Liquid level detection structure

Abstract

A liquid level detection structure relates to the technical field of liquid level detection facilities, and comprises a main body provided with a liquid inlet cavity communicated with the external space of the main body; the ultrasonic transmitting unit can transmit ultrasonic waves; the ultrasonic receiving unit can receive ultrasonic waves; the processing unit is electrically connected with the ultrasonic transmitting unit and the ultrasonic receiving unit; and the liquid inlet cavity is arranged on an ultrasonic propagation path formed between the ultrasonic transmitting unit and the ultrasonic receiving unit. Due to the fact that attenuation of ultrasonic waves is obviously different when the ultrasonic waves are transmitted in gas and liquid, a new detection signal can be formed through the new detection structure, whether the liquid level reaches the switching value or not is judged according to the intensity change condition of the ultrasonic waves, and the ultrasonic waves have efficient and reliable transmission capacity in the liquid environment. Therefore, misjudgment caused by influence of environmental factors is avoided.

Description

Technical Field

[0001] The present application relates to the technical field of liquid level detection facilities, and in particular to a liquid level detection structure. Background Art

[0002] In today's technical scenarios such as industrial automation, commercial facility operation and maintenance, and home device monitoring, liquid level monitoring of many water tanks, oil tanks, or other types of liquid storage tanks is involved. Accurate liquid level monitoring can strengthen safe operating procedures, improve resource utilization, and effectively prevent spills. It is a key factor in ensuring the safe and efficient operation of production and living facilities.

[0003] Currently, the most widely used liquid level monitoring facilities include reed switch float level gauges and Hall effect float level gauges. Both of these level gauges rely on a float equipped with a magnet to move up and down with the liquid level to detect the liquid level. The detection accuracy is easily affected by external magnetic fields such as the external environment magnetic field and magnetic impurities in the liquid. Utility Model Content

[0004] The present application provides a new liquid level detection structure that can generate a new detection signal.

[0005] In one embodiment, a liquid level detection structure is provided, comprising:

[0006] A main body, wherein the main body is provided with a liquid inlet cavity communicating with an external space of the main body;

[0007] An ultrasonic emitting unit, wherein the ultrasonic emitting unit is capable of emitting ultrasonic waves;

[0008] an ultrasonic receiving unit, wherein the ultrasonic receiving unit is capable of receiving ultrasonic waves;

[0009] and a processing unit, wherein the processing unit is electrically connected to the ultrasonic transmitting unit and the ultrasonic receiving unit;

[0010] The liquid inlet cavity is arranged on the ultrasonic wave propagation path formed between the ultrasonic wave transmitting unit and the ultrasonic wave receiving unit.

[0011] In one embodiment, a mounting cavity is provided in the main body, the ultrasonic transmitting unit and the ultrasonic receiving unit are both arranged in the mounting cavity, and the ultrasonic transmitting unit and the ultrasonic receiving unit are arranged opposite to each other.

[0012] In one embodiment, a circuit board is further included, and the processing unit, the ultrasonic transmitting unit and the ultrasonic receiving unit are all arranged on the circuit board, and the circuit board is arranged in the installation cavity.

[0013] In one embodiment, the installation cavity has a length direction, the liquid inlet cavity and the circuit board are respectively located on both sides of the length direction of the installation cavity, and the ultrasonic transmitting unit and the ultrasonic receiving unit are arranged on a side of the installation cavity close to the circuit board.

[0014] In one embodiment, it further includes a first threading tube, which is connected to the main body, an inner cavity of the first threading tube is connected to the installation cavity, and the first threading tube is used for allowing wires connected to the circuit board to pass through.

[0015] In one embodiment, the end of the first threading tube away from the main body is provided with a first connecting structure for connecting to a liquid storage tank for which liquid level detection is required.

[0016] In one embodiment, a second threading tube is provided at one end of the main body away from the first threading tube, and the inner cavity of the second threading tube is connected to the installation cavity; the liquid level detection structure also includes a connecting piece, and the connecting piece is used to connect between the first threading tubes of the two liquid level detection structures, between the second threading tubes of the two liquid level detection structures, or between the first threading tube of one of the liquid level detection structures and the second threading tube of another liquid level detection structure.

