JPS61130821A - Fluid body level sensor - Google Patents

Abstract

PURPOSE:To achieve a highly sensitive level detection, by providing a flexible member retaining a clearance between it and a piezo-electric vibrator to give a pressure change in a fluid body in the vicinity of the vibration node thereof effectively through the flexible member and a pressure transmitting member. CONSTITUTION:A piezo-electric vibrator 2 is mounted on a step 4 of a mounting case 1 through a buffer support 3. Moreover, the pressure of a fluid body is received through a flexible member 5 with a required clearance 7 formed between it and the vibrator 2 and given as concentrated load in the vicinity of the vibration node 2A of the vibrator 2 set optimally with a plate body 8 and a pressure transmitting member 9. Therefore, any fluid body that may generate a friction resistance in noway affects the vibrator 2 adversely in the friction loss or the like and the resonance frequency of the vibrator 2 will not be varied with the type of the fluid body. The vibrator 2 is supported with the buffer support 3 in such a structure as to attain free vibration progressively thereby enabling a highly sensitive level detection.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Meter" The present invention relates to a level meter configured to detect the level of a fluid such as powder or granular material or fluid via a piezoelectric vibrator. In addition to eliminating the negative effects caused by friction loss between the fluid and the piezoelectric vibrator or changes in the resonant frequency of the piezoelectric vibrator, we also improved the support structure of the piezoelectric vibrator to enable better detection operation. Related to body level sensor.

"Prior art" As a means of detecting the pressure of gas, etc., a piezoelectric vibrator that can convert external pressure changes into electrical output changes is used, and the pressure is applied to the surface of the vibrator to detect gas pressure changes. For example, a pressure sensor with a structure that detects frequency changes is
Currently, it is widely used in various fields. This type of conventional pressure sensor is generally configured so that the pressure receiving surface is essentially the vibrator itself, and the corresponding portion of the pressure receiving surface of such a vibrator is formed as smooth as possible. As a result, the piezoelectric vibrator is configured to maximize the ability to sense pressure changes while eliminating as much as possible friction loss that may occur between the pressure receiving surface and the object to be detected. Such pressure sensors are used not only as atmospheric pressure detectors but also as various sound pressure level meters.

"Problems to be Solved by the Invention" By the way, when the above-mentioned conventional pressure detection sensor is used as a sensor for detecting pressure changes or level changes of fluids other than gases, such as various powders or liquids, Since frictional resistance with the fluid occurs on the pressure-receiving surface of the piezoelectric vibrator, this friction loss and the resulting change in the resonant frequency of the piezoelectric vibrator cause the quality of the vibrator to deteriorate.
There is a risk that the performance of the actor will be drastically reduced. Therefore, if the fluid level detection operation is performed under such conditions,
The oscillation operation of the piezoelectric vibrator becomes impossible to continue, and only the start and stop operations of oscillation are detected, and it is no longer possible to detect continuous pressure changes or level changes in the fluid. In addition, piezoelectric vibrators are conventionally
Although it is supported by being fused or adhered to a cushioning material such as rubber, such support means may inhibit the free vibration of the piezoelectric vibrator and cause sensitivity instability or decrease in sensitivity. there were.

``Means for Solving the Problems'' The present invention is capable of reliably detecting a change in the level of a detected object made of a fluid with frictional resistance such as powder or liquid as described above. It is an object of the present invention to provide a fluid level sensor having a suitable support structure for a piezoelectric vibrator. In a level sensor that detects the level of a fluid by using a pressure change as an output change of the piezoelectric vibrator, a flexible member is slightly disposed to form a gap between the piezoelectric vibrator and the fluid. , the flexible member is configured to include a pressure transmission member for applying a pressure change of the fluid to the vicinity of a vibration node of the vibrator, and is configured to freely support the piezoelectric vibrator with a cushioning material. It is characterized by having been devised.

