A MEMS pressure sensor

Abstract

The application relates to the technical field of micro-electro-mechanical system sensors, in particular to a MEMS pressure sensor which comprises a shell, a sensing diaphragm and an ASIC signal processing unit, the shell is internally provided with a sensing installation cavity and a signal processing cavity, 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 buffer cavity is designed in a gradually expanding mode from bottom to top; pulse airflow first enters the detection channel through the air inlet to avoid direct and disordered airflow impact; then the airflow enters the buffer cavity, the gradually increasing cross-sectional area of the cavity body is utilized to gradually reduce airflow speed and pressure peak value, disperse pulse energy, convert the originally concentrated strong impact force into gentle pressure transmission, thereby reducing the abrasion and damage risk of the sensing diaphragm caused by frequently bearing intense pressure, helping to maintain the structural stability and sensing sensitivity of the sensing diaphragm, and guaranteeing the accuracy of the MEMS pressure sensor in pressure detection and the reliability of long-term work.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of micro-electro-mechanical system sensor, in particular to a MEMS pressure sensor. BACKGROUND

[0002] Micro-electro-mechanical system (MEMS) pressure sensor is a kind of miniature pressure detection device based on micro-machining technology, its core is to use the micro-machining process of semiconductor materials such as silicon to integrate micro-sensitive structure (such as thin film, beam, cavity, etc.) and signal processing circuit on the chip, when the external pressure acts on these sensitive structures, the structure will produce micro deformation, the deformation is converted into electrical signal through piezoresistive effect, capacitive effect or piezoelectric effect, etc. Physical principle, so as to realize the accurate measurement of pressure, compared with traditional mechanical pressure sensor, MEMS pressure sensor is outstanding with its small size, light weight, low power consumption, low cost and batch production, and can be compatible with integrated circuit, easy to integrate into various electronic systems; Because of these irreplaceable advantages of MEMS sensor, traditional automotive pressure sensor is gradually replaced by it.

[0003] However, the existing pressure sensor is usually installed and fixed by the rigid contact of the electronic device and the shell, during the use of the automobile, due to often in outdoor environment, it is easy to be affected by temperature, humidity, wind speed and other climate factors, these factors may affect the measurement accuracy of the pressure sensor; In addition, the automobile may also suffer from collision and other external force during operation, the installation mode of the traditional pressure sensor makes the electronic device easy to be connected with the shell after experiencing thermal expansion and cold shrinkage or external force collision, or the electronic device is damaged due to the extrusion of the shell after deformation or stress due to the rigid contact of the electronic device and the shell, thereby affecting the detection accuracy and reducing the service life.

[0004] To solve the above problems, the prior art proposes some solutions, for example, the invention patent with application number CN202311099506.8 discloses a MEMS automobile pressure sensor. The invention realizes the fixation of the PCB board through the abutment of the connector with the PCB board, the limiting of the connector and the base on the first path to the PCB board, and the limiting of the inner circumferential surface of the first mounting cavity to the PCB board on the second path. Due to the accommodation cavity provided on the connector, the second mounting cavity is communicated with the first mounting cavity, thereby reducing the rigid contact area on both sides of the PCB board, avoiding the extrusion with the base or the connector under the influence of the environment or external force, and 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 accommodation cavity, and the PCB board covers the opening of the accommodation cavity, so that the electronic module is in a closed space, not only avoiding the rigid contact with the connector and the base, but also reducing the influence of the change of external environmental temperature or humidity. The sensing module is located in the second mounting cavity and is fixed through the connection with the PCB board, avoiding the rigid contact of the sensing module with the base, reducing the probability of extrusion or collision of the sensing module with the base, and ensuring the detection accuracy of the sensing module.

