A micromechanical accelerometer

Abstract

The application provides a micromechanical accelerometer, which comprises at least four fixed anchors, the fixed anchors are integrally formed into a rectangle and are located at four vertices of the rectangle; an inertial mass module is located at a middle position of the rectangle and is connected with all the fixed anchors respectively; a plurality of elastic connection modules are connected between the inertial mass module and the fixed anchors respectively; and a plurality of detection capacitance modules are arranged on the inertial mass module and are used for detecting displacement of the inertial mass module; wherein two fixed anchors located at the same side are connected with a positive voltage, two fixed anchors located at the other side are connected with a negative voltage, or one group of fixed anchors located at diagonal positions are connected with the positive voltage, and the other group of fixed anchors located at diagonal positions are connected with the negative voltage, the positive voltage and the negative voltage have equal amplitudes; the fixed anchors, the elastic connection modules and the inertial mass module form a channel. The application has compact structure and can significantly improve sensitivity of the capacitive micromechanical accelerometer.

Description

Technical Field

[0001] This invention relates to the field of microelectromechanical systems (MEMS) technology, and in particular to a micromechanical accelerometer. Background Technology

[0002] Micromechanical accelerometers, as typical inertial devices in microelectromechanical systems (MEMS), have shown broad application prospects in aerospace, automotive, and consumer electronics industries due to their small size, light weight, low cost, high reliability, and suitability for mass production. High-resolution capacitive accelerometers are widely used in high-precision measurement fields such as inertial navigation and seismic detection.

[0003] The structural sensitivity of micromechanical accelerometers is directly affected by the stiffness coefficient of the elastic structure; the lower the stiffness, the higher the sensitivity. In existing technologies, micromechanical anti-spring accelerometers achieve a near-zero stiffness coefficient by using the gravity of an inertial mass to bias the elastic structure into a low-stiffness position. However, this design typically requires a large bias force and displacement, making it difficult to further miniaturize such accelerometers while achieving a near-zero stiffness coefficient. Therefore, improvements are needed. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a micromechanical accelerometer to solve the technical problem that the prior art micromechanical anti-spring accelerometer requires a large bias force and bias displacement, which makes it difficult to further miniaturize it while achieving quasi-zero stiffness.

[0005] To achieve the above and other related objectives, the present invention provides a micromechanical accelerometer, comprising:

[0006] At least four fixed anchor points, the fixed anchor points forming a rectangle and located at the four vertices of the rectangle;

[0007] An inertial mass module is located at the center of the rectangle and is connected to all of the fixed anchor points respectively;

[0008] Multiple flexible connection modules are respectively connected between the inertial mass module and the fixed anchor point; and

[0009] Multiple detection capacitor modules are disposed on the inertial mass module, and the detection capacitor modules are used to detect the displacement of the inertial mass module;

[0010] The displacement direction of the inertial mass module is set as a first direction, and the surface of the inertial mass module and perpendicular to the first direction is set as a second direction. A plurality of detection capacitor modules are disposed on the inertial mass module along the second direction.

[0011] Along the second direction, two of the fixed anchor points on the same side are connected to a positive voltage, and two of the fixed anchor points on the other side are connected to a negative voltage; or, one set of the fixed anchor points located diagonally are connected to a positive voltage, and another set of the fixed anchor points located diagonally are connected to a negative voltage, wherein the magnitudes of the positive voltage and the negative voltage are equal.

[0012] The fixed anchor point, the elastic connection module, and the inertial mass module form a pathway.

[0013] In one embodiment of the present invention, the elastic connection module includes:

[0014] A linear folding beam, one end of which is connected to the inertial mass module and the other end of which is connected to the fixed anchor point;

[0015] It includes two straight beams and one semi-circular beam, one of the straight beams being connected between one end of the semi-circular beam and the inertial mass module, and the other straight beam being connected between the other end of the semi-circular beam and the fixed anchor point;

[0016] A nonlinear bending beam, one end of which is connected to the inertial mass module, and the other end of which is connected to the fixed anchor point.

[0017] In one embodiment of the present invention, the linear folding beam includes two straight beams and a semi-circular beam, wherein one straight beam is connected between one end of the semi-circular beam and the inertial mass module, and the other straight beam is connected between the other end of the semi-circular beam and the fixed anchor point.

[0018] In one embodiment of the present invention, the width of the nonlinear bending beam is a fixed value, and the shape of its side side satisfies the shape of a cosine function curve.

[0019] In one embodiment of the present invention, the micromechanical accelerometer further includes a plurality of feedback capacitor modules, which are disposed on the inertial mass module along the first direction.

