Accelerometer

Abstract

The invention provides an accelerometer. The accelerometer comprises a base, a sensing unit arranged on the base and two anchor points for fixing the base, the sensing unit comprises an outer coupling unit which is stacked on the base; the number of the seesaw structures is two, the two seesaw structures are arranged on the inner side of the outer coupling unit, and the two seesaw structures are arranged in a central symmetry mode; the number of the inner side coupling units is two, the inner side coupling units are arranged on the inner side of the outer side coupling unit, and the two inner side coupling units are symmetrically arranged relative to a connecting line of the two anchor points; the test mass block is fixed on the outer side coupling unit and / or the inner side coupling unit; the accelerometer further comprises out-of-plane detection devices, and the out-of-plane detection devices are respectively arranged in a base area directly facing the outer side coupling unit and a base area directly facing the inner side coupling unit. According to the accelerometer, all displacement of the out-of-plane detection capacitor can be changed into linear displacement, and the linearity of acceleration detection is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of micromechanical structures, and in particular to an accelerometer. Background Art

[0002] An accelerometer is an instrument that measures the linear acceleration of a vehicle. Figure 1 As shown, the seesaw type out-of-plane accelerometer mainly includes a base (not shown), a sensor unit arranged on the base, and an anchor point 201 fixed to the base and located at the same level as the sensor unit. The sensor unit mainly includes a torsion spring 202 fixed between the anchor points and a test mass block 203. When the accelerometer is subjected to out-of-plane (Z direction) acceleration, the asymmetric test mass block 203 (M1) along the rotation axis 204 drives the torsion spring 202 to rotate around the rotation axis 204, which will cause an out-of-plane displacement in the area 205 corresponding to the capacitor plate. By placing a capacitor plate in the area 205 corresponding to the capacitor plate above or below it to form a differential capacitor, the acceleration change can be obtained by detecting the capacitance change. Figure 2 As shown, due to the asymmetric structure of the accelerometer, that is, its mass center 206 is not located on the rotation axis 204, it will produce in-plane (X direction) swing under the action of X direction acceleration.

[0003] In response to the above problems, Murata's patent application (US20200018777A) discloses a structure using two seesaws, in which the main body of the rotating test mass is on the seesaw structure, and a rigid body is added to the outside as a coupling structure, and as a linear mass, when the out-of-plane acceleration acts, the linear mass moves linearly in the out-of-plane direction. This structure sets the detection plate far away from the axis of rotation, ensures the gain of the rotation to the capacitance change, eliminates the swing along the X-axis direction (IP1 axis direction), but cannot suppress the rotation of the two seesaws in the same direction around the Z axis (OP axis) and the rotation in the same direction around the X axis (IP1 axis).

[0004] ADI's patent application (US20200132716A1) discloses a multi-axis accelerometer whose out-of-plane accelerometer adopts a butterfly structure, that is, the inner coupling structure realizes the motion coupling of the two seesaw structures, which can suppress the in-plane rotation of a single seesaw structure and the same-direction rotation around the rotation axis. Compared with Murata's structure, it does not have a linear test mass for linear motion of the Z axis as an outer coupling structure, so its ability to suppress the reverse motion of the two seesaw structures around the Z axis is poor.

[0005] In summary, the accelerometer in the related art cannot convert all the displacement of the out-of-plane capacitor substrate into linear displacement, which results in poor linearity of acceleration detection of the accelerometer. Summary of the invention

[0006] An object of the present invention is to provide an accelerometer with improved linearity of acceleration detection.