[0017] In one embodiment, a fixing member is further included, and the fixing member is arranged on the first threading tube or the second threading tube, and the fixing member is used to be connected to a liquid storage tank that needs to perform liquid level detection.

[0018] In one embodiment, the liquid inlet cavity passes through the main body, and the installation cavity is filled with sealant, and the sealant is used to seal the installation cavity.

[0019] In one embodiment, the frequency of the ultrasonic transmitting unit and / or the ultrasonic receiving unit is not less than 500 kHz.

[0020] In one embodiment, the ultrasonic transmitting unit and / or the ultrasonic receiving unit is a piezoelectric micromechanical ultrasonic transducer or a PZT-based piezoelectric ultrasonic transducer.

[0021] According to the liquid level detection structure of the above-mentioned embodiment, it includes a main body, an ultrasonic transmitting unit, an ultrasonic receiving unit and a processing unit. A liquid inlet cavity is provided on the main body, and an ultrasonic propagation path formed between the ultrasonic transmitting unit and the ultrasonic receiving unit passes through the liquid inlet cavity. Since there is a significant difference in the attenuation of ultrasonic waves when propagating in gas and liquid, when the liquid level changes, causing the medium in the liquid inlet cavity to change, the intensity of the ultrasonic signal received by the ultrasonic receiving unit will also change, and the intensity of the electrical signal converted by the ultrasonic receiving unit according to the intensity of the received ultrasonic signal will also change. That is, the new detection structure provided by the embodiment of the present application can convert the liquid level change information into the electrical signal intensity change information to form a new detection signal.

[0022] When in use, the processing unit can determine whether the liquid level has reached the set immersion chamber position based on the received electrical signal strength change information. Since the ultrasonic intensity change is used to determine whether the liquid level has reached the switch value, and ultrasonic waves have a relatively efficient and reliable transmission capability in a liquid environment, it is not easily affected by environmental factors and misjudgment occurs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the overall structure of a liquid level detection structure according to an embodiment;

[0024] Figure 2 for Figure 1 Schematic diagram of the explosion structure of the liquid level detection structure;

[0025] Figure 3 A structural schematic diagram of a liquid level detection structure in another embodiment in a continuous use state;

[0026] Figure 4 for Figure 3 Schematic diagram of the explosion structure of the liquid level detection structure in the continuous use state;

[0027] Figure 5 for Figure 3 A cross-sectional view of the liquid level detection structure in the state of continued use;

[0028] Figure 6 1 is a circuit diagram of a circuit board in one embodiment.

[0029] In the figure, 100, main body; 101, shell; 102, shell cover; 110, liquid inlet cavity; 120, installation cavity; 121, positioning rib plate; 130, first threading tube; 140, second threading tube; 150, connecting piece; 160, fixing piece; 161, fixing sleeve; 162, protrusion;

[0030] 200. Ultrasonic transmitting unit;

[0031] 300. Ultrasonic receiving unit;

[0032] 400. Circuit board. DETAILED DESCRIPTION

[0033] The present application is further described in detail below by specific embodiments in conjunction with the accompanying drawings. Wherein similar elements in different embodiments adopt associated similar element numbers. In the following embodiments, many detailed descriptions are intended to enable the present application to be better understood. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, and methods. In some cases, some operations related to the present application are not shown or described in the specification, in order to avoid the core part of the present application being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations based on the description in the specification and the general technical knowledge in the art.

[0034] In addition, the features, operations or characteristics described in the specification can be combined in any appropriate manner to form various implementations. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a required sequence, unless otherwise specified that a certain sequence must be followed.

[0035] The serial numbers of the components in this document, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings).

[0036] Currently, the most widely used liquid level monitoring facilities include reed switch float level gauges and Hall effect float level gauges. Both of these level gauges rely on a float equipped with a magnet to move up and down with the liquid level to detect the liquid level. The detection accuracy is easily affected by external magnetic fields such as the external environment magnetic field and magnetic impurities in the liquid.

