A MEMS pressure sensing element with anti-electromagnetic interference

Abstract

The present invention relates to the field of sensors, and specifically to an electromagnetic interference-proof MEMS pressure sensing element, comprising a shell, a pressure-sensitive membrane provided on the top of the shell, and a sealed cavity provided inside the shell. The present invention separates pressure sensitivity and electrical detection, exposes the pressure-sensitive membrane to the air, and arranges a capacitor structure in a box body within the sealed cavity, thereby shielding the capacitor structure from external electromagnetic interference; the pressure-sensitive membrane deforms as pressure changes, thereby driving changes in the internal air pressure of the sealed cavity, and the change in air pressure drives the movement of a movable plate, the movable plate and the corresponding first fixed plate forming a first capacitor, and the movable plate and the corresponding second fixed plate forming a second capacitor, and detection of external pressure can be achieved by detecting changes in capacitance. The movable plate is non-contact with the pressure-sensitive membrane, thereby avoiding the problem of the movable plate affecting the bending deformation of the pressure-sensitive membrane in traditional capacitive MEMS pressure sensors.

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 sensors are classified into two types: piezoresistive and capacitive. Both types involve exposing a pressure-sensitive film to air. This film responds sensitively to external air pressure and is typically used as an electrical capacitor plate or resistor. Because it must be exposed to air and cannot be placed in a closed electrical cavity, external electromagnetic interference can affect the output of the MEMS pressure sensor.

[0003] Existing capacitive MEMS pressure sensors mostly use a single capacitance 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 this capacitance change. Capacitive MEMS pressure sensors generally use a pressure-sensitive film to drive the movable plate up and down, thereby changing the distance between the movable plate and the fixed plate, and the capacitance changes accordingly. The capacitance is used to detect changes in external pressure. When the pressure-sensitive film drives the movable plate up and down, the pressure-sensitive film first needs to overcome the weight of the movable 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 present invention aims to provide a MEMS pressure sensor element that is resistant to electromagnetic interference. This solves the problem of capacitive MEMS pressure sensors, as discussed in the background art, which typically use a pressure-sensitive film to drive a movable plate up and down, thereby changing the distance between the movable plate and the fixed plate, and consequently changing the capacitance, to detect external pressure changes. When the pressure-sensitive film drives the movable plate up and down, it must first overcome the weight of the movable plate, which affects the bending deformation of the pressure-sensitive film and thus reduces the sensing accuracy of the capacitive MEMS pressure sensor.

[0005] To achieve the above-mentioned object, the present invention provides the following technical solution: an electromagnetic interference-proof MEMS pressure sensing element, comprising a shell, a pressure-sensitive membrane is provided on the top of the shell, a sealed cavity is opened inside the shell, a bottom plate is fixedly provided at the bottom of the sealed cavity, a box body is fixedly provided 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 provided at the bottom of the cover plate, a first fixed electrode plate and a second fixed electrode plate are respectively provided 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 rails are provided on both sides of the bottom of the box body, sliders are slidably connected to the two side 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;

[0006] 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 the two movable plates.

[0007] 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.

[0008] 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.

[0009] Preferably, the two movable pole plates are respectively arranged corresponding to the two ceramic plates, and the first fixed pole plate and the second fixed pole plate connected to the corresponding ceramic plates are arranged correspondingly, 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.

[0010] 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.

[0011] Preferably, a slide plate is fixedly provided at the bottom of the box body and is slidably connected to the two movable pole plates, 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.

[0012] Preferably, both ends of the round rod are fixedly connected to the middle of one side opposite to the two movable plates.

[0013] Preferably, a connecting seat is fixedly provided at the connection 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 connecting seats.

[0014] 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. Pressure sensitivity and electrical detection are separated, the pressure sensitive membrane is exposed to the air, and the capacitor structure is arranged in a sealed cavity surrounded by the pressure sensitive membrane and the substrate, thereby shielding the capacitor structure from external electromagnetic interference; the pressure sensitive membrane deforms with changes in pressure, thereby driving changes in the internal air pressure of the sealed cavity, and the change in air pressure drives the movable plate to move. The movable plate and the corresponding first fixed plate form a first capacitor, and the movable plate and the corresponding second fixed plate form a second capacitor. By detecting the change in capacitance, the external pressure can be detected.

