MEMS pressure sensor

Abstract

The invention relates to the technical field of micro-electro-mechanical system sensors, in particular to an MEMS pressure sensor which comprises a shell, an induction diaphragm and an ASIC signal processing unit, an induction mounting cavity and a signal processing cavity are formed in the shell, an air inlet is formed in the lower end face of the shell, a detection channel and a buffer cavity are formed in the shell, and the detection channel is communicated with the signal processing cavity. The buffer cavity is designed to be gradually expanded from bottom to top; pulse airflow firstly enters the detection channel through the air inlet, and direct disordered impact of the airflow is avoided; then the airflow enters the buffer cavity, the airflow speed and the pressure peak value are gradually reduced and the pulse energy is dispersed by utilizing the characteristic that the cross sectional area of the cavity is gradually increased, and the originally concentrated strong impact force is converted into gentle pressure transmission, so that the abrasion and damage risks caused by the fact that the sensing diaphragm frequently bears the violent pressure are reduced; the structure stability and the sensing sensitivity of the sensing diaphragm can be maintained, and the accuracy of pressure detection and the reliability of long-term work of the MEMS pressure sensor can be guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-electromechanical system sensors, and in particular to a MEMS pressure sensor. Background Art

[0002] A microelectromechanical system (MEMS) pressure sensor is a miniature pressure detection device based on micromachining technology. Its core lies in the use of micromachining technology of semiconductor materials such as silicon to integrate miniature sensitive structures (such as films, beams, cavities, etc.) and signal processing circuits on the chip. When external pressure acts on these sensitive structures, the structure will produce tiny deformations. This deformation is converted into electrical signals through physical principles such as piezoresistive effect, capacitive effect or piezoelectric effect, thereby achieving accurate measurement of pressure. Compared with traditional mechanical pressure sensors, MEMS pressure sensors stand out with their significant advantages such as small size, light weight, low power consumption, low cost and mass production. They are also compatible with integrated circuits and can be easily integrated into various electronic systems. Due to these irreplaceable advantages of MEMS sensors, traditional automotive pressure sensors are gradually being replaced by them.

[0003] However, existing pressure sensors are usually installed and fixed through rigid contact between electronic devices and the shell. During the use of automobiles, since they are often in outdoor environments, they are easily affected by climatic factors such as temperature, humidity, and wind speed, all of which may affect the measurement accuracy of the pressure sensor. In addition, the automobile may also be subjected to external forces such as collisions during operation. The installation method of traditional pressure sensors makes it easy for electronic devices to fail in connection with the shell due to deformation or force after experiencing thermal expansion and contraction or external force collisions, or due to the rigid contact between the electronic devices and the shell, they are squeezed by the shell and damaged after deformation or force, thereby affecting the detection accuracy and reducing the service life.

[0004] In order to solve the above problems, the prior art has proposed some solutions. For example, the invention patent with application number CN202311099506.8 discloses a MEMS automobile pressure sensor. The invention fixes the PCB board by abutting the connector with the PCB board, limiting the PCB board on the first path by the connector and the base, and limiting the PCB board on the second path by the inner circumference of the first mounting cavity. Since the connector is provided with a receiving cavity, the second mounting cavity is connected to the first mounting cavity, thereby reducing the rigid contact area on both sides of the PCB board and avoiding the influence of the environment or external force on the base. or the extrusion of the connector, thereby improving the service life of the PCB board. In addition, the electronic module is located in the first mounting cavity. After the connector is inserted into the first mounting cavity, the electronic module is located in the accommodating cavity, and the PCB board covers the opening of the accommodating cavity, so that the electronic module is in a closed space, which not only avoids rigid contact with the connector and the base, but also reduces the influence of changes in external environmental temperature or humidity; the sensing module is located in the second mounting cavity and is fixed by connection with the PCB board, thereby avoiding rigid contact between the sensing module and the base, reducing the probability of extrusion or collision between the sensing module and the base, and ensuring the detection accuracy of the sensing module.

