Micromechanical accelerometer

Abstract

The invention provides a micro-mechanical accelerometer comprising at least four fixed anchor points which integrally form a rectangle and are located at four vertexes of the rectangle; the inertial mass module is located in the middle of the rectangle and connected with all the fixed anchor points; the plurality of elastic connecting modules are respectively connected between the inertial mass module and the fixed anchor point; the plurality of detection capacitance modules are arranged on the inertial mass module and are used for detecting the displacement of the inertial mass module; wherein the two fixed anchor points located on the same side are connected to positive voltage, the two fixed anchor points located on the other side are connected to negative voltage, or one set of fixed anchor points located at the diagonal position are connected to the positive voltage, the other set of fixed anchor points located at the diagonal position are connected to the negative voltage, and the amplitude of the positive voltage is equal to that of the negative voltage; and the fixed anchor point, the elastic connecting module and the inertial mass module form a passage. The capacitive micro-mechanical accelerometer is compact in structure, and the sensitivity of the capacitive micro-mechanical accelerometer can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-electromechanical systems, and in particular to a micro-mechanical accelerometer. Background Art

[0002] As a typical inertial device in micro-electromechanical systems (MEMS), micro-machined accelerometers have shown broad application prospects in aerospace, automotive industry, consumer electronics and other fields 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 earthquake detection.

[0003] The structural sensitivity of a micromechanical accelerometer is directly affected by the stiffness coefficient of the elastic structure. The lower the stiffness, the higher the sensitivity. In the prior art, a micromechanical anti-spring accelerometer uses the gravity of an inertial mass block to bias the elastic structure to a low stiffness position, thereby achieving a quasi-zero stiffness coefficient. However, this design usually requires a large bias force and bias displacement, which makes it difficult to further miniaturize such accelerometers while achieving a quasi-zero stiffness coefficient. Therefore, there is room for improvement. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a micromechanical accelerometer for solving the technical problem that the micromechanical back-spring accelerometer in the prior art 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 objectives and other related objectives, the present invention provides a micromechanical accelerometer, comprising:

[0006] At least four fixed anchor points, the fixed anchor points form a rectangle as a whole and are located at four vertices of the rectangle;

[0007] An inertial mass module, located in the middle of the rectangle and connected to all the fixed anchor points respectively;

[0008] a plurality of elastic connection modules, respectively connected between the inertial mass module and the fixed anchor point; and

[0009] A plurality of detection capacitor modules are arranged 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, a second direction is set on the surface of the inertial mass module and perpendicular to the first direction, and a plurality of the detection capacitor modules are arranged on the inertial mass module along the second direction;

[0011] Along the second direction, two of the fixed anchor points located on the same side are connected to a positive voltage, and two of the fixed anchor points located on the other side are connected to a negative voltage, or one group of the fixed anchor points located at a diagonal position is connected to a positive voltage, and another group of the fixed anchor points located at a diagonal position is connected to a negative voltage, and the amplitudes 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 passage.

[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 comprises two straight beams and one semicircular beam, wherein one straight beam is connected between one end of the semicircular beam and the inertial mass module, and the other straight beam is connected between the other end of the semicircular beam and the fixed anchor point;

[0016] A nonlinear curved beam has one end connected to the inertial mass module and the other end connected to the fixed anchor point.

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

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

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

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

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

[0022] A plurality of 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 connected to the inertial mass module; and

[0025] Fixed detection comb teeth 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 a capacitance change value of the detection capacitor is in a corresponding relationship with the displacement of the inertial mass module.

[0027] In one embodiment of the present invention, the movable detection comb teeth and the fixed detection comb teeth both include a plurality of comb tooth cantilevers, each comb tooth cantilever is provided with a comb tooth array, and the plurality of comb tooth cantilevers of the movable detection comb teeth and the plurality of comb tooth cantilevers of the fixed detection comb teeth correspond to form a plurality of pairs of parallel pole plates.

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

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

[0030] As described above, a micromechanical accelerometer of the present invention has the following beneficial effects: the present invention realizes a near-zero stiffness elastic structure under small-size conditions, and can significantly improve the sensitivity of the capacitive micromechanical accelerometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Shown is a schematic structural diagram of a micromechanical accelerometer provided by an embodiment of the present invention;

[0032] Figure 2 Shown is a schematic structural diagram of an elastic connection module in one embodiment of the present invention;

[0033] Figure 3 Shown is a schematic diagram of the structure of a detection capacitor module in one embodiment of the present invention;

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

[0035] In the figure:

[0036] 100. Fixed anchor point;

[0037] 200, inertial mass module;

[0038] 300, elastic connection module; 310, linear folding beam; 320, nonlinear bending beam;

[0039] 400, detection capacitor 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 DESCRIPTION

[0043] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0044] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0045] In the following description, numerous details are discussed to provide a more thorough explanation of the embodiments of the present invention. However, it is obvious to those skilled in the art that the embodiments of the present invention can be implemented without these specific details. In other embodiments, well-known structures and devices are shown in the form of block diagrams rather than in detail to avoid making the embodiments of the present invention difficult to understand.

