JPH09101188A - Flat oscillating type level sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the leak of the oscillation of an oscillating diaphragm used to detect a charged material in contact therewith along a housing vessel, regardless of flat oscillating type having no projected oscillation rod. SOLUTION: A pair of oscillating diaphragms 7 and 8 are held in a holding tube 4, so as to face each other along the axial direction of the holding tube 4. The end of the holding tube 4 is positioned in such a state as protruding in the housing vessel 22 of a charged material 23. Furthermore, an exciter 10 is mounted at least on one of a pair of the oscillating diaphragms 7 and 8. In this case, a pair of the oscillating diaphragms 7 and 8 are respectively set to have the same natural frequency, and caused to oscillate at the same frequency and with an opposite phase under resonance, thereby offsetting the oscillations of both diaphragms 7 and 8 via the holding tube 4 and preventing the oscillation from propagating to the housing vessel 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to filling a container such as a tank with an object to be filled such as a liquid, powder or granular material, and checking whether the object has been filled to a predetermined height level. The present invention relates to a flat vibration type level sensor for detecting whether or not it is.

[0002]

2. Description of the Related Art Conventionally, as a level sensor generally used for this type of application, Japanese Patent Laid-Open No. 62-29312 has been proposed.
A device described as a filling surface adjusting device in Japanese Patent Laid-Open No. 7 is known, and this device is attached to a container for the object to be filled and has the following configuration. That is,
The vibrating rod in which a piezoelectric element is attached to one end of a strip-shaped metal vibrating piece is supported by a support made of a metal thin film at two places where the nodes of the vibration of the primary vibration mode appear, and the vibration is generated. The transmission to the storage container is suppressed as much as possible. Both of these supports are attached by welding to the openings at both ends of a cylindrical holding tube that covers both nodes of the vibrating rod, and the other end of the vibrating rod projecting from the holding tube is used as a measuring probe of the filling object. There is.

In the above-mentioned device, when the filling surface of the filling object which rises with the filling operation of the storage container such as the tank comes into contact with the measuring probe portion on the other end side of the vibrating rod, the vibration rod vibrates. Since the output voltage from the piezoelectric element changes due to the suppression or the stop, the size of this output voltage determines whether or not the object to be filled is filled to a predetermined height level.

[0004]

However, in the above apparatus, when the object to be filled has a large apparent specific gravity,
The measurement probe portion is easily bent by being pressed by the filling object. When the measuring probe portion bends, there arises inconveniences such as erroneously detecting the height level of the filling object and preventing the vibrating rod from vibrating normally.

In order to solve the above problem, there is a flat type in which the vibrating rod does not protrude from the holding tube. In this flat type, a vibrating membrane for detecting an object to be filled instead of the vibrating rod is attached to the vibrating membrane in a closed state at a tip opening portion of the holding tube that is inserted into the container for the object to be filled. A piezoelectric element is attached. When the object to be filled comes into contact with the vibrating film that vibrates by driving the piezoelectric element, the vibration of the vibrating film is suppressed or stopped, and the output voltage from the piezoelectric element changes. It can be determined whether or not is filled up to a predetermined height level.

However, with the above-mentioned structure, the vibration of the vibrating film is transmitted to the storage container through the holding tube and leaks, so that the vibration of the vibrating film is attenuated by the storage container, which is generally a heavy object, and the filled object is filled. The detection sensitivity of the object is significantly reduced. Therefore, in order to obtain vibration of a predetermined amplitude, the power supplied to the piezoelectric element must be increased,
Power consumption increases. Further, the amount of attenuation of the vibration of the vibrating membrane by the storage container changes according to the variation in the mounting strength of the level sensor to the storage container. Therefore, it is necessary to adjust the vibration intensity of the vibrating membrane to obtain a required amplitude after the completion of attachment to the storage container, for example, which is not practically possible.

Therefore, the present invention is a flat type vibration type in which the vibrating rod does not project, but the vibration of the vibrating membrane for contacting and detecting the object to be filled is not transmitted to the storage container and leaks. The purpose is to provide a formula level sensor.

[0008]

In order to achieve the above-mentioned object, a flat vibrating level sensor of the present invention comprises a holding tube having a tip advanced into a container for the object to be filled, and a holding tube. A pair of vibrating membranes that are held by the holding tube and face each other in the axial direction of the holding tube, and a vibrator that applies vibration to at least one of the pair of vibrating membranes are provided. The frequencies are set to be the same.