[0005] Although the above-mentioned scheme reduces the rigid contact and improves the stability through structural optimization, the application of the MEMS pressure sensor in the automobile engine intake system still faces challenges. Due to the movement characteristics of the piston inside the engine cylinder, the airflow in the intake manifold presents a pulse form. This pulse airflow will produce a continuous and strong impact force on the sensing diaphragm of the MEMS pressure sensor. In the long-term impact environment, the structure of the sensing diaphragm is prone to deformation, rupture, etc., resulting in a decrease in its sensitivity, and ultimately a significant reduction in the precision of data collected by the MEMS pressure sensor, which seriously affects the accurate judgment and regulation of the engine control system on the intake amount. SUMMARY

[0006] The purpose of the present application is to provide a MEMS pressure sensor to solve the problem that the pulse airflow produces a continuous and strong impact force on the sensing diaphragm of the MEMS pressure sensor, which easily leads to deformation, rupture, etc. of the structure of the sensing diaphragm, thereby causing a decrease in its sensitivity, and ultimately a significant reduction in the precision of data collected by the MEMS pressure sensor, which seriously affects the accurate judgment and regulation of the engine control system on the intake amount.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0008] 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.

[0009] 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.

[0010] Preferably, a rectifying net is coaxially installed in the shell, the rectifying net is cylindrical, the rectifying net is located between the buffer cavity and the sensing diaphragm, the diameter of the rectifying net is larger than the diameter of the sensing diaphragm, a plurality of mesh holes are arranged on the rectifying net, 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, the diameter of the rectifying net is larger than the diameter of the sensing diaphragm to achieve full coverage, the mesh holes arranged in a regular hexagonal array and parallel to the axis of the shell are designed, when the pulsed gas flows through the plurality of mesh holes of the rectifying net, the rectifying net can further rectify the airflow after buffering and flow guiding, comb the turbulent airflow into uniform laminar flow, and intercept the small particle pollutants in the airflow, thereby avoiding problems such as local stress of the sensing diaphragm, influence of pollutants on sensing accuracy, and the like caused by uneven airflow, and ensuring the accuracy of detection data of the MEMS pressure sensor, the cleanliness of the sensing diaphragm, and the stability of long-term work.

[0011] Preferably, an annular flow guide cavity is arranged between the rectifying net and the buffer cavity, the inner diameter of the annular flow guide cavity gradually decreases from the buffer cavity to the rectifying net at a contraction angle of 5°-8°, the inner wall of the annular flow guide cavity has a roughness Ra≤0.1 μm after machining, and the length of the annular flow guide cavity is 1 / 3-1 / 2 of the total length of the buffer cavity; by arranging the annular flow guide cavity with the inner diameter gradually decreasing from the buffer cavity to the rectifying net at a contraction angle of 5°-8°, the inner wall roughness Ra≤0.1 μm, and the length of 1 / 3-1 / 2 of the total length of the buffer cavity, after the pulsed gas flows through the plurality of flow guide vanes, the annular flow guide cavity can guide the airflow treated by the buffer cavity to smoothly transition to the rectifying net, reduce the turbulent disturbance and pressure loss of the airflow in the transition area, avoid the influence of airflow turbulence on the rectifying 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.

[0012] Preferably, the sensing diaphragm is made of silicon-based material, a stepped flexible connecting ring is arranged between the sensing diaphragm and the inner wall of the sensing installation cavity, the connecting ring is composed of three layers of composite structure of inner layer, middle layer and outer layer, the inner layer, the middle layer and the outer layer of the connecting ring are made of nickel-titanium alloy, polyimide and beryllium copper respectively, the thickness of the inner layer and the outer layer of the connecting ring is 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 arranging the three-layer composite stepped flexible connecting ring composed of nickel-titanium alloy, polyimide and beryllium copper between the silicon-based sensing diaphragm and the inner wall of the sensing installation cavity, and the thickness of the inner layer and the outer layer is equal and the thickness of the middle layer is 1 / 2, the gradient matching of the thermal expansion coefficients of different materials and the structural flexibility are utilized, when the MEMS pressure sensor is affected by external temperature change, the connecting ring can effectively alleviate the extrusion of the sensing diaphragm caused by the difference of the material expansion coefficients when the temperature changes, avoid the deformation and rupture of the sensing diaphragm and the decrease of the detection accuracy caused thereby, and ensure the measurement accuracy, structural stability and long-term working reliability of the MEMS pressure sensor in a wide temperature range.