[0007] In order to achieve the above object, an embodiment of the present invention provides an accelerometer, which includes a base, a sensor unit arranged on the base, and two anchor points that fix the base and are located at the same level as the sensor unit, and the two anchor points are arranged opposite to each other at intervals; the sensor unit includes:

[0008] An outer coupling unit, the outer coupling unit is stacked on the base;

[0009] A seesaw structure, wherein the seesaw structure comprises two seesaw structures arranged at intervals on the inner side of the outer coupling unit, and the two seesaw structures are arranged symmetrically to the center;

[0010] An inner coupling unit, wherein the inner coupling units include two inner coupling units and are respectively arranged on the inner side of the outer coupling unit, the two inner coupling units are symmetrically arranged about the connection line of the two anchor points and are respectively located on opposite sides of the anchor points; each of the seesaw structures is elastically connected to the outer coupling unit, the two inner coupling units and another seesaw structure;

[0011] a proof mass, the proof mass being fixed to the outer coupling unit and / or the inner coupling unit; and

[0012] The accelerometer also includes an out-of-plane detection device, which is respectively arranged in a base area opposite to the outer coupling unit and a base area opposite to the inner coupling unit. The out-of-plane detection device uses capacitive detection to detect the linear movement generated by the outer coupling unit and / or the inner coupling unit along the first direction.

[0013] Preferably, the seesaw structure is arranged in a nested manner.

[0014] Preferably, the two anchor points are both located in the middle area of ​​the outer coupling unit.

[0015] Preferably, the outer coupling unit includes a supporting portion in the form of a rectangular ring, two counterweight portions spaced apart from each other, and two connecting portions respectively connecting the two counterweight portions to opposite sides of the supporting portion, and the counterweight portions are spaced apart from the supporting portion and the seesaw structure, respectively; the counterweight portions also serve as a test mass block.

[0016] Preferably, each of the seesaw structures includes two torsion springs spaced apart from each other and elastic members respectively fixed to the two torsion springs, the ends of the two torsion springs close to each other are respectively fixed to the corresponding anchor points, and the ends of the two torsion springs far away from each other are respectively connected to the elastic members; the elastic members in each of the seesaw structures are respectively elastically connected to the outer coupling unit, the two inner coupling units and the elastic member in another seesaw structure, and each of the seesaw structures is respectively spaced apart from the outer coupling unit, the two inner coupling units and the elastic member in another seesaw structure.

[0017] Preferably, the elastic member in each of the seesaw structures includes a first elastic beam and a second elastic beam respectively fixed at opposite sides of the connecting portion, a rotating arm fixed to an end of the first elastic beam away from the connecting portion, a first extending portion fixed to an end of the second elastic beam away from the connecting portion, a fixing portion extending from the rotating arm to the first extending portion, a second extending portion extending from the rotating arm toward the first extending portion, a third elastic beam connected to an end of the rotating arm away from the first elastic beam and a side of one of the inner coupling units away from the first elastic beam, a bent portion formed by the first extending portion extending away from an end of the second elastic beam around the other inner coupling unit, and a third elastic beam connected to the bent portion away from the first elastic beam. One end of an extension portion and the corresponding inner coupling unit are away from a fourth elastic beam on one side of the second elastic beam and a fifth elastic beam connected to the bending portion, the second extension portion is spaced apart from the bending portion and the fixed portion respectively, and the fifth elastic beam is located between the two anchor points and spaced apart from the anchor points; the ends of the two torsion springs in each seesaw structure that are away from each other are respectively connected to the corresponding rotating arm and the first extension portion, and are respectively spaced apart from the fixed portion, the second extension portion and the bending portion, the ends of the two torsion springs in the seesaw structure that are close to each other are respectively fixed to the corresponding anchor points, and the fifth elastic beam in each seesaw structure is connected to the fifth elastic beam in another seesaw structure.

[0018] Preferably, one end of each anchor point away from another anchor point is connected to the corresponding two torsion springs through an extension arm, and the extension arm is located between the corresponding second extension portion and the bending portion, and is spaced apart from the corresponding second extension portion and the bending portion respectively.

[0019] Preferably, the base includes a base and a cavity cover fixed to the base and together enclosing a receiving space, and the sensing unit is arranged in the receiving space; the out-of-plane detection device includes a first capacitor plate fixed to an area of ​​the base or an area of ​​the cavity cover opposite to the outer coupling unit and a second capacitor plate fixed to an area of ​​the base or an area of ​​the cavity cover opposite to the inner coupling unit.