[0015] Compared with the prior art, the beneficial effects of the present invention are: separating pressure sensitivity and electrical detection, exposing the pressure sensitive membrane to the air, and setting the capacitor structure in a box body in a sealed cavity, thereby shielding the external electromagnetic interference to the capacitor structure; the pressure sensitive membrane deforms as the pressure changes, and as the pressure sensitive membrane deforms, the internal air pressure of the sealed cavity increases or decreases. 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. By detecting the change in capacitance, the external pressure can be detected. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a cross-sectional view of the present invention;

[0017] Figure 2 Schematic diagram of Example 1 of the present invention;

[0018] Figure 3 Schematic diagram of embodiment 2 of the present invention;

[0019] Figure 4 A top view of the cover plate and the partition plate of the present invention;

[0020] Figure 5 It is an internal diagram of the box body of the present invention;

[0021] Figure 6 is a bottom view of the cover plate of the present invention;

[0022] Figure 7 Schematic diagram of the driving structure of the movable plate of the present invention;

[0023] Figure 8 Schematic diagram of the roller of the present invention.

[0024] In the figure: 1. shell; 2. pressure sensitive membrane; 3. telescopic mechanism; 4. first fixed electrode plate; 5. movable electrode plate; 6. ceramic plate; 7. second fixed electrode 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 gasket; 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 chamber; 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 gasket; 38. cavity; 39. roller. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0026] See also Figure 1-8 The present invention provides a MEMS pressure sensing element for preventing electromagnetic interference, comprising a shell 1, a pressure-sensitive membrane 2 being provided on the top of the shell 1, a sealed cavity 36 being opened inside the shell 1, a bottom plate 8 being fixedly provided at the bottom of the sealed cavity 36, a box body 9 being fixedly provided on one side of the top of the bottom plate 8, a cover plate 11 being installed on the top of the box body 9, two ceramic plates 6 being fixedly provided at the bottom of the cover plate 11, a first fixed electrode plate 4 and a second fixed electrode plate 7 being provided on both sides of the two ceramic plates 6, and the first fixed electrode plate 4 and the second fixed electrode plate 7 being fixedly connected to the cover plate 11, side rails 33 being provided on both sides of the bottom of the box body 9, sliders 34 being slidably connected to the two side rails 33, and the two sliders 34 being fixedly connected to the movable electrode plate 5, a side plate 10 being fixedly connected to one side of the box body 9, and two telescopic mechanisms 3 being fixedly installed on the side plate 10;

[0027] During use, the pressure sensitive membrane 2 is preferably made of single crystal silicon and has a thickness of preferably 10um-30um. The pressure sensitive membrane 2 deforms as 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 upward convexity of the pressure sensitive membrane 2 reduces the internal air pressure of the sealed cavity 36, and the concaveness of the pressure sensitive membrane 2 increases 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 by the two telescopic mechanisms 3 to move, so that the movable plates 5 move toward the first fixed plate 4 or the second fixed plate 7. The external pressure is detected by the change in capacitance. The pressure sensitive membrane 2 is connected to the ground potential, which not only realizes the detection of external pressure, but also shields external electromagnetic interference from the electrical part, thereby achieving the purpose of improving the accuracy of the MEMS pressure sensor.

[0028] The two telescopic mechanisms 3 each include a cylinder 22, one end of which is fixedly connected to a front end cover 24, and the other end of which is fixedly connected to a rear end cover 23. A vent hole 25 communicating with the cylinder 22 is defined at the top of the rear end tube, and the vent hole 25 is fixedly connected to the vent pipe 17. A piston chamber 27 is defined within the cylinder 22, and a piston 26 is slidably connected within the piston chamber 27. One end of the piston 26 is fixedly connected to an output shaft 28. The ends of the two output shafts 28 facing away from the piston 26 pass through the front end cover 24 and are respectively connected to the two movable plates 5.

[0029] During 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 electrode plate 5 to move toward the first fixed electrode 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 electrode plate 5 to move toward the second fixed electrode plate 7.

[0030] 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.

[0031] 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. The pressure sensitive membrane 2 is limited by the upper limit block 14 and the lower limit block 15.