[0013] Preferably, an annular groove is processed on the inner side of the air inlet of the shell, an oil-repellent and water-repellent film is arranged on the shell, the edge of the oil-repellent and water-repellent film is embedded in the annular groove, the oil-repellent and water-repellent film is located at the lowermost end of the air inlet, the plane of the oil-repellent and water-repellent film is parallel to the end face of the air inlet, and the surface of the oil-repellent and water-repellent film is kept in a tight state; by arranging the oil-repellent and water-repellent film in the annular groove on the inner side of the air inlet of the shell, the oil-repellent and water-repellent film is located at the lowermost end of the air inlet, the plane of the oil-repellent and water-repellent film is parallel to the end face of the air inlet, and the surface of the oil-repellent and water-repellent film is kept in a tight state, the oil-repellent and water-repellent characteristics of the film and the edge embedding design are utilized, when the pulse gas passes through the oil-repellent and water-repellent film, the liquid pollutants such as oil fume and water vapor in the air inlet and the small impurities can be effectively blocked from penetrating from the edge, the pollutants adhering to the surface of the sensing diaphragm or entering the inside of the sensor to affect the sensing accuracy and cause component corrosion are avoided, and the detection sensitivity, measurement accuracy and long-term working reliability and cleanliness of the MEMS pressure sensor are ensured.

[0014] Preferably, a plurality of buffer grooves are arranged on the outer side wall of the ASIC signal processing unit, a buffer ring is arranged in each of the buffer grooves, and the outer side wall of the buffer ring is connected with the inner side wall of the signal processing cavity; by arranging the buffer ring in the plurality of buffer grooves on the outer side wall of the ASIC signal processing unit, and connecting the outer side wall of the buffer ring with the inner side wall of the signal processing cavity, the positioning effect of the buffer grooves and the elastic buffering performance of the buffer ring are utilized, when the MEMS pressure sensor is affected by external vibration, the buffer grooves and the buffer ring can effectively absorb the impact of external vibration on the ASIC signal processing unit, the element contact failure, structural damage and signal processing abnormality caused by vibration are avoided, and the stability of the signal processing of the MEMS pressure sensor, the structural integrity of the electronic elements and the accuracy of the data output are ensured.

[0015] Preferably, the upper end of the shell is threadedly connected with a mounting cap, a rotating groove is coaxially arranged on the mounting cap, a sealing plate is coaxially and rotatably connected in the rotating groove, a wiring terminal is arranged on the ASIC signal processing unit, and the wiring terminal extends to the upper side of the sealing plate; the upper end of the shell is threadedly connected with the mounting cap, the mounting cap is coaxially and rotatably connected with the sealing plate in the rotating groove, and the wiring terminal of the ASIC signal processing unit extends to the upper side of the sealing plate, so that the mounting cap is stably assembled and conveniently disassembled through thread connection, the rotating characteristic of the sealing plate is utilized to avoid wire distortion under stress during wiring, and the sealing property of the signal processing cavity is ensured, so that signal interference or component damage caused by loose installation, wiring damage and invasion of external pollutants is avoided, and the installation reliability, wiring safety, signal transmission stability and internal environment sealing property of the MEMS pressure sensor are ensured.

[0016] Compared with the prior art, the application has the following beneficial effects:

[0017] 1. The detection channel and the buffer cavity are arranged in the shell, the pulse airflow first enters the detection channel through the air inlet to avoid direct and disordered impact of the airflow, and then the airflow enters the buffer cavity, the airflow speed and pressure peak value are gradually reduced by utilizing the characteristic that the cross-sectional area of the cavity gradually increases, the pulse energy is dispersed, the originally concentrated strong impact force is converted into gentle pressure transmission, the abrasion and damage risk of the sensing diaphragm caused by frequent bearing of intense pressure is reduced, the structural stability and sensing sensitivity of the sensing diaphragm are helped to maintain, and the accuracy of pressure detection and the reliability of long-term work of the MEMS pressure sensor are ensured.

[0018] 2. The plurality of guide vanes are circumferentially and uniformly arranged on the inner wall of the lower end of the buffer cavity, the plurality of guide vanes in the arc-shaped thin plate structure, the concave surface of which faces the air inlet and the edge of which is rounded, are circumferentially and uniformly arranged on the inner wall of the lower end of the buffer cavity, the pulse airflow entering the air inlet can be divided into multiple sub-streams, the airflow is guided to flow smoothly by the arc-shaped concave surface, the rounded edge avoids turbulence caused by airflow impact, the local concentrated impact of the pulse airflow on the sensing diaphragm is avoided, the deformation and rupture risk of the sensing diaphragm caused by stress concentration is reduced, and the sensing sensitivity, detection accuracy and structural reliability of long-term work of the MEMS pressure sensor are ensured.