[0005] Although the above solution reduces rigid contact and improves stability through structural optimization, the application of MEMS pressure sensors in automotive engine intake systems still faces challenges. Due to the motion characteristics of the piston inside the engine cylinder, the airflow in the intake manifold is pulsating. This pulsating airflow exerts a continuous and strong impact on the sensing diaphragm of the MEMS pressure sensor. Long-term exposure to this impact environment can easily cause the sensing diaphragm structure to deform and crack, resulting in a decrease in its sensitivity. Ultimately, the accuracy of the data collected by the MEMS pressure sensor is significantly reduced, seriously affecting the engine control system's ability to accurately determine and control the intake volume. Summary of the Invention

[0006] The purpose of the present invention is to provide a MEMS pressure sensor to solve the problem that pulsed airflow produces continuous and strong impact force on the sensing diaphragm of the MEMS pressure sensor, which easily causes deformation and rupture of the sensing diaphragm structure, thereby causing its sensitivity to decrease, and ultimately greatly reducing the accuracy of data collected by the MEMS pressure sensor, seriously affecting the engine control system's accurate judgment and regulation of the intake volume.

[0007] To achieve the above object, the present invention provides the following technical solutions: The utility model provides a kind of MEMS pressure sensor, including shell, sensing diaphragm and ASIC signal processing unit, sensing installation cavity and signal processing cavity are equipped in the shell, sensing installation cavity is located signal processing cavity downside, sensing diaphragm and ASIC signal processing unit are installed in sensing installation cavity and signal processing cavity respectively, the lower end surface of the shell is equipped with air inlet, detection channel and buffer cavity are equipped in the shell, the upper and lower ends of the detection channel are communicated with buffer cavity and air inlet respectively, the upper end of buffer cavity is communicated with sensing installation cavity, and the buffer cavity is gradually expanding design from bottom to top;Pulse airflow first enters detection channel via air inlet, channel plays primary rectification and guiding role to airflow, avoid airflow direct disorder impact;Subsequently, airflow enters gradually expanding design from bottom to top buffer cavity, according to the principle of fluid mechanics, utilize the characteristics that cavity cross-sectional area gradually increases, gradually reduce airflow velocity and pressure peak value, disperse pulse energy, convert originally concentrated strong impact force into gentle pressure transmission, so as to weaken the sustained impact of pulse airflow to sensing diaphragm, so as to reduce the wear and damage risk of sensing diaphragm due to frequent bearing intense pressure, help to maintain the structural stability and sensing sensitivity of sensing diaphragm, guarantee the accuracy of MEMS pressure sensor to pressure detection and the reliability of long-term work.

[0008] Preferably, the lower end inner wall of the buffer cavity is circumferentially distributed with a plurality of guide vanes, the plurality of guide vanes are in arc sheet structure, the concave surface of the plurality of guide vanes faces the air inlet direction, and the edges of the plurality of guide vanes are rounded; by circumferentially distributing a plurality of guide vanes in arc sheet structure, concave surface facing the air inlet and rounded edges at the lower end inner wall of the buffer cavity, when pulse gas enters the buffer cavity through the air inlet and the detection channel, the plurality of guide vanes can divide the entering pulse airflow into multiple substreams, and the arc concave surface of the plurality of guide vanes guides the smooth flow of the airflow. At the same time, the rounded edges of the plurality of guide vanes avoid turbulent flow caused by airflow impact, thereby avoiding the local concentrated impact of pulse airflow on the sensing diaphragm, reducing the deformation and rupture risk of the sensing diaphragm caused by stress concentration, and ensuring the sensing sensitivity, detection accuracy and long-term working structural reliability of the MEMS pressure sensor.

[0009] Preferably, a rectifying net is coaxially installed in the shell, and the rectifying net is cylindrical. The rectifying net is located between the buffer cavity and the sensing diaphragm, and the diameter of the rectifying net is larger than the diameter of the sensing diaphragm. A plurality of mesh holes are provided on the rectifying net, and the plurality of mesh holes are arranged in a regular hexagonal array, and the plurality of mesh holes are parallel to the axis of the shell; by coaxially installing the cylindrical rectifying net between the buffer cavity and the sensing diaphragm, full range coverage is achieved by utilizing its diameter larger than the sensing diaphragm, and the mesh hole design arranged in a regular hexagonal array and parallel to the axis of the shell, when the pulse gas flows through the plurality of mesh holes of the rectifying net, the rectifying net can further rectify the airflow after buffering and guiding, and comb the turbulent airflow into uniform laminar flow, while intercepting tiny particle pollutants in the airflow, thereby avoiding the problems of local force on the sensing diaphragm caused by uneven airflow, and the influence of pollutant adhesion on sensing accuracy, thereby ensuring the accuracy of detection data of the MEMS pressure sensor, the cleanliness of the sensing diaphragm and the long-term working stability.