The flat type vibration type level sensor is installed in a state where a holding tube is inserted into a storage container such as a tank filled with liquid or powder, and a vibrator is driven to generate a pair of vibrations. When vibration is applied to at least one of the membranes, this vibration excites the other vibrating membrane through the holding tube. When the filling object inside the container is filled to the height level where it contacts the vibrating membrane near the tip of the holding tube, the vibration of the vibrating membrane is suppressed by the filling object, so the electric signal of the exciter changes. Then, it is detected that the filling object is filled to a predetermined height level by the change of the electric signal.

Here, since the natural frequencies of both vibrating membranes are set to be the same, the other vibrating membrane resonates with the vibration of one vibrating membrane, and the amplitude and the vibration frequency of the one vibrating membrane are increased. Vibrations that are the same and have different phases are generated.
Therefore, the vibrations of both vibrating membranes cancel each other out and are not transmitted to the storage container, so the vibrations of the vibrating membrane are not attenuated by the storage container and are not affected by the variations in the mounting strength to the storage container. Therefore, it always has an amplitude corresponding to the vibration energy received from the vibrator. Further, since it is a flat type without a vibrating rod that is easily bent by the object to be filled, it has a high reliability that it can be stably operated for a long period of time.

In one embodiment of the present invention, a weight is attached to the vibrating membrane. The weight reduces the natural vibration frequency of the vibrating membrane and shortens the vibration length, so that the level sensor can be downsized.

The vibrator is composed of a piezoelectric element, and the piezoelectric element is fixed to one of the pair of the vibrating membranes near one end of the holding tube, and the lead wire of the piezoelectric element is the other. It is preferable that the vibrating membrane penetrates through the vibration nodal line and is drawn out to the rear portion of the holding tube.

According to the above construction, the one vibrating membrane located near the tip of the holding tube is arranged so as to advance into the storage container, and the object to be filled is detected by the contact thereof. By directly exciting one of the vibrating membranes by the piezoelectric element, this vibrating membrane is vibrated reliably and the reliability of detection of the filling object is improved. Further, if the lead wire of the piezoelectric element is pulled out backward through the nodal line where the node of the vibration of the other vibrating film at the rear position appears, this lead wire penetrates the nodal line which is the fixed point, There is no adverse effect on the vibration of the other vibrating membrane.

[0014]

Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a vertical sectional view showing a flat vibration type level sensor according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line II-II of FIG. In these drawings, the body case 2 and the mounting socket 3 are connected to the tip of the casing 1 by a means described later,
The cylindrical holding tubes 4 are connected by fixing means such as welding. First and second circular thin film-shaped vibrating membranes 7 and 8 are fixed to both ends of the holding tube 4 by welding while hermetically closing the opening of the holding tube 4. Both vibrating membranes 7 and 8 are made of the same material and have the same shape and the same size.

FIG. 3A is a view seen from the direction of arrow A in FIG. The inner surface of the first vibrating membrane 7 located near the tip of the holding tube 4 (on the left side in FIG. 1) has a structure shown in FIGS.
As shown in FIG. 1, a pair of piezoelectric elements (vibrators) 9 and 10 are arranged and attached on the same horizontal plane, and these piezoelectric elements 9 and 10 are connected to the lead wires from the drive circuit section 11 of FIG. Power is supplied via 12. As shown in FIGS. 1 and 3 (a), a weight 13 having the same disk shape and the same weight is provided at the central portions of the surfaces of the vibrating membranes 7 and 8 which face each other.
Mounting screws 14 screwed into the respective central portions are welded and attached.

As shown in FIG. 4, the drive circuit section 11 converts the AC power of the commercial AC power supply 17 into DC power by the rectifier circuit 18 and supplies the DC power to one piezoelectric element 9. The piezoelectric element 9 converts the supplied electric energy into mechanical energy and applies vibration to the first vibrating film 7. Mechanical energy due to the vibration of the vibrating film 7 is converted into electric energy by the other piezoelectric element 10. Only the vibration component of the output voltage of the piezoelectric element 10 is extracted by the bandpass filter 19 of the drive circuit unit 11, and the output signal of the bandpass filter 19 is amplified by the amplifier circuit 20.
After being amplified by, it is superimposed on the DC power of the rectifier circuit 18 and input to the relay output circuit 21. The relay output circuit 21 turns on an indicator lamp (not shown) when a predetermined electric signal is input, and supplies the filling object 24 into the storage container 22 such as the tank of FIG. 1 ( A supply stop signal is output to (not shown) to stop the supply operation of the filling target 24.

