Micro air pressure sensor with self-tensioning pressure sensing film and adjustable measuring range

Abstract

A micro air pressure sensor with a self-tensioning pressure sensing film and an adjustable measuring range comprises an upper shell, a middle shell and a lower shell which are sequentially arranged from top to bottom, and the upper shell and the middle shell are movably matched; a pressure sensing film is fixed to the bottom of the middle shell, one of the bottom of the middle shell and the top of the lower shell is provided with a groove, the other one of the bottom of the middle shell and the top of the lower shell is provided with a protruding edge, the groove and the protruding edge are matched to form a film self-tensioning structure, and the middle shell and the lower shell are detachably connected. The lower shell is provided with a third cavity located below the pressure sensing film and an air inlet communicated with the third cavity. An insulating substrate is arranged in the first cavity, an electrode set is arranged on the side, close to the pressure sensing film, of the insulating substrate, the electrode set and the pressure sensing film are arranged in a spaced mode, and the electrode distance between the electrode set and the pressure sensing film is adjusted by making the upper shell move in the axial direction of the middle shell. Output signal short circuit caused by the fact that the pressure sensing film is attached to the electrode set can be avoided, and the effect of adjusting the measuring range of the sensor can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-pressure sensors, and particularly to a micro-pressure sensor with a self-tensioning pressure-sensitive film and an adjustable measuring range. Background Art

[0002] As a key component in the modern aerospace field, aerospace vehicles not only integrate various functions such as spacecraft, space shuttles, and transportation tools, but also play an irreplaceable role in space exploration, scientific research, environmental monitoring, and technological innovation. When an aerospace vehicle flies in the near space and low Earth orbit, its surface is affected by the tiny air pressure generated by the high-altitude rarefied air. This continuous micro-pressure may cause deformation, component loosening, and even part detachment of the tiny devices and equipment of the spacecraft, resulting in serious consequences. Therefore, monitoring the tiny air pressure in the environment where the aerospace vehicle is located is of great significance for both theoretical research and practical applications.

[0003] Micro-pressure sensors are instruments used to measure the rarefaction degree of gases below atmospheric pressure. They indirectly measure the air pressure through different physical phenomena. There are various types of modern micro-pressure sensors with different working principles, and most of them use indirect methods to measure pressure. Among existing micro-pressure sensors, capacitive thin-film micro-pressure sensors are widely used in various fields due to their advantages such as high precision, fast response, wide measurement range, insensitivity to the types of measured gases, miniaturized design, low-power consumption operation, and long-term stability. However, in the production and manufacturing process of current absolute-pressure capacitive thin-film micro-pressure sensors, there are problems such as the pressure-sensitive film being prone to uneven welding and short-circuiting of the output signal due to fitting with the electrode group, a relatively narrow pressure measurement range, and an unadjustable measuring range, resulting in being unable to better meet different actual application requirements. Summary of the Invention

[0004] Aiming at the deficiencies in the background art, the purpose of the present invention is to provide a micro-pressure sensor with a self-tensioning pressure-sensitive film and an adjustable measuring range.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A micro-pressure sensor with a pressure-sensitive film that is self-tensioning and has an adjustable range, comprising an upper housing, a middle housing, and a lower housing arranged in sequence from top to bottom. A first cavity is provided at the bottom of the upper housing. The middle housing is provided with a second cavity that penetrates through its top and bottom. The upper housing and the middle housing are movably matched. A pressure-sensitive film is fixed to the bottom of the middle housing. One of the bottom of the middle housing and the top of the lower housing is provided with a groove, and the other is provided with a convex rib. The groove and the convex rib cooperate to form a film self-tensioning structure. The middle housing and the lower housing are detachably connected. The lower housing is provided with a third cavity below the pressure-sensitive film and an air inlet communicating with the third cavity. An insulating substrate is provided in the first cavity. An electrode group is provided on one side of the insulating substrate close to the pressure-sensitive film and is arranged at an interval from the pressure-sensitive film. By moving the upper housing axially along the middle housing, the pole pitch between the electrode group and the pressure-sensitive film is adjusted.