[0037] In the embodiment of the present application, an ultrasonic transmitting unit 200 and an ultrasonic receiving unit 300 are provided, and a liquid inlet cavity 110 is provided on the main body 100, and the liquid inlet cavity 110 is specifically provided on the ultrasonic propagation path formed between the ultrasonic transmitting unit 200 and the ultrasonic receiving unit 300. When the medium in the liquid inlet cavity 110 changes with the change of the liquid level in the liquid storage tank, since the attenuation of ultrasonic waves when propagating in gas and liquid is significantly different, the intensity of the ultrasonic signal received by the ultrasonic receiving unit 300 will also change, and the intensity of the electrical signal converted by the ultrasonic receiving unit 300 according to the intensity of the received ultrasonic signal will also change. That is, through the new detection structure provided in the embodiment of the present application, the liquid level change information can be converted into electrical signal intensity change information to form a new detection signal.

[0038] The formation of the detection signal does not need to rely on the magnetic field, so it can effectively avoid the problem that the detection accuracy of the reed switch float type liquid level gauge and the Hall effect float type liquid level gauge is easily affected by the external magnetic field. In addition, since ultrasound has a relatively efficient and reliable transmission capability in a liquid environment, and the detection structure of the present application uses the change in ultrasound intensity to determine whether the liquid level has reached the switching value, it is not easily affected by the noise in the environment and misjudgment occurs.

[0039] Reference Figure 1-Figure 6 The present application provides a liquid level detection structure, including a main body 100, an ultrasonic transmitting unit 200, an ultrasonic receiving unit 300 and a processing unit (not shown in the figure).

[0040] In one embodiment, referring to Figure 1 and Figure 2 The main body 100 is provided with a liquid inlet cavity 110 which is connected to the external space of the main body 100. The ultrasonic transmitting unit 200 and the ultrasonic receiving unit 300 are arranged on both sides of the liquid inlet cavity 110. The ultrasonic transmitting unit 200 and the ultrasonic receiving unit 300 are electrically connected to the processing unit. An ultrasonic propagation path is formed between the ultrasonic transmitting unit 200 and the ultrasonic receiving unit 300. The ultrasonic propagation path passes through the liquid inlet cavity 110, that is, the liquid inlet cavity 110 is arranged on the ultrasonic propagation path formed between the ultrasonic transmitting unit 200 and the ultrasonic receiving unit 300.

[0041] The liquid inlet cavity 110 can be understood as a reflection area of ​​the liquid level change. The liquid inlet cavity 110 is connected to the external space of the main body 100. When the liquid level detection structure is in a working state in the liquid storage tank, and the liquid level in the liquid storage tank changes within the height range of the liquid inlet cavity 110, the liquid level in the liquid inlet cavity 110 will also change synchronously. Exemplarily, the liquid inlet cavity 110 is arranged in the middle area of ​​the main body 100 and is arranged through the main body 100. The liquid inlet cavity 110 can also be arranged in the edge area of ​​one side of the main body 100, or be arranged in a concave cavity with only one side open.

[0042] The main body 100 can be understood as the basic structural framework of the liquid level detection structure, and the ultrasonic transmitting unit 200 and the ultrasonic receiving unit 300 can be arranged inside the main body 100. Figure 2 The main body 100 includes a shell 101 and a shell cover 102. The shell 101 is provided with an installation cavity 120. The shell cover 102 is detachably covered at the cavity opening of the installation cavity 120 to seal the installation cavity 120. The ultrasonic transmitting unit 200 and the ultrasonic receiving unit 300 are both provided in the installation cavity 120. The ultrasonic transmitting unit 200 and the ultrasonic receiving unit 300 are arranged opposite to each other and are located on both sides of the liquid inlet cavity 110. In other examples, the ultrasonic transmitting unit 200 and the ultrasonic receiving unit 300 can also be installed outside the main body 100.

