Ultrasonic gas sensor

Abstract

The utility model discloses an ultrasonic gas sensor, and belongs to the technical field of ultrasonic sensors. An ultrasonic gas sensor comprises an annular rigid shell, the lower portion of the rigid shell is connected with a first matching layer, the first matching layer is provided with a protruding part, the protruding part is inserted into the middle of the rigid shell, a cavity is formed in the protruding part, and a circuit board, piezoelectric ceramics and an acoustic damping layer are fixedly arranged in the cavity. The piezoelectric ceramic is pasted on the first matching layer, the circuit board is electrically connected with the piezoelectric ceramic, a flexible rubber sleeve is arranged on the outer side of the rigid shell, the flexible rubber sleeve is matched with the first matching layer to completely wrap the rigid shell, a wire is electrically connected to the circuit board, and the wire penetrates through the flexible rubber sleeve. The acoustic damping layer is arranged in the cavity, so that the aging rate of the acoustic damping layer can be effectively reduced, and the service life of the device is prolonged.

Description

Technical Field

[0001] This application relates to the field of ultrasonic sensor technology, and more specifically, to an ultrasonic gas sensor. Background Technology

[0002] Ultrasonic gas sensing technology utilizes the characteristic that the propagation speed (or acoustic impedance) of sound waves in a gas varies with the gas composition, temperature, and pressure. By measuring the flight time or phase difference of the ultrasonic waves along a fixed path, gas parameters can be indirectly deduced. This technology has advantages such as being non-contact, having no moving parts, having a fast response, and being able to measure various gas mixtures, and has become a research hotspot in recent years.

[0003] A search revealed that Chinese patent CN213688510U discloses an ultrasonic gas meter sensor. This device, by configuring the area of ​​the first part to account for at least 90% of the total area of ​​the sidewall covered by the sound-absorbing layer, can minimize the gap between the sound-absorbing layer and the matching layer, expel air from the measurement, and greatly improve the stability of the sensor in the entire temperature range (-35 to 60 degrees Celsius).

[0004] The aforementioned device, by covering the sound-absorbing layer outside the matching layer, exposes the sound-absorbing layer to the air, increasing its aging rate. After aging, this not only affects the device's sealing performance but also leads to a decrease in the signal-to-noise ratio. Therefore, we propose an ultrasonic gas sensor. Utility Model Content

[0005] 1. Technical problems to be solved

[0006] The purpose of this application is to provide an ultrasonic gas sensor to solve the problems mentioned in the background art.

[0007] 2. Technical Solution

[0008] This application is achieved through the following technical solution:

[0009] An ultrasonic gas sensor includes a rigid housing arranged in a ring shape. A first matching layer is connected to the lower part of the rigid housing. The first matching layer has a protrusion inserted into the middle of the rigid housing. A cavity is formed in the protrusion. A circuit board, a piezoelectric ceramic, and an acoustic damping layer are fixed in the cavity. The piezoelectric ceramic is adhered to the first matching layer. The circuit board is electrically connected to the piezoelectric ceramic. A flexible rubber sleeve is provided on the outer side of the rigid housing. The flexible rubber sleeve cooperates with the first matching layer to completely wrap the rigid housing. A wire is electrically connected to the circuit board and passes through the flexible rubber sleeve.

[0010] As an optional solution to the technical solution in this application, a flexible silicone sealant is provided between the rigid shell and the flexible rubber sleeve, and on the upper and lower end faces of the rigid shell.

[0011] As an optional solution to the technical solution in this application, the first matching layer is formed by mixing epoxy resin with glass microspheres with a particle size of 20-110μm and then curing it.

[0012] As an optional solution to the technical solution of this application, the piezoelectric ceramic is adhered to the first matching layer through a second matching layer, the second matching layer being composed of a flexible epoxy resin doped with damping powder.

[0013] As an optional solution to the technical solution in this application, the acoustic damping layer is filled between the circuit board and the piezoelectric ceramic.

[0014] As an optional solution to the technical solution of this application, the opening of the flexible rubber sleeve is provided with an inwardly protruding annular protrusion, which extends to the space between the rigid outer shell and the first matching layer.

[0015] As an optional solution to the technical solution in this application, the connection between the wire and the flexible rubber sleeve is sealed with epoxy resin.

[0016] 3. Beneficial effects

[0017] Compared with the prior art, the beneficial effects of this application are:

[0018] 1) By placing the acoustic damping layer inside the cavity, this application can effectively reduce the aging rate of the acoustic damping layer and extend the service life of the device.

[0019] 2) This application protects the structure of the first matching layer by setting a rigid shell between the flexible rubber sleeve and the first matching layer, forming a rigidly coupled and elastically buffered mechanical system to ensure stable acoustic performance.

[0020] 3) By extending the first matching layer to below the rigid shell, this application allows the first matching layer to contact the gas more directly, reducing the loss of sound waves during propagation and improving sensitivity; the first matching layer located below the rigid shell can allow for better thermal expansion compensation and reduce structural stress caused by temperature changes. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of an ultrasonic gas sensor.

[0022] In the figure: 1. Rigid shell; 2. First matching layer; 201. Protrusion; 202. Cavity; 3. Circuit board; 4. Piezoelectric ceramic; 5. Flexible rubber sleeve; 501. Annular protrusion; 6. Wire; 7. Second matching layer; 8. Acoustic damping layer. Detailed Implementation

[0023] The technical solution of this application will now be clearly and completely described in conjunction with the accompanying drawings.

