Anti-electromagnetic interference MEMS pressure sensing element

Abstract

The invention relates to the field of sensors, in particular to an anti-electromagnetic interference MEMS pressure sensing element which comprises a shell, a pressure sensitive film is arranged on the top of the shell, a sealed cavity is formed in the shell, pressure sensitivity and electrical detection are separated, the pressure sensitive film is exposed in the air, a capacitor structure is arranged in a box body in the sealed cavity, and the pressure sensitive film is exposed in the sealed cavity. The external electromagnetic interference on the capacitor structure is shielded; the pressure sensitive film deforms along with pressure change, so that air pressure in the sealed cavity is driven to change, the movable polar plate is driven to move through air pressure change, the movable polar plate and the corresponding first fixed polar plate form a first capacitor, and the movable polar plate and the corresponding second fixed polar plate form a second capacitor. The external pressure can be detected by detecting the change of the capacitance, and the movable polar plate is not in contact with the pressure sensitive film, so that the problem that the movable polar plate affects the bending deformation of the pressure sensitive film in the traditional capacitive MEMS pressure sensor is avoided.

Description

Technical Field

[0001] The present invention relates to the field of sensors, and in particular to a MEMS pressure sensing element that is resistant to electromagnetic interference. Background Art

[0002] MEMS pressure sensing elements are divided into two types: piezoresistive and capacitive. Both types expose the pressure sensitive film to the air. The pressure sensitive film responds sensitively to the external air pressure and is usually used as an electrical capacitor plate or resistor. Since it must be exposed to the air and cannot be set in a closed electrical cavity, external electromagnetic interference will affect the output of the MEMS pressure sensor.

[0003] Existing capacitive MEMS pressure sensors mostly use a single capacitor detection method: a sealed vacuum chamber is formed by a pressure-sensitive film and a substrate. When the external air pressure changes, the pressure-sensitive film above the vacuum chamber will bend, causing the capacitance formed by the pressure-sensitive film and the substrate to change. The external pressure can be obtained by detecting the capacitance change. Capacitive MEMS pressure sensors generally use a pressure-sensitive film to drive the moving plate up and down, so that the distance between the moving plate and the fixed plate changes, and the capacitance changes accordingly. The capacitance is used to detect changes in external pressure. When the pressure-sensitive film drives the moving plate to move up and down, the pressure-sensitive film first needs to overcome the weight of the moving plate, which affects the bending deformation of the pressure-sensitive film, thereby reducing the sensing accuracy of the capacitive MEMS pressure sensor. Summary of the invention

[0004] The purpose of the present invention is to provide a MEMS pressure sensing element that is resistant to electromagnetic interference, so as to solve the problem that the capacitive MEMS pressure sensor proposed in the above background technology generally drives the moving plate to move up and down through a pressure-sensitive film, thereby changing the distance between the moving plate and the fixed plate, and the capacitance changes accordingly, and the external pressure change is detected through the capacitance. When the pressure-sensitive film drives the moving plate to move up and down, the pressure-sensitive film first needs to overcome the weight of the moving plate, which affects the bending deformation of the pressure-sensitive film, thereby reducing the sensing accuracy of the capacitive MEMS pressure sensor.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: an electromagnetic interference-proof MEMS pressure sensing element, comprising a shell, a pressure-sensitive membrane is arranged on the top of the shell, a sealed cavity is opened inside the shell, a bottom plate is fixedly arranged on the bottom of the sealed cavity, a box body is fixedly arranged on one side of the top of the bottom plate, a cover plate is installed on the top of the box body, two ceramic plates are fixedly arranged on the bottom of the cover plate, a first fixed electrode plate and a second fixed electrode plate are respectively arranged on both sides of the two ceramic plates, and the first fixed electrode plate and the second fixed electrode plate are fixedly connected to the cover plate, side slide rails are arranged on both sides of the bottom of the box body, sliders are slidably connected to the two side slide rails, and the two sliders are fixedly connected to the moving electrode plate, a side plate is fixedly connected to one side of the box body, and two telescopic mechanisms are fixedly installed on the side plate; The two telescopic mechanisms each include a cylinder, one end of the cylinder is fixedly connected to a front end cover, the other end of the cylinder is fixedly connected to a rear end cover, a vent hole connected to the cylinder is provided on the top of the rear end tube, the vent hole is fixedly connected to a vent pipe, a piston cavity is provided in the cylinder, a piston is slidably connected in the piston cavity, one end of the piston is fixedly connected to an output shaft, and the ends of the two output shafts facing away from the piston pass through the front end cover and are respectively connected to two movable pole plates.