[0020] In one embodiment of the present invention, the micromechanical accelerometer further includes:

[0021] Multiple detection anchor points are arranged on both sides of the inertial mass module along the second direction; and

[0022] Multiple feedback anchor points are arranged on both sides of the inertial mass module along the first direction.

[0023] In one embodiment of the present invention, the capacitance detection module includes:

[0024] Movable detection comb teeth are connected to the inertial mass module; and

[0025] Fixed detection comb teeth are connected to the detection anchor point;

[0026] The movable detection comb teeth and the fixed detection comb teeth correspond to form a detection capacitor, and the change in capacitance of the detection capacitor corresponds to the displacement of the inertial mass module.

[0027] In one embodiment of the present invention, both the movable detection comb and the fixed detection comb include multiple comb cantilever arms, each comb cantilever arm is provided with a comb array, and the multiple comb cantilever arms of the movable detection comb and the multiple comb cantilever arms of the fixed detection comb correspondingly form multiple pairs of parallel plates.

[0028] In one embodiment of the present invention, a plurality of detection capacitor modules are symmetrically distributed about the center line of the inertial mass module parallel to the first direction, and also symmetrically distributed about the center line of the inertial mass module parallel to the second direction.

[0029] In one embodiment of the present invention, the equivalent stiffness coefficient of the elastic connection module after being heated by electricity is less than or equal to 0.1 N / m.

[0030] As described above, the micromechanical accelerometer of the present invention has the following beneficial effects: the present invention achieves a near-zero stiffness elastic structure under small size conditions, which can significantly improve the sensitivity of the capacitive micromechanical accelerometer. Attached Figure Description

[0031] Figure 1 The diagram shown is a structural schematic of a micromechanical accelerometer provided in an embodiment of the present invention.

[0032] Figure 2 The diagram shown is a structural schematic of an elastic connection module according to an embodiment of the present invention.

[0033] Figure 3 The diagram shown is a structural schematic of a detection capacitor module according to an embodiment of the present invention;

[0034] Figure 4 The diagram shown is a structural schematic of a feedback capacitor module in one embodiment of the present invention.

[0035] In the picture:

[0036] 100. Fixed anchor points;

[0037] 200. Inertial Mass Module;

[0038] 300. Flexible connection module; 310. Linear folding beam; 320. Nonlinear bending beam;

[0039] 400. Capacitor detection module; 410. Movable detection comb teeth; 420. Fixed detection comb teeth;

[0040] 500. Feedback capacitor module; 520. Movable feedback comb teeth; 520. Fixed feedback comb teeth;

[0041] 600. Detect anchor points;

[0042] 700, Feedback Anchor Point. Detailed Implementation

[0043] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0044] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0045] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.

[0046] First, it's important to clarify that a MEMS (Micro-Electro-Mechanical Systems) accelerometer is a miniature sensor used to measure acceleration. It utilizes a combination of microelectronics and micromechanical techniques to detect the linear acceleration of an object along one or more axes. Unlike traditional accelerometers, near-zero stiffness accelerometers typically have a two-part structural design. One part is a common supporting beam structure, exhibiting positive stiffness. The other part provides negative stiffness to cancel out the positive stiffness of the beam structure. Unlike large vibration isolation systems, many load-generating mechanisms such as springs and magnetic coils cannot be used in the MEMS field. Therefore, the method of generating negative stiffness is crucial. Currently, the mechanism for generating negative stiffness generally employs buckling beams or anti-spring beams. The static characteristics of these beam structures can be summarized as follows: as the magnitude of the load at the midpoint of the double-ended fixed beam gradually increases, the stiffness exhibited by the beam changes from positive stiffness to local negative stiffness and then back to positive stiffness. Because of the existence of localized negative stiffness characteristics that are approximately linear, the combined MEMS accelerometer can achieve near-zero stiffness locally. However, to achieve this zero stiffness, a certain amount of force needs to be pre-applied at the midpoint of the beam to induce a certain displacement. For beams made of silicon, their inherent brittleness makes it difficult to withstand large deformations.

[0047] This invention provides a micromechanical accelerometer, relating to the field of microelectromechanical systems (MEMS) technology. It addresses the technical problem in existing micromechanical anti-spring accelerometers that require large bias forces and displacements, hindering further miniaturization while achieving quasi-zero stiffness. This invention, through a specially designed elastic structure, achieves a quasi-zero stiffness coefficient within a small size. Specific embodiments are described in detail below.