[0007] Further, an external thread is provided on the outer side of the upper housing, and an internal thread is provided on the inner side of the middle housing. After adjusting the relative position between the upper housing and the middle housing through thread cooperation, the relative position between the upper housing and the middle housing is fixed by vacuum brazing.

[0008] Further, a plurality of threaded holes are provided along the circumferential direction of the middle housing. The lower housing and the pressure-sensitive film are respectively provided with first through holes and second through holes that are adapted in position and size to the threaded holes. A plurality of locking members are provided at the bottom of the lower housing. Each of the locking members sequentially passes through the first through hole, the second through hole and is threadedly engaged with the threaded hole.

[0009] Further, one of the bottom of the middle housing and the top of the lower housing is provided with a limiting post along its circumferential direction, and the other is provided with a limiting hole adapted to the limiting post. The pressure-sensitive film is provided with a third through hole adapted to the limiting post.

[0010] Further, the electrode group includes an inner electrode and an outer electrode. The outer electrode is arranged around the outer circumference of the inner electrode, and the inner electrode and the outer electrode are provided with lead-out electrodes that pass through the insulating substrate to the outside of the upper housing.

[0011] Further, two fourth through holes are provided at the top of the upper housing. After the lead-out electrodes pass through the fourth through holes, at least part of their positions are located outside the upper housing. Sealing members are filled between the two ends of each fourth through hole and the lead-out electrodes.

[0012] Further, the sealing member is a kovar alloy cap, and the air inlet is provided with a filter screen.

[0013] Further, a placement groove with a notch facing the first cavity is provided in the upper housing. A getter is placed in the placement groove, and a barrier net is provided at the notch of the placement groove.

[0014] Furthermore, the getter is provided with a number of micropores.

[0015] Furthermore, a circumferentially distributed convex ring is provided on the inner wall of the upper shell, and the insulating substrate is fixed to the convex ring.

[0016] As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. In the present invention, a pressure-sensitive film is fixed to the bottom of the middle shell, and one of the bottom of the middle shell and the top of the lower shell is provided with a groove, and the other is provided with a convex rib. The groove and the convex rib cooperate to form a film self-tensioning structure. The pressure-sensitive film is pressed through the film self-tensioning structure. During the pressing process, the film is slightly stretched to generate a pre-tensioning force, thereby flattening the film, trying to ensure the flatness of the film, and avoiding adverse effects such as wrinkles on the surface of the pressure-sensitive film and even short-circuit of the output signal caused by the pressure-sensitive film being in contact with the electrode group.

[0018] 2. In the present invention, an external thread is provided on the upper shell of the micro-pressure sensor, and an internal thread is provided inside the middle shell. The upper shell and the middle shell are matched through the internal and external threads, and the pole pitch between the electrode group and the pressure-sensitive film can be adjusted, so that the pressure measurement range of the sensor is increased, and the range of the sensor is adjusted by changing the pole pitch.

[0019] 3. In the present invention, a number of threaded holes are provided along the circumference of the middle shell. The lower shell and the pressure-sensitive film are respectively provided with a first through hole and a second through hole that are adapted to the threaded holes in terms of position and size. A number of locking members are provided at the bottom of the lower shell. Each locking member sequentially passes through the first through hole, the second through hole and is threadedly engaged with the threaded hole, and the magnitude of the pre-tensioning force applied by the film self-tensioning structure to the pressure-sensitive film is controlled by the locking degree of the locking member.

[0020] 4. In the present invention, one of the bottom of the middle shell and the top of the lower shell is provided with a limiting post along its own circumference, and the other is provided with a limiting hole adapted to the limiting post. The pressure-sensitive film is provided with a third through hole adapted to the limiting post. The cooperation among the limiting post, the limiting hole and the third through hole achieves the effect of restricting the radial displacement of the pressure-sensitive film.