[0032] 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. By detecting the change in capacitance, the external pressure can be detected.

[0033] 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. The two telescopic mechanisms 3 are located inside the cavity 38. The top ends of the two vent pipes 17 are fixedly connected to the tube ends 16. The two tube ends 16 are fixedly provided on the partition 12. The bottom of the box body 9 is fixedly provided with a slide 19 that is slidably connected to the two movable plates 5. The middle of the slide 19 is fixedly provided with a lower slide rail 30. The bottom of the cover plate 11 is fixedly provided with an upper slide rail 35 located between the two ceramic plates 6. A 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 the roller 39 located in the middle 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 movable pole plates 5 respectively; when in use, the roller 39 slides between the upper slide rail 35 and the lower rail 30, and the wheel seat 31 is connected to one side of the two movable pole plates 5 through the round rod 32, and the other side of the two movable 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 movable pole plates 5.

[0034] The connections between the two output shafts 28 and the two movable pole plates 5 are fixedly provided with connecting seats 29. Two receiving grooves 20 are provided on the side plate 10. The two receiving grooves 20 are respectively provided corresponding to the two connecting seats 29. The two output shafts 28 are interlaced with the side plate 10. Bearings 21 are fixedly provided at the connections 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 retracted into the receiving groove 20, and the bearings 21 reduce the friction resistance of the telescopic activity of the output shaft 28, thereby facilitating the displacement of the two movable pole plates 5.

[0035] Example 1: The decrease in external pressure causes the pressure-sensitive membrane 2 to bulge upward, and the bulging of the pressure-sensitive membrane 2 reduces the internal air pressure of the sealed cavity 36. The reduction in the 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 5 to move toward the first fixed electrode 4. The movable electrode 5 and the corresponding first fixed electrode 4 form a first capacitor. By detecting the change in capacitance, the external pressure can be detected; as the external pressure decreases, the bulging 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 5 and the first fixed electrode 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.

[0036] Example 2: The increase in external pressure causes the pressure-sensitive membrane 2 to concave, and the concave pressure-sensitive membrane 2 increases the internal air pressure of the sealed cavity 36. The increase in 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 form a second capacitor. By detecting the change in capacitance, the external pressure can be detected; 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.

[0037] 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 scope of protection 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 provided on the top of the shell (1), a sealed cavity (36) is provided inside the shell (1), a bottom plate (8) is fixedly provided on the bottom of the sealed cavity (36), a box body (9) is fixedly provided 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 provided on the bottom of the cover plate (11), a first fixed electrode plate (4) and a second fixed electrode plate (7) are provided 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 rails (33) are provided on both sides of the bottom of the box body (9), sliders (34) are slidably connected to the two side rails (33), and the two sliders (34) are fixedly connected to the movable 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); 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 top of the rear end cover is provided with a vent hole (25) connected to the cylinder (22), 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) facing away from the piston (26) pass through the front end cover (24) and are respectively connected to the two movable plates (5).

2. The MEMS pressure sensing element 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 sensing element with electromagnetic interference protection 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 with electromagnetic interference protection 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 the first fixed pole plate (4) and the 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 sensing element with electromagnetic interference protection according to claim 1, characterized in that: A partition (12) is fixedly provided on the top of one side of the box body (9), and 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), and the top ends of the two ventilation pipes (17) are fixedly connected to pipe ends (16), and the two pipe ends (16) are fixedly provided on the partition (12).

6. The MEMS pressure sensing element with electromagnetic interference protection according to claim 1, characterized in that: A slide plate (19) is fixedly provided at the bottom of the box body (9) and is slidably connected to the two movable pole plates (5). 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). The middle of the round rod (32) is rotatably connected to a roller (39) located in the middle of the wheel seat (31). 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 sensing element with electromagnetic interference protection according to claim 6, characterized in that: The two ends of the round rod (32) are respectively fixedly connected to the middle portions of the opposite sides of the two movable pole plates (5).

8. The MEMS pressure sensing element with electromagnetic interference protection according to claim 1, characterized in that: A connecting 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 connecting seats (29).

9. The MEMS pressure sensing element with electromagnetic interference protection according to claim 8, characterized in that: The two output shafts (28) are connected to the side plate (10) through insertion, 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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