[0043] The processing unit can be used to stimulate the ultrasonic transmitting unit 200 to emit ultrasonic waves by being electrically connected to the ultrasonic transmitting unit 200 and the ultrasonic receiving unit 300, and receive the electrical signal converted by the ultrasonic receiving unit 300 after receiving the ultrasonic waves. The received electrical signal can also be analyzed to send a switch signal, and the sent switch signal can be used to control the liquid tank to inlet or pause the liquid inlet and discharge or pause the liquid discharge, etc. Exemplarily, the processing unit is specifically an ultrasonic detection chip, which is installed in the installation cavity 120. In other examples, the processing unit can also be set outside the main body 100, and can maintain electrical connection with the ultrasonic transmitting unit 200 and the ultrasonic receiving unit 300 through wires or the like.

[0044] Further, in some embodiments, referring to Figure 2 , further comprising a circuit board 400, on which the processing unit, the ultrasonic transmitting unit 200 and the ultrasonic receiving unit 300 are all disposed, and the circuit board 400 is disposed in the mounting cavity 120. The integrated design in which the processing unit, the ultrasonic transmitting unit 200 and the ultrasonic receiving unit 300 are all disposed on the circuit board 400 helps to improve the integration and reduce the volume of the liquid level detection structure.

[0045] Exemplarily, the main body 100 is generally a long strip-shaped shell structure having a length direction, the installation cavity 120 has a length direction, the liquid inlet cavity 110 and the circuit board 400 are respectively located on both sides of the length direction of the installation cavity 120, and the ultrasonic transmitting unit 200 and the ultrasonic receiving unit 300 are arranged on one side of the installation cavity 120 close to the circuit board 400. By arranging the liquid inlet cavity 110 on one side of the length direction of the installation cavity 120, sufficient installation space can be reserved for the circuit board 400, which is convenient for circuit board design; by reasonably arranging the positions of the liquid inlet cavity 110 and the circuit board 400, it is helpful to reduce the volume of the liquid level detection structure. In addition, a positioning rib 121 is provided in the installation cavity 120, and the positioning rib 121 and the cavity wall of the installation cavity 120 together form an installation position for the circuit board 400, and the positioning rib 121 is also provided with a card slot for clamping the ultrasonic transmitting unit 200 or the ultrasonic receiving unit 300, the circuit board 400 is clamped in the installation position, and the ultrasonic transmitting unit 200 and the ultrasonic receiving unit 300 are clamped in the card slot corresponding to the positioning rib 121. In other examples, the circuit board 400 can also be fixed by using a limit column, a positioning card slot, or other fixing methods.

[0046] In some embodiments, the main body 100 can also be designed into other shapes or structures as needed, and the position of the liquid inlet cavity 110 can also be adjusted as needed. For example, the liquid inlet cavity 110 is set in the middle of the main body 100, and the circuit board 400 is arranged around the liquid inlet cavity 110 in a ring-shaped arrangement similar to the shape of the liquid inlet cavity 110. In short, it can meet the actual design and detection needs.

[0047] In some embodiments, reference Figure 2 In order to facilitate power supply to the processing unit or facilitate the processing unit to send a switch signal, a first threading tube 130 is also included. The first threading tube 130 is connected to the main body 100. The inner cavity of the first threading tube 130 is connected to the installation cavity 120. The first threading tube 130 is used for the wires connected to the circuit board 400 to pass through. When in use, the first threading tube 130 can be installed on the wall of the liquid storage tank where the liquid level detection is required, and the wires can be passed through the wall of the liquid storage tank. In this way, it helps to reduce the risk of the liquid in the liquid storage tank entering the installation cavity 120 through the pipe mouth of the first threading tube 130 to damage the circuit board 400. The wires that pass through can also be connected to external facilities such as the infusion pump or control valve of the liquid storage tank according to the needs of use.

