A vibration liquid level switch sensor

Abstract

The present invention provides a vibration liquid level switch sensor, which relates to the technical field of liquid level switches and includes a bottomed cylindrical housing, a piezoelectric unit, a matching layer and an adhesive layer; the piezoelectric unit and the matching layer are sequentially arranged in the bottomed cylindrical housing from top to bottom; the piezoelectric unit and the matching layer are bonded through the adhesive layer; the matching layer and the inner bottom surface of the bottomed cylindrical housing are bonded through the adhesive layer; the matching layer is used to insulate the bottomed cylindrical housing and the piezoelectric unit; the central thickness of the bottom surface of the bottomed cylindrical housing is smaller than the edge thickness; an oscillating fork body is arranged at the outer bottom surface of the bottomed cylindrical housing; the piezoelectric unit is used to drive the oscillating fork body to vibrate and receive the signal of the oscillating fork body after vibration in different media; the oscillating fork body is a long strip-shaped metal with a thick middle and thin ends. The present invention adjusts the thickness of the bottom surface of the bottomed cylindrical housing to improve the stability of the vibration liquid level switch sensor, and has the advantages of simple structure and low manufacturing cost.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid level switches, and particularly to a vibrating liquid level switch sensor. Background Art

[0002] The working principle of a vibrating liquid level switch sensor is to judge whether there is liquid by the change of the frequency of the sensor in air and various test media, and then start or stop through a switch command to prevent overflow or dry running. Among them, the working frequency, as a key parameter, plays a crucial role in the reliable and stable operation of the vibrating liquid level switch sensor during long-term operation or within a certain temperature range.

[0003] In the prior art, the piezoelectric driving device preferably adopts a crimping method, that is, the piezoelectric transmitting unit and the receiving unit of the multi-layer structure are pressed on the diaphragm through a tightening bolt. This structure, although not affected by the adhesive layer generated by the adhesive method, also has obvious disadvantages: 1) It needs to be realized by a multi-layer piezoelectric transmitting unit and receiving unit, and the number of required parts is very large. In actual application, if one part fails and the frequency and amplitude of the sensor change abnormally, the entire product will fail; 2) Affected by the crimping structure, the fixing structure of the piezoelectric driving device will occupy more space, the oscillating fork body is very large, which limits the installation space of the switch product, and the vibration frequency is low, and the frequency change difference in air and medium is small, which is easy to cause false alarms; 3) The manufacturing process is complex and the manufacturing cost is high.

[0004] As another implementation method, a vibrating liquid level switch includes a piezoelectric transmitting unit and a receiving unit, a diaphragm, and an oscillating fork body combined with the diaphragm. Among them, the piezoelectric transmitting unit and the receiving unit are directly bonded to the diaphragm or by using an adhesive process, so that the oscillating fork body vibrates. This adhesive layer generally uses organic epoxy resin, and structurally, the diaphragm has a continuous and uniform thickness, and the surfaces between the diaphragm and the adhesive layer are relatively horizontal, resulting in a constant thickness of the adhesive layer over the entire area. Affected by long-term vibration or temperature, the disadvantages of such a design are: 1) Affected by temperature, the continuous and uniform thickness of the diaphragm will generate shear stress around the piezoelectric unit, resulting in small cracks and failure, and then the frequency and amplitude of the product will suddenly fail and cause abnormal alarms; 2) Using epoxy resin glue, there are problems such as aging, low glass transition temperature, insufficient rigidity, or excessive rigidity, and a decrease in hardness at high temperatures. Small cracks are likely to occur in the adhesive layer. Once the temperature exceeds 100 degrees, the state changes from a glassy state to a highly elastic state, which will absorb the transmitted vibration energy and have an irreversible impact on the frequency and amplitude of the oscillating liquid level switch; 3) Structurally, the adhesive layer has a uniform thickness, and shear force is caused by thermal stress, resulting in cracks inside, thus affecting the frequency and amplitude of the oscillating liquid level switch and unable to work properly.

[0005] In the prior art, there are two ways to improve the above problems. First, in a piezoelectric drive device, each piezoelectric unit is first subjected to surface pre-metallization treatment, and then fixed together by diffusion welding. Although this is not affected by the aging of the organic adhesive layer and temperature, this method has very high quality requirements for the surface treatment of the piezoelectric units bonded to each other. In addition, this process strictly requires that the temperature of diffusion welding cannot exceed the Curie temperature of the piezoelectric unit, otherwise the piezoelectric unit will depolarize due to excessive temperature and lose its piezoelectric properties. Therefore, this places particularly high requirements on the temperature performance of the piezoelectric unit, and the selection of the manufacturing materials and processes of the piezoelectric unit will be much more complex, and the cost will also be very high. In addition, the manufacturing process of diffusion welding is very complex and the cost is also very high. Second, in a piezoelectric drive device, a nano-silver sintering technology with a single particle size is used to achieve the connection between each unit. Although this technology can achieve low-temperature sintering and achieve sintering and curing at as low as 280 °C to achieve connection. However, since nano-silver is not 100% pure nano-silver during the manufacturing process and contains about 10% organic matter, during sintering, due to the volatilization of the organic matter, many interconnected microscopic pores will be left in the adhesive layer. These existing pores will affect the transmission of the vibration energy of the piezoelectric unit, and thus its operating frequency reliability is poor, and it is prone to false alarms, especially within a certain temperature range.