[0048] Please see Figure 1 An embodiment of the present invention provides a micromechanical accelerometer, which may include: a fixed anchor point 100, an inertial mass module 200, an elastic connection module 300, a detection capacitor module 400, and a feedback capacitor module 500. The fixed anchor point 100 provides basic support for the entire accelerometer, ensuring that the other modules are correctly installed and fixed to the substrate. Multiple fixed anchor points 100 form a rectangle and are located at the four vertices of the rectangle. In this embodiment, four fixed anchor points 100 are located at the four vertices of the rectangle. The inertial mass module 200 is the core part of the accelerometer and can move freely. The inertial mass module 200 can be located in the middle of the rectangle. When the accelerometer is subjected to an external force, the inertial mass module 300 will move relative to the substrate, such as... Figure 1As shown, the inertial mass module 300 will move along the Y-axis. In this embodiment, the displacement direction of the inertial mass module 200 is set as the first direction, and the direction perpendicular to the first direction on the surface of the inertial mass module 200 is set as the second direction. The elastic connection module 300 can be connected between the inertial mass module 200 and the fixed anchor point 100, allowing the inertial mass module 200 to have a certain range of movement. In this embodiment, the inertial mass module 200 is connected to a fixed anchor point 100 at each of its four azimuth angles via an elastic connection module 300. The elastic connection module 300 can exhibit extremely low stiffness under preset conditions, thus indicating that even a very small acceleration received by the accelerometer can cause a significant displacement change in the inertial mass module 200. The detection capacitor module 400 can be used to sense the displacement of the inertial mass module 200. As the displacement of the inertial mass module 200 changes, the capacitance value of the detection capacitor module 400 will also change accordingly. This change can be converted into an electrical signal, thereby reflecting the magnitude of the acceleration. In this embodiment, multiple detection capacitor modules 400 can be used, respectively located on both sides of the inertial mass module 200 along its direction of movement (i.e., the Y direction). Feedback capacitor modules 500 can be used to construct a closed-loop acceleration sensing system. Feedback capacitor modules 500 can help adjust the position of the inertial mass module 200, thereby counteracting the effects of external acceleration and maintaining the system's balance. In this embodiment, multiple feedback capacitor modules 500 can be used, respectively located at both ends of the inertial mass module 200 along its direction of movement.

[0049] Please see Figure 1 In one embodiment of the present invention, the inertial mass module 200 is in the shape of an "I", that is, the inertial mass module 200 is symmetrical in both the X-axis and Y-axis directions. Figure 1 As shown, a recess is provided on both the upper and lower sides of the inertial mass module 200. Multiple detection capacitor modules 400 can be respectively disposed in the aforementioned recesses, and the positions and orientations of the multiple detection capacitor modules 400 are symmetrically distributed about the center line of the inertial mass module 200 parallel to the first direction (i.e., the Y-axis direction) and the center line parallel to the second direction (i.e., the X-axis direction). Multiple feedback capacitor modules 500 can be respectively disposed at both ends of the inertial mass module 200, and the positions and orientations of the multiple feedback capacitor modules 500 are also symmetrically distributed about the center line of the inertial mass module 200 parallel to the first direction and the center line parallel to the second direction.

[0050] Please see Figure 1 , Figure 2In one embodiment of the present invention, the elastic connection module 300 may include a linear folding beam 310 and a nonlinear bending beam 320. The linear folding beam 310 is a structure composed of two straight beams connected by a semi-circular beam. Both ends of the linear folding beam 310 are connected to a fixed anchor point 100 and an inertial mass module 200, respectively, providing high flexibility and low stiffness while ensuring structural stability and compactness. In this embodiment, the width of the linear folding beam 310 can be set between 2µm and 6µm, wherein the inner radius of the semi-circular beam can be set between 3µm and 6µm, and the lengths of the two straight beams are the same, set between 200µm and 205µm. Preferably, the width of the linear folding beam 310 is 4µm, wherein the inner radius of the semi-circular beam can be set to 5µm, and the length of the two straight beams is 204µm. The width of the nonlinear bending beam 320 can be set between 2µm and 6µm, and the geometry of its beam side can satisfy a cosine function curve shape. In this embodiment, the width of the nonlinear bending beam 320 is 4µm, and the geometry of its beam side satisfies the following formula.

[0051] Y=1μm·(1-cos(2π·x / 400μm)),x∈(0,400μm);

[0052] Where x represents a point on that side. Figure 1 The coordinates shown are on the X-axis, and the Y-axis represents the position of the point. Figure 1 The coordinates on the XY axis are shown.