[0006] Preferably, a first sealing gasket is fixedly provided at the connection between the outer side of the top of the shell and the pressure sensitive membrane, and a second sealing gasket is fixedly provided at the connection between the box body and the cover plate and at the connection between the side plate and the cover plate.

[0007] Preferably, a fixing pad is fixedly connected to the bottom of the pressure sensitive membrane, an upper limit block is fixedly connected to the bottom of the fixing pad, and a lower limit block is fixedly connected to the top of the cover plate.

[0008] Preferably, the two movable pole plates are respectively arranged corresponding to the two ceramic plates, the movable pole plate is arranged corresponding to the first fixed pole plate and the second fixed pole plate connected to the corresponding ceramic plate, the movable pole plate and the corresponding first fixed pole plate constitute a first capacitor, and the movable pole plate and the corresponding second fixed pole plate constitute a second capacitor.

[0009] Preferably, a partition is fixedly provided on the top of one side of the box body, a cavity is separated inside the shell by the box body and the partition, the two telescopic mechanisms are located inside the cavity, the top ends of the two ventilation pipes are fixedly connected with pipe ends, and the two pipe ends are fixedly provided on the partition.

[0010] Preferably, a slide plate slidably connected to the two movable pole plates is fixedly provided at the bottom of the box body, a lower slide rail is fixedly provided in the middle of the slide plate, an upper slide rail located between the two ceramic plates is fixedly provided at the bottom of the cover plate, a wheel seat is provided between the upper slide rail and the lower slide rail, a round rod is provided on the wheel seat, the middle part of the round rod is rotatably connected to a roller located in the middle of the wheel seat, and the top and bottom of the roller are slidably connected to the upper slide rail and the lower slide rail respectively.

[0011] Preferably, two ends of the round rod are respectively fixedly connected to the middle of one side opposite to the two movable pole plates.

[0012] Preferably, connection seats are fixedly provided at the connection points between the two output shafts and the two movable pole plates, and two receiving grooves are provided on the side plate, and the two receiving grooves are respectively provided corresponding to the two connection seats.

[0013] Preferably, the two output shafts are interlaced with the side plates, and bearings are fixedly provided at the connection between the side plates and the two output shafts, and the two bearings are respectively located in two receiving grooves. The pressure sensitivity and electrical detection are separated, the pressure sensitive film is exposed to the air, and the capacitor structure is arranged in a sealed cavity surrounded by the pressure sensitive film and the substrate, so as to shield the electromagnetic interference of the capacitor structure from the outside world; the pressure sensitive film deforms with the pressure change, thereby driving the change of the internal air pressure of the sealed cavity, and the change of the air pressure drives the moving plate to move, the moving plate and the corresponding first fixed plate form a first capacitor, and the moving plate and the corresponding second fixed plate form a second capacitor, and the detection of the external pressure can be realized by detecting the change of the capacitance.