[0006] In summary, the manufacturing process and technology of the existing vibration type liquid level sensor are complex, the manufacturing cost is high, the frequency and amplitude are greatly affected by temperature within a certain wide temperature range, the repeatability is poor, and the reliability is low. Summary of the Invention

[0007] The object of the present invention is to provide a vibration liquid level switch sensor, which improves the stability of the vibration liquid level switch sensor by setting the bottom thickness of the bottomed cylindrical housing, and has the advantages of simple structure and low manufacturing cost.

[0008] To achieve the above object, the present invention provides the following solution:

[0009] A vibration liquid level switch sensor, comprising:

[0010] A bottomed cylindrical housing, a piezoelectric unit, a matching layer and an adhesive layer;

[0011] The piezoelectric unit and the matching layer are sequentially arranged in the bottomed cylindrical housing from top to bottom;

[0012] The piezoelectric unit and the matching layer are bonded by an adhesive layer;

[0013] The matching layer and the inner bottom surface of the bottomed cylindrical housing are bonded by an adhesive layer; the matching layer is used to insulate the bottomed cylindrical housing and the piezoelectric unit; the central thickness of the bottom surface of the bottomed cylindrical housing is less than the edge thickness;

[0014] An oscillating fork body is provided at the outer bottom surface of the bottomed cylindrical housing; the piezoelectric unit is used to drive the oscillating fork body to vibrate and receive the signal after the oscillating fork body vibrates in different media; the oscillating fork body is a long strip-shaped metal that is thick in the middle and thin at both ends.

[0015] Optionally, the bottomed cylindrical housing is a stepped bottomed cylindrical structure; the inner diameter of the upper part of the bottomed cylindrical housing is greater than the inner diameter of the bottom of the bottomed cylindrical housing;

[0016] Both the piezoelectric unit and the matching layer are disc-shaped structures;

[0017] The diameter of the piezoelectric unit is smaller than the diameter of the matching layer;

[0018] The diameter of the matching layer is smaller than the inner diameter of the bottom of the bottomed cylindrical housing.

[0019] Optionally, the vibrating liquid level switch sensor further includes:

[0020] A surrounding structure, an adapter plate, and a plurality of support columns;

[0021] The surrounding structure is a stepped cylindrical structure; the outer diameter of the surrounding structure is greater than the inner diameter of the bottom of the stepped bottomed cylindrical housing; the outer diameter of the surrounding structure is smaller than the inner diameter of the upper part of the stepped bottomed cylindrical housing; the surrounding structure is arranged at the step inside the bottomed cylindrical housing; the inner diameter of the upper part of the surrounding structure is greater than the inner diameter of the bottom of the surrounding structure;

[0022] The diameter of the adapter plate is greater than the inner diameter of the bottom of the surrounding structure; the diameter of the adapter plate is smaller than the inner diameter of the upper part of the surrounding structure; the adapter plate is arranged at the step inside the surrounding structure; the adapter plate is connected to the piezoelectric unit through a connecting wire; the adapter plate is used to transfer the signal received by the piezoelectric unit;

[0023] A plurality of the support columns are arranged at intervals on the lower bottom surface of the surrounding structure; the lower bottom surfaces of the plurality of support columns are in contact with the matching layer.

[0024] Optionally, the matching layer is alumina ceramic;

[0025] The thickness of the matching layer is 0.4 mm - 0.6 mm.

[0026] Optionally, the thickness of the middle part of the bottom surface of the bottomed cylindrical housing is 1.6 mm to 1.8 mm;

[0027] The thickness of the edge of the bottom surface of the bottomed cylindrical housing is 2 mm.

[0028] Optionally, a plurality of annular grooves are provided on the inner bottom surface of the bottomed cylindrical housing;

[0029] The annular groove is used to enhance the bonding strength between the matching layer and the inner bottom surface of the cylindrical shell with a bottom.

[0030] Optionally, the piezoelectric unit includes:

[0031] A piezoelectric transmitting part and a piezoelectric receiving part;

[0032] The piezoelectric receiving part is circular; the piezoelectric transmitting part is annular; the piezoelectric transmitting part and the piezoelectric receiving part are concentrically arranged;

[0033] The piezoelectric transmitting part and the piezoelectric receiving part share a negative electrode.

[0034] Optionally, the piezoelectric unit includes:

[0035] A piezoelectric receiving part and two piezoelectric transmitting parts;

[0036] The piezoelectric receiving part is circular; the piezoelectric transmitting part is semi-annular; the two piezoelectric transmitting parts are arranged to surround the piezoelectric receiving part; the piezoelectric transmitting part and the piezoelectric receiving part are separated by a spacer groove; the piezoelectric transmitting part and the piezoelectric receiving part share a negative electrode.

[0037] Optionally, the piezoelectric unit includes:

[0038] A piezoelectric transmitting part, a piezoelectric receiving part and a shared negative electrode;

[0039] The piezoelectric transmitting part, the shared negative electrode and the piezoelectric transmitting part are arranged at intervals.

[0040] Optionally, the bonding layer is a two-component organic epoxy resin doped with nano-aluminum oxide powder; the edge thickness of the bonding layer is greater than the middle thickness of the bonding layer.

