Ultrasonic gas flow sensor

Abstract

The invention relates to an ultrasonic gas flow sensor. The ultrasonic gas flow sensor comprises an acoustic matching layer, a gas flow sensor and a gas flow sensor, wherein the acoustic matching layer is provided with a groove; the metal substrate is fixed at the bottom of the groove of the sound matching layer; the piezoelectric ceramic is fixed on one side, far away from the sound matching layer, of the metal substrate; wherein the sound matching layer, the metal substrate and the piezoelectric ceramic are coaxially arranged; the input end of the adapter plate is connected with the electrode of the piezoelectric ceramic, and the output end of the adapter plate is used for outputting an ultrasonic gas flow measurement signal; the shell is arranged on the periphery of the sound matching layer and the adapter plate, and a closed space is defined by the shell, the sound matching layer and the adapter plate; and the closed space is filled with a polymer. By adopting the ultrasonic gas flow sensor, the gas flow can be accurately measured.

Description

Technical Field

[0001] This application relates to the technical field of ultrasonic gas sensors, and particularly to an ultrasonic gas flow sensor. Background Art

[0002] As the core component of a gas meter, the working principle of an ultrasonic gas flow sensor is based on the relationship between the propagation time of ultrasonic waves in a flowing medium and the flow rate. The gas flow rate and flow are calculated by measuring the time difference between the forward and reverse propagation of the gas flow. The consistency of product performance is crucial for accurate gas flow measurement.

[0003] Currently, during the manufacturing process of ultrasonic gas flow sensors, due to the large attenuation of the gas to the echo signal, an air backing is usually used to reduce the influence of the backing on the sensitivity of the ultrasonic gas flow sensor. However, the air backing will cause the ultrasonic echo signal to be distorted due to reverberation. The distorted waveform makes it difficult to locate the characteristic points of the echo signal, affecting the accuracy of the ultrasonic propagation time and flow measurement, and also increasing the signal processing difficulty of the gas flow meter.

[0004] Therefore, there is a problem of insufficient accuracy in gas flow measurement in ultrasonic gas flow sensors in traditional technologies. Summary of the Invention

[0005] Based on this, it is necessary to provide an ultrasonic gas flow sensor for the above technical problems. Using this ultrasonic gas flow sensor can improve the accuracy of gas flow measurement.

[0006] An ultrasonic gas flow sensor, which includes:

[0007] An acoustic matching layer with grooves;

[0008] A metal substrate fixed to the bottom of the groove of the acoustic matching layer;

[0009] A piezoelectric ceramic fixed on the side of the metal substrate away from the acoustic matching layer;

[0010] Among them, the acoustic matching layer, the metal substrate, and the piezoelectric ceramic are coaxially arranged;

[0011] An adapter board, the input end of the adapter board is connected to the electrode of the piezoelectric ceramic, and the output end of the adapter board is used to output an ultrasonic gas flow measurement signal;

[0012] A housing, the housing is arranged around the acoustic matching layer and the adapter board, and forms a sealed space with the acoustic matching layer and the adapter board; the sealed space is filled with a polymer.

[0013] In one embodiment, the height of the side wall of the groove of the acoustic matching layer is between 1 / 2 and 4 / 5 of the height of the piezoelectric ceramic.

[0014] In one embodiment, the bottom wall thickness of the acoustic matching layer is 1 / 4 of the ultrasonic propagation wavelength, and / or the difference between the inner diameter dimension of the groove of the acoustic matching layer and the outer diameter dimension of the metal substrate is between 0.1 and 0.2 mm.

[0015] In one embodiment, the projection of the piezoelectric ceramic on the metal substrate falls within the area where the metal substrate is located.

[0016] In one embodiment, there are a preset number of grooving in the piezoelectric ceramic.

[0017] In one embodiment, the depth of the grooving in the height direction of the piezoelectric ceramic is between 5 / 6 and 1 of the height of the piezoelectric ceramic.

[0018] In one embodiment, the thickness of the piezoelectric ceramic is determined according to the vibration frequency of the piezoelectric ceramic in the thickness direction.

[0019] In one embodiment, the inner diameter dimension of the housing is greater than the outer diameter dimension of the acoustic matching layer at the corresponding position; the difference between the outer diameter dimension of the housing and the outer diameter dimension of the acoustic matching layer at the corresponding position is in the range of 0.1 to 0.2 mm.

[0020] In one embodiment, the polymer is an impedance material with an acoustic impedance less than a preset threshold.