[0020] Preferably, the accelerometer also includes an in-plane detection device, which is arranged on the outer coupling unit, and the in-plane detection device uses capacitive detection to detect the linear movement generated by the outer coupling unit along the second direction, and / or to detect the linear movement generated by the outer coupling unit along the third direction; the first direction, the second direction and the third direction are perpendicular to each other.

[0021] Preferably, the in-plane detection device includes a plurality of X-axis in-plane detection units for detecting linear motion of the outer coupling unit along the second direction, and / or a plurality of Y-axis in-plane detection units for detecting linear motion of the outer coupling unit along the third direction.

[0022] Compared with the related art, the overall structure of the accelerometer in the present invention is supported by two relative seesaw structures, and the outer coupling structure is coupled to the outer sides of the two seesaw structures, and the inner coupling structure is coupled to the inner side of the seesaw structure, and the two seesaw structures are arranged symmetrically with respect to the center, and the two inner coupling units are arranged symmetrically about the connecting line of the two anchor points and are respectively located on the opposite sides of the anchor points, thus suppressing the rotation of the seesaw structure on the plane around the axis perpendicular to the plane to a certain extent, reducing the cross-coupling of the seesaw structure, and the inspection mass blocks of the accelerometer are distributed on the outer coupling units and / or the inner coupling units, and when the acceleration perpendicular to the plane axis arrives, the two sides of the seesaw structure The outer coupling unit and the inner coupling unit move differentially relative to the base, causing the detection capacitor in the out-of-plane detection device to form a parallel plate capacitor with the sensing unit and undergo a differential change. This is equivalent to, when subjected to out-of-plane acceleration, the mass of the outer coupling unit is larger and will move in the direction of the acceleration, while the mass of the inner coupling unit is smaller and will move in the opposite direction of the acceleration. In this way, the capacitance corresponding to the outer coupling unit will increase, while the capacitance corresponding to the inner coupling unit will decrease, thereby forming a differential capacitance. The acceleration perpendicular to the plane axis can be detected by detecting the change in capacitance. This structure converts all displacements of the out-of-plane detected capacitance into linear displacements, greatly improving the linearity of acceleration detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0024] Figure 1 A schematic diagram of the structure of an accelerometer provided for related technologies;

[0025] Figure 2 A schematic diagram of the motion state of an accelerometer provided for related technologies;

[0026] Figure 3 A schematic diagram of the structure of an accelerometer provided in Embodiment 1 of the present invention;

[0027] Figure 4 A schematic diagram of the detection mode of the accelerometer provided in the first embodiment of the present invention;

[0028] Figure 5 A schematic diagram of a modular cross-section of an accelerometer provided in Embodiment 1 of the present invention;

[0029] Figure 6 This is a schematic diagram of the structure of an accelerometer provided in Embodiment 2 of the present invention.

[0030] In the figure, 100, accelerometer; 1, sensing unit; 11, outer coupling unit; 111, supporting part; 112, counterweight part; 113, connecting part; 12, seesaw structure; 121, torsion spring; 122, elastic member; 1221, first elastic beam; 1222, second elastic beam; 1223, rotating arm; 1224, first extension part; 1225, fixing part; 1226, second extension part; 1227, third elastic beam; 1228, bending part; 1229, fourth elastic beam; 12210, fifth elastic beam; 13, inner coupling unit; 2, anchor point; 21, extension arm; 3, in-plane detection device; 31, X-axis in-plane detection unit; 32, Y-axis in-plane detection unit; 4, base; 40, accommodating space; 41, substrate; 42, cavity cover; 5, first capacitor plate; 6, second capacitor plate. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Embodiment 1

[0033] Figure 3 The Z axis is the first direction, the X axis is the second direction, the Y axis is the third direction, and the dotted box is the capacitor plate area on the corresponding base 4; Figure 3 As shown, an embodiment of the present invention provides an accelerometer 100, which includes a base 4, a sensor unit 1 arranged on the base 4, and two anchor points 2 fixed to the base 4 and located at the same level as the sensor unit 1, and the two anchor points 2 are arranged opposite to each other and spaced apart.