[0041] Optionally, the bonding layer is a silver-tin sintered material; the silver-tin sintered material is formed by mixing paste-like nano-silver and paste-like nano-tin materials and then coating and sintering them on a steel mesh coated with nano-copper.

[0042] According to the specific embodiments provided by the present invention, the following technical effects of the present invention are disclosed:

[0043] A vibration liquid level switch sensor provided by the present invention comprises: a bottomed cylindrical outer shell, a piezoelectric unit, a matching layer and an adhesive layer; the piezoelectric unit and the matching layer are sequentially arranged in the bottomed cylindrical outer shell from top to bottom; the piezoelectric unit and the matching layer are adhered through the adhesive layer; the matching layer and the inner bottom surface of the bottomed cylindrical outer shell are adhered through the adhesive layer; the matching layer is used for insulating the bottomed cylindrical outer shell and the piezoelectric unit; the central thickness of the bottom surface of the bottomed cylindrical outer shell is smaller than the edge thickness; an oscillating fork body is arranged at the outer bottom surface of the bottomed cylindrical outer shell; the piezoelectric unit is used for driving the oscillating fork body to vibrate and receiving the signal after the oscillating fork body vibrates in different media; the oscillating fork body is a strip-shaped metal with a thick middle and thin ends. By setting the thickness of the bottom surface of the bottomed cylindrical outer shell, the stability of the vibration liquid level switch sensor is improved. The manufacturing process is simple and the cost is low. When affected by temperature, the working frequency changes stably. After multiple high and low temperature cycles, the working frequency at room temperature is stable and can be restored. Description of the Drawings

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0045] Figure 1 Structural schematic diagram of the vibration liquid level switch sensor in Embodiment 1 of the present invention;

[0046] Figure 2 Structural detail diagram of the vibration liquid level switch sensor in Embodiment 1 of the present invention;

[0047] Figure 3 Structural schematic diagram of the piezoelectric unit in Embodiment 1 of the present invention;

[0048] Figure 4 Structural schematic diagram of the piezoelectric unit in Embodiment 2 of the present invention;

[0049] Figure 5 Structural schematic diagram of the piezoelectric unit in Embodiment 3 of the present invention;

[0050] Figure 6 Structural thickness diagram of Embodiment 1 of the present invention;

[0051] Figure 7 Microstructural schematic diagram of the sintered nano-scale silver in Embodiment 4 of the present invention;

[0052] Figure 8 Three-dimensional axial cut view of the vibration liquid level switch sensor in Embodiment 1 of the present invention;

[0053] Description of the Drawings: 1 Oscillating fork body; 2 Rigid diaphragm; 3 Conical structure; 4 Step hole; 5 Annular enclosure structure; 6 Common annular sleeve; 7 Lead wire; 8 Adapter board; 9 Support pillar; 10 Piezoelectric unit; 11 Matching layer; 12 Annular groove; 13 Adhesive layer; 14 Piezoelectric emission part; 15 Spacing groove; 16 Piezoelectric receiving part; 17 Common negative electrode. Detailed Implementation Manner

[0054] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0055] The purpose of the present invention is to provide a vibration liquid level switch sensor, which improves the stability of the vibration liquid level switch sensor by setting the bottom thickness of the bottomed cylindrical housing, and has the advantages of simple structure and low manufacturing cost.

[0056] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the drawings and specific implementation manners.

[0057] Embodiment 1

[0058] As Figure 1-2 and Figure 8 shown, this embodiment provides a vibration liquid level switch sensor, including:

[0059] A bottomed cylindrical housing (including an oscillating fork body 1, a rigid diaphragm 2, and a step hole 4), a piezoelectric unit 10, and a matching layer 11;

[0060] The piezoelectric unit and the matching layer are sequentially arranged in the bottomed cylindrical housing from top to bottom;

[0061] The piezoelectric unit and the matching layer are bonded through an adhesive layer;

[0062] The matching layer and the inner bottom surface of the bottomed cylindrical housing are bonded through an adhesive layer; the matching layer is used to insulate the bottomed cylindrical housing and the piezoelectric unit; the central thickness of the bottom surface of the bottomed cylindrical housing is less than the edge thickness;

[0063] An oscillating fork body is provided at the outer bottom surface of the bottomed cylindrical housing; the piezoelectric unit is used to drive the oscillating fork body to vibrate and receive the signal after the oscillating fork body vibrates in different media; the oscillating fork body is a long strip-shaped metal that is thick in the middle and thin at both ends.

[0064] Among them, the bottomed cylindrical housing is a stepped bottomed cylindrical structure; the inner diameter of the upper part of the bottomed cylindrical housing is greater than the inner diameter of the bottom of the bottomed cylindrical housing;

[0065] Both the piezoelectric unit and the matching layer are in a disc-shaped structure;

[0066] The diameter of the piezoelectric unit is smaller than that of the matching layer;

[0067] The diameter of the matching layer is smaller than the inner diameter of the bottom of the cylindrical housing with a bottom.