[0021] In one embodiment, the potting height of the polymer is between 5 / 6 and 1 of the height of the piezoelectric ceramic.

[0022] For the above ultrasonic gas flow sensor, the acoustic matching layer has grooves, the metal substrate is fixed at the bottom of the grooves of the acoustic matching layer, the piezoelectric ceramic is fixed on the side of the metal substrate away from the acoustic matching layer, and the acoustic matching layer, the metal substrate and the piezoelectric ceramic are coaxially arranged. The input end of the adapter plate is connected to the electrode of the piezoelectric ceramic, and the output end of the adapter plate is used to output an ultrasonic gas flow measurement signal. The housing is arranged on the periphery of the acoustic matching layer and the adapter plate, and forms a sealed space with the acoustic matching layer and the adapter plate. The sealed space is filled with a polymer. Compared with the linear acoustic matching layer of the existing ultrasonic gas flow sensor, the possibility of glue overflow during the bonding of the acoustic matching layer and the metal housing is reduced, thereby improving the received amplitude and sensitivity of the ultrasonic gas flow sensor product. Moreover, the reduction of glue overflow can reduce the difficulty of subsequent assembly of the ultrasonic gas flow sensor product, and at the same time avoid the direct contact of the metal housing with the gas, especially corrosive gas. Also, the metal housing of the existing ultrasonic gas flow sensor is removed, and the metal substrate is used to replace the original metal housing, which reduces the impedance of the piezoelectric ceramic sheet after bonding, is beneficial to reducing signal attenuation and improving signal stability. And, by arranging the housing on the periphery of the acoustic matching layer and the adapter plate, and forming a sealed space with the acoustic matching layer and the adapter plate, the formed sealed space can prevent the influence of the external environment on the internal components of the ultrasonic gas flow sensor. Filling the formed sealed space with a polymer can improve the sealing performance of the ultrasonic gas flow sensor. The backlining structure formed in this way can avoid harmful mode coupling, weaken the lateral coupling, that is, reduce the energy loss in the transverse direction, improve the energy utilization efficiency, make the energy concentrated in the thickness direction, improve the energy conversion efficiency and directivity. Generally speaking, it can ensure the high sensitivity of the ultrasonic gas flow sensor, effectively reduce the distortion of the ultrasonic gas flow sensor, and improve the detection accuracy of the ultrasonic gas flow sensor. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following will briefly introduce the drawings required for use in the description of the embodiments or related technologies. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Figure 1 Schematic diagram of an existing ultrasonic gas flow sensor in an embodiment;

[0025] Figure 2 Schematic diagram of glue overflow during the assembly of an existing ultrasonic gas flowmeter in an embodiment;

[0026] Figure 3 Schematic diagram of the ultrasonic gas flow sensor of the present application;

[0027] Figure 4 Schematic diagram of positioning the acoustic matching layer, metal substrate and piezoelectric ceramic using a positioning tooling in one embodiment;

[0028] Figure 5 Schematic diagram of calculating the absolute flight time based on the starting point and peak-to-peak value in one embodiment;

[0029] Figure 6 Cross-sectional schematic diagram of an ultrasonic gas flow sensor in one embodiment;

[0030] Figure 7 Schematic diagram of the received waveform distortion in one embodiment.

[0031] Figure 8 Schematic diagram of the waveform received by using the ultrasonic gas flow sensor of the present application in one embodiment.

[0032] Among them, the meanings of the respective reference numerals are as follows:

[0033] 110, disc-shaped acoustic matching layer; 120, metal shell; 130, piezoelectric ceramic sheet; 140, adhesive; 150, external potting adhesive; 160, wire; 310, acoustic matching layer; 320, metal substrate; 330, piezoelectric ceramic; 340, adapter board; 350, housing; 360, polymer. Detailed implementation manners

[0034] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. Embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the specification of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0036] It can be understood that the terms "first", "second", etc. used in this application can be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element. For example, without departing from the scope of this application, the first resistor can be called the second resistor, and similarly, the second resistor can be called the first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0037] It can be understood that for the "connection" in the following embodiments, if there is transmission of electrical signals or data between the connected circuits, modules, units, etc., it should be understood as "electrical connection", "communication connection", etc.

[0038] It can be understood that "at least one" means one or more, and "a plurality" means two or more. "At least part of an element" means part or all of the element.

[0039] As used herein, the singular forms "a", "an" and "the" may also include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprises / include" or "has" etc. specify the presence of the stated features, wholes, steps, operations, components, parts or combinations thereof, but do not preclude the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the related listed items.