[0014] Compared with the prior art, the beneficial effects of the present invention are: separating pressure sensitivity and electrical detection, exposing the pressure sensitive film to the air, and setting the capacitor structure in a box body in a sealed cavity, thereby shielding the electromagnetic interference of the outside world to the capacitor structure; the pressure sensitive film is deformed as the pressure changes, and the internal air pressure of the sealed cavity increases or decreases as the pressure sensitive film is deformed, and the change in air pressure drives the piston in the cylinder to move, driving the movable electrode plate to move toward the first fixed electrode plate or the second fixed electrode plate, the movable electrode plate and the corresponding first fixed electrode plate constitute a first capacitor, and the movable electrode plate and the corresponding second fixed electrode plate constitute a second capacitor, and the detection of external pressure can be achieved by detecting the change in capacitance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a cross-sectional view of the present invention; Figure 2 is a schematic diagram of embodiment 1 of the present invention; Figure 3 is a schematic diagram of embodiment 2 of the present invention; Figure 4 It is a top view of the cover plate and the partition plate of the present invention; Figure 5 is an internal diagram of the box body of the present invention; Figure 6 is a bottom view of the cover plate of the present invention; Figure 7 It is a schematic diagram of the driving structure of the movable plate of the present invention; Figure 8 Schematic diagram of the roller of the present invention.

[0016] In the figure: 1, shell; 2, pressure sensitive membrane; 3, telescopic mechanism; 4, first fixed plate; 5, movable plate; 6, ceramic plate; 7, second fixed plate; 8, bottom plate; 9, box body; 10, side plate; 11, cover plate; 12, partition plate; 13, fixed pad; 14, upper limit block; 15, lower limit block; 16, pipe end; 17, vent pipe; 18, first sealing pad; 19, slide plate; 20, storage groove; 21, bearing; 22, cylinder; 23, rear end cover; 24, front end cover; 25, vent hole; 26, piston; 27, piston cavity; 28, output shaft; 29, connecting seat; 30, lower slide rail; 31, wheel seat; 32, round rod; 33, side slide rail; 34, slider; 35, upper slide rail; 36, sealing cavity; 37, second sealing pad; 38, cavity; 39, roller. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0018] See also Figure 1-8 The present invention provides an electromagnetic interference-proof MEMS pressure sensing element, comprising a shell 1, a pressure-sensitive membrane 2 is arranged on the top of the shell 1, a sealed cavity 36 is opened inside the shell 1, a bottom plate 8 is fixedly arranged at the bottom of the sealed cavity 36, a box body 9 is fixedly arranged on one side of the top of the bottom plate 8, a cover plate 11 is installed on the top of the box body 9, two ceramic plates 6 are fixedly arranged at the bottom of the cover plate 11, a first fixed electrode plate 4 and a second fixed electrode plate 7 are respectively arranged on both sides of the two ceramic plates 6, and the first fixed electrode plate 4 and the second fixed electrode plate 7 are fixedly connected to the cover plate 11, side slide rails 33 are arranged on both sides of the bottom of the box body 9, sliders 34 are slidably connected to the two side slide rails 33, and the two sliders 34 are fixedly connected to the moving electrode 5, a side plate 10 is fixedly connected to one side of the box body 9, and two telescopic mechanisms 3 are fixedly installed on the side plate 10; When in use, the pressure sensitive membrane 2 is preferably made of single crystal silicon, and the thickness is preferably 10um-30um. The pressure sensitive membrane 2 deforms as the pressure changes, and the deformation is specifically convex or concave. As the pressure sensitive membrane 2 deforms, the size of the sealed cavity 36 changes, thereby changing the internal air pressure of the sealed cavity 36. The pressure sensitive membrane 2 convexes to reduce the internal air pressure of the sealed cavity 36, and the pressure sensitive membrane 2 concave to increase the internal air pressure of the sealed cavity 36. The two telescopic mechanisms 3 are driven by the change in air pressure, and the two movable plates 5 are driven to move by the two telescopic mechanisms 3, so that the movable plate 5 moves toward the first fixed plate 4 or the second fixed plate 7. The external pressure is detected by the change in capacitance, and the pressure sensitive membrane 2 is connected to the ground potential, which not only realizes the detection of the external pressure, but also shields the external electromagnetic interference outside the electrical part, so as to achieve the purpose of improving the accuracy of the MEMS pressure sensor.