[0019] 3. This invention achieves full coverage by coaxially installing a rectifier mesh within the housing and by coaxially installing a cylindrical rectifier mesh between the buffer chamber and the sensing diaphragm, which is larger than the diameter of the sensing diaphragm. The mesh design, with its regular hexagonal array arrangement and parallel to the housing axis, further rectifies the airflow after buffering and guiding, transforming turbulent airflow into uniform laminar flow. At the same time, it intercepts tiny particulate contaminants in the airflow, avoiding problems such as localized stress on the sensing diaphragm and the impact of contaminant adhesion on sensing accuracy caused by uneven airflow. This ensures the accuracy of the detection data of the MEMS pressure sensor, the cleanliness of the sensing diaphragm, and the stability of long-term operation. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the MEMS pressure sensor of the present invention;

[0021] Figure 2 This is a schematic diagram of the internal structure of the MEMS pressure sensor of the present invention;

[0022] Figure 3 For the present invention Figure 2 A cross-sectional view of the shell at point AA;

[0023] Figure 4 For the present invention Figure 3 Full sectional view;

[0024] Figure 5 This is a schematic diagram of the gas flow inside the MEMS pressure sensor of the present invention;

[0025] Figure 6 For the present invention Figure 4 Sectional view at point BB;

[0026] Figure 7 This is an exploded view of the MEMS pressure sensor of the present invention.

[0027] In the diagram: 1. Housing; 101. Sensor mounting cavity; 102. Signal processing cavity; 103. Air inlet; 104. Annular groove; 105. Oleophobic and hydrophobic film; 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 Implementation

[0028] Please see Figures 1 to 7 This invention provides a MEMS pressure sensor, the technical solution of which is as follows:

[0029] A MEMS pressure sensor, please refer to Figures 1 to 7 , including shell 1, sensing diaphragm 2 and ASIC signal processing unit 3, shell 1 is provided with sensing installation cavity 101 and signal processing cavity 102, sensing installation cavity 101 is located in the lower side 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, a plurality of buffer grooves 901 are formed on the outer wall of ASIC signal processing unit 3, a plurality of buffer rings 902 are arranged in a plurality of buffer grooves 901, the outer wall of a plurality of buffer rings 902 is connected with the inner wall of signal processing cavity 102, the upper end of shell 1 is threadedly connected with mounting cap 903, rotation groove 904 is coaxially formed on mounting cap 903, sealing plate 905 is coaxially connected in rotation groove 904, wiring terminal 906 is arranged on ASIC signal processing unit 3, wiring terminal 906 extends to the upper side of sealing plate 905, gas inlet 103 is formed on the lower end surface of shell 1, annular groove 104 is processed in the inner side of gas inlet 103, oil and water repellent membrane 105 is arranged on shell 1, the edge of oil and water repellent membrane 105 is embedded in annular groove 104, oil and water repellent membrane 105 is located at the lowermost end of gas inlet 103, the plane of oil and water repellent membrane 105 is parallel to the end surface of gas inlet 103, and the surface of oil and water repellent membrane 105 is kept in a taut state, detection channel 4 and buffer cavity 5 are formed in shell 1, the upper and lower ends of detection channel 4 are communicated with buffer cavity 5 and gas inlet 103 respectively, the upper end of buffer cavity 5 is communicated with sensing installation cavity 101, and buffer cavity 5 is designed in a gradually expanding manner from bottom to top, a plurality of guide vanes 501 are circumferentially distributed on the inner wall of the lower end of buffer cavity 5, a plurality of guide vanes 501 are in arc-shaped thin plate structure, the concave surface of a plurality of guide vanes 501 faces the direction of gas inlet 103, and the edges of a plurality of guide vanes 501 are rounded, rectifier net 6 is coaxially arranged in shell 1, rectifier net 6 is in cylindrical shape, rectifier net 6 is located between buffer cavity 5 and sensing diaphragm 2, the diameter of rectifier net 6 is greater than the diameter of sensing diaphragm 2, a plurality of mesh holes 601 are arranged on rectifier net 6, a plurality of mesh holes 601 are arranged in regular hexagonal array, a plurality of mesh holes 601 are parallel to the axis of shell 1, annular guide cavity 7 is arranged between rectifier net 6 and buffer cavity 5, the inner diameter of annular guide cavity 7 gradually decreases from buffer cavity 5 to rectifier net 6, and the shrinkage angle is 6°; the inner wall of annular guide cavity 7 has a roughness Ra=0.1 μm after machining, 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 a stepped flexible connecting ring 8 is arranged 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, 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 inner layer 801 and 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.