[0068] In addition, the vibration liquid level switch sensor further includes:

[0069] A retaining structure (including an annular retaining structure 5 and a common annular sleeve 6), a transfer plate 8 and a plurality of support columns 9;

[0070] The retaining structure is in a stepped cylindrical structure; the outer diameter of the retaining structure is larger than the inner diameter of the bottom of the stepped cylindrical housing with a bottom; the outer diameter of the retaining structure is smaller than the upper inner diameter of the stepped cylindrical housing with a bottom; the retaining structure is arranged at the step inside the cylindrical housing with a bottom; the upper inner diameter of the retaining structure is larger than the bottom inner diameter of the retaining structure;

[0071] The diameter of the transfer plate is larger than the bottom inner diameter of the retaining structure; the diameter of the transfer plate is smaller than the upper inner diameter of the retaining structure; the transfer plate is arranged at the step inside the retaining structure; the transfer plate is connected to the piezoelectric unit through a transfer wire; the transfer plate is used to transfer the signal received by the piezoelectric unit.

[0072] A plurality of support columns are arranged at intervals on the lower bottom surface of the retaining structure; the lower bottom surfaces of the plurality of support columns are in contact with the matching layer.

[0073] Specifically, the matching layer is alumina ceramic;

[0074] The thickness of the matching layer is 0.4 mm - 0.6 mm.

[0075] The thickness of the middle part of the bottom surface of the cylindrical housing with a bottom is 1.6 mm to 1.8 mm;

[0076] The thickness of the edge of the bottom surface of the cylindrical housing with a bottom is 2 mm.

[0077] Preferably,

[0078] A plurality of annular grooves are provided on the inner bottom surface of the cylindrical housing with a bottom;

[0079] The annular grooves are used to enhance the bonding strength between the matching layer and the inner bottom surface of the cylindrical housing with a bottom.

[0080] Preferably, the piezoelectric unit includes:

[0081] A piezoelectric transmitting part and a piezoelectric receiving part;

[0082] The piezoelectric receiving part is circular; the piezoelectric transmitting part is annular; the piezoelectric transmitting part and the piezoelectric receiving part are concentrically arranged;

[0083] The piezoelectric emission part and the piezoelectric reception part share a common negative electrode.

[0084] Specifically, the adhesive layer is a two-component organic epoxy resin doped with nano-aluminum oxide powder; the edge thickness of the adhesive layer is greater than the middle thickness of the adhesive layer.

[0085] The object of the present invention is to preferably adopt a method with a simple manufacturing process and low cost to manufacture a vibration liquid level switch sensor that can work normally within a wide temperature range. Especially when affected by temperature, the working frequency changes stably. After multiple high and low temperature cycles, the working frequency at room temperature can be restored. The vibration liquid level switch sensor of the present invention includes a piezoelectric unit (including a piezoelectric emission part and a piezoelectric reception part) 10, a matching layer 11 that cooperates with the piezoelectric unit and a metal structure (rigid diaphragm), an annular enclosure structure 5 for ensuring limit concentricity, a rigid diaphragm 2 that can undergo mechanical deformation, and an oscillating fork structure 1 connected to the diaphragm. The piezoelectric emission part 14, the piezoelectric reception part 16, and the matching layer 11 are connected to the rigid diaphragm 2 through certain operations. To ensure the concentricity and positioning of the piezoelectric unit 10 and the rigid vibrating diaphragm 2, and the reliability of welding the external lead 7 of the piezoelectric drive part, an annular enclosure structure 5 is provided at the upper end, such as Figure 2 . A common annular sleeve is provided at the upper end of the annular enclosure structure 5 and is stuck in a stepped hole 4 on the upper side wall of the oscillating fork 1, and a plurality of struts are provided at the lower end and pressed against the peripheral outer edge of the matching layer 11.

[0086] The vibration coupling and synchronization between the components (including the matching layer 11 and the rigid diaphragm 2) in the vibration liquid level switch sensor are such that even when affected by temperature or thermal shock, their thermal expansion matching is in the best state. In addition, during long-term operation, the adhesive layer 13 between the piezoelectric unit 10 and the matching layer 11, and between the matching layer 11 and the rigid diaphragm 2 will not generate fine cracks inside when the temperature changes within a wide temperature range, which will affect the working frequency of the vibration switch to decrease or become abnormal. The manufacturing process is simple, and generally, it can make the working frequency of the vibration sensor stable and reliable, and not affected by temperature changes and thermal shock.

[0087] In order to achieve the performance of a vibration sensor with the least number of components, the present invention preferably selects a piezoelectric unit to simultaneously perform the functions of piezoelectric emission and piezoelectric reception. When the single piezoelectric unit is subjected to an alternating electric excitation, it generates a vibration working mode of continuous expansion and contraction in the radial direction, driving the rigid diaphragm 2 and the oscillating fork body 1 to vibrate inward or outward simultaneously. After the oscillating fork body 1 generates vibration, the piezoelectric receiving part 16 of the piezoelectric unit 10 will convert the received vibration energy into an electrical signal for output. To further realize the functions of the piezoelectric emission part and the piezoelectric receiving part on the same piezoelectric unit 10, in this invention patent, it is achieved by designing the shape of the piezoelectric unit as a round cake, sharing the negative electrode on one side, and simultaneously designing the piezoelectric emission unit and the piezoelectric receiving unit on the other side. In particular, the piezoelectric emission part 14 and the piezoelectric receiving part 16 on the same side are separated by a spacer groove, and there is no capacitive coupling effect between the two units, and they are independent of each other. The designed piezoelectric unit 10 has various forms and is not limited to a fixed structural form of a piezoelectric unit 10. Such as Figure 3 , on one side of the piezoelectric unit 10 is a shared negative electrode 17, and on the other side there are a piezoelectric emission part and a piezoelectric receiving part at the same time, and the two parts are separated by an annular spacer groove 15. Specifically, the piezoelectric emission part 14 is distributed around the piezoelectric unit 10 in the form of a ring, and the piezoelectric receiving part 16 is distributed on the piezoelectric unit 10 in a circular structure at the center of the ring. The shared negative electrode 17 is on the same side as the piezoelectric receiving part 16 and the piezoelectric emission part 14 in a flanged form. Under electric drive, acting on the positive and negative electrodes of the annular part, the piezoelectric emission part 14 of the annular part simultaneously changes between the outward stretching and contracting states, driving the left and right vibration of the oscillating fork body 1.