[0048] In order to facilitate the high and low water level detection in facilities such as water heaters and fish tanks, or high and low liquid level detection in water tanks corresponding to air conditioner pumps and other scenarios that require multi-point liquid level detection, it can be achieved by setting multiple liquid level detection structures with different installation heights or different first threading tube 130 lengths, or by connecting multiple liquid level detection structures in sequence to form a height difference between the detection positions.

[0049] For the liquid level detection structure that can be connected, in some embodiments, refer to Figure 3-Figure 5 A second threading tube 140 is provided at one end of the main body 100 away from the first threading tube 130, and the inner cavity of the second threading tube 140 is communicated with the installation cavity 120. A connecting member 150 is also included, and the connecting member 150 is used to connect the first threading tube 130 or the second threading tube 140 in different liquid level detection structures to achieve the connection of the two liquid level detection structures. The connection of the first threading tube 130 or the second threading tube 140 can be to connect two first threading tubes 130 in different liquid level detection structures, or to connect two second threading tubes 140 in different liquid level detection structures, or to connect the first threading tube 130 in one liquid level detection structure and the second threading tube 140 in another liquid level detection structure.

[0050] The liquid level detection structure with the second threading tube 140 can be used for other liquid level detections except the lowest point liquid level, and the liquid level detection structure without the second threading tube 140 can be used in conjunction to detect the lowest point liquid level. By using these two liquid level detection mechanisms in combination, liquid level detection can be performed in various multi-point liquid level detection scenarios. Of course, the liquid level detection structure with the second threading tube 140 can also be used in succession to perform multi-point liquid level detection. It is only necessary to add a blocking piece that can block the first threading tube 130 or the second threading tube 140 located at the lowest point. In different embodiments, the blocking piece can be set as a sealing plug or a blocking cover as needed. The blocking piece can be installed in a snap-on, threaded or other detachable connection form to seal the first threading tube 130 or the second threading tube 140.

[0051] For example, refer to Figure 4 and Figure 5 The connecting piece 150 is a connecting sleeve, one end of which is sleeved and fixed on the terminal pipe opening of the first threading tube 130 of a liquid level detection structure. The second threading tube 140 of the liquid level detection structure is used to be fixed on the top wall of the liquid storage tank whose liquid level needs to be detected. The other end of the connecting sleeve is sleeved and fixed on the terminal pipe opening of the first threading tube 130 of another liquid level detection structure. The connecting sleeve is plug-fitted with the first threading tubes 130 of the two liquid level detection structures through interference fit, so that the two liquid level detection structures are connected as a whole along the same axis.

[0052] In other embodiments, the connecting member 150 may also be a threaded tube that can be threadedly connected to the first threading tube 130 or the second threading tube 140, or an internal thread and an external thread that are matched with each other on the first threading tube 130 and the second threading tube 140 as the connecting member 150, so as to realize the matched connection between the first threading tube 130 and the second threading tube 140 of the two liquid level detection structures.

[0053] In some embodiments, in order to facilitate the installation of the liquid level detection structure in the liquid storage tank where the liquid level needs to be detected, refer to Figure 3-Figure 5 , and also includes a fixing member 160 for connecting to a liquid storage tank for liquid level detection. The fixing member 160 is installed on the first threading tube 130 or the second threading tube 140 so that the liquid level detection structure can be directly installed in the liquid storage tank for liquid level detection.

[0054] Exemplarily, the fixing member 160 includes a fixing sleeve 161 and a protrusion 162 integrally arranged outside the fixing sleeve 161. The fixing sleeve 161 is sleeved and fixed on the end of the second threading tube 140 away from the main body 100. The fixing sleeve 161 is provided with an external thread. A threaded hole is provided on the top wall of the liquid storage tank where the liquid level detection is required. The fixing sleeve 161 can be rotated and inserted into the threaded hole by screwing the protrusion 162, so that the liquid level detection structure is installed in the liquid storage tank. In other embodiments, the fixing member 160 can also be provided on the first threading tube 130 as needed. In addition, an external thread can be provided outside the first threading tube 130 or the second threading tube 140 as the fixing member 160. Any structure or component that can achieve the design purpose of connecting the first threading tube 130 to the liquid storage tank can be used as the fixing member 160.