[0030] In operation, referring to Figures 1 to 7 , the air flow of the automobile intake system first enters through the air inlet 103 at the lower end of the shell 1, and contacts the oil-repellent and water-repellent film 105 at the lowermost end of the air inlet 103; the oil-repellent and water-repellent film 105 is embedded in the annular groove 104 through the sealing design of the tight surface and the edge, and uses the oil-repellent and water-repellent characteristics to make liquid pollutants form liquid beads and roll off, and uses the principle of physically blocking solid particles to intercept oil fume, water vapor and solid particles ≥0.1 μm in the air flow, so as to avoid the pollutants from entering the subsequent core structure; the filtered air flow vertically upwardly flows through the detection channel 4 and enters the lower end of the buffer cavity 5; the air flow enters the gradually expanding buffer cavity 5, uses the characteristic of the increasing cavity volume to preliminarily reduce the air flow velocity and weaken the pulse pressure peak, so as to reduce the wear and damage risk of the sensing diaphragm 2 caused by frequently bearing severe pressure.

[0031] Further, the arc-shaped guide vane 501 with the concave inner wall at the lower end of the buffer cavity 5 faces the air inlet 103, which divides the air flow into multiple branch flows, the arc-shaped concave surface of the guide vane 501 guides the air flow to stably flow along the inner wall of the buffer cavity 5, and the edge round treatment of the guide vane 501 avoids the turbulence when the air flow impacts the guide vane 501, and further disperses the pulse energy; at this time, the air flow treated by the guide vane 501 enters the annular guide cavity 7 with a contraction angle of 6° and a length of 1 / 2 of the total length of the buffer cavity 5, the structure of the gradually reduced inner diameter of the annular guide cavity 7 forces the air flow to converge to the center, and cooperates with the low roughness design of Ra=0.1 μm of the inner wall of the annular guide cavity 7 to reduce the friction disturbance between the air flow and the cavity wall of the annular guide cavity 7, so as to make the air flow transition from “dispersed flow” to “quasi-laminar flow”; the air flow finally enters the cylindrical rectifying net 6 with a diameter larger than that of the sensing diaphragm 2, at this time, the hexagonal array and parallel to the axis of the shell 1 of the mesh hole 601 combs the air flow, converts the residual turbulence into uniform laminar flow parallel to the axis of the shell 1 through the shunt effect of the mesh hole 601, and completely covers the sensing area of the sensing diaphragm 2.

[0032] The rectified laminar flow vertically acts on the silicon-based sensing diaphragm 2, the sensing diaphragm 2 generates a small deformation under the pressure, and the deformation amount is linearly related to the pressure; since the sensing diaphragm 2 is fixed with the inner wall of the sensing installation cavity 101 through the stepped flexible connecting ring 8, the inner layer 801 of nickel-titanium alloy, the middle layer 802 of polyimide and the outer layer 803 of beryllium copper of the connecting ring 8 are matched through the material elasticity and the thickness of the inner layer 801 is equal to that of the outer layer 803, and the thickness of the middle layer 802 is 1 / 2 of that of the inner and outer layers 803, so as to relieve the stress difference caused by the thermal expansion of silicon and the metal shell 1 due to temperature change, avoid the sensing diaphragm 2 from generating additional deformation due to stress extrusion, and ensure that the deformation amount is only determined by the air flow pressure; at this time, the sensing diaphragm 2 converts the deformation into an electric signal through capacitance change or resistance change, and transmits the electric signal to the signal processing cavity 102 through the lead wire.