[0053] Please see Figure 1In one embodiment of the present invention, two fixed anchor points 100 are connected to a positive voltage, and the remaining two fixed anchor points 100 are connected to a negative voltage, with the amplitudes of the positive and negative voltages being equal. Specifically, along the second direction, two fixed anchor points 100 located on the same side are connected to a +3.5V voltage, and two fixed anchor points 100 located on the other side are connected to a -3.5V voltage. Alternatively, one set of fixed anchor points 100 located diagonally are connected to a +3.5V voltage, and another set of fixed anchor points 100 located diagonally are connected to a -3.5V negative voltage. In this case, since the fixed anchor points 100, the elastic connection module 300, and the inertial mass module 200 can form a circuit, the longitudinal centerline of the inertial mass module 200 has a potential of 0, while there will be a potential difference on both sides of the entire inertial mass module 200. Therefore, current will flow through each elastic connection module 300. When current flows through a conductor, such as the elastic connection module 300, due to the internal resistance of the elastic connection module 300, electrical energy will be partially converted into heat energy. The multiple elastic connection modules 300 are symmetrically distributed along the centerline of the inertial mass module 200. Therefore, the inertial mass module 200 is in force balance and will not displace. As mentioned above, the linear folding beam 310 and the nonlinear bending beam 320 will undergo thermal expansion. The two straight beams of the linear folding beam 310 are parallel, and their fixed ends are located on the same side. Therefore, after heating, both expand in the same direction, and no additional force is generated on the linear folding beam 310. The fixed ends of the nonlinear bending beam 320 are located on opposite sides, with the distance remaining constant. After heating, the axial force increases due to thermal expansion. When the axial force exceeds the critical buckling load, the nonlinear bending beam 320 will buckle. At this time, the nonlinear bending beam 320 will generate a negative stiffness coefficient. Therefore, after heating, the equivalent stiffness coefficient formed by the superposition of the positive stiffness coefficient of the linear folding beam 310 and the negative stiffness coefficient of the nonlinear bending beam 320 can be approximated as zero. In this embodiment, based on the preferred parameter settings in the above embodiments, the equivalent stiffness coefficient of its elastic structure is approximately 0.1 N / m.

[0054] Please see Figure 1 In one embodiment of the present invention, the micromechanical accelerometer further includes a plurality of detection anchor points 600 and a plurality of feedback anchor points 700. The plurality of detection anchor points 600 are disposed on both sides of the inertial mass module 200 along a second direction. The plurality of feedback anchor points 700 are disposed on both sides of the inertial mass module 200 along a first direction.

[0055] Please see Figure 1 , Figure 3In one embodiment of the present invention, the detection capacitor module 400 may include two comb tooth structures: a movable detection comb tooth 410 and a fixed detection comb tooth 420. The movable detection comb tooth 410 can be connected to the inertial mass module 200, and its movement is consistent with that of the inertial mass module 200. The fixed detection comb tooth 420 can be connected to the detection anchor point 600 and remains stationary. Both the movable and fixed detection comb teeth 410 and 420 include multiple comb tooth cantilevers, each with a comb tooth array. Multiple pairs of parallel plates can be formed between the multiple pairs of comb tooth cantilevers on the movable and fixed detection comb teeth 410 and 420, thereby forming a detection capacitor. The capacitance change between the parallel plates directly reflects the displacement change of the inertial mass module 200. In this embodiment, the geometric dimensions of the comb tooth cantilevers and the comb tooth arrays on the movable and fixed detection comb teeth 410 and 420 are the same. The length of the comb cantilever can be set between 400µm and 600µm, the length of the comb teeth in the comb array can be set between 15µm and 20µm, the width of the comb teeth is between 2µm and 4µm, the spacing between two comb teeth is between 2µm and 4µm, and the initial overlap length of the comb teeth is between 8µm and 15µm. Preferably, the length of the comb cantilever is 500µm, the length of the comb teeth in the comb array can be set to 17µm, the width to 2µm, the spacing between two comb teeth to 3µm, and the initial overlap length of the comb teeth to 11µm.