[0046] First of all, it should be noted that a MEMS (Micro-Electro-Mechanical Systems) accelerometer is a miniature sensor for measuring acceleration, which uses a combination of microelectronics and micromechanical technologies to detect the linear acceleration of an object along one or more axes. Unlike traditional accelerometers, the structural design of a near-zero stiffness accelerometer is usually divided into two parts, one of which is a common beam structure that provides support, which exhibits positive stiffness. In addition, there is a part of the structure that provides negative stiffness, which offsets the positive stiffness of the beam structure. Unlike large-scale vibration isolation systems, in the MEMS field, many load generation mechanisms such as springs and magnetic coils cannot be used. Therefore, the way to generate negative stiffness is the key. At present, the mechanism for generating negative stiffness generally uses a buckling beam or an anti-spring beam. The static characteristics of this type of beam structure can be briefly described as follows: as the size of the midpoint load of the double-end clamped beam gradually increases, the stiffness exhibited by the beam is transformed from positive stiffness to local negative stiffness and then to positive stiffness. Because of the local negative stiffness characteristics and the approximate linearity, the combined MEMS accelerometer can obtain local near-zero stiffness. However, to achieve this zero stiffness, a certain amount of force must be pre-applied at the midpoint of the beam to cause the beam to have a certain displacement. For a beam made of silicon, it is difficult to withstand large deformation due to its own brittleness.

[0047] The present invention provides a micromechanical accelerometer, which relates to the technical field of micro-electromechanical systems and can be used to solve the technical problem that the micromechanical anti-spring accelerometer in the prior art requires a large bias force and bias displacement, which makes it difficult to further miniaturize the accelerometer while achieving quasi-zero stiffness. The present invention can achieve a quasi-zero stiffness coefficient in a small size through a specially designed elastic structure. The following is a detailed description through specific embodiments.

[0048] See also 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. Among them, the fixed anchor point 100 is used to provide basic support for the entire accelerometer, which can ensure that other modules are correctly installed and fixed on the substrate. The multiple fixed anchor points 100 form a rectangle as a whole, and are respectively located at the four vertices of the rectangle. In this embodiment, the four fixed anchor points 100 are respectively located at the four vertices of the rectangle. The inertial mass module 200 is the core part of the accelerometer, which can move freely. The inertial mass module 200 can be located in the middle position of the above-mentioned rectangle. When the accelerometer is subjected to 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 direction. In this embodiment, the displacement direction of the inertial mass module 200 is set as a first direction, and the second direction is set on the surface of the inertial mass module 200 and perpendicular to the first direction. The elastic connection module 300 can be connected between the inertial mass module 200 and the fixed anchor point 100, and allows 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 its four azimuth angles through an elastic connection module 300. The elastic connection module 300 can show extremely low stiffness under preset conditions. It can be seen that when the accelerometer receives a very small acceleration, it can also cause a significant displacement change of 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, and this change can be converted into an electrical signal, thereby reflecting the magnitude of the acceleration. In this embodiment, the number of detection capacitor modules 400 can be multiple, and they are respectively arranged at both sides of the inertial mass module 200 along its moving direction (i.e., the Y direction). The feedback capacitor module 500 can be used to form a closed-loop acceleration sensing system. The feedback capacitor module 500 can help adjust the position of the inertial mass module 200, thereby offsetting the influence of external acceleration and maintaining the balance state of the system. In this embodiment, the number of feedback capacitor modules 500 can be multiple, and they can be respectively arranged at both ends of the inertial mass module 200 along its moving direction.

[0049] See also 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 direction and the Y-axis direction. Figure 1 As shown, a depression is provided on both the upper and lower sides of the inertial mass module 200. A plurality of detection capacitor modules 400 can be respectively disposed in the above-mentioned depressions, and the positions and directions of the plurality of detection capacitor modules 400 can be 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). A plurality of feedback capacitor modules 500 can be respectively disposed at both ends of the inertial mass module 200, and the positions and directions of the plurality of 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] See also 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 semicircular beam. The two ends of the linear folding beam 310 are respectively connected to the fixed anchor point 100 and the inertial mass module 200, which can provide higher flexibility and lower stiffness while ensuring the stability and compactness of the structure. In this embodiment, the width of the linear folding beam 310 can be set to between 2um and 6um, wherein the inner radius of the semicircular beam can be set to between 3um and 6um, and the lengths of the two straight beams are the same and can be set to between 200um and 205um. Preferably, the width of the linear folding beam 310 is 4um, wherein the inner radius of the semicircular beam can be set to 5um, and the length of the two straight beams is 204um. The width of the nonlinear bending beam 320 can be set to between 2um and 6um, and the geometric shape of the side of the beam can meet the shape of the cosine function curve. In this embodiment, the width of the nonlinear curved beam 320 is 4 um, and the geometric shape of the beam side satisfies the following formula.