[0010] Preferably, an annular guide cavity is provided between the rectifier mesh and the buffer cavity, and the inner diameter of the annular guide cavity gradually decreases from the buffer cavity toward the rectifier mesh, and the contraction angle is 5°-8°; the inner wall of the annular guide cavity adopts the roughness Ra≤0.1μm after machining, and the length of the annular guide cavity is 1 / 3-1 / 2 of the total length of the buffer cavity; by providing an annular guide cavity between the rectifier mesh and the buffer cavity, the inner diameter of which gradually decreases from the buffer cavity toward the rectifier mesh at a contraction angle of 5°-8°, the inner wall roughness Ra≤0.1μm and the length is 1 / 3-1 / 2 of the total length of the buffer cavity, after the pulse gas flows through multiple guide blades, the annular guide cavity can guide the airflow processed by the buffer cavity to smoothly transition to the rectifier mesh, reduce the turbulent disturbance and pressure loss of the airflow in the transition area, avoid the influence of airflow turbulence on the rectification effect and the distortion of pressure signal transmission, and ensure the dynamic response speed, detection accuracy stability and accuracy of airflow pressure transmission of the MEMS pressure sensor.

[0011] Preferably, the sensing diaphragm is made of silicon-based material, and a stepped flexible connecting ring is provided between the sensing diaphragm and the inner wall of the sensing installation cavity. The connecting ring is composed of a three-layer composite structure of an inner layer, a middle layer and an outer layer. The inner layer, the middle layer and the outer layer of the connecting ring are respectively made of nickel-titanium alloy, polyimide and beryllium copper. The thickness of the inner layer and the outer layer of the connecting ring are equal, and the thickness of the middle layer of the connecting ring is 1 / 2 of the thickness of the inner layer and the outer layer. By providing a stepped flexible connecting ring made of nickel-titanium alloy, polyimide and beryllium copper between the silicon-based sensing diaphragm and the inner wall of the sensing installation cavity, the connecting ring is provided with a stepped flexible connecting ring. The three-layer composite stepped flexible connecting ring is composed of an inner layer and an outer layer of equal thickness, and a middle layer of half the thickness. By utilizing the gradient matching of the thermal expansion coefficients of different materials and structural flexibility, when the MEMS pressure sensor is subjected to external temperature changes, the connecting ring can effectively alleviate the problem of sensing diaphragm extrusion caused by the difference in material expansion coefficients when the temperature changes, avoid the deformation and rupture of the sensing diaphragm and the resulting decrease in detection accuracy, and ensure the measurement accuracy, structural stability and long-term working reliability of the MEMS pressure sensor in a wide temperature range.

[0012] Preferably, an annular groove is processed on the inner side of the air inlet of the shell, and an oleophobic and hydrophobic membrane is installed on the shell, and the edge of the oleophobic and hydrophobic membrane is embedded in the annular groove. The oleophobic and hydrophobic membrane is located at the lower end of the air inlet, and the plane of the oleophobic and hydrophobic membrane is parallel to the end face of the air inlet, and the surface of the oleophobic and hydrophobic membrane is kept in a taut state; by installing the oleophobic and hydrophobic membrane located at the lower end of the air inlet, with the plane parallel to the end face of the air inlet and the surface taut in the annular groove on the inner side of the air inlet of the shell, and utilizing the oleophobic and hydrophobic properties of the membrane and the edge embedding design, when the pulse gas passes through the oleophobic and hydrophobic membrane, it can effectively block liquid pollutants such as oil smoke and water vapor in the intake air and tiny impurities from penetrating from the edge, avoiding pollutants from adhering to the surface of the sensing diaphragm or entering the interior of the sensor to affect the sensing accuracy and cause component corrosion, thereby ensuring the detection sensitivity, measurement accuracy, long-term working reliability and cleanliness of the MEMS pressure sensor.

[0013] Preferably, a plurality of buffer grooves are provided on the outer wall of the ASIC signal processing unit, and a buffer ring is provided in each of the plurality of buffer grooves, and the outer walls of the plurality of buffer rings are connected to the inner wall of the signal processing cavity; by arranging the buffer rings in the plurality of buffer grooves on the outer wall of the ASIC signal processing unit, and connecting the outer walls of the buffer rings to the inner wall of the signal processing cavity, and utilizing the positioning effect of the buffer grooves and the elastic buffering performance of the buffer rings, when the MEMS pressure sensor is affected by external vibration, the buffer grooves and the buffer rings can effectively absorb the impact of the external vibration on the ASIC signal processing unit, thereby avoiding poor component contact, structural damage and signal processing abnormalities caused by vibration, thereby ensuring the stability of the MEMS pressure sensor signal processing, the structural integrity of the electronic components and the accuracy of the data output.