[0021] 5. In the present invention, a number of micropores are processed inside the getter. The specific surface area of the getter is increased through this micropore structure, thereby improving the gas absorption performance of the getter, improving the vacuum degree of the sensor, and ensuring that the working environment of the micro-pressure sensor meets the requirements. Description of the Drawings

[0022] To more clearly illustrate the technical solutions in the embodiments of the invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0023] Figure 1 Overall schematic diagram of the present invention;

[0024] Figure 2 Overall exploded view of the present invention;

[0025] Figure 3 One of the overall cross-sectional views of the present invention;

[0026] Figure 4 Another overall cross-sectional view of the present invention;

[0027] Figure 5 Bottom schematic diagram of the upper housing and the middle housing of the present invention;

[0028] Figure 6 Top schematic diagram of the lower housing of the present invention;

[0029] In the figure, 10 is the upper housing; 101 is the first cavity; 102 is the external thread; 103 is the fourth through hole; 104 is the placement groove; 105 is the getter; 1051 is the micropore; 106 is the barrier net; 107 is the convex ring; 20 is the middle housing; 201 is the groove; 202 is the internal thread; 203 is the threaded hole; 204 is the limiting post; 30 is the lower housing; 301 is the third cavity; 302 is the air inlet; 3021 is the filter screen; 303 is the convex rib; 304 is the first through hole; 305 is the limiting hole; 40 is the pressure-sensitive film; 401 is the second through hole; 402 is the third through hole; 50 is the insulating substrate; 60 is the electrode group; 601 is the internal electrode; 602 is the external electrode; 603 is the lead-out electrode; 604 is the seal; 605 is the ceramic rod. Detailed implementation manners

[0030] The following will be combined with Figure 1-6 to describe the present invention in detail.

[0031] A micro-pressure sensor with a self-tensioning and adjustable range for a pressure-sensitive film 40, comprising an upper housing 10, a middle housing 20, and a lower housing 30 arranged in sequence from top to bottom. A first cavity 101 is provided at the bottom of the upper housing 10. The middle housing 20 is provided with a second cavity that penetrates through its top and bottom. The upper housing 10 and the middle housing 20 are movably matched; a pressure-sensitive film 40 is fixed to the bottom of the middle housing 20, and one of the bottom of the middle housing 20 and the top of the lower housing 30 is provided with a groove 201, and the other is provided with a convex rib 303. The groove 201 and the convex rib 303 cooperate to form a film self-tensioning structure, and the middle housing 20 and the lower housing 30 are detachably connected. The lower housing 30 is provided with a third cavity 301 below the pressure-sensitive film 40 and an air inlet 302 communicating with the third cavity 301; an insulating substrate 50 is provided in the first cavity 101, and an electrode group 60 is provided on the side of the insulating substrate 50 close to the pressure-sensitive film 40 and spaced from the pressure-sensitive film 40. By moving the upper housing 10 along the axial direction of the middle housing 20, the pole pitch between the electrode group 60 and the pressure-sensitive film 40 is adjusted.

[0032] Specifically, the middle housing 20 is sleeved on the outer side wall of the upper housing 10, and the upper housing 10 can move along the axial direction of the middle housing 20. In the normal state, as Figure 3 shown, the bottom end face of the upper housing 10 is flush with the bottom end face of the lower housing 30. At this time, the positions of the insulating substrate 50 and the electrode group 60 are at a certain distance from the position where the pressure-sensitive film 40 is arranged. Then, as Figure 4 shown, according to the actual situation, the upper housing 10 can be moved away from the middle housing 20 along the axial direction of the middle housing 20, so as to increase the distance between the insulating substrate 50 and the pressure-sensitive film 40, adjust the pole pitch between the electrode group 60 and the pressure-sensitive film 40, and fix the upper housing 10 and the middle housing 20 to each other after adjustment. The fixing method is such as snap connection or threaded cooperation in the lower section; a groove 201 is provided circumferentially at the bottom of the middle housing 20, and a convex rib 303 is provided circumferentially at the top of the lower housing 30. The pressure-sensitive film 40 is pressed by the film self-tensioning structure. During the pressing process, the film is slightly stretched to generate a pre-tensioning force, so as to flatten the film, try to ensure the flatness of the film, and avoid short-circuiting of the output signal caused by the pressure-sensitive film 40 sticking to the electrode group 60; the width of the groove 201 is 500um - 700um, and the height is 200um - 300um; the pressure-sensitive film 40 separates the middle housing 20 and the lower housing 30 into a non-communicating detection cavity and a vacuum cavity. The detection cavity is the third cavity 301 below the pressure-sensitive film 40, and the vacuum cavity is the first cavity 101 above the pressure-sensitive film 40; the electrode group 60 is installed on the side of the insulating substrate 50 close to the pressure-sensitive film 40 to output the capacitance change signal generated by the deformation of the pressure-sensitive film 40.