[0088] Furthermore, in this invention patent, the material of the rigid diaphragm 2 is preferably high-quality 316L stainless steel. Under the excitation of the piezoelectric emission part 14 of the piezoelectric unit, it generates a telescopic vibration in the radial direction, and the design of its thickness is particularly important. Through the simulation of the effective vibration frequency, energy transfer, and determination of the material elastic modulus by ANSYS software, as well as relying on rich ultrasonic experience, its thickness is generally set within 2 mm. Because if the thickness of the rigid diaphragm 2 is too thick, there will be a large loss of vibration energy; if the rigid diaphragm 2 is too thin, it will cause the working mode of the first-order vibration of the entire vibration sensor to be unstable, and it is easy to generate complex and distorted vibrations above the second order, which is not conducive to the reliable stability of the entire vibration sensor. Such as Figure 6 , the thickness of the rigid diaphragm 2 (i.e., the bottom surface of the cylindrical shell with a bottom) increases from the middle area to the edge area to ensure that the bonding surface of the rigid diaphragm 2 is flat. One side of its oscillating fork body 1 belongs to a structure that thickens from the middle area to the periphery, that is, the thickness of the middle area of the rigid diaphragm 2 is d0, and the thickness of the periphery is d1, and it is designed that d0 < d1. See Figure 5As shown in the figure. The rigid diaphragm 2 is designed in this way mainly because after the oscillating fork body 1 is vibrated, due to the restriction of the outer edge in the middle of the adhesive layer 13, its thermal expansion force is small, while the outer edge of the adhesive layer 13 is in a free state, and its thermal expansion force is larger than that in the middle of the adhesive layer 13. Therefore, especially in the edge area of adjacent layers, high shear forces and cracks will be generated. Therefore, improvements are made to the structure of the rigid diaphragm 2 so that the adhesive layer 13 in this area can better withstand the generated shear forces, thereby achieving the purpose of reducing crack generation and enabling the vibration of the piezoelectric unit to be transmitted to the rigid diaphragm 2 with as little loss as possible.

[0089] To further improve the reliable stability of the operating frequency of the vibration liquid level switch sensor within a certain wide temperature range, the bonding method of the piezoelectric unit 10 is optimized. When using the adhesive layer for bonding, to improve the bonding strength, the rigid diaphragm 2 is preferably degreased, rust-removed, etc., and then on the surface of the rigid diaphragm 2, through chemical etching treatment, especially the phosphating treatment process, assisted by mechanical treatment methods. In particular, the mechanical treatment method makes the surface of the rigid diaphragm 2 have a circular groove 12 design to increase the surface roughness of the rigid diaphragm 2, thereby increasing the bonding strength of the adhesive layer 13. Moreover, in addition to enhancing the bonding strength, the function of the circular groove 12 can also generate a small gap between the rigid diaphragm and the matching layer 11, playing a capillary action, which is more conducive to the effective filling of the adhesive. The structure of this circular groove 12 is realized by a laser marking machine: adjusting the power of the laser marking machine (35W to 45W) to etch a circular groove 12 with a depth of 0.05mm on the rigid diaphragm 2. The circular groove is shown Figure 2 as shown.

[0090] In the selection of the adhesive of the present invention, a two-component organic epoxy resin matrix is preferably used. Although during curing, the stress generated by the single-component room-temperature-curing organic resin is small, the existing problems are also obvious: large plasticity, relatively low rigidity, not high hardness, and low temperature resistance. Therefore, a two-component heat-curing organic epoxy resin is preferably used.

[0091] The adhesive is preferably a two-component organic resin. To ensure that the operating frequency of the vibration liquid level switch sensor is reliable at high temperature, the glass transition temperature of the adhesive is at least in the range of 140°C to 150°C. In addition, temperature heating is used as an auxiliary method during the curing process. In principle, the heating temperature does not exceed the Curie temperature of the piezoelectric unit 10, so that the piezoelectric unit 10 will not be depolarized. At the same time, in order to avoid the organic epoxy resin from generating sintering internal stress during the heating and curing process, the temperature is controlled according to the temperature curing curve (the temperature curing curve is obtained by consulting the stress reduction data, experimental verification, and rich experience during the curing process) and a certain preload is applied to the piezoelectric unit 10. The temperature sintering curve used is room temperature → 80°C, constant temperature 1h → 100°C, constant temperature 2h → 120°C, constant temperature 3h → 150°C, constant temperature 1h; the size of the preload is 0.5~1MPa.