[0040] The ultrasonic gas flow sensor is a core component used in gas meters. Based on the principle of testing the relationship between the time of ultrasonic wave propagation in a flowing medium and the flow rate, the flow velocity and flow rate of the gas are calculated by measuring the time difference between the forward and reverse propagation of the gas flow. Therefore, the consistency of the product performance of the ultrasonic gas flow sensor directly affects the measurement accuracy of the gas flow rate.

[0041] Figure 1 The schematic diagram of the existing ultrasonic gas flow sensor is shown. The existing ultrasonic gas flow sensor includes a disc-shaped acoustic matching layer 110, a metal shell 120, a piezoelectric ceramic sheet 130, an adhesive 140, an external potting adhesive 150 and a wire 160. The disc-shaped acoustic matching layer 110 is bonded to the metal shell 120 through the adhesive 140, and the piezoelectric ceramic sheet 130 is fixed at the bottom of the groove of the metal shell 120.

[0042] Through research and analysis of the existing ultrasonic gas flow sensors, the inventors of the present application found that the existing ultrasonic gas flow sensors bond the disc-shaped acoustic matching layer 110 to the piezoelectric ceramic 130 or the metal shell 120 with glue, which easily causes glue overflow at the edge of the disc-shaped acoustic matching layer 110 (refer to Figure 2), as well as problems such as difficult tooling positioning and hard-to-control concentricity, which affect product consistency. In addition, for gas sensors, due to the very large attenuation of gas to the echo signal, an air backing is often used to reduce the influence of the backing on the sensitivity of the gas sensor. However, the air backing will cause the ultrasonic echo signal to be distorted due to reverberation. The distorted waveform makes it difficult to locate the characteristic points of the echo signal, affecting the measurement accuracy of the ultrasonic propagation time and gas flow rate. At the same time, it also increases the signal processing difficulty of the gas flowmeter. Therefore, how to improve the consistency of the ultrasonic gas flow sensor and improve the measurement accuracy of the ultrasonic propagation time and gas flow rate is an urgent problem to be solved currently. To solve this problem, the inventors of this application propose an ultrasonic gas flow sensor.

[0043] As Figure 3 shown, an ultrasonic gas flow sensor according to an embodiment includes: an acoustic matching layer 310, a metal substrate 320, a piezoelectric ceramic 330, an adapter board 340, and a housing 350. The acoustic matching layer 310 has a groove. The metal substrate 320 is fixed to the bottom of the groove of the acoustic matching layer 310. The piezoelectric ceramic 330 is fixed to the side of the metal substrate 320 away from the acoustic matching layer 310. Among them, the acoustic matching layer 310, the metal substrate 320, and the piezoelectric ceramic 330 are coaxially arranged. The input end of the adapter board 340 is connected to the electrode of the piezoelectric ceramic 330, and the output end of the adapter board 340 is used to output an ultrasonic gas flow measurement signal. The housing 350 is disposed around the acoustic matching layer 310 and the adapter board 340, and forms a closed space with the acoustic matching layer 310 and the adapter board 340. The closed space is filled with a polymer 360.

[0044] Among them, the acoustic matching layer 310 has a concave design. The acoustic matching layer 310 is a semi-wrapping structure, and the metal substrate 320 and the piezoelectric ceramic 330 can be directly embedded in the groove of the acoustic matching layer 310. In practical applications, as Figure 4 shown, a positioning tooling can be used to ensure the concentricity of the acoustic matching layer 310, the metal substrate 320, and the piezoelectric ceramic 330. The piezoelectric ceramic 330 can be a square piezoelectric ceramic or other shaped piezoelectric ceramics.

[0045] Among them, the housing 350 can be circular or any shape that can enclose the acoustic matching layer 310 and the adapter board 340 to form a closed space. The two ends of the housing 350 are also provided with card slots.