[0033] In this embodiment, an external thread 102 is provided on the outer side of the upper housing 10, and an internal thread 202 is provided on the inner side of the middle housing 20. After adjusting the relative position between the upper housing 10 and the middle housing 20 through thread fitting, the relative position between the upper housing 10 and the middle housing 20 is fixed by vacuum brazing. Specifically, the range of the sensor is determined according to actual application requirements such as the usage scenario, and then the distance between the electrode group 60 and the pressure-sensitive film 40, that is, the pole pitch, is adjusted through thread fitting to an appropriate value. By changing the pole pitch, the range of the sensor is adjusted. The degree to which the distance between the electrode group 60 and the pressure-sensitive film 40 is adjusted can be observed by the upward movement degree of the upper housing 10, and the upward movement degree of the upper housing 10 can be controlled by observing the number of exposed threads or directly measuring with a ruler. The conversion between the range of the sensor and the value of this distance belongs to the common knowledge in the art and will not be elaborated here; Vacuum brazing is a brazing process carried out in a vacuum environment. By heating the filler metal under vacuum conditions, it is melted and filled into the joint gap to achieve the connection of parts. This process has the advantages of cleanliness, no oxidation, and high weld quality, and is widely used in fields such as aerospace, electronics, and automotive; Vacuum brazing is used to weld the junction of the upper housing 10 and the middle housing 20 to achieve fixation. After vacuum brazing, the range cannot be adjusted again. Therefore, it is necessary to adjust to an appropriate range before vacuum brazing.

[0034] In this embodiment, the middle housing 20 is provided with a plurality of threaded holes 203 along its circumferential direction. The lower housing 30 and the pressure-sensitive film 40 are respectively provided with a first through hole 304 and a second through hole 401 that are adapted to the threaded holes 203 in terms of position and size. A plurality of locking members are provided at the bottom of the lower housing 30, and each locking member sequentially passes through the first through hole 304 and the second through hole 401 and is in threaded fit with the threaded hole 203. Specifically, the magnitude of the pre-tension force applied by the film self-tensioning structure to the pressure-sensitive film 40 is controlled by the locking degree of the locking members. The locking members are screws or bolts; The threaded holes 203 are M1.6 threaded holes 203 provided at the bottom of the middle housing 20 and distributed at intervals of 90° along the circumference.

[0035] In this embodiment, one of the bottom of the middle housing 20 and the top of the lower housing 30 is provided with a limit post 204 along its circumferential direction, and the other is provided with a limit hole 305 adapted to the limit post 204. The pressure-sensitive film 40 is provided with a third through hole 402 adapted to the limit post 204. Specifically, the limit post 204 is provided at the bottom of the middle housing 20, and the limit hole 305 is provided at the top of the lower housing 30; The cooperation among the limit post 204, the limit hole 305, and the third through hole 402 achieves the effect of restricting the radial displacement of the pressure-sensitive film 40; The diameter of the limit post 204 is 1 mm - 1.2 mm, and the height is 1 mm - 1.2 mm.

[0036] In this embodiment, the electrode group 60 includes an inner electrode 601 and an outer electrode 602. The outer electrode 602 is disposed around the outer periphery of the inner electrode 601, and the inner electrode 601 and the outer electrode 602 are provided with lead electrodes 603 that pass through the insulating substrate 50 to the outside of the upper housing 10. Specifically, there is a gap between the outer electrode 602 and the inner electrode 601; one end of each lead electrode 603 is connected to the outer electrode 602 or the inner electrode 601, and the other end passes through a perforation provided separately in the insulating substrate 50 and the first chamber to the outside of the upper housing 10, and the aspect ratio of the perforation is high; the outer electrode 602 and the inner electrode 601 are respectively fixed to the insulating substrate 50 by vacuum welding. The inner electrode 601 is located in the middle of the insulating substrate 50, and the outer electrode 602 is close to the edge of the insulating substrate 50.