[0019] The two telescopic mechanisms 3 each include a cylinder 22, one end of the cylinder 22 is fixedly connected to a front end cover 24, the other end of the cylinder 22 is fixedly connected to a rear end cover 23, a vent hole 25 connected to the cylinder 22 is provided at the top of the rear end tube, the vent hole 25 is fixedly connected to a vent pipe 17, a piston cavity 27 is provided in the cylinder 22, a piston 26 is slidably connected in the piston cavity 27, one end of the piston 26 is fixedly connected to an output shaft 28, and the ends of the two output shafts 28 that are away from the piston 26 pass through the front end cover 24 and are respectively connected to the two movable plates 5; When in use, the internal air pressure of the sealed cavity 36 decreases, driving the piston 26 to move toward the rear end cover 23, driving the output shaft 28 to be retracted into the cylinder 22, and driving the movable pole plate 5 to move toward the first fixed pole plate 4. The internal air pressure of the sealed cavity 36 increases, driving the piston 26 to move toward the front end cover 24, driving the output shaft 28 to move out of the cylinder 22, and driving the movable pole plate 5 to move toward the second fixed pole plate 7.

[0020] A first sealing gasket 18 is fixedly provided at the connection between the outer side of the top of the shell 1 and the pressure sensitive membrane 2, and a second sealing gasket 37 is fixedly provided at the connection between the box body 9 and the cover plate 11 and at the connection between the side plate 10 and the cover plate 11. The first sealing gasket 18 seals the sealing cavity 36, and the second sealing gasket 37 seals the inner space of the box body 9.

[0021] The bottom of the pressure sensitive membrane 2 is fixedly connected with a fixing pad 13 , the bottom of the fixing pad 13 is fixedly connected with an upper limit block 14 , and the top of the cover plate 11 is fixedly connected with a lower limit block 15 , and the pressure sensitive membrane 2 is limited by the upper limit block 14 and the lower limit block 15 .

[0022] The two movable pole plates 5 are respectively arranged corresponding to the two ceramic plates 6, and the first fixed pole plate 4 and the second fixed pole plate 7 connected to the movable pole plate 5 and the corresponding ceramic plate 6 are arranged correspondingly, the movable pole plate 5 and the corresponding first fixed pole plate 4 constitute a first capacitor, and the movable pole plate 5 and the corresponding second fixed pole plate 7 constitute a second capacitor; when in use, the movable pole plate 5 and the corresponding first fixed pole plate 4 constitute a first capacitor, and the movable pole plate 5 and the corresponding second fixed pole plate 7 constitute a second capacitor, and the external pressure can be detected by detecting the change of the capacitance.

[0023] A partition 12 is fixedly provided on the top of one side of the box body 9, a cavity 38 is separated inside the shell 1 by the box body 9 and the partition 12, two telescopic mechanisms 3 are located inside the cavity 38, the top ends of the two ventilation pipes 17 are fixedly connected to the pipe ends 16, and the two pipe ends 16 are fixedly provided on the partition 12, a slide plate 19 slidably connected to the two movable pole plates 5 is fixedly provided at the bottom of the box body 9, a lower slide rail 30 is fixedly provided in the middle of the slide plate 19, an upper slide rail 35 located between the two ceramic plates 6 is fixedly provided at the bottom of the cover plate 11, a wheel seat 31 is provided between the upper slide rail 35 and the lower slide rail 30, and the wheel seat 31 is provided between the upper slide rail 35 and the lower slide rail 30. A round rod 32 is provided on the seat 31, and the middle part of the round rod 32 is rotatably connected to a roller 39 located in the middle part of the wheel seat 31. The top and bottom of the roller 39 are slidably connected to the upper slide rail 35 and the lower slide rail 30 respectively, and the two ends of the round rod 32 are fixedly connected to the middle part of the opposite side of the two moving pole plates 5 respectively; when in use, the roller 39 slides between the upper slide rail 35 and the lower slide rail 30, and the wheel seat 31 is connected to one side of the two moving pole plates 5 through the round rod 32, and the other side of the two moving pole plates 5 slides along the side slide rail 33 through the slider 34, and the friction resistance is small, which facilitates the displacement of the two moving pole plates 5.