[0046] The ultrasonic gas flow sensor of this embodiment reduces the possibility of glue overflow when the acoustic matching layer is bonded to the metal housing compared with the linear acoustic matching layer of the existing ultrasonic gas flow sensor, thereby improving the received amplitude and sensitivity of the ultrasonic gas flow sensor product; moreover, the reduction of glue overflow can reduce the difficulty of subsequent assembly of the ultrasonic gas flow sensor product and avoid the direct contact between the metal housing and the gas, especially corrosive gas; at the same time, the metal housing of the existing ultrasonic gas flow sensor is cancelled, and a metal substrate is used to replace the original metal housing, reducing the impedance of the piezoelectric ceramic sheet after bonding, which is beneficial to reducing signal attenuation and improving signal stability; furthermore, by arranging the outer shell around the acoustic matching layer and the adapter board and enclosing with the acoustic matching layer and the adapter board to form a sealed space, the formed sealed space can prevent the external environment from affecting the internal components of the ultrasonic gas flow sensor. Filling the formed sealed space with polymer can improve the sealing performance of the ultrasonic gas flow sensor. The formed backlining structure can avoid harmful mode coupling, weaken the lateral coupling, that is, reduce the energy loss in the transverse direction, improve the energy utilization efficiency, concentrate the energy in the thickness direction, improve the energy conversion efficiency and directivity, and can improve the gas flow measurement accuracy of the ultrasonic gas flow sensor.

[0047] In an exemplary embodiment, the height of the groove side wall of the acoustic matching layer 310 is between 1 / 2 and 4 / 5 of the height of the piezoelectric ceramic 330.

[0048] In this embodiment, by setting the height of the groove side wall of the acoustic matching layer between 1 / 2 and 4 / 5 of the height of the piezoelectric ceramic, the piezoelectric ceramic can be positioned and it is beneficial to the subsequent potting of the polymer.

[0049] In an exemplary embodiment, the thickness of the acoustic matching layer 310 is 1 / 4 of the ultrasonic propagation wavelength, and / or the difference between the inner diameter dimension of the groove of the acoustic matching layer 310 and the outer diameter dimension of the metal substrate 320 is between 0.1 and 0.2 mm.

[0050] In practical applications, the bottom wall thickness and the side wall thickness of the acoustic matching layer 310 can be different.

[0051] In this embodiment, by setting the thickness of the acoustic matching layer 310 to 1 / 4 of the ultrasonic propagation wavelength, the best acoustic impedance matching can be achieved, thereby improving the transmission efficiency of ultrasonic waves. By setting the difference between the inner diameter of the groove of the acoustic matching layer 310 and the outer diameter of the metal substrate 320 within the range of 0.1 - 0.2 mm, it can ensure that the metal substrate 320 is fixed more firmly in the groove of the acoustic matching layer 310, reduce vibration and displacement during the manufacturing process, contribute to improving the overall mechanical stability of the ultrasonic gas flow sensor, and extend the service life. By setting the thickness of the acoustic matching layer 310 to 1 / 4 of the ultrasonic propagation wavelength and setting the difference between the inner diameter of the groove of the acoustic matching layer 310 and the outer diameter of the metal substrate 320 within the range of 0.1 - 0.2 mm, it can improve the overall structural stability of the ultrasonic gas flow sensor while improving the ultrasonic transmission efficiency.

[0052] In an exemplary embodiment, the projection of the piezoelectric ceramic 330 on the metal substrate 320 falls within the area where the metal substrate 320 is located.

[0053] In practical applications, the outer diameter of the metal substrate 320 is larger than the outer diameter of the circumscribed circle of the piezoelectric ceramic 330.

[0054] In this embodiment, by setting the projection of the piezoelectric ceramic on the metal substrate to fall within the area where the metal substrate is located, the metal sheet can better transmit and amplify the vibration of the piezoelectric ceramic, while protecting the piezoelectric ceramic from direct erosion by the gas environment, which can improve the sensitivity and mechanical stability of the sensor, and optimize the transmission efficiency of sound waves.

[0055] In an exemplary embodiment, there are a preset number of grooving in the piezoelectric ceramic 330.

[0056] Among them, the number of grooving of the piezoelectric ceramic 330 can be determined according to actual needs. For example, three grooves can be made inside the piezoelectric ceramic 330. When there are three grooves inside the piezoelectric ceramic 330, the overall manufacturing process of the ultrasonic gas flow sensor is relatively simple, the cost is low, and it is suitable for large-scale production.

[0057] In this embodiment, by setting a preset number of grooving inside the piezoelectric ceramic, the vibration mode of the piezoelectric ceramic can be optimized, lateral coupling can be reduced, and the energy can be more concentrated in the thickness direction, thereby improving the energy conversion efficiency.

[0058] In an exemplary embodiment, the depth of the grooving in the height direction of the piezoelectric ceramic 330 is between 5 / 6 and 1 of the height of the piezoelectric ceramic 330.