[0037] In this embodiment, two fourth through holes 103 are provided at the top of the upper housing 10. After passing through the fourth through holes 103, at least part of the lead electrode 603 is located outside the upper housing 10, and a seal 604 is filled between both ends of each fourth through hole 103 and the lead electrode 603. Specifically, a ceramic rod 605 is sleeved on the part of the lead electrode 603 located outside the upper housing 10; the seal 604 is a kovar alloy cap, and filling the kovar alloy cap is used to ensure the vacuum degree of the first chamber, that is, the vacuum chamber, and prevent air leakage.

[0038] In this embodiment, in this embodiment, a placement groove 104 with a notch facing the first cavity 101 is provided in the upper housing 10. An getter 105 is placed in the placement groove 104, and a barrier net 106 is provided at the notch of the placement groove 104. The getter 105 is provided with a number of micro holes 1051. Specifically, the getter 105 is used to absorb the gas in the first cavity, that is, the vacuum chamber. The barrier net 106 is fixed to the inner wall of the upper housing 10, thereby fixing the getter 105 in the placement groove 104; the getter 105 adopts a non-evaporable Ti-based bulk getter 105, and its shape is adapted to the shape of the placement groove 104, for example, it is a cylinder. The metal material of the barrier net 106 can be stainless steel, inconel, etc.; high-aspect-ratio micro holes 1051 can also be processed on the getter 105 by five-axis laser machining. The diameter of the micro holes 1051 processed on the getter 105 can be 200 um, and the height is 7 mm, but it is not limited thereto. Through this micro hole 1051 structure, the specific surface area of the getter 105 is increased, thereby improving the gas absorption performance of the getter 105, improving the vacuum degree of the sensor, and ensuring that the working environment of the micro pressure sensor meets the requirements.

[0039] In this embodiment, a circumferentially distributed convex ring 107 is provided on the inner wall of the upper housing. The insulating substrate 50 is fixed to the convex ring 107, and a filter net 3021 is provided at the air inlet 302. Specifically, the air inlet 302 is connected to a pipe body, and the pipe body is welded to the air inlet 302 and the two are communicated; the filter net 3021 is used to filter impurities in the gas to be measured. The filter net 3021 is made of polytetrafluoroethylene material, and the filter net 3021 is bonded to the air inlet 302.

[0040] The upper housing 10, the middle housing 20, the lower housing 30 and the pressure-sensitive film 40 are made of a metal material, such as nickel-chromium alloy; the insulating substrate 50 is made of a ceramic material, such as 95 alumina material; the outer electrode 602 and the inner electrode 601 can be made of a metal material such as copper, and the lead-out electrode 603 is also made of copper.

[0041] A manufacturing method of a micro-pressure sensor with a self-tensioning and adjustable range pressure-sensitive film 40 includes the following steps:

[0042] 1) Fabricate the upper housing 10, the middle housing 20, the lower housing 30, the pressure-sensitive film 40, the insulating substrate 50 and the electrode group 60 with corresponding structures;

[0043] Specifically, first prepare the upper housing 10, the middle housing 20, the lower housing 30 and the pressure-sensitive film 40 respectively; then fabricate the first cavity 101, the external thread 102, the convex ring 107 and the fourth through hole 103 on the upper housing 10; fabricate the second cavity, the internal thread 202, the groove 201, the threaded hole 203, the limiting post 204 on the middle housing 20; fabricate the convex rib 303, the third cavity 301, the air inlet 302, the first through hole 304 and the limiting hole 305 on the lower housing 30; fabricate the second through hole 401 and the third through hole 402 on the pressure-sensitive film 40; fabricate the lead-out electrode 603 on the electrode group 60; fabricate a placement groove 104 with the notch facing the first cavity 101 on the upper housing 10, place a getter 105 in the placement groove 104 and weld a barrier net 106 at the notch for fixation.