[0014] Preferably, a mounting cap is threadedly connected to the upper end of the shell, a rotating groove is coaxially provided on the mounting cap, a sealing plate is coaxially connected to the rotating groove, and a wiring terminal is provided on the ASIC signal processing unit, and the wiring terminal extends to the upper side of the sealing plate; the mounting cap is threadedly connected to the upper end face of the shell, and the sealing plate is coaxially connected to the mounting cap in the rotating groove, and the wiring terminal of the ASIC signal processing unit is extended to the upper side of the sealing plate. The mounting cap is firmly assembled and conveniently disassembled through the threaded connection, and the rotating characteristics of the sealing plate are used to avoid twisting and stress of the wires during wiring, while ensuring the sealing of the signal processing cavity, avoiding signal interference or component damage caused by loose installation, wiring damage and intrusion of external contaminants, and ensuring the installation reliability, wiring safety, signal transmission stability and internal environment sealing of the MEMS pressure sensor.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention provides a detection channel and a buffer cavity in the shell. The pulsed airflow first enters the detection channel through the air inlet to avoid direct and disordered impact of the airflow. The airflow then enters the buffer cavity and gradually reduces the airflow velocity and pressure peak by utilizing the characteristic of the gradually increasing cross-sectional area of ​​the cavity, thereby dispersing the pulse energy and converting the originally concentrated strong impact force into a gentle pressure transmission, thereby reducing the risk of wear and damage to the sensing diaphragm caused by frequent exposure to severe pressure, helping to maintain the structural stability and sensing sensitivity of the sensing diaphragm, and ensuring the accuracy of pressure detection and the long-term reliability of the MEMS pressure sensor.

[0016] 2. The present invention has a plurality of guide blades evenly distributed on the circumference of the inner wall at the lower end of the buffer cavity. The plurality of guide blades are evenly distributed on the circumference of the inner wall at the lower end of the buffer cavity and have an arc-shaped thin plate structure, with the concave surface facing the air inlet and the edges being rounded. The pulsed airflow entering the air inlet can be divided into multiple tributaries. The arc-shaped concave surface is used to guide the airflow to flow smoothly, and the rounded corners are used to avoid turbulence caused by the impact of the airflow, thereby avoiding the local concentrated impact of the pulsed airflow on the sensing diaphragm, reducing the risk of deformation and rupture of the sensing diaphragm due to stress concentration, and ensuring the sensing sensitivity, detection accuracy and structural reliability of the MEMS pressure sensor for long-term operation.

[0017] 3. The present invention coaxially installs a rectifier mesh in the shell, and coaxially installs a cylindrical rectifier mesh between the buffer cavity and the sensing diaphragm. The rectifier mesh is larger than the diameter of the sensing diaphragm to achieve full range coverage. The mesh design is arranged in a regular hexagonal array and parallel to the axis of the shell. It can further rectify the airflow after buffering and guiding, comb the turbulent airflow into uniform laminar flow, and at the same time intercept tiny particle pollutants in the airflow, avoiding problems such as local force on the sensing diaphragm caused by uneven airflow and the influence of pollutant adhesion on sensing accuracy, thereby ensuring the accuracy of detection data of the MEMS pressure sensor, the cleanliness of the sensing diaphragm and the long-term working stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the structure of the MEMS pressure sensor of the present invention; Figure 2 Schematic diagram of the internal structure of the MEMS pressure sensor of the present invention; Figure 3 For the present invention Figure 2 Cross-sectional view of the shell at AA; Figure 4 For the present invention Figure 3 Full cross-sectional view of Figure 5 Schematic diagram of gas flow inside the MEMS pressure sensor of the present invention; Figure 6 For the present invention Figure 4 Cross-sectional view at the middle BB; Figure 7 This is an exploded view of the MEMS pressure sensor of the present invention.