[0059] In practical applications, the grooving depth of the piezoelectric ceramic 330 in the height direction can be represented as a, and the height of the piezoelectric ceramic 330 can be represented as b. In actual settings, the grooving depth a of the piezoelectric ceramic 330 in the height direction should be more than 5 times the un-grooved depth c. The un-grooved depth c is equal to the height b of the piezoelectric ceramic 330 minus the grooving depth a of the piezoelectric ceramic 330 in the height direction. Therefore, the grooving depth a of the piezoelectric ceramic 330 in the height direction and the un-grooved depth c satisfy the relational expression a >= 5c. From this, it can be inferred that the grooving depth a of the piezoelectric ceramic 330 in the height direction and the height b of the piezoelectric ceramic 330 satisfy the relational expression a >= 5*(b - a), that is, a >= 5b / 6.

[0060] In this embodiment, by setting the depth of the grooving in the height direction of the piezoelectric ceramic to be between 5 / 6 and 1 times the height of the piezoelectric ceramic, it is possible to ensure the best performance of the piezoelectric ceramic at the required operating frequency while avoiding damage to the structural integrity of the piezoelectric ceramic.

[0061] In an exemplary embodiment, the thickness of the piezoelectric ceramic 330 is determined according to the vibration frequency of the piezoelectric ceramic 330 in the thickness direction.

[0062] In practical applications, the thickness d of the piezoelectric ceramic 330 is determined according to the vibration frequency of the piezoelectric ceramic 330 in the thickness direction. Specifically, the determination method of the thickness d of the piezoelectric ceramic 330 can be expressed as d = N / Fr, where N represents the vibration frequency constant of the piezoelectric ceramic in the thickness direction, and Fr is the vibration frequency of the piezoelectric ceramic 330 in the thickness direction.

[0063] In this embodiment, the thickness of the piezoelectric ceramic 330 is determined according to the vibration frequency of the piezoelectric ceramic 330 in the thickness direction, which can ensure that the ultrasonic gas flow sensor can achieve the best performance at a specific frequency.

[0064] In an exemplary embodiment, the inner diameter dimension of the housing is larger than the outer diameter dimension of the acoustic matching layer at the corresponding position; the difference between the outer diameter dimension of the housing and the outer diameter dimension of the acoustic matching layer at the corresponding position is in the range of 0.1 - 0.2 mm.

[0065] In practical applications, as Figure 3 shown, the inner diameter dimension of the part where the housing 350 is in contact with the acoustic matching layer 310 is larger than the outer diameter dimension of the acoustic matching layer 310, and the difference between the outer diameter dimension of the part where the housing 350 is in contact with the acoustic matching layer 310 is within 0.1 - 0.2 mm.

[0066] The setting of this embodiment can provide better mechanical support, reduce the vibration and displacement of the ultrasonic gas flow sensor during operation, improve the mechanical stability of the ultrasonic gas flow sensor. At the same time, it is beneficial to fill a sealing material in a closed space formed by enclosing the housing, the acoustic matching layer and the adapter plate, so as to improve the sealing performance of the ultrasonic gas flow sensor.

[0067] In an exemplary embodiment, the polymer 360 is an impedance material with an acoustic impedance less than a preset threshold.

[0068] Among them, the polymer 360 can be a low acoustic impedance material. For example, the polymer 360 can be a material with an acoustic impedance less than 4 MPa*s / m.

[0069] The setting of this embodiment can more effectively reduce the energy loss of sound waves during propagation and improve the transmission efficiency of sound waves by using a polymer material with a low acoustic impedance.

[0070] In an exemplary embodiment, the potting height of the polymer 360 is between 5 / 6 and 1 of the height of the piezoelectric ceramic 330.

[0071] Among them, the potting height of the polymer 360 is 5 / 6 to 1 of the piezoelectric ceramic 330.

[0072] The setting of this embodiment can improve the overall mechanical stability of the ultrasonic gas flow sensor, prevent problems such as measurement errors or poor contact caused by component displacement or loosening, and ensure the long-term stable operation of the sensor.

[0073] For the convenience of those skilled in the art to understand, the following specifically describes the beneficial effects that can be achieved after filling the polymer in the closed space.