[0034] The base 4 includes a substrate 41 and a cavity cover 42 which is disposed on the substrate 41 and together surrounds a receiving space; the sensor unit 1 is disposed in the receiving space 40 .

[0035] Specifically, the sensing unit 1 includes an outer coupling unit 11 , a seesaw structure 12 , an inner coupling unit 13 and a proof mass block.

[0036] Among them, the outer coupling unit 11 is stacked on the base 4; the seesaw structure 12 includes two and is arranged at intervals on the inner side of the outer coupling unit 11, and the two seesaw structures 12 are arranged symmetrically with respect to the center; the inner coupling unit 13 includes two and is arranged on the inner side of the outer coupling unit 11 respectively, and the two inner coupling units 13 are symmetrically arranged about the connection line of the two anchor points 2 and are respectively located on the opposite sides of the anchor points 2; each seesaw structure 12 is elastically connected to the outer coupling unit 11, the two inner coupling units 13 and another seesaw structure 12; the inspection mass block is fixed to the outer coupling unit 11 and / or the inner coupling unit 13.

[0037] The outer coupling unit 11 includes a supporting portion 111 in the form of a rectangular ring, two counterweight portions 112 spaced apart from each other, and two connecting portions 113 respectively connecting the two counterweight portions 112 to opposite sides of the supporting portion 111. The counterweight portions 112 are spaced apart from the supporting portion 111 and the seesaw structure 12 respectively; the counterweight portions 112 also serve as a verification mass block, that is, the counterweight portion 112 is not only a part of the outer coupling unit 11, but also directly serves as a verification mass block.

[0038] In addition, the supporting portion 111 , the weight portion 112 and the connecting portion 113 in the outer coupling unit 11 are also part of the seesaw structure 12 .

[0039] Each seesaw structure 12 includes two torsion springs 121 spaced apart from each other and elastic members 122 respectively fixed to the two torsion springs 121, the ends of the two torsion springs 121 close to each other are respectively fixed to the corresponding anchor points 2, and the ends of the two torsion springs 121 away from each other are respectively connected to the elastic members 122; the elastic members 122 in each seesaw structure 12 are respectively elastically connected to the outer coupling unit 11, the two inner coupling units 13 and the elastic member 122 in another seesaw structure 12, and each seesaw structure 12 is respectively spaced apart from the outer coupling unit 11, the two inner coupling units 13 and the elastic member 122 in another seesaw structure 12.

[0040] The elastic member 122 in each seesaw structure 12 includes a first elastic beam 1221 and a second elastic beam 1222 fixed to opposite sides of the connecting portion 113, a rotating arm 1223 fixed to an end of the first elastic beam 1221 away from the connecting portion 113, a first extending portion 1224 fixed to an end of the second elastic beam 1222 away from the connecting portion 113, a fixing portion 1225 extending from the rotating arm 1223 to the first extending portion 1224, a second extending portion 1226 extending from the rotating arm 1223 toward the first extending portion 1224, a third elastic beam 1227 connected to an end of the rotating arm 1223 away from the first elastic beam 1221 and a side of one of the inner coupling units 13 away from the first elastic beam 1221, a bending portion 1228 formed by bending and extending the end of the first extending portion 1224 away from the second elastic beam 1222 around the other inner coupling unit 13, and a fixing portion 1225 extending from the rotating arm 1223 to the first extending portion 1224. 28 is far away from one end of the first extension portion 1224 and the corresponding inner coupling unit 13, a fourth elastic beam 1229 is far away from one side of the second elastic beam 1222, and a fifth elastic beam 12210 is connected to the bending portion 1228, the second extension portion 1226 is spaced apart from the bending portion 1228 and the fixing portion 1225, and the fifth elastic beam 12210 is located between the two anchor points 2 and spaced apart from the anchor points 2; the ends of the two torsion springs 121 in each seesaw structure 12 that are far away from each other are respectively connected to the corresponding rotating arm 1223 and the first extension portion 1224, and are spaced apart from the fixing portion 1225, the second extension portion 1226 and the bending portion 1228, and the ends of the two torsion springs 121 in the seesaw structure 12 that are close to each other are respectively fixed to the corresponding anchor points 2, and the fifth elastic beam 12210 in each seesaw structure 12 is connected to the fifth elastic beam 12210 in another seesaw structure 12.