[0055] In some embodiments, the installation cavity 120 is also filled with sealant (not shown in the figure), which is used to seal the installation cavity 120 so as to completely seal and protect the ultrasonic transmitting unit 200, the ultrasonic receiving unit 300, the processing unit and the circuit board 400 in the installation cavity 120.

[0056] In some embodiments, both the ultrasonic transmitting unit 200 and the ultrasonic receiving unit 300 can be selected as a piezoelectric micro-machined ultrasonic transducer (PMUT) or a PZT (Lead Zirconate Titanate) based piezoelectric ultrasonic transducer. The piezoelectric micro-machined ultrasonic transducer is based on the micro-electromechanical system (MEMS) technology and the characteristics of piezoelectric materials, and realizes the transmission and reception of ultrasonic waves through the positive and negative piezoelectric effects. The PZT-based piezoelectric ultrasonic transducer is made of PZT (Pb (Zr, Ti) O3) piezoelectric ceramic material, and realizes the transmission and reception of ultrasonic waves through the negative piezoelectric effect under the action of an external electric field. The ultrasonic transmitting unit 200 can emit an ultrasonic signal under the excitation of the processing unit, and the ultrasonic receiving unit 300 can receive the ultrasonic signal, and convert the received ultrasonic signal into an electrical signal and transmit it to the processing unit. In other embodiments, the ultrasonic transmitting unit 200 and the ultrasonic receiving unit 300 can also use other transducers that meet the design and use requirements.

[0057] In some embodiments, the ultrasonic transmitting unit 200 and the ultrasonic receiving unit 300 may use a high frequency band frequency of 500kHZ or above, such as 1000kHZ, 2000kHZ, 4000kHZ or even higher. Since environmental noise is usually in a lower frequency range, the characteristic of high-frequency ultrasonic waves that they are not easily disturbed by low-frequency noise in the environment during propagation helps to improve the stability and accuracy of liquid level detection. In addition, high-frequency ultrasonic waves have a shorter wavelength and a narrower beam, which helps to improve the resolution of the measurement, that is, they can more accurately distinguish small changes in the liquid level, and are suitable for application scenarios that require high-precision measurements.

[0058] In some embodiments, an adjusting resistor is also included. The adjusting resistor is electrically connected between the ultrasonic receiving unit 300 and the processing unit. The adjusting resistor can adjust the signal strength of the ultrasonic receiving unit 300 input into the processing unit to adjust the detection sensitivity of the liquid level detection structure and adapt to the sensitivity requirements of different liquid media and different application scenarios.

[0059] Exemplarily, the circuit board 400 is provided with an external circuit (such as Figure 6 As shown), the adjustment resistor is included in the external circuit.

[0060] For the external circuit, illustratively, the ultrasonic detection chip is provided with a first connection terminal (SENSE terminal), a second connection terminal (IN terminal), a third connection terminal (OUT terminal), a fourth connection terminal (VDD terminal), a fifth connection terminal (OSC terminal) and a sixth connection terminal (ground terminal), and the adjustment resistor includes a resistor R5 and a resistor R6 with adjustable resistance. Among them, the first connection terminal is connected to one end of the resistor R6, and the other end of the resistor R6 is connected to the second connection terminal and the resistor R5; the second connection terminal is connected to one end of the resistor R5, and the other end of the resistor R5 is connected to a capacitor C5, and the other end of the capacitor C5 is connected to the two connection terminals T10 and T11 of the ultrasonic receiving unit 300, and a resistor R4 is also connected between the connection terminal T11 of the ultrasonic receiving unit 300. The third connection terminal is used to connect to the OUT terminal and the VDD terminal of the external element, wherein the line connected to the VDD terminal is connected to a resistor R12; the fourth connection terminal is directly connected to the VDD terminal of the external element; the fifth connection terminal is connected to a capacitor C1, the other end of the capacitor C1 is connected to the two connection terminals T8 and T9 of the ultrasonic transmitting unit 200, and the line connected to the connection terminal T9 of the ultrasonic transmitting unit 200 is connected to a resistor R1, and one end of the resistor R1 connected to the ultrasonic transmitting unit connection terminal T9 is also used for grounding; the sixth connection terminal is used for grounding. In this way, by adjusting the resistance value of the resistor (i.e., resistors R5 and R6), the signal strength of the input processing unit of the ultrasonic receiving unit 300 can be adjusted to achieve the effect of adjusting the detection sensitivity of the liquid level detection structure. Of course, for some liquid level detection structures used in stable working conditions, the sensitivity of the liquid level detection structure can also be adjusted to a specific range by replacing resistors R5 and R6 with resistors of required resistance before installation.