[0024] A connecting seat 29 is fixedly provided at the connection between the two output shafts 28 and the two movable pole plates 5. Two receiving grooves 20 are provided on the side plate 10. The two receiving grooves 20 are respectively arranged corresponding to the two connecting seats 29. The two output shafts 28 are interlaced and connected with the side plate 10. A bearing 21 is fixedly provided at the connection between the side plate 10 and the two output shafts 28. The two bearings 21 are respectively located in the two receiving grooves 20. When in use, when the movable pole plate 5 moves to the bottom of the first fixed pole plate 4, the connecting seat 29 is received in the receiving groove 20, and the bearing 21 reduces the friction resistance of the telescopic activity of the output shaft 28, so as to facilitate the displacement of the two movable pole plates 5.

[0025] Embodiment 1: The external pressure decreases and causes the pressure sensitive membrane 2 to convex. The convexity of the pressure sensitive membrane 2 reduces the internal air pressure of the sealed cavity 36. The reduced internal air pressure of the sealed cavity 36 drives the piston 26 to move toward the rear end cover 23, drives the output shaft 28 to be retracted into the cylinder 22, and drives the movable electrode plate 5 to move toward the first fixed electrode plate 4. The movable electrode plate 5 and the corresponding first fixed electrode plate 4 constitute a first capacitor. The external pressure can be detected by detecting the change in capacitance. As the external pressure decreases, the convex distance of the pressure sensitive membrane 2 increases, the internal air pressure of the sealed cavity 36 decreases, the piston 26 moves toward the rear end cover 23, the area facing the movable electrode plate 5 and the first fixed electrode plate 4 increases, and the capacitance of the first capacitor increases. Therefore, it is concluded that the smaller the external pressure, the larger the capacitance of the first capacitor.

[0026] Embodiment 2: The increase of external pressure makes the pressure sensitive membrane 2 concave, and the concave pressure sensitive membrane 2 makes the internal air pressure of the sealed cavity 36 increase. The increase of the internal air pressure of the sealed cavity 36 drives the piston 26 to move toward the front end cover 24, drives the output shaft 28 to move out of the cylinder 22, and drives the movable electrode plate 5 to move toward the second fixed electrode plate 7. The movable electrode plate 5 and the corresponding second fixed electrode plate 7 constitute a second capacitor. By detecting the change of capacitance, the detection of the external pressure can be realized; as the external pressure increases, the concave distance of the pressure sensitive membrane 2 increases, the internal air pressure of the sealed cavity 36 increases, the piston 26 moves toward the front end cover 24, the area facing the movable electrode plate 5 and the second fixed electrode plate 7 increases, and the capacitance of the second capacitor increases. Therefore, it is concluded that the greater the external pressure, the greater the capacitance of the second capacitor.

[0027] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A MEMS pressure sensing element for preventing electromagnetic interference, comprising a housing (1), characterized in that: A pressure sensitive membrane (2) is arranged on the top of the shell (1), a sealed cavity (36) is provided inside the shell (1), a bottom plate (8) is fixedly arranged on the bottom of the sealed cavity (36), a box body (9) is fixedly arranged on one side of the top of the bottom plate (8), a cover plate (11) is installed on the top of the box body (9), two ceramic plates (6) are fixedly arranged on the bottom of the cover plate (11), a first fixed electrode plate (4) and a second fixed electrode plate (7) are respectively arranged on both sides of the two ceramic plates (6), and the first fixed electrode plate (4) and the second fixed electrode plate (7) are fixedly connected to the cover plate (11), side slide rails (33) are arranged on both sides of the bottom of the box body (9), sliders (34) are slidably connected to the two side slide rails (33), and the two sliders (34) are fixedly connected to the moving electrode plate (5), a side plate (10) is fixedly connected to one side of the box body (9), and two telescopic mechanisms (3) are fixedly installed on the side plate (10); The two telescopic mechanisms (3) each comprise a cylinder (22), one end of the cylinder (22) being fixedly connected to a front end cover (24), the other end of the cylinder (22) being fixedly connected to a rear end cover (23), a vent hole (25) communicating with the cylinder (22) being provided at the top of the rear end tube, the vent hole (25) being fixedly connected to a vent pipe (17), a piston cavity (27) being provided in the cylinder (22), a piston (26) being slidably connected in the piston cavity (27), one end of the piston (26) being fixedly connected to an output shaft (28), and the ends of the two output shafts (28) facing away from the piston (26) passing through the front end cover (24) and being respectively connected to the two movable pole plates (5).