[0092] In order to further optimize the bonding layer, a composite epoxy resin doped with nano-alumina powder (with a particle size of less than 800nm) is used on the organic epoxy resin matrix to form a uniform composite epoxy resin. The specific implementation process is as follows: First, the nano-alumina powder is pretreated, the main function of which is to prevent the agglomeration of the nano-alumina powder. Take 0.5% to 1% of the weight of the alumina powder, dilute it with an alcohol aqueous solution (water: alcohol = 1:9) 2 to 5 times the weight of the alumina powder, and then add the nano-alumina powder, stir it thoroughly, oscillate it with ultrasound for 30 minutes, and heat it to 100°C, keep it warm for 2 to 3 hours and dry it. After the nano-alumina powder is pretreated, 5% to 8% of the nano-alumina powder doped on the organic epoxy resin matrix is stirred mechanically and assisted by centrifuge swinging, and stirred fully in one direction, so that the nano-alumina powder and the resin are fully mixed, and observed under a high-power microscope (at least magnified to 10 times), and no agglomerates of the nano-alumina powder appear. Such composite epoxy resin makes full use of nano-aluminum oxide powder, because its particle size is very small, the surface area is very large, and the proportion of atoms in the surface layer is very large. Through sufficient stirring, it is fully absorbed and bonded with the polymer of the organic epoxy resin, which enhances the interface bonding between the aluminum oxide particles and the organic resin matrix, making the rigidity and dimensional stability of aluminum oxide more conducive to the toughness of the organic epoxy resin. The organic resin has a toughening and strengthening effect, and at the same time improves the shear strength of the composite resin at a high temperature of 180°C, so that the cracks in the bonding layer 13 disappear, greatly improving the reliable and stable working performance of the vibration liquid level switch sensor, and can ensure that the vibration sensor can work reliably and stably in a wide temperature range, and will not be affected by extreme high and low temperature cold and hot shocks in a wide temperature range. At the same time, nanoparticles, as fillers, play a positioning role in adjusting the thickness of the bonding layer 13 between the two bonding surfaces.

[0093] Furthermore, the organic epoxy resin of the composite material is preferably coated on the bonding surface of the bonded piezoelectric unit 10 and the matching layer 11 by screen printing, and both bonding surfaces are coated with the composite organic epoxy resin. The coating thickness is controlled by the mesh density of the screen so that the coating thickness is controlled within 30 μm. After coating, they are pressed together by a special tool. The tool is used to ensure the concentricity of the bonded parts (piezoelectric unit 10 and matching layer 11). After the pre-tightening force is applied, the coated organic epoxy resin will overflow to the side wall, ensuring that the overflowed organic epoxy resin glue forms an annular conical structure 3 along the outer edge of the piezoelectric unit 10 and the matching layer 11, as shown in FIG. Figure 2 shown.

[0094] The tooling adopts a non-uniform loading pressure method, specifically using a rod with a spherical head, so that the loading pressure generates a non-uniform pressure field on the surface of the bonding layer 13 with a circular center that is strong and the edges that are weak, so that excess organic epoxy resin adhesive is squeezed out from the edge of the piezoelectric unit 10 or the matching layer 11 to form a conical structure 3.

[0095] The conical structure 3 can reduce the generation of fine cracks inside the adhesive layer 13. This is because the middle area of the formed adhesive layer 13 is restricted by the outer edge, and its thermal expansion change is smaller than that of the outer edge part, and the outer edge part of the adhesive layer 13 is in a free state, which will generate high shear force and cracks. Therefore, by arranging the conical structure 3 that overflows the adhesive layer at the outer edge, the thickness of this area is increased, so that the outer edge part can better withstand the generated shear force.

[0096] In the present invention, in order to ensure that the matching layer 11 is concentrically bonded and fixed on the rigid diaphragm 2, and to ensure the reliability of the connection of the welding lead 7 from the piezoelectric unit 10, an annular enclosure structure 5 is used. The outer wall of the annular enclosure structure 5 ensures the curvature of the inner wall of the upper end of the rigid diaphragm 2. A common annular sleeve 6 is provided at its upper end, and an adapter plate 8 is embedded inside, and a welding point is provided. The welding lead 7 of the bottom piezoelectric unit can be welded on the welding point to achieve secondary transfer, thereby increasing the reliability of the welding lead 7. The lower end of the common annular sleeve 6 is provided with open pillars 9 in a free state at a certain distance, and the pillars extend from one side of the common annular sleeve 6. The fixed clamping part is located at the free end of each pillar 9, and the fixed clamping part is fixed around the outer edge of the matching layer 11 by means of the upper stepped hole 4 of the rigid diaphragm 2. The number of pillars 9 on the annular enclosure structure 5 is not limited, and it is generally believed that an even number is preferred to ensure balanced loading on the clamping structure. In the present invention, 12 pillars 9 are provided.