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

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

[0053] See also Figure 1In one embodiment of the present invention, two of the fixed anchor points 100 are connected to a positive voltage, and the remaining two fixed anchor points 100 are connected to a negative voltage, and the amplitudes of the positive voltage and the negative voltage are equal. Specifically, along the second direction, the two fixed anchor points 100 located on the same side are connected to a +3.5V voltage, and the two fixed anchor points 100 located on the other side are connected to a -3.5V voltage. Alternatively, one group of fixed anchor points 100 located at a diagonal position is connected to a +3.5V voltage, and another group of fixed anchor points 100 located at a diagonal position is connected to a negative voltage of -3.5V. At this time, since the fixed anchor points 100, the elastic connection module 300 and the inertial mass module 200 can form a passage, the longitudinal center line of the inertial mass module 200 is 0 potential, and there will be a potential difference on both sides of the entire inertial mass module 200, so each elastic connection module 300 will have a current passing through it. When current passes through a conductor, such as an elastic connection module 300, due to the resistance inside the elastic connection module 300, the electrical energy will be partially converted into heat energy. The multiple elastic connection modules 300 are symmetrically distributed along the center line of the inertial mass module 200. Therefore, the inertial mass module 200 is balanced in force and will not be displaced. As can be seen from the above, the linear folding beam 310 and the nonlinear curved beam 320 will experience thermal expansion. Among them, the two straight beams of the linear folding beam 310 are arranged in parallel, and the fixed ends are located on the same side. Therefore, after heating, the expansion directions of the two are the same, and no additional force will be generated on the linear folding beam 310. The fixed ends of the nonlinear curved beam 320 are located on opposite sides, and the distance remains unchanged. After heating, the axial force increases due to thermal expansion. When the axial force exceeds the critical buckling load, the nonlinear curved beam 320 will be in a buckling state. At this time, the nonlinear curved beam 320 will generate a negative stiffness coefficient. It can be seen that after heating, the equivalent stiffness coefficient formed by superimposing the positive stiffness coefficient of the linear folding beam 310 and the negative stiffness coefficient of the nonlinear curved beam 320 can be approximately zero. In this embodiment, according to the preferred parameter settings in the above embodiments, the equivalent stiffness coefficient of the elastic structure is approximately 0.1 N / m.

[0054] See also Figure 1 In one embodiment of the present invention, the micromechanical accelerometer of the present invention 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 arranged on both sides of the inertial mass module 200 along the second direction. The plurality of feedback anchor points 700 are arranged on both sides of the inertial mass module 200 along the first direction.

[0055] See also Figure 1 , Figure 3In one embodiment of the present invention, the detection capacitor module 400 may include two parts of the comb structure, namely, a movable detection comb 410 and a fixed detection comb 420. Among them, the movable detection comb 410 can be connected to the inertial mass module 200, and its movement mode is consistent with that of the inertial mass module 200. The fixed detection comb 420 can be connected to the detection anchor point 600 and always remain motionless. The movable detection comb 410 and the fixed detection comb 420 both include a plurality of comb cantilevers, and each comb cantilever is provided with a comb array. Multiple pairs of parallel plates can be formed between the multiple pairs of comb cantilevers on the movable detection comb 410 and the fixed detection comb 420, thereby forming a detection capacitor, and the capacitance change between the parallel plates can directly reflect the displacement change of the inertial mass module 200. In this embodiment, the geometric dimensions of the comb cantilevers and the comb arrays on the movable detection comb 410 and the fixed detection comb 420 are the same. The length of the comb tooth cantilever can be set to between 400um and 600um, the length of the comb teeth in the comb tooth array can be set to between 15um and 20um, the width of the comb teeth is between 2um and 4um, the spacing between two comb teeth is between 2um and 4um, and the initial overlapping length of the comb teeth is between 8um and 15um. Preferably, the length of the comb tooth cantilever is 500um, the length of the comb teeth in the comb tooth array can be set to 17um, the width is 2um, the spacing between two comb teeth is 3um, and the initial overlapping length of the comb teeth is 11um.