[0056] Please see Figure 1 , Figure 4 In one embodiment of the present invention, a feedback capacitor module 500 may be disposed on an inertial mass module 200 along a first direction. The feedback capacitor module 500 may include movable feedback comb teeth 510 and fixed feedback comb teeth 520. Both the movable feedback comb teeth 510 and the fixed feedback comb teeth 520 are comb tooth arrays containing multiple parallel comb teeth. The movable feedback comb teeth 510 may be connected to the inertial mass module 200 and may move with the movement of the inertial mass module 200. The fixed detection comb teeth 520 may be fixedly connected to the feedback anchor point 700 and remain stationary. In this embodiment, the comb tooth array of the movable feedback comb teeth 510 and the comb tooth array of the fixed feedback comb teeth 520 may form a feedback capacitor. In this embodiment, the movable feedback comb teeth 510 and the fixed feedback comb teeth 520 have the same geometric dimensions, wherein the length and width of the comb teeth may be set to between 2µm and 5µm, and the initial overlap length of the comb teeth on both sides is between 8µm and 15µm. Preferably, the comb teeth are between 37µm in length and 3µm in width, and the initial overlap length of the comb teeth on both sides is 11µm.

[0057] In summary, the micromechanical accelerometer disclosed in this invention achieves a near-zero stiffness elastic structure under small size conditions, which can significantly improve the sensitivity of capacitive micromechanical accelerometers. Compared with existing micromechanical anti-spring accelerometer designs, the technical solution of this invention can achieve a low stiffness coefficient of approximately 0.1 N / m without relying on large bias forces and bias displacements. Furthermore, the novel accelerometer of this invention has an extremely small size, with a device size of only 10 mm. -4 m 2 It boasts a large scale and excellent miniaturization characteristics. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial application value.

[0058] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A micromechanical accelerometer, characterized in that, include: At least four fixed anchor points, the fixed anchor points forming a rectangle and located at the four vertices of the rectangle; An inertial mass module is located at the center of the rectangle and is connected to all of the fixed anchor points respectively; Multiple flexible connection modules are respectively connected between the inertial mass module and the fixed anchor point, and the flexible connection module includes: A linear folding beam, one end of which is connected to the inertial mass module and the other end of which is connected to the fixed anchor point; It includes two straight beams and one semi-circular beam, one of the straight beams being connected between one end of the semi-circular beam and the inertial mass module, and the other straight beam being connected between the other end of the semi-circular beam and the fixed anchor point; A nonlinear bending beam, one end of which is connected to the inertial mass module and the other end of which is connected to the fixed anchor point, has a fixed width and its side shape satisfies the shape of a cosine function curve; and Multiple detection capacitor modules are disposed on the inertial mass module, and the detection capacitor modules are used to detect the displacement of the inertial mass module; The displacement direction of the inertial mass module is set as a first direction, and the surface of the inertial mass module and perpendicular to the first direction is set as a second direction. A plurality of detection capacitor modules are disposed on the inertial mass module along the second direction. Along the second direction, two of the fixed anchor points on the same side are connected to a positive voltage, and two of the fixed anchor points on the other side are connected to a negative voltage; or, one set of the fixed anchor points located diagonally are connected to a positive voltage, and another set of the fixed anchor points located diagonally are connected to a negative voltage, wherein the magnitudes of the positive voltage and the negative voltage are equal. The fixed anchor point, the elastic connection module, and the inertial mass module form a passage. After being heated by electricity, the linear folding beam generates a positive stiffness coefficient, the nonlinear bending beam generates a negative stiffness coefficient, and the equivalent stiffness coefficient formed by the superposition of the positive stiffness coefficient and the negative stiffness coefficient is zero. The micromechanical accelerometer also includes multiple feedback capacitor modules, which are disposed on the inertial mass module along the first direction; Multiple detection anchor points are arranged on both sides of the inertial mass module along the second direction; and Multiple feedback anchor points are arranged on both sides of the inertial mass module along the first direction.

2. The micromechanical accelerometer according to claim 1, characterized in that, The capacitance detection module includes: Movable detection comb teeth are connected to the inertial mass module; and Fixed detection comb teeth are connected to the detection anchor point; The movable detection comb teeth and the fixed detection comb teeth correspond to form a detection capacitor, and the change in capacitance of the detection capacitor corresponds to the displacement of the inertial mass module.

3. The micromechanical accelerometer according to claim 2, characterized in that, Both the movable detection comb and the fixed detection comb include multiple comb cantilever arms, and each comb cantilever arm is provided with a comb array. The multiple comb cantilever arms of the movable detection comb and the multiple comb cantilever arms of the fixed detection comb correspondingly form multiple pairs of parallel plates.

4. The micromechanical accelerometer according to claim 1, characterized in that, Multiple detection capacitor modules are symmetrically distributed about the center line of the inertial mass module parallel to the first direction, and also symmetrically distributed about the center line of the inertial mass module parallel to the second direction.

5. The micromechanical accelerometer according to claim 1, characterized in that, After being heated by electricity, the equivalent stiffness coefficient of the elastic connection module is less than or equal to 0.1 N / m.

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