[0097] The matching layer 11 ensures electrical insulation between the piezoelectric unit 10, the rigid diaphragm 2, and the oscillating fork body 1. To further optimize the reliability of the vibration level switch sensor, the matching layer 11 is preferably a high-purity alumina ceramic with a purity as high as 99.9%. The higher the purity, the smaller the content of other components such as silicon oxide and titanium oxide. In this way, the denser and more rigid it is, the more conducive it is to the transmission of vibration energy. Moreover, its linear thermal expansion coefficient is between (6.8 - 8) / K×10 -6 and is between the piezoelectric unit ((3.2 - 4) / K×10 -6 ) and the metal material ((14 - 16) / K×10 -6 ), playing a role of stepped transition for the thermal expansion coefficients of different materials, enabling the effective transmission of vibration energy in different materials. Additionally, for the design of the thickness of the matching layer 11, if the matching layer is too thick, it will affect the transmission of vibration energy on the piezoelectric sheet; if the matching layer is too thin, under actual use or temperature influence, under the action of thermal stress and shear force, the matching layer 11 is prone to cracking or breaking, thus affecting the performance of the vibration switch device. Based on the material properties, expansion / contraction heat properties, vibration energy transmission characteristics of the piezoelectric unit 10, the configuration and thickness of the rigid diaphragm structure, as well as the expected operating temperature range of the device, the thickness of the matching layer is generally set within the range of 0.4 mm to 0.6 mm.

[0098] Embodiment 2

[0099] The difference between this embodiment and Embodiment 1 is that the piezoelectric unit includes:

[0100] a piezoelectric receiving part and two piezoelectric transmitting parts;

[0101] The piezoelectric receiving part is circular; the piezoelectric transmitting parts are semi-circular rings; the two piezoelectric transmitting parts are arranged to surround the piezoelectric receiving part; the piezoelectric transmitting parts and the piezoelectric receiving part are separated by a spacer groove; the piezoelectric transmitting parts and the piezoelectric receiving part share a negative electrode. As Figure 4 , the piezoelectric transmitting part 14 is divided into two parts by the spacer groove 15. After being electrically driven, its vibration working mode is the same as that of the piezoelectric unit 10 in Embodiment 1;

[0102] Embodiment 3

[0103] The difference between this embodiment and Embodiment 1 is that the piezoelectric unit includes:

[0104] a piezoelectric transmitting part, a piezoelectric receiving part, and a shared negative electrode;

[0105] The piezoelectric transmitting parts, the shared negative electrode, and the piezoelectric transmitting parts are arranged at intervals. As Figure 5, on one side of the piezoelectric unit 10 is the common negative electrode 17, and on the other side, the circular structure is divided into three parts. Among them, the middle part forms the common negative electrode 17 in the form of a flanged edge. The two sides are respectively the piezoelectric emission part 14 and the piezoelectric reception part 16, separated by a spacer groove 15 in the middle. For such a piezoelectric unit 10, under electric drive, acting on the positive electrode of the piezoelectric emission part 14 and the common negative electrode 17, the continuous stretching and contraction changes of this part of the piezoelectric ceramic unit drive one of the oscillating fork bodies 1 to vibrate. Furthermore, the other oscillating fork body 1 is driven by the already oscillating fork body 1, realizing the left - right vibration of the oscillating fork body 1.

[0106] Embodiment Four

[0107] The difference between this embodiment and Embodiment One is that the bonding layer is a silver - tin sintered material; the silver - tin sintered material is formed by mixing paste - like nano - silver and paste - like nano - tin materials, coating them on a steel mesh coated with nano - copper, and then sintering.

[0108] It is realized by using a nano - scale metal sintering method for composite structures / materials. In the present invention, a composite - particle - size nano - silver / tin sintering method is preferably adopted. The specific implementation process: using a nano - silver sintered material with a mixed and uniform particle size ranging from 50nm to 10μm. This material has a semi - fluid paste appearance. Using nano - silver particles with a composite of multiple particle sizes can build a denser structure in terms of structure. This is because small - particle - size particles can surround large - particle - size particles through physical adsorption or physical bonding. At the same time, nano - tin particles with a particle size in the range of 100nm to 200nm are doped in the nano - silver sintered material, which can further reduce the sintering temperature of the nano - silver paste, significantly dropping from 280°C to 235°C. In this way, better bonding of the piezoelectric unit 10 can be achieved without causing a decrease in the piezoelectric performance of the piezoelectric unit 10.

[0109] The paste - like nano - silver / tin material can be coated on the piezoelectric unit 10 and the matching layer 11 to be bonded by means such as template printing, coater, steel mesh, or screen printing. Brush a layer of nano - copper on the steel mesh or screen, and then brush the nano - silver / tin paste on the bonding surfaces of the piezoelectric unit 10 and the matching layer 11. Because after the nano - silver / tin paste is sintered, due to the volatilization of organic substances, many small pores will be generated. After improvement and optimization, the grid - like structure formed by nano - copper serves as a gas - discharging channel, reducing the generation of small pores.

[0110] Due to the low sintering temperature, very little stress is generated between the layers of the piezoelectric unit 10, the matching layer 11, and the rigid diaphragm 2. In the case of using a sintering paste with nano - scale silver, by applying a certain sintering pressure through a tooling method, the equipment cost required for sintering treatment can be significantly reduced, making this bonding technology easier to apply and promote. The microscopic structure after sintering is shown in Figure 7 as shown.