According to the fluid level sensor having such a structure, the pressure caused by the fluid is transferred to the flexible member while receiving the fluid with the flexible member without directly contacting the fluid with the pressure receiving surface of the piezoelectric vibrator. It is possible to apply a concentrated load to the vicinity of the vibration nodes of the piezoelectric vibrator through the pressure transmission member installed in the member, and this structure allows stable and highly accurate detection without being adversely affected by the type of object to be sensed. It becomes possible to achieve fluid level detection operations. The flexible member can be made of a corrosion-resistant metal foil of an appropriate thickness, a corrosion-resistant metal foil, a plastic film of an appropriate thickness, etc., and may be made of such a member. The pressure transmission member serves as a means for intensively transmitting the fluid pressure applied by the flexible member to the vicinity of the vibration node of the piezoelectric vibrator.
It is made of a rubber material with appropriate rigidity and elasticity, and its tip can be placed in contact with the piezoelectric vibrator.
Furthermore, since the piezoelectric vibrator is supported in a freely supported state, such as by placing its outer end on a cushioning material such as rubber, it is possible to ensure optimal detection operation of the piezoelectric vibrator.

"Embodiment" FIG. 1 shows a conceptual cross-sectional configuration diagram of essential parts of a fluid level sensor constructed according to an embodiment of the present invention.
Reference numeral 1 denotes a cylindrical assembly case in a fluid level sensor, and a disc-shaped piezoelectric vibrator 2 is mounted on a stepped portion 4 provided at the upper end of the case via a suitable buffer support material 3. has been done.

Reference numeral 5 denotes a flexible member, and the flexible member 5 has a mounting portion 6 on its outer periphery attached to the upper end of the nurse 1 so as to form a required gap 7 between the flexible member 5 and the piezoelectric vibrator 2. 8 is a flexible member 5
A plate body for converting concentrated load is attached to the back surface of the central part of the piezoelectric vibrator 2, and the plate body 8 and the vibrator 2 are in contact with each other in a manner that matches the positions of the two vibration nodes existing near the outer periphery of the piezoelectric vibrator 2. For example, the pressure transmitting member 9 is configured to have an annularly protruding pressure transmitting member 9 such as an O-ring. As the flexible member 5, for example, a corrosion-resistant metal foil such as nickel or stainless steel with an appropriate thickness, or other corrosion-resistant metal foil may be used. Note that the pressure transmission member 9 is desirably made of a rubber material or the like so as to have appropriate rigidity and elasticity so as to prevent the piezoelectric vibrator 2 from causing undesirable chatter motion. Further, it is preferable that the lower surface of the pressure transmitting member 9 be placed in contact with a portion of the piezoelectric vibrator 2 that corresponds to the vibration wIz of the person.

According to the fluid level sensor having such a structure, the pressure transmitting member 9, the plate body 8, and the flexible member 5 are first placed on the upper surface of the piezoelectric vibrator 2 on the buffer support member 3 of the case 1. The pressure transmitting member 9 can be attached to the outer peripheral mounting portion 6 of the flexible member 5 to the upper end of the case 1, or by attaching it via a suitable buffering structure such as a buffering material or pears means.
The piezoelectric vibrator 2 can be easily assembled while ensuring uniform contact between the piezoelectric vibrator 2 and the piezoelectric vibrator 2.
@'I is maintained in an airtight state during the formation between the flexible member 5 and the flexible member 5.

In order to maintain the original free vibration of the piezoelectric vibrator 2, the first
In the illustrated embodiment, a substantially U-shaped buffer support member 3 made of a rubber material for positioning the vibrator is attached to the stepped portion 4 of the case 1, and the inner protrusion of the support member 3 A support structure is adopted in which the outer end of the piezoelectric vibrator 2 is placed on top of the piezoelectric vibrator 2 so as to be in contact with the outer end thereof. With such a buffer support structure, the piezoelectric vibrator 2 is maintained in a free oscillating state without the risk of being subjected to undesirable restraint, thereby ensuring linear level output characteristics even when the load of the fluid is low. Become. The buffer support material 3 as described above may be a protruding or semicylindrical buffer support material 11 shown in FIG. 2, or a ring-shaped material 12 such as 1jlI31ff may also be used.