[0041] One end of each anchor point 2 away from another anchor point 2 is connected to the corresponding two torsion springs 121 through an extension arm 21. The extension arm 21 is located between the corresponding second extension portion 1226 and the bending portion 1228, and is spaced apart from the corresponding second extension portion 1226 and the bending portion 1228 respectively.

[0042] The seesaw structure 12 in this embodiment is arranged in a nested manner, that is, inserted between the outer coupling unit 11 and the inner coupling unit 13, so that the remaining translation and rotation modes of the seesaw can be suppressed to prevent the influence of angular velocity.

[0043] In this embodiment, the two anchor points 2 are both located in the middle area of ​​the outer coupling unit 11. This structural design can reduce the stress effect during the processing and also reduce the process error.

[0044] The accelerometer 100 also includes an out-of-plane detection device, which is respectively arranged in the base 4 area opposite to the outer coupling unit 11 and the base 4 area opposite to the inner coupling unit 13. The out-of-plane detection device uses capacitive detection to detect the linear movement generated by the outer coupling unit 11 and / or the inner coupling unit 13 along the first direction.

[0045] In this embodiment, the base 4 includes a base 41 and a cavity cover 42 which is fixed to the base 41 and together surrounds a receiving space 40, and the sensor unit 1 is arranged in the receiving space 40; the out-of-plane detection device includes a first capacitor plate 5 fixed to an area of ​​the base 41 or an area of ​​the cavity cover 42 opposite to the outer coupling unit 11 and a second capacitor plate 6 fixed to an area of ​​the base 41 or an area of ​​the cavity cover 42 opposite to the inner coupling unit 13.

[0046] The number of the first capacitor plates 5 is the same as the number of the outer coupling units 11 ; the number of the second capacitor plates 6 is the same as the number of the inner coupling units 13 .

[0047] The detection modes of each axis of the accelerometer 100 in this embodiment are as follows: Figure 4 As shown, Figure 4 a is the X-axis detection mode, b is the Y-axis detection mode, and c is the Z-axis detection mode; the modular cross-section of the accelerometer 100 in this embodiment is as follows Figure 5 As shown, Figure 5 d in the figure is an X-axis cross-sectional view, which shows that the first capacitor plate 5 is arranged in the area of ​​the substrate 41 facing the outer coupling unit 11, and f is a Y-axis cross-sectional view, which shows that the second capacitor plate 6 is arranged in the area of ​​the cavity cover 42 facing the inner coupling unit 13.