[0061] The above specific examples are used to illustrate the present application, which is only used to help understand the present application and is not intended to limit the present application. For technicians in the technical field to which the present application belongs, they can also make some simple deductions, deformations or substitutions based on the ideas of the present application.

Claims

1. A liquid level detection structure, characterized in that: include: A main body, wherein the main body is provided with a liquid inlet cavity communicating with an external space of the main body; An ultrasonic emitting unit, wherein the ultrasonic emitting unit is capable of emitting ultrasonic waves; an ultrasonic receiving unit, wherein the ultrasonic receiving unit is capable of receiving ultrasonic waves; and a processing unit, wherein the processing unit is electrically connected to the ultrasonic transmitting unit and the ultrasonic receiving unit; The liquid inlet cavity is arranged on the ultrasonic wave propagation path formed between the ultrasonic wave transmitting unit and the ultrasonic wave receiving unit.

2. The liquid level detection structure according to claim 1, characterized in that: An installation cavity is arranged in the main body, and the ultrasonic emitting unit and the ultrasonic receiving unit are both arranged in the installation cavity, and the ultrasonic emitting unit and the ultrasonic receiving unit are arranged opposite to each other.

3. The liquid level detection structure according to claim 2, characterized in that: It also includes a circuit board, the processing unit, the ultrasonic transmitting unit and the ultrasonic receiving unit are all arranged on the circuit board, and the circuit board is arranged in the installation cavity.

4. The liquid level detection structure according to claim 3, characterized in that: The installation cavity has a length direction, the liquid inlet cavity and the circuit board are respectively located on both sides of the length direction of the installation cavity, and the ultrasonic transmitting unit and the ultrasonic receiving unit are arranged on one side of the installation cavity close to the circuit board.

5. The liquid level detection structure as claimed in claim 3 or 4, characterized in that: It also includes a first threading tube, which is connected to the main body. The inner cavity of the first threading tube is communicated with the installation cavity, and the first threading tube is used for allowing the wires connected to the circuit board to pass through.

6. The liquid level detection structure according to claim 5, characterized in that: A second threading tube is provided at one end of the main body away from the first threading tube, and the inner cavity of the second threading tube is connected to the installation cavity; the liquid level detection structure also includes a connecting piece, and the connecting piece is used to connect between the first threading tubes of the two liquid level detection structures, between the second threading tubes of the two liquid level detection structures, or between the first threading tube of one liquid level detection structure and the second threading tube of another liquid level detection structure.

7. The liquid level detection structure according to claim 6, characterized in that: It also includes a fixing part, which is arranged on the first threading tube or the second threading tube, and is used to be connected to a liquid storage tank that needs to perform liquid level detection.

8. The liquid level detection structure according to any one of claims 2 to 4, characterized in that: The liquid inlet cavity passes through the main body, and the installation cavity is filled with sealant, and the sealant is used to seal the installation cavity.

9. The liquid level detection structure according to any one of claims 1 to 4, characterized in that: The frequency of the ultrasonic transmitting unit and / or the ultrasonic receiving unit is not less than 500 kHz.

10. The liquid level detection structure according to any one of claims 1 to 4, characterized in that: The ultrasonic transmitting unit and / or the ultrasonic receiving unit is a piezoelectric micromechanical ultrasonic transducer or a PZT-based piezoelectric ultrasonic transducer.

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