[0033] Further, after the electric 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, for example, airflow turbulence residues and circuit thermal noise interference; since the buffer ring 902 is arranged in the buffer groove 901 on the outer wall of the ASIC signal processing unit 3 and connected with the inner wall of the signal processing cavity 102, the buffer ring 902 can absorb the impact vibration of the ASIC signal processing unit 3 caused by, for example, engine vibration, so as to avoid loosening of circuit connection or damage of components; the processed signal is output through the wiring end 906 extending to the upper side of the sealing plate 905, the sealing plate 905 can rotate with the rotating groove 904 of the mounting cap 903, so as to avoid twisting of the wire during wiring and ensure stable transmission of the signal, and meanwhile the ASIC signal processing unit 3 is sealed and protected.

[0034] The above describes one specific embodiment of the application in detail with reference to the drawings, but the application is not limited to the above described embodiment. For those skilled in the art, various changes, modifications, replacements and variations can be made to the embodiment without departing from the principles and ideas of the application, and still fall within the protection scope of the application.

Claims

1. A MEMS pressure sensor, characterized by, The utility model relates to a kind of gas concentration detection device, including shell (1), sensing diaphragm (2) and ASIC signal processing unit (3), the shell (1) is equipped with sensing installation cavity (101) and signal processing cavity (102) in, sensing installation cavity (101) is located signal processing cavity (102) downside, sensing diaphragm (2) and ASIC signal processing unit (3) are respectively installed in sensing installation cavity (101) and signal processing cavity (102) in, the lower end surface of shell (1) is equipped with air inlet (103), the shell (1) is equipped with detection channel (4) and buffer cavity (5) in, 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 the buffer cavity (5) is gradually expanded design from below to top;The lower end inner wall of buffer cavity (5) is circumferentially distributed with multiple guide vanes (501), multiple the guide vanes (501) are arc thin plate structure, the concave surface of multiple the guide vanes (501) is towards air inlet (103) direction, the edge of multiple the guide vanes (501) is all done round angle processing;The shell (1) is coaxially installed with rectifier net (6) in, the rectifier net (6) is cylindrical, the rectifier net (6) is located between buffer cavity (5) and sensing diaphragm (2), the diameter of rectifier net (6) is greater than the diameter of sensing diaphragm (2), the rectifier net (6) is equipped with multiple mesh (601), multiple the mesh (601) is arranged in regular hexagon array, multiple the mesh (601) is all parallel with the axis of shell (1);The rectifier net (6) and buffer cavity (5) are equipped with annular flow guide cavity (7) between, the inner diameter of annular flow guide cavity (7) gradually reduces from buffer cavity (5) to rectifier net (6) direction, and the shrinkage angle is 5 °-8 °;The inner wall of annular flow guide cavity (7) is machined after roughness Ra≤0.1 μm, and the length of annular flow guide cavity (7) is 1 / 3-1 / 2 of 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), the 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 inner layer (801) and 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).

2. The MEMS pressure sensor of claim 1, wherein: The inside of the air inlet (103) of the shell (1) is processed with an annular groove (104), the shell (1) is installed with an oil and water repellent film (105), the edge of the oil and water repellent film (105) is embedded into the annular groove (104), the oil and water repellent film (105) is located at the lowermost end of the air inlet (103), the plane of the oil and water repellent film (105) is parallel to the end face of the air inlet (103), and the surface of the oil and water repellent film (105) is kept in a taut state.

3. The MEMS pressure sensor of claim 1, wherein: A plurality of buffer grooves (901) are formed on the outer wall of the ASIC signal processing unit (3), a buffer ring (902) is arranged in each buffer groove (901), and the outer wall of the buffer ring (902) is connected with the inner wall of the signal processing cavity (102).

4. The MEMS pressure sensor of claim 3, wherein: A mounting cap (903) is threadedly connected to the upper end of the shell (1), a rotating groove (904) is coaxially formed in the mounting cap (903), a sealing plate (905) is coaxially and rotatably connected in the rotating groove (904), a wiring end (906) is arranged on the ASIC signal processing unit (3), and the wiring end (906) extends to the upper side of the sealing plate (905).

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