According to the fluid level sensor having the above structure, the piezoelectric vibrator 2
A fluid such as powder or liquid whose level is to be detected receives the pressure of the fluid through a flexible member 5 that forms a required distance with the vibrator 2 without contacting the transducer 2. This fluid pressure is applied to the plate body 8 and the pressure transmission member 9, and the vibration of the piezoelectric vibrator 2 which is optimally set as a concentrated load @2
Since the configuration is such that the pressure is applied near A, even if the fluid generates frictional resistance, the pressure 11! There is no possibility of any adverse effect on the vibrator 2, and therefore, the wave number of the resonance layer of the piezoelectric vibrator 2 is not varied depending on the type of fluid and is stable.

A reliable fluid level detection operation can be achieved.

Furthermore, since the piezoelectric vibrator 2 is supported by the buffer support material 3, 11, 12 in a structure that allows its free vibration to be achieved as much as possible, a highly sensitive level detection operation can be performed.

In the above embodiment, the weight of the flexible member plate 8 and pressure transmission member 9 is compensated for by attaching the flexible member 5 to the case 1 while maintaining an appropriate tensile state in the outer circumferential direction. The present invention also includes providing ventilation holes in the case 1 as appropriate so that the space 7 formed between the piezoelectric vibrator 2 and the flexible member 5 communicates with the outside of the case 1. This is a matter that should be understood as falling within the range intended by Providing various means for reducing contact resistance at the tip, and using such means at the same time without making the entire tip of the pressure transmitting member uniformly contact the piezoelectric vibrator side. An embodiment in which only the actual pressure inherent in the fluid is effectively applied to the piezoelectric vibrator 2 side by a method of making contact at several points is also included within the scope of the fluid level sensor according to the present invention. It can be implemented as desired. Similarly, as for the structure of the flexible member 5, instead of configuring the entire part from a flexible material, a part thereof may be configured to have flexibility, and the surface of the flexible member may be It is also possible to apply other members capable of reducing the frictional resistance with the fluid as much as possible, or to perform a coating treatment with a suitable material.

"Effects of the Invention" The fluid level sensor according to the present invention includes a flexible member capable of maintaining a gap between the piezoelectric vibrator and the fluid level sensor, and the pressure of the fluid is transmitted through the flexible member and the pressure transmitting member. It is configured to effectively apply changes to the vicinity of the vibration nodes of the piezoelectric vibrator, and can also handle level changes in various fluids with frictional resistance, such as powder or liquid, which was previously impossible. Can be suitably detected. In addition, it is equipped with a buffer support structure that can maintain the inherent free vibration motion of the piezoelectric vibrator, enabling highly sensitive level detection, and the structure of this fluid level sensor is made up of a minimum number of parts. It has the advantage that it is easy to assemble and set, and can be easily applied as a level detection means for this type of fluid, and the level detection operation is stable and highly accurate over a wide range.

Brief explanation of tvA plane FIG. 1 shows a conceptual cross-sectional view of essential parts of a fluid level sensor constructed according to an embodiment of the present invention, and FIG. FIG. 3 is a cross-sectional configuration diagram of main parts showing another structure, and FIG. 3 is a cross-sectional configuration diagram of main parts showing still another buffer support structure.

1: Mounting case 2; Piezoelectric vibrator 2 people: Vibration node 3: Buffer support material 4: Case step, section 5: Flexible member) 6: Mounting section 7: Gap 8:
Concentrated load conversion plate 9: Pressure transmission member

Claims (1)

[Claims] In a level sensor that detects the level of a fluid based on a pressure change applied to a piezoelectric vibrator as a change in the output of the piezoelectric vibrator, a gap is provided between the piezoelectric vibrator and the fluid. The flexible member has a pressure transmitting member for applying a pressure change of the fluid to the vicinity of a vibration node of the vibrator, and the piezoelectric vibrator is covered with a cushioning material. A fluid level sensor configured to be freely supported.