2. The MEMS pressure sensor element for electromagnetic interference prevention according to claim 1, characterized in that: A first sealing gasket (18) is fixedly provided at the connection between the outer side of the top of the shell (1) and the pressure sensitive membrane (2), and a second sealing gasket (37) is fixedly provided at the connection between the box body (9) and the cover plate (11) and at the connection between the side plate (10) and the cover plate (11).

3. The MEMS pressure sensor element for electromagnetic interference prevention according to claim 1, characterized in that: The bottom of the pressure sensitive membrane (2) is fixedly connected to a fixing pad (13), the bottom of the fixing pad (13) is fixedly connected to an upper limit block (14), and the top of the cover plate (11) is fixedly connected to a lower limit block (15).

4. The MEMS pressure sensor element for electromagnetic interference prevention according to claim 1, characterized in that: The two movable pole plates (5) are respectively arranged corresponding to the two ceramic plates (6); the movable pole plate (5) is arranged corresponding to a first fixed pole plate (4) and a second fixed pole plate (7) connected to the corresponding ceramic plate (6); the movable pole plate (5) and the corresponding first fixed pole plate (4) form a first capacitor; and the movable pole plate (5) and the corresponding second fixed pole plate (7) form a second capacitor.

5. The MEMS pressure sensor element for preventing electromagnetic interference according to claim 1, characterized in that: A partition (12) is fixedly arranged on the top of one side of the box body (9); a cavity (38) is formed inside the shell (1) by the box body (9) and the partition (12); the two telescopic mechanisms (3) are located inside the cavity (38); the top ends of the two ventilation pipes (17) are fixedly connected to pipe ends (16); and the two pipe ends (16) are fixedly arranged on the partition (12).

6. The MEMS pressure sensor element for electromagnetic interference prevention according to claim 1, characterized in that: A slide plate (19) slidably connected to the two movable pole plates (5) is fixedly provided at the bottom of the box body (9), a lower rail (30) is fixedly provided in the middle of the slide plate (19), an upper rail (35) located between the two ceramic plates (6) is fixedly provided at the bottom of the cover plate (11), a wheel seat (31) is provided between the upper rail (35) and the lower rail (30), a round rod (32) is provided on the wheel seat (31), a roller (39) located in the middle of the wheel seat (31) is rotatably connected to the middle of the round rod (32), and the top and bottom of the roller (39) are slidably connected to the upper rail (35) and the lower rail (30) respectively.

7. The MEMS pressure sensor element for preventing electromagnetic interference according to claim 6, characterized in that: Both ends of the round rod (32) are respectively fixedly connected to the middle of one side opposite to the two movable pole plates (5).

8. The MEMS pressure sensor element for preventing electromagnetic interference according to claim 1, characterized in that: A connection seat (29) is fixedly provided at the connection points between the two output shafts (28) and the two movable pole plates (5), and two receiving grooves (20) are provided on the side plate (10), and the two receiving grooves (20) are respectively provided corresponding to the two connection seats (29).

9. The MEMS pressure sensor element for preventing electromagnetic interference according to claim 8, characterized in that: The two output shafts (28) are interlacedly connected with the side plate (10), and a bearing (21) is fixedly provided at the connection between the side plate (10) and the two output shafts (28), and the two bearings (21) are respectively located in the two receiving grooves (20).

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