[0044] 2) Use a five-axis laser to machine a certain number of micro-holes 1051 with a high aspect ratio inside the getter 105;

[0045] 3) After adjusting the relative positions between the upper housing 10 and the middle housing 20 through thread fitting, use vacuum brazing to weld parts such as the upper housing 10, the middle housing 20, the pressure-sensitive film 40, the insulating substrate 50, the electrode group 60, the getter 105, the ceramic rod 605, the electrode needle, the upper and lower kovar caps and the barrier net 106 to form an assembly with a vacuum cavity.

[0046] Specifically, after determining the range according to the working scenario before welding, the upper housing 10 and the middle housing 20 are moved to the corresponding positions through threaded engagement (the threaded engagement also serves as a pre-fixing function). Then, parts such as the pressure-sensitive film 40, the insulating substrate 50, the electrode group 60, the getter 105, the ceramic rod 605, the kovar alloy cap, and the barrier net 106 are placed at the corresponding positions of the upper and middle housings 20 and soldered to fix them. Solder is also applied to the connection between the upper housing 10 and the middle housing 20, and then it is placed in a vacuum brazing furnace for vacuuming and heating for welding; the insulating substrate 50 needs to be metallized before vacuum brazing. The main parts of the metallization treatment are: 1. The part where the insulating substrate 50 contacts and welds with the upper housing 10; 2. The inner wall of the through-hole on the insulating substrate 50 that contacts the electrode pins; 3. The part where the insulating substrate 50 contacts and welds with the electrode group 60.

[0047] 4) Tighten the obtained assembly above and the lower housing 30 by tightening the screws to form the entire micro-pressure sensor.

[0048] Specifically, first align the obtained assembly above with the lower housing 30 so that the position of the limiting post 204, the third through-hole 402, and the limiting hole 305 are aligned with each other, and the convex rib 303 and the concave groove 201 are in concave-convex fit. Then lock the middle housing 20 and the lower housing 30 through the locking member. After locking, the pressure-sensitive film 40 is tensioned, and the locking degree of the locking member controls the magnitude of the pre-tension force applied by the film self-tensioning structure to the pressure-sensitive film 40.

[0049] For a micro-pressure sensor with a self-tensioning and range-adjustable pressure-sensitive film 40 proposed by the present invention, its working principle is as follows:

[0050] The gas to be measured enters the third cavity 301, i.e., the detection cavity, through the air inlet 302. Under the action of the pressure difference between the gas pressure in the detection cavity and the pressure in the first cavity 101, i.e., the vacuum cavity, the pressure-sensitive film 40 located between the detection cavity and the vacuum cavity deforms. The capacitance between the insulating substrate 50 and the pressure-sensitive film 40 changes, causing the capacitance signal output by the electrode group 60 to change. An external conversion circuit is used to convert the capacitance change signal into a voltage or current signal for output, and the current air pressure value in the detection cavity can be obtained through signal processing.

[0051] More specifically, the pressure-sensitive film 40 undergoes deflection deformation under the action of uniform air pressure. The distance between the pressure-sensitive film 40 and the fixed electrode group 60 decreases. At this time, the measurement capacitance formed by the inner fixed electrode and the pressure-sensitive film 40 and the reference capacitance formed by the outer fixed electrode and the pressure-sensitive film 40 increase simultaneously. The output capacitance value is set as the difference between the measurement capacitance and the reference capacitance. When there is no uniform air pressure acting, the pressure-sensitive film 40 will return to the initial position parallel to the fixed electrode, and at the same time, the output capacitance returns to the initial capacitance state. During the mutual conversion process among the initial state, the loaded state, and the unloaded state, the output capacitance value corresponds to the loaded air pressure value, and the dynamic measurement of the load can be realized to a certain extent. The electrical signals generated by the measurement capacitance and the reference capacitance will be transmitted to the electronic control unit through the lead-out electrode 603. In the electronic control unit, the output capacitance result is obtained, and the capacitance change amount is converted into a voltage change amount through the conversion circuit, so as to obtain the vacuum degree measurement result.