[0048] Compared with the related art, the overall structure of the accelerometer 100 in this embodiment is supported by two relative seesaw structures 12, and the outer coupling structure is coupled to the outer sides of the two seesaw structures 12, and the inner coupling structure is coupled to the inner side of the seesaw structure 12, and the two seesaw structures 12 are arranged symmetrically with respect to the center, and the two inner coupling units 13 are arranged symmetrically about the connecting line of the two anchor points 2 and are respectively located on the opposite sides of the anchor points 2, so that the rotation of the seesaw structure 12 on the plane around the line perpendicular to the plane axis (Z axis) is suppressed to a certain extent, and the cross coupling of the seesaw structure 12 is reduced, and the inspection mass blocks of the accelerometer 100 are distributed on the outer coupling unit 11 and / or the inner coupling unit 13. When the acceleration perpendicular to the plane axis arrives, the seesaw The outer coupling unit 11 and the inner coupling unit 13 on both sides of the seesaw structure 12 move differentially relative to the base 4, causing the detection capacitor in the out-of-plane detection device to form a parallel plate capacitor with the sensing unit 1 and undergo a differential change, which is equivalent to, when subjected to out-of-plane acceleration, the mass of the outer coupling unit 11 is larger and will move in the direction of the acceleration, while the mass of the inner coupling unit 13 is smaller and will move in the opposite direction of the acceleration, so that the capacitance corresponding to the outer coupling unit 11 will increase, and the capacitance corresponding to the inner coupling unit 13 will decrease, thereby forming a differential capacitance, and then the acceleration perpendicular to the plane axis can be detected by detecting the change in capacitance. This structure converts all displacements of the capacitance detected out of the plane into linear displacements, greatly improving the linearity of acceleration detection.

[0049] Embodiment 2

[0050] Combination Figure 6 As shown, the accelerometer 100 in this embodiment not only includes various structures of the first embodiment, but also includes an in-plane detection device 3. The in-plane detection device 3 is arranged on the outer coupling unit 11. The in-plane detection device 3 adopts a capacitive detection method to detect the linear movement generated by the outer coupling unit 11 along the second direction, and / or to detect the linear movement generated by the outer coupling unit 11 along the third direction; the first direction, the second direction and the third direction are perpendicular to each other.

[0051] Specifically, the in-plane detection device 3 includes a plurality of X-axis in-plane detection units 31 for detecting the linear motion of the outer coupling unit 11 along the second direction, and / or a plurality of Y-axis in-plane detection units 32 for detecting the linear motion of the outer coupling unit 11 along the third direction. In this embodiment, the in-plane detection device 3 includes a plurality of X-axis in-plane detection units 31 and a plurality of Y-axis in-plane detection units 32.

[0052] The X-axis in-plane detection unit 31 and the Y-axis in-plane detection unit 32 in this embodiment are the same as or similar to the out-of-plane detection device in the first embodiment, and are not described in detail here.

[0053] The accelerometer 100 in this embodiment can directly detect acceleration in three mutually perpendicular directions of the accelerometer 100 by adding an X-axis in-plane detection unit 31 and a Y-axis in-plane detection unit 32, that is, a three-axis capacitive acceleration sensor is formed.

[0054] The above description is only an implementation mode of the present invention. It should be pointed out that, for ordinary technicians in this field, improvements can be made without departing from the creative concept of the present invention, but these all belong to the protection scope of the present invention.

Claims

1. An accelerometer, comprising a base, a sensor unit disposed on the base, and two anchor points fixed to the base and located at the same level as the sensor unit, wherein the two anchor points are disposed opposite to each other and spaced apart; characterized in that: The sensing unit comprises: An outer coupling unit, the outer coupling unit is stacked on the base; A seesaw structure, wherein the seesaw structure comprises two seesaw structures arranged at intervals on the inner side of the outer coupling unit, and the two seesaw structures are arranged symmetrically to the center; An inner coupling unit, wherein the inner coupling units include two inner coupling units and are respectively arranged on the inner side of the outer coupling unit, the two inner coupling units are symmetrically arranged about the connection line of the two anchor points and are respectively located on opposite sides of the anchor points; each of the seesaw structures is elastically connected to the outer coupling unit, the two inner coupling units and another seesaw structure; a proof mass block, wherein the proof mass block is fixed to the outer coupling unit and / or the inner coupling unit; The accelerometer also includes an out-of-plane detection device, which is respectively arranged in a base area opposite to the outer coupling unit and a base area opposite to the inner coupling unit. The out-of-plane detection device uses capacitive detection to detect the linear movement generated by the outer coupling unit and / or the inner coupling unit along the first direction.