[0024] Please see Figure 1 This application provides an ultrasonic gas sensor, including a rigid housing 1 arranged in a ring shape. A first matching layer 2 is connected to the lower part of the rigid housing 1. A protrusion 201 is provided on the first matching layer 2 and inserted into the middle of the rigid housing 1. A cavity 202 is opened on the protrusion 201. A circuit board 3, a piezoelectric ceramic 4 and an acoustic damping layer 8 are fixed in the cavity 202. The piezoelectric ceramic 4 is attached to the first matching layer 2. The circuit board 3 and the piezoelectric ceramic 4 are electrically connected. A flexible rubber sleeve 5 is provided on the outside of the rigid housing 1. The flexible rubber sleeve 5 cooperates with the first matching layer 2 to completely wrap the rigid housing 1. A wire 6 is electrically connected to the circuit board 3 and passes through the flexible rubber sleeve 5.

[0025] In this design, the rigid housing 1 is made of stainless steel to protect the internal structure; the flexible rubber sleeve 5, which is fitted on the outside of the rigid housing 1, is used to increase the sealing performance of the device; by placing the acoustic damping layer 8 inside the cavity 202, the acoustic damping layer 8 can be prevented from being exposed to the air, which would lead to accelerated aging. At the same time, it can absorb the acoustic energy propagating upward from the piezoelectric ceramic 4 to shorten the pulse width and increase the signal-to-noise ratio.

[0026] In a preferred embodiment of this application, a flexible silicone sealant is provided between the rigid outer shell 1 and the flexible rubber sleeve 5, and on both the upper and lower end faces of the rigid outer shell 1. External sound waves can be transmitted almost without damage to the first matching layer 2 through the flexible rubber sleeve 5, the flexible silicone sealant, and the rigid outer shell 1, and then transmitted from the first matching layer 2 to the piezoelectric ceramic 4. Preferably, the piezoelectric ceramic 4 has a circular sheet structure and is chamfered at the edges.

[0027] As a preferred embodiment of this application, the first matching layer 2 is formed by mixing epoxy resin with glass microspheres with a particle size of 20-110μm and then curing it to achieve better impedance matching and a wider bandwidth, thereby improving sensitivity and measurement stability; the piezoelectric ceramic 4 is adhered to the first matching layer 2 through the second matching layer 7, which is composed of flexible epoxy resin doped with damping powder, to suppress the lateral vibration and aftershock of the piezoelectric ceramic 4 and improve signal clarity.

[0028] As a preferred embodiment of this application, the acoustic damping layer 8 is filled between the circuit board 3 and the piezoelectric ceramic 4.

[0029] As a preferred embodiment of this application, the opening of the flexible rubber sleeve 5 is provided with an inwardly protruding annular protrusion 501, which extends between the rigid outer shell 1 and the first matching layer 2 to increase the reliability of the connection between the flexible rubber sleeve 5 and the rigid outer shell 1; the connection between the wire 6 and the flexible rubber sleeve 5 is sealed with epoxy resin to increase the sealing performance of the connection between the wire 6 and the flexible rubber sleeve 5.

[0030] This ultrasonic gas sensor features an integrated transceiver design, achieving high-efficiency signal transmission and reception with stable support at a core operating point resonant frequency of 220kHz±5%. The sensor's electromechanical coupling coefficient Keff ≥0.45 and output sensitivity ≥20 mV work synergistically to significantly improve energy utilization and signal integrity. It can directly convert ppm-level gas concentration changes into millivolt-level voltage signals, with a detection limit as low as 10 ppm (taking methane as an example), significantly superior to existing similar products with a detection limit of 50–100 ppm.

[0031] The electromechanical coupling coefficient Keff is ≥0.45, and the bidirectional conversion loss between mechanical energy and electrical energy is <5%. Combined with the optimized capacitor design of 1700pF±15%, the driving voltage can be reduced to 3.3 V, and the power consumption per measurement is <0.5 mJ.

Claims

1. An ultrasonic gas sensor, characterized in that: The device includes a rigid outer shell (1) arranged in a ring shape. A first matching layer (2) is connected to the lower part of the rigid outer shell (1). A protrusion (201) is provided on the first matching layer (2). The protrusion (201) is inserted into the middle of the rigid outer shell (1). A cavity (202) is opened on the protrusion (201). A circuit board (3), a piezoelectric ceramic (4) and an acoustic damping layer (8) are fixed in the cavity (202). The piezoelectric ceramic (4) is pasted on the first matching layer (2). The circuit board (3) is electrically connected to the piezoelectric ceramic (4). A flexible rubber sleeve (5) is provided on the outside of the rigid outer shell (1). The flexible rubber sleeve (5) cooperates with the first matching layer (2) to completely wrap the rigid outer shell (1). A wire (6) is electrically connected on the circuit board (3). The wire (6) passes through the flexible rubber sleeve (5).

2. The ultrasonic gas sensor according to claim 1, characterized in that: Flexible silicone sealant is provided between the rigid shell (1) and the flexible rubber sleeve (5), and on the upper and lower end faces of the rigid shell (1).

3. An ultrasonic gas sensor according to claim 1, characterized in that: The first matching layer (2) is formed by mixing epoxy resin with glass microspheres with a particle size of 20-110μm and then curing it.

4. An ultrasonic gas sensor according to claim 1, characterized in that: The piezoelectric ceramic (4) is adhered to the first matching layer (2) through the second matching layer (7), which is composed of a flexible epoxy resin doped with damping powder.

5. An ultrasonic gas sensor according to claim 1, characterized in that: The acoustic damping layer (8) is filled between the circuit board (3) and the piezoelectric ceramic (4).

6. An ultrasonic gas sensor according to claim 1, characterized in that: The flexible rubber sleeve (5) has an inwardly protruding annular protrusion (501) at the opening, and the annular protrusion (501) extends between the rigid outer shell (1) and the first matching layer (2).

7. An ultrasonic gas sensor according to claim 1, characterized in that: The connection between the wire (6) and the flexible rubber sleeve (5) is sealed with epoxy resin.

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