[0052] The above embodiments are only used to illustrate the technical concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it. However, the protection scope of the present invention cannot be limited thereby. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A micro-pressure sensor with a pressure-sensitive film that is self-tensioning and has an adjustable range, characterized in that It includes an upper shell, a middle shell, and a lower shell which are arranged in sequence from top to bottom. A first cavity is provided at the bottom of the upper shell. The middle shell is provided with a second cavity that penetrates through its top and bottom. The upper shell and the middle shell are movably matched; a pressure-sensitive film is fixed at the bottom of the middle shell. One of the bottom of the middle shell and the top of the lower shell is provided with a groove, and the other is provided with a convex rib. The groove and the convex rib cooperate to form a film self-tensioning structure. The middle shell and the lower shell are detachably connected. The lower shell is provided with a third cavity below the pressure-sensitive film and an air inlet communicating with the third cavity; an insulating substrate is provided in the first cavity. An electrode group spaced from the pressure-sensitive film is provided on one side of the insulating substrate close to the pressure-sensitive film. By moving the upper shell axially along the middle shell, the pole pitch between the electrode group and the pressure-sensitive film is adjusted.

2. The micro-pressure sensor with a pressure-sensitive film that is self-tensioning and has an adjustable range as described in claim 1, characterized in that, External threads are provided on the outer side of the upper shell, and internal threads are provided on the inner side of the middle shell. After adjusting the relative position between the upper shell and the middle shell through thread fitting, the relative position between the upper shell and the middle shell is fixed by vacuum brazing.

3. The micro air pressure sensor with a pressure-sensitive film that is self-tensioning and has an adjustable range as claimed in claim 1 or 2, characterized in that, A number of threaded holes are provided along the circumferential direction of the middle shell. The lower shell and the pressure-sensitive film are respectively provided with first through holes and second through holes that are adapted in position and size to the threaded holes. A number of locking members are provided at the bottom of the lower shell. Each of the locking members sequentially passes through the first through hole, the second through hole and is threadedly engaged with the threaded hole.

4. The micro air pressure sensor with a pressure-sensitive film that is self-tensioning and has an adjustable range as described in claim 3, characterized in that, One of the bottom of the middle shell and the top of the lower shell is provided with a limiting post along its circumferential direction, and the other is provided with a limiting hole adapted to the limiting post. The pressure-sensitive film is provided with a third through hole adapted to the limiting post.

5. The micro air pressure sensor with self-tensioning and adjustable range of the pressure-sensitive film according to claim 1, characterized in that, The electrode group includes an inner electrode and an outer electrode. The outer electrode is arranged around the outer circumference of the inner electrode, and the inner electrode and the outer electrode are provided with lead-out electrodes that pass through the insulating substrate to the outside of the upper shell.

6. The micro air pressure sensor with self-tensioning and adjustable range of the pressure-sensitive film according to claim 5, characterized in that Two fourth through holes are provided at the top of the upper shell. After the lead-out electrodes pass through the fourth through holes, at least part of their positions are located outside the upper shell. Sealing members are filled between the two ends of each of the fourth through holes and the lead-out electrodes.

7. The micro-pressure sensor with a pressure-sensitive film that is self-tensioning and has an adjustable range as described in claim 6, wherein, The sealing member is a kovar alloy cap, and a filter screen is provided at the air inlet.

8. A micro-pressure sensor with a pressure-sensitive film that is self-tensioning and has an adjustable range, characterized in that A placement groove with a notch facing the first cavity is provided in the upper shell. An getter is placed in the placement groove, and a barrier net is provided at the notch of the placement groove.

9. The micro air pressure sensor with self-tensioning and adjustable range of the pressure-sensitive film according to claim 8, wherein The getter is provided with a number of micropores.

10. The micro air pressure sensor with a pressure-sensitive film that is self-tensioning and has an adjustable range as described in claim 1, characterized in that, Circumferentially distributed convex rings are provided on the inner wall of the upper shell, and the insulating substrate is fixed to the convex rings.

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