[0074] In the existing ultrasonic gas flow sensor, when calculating the absolute flight time of ultrasonic waves using the threshold method, the echo signal is located by the starting point or the peak-to-peak value to obtain the time difference between the downstream and upstream flows, so as to calculate the gas flow velocity. The principle is as Figure 5 shown. However, when the sound wave generated by the transmitter of the ultrasonic gas flow sensor propagates repeatedly in the pipeline (as Figure 6 shown) and reaches the receiver, the received waveform (as Figure 7 shown) will be distorted due to reverberation. This situation is likely to cause misidentification of characteristic points, thus seriously affecting the gas flow measurement accuracy, especially when affected by factors such as the medium, flow velocity and temperature change in the pipeline. The specific reason for this problem is that the piezoelectric ceramic has small anisotropy and a large radial electromechanical coupling coefficient, which will cause great interference to the vibration in the thickness direction, making it difficult to obtain a single vibration in the thickness direction, resulting in a large reverberation of the ultrasonic received wave, and thus unable to accurately measure the gas flow rate and flow velocity.

[0075] For the ultrasonic gas flow sensor of the present application, after the polymer 360 is filled inside the acoustic matching layer 310, harmful mode coupling can be avoided, while the lateral coupling is weakened and the energy is concentrated in the thickness direction, maintaining the high sensitivity and piezoelectricity of the piezoelectric ceramic sheet 330, and obtaining an ultrasonic gas flow sensor with a thickness expansion vibration mode of high bandwidth and high sensitivity. The received waveform after filling the polymer 360 is as follows Figure 8 shown.

[0076] It can be understood that the above ultrasonic gas flow sensor can also adopt other forms, not limited to the forms already mentioned in the above embodiments, as long as it can achieve the function of the ultrasonic gas flow sensor.

[0077] In the description of this specification, the descriptions referring to terms such as "some embodiments", "other embodiments", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic description of the above terms does not necessarily refer to the same embodiment or example.

[0078] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0079] The above-described embodiments only represent several implementation manners of the present application, and their descriptions are relatively specific and detailed, but should not be construed as a limitation on the scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. An ultrasonic gas flow sensor, characterized in that, The ultrasonic gas flow sensor includes: An acoustic matching layer, which has a groove; A metal substrate, fixed to the bottom of the groove of the acoustic matching layer; A piezoelectric ceramic, fixed on the side of the metal substrate away from the acoustic matching layer; Wherein, the acoustic matching layer, the metal substrate and the piezoelectric ceramic are coaxially arranged; An adapter board, the input end of the adapter board is connected to the electrode of the piezoelectric ceramic, and the output end of the adapter board is used to output an ultrasonic gas flow measurement signal; A housing, the housing is arranged around the acoustic matching layer and the adapter board, and forms a sealed space with the acoustic matching layer and the adapter board; the sealed space is filled with a polymer.

2. The ultrasonic gas flow sensor according to claim 1, characterized in that, The height of the side wall of the groove of the acoustic matching layer is between 1 / 2 and 4 / 5 of the height of the piezoelectric ceramic.

3. The ultrasonic gas flow sensor according to claim 1, characterized in that The bottom wall thickness of the acoustic matching layer is 1 / 4 of the ultrasonic propagation wavelength, and / or, the difference between the inner diameter size of the groove of the acoustic matching layer and the outer diameter size of the metal substrate is between 0.1 and 0.2 mm.

4. The ultrasonic gas flow sensor according to claim 1, characterized in that, The projection of the piezoelectric ceramic on the metal substrate falls within the area where the metal substrate is located.

5. The ultrasonic gas flow sensor according to claim 1, characterized in that, There are a preset number of scribing grooves inside the piezoelectric ceramic.

6. The ultrasonic gas flow sensor according to claim 5, characterized in that, The depth of the scribing grooves in the height direction of the piezoelectric ceramic is between 5 / 6 and 1 of the height of the piezoelectric ceramic.

7. The ultrasonic gas flow sensor according to claim 1, characterized in that, The thickness of the piezoelectric ceramic is determined according to the vibration frequency of the piezoelectric ceramic in the thickness direction.

8. The ultrasonic gas flow sensor according to claim 1, characterized in that, The inner diameter size of the housing is larger than the outer diameter size of the acoustic matching layer at the corresponding position; the difference between the outer diameter size of the housing and the outer diameter size of the acoustic matching layer at the corresponding position is in the range of 0.1 to 0.2 mm.

9. The ultrasonic gas flow sensor according to claim 1, wherein The polymer is an impedance material with an acoustic impedance less than a preset threshold.

10. The ultrasonic gas flow sensor according to claim 1, characterized in that, The potting height of the polymer is between 5 / 6 and 1 of the height of the piezoelectric ceramic.

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