[0056] See also Figure 1 , Figure 4 In one embodiment of the present invention, the feedback capacitor module 500 may be arranged on the inertial mass module 200 along the first direction. The feedback capacitor module 500 may include a movable feedback comb tooth 510 and a fixed feedback comb tooth 520. The movable feedback comb tooth 510 and the fixed feedback comb tooth 520 are both comb tooth arrays including a plurality of parallel comb teeth. The movable feedback comb tooth 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 tooth 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 tooth 510 and the comb tooth array of the fixed feedback comb tooth 520 may form a feedback capacitor. In this embodiment, the geometric dimensions of the movable feedback comb tooth 510 and the fixed feedback comb tooth 520 are the same, wherein the length of the comb tooth and the width of the comb tooth may be set between 2um and 5um, and the initial overlap length of the comb teeth on both sides is between 8um and 15um. Preferably, the length of the comb teeth is between 37 um, the width is 3 um, and the initial overlapping length of the comb teeth on both sides is 11 um.

[0057] In summary, the micromechanical accelerometer disclosed in the present invention realizes a near-zero stiffness elastic structure under small size conditions, which can significantly improve the sensitivity of the capacitive micromechanical accelerometer. Compared with the existing micromechanical anti-spring accelerometer design, the technical solution of the present invention can achieve a low stiffness coefficient of about 0.1N / m without relying on large bias force and bias displacement. In addition, the size of the new accelerometer of the present invention is extremely small, and its device size is only 10 -4 m 2 Therefore, the present invention effectively overcomes various shortcomings of the prior art and has high industrial utilization value.

[0058] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may 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 a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall 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 form a rectangle as a whole and are located at four vertices of the rectangle; An inertial mass module, located in the middle of the rectangle and connected to all the fixed anchor points respectively; a plurality of elastic connection modules, respectively connected between the inertial mass module and the fixed anchor point; and A plurality of detection capacitor modules are arranged 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, a second direction is set on the surface of the inertial mass module and perpendicular to the first direction, and a plurality of the detection capacitor modules are arranged on the inertial mass module along the second direction; Along the second direction, two of the fixed anchor points located on the same side are connected to a positive voltage, and two of the fixed anchor points located on the other side are connected to a negative voltage, or one group of the fixed anchor points located at a diagonal position is connected to a positive voltage, and another group of the fixed anchor points located at a diagonal position is connected to a negative voltage, and the amplitudes 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.

2. The micromechanical accelerometer according to claim 1, characterized in that: The elastic connection module comprises: 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 comprises two straight beams and one semicircular beam, wherein one straight beam is connected between one end of the semicircular beam and the inertial mass module, and the other straight beam is connected between the other end of the semicircular beam and the fixed anchor point; A nonlinear curved beam has one end connected to the inertial mass module and the other end connected to the fixed anchor point.

3. The micromechanical accelerometer according to claim 2, characterized in that: The linear folding beam includes two straight beams and a semicircular beam, wherein one straight beam is connected between one end of the semicircular beam and the inertial mass module, and the other straight beam is connected between the other end of the semicircular beam and the fixed anchor point.

4. The micromechanical accelerometer according to claim 2, characterized in that: The width of the nonlinear curved beam is a fixed value, and the shape of its side meets the shape of a cosine function curve.

5. The micromechanical accelerometer according to claim 1, characterized in that: The micromechanical accelerometer further includes a plurality of feedback capacitor modules, and the plurality of feedback capacitor modules are arranged on the inertial mass module along the first direction.

6. The micromechanical accelerometer according to claim 5, characterized in that: The micromechanical accelerometer further comprises: a plurality of detection anchor points, arranged on both sides of the inertial mass module along the second direction; and A plurality of feedback anchor points are arranged on both sides of the inertial mass module along the first direction.

7. The micromechanical accelerometer according to claim 6, characterized in that: The detection capacitance module comprises: Movable detection comb teeth connected to the inertial mass module; and Fixed detection comb teeth connected to the detection anchor point; The movable detection comb teeth and the fixed detection comb teeth correspond to form a detection capacitor, and a capacitance change value of the detection capacitor is in a corresponding relationship with the displacement of the inertial mass module.

8. The micromechanical accelerometer according to claim 7, characterized in that: The movable detection comb teeth and the fixed detection comb teeth both include a plurality of comb tooth cantilevers, each comb tooth cantilever is provided with a comb tooth array, and the plurality of comb tooth cantilevers of the movable detection comb teeth and the plurality of comb tooth cantilevers of the fixed detection comb teeth correspond to form a plurality of pairs of parallel pole plates.

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

10. The micromechanical accelerometer according to claim 1, characterized in that: After the elastic connection module is powered on and heated, its equivalent stiffness coefficient is less than or equal to 0.1 N / m.

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