The lead wire 12 for connecting the drive circuit portion 11 and the piezoelectric elements 9 and 10 passes through the insertion hole 24 of the second vibrating membrane 8 and the through hole 27 of the mounting socket portion 3 of FIG. It is pulled back. Further, the lead wire 12
Is a support cylinder body 3 in which a fixing elastic body 28 such as rubber having the lead wire 12 inserted therethrough is fixed to a support plate 29.
It is press-fitted into 0 and is held by the elastic body 28 that is deformed into a crushed state, and is supported by the support plate 29 through the support cylinder body 30. Further, the front end of the main body case 2 is fitted to the step portion of the rear end of the mounting socket 3 with the gasket 31 interposed, and the main body case 2 is contacted with the main body case 2 via the seal material 32. By fixing the peeled support plate 29 to the mounting socket portion 3 with the fixing screw 33, the main body case portion 2 and the mounting socket portion 3 are hermetically connected. The rear end opening of the main body case 2 has the packing 34 shown in FIG.
It is blocked by 7.

The flat vibration type level sensor having the above-mentioned structure is mounted at a predetermined height position on the side wall of the storage container 22 shown in FIG. That is, a mounting hole 38 is formed in the side wall of the storage container 22 at a position corresponding to the height position where the filling object 23 is to be filled, and a socket 39 having a female screw portion is fitted into the mounting hole 38. It is fixed by welding. In the flat vibration type level sensor, the taper screw portion 40 formed on the mounting socket portion 3 of the casing 1 is screwed into the female screw portion of the socket 39, and the outward bulging portion 41 of the mounting socket portion 3 is fixed to the gasket 31.
The holding tube 4 is airtightly attached to the storage container 22 in a state where the holding pipe 4 is advanced into the storage container 22 by pressing the holding pipe 4 into the storage container 22 by interposing the holding tube 4 therebetween. Since this level sensor is a flat type that does not have a vibrating rod protruding into the storage container 22 unlike the conventional sensor, the problem that the vibrating rod bends does not occur.

Next, the operation of the level sensor will be briefly described. The first vibrating membrane 7 near the tip of the holding tube 4.
The piezoelectric element 9 attached to the drive circuit unit 11 of FIG.
DC power is supplied from the rectifier circuit 18 of the first vibrating film 7 and vibrates due to noise components included in the DC power.
Add vibration to. When the filling surface H of the filling object 23 in the storage container 22 is below the first vibrating membrane 7 as shown in FIG. 1, the vibration component contained in the other piezoelectric element 10 is in the band of FIG. The amplification circuit 20 is extracted by the filter 19.
After being amplified by, it is superimposed on the DC power of the rectifier circuit 18 and input to the relay output circuit 21. When the filling surface H of the filling object 23 rises to a height position where the filling surface H contacts the first vibrating film 7, the filling object 23 suppresses or stops the vibration of the first vibrating film 7 and the output voltage of the piezoelectric element 10. No longer contains vibration components. Therefore, the relay output circuit 21
Since only the DC power from the rectifier circuit 18 is input, the indicator lamp is turned on to notify the completion of filling, and
The supply stop signal is output to the feeder for the filling object 23.

By the way, in the above-mentioned flat vibration type level sensor, since the first vibrating membrane 7 is fixed to the holding tube 4 at the peripheral portion thereof, it is schematically shown by a two-dot chain line in FIG. 3 (b). As shown, the first vibrating membrane 7 is excited in the secondary vibration mode. The vibration of the first vibrating film 7 is transmitted to the second vibrating film 8 through the holding tube 4, and the second vibrating film 8 is also fixed to the holding tube 4 at the peripheral portion thereof.
As shown in (b), it is excited in the secondary vibration mode similarly to the first vibrating film 7. The vibrating membranes 7 and 8 are made of the same material and have the same shape and the same size, and the weights 13 and 13 attached to the vibrating membranes 7 and 8 have the same weight. That is, since the natural frequencies of both vibrating membranes 7 and 8 are set to be the same, the second vibrating membrane 8 is
As is clear from the longitudinal cross-sectional view of the operating state shown in Fig. 3, the first vibrating membrane 7 resonates with the same vibration frequency with respect to the first vibrating membrane 7 and in the opposite phase (phase shifted by 180 °). Vibrate.