[0111] Compared with the current complex crimping implementation method, the vibration liquid level switch sensor of the present invention not only has a simple structure, but also can operate reliably for a long time at significantly different working temperatures (-40°C to 180°C), while showing acceptable operating performance and its performance will not be adversely affected.

[0112] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. At the same time, for those of ordinary skill in the art, based on the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A vibrating liquid level switch sensor, characterized in that, The vibration liquid level switch sensor comprises: A cylindrical housing with a bottom, a piezoelectric unit, a matching layer and an adhesive layer; The piezoelectric unit and the matching layer are sequentially arranged from top to bottom in a cylindrical housing with a bottom; The piezoelectric unit and the matching layer are bonded by an adhesive layer; The matching layer and the inner bottom surface of the bottomed cylindrical shell are bonded by an adhesive layer; the matching layer is used to insulate the bottomed cylindrical shell and the piezoelectric unit; the center thickness of the bottom surface of the bottomed cylindrical shell is less than the edge thickness; the bottom surface thickness of the bottomed cylindrical shell is set within a range of 2 mm; An oscillating fork is provided on the outer bottom surface of the bottomed cylindrical shell; the piezoelectric unit is used to drive the oscillating fork to vibrate and receive signals after the oscillating fork vibrates in different media; the oscillating fork is a long strip of metal that is thick in the middle and thin at both ends.

2. The vibration liquid level switch sensor according to claim 1, characterized in that: The bottomed cylindrical shell is a stepped bottomed cylindrical structure; the upper inner diameter of the bottomed cylindrical shell is larger than the bottom inner diameter of the bottomed cylindrical shell; The piezoelectric unit and the matching layer are both in a pancake-shaped structure; The diameter of the piezoelectric unit is smaller than the diameter of the matching layer; The matching layer has a diameter smaller than an inner diameter of a bottom portion of the bottomed cylindrical housing.

3. The vibration liquid level switch sensor according to claim 2, wherein The vibration liquid level switch sensor also includes: enclosure structure, adapter plate and multiple pillars; The enclosure structure is a stepped cylindrical structure; the outer diameter of the enclosure structure is larger than the bottom inner diameter of the stepped cylindrical shell with a bottom; the outer diameter of the enclosure structure is smaller than the upper inner diameter of the stepped cylindrical shell with a bottom; the enclosure structure is arranged at the step inside the cylindrical shell with a bottom; the upper inner diameter of the enclosure structure is larger than the bottom inner diameter of the enclosure structure; The adapter plate has a diameter greater than the bottom inner diameter of the enclosure structure; the adapter plate has a diameter less than the upper inner diameter of the enclosure structure; the adapter plate is disposed at a step in the enclosure structure; the adapter plate is connected to the piezoelectric unit via an adapter line; the adapter plate is used to transfer the signal received by the piezoelectric unit; The plurality of pillars are spaced apart on the lower bottom surface of the enclosure structure; the lower bottom surfaces of the plurality of pillars are in contact with the matching layer.

4. The vibration liquid level switch sensor according to claim 1, characterized in that: The matching layer is alumina ceramic; The thickness of the matching layer is 0.4 mm-0.6 mm; The thickness of the middle part of the bottom surface of the bottomed cylindrical shell is 1.6 mm to 1.8 mm; The edge thickness of the bottom surface of the bottom cylindrical shell is 2 mm.

5. The vibration liquid level switch sensor according to claim 1, characterized in that: A plurality of annular grooves are provided on the inner bottom surface of the bottomed cylindrical shell; The annular groove is used to enhance the bonding strength between the matching layer and the inner bottom surface of the bottomed cylindrical housing.

6. The vibrating liquid level switch sensor according to claim 2, wherein The piezoelectric unit comprises: A piezoelectric transmitting part and a piezoelectric receiving part; The piezoelectric receiving part is circular; the piezoelectric transmitting part is annular; the piezoelectric transmitting part and the piezoelectric receiving part are arranged concentrically; The piezoelectric transmitting portion and the piezoelectric receiving portion share a negative electrode.

7. The vibration liquid level switch sensor according to claim 2, characterized in that, The piezoelectric unit comprises: A piezoelectric receiving part and two piezoelectric transmitting parts; The piezoelectric receiving part is circular; the piezoelectric transmitting parts are semi-circular rings; the two piezoelectric transmitting parts are arranged to surround the piezoelectric receiving part; the piezoelectric transmitting parts and the piezoelectric receiving part are separated by a spacer groove; the piezoelectric transmitting parts and the piezoelectric receiving part share a negative electrode.

8. The vibration liquid level switch sensor according to claim 2, characterized in that, The piezoelectric unit includes: Piezoelectric transmitting parts, a piezoelectric receiving part and a shared negative electrode; The piezoelectric transmitting parts, the shared negative electrode and the piezoelectric transmitting parts are arranged at intervals.

9. The vibration liquid level switch sensor according to claim 1, characterized in that, The adhesive layer is a two-component organic epoxy resin doped with nano-alumina powder; the edge thickness of the adhesive layer is greater than the middle thickness of the adhesive layer.

10. The vibrating liquid level switch sensor according to claim 1, wherein The adhesive layer is a silver-tin sintered material; the silver-tin sintered material is formed by mixing paste-like nano-silver and paste-like nano-tin materials, coating them on a steel mesh coated with nano-copper, and then sintering.

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