[0019] In the figure: 1. Shell; 101. Sensor mounting cavity; 102. Signal processing cavity; 103. Air inlet; 104. Annular groove; 105. Oleophobic and hydrophobic membrane; 2. Sensor diaphragm; 3. ASIC signal processing unit; 4. Detection channel; 5. Buffer cavity; 501. Guide vane; 6. Rectifier mesh; 601. Mesh; 7. Annular guide cavity; 8. Connecting ring; 801. Inner layer; 802. Middle layer; 803. Outer layer; 901. Buffer groove; 902. Buffer ring; 903. Mounting cap; 904. Rotating groove; 905. Sealing plate; 906. Terminal. DETAILED DESCRIPTION

[0020] See also Figures 1 to 7 The present invention provides a MEMS pressure sensor, the technical solution is as follows: A MEMS pressure sensor, see Figures 1 to 7The utility model relates to a kind of sensor, including shell 1, sensing diaphragm 2 and ASIC signal processing unit 3, sensing installation cavity 101 and signal processing cavity 102 are equipped in shell 1, sensing installation cavity 101 is located in the downside of signal processing cavity 102, sensing diaphragm 2 and ASIC signal processing unit 3 are installed in sensing installation cavity 101 and signal processing cavity 102 respectively, multiple buffer grooves 901 are set on the outer side wall of ASIC signal processing unit 3, multiple buffer rings 902 are equipped in multiple buffer grooves 901, the outer side wall of multiple buffer rings 902 is connected with the inner side wall of signal processing cavity 102, the upper end of shell 1 is threadedly connected with installation cap 903, coaxially rotating groove 904 is set on installation cap 903, sealing plate 905 is coaxially rotatably connected in rotating groove 904, wiring end 906 is equipped on ASIC signal processing unit 3, wiring end 906 extends to the upside of sealing plate 905, air inlet 103 is set on the lower end surface of shell 1, annular groove 104 is processed in the inner side of air inlet 103 of shell 1, oil-repellent and water-repellent membrane 105 is installed on shell 1, the edge of oil-repellent and water-repellent membrane 105 is embedded in annular groove 104, oil-repellent and water-repellent membrane 105 is located in the lowermost end of air inlet 103, the plane of oil-repellent and water-repellent membrane 105 is parallel with the end surface of air inlet 103, and the surface of oil-repellent and water-repellent membrane 105 keeps taut state, detection channel 4 and buffer cavity 5 are set in shell 1, the upper and lower ends of detection channel 4 are communicated with buffer cavity 5 and air inlet 103 respectively, the upper end of buffer cavity 5 is communicated with sensing installation cavity 101, and buffer cavity 5 is designed gradually expanding from down to up, multiple guide vanes 501 are uniformly distributed on the inner wall of the lower end of buffer cavity 5, multiple guide vanes 501 are arc thin plate structure, the concave surface of multiple guide vanes 501 faces the direction of air inlet 103, and the edge of multiple guide vanes 501 is all rounded, flow net 6 is coaxially installed in shell 1, flow net 6 is cylindrical, flow net 6 is located between buffer cavity 5 and sensing diaphragm 2, the diameter of flow net 6 is greater than the diameter of sensing diaphragm 2, multiple mesh holes 601 are equipped on flow net 6, multiple mesh holes 601 are arranged in regular hexagon array, multiple mesh holes 601 are all parallel with the axis of shell 1, annular guide cavity 7 is arranged between flow net 6 and buffer cavity 5, the inner diameter of annular guide cavity 7 gradually reduces from buffer cavity 5 to flow net 6, and the shrinkage angle is 6 °;The roughness Ra=0.1 μm after mechanical processing is used to the inner wall of annular guide cavity 7, and the length of annular guide cavity 7 is 1 / 2 of the total length of buffer cavity 5, sensing diaphragm 2 is made of silicon-based material, and there is stepped flexible connecting ring 8 between sensing diaphragm 2 and the inner wall of sensing installation cavity 101, connecting ring 8 is composed of three-layer composite structure of inner layer 801, middle layer 802 and outer layer 803, the inner layer 801, middle layer 802 and outer layer 803 of connecting ring 8 are made of nickel-titanium alloy, polyimide and beryllium copper respectively, the thickness of the inner layer 801 and the outer layer 803 of connecting ring 8 is equal, and the thickness of middle layer 802 of connecting ring 8 is 1 / 2 of the thickness of inner layer 801 and outer layer 803.