Therefore, as shown in FIG. 5, the holding tube 4 has the same tensile forces B1 and B2 for pulling one side (upper side of the figure) of the both ends in opposite directions, and the other of the both ends. The same compression forces C1 and C2 that try to compress the sides (the lower side in the figure) in opposite directions are alternately generated in the upper and lower portions of the figure. Since the tensile forces B1 and B2 and the compressive forces C1 and C2 cancel each other out, the vibrations of the vibrating membranes 7 and 8 disappear in the wall of the holding tube 4, and
Is not transmitted to the mounting socket 3 of. That is, the vibration of the first vibrating film 7 to which the vibration is added by the piezoelectric element 9 does not leak to the storage container 22 via the mounting socket portion 3,
It is not damped by the storage container 22, which is a heavy object. As a result, the first vibrating film 7 is supplied with a constant vibration energy from the piezoelectric element 9, whereby the filling object 23
Oscillates with a predetermined amplitude sufficient to reliably detect. Moreover, the amplitude of the vibration of the first vibrating film 7 is always a constant value determined by the piezoelectric element 9 and the electric power supplied thereto, regardless of the variation in the mounting strength of the mounting socket portion 3 to the storage container 22. Becomes

In the above embodiment, both vibrating membranes 7,
Weights 13 of the same weight are attached to each of the eight. The weight 13 lowers the natural vibration frequency of the vibrating membranes 7 and 8 and shortens the vibration length thereof, so that the shape of the vibrating membranes 7 and 8 can be reduced and the level sensor can be downsized.

Further, in the above-described embodiment, the insertion hole 24 provided in the second vibrating membrane 8 for pulling out the lead wire 12 of the piezoelectric elements 9 and 10 rearward is shown in FIGS. 3 (a) and 3 (b). As shown by the dashed line, the second vibration mode
Is arranged on the nodal line 42 of the vibrating membrane 8. This nodal line 4
Since each point on 2 is immovable, the second vibrating membrane 8 vibrates without being affected by the penetration of the lead wire 12 into the insertion hole 24.

In the above embodiment, the filling object 23
The pair of piezoelectric elements 9 and 10 are directly attached to the first vibrating membrane 7 with which the filling object 23 comes into contact in order to obtain a reliable vibration against the pressure of the piezoelectric element 9 and the second piezoelectric element 10. Attached to the vibrating film 8 or a pair of piezoelectric elements 9 and 10
One of them is attached to one of the vibrating membranes 7 and 8, and the other of the piezoelectric elements 9 and 10 is attached to the other of the vibrating membranes 7 and 8, or a pair of piezoelectric elements 9 and 10 is attached to each of the vibrating membranes 7 and 8. Even if the structure is provided with two pairs of piezoelectric elements 9 and 10 in total, the same effect as described above can be obtained.

[0025]

As described above, according to the present invention, since the object to be filled is detected by contacting it with the vibrating membrane, the problem of the conventional sensor having the vibrating rod as the detecting portion can be solved. Also,
Since a pair of vibrating membranes held in the holding tube so as to face each other in the axial direction are set to the same natural frequency, both vibrating membranes resonate and vibrate at the same frequency and in opposite phases. , The respective vibrations cancel each other out in the holding tube. Therefore, the vibration of the vibrating membrane is not transmitted to the storage container and leaks, so that the vibration is not attenuated by the storage container and is not affected by the variation in the attachment strength to the storage container. Therefore, the object to be filled can be detected with high accuracy by vibrating the vibrating membrane at a predetermined amplitude at all times.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view showing a flat vibration type level sensor according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

3 (a) is a view seen from the direction of arrow A in FIG.
(B) is a schematic diagram showing a vibration mode of the vibrating film in correspondence with (a).

FIG. 4 is a block configuration diagram of a drive circuit unit in the same sensor.

FIG. 5 is a simplified vertical cross-sectional view of a main part showing an operating state of the same sensor.

[Explanation of Codes] 4 ... Holding tube, 7, 8 ... Vibration film, 9, 10 ... Piezoelectric element (vibrator), 12 ... Lead wire, 13 ... Weight, 22 ... Storage container, 23 ... Filled object, 42 … Node lines.

Claims (3)

[Claims] 1. A holding tube having a front end that is arranged to advance into a storage container for the object to be filled, a pair of vibrating membranes held by the holding tube and facing each other in the axial direction of the holding tube, and a pair of the vibrating membranes. A flat vibratory level sensor, comprising: a vibrator for applying vibration to at least one of the vibrating membranes, wherein the pair of vibrating membranes have the same natural frequency. 2. The flat vibration type level sensor according to claim 1, wherein a weight is attached to the vibration film. 3. The piezoelectric vibrator according to claim 1, wherein the vibrator comprises a piezoelectric element, and the piezoelectric element is fixed to one of a pair of the vibrating membranes near one end of the holding tube. A flat vibration type level sensor in which a lead wire of an element penetrates a nodal line of vibration of the other vibrating membrane and is drawn out to a rear portion of the holding tube.