2. The accelerometer according to claim 1, wherein: The seesaw structure is arranged in a nested manner.

3. The accelerometer according to claim 1, wherein: The two anchor points are both located in the middle area of ​​the outer coupling unit.

4. The accelerometer according to claim 1, wherein: The outer coupling unit includes a rectangular ring-shaped support portion, two counterweight portions spaced apart from each other, and two connecting portions that respectively connect the two counterweight portions to opposite sides of the support portion, wherein the counterweight portions are spaced apart from the support portion and the seesaw structure, respectively; the counterweight portions also serve as inspection mass blocks.

5. The accelerometer according to claim 4, wherein: Each of the seesaw structures includes two torsion springs spaced apart from each other and elastic members respectively fixed to the two torsion springs, wherein the ends of the two torsion springs close to each other are respectively fixed to the corresponding anchor points, and the ends of the two torsion springs far away from each other are respectively connected to the elastic members; the elastic members in each of the seesaw structures are respectively elastically connected to the outer coupling unit, the two inner coupling units and the elastic member in another seesaw structure, and each of the seesaw structures is respectively spaced apart from the outer coupling unit, the two inner coupling units and the elastic member in another seesaw structure.

6. The accelerometer according to claim 5, wherein: The elastic member in each of the seesaw structures includes a first elastic beam and a second elastic beam respectively fixed at opposite sides of the connecting portion, a rotating arm fixed to an end of the first elastic beam away from the connecting portion, a first extending portion fixed to an end of the second elastic beam away from the connecting portion, a fixing portion extending from the rotating arm to the first extending portion, a second extending portion extending from the rotating arm toward the first extending portion, a third elastic beam connected to an end of the rotating arm away from the first elastic beam and a side of one of the inner coupling units away from the first elastic beam, a bending portion formed by bending and extending the first extending portion away from the second elastic beam around the other inner coupling unit, and a fixing portion connected to the bending portion away from the first extending portion. One end of the extension part and the corresponding inner coupling unit are away from the fourth elastic beam on one side of the second elastic beam and the fifth elastic beam connected to the bending part, the second extension part is respectively spaced apart from the bending part and the fixed part, and the fifth elastic beam is located between the two anchor points and spaced apart from the anchor points; the ends of the two torsion springs in each seesaw structure that are away from each other are respectively connected to the corresponding rotating arm and the first extension part, and are respectively spaced apart from the fixed part, the second extension part and the bending part, the ends of the two torsion springs in the seesaw structure that are close to each other are respectively fixed to the corresponding anchor points, and the fifth elastic beam in each seesaw structure is connected to the fifth elastic beam in another seesaw structure.

7. The accelerometer according to claim 6, wherein: One end of each anchor point away from another anchor point is connected to the corresponding two torsion springs through an extension arm, and the extension arm is located between the corresponding second extension part and the bending part, and is spaced apart from the corresponding second extension part and the bending part respectively.

8. The accelerometer according to claim 1, wherein: The base includes a base and a cavity cover fixed to the base and together enclosing a receiving space, and the sensing unit is arranged in the receiving space; the out-of-plane detection device includes a first capacitor plate fixed to an area of ​​the base or an area of ​​the cavity cover opposite to the outer coupling unit, and a second capacitor plate fixed to an area of ​​the base or an area of ​​the cavity cover opposite to the inner coupling unit.

9. The accelerometer according to claim 1, wherein: The accelerometer also includes an in-plane detection device, which is arranged on the outer coupling unit. The in-plane detection device uses capacitive detection to detect the linear movement generated by the outer coupling unit along the second direction, and / or to detect the linear movement generated by the outer coupling unit along the third direction; the first direction, the second direction and the third direction are perpendicular to each other.

10. The accelerometer according to claim 9, wherein: The in-plane detection device includes a plurality of X-axis in-plane detection units for detecting the linear motion of the outer coupling unit along the second direction, and / or a plurality of Y-axis in-plane detection units for detecting the linear motion of the outer coupling unit along the third direction.

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