[0021] While working, see Figures 1 to 7 The airflow of the automobile intake system first enters through the air inlet 103 at the lower end of the shell 1 and contacts the oleophobic and hydrophobic membrane 105 located at the lower end of the air inlet 103; the oleophobic and hydrophobic membrane 105 is sealed by a tightened surface and an edge embedded in the annular groove 104. The oleophobic and hydrophobic membrane 105 uses the oleophobic and hydrophobic properties to make liquid pollutants form liquid droplets and roll down, and the solid particles are physically blocked, intercepting the oil smoke, water vapor and solid particles ≥0.1μm in the airflow to prevent pollutants from entering the subsequent core structure; the filtered airflow flows through the detection channel 4 and is transmitted vertically upward and enters the lower end of the buffer cavity 5; the airflow enters the gradually expanding buffer cavity 5, and uses the characteristics of increased cavity volume to initially reduce the airflow velocity and weaken the pulse pressure peak, thereby reducing the risk of wear and damage to the sensing diaphragm 2 due to frequent exposure to severe pressure.

[0022] Furthermore, the arc-shaped guide blade 501 with the concave surface of the inner wall at the lower end of the buffer chamber 5 facing the air inlet 103 divides the airflow into multiple branches. The arc-shaped concave surface of the guide blade 501 guides the airflow to flow smoothly upward along the inner wall of the buffer chamber 5. The rounded edge of the guide blade 501 avoids turbulence when the airflow hits the guide blade 501, further dispersing the pulse energy. At this time, the airflow processed by the guide blade 501 enters the annular guide chamber 7 with a contraction angle of 6° and a length of 1 / 2 of the total length of the buffer chamber 5. Through the structure of the gradually contracting inner diameter of the annular guide chamber 7, the airflow is discharged. The airflow is forced to converge toward the center, and the low roughness design of the inner wall of the annular guide cavity 7 with Ra=0.1μm reduces the friction disturbance between the airflow and the wall of the annular guide cavity 7, so that the airflow transitions from "dispersed flow" to "quasi-laminar flow"; the airflow finally enters the cylindrical rectifying mesh 6 with a diameter larger than that of the sensing diaphragm 2. At this time, the mesh 601 with a regular hexagonal array and parallel to the axis of the shell 1 combs the airflow. Through the diversion and confluence effect of the mesh 601, the residual turbulence is converted into a uniform laminar flow parallel to the axis of the shell 1, and completely covers the sensing area of ​​the sensing diaphragm 2.

[0023] The rectified laminar flow acts perpendicularly on the silicon-based sensing diaphragm 2, and the sensing diaphragm 2 produces a slight deformation under the action of pressure, and the deformation is linearly related to the pressure; since the sensing diaphragm 2 is fixed to the inner wall of the sensing installation cavity 101 by a stepped flexible connecting ring 8, the nickel-titanium alloy inner layer 801, the polyimide middle layer 802, and the beryllium copper outer layer 803 of the connecting ring 8 are matched with the inner layer 801 to be equal to the thickness of the outer layer 803 through material elasticity, and the middle layer 802 is 1 / 2 the thickness of the inner and outer layers 803, which alleviates the thermal expansion difference stress between silicon and the metal shell 1 caused by temperature changes, avoids additional deformation of the sensing diaphragm 2 due to stress extrusion, and ensures that the deformation is only determined by the airflow pressure; at this time, the sensing diaphragm 2 converts the deformation into an electrical signal through a change in capacitance or resistance, and transmits it to the signal processing cavity 102 through the lead.

[0024] Furthermore, after the electrical signal enters the ASIC signal processing unit 3, the ASIC signal processing unit 3 performs amplification, filtering, temperature compensation and other processing on the original signal to eliminate interference such as residual airflow turbulence and circuit thermal noise; since a buffer ring 902 is provided in the buffer groove 901 on the outer wall of the ASIC signal processing unit 3, and the buffer ring 902 is connected to the inner wall of the signal processing chamber 102, it can absorb external impact vibrations such as engine vibration on the ASIC signal processing unit 3, thereby avoiding loose circuit connections or component damage; the processed signal is output through the terminal 906 extending to the upper side of the sealing plate 905, and the sealing plate 905 can rotate with the rotating groove 904 of the mounting cap 903 to avoid twisting and stress of the wires during wiring, thereby ensuring stable signal transmission and sealing protection of the ASIC signal processing unit 3.

[0025] A specific embodiment of the present invention has been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the embodiment described above. For those skilled in the art, various changes, modifications, substitutions, and variations to these embodiments without departing from the principles and ideas of the present invention should still fall within the scope of protection of the present invention.

Claims

1. A MEMS pressure sensor, characterized in that: The invention comprises a shell (1), a sensing diaphragm (2) and an ASIC signal processing unit (3), wherein the shell (1) is provided with a sensing installation cavity (101) and a signal processing cavity (102), the sensing installation cavity (101) is located at the lower side of the signal processing cavity (102), the sensing diaphragm (2) and the ASIC signal processing unit (3) are respectively installed in the sensing installation cavity (101) and the signal processing cavity (102), an air inlet (103) is provided on the lower end surface of the shell (1), a detection channel (4) and a buffer cavity (5) are provided in the shell (1), the upper and lower ends of the detection channel (4) are respectively connected to the buffer cavity (5) and the air inlet (103), the upper end of the buffer cavity (5) is connected to the sensing installation cavity (101), and the buffer cavity (5) is designed to be gradually expanded from bottom to top.

2. The MEMS pressure sensor according to claim 1, wherein: A plurality of guide blades (501) are evenly distributed on the circumference of the inner wall of the lower end of the buffer chamber (5), and the plurality of guide blades (501) are in the form of an arc-shaped thin plate structure. The concave surfaces of the plurality of guide blades (501) face the direction of the air inlet (103), and the edges of the plurality of guide blades (501) are all rounded.

3. The MEMS pressure sensor according to claim 2, wherein: A rectifying net (6) is coaxially mounted in the housing (1), the rectifying net (6) being cylindrical and located between the buffer cavity (5) and the sensing diaphragm (2). The diameter of the rectifying net (6) is larger than the diameter of the sensing diaphragm (2). The rectifying net (6) is provided with a plurality of mesh holes (601), the plurality of mesh holes (601) being arranged in a regular hexagonal array, and the plurality of mesh holes (601) are all parallel to the axis of the housing (1).

4. The MEMS pressure sensor according to claim 3, wherein: An annular guide cavity (7) is provided between the rectifying net (6) and the buffer cavity (5); the inner diameter of the annular guide cavity (7) gradually decreases from the buffer cavity (5) toward the rectifying net (6), with a contraction angle of 5°-8°; the inner wall of the annular guide cavity (7) has a roughness Ra≤0.1μm after machining, and the length of the annular guide cavity (7) is 1 / 3-1 / 2 of the total length of the buffer cavity (5).

5. The MEMS pressure sensor according to claim 4, characterized in that: The sensing diaphragm (2) is made of a silicon-based material. A stepped flexible connecting ring (8) is provided between the sensing diaphragm (2) and the inner wall of the sensing mounting cavity (101). The connecting ring (8) is composed of a three-layer composite structure of an inner layer (801), a middle layer (802) and an outer layer (803). The inner layer (801), the middle layer (802) and the outer layer (803) of the connecting ring (8) are respectively made of nickel-titanium alloy, polyimide and beryllium copper. The thickness of the inner layer (801) and the outer layer (803) of the connecting ring (8) are equal, and the thickness of the middle layer (802) of the connecting ring (8) is 1 / 2 of the thickness of the inner layer (801) and the outer layer (803).

6. The MEMS pressure sensor according to claim 1, wherein: An annular groove (104) is machined on the inner side of the air inlet (103) of the shell (1), and an oleophobic and hydrophobic membrane (105) is installed on the shell (1), and the edge of the oleophobic and hydrophobic membrane (105) is embedded in the annular groove (104). The oleophobic and hydrophobic membrane (105) is located at the lower end of the air inlet (103), and the plane of the oleophobic and hydrophobic membrane (105) is parallel to the end face of the air inlet (103), and the surface of the oleophobic and hydrophobic membrane (105) is kept in a taut state.

7. The MEMS pressure sensor according to claim 1, wherein: A plurality of buffer grooves (901) are provided on the outer wall of the ASIC signal processing unit (3), a buffer ring (902) is provided in each of the plurality of buffer grooves (901), and the outer walls of the plurality of buffer rings (902) are connected to the inner wall of the signal processing cavity (102).

8. The MEMS pressure sensor according to claim 7, characterized in that: The upper end of the housing (1) is threadedly connected to a mounting cap (903), a rotation slot (904) is coaxially provided on the mounting cap (903), a sealing plate (905) is coaxially rotatably connected in the rotation slot (904), and a wiring terminal (906) is provided on the ASIC signal processing unit (3), and the wiring terminal (906) extends to the upper side of the sealing plate (905).

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