A comb-tooth capacitive accelerometer

Abstract

The present invention discloses a comb-tooth capacitive accelerometer, which relates to the technical field of micromechanical accelerometers, and includes a substrate and an accelerometer structure, wherein the accelerometer structure is arranged on the substrate; the accelerometer structure includes a fixed support frame, a sensitive mass block frame, and a non-movable electrode assembly, wherein the non-movable electrode assembly is fixed on the substrate through an electrode anchor point, and a movable electrode assembly is arranged on the sensitive mass block frame, wherein the movable electrode assembly corresponds to the non-movable electrode assembly one by one, and the corresponding movable electrode assembly and the non-movable electrode assembly constitute a comb-tooth capacitor structure; the fixed support frame is fixed on the substrate through a fixed support frame anchor point, and the fixed support frame is connected to the sensitive mass block frame through an elastic structure, and the elastic structure enables the sensitive mass block frame to move along the sensitive axis direction. The present invention can effectively reduce the thermal stress inside the accelerometer structure, thereby ensuring that the performance of the accelerometer is stable when the ambient temperature changes.

Description

Technical Field

[0001] The invention relates to the technical field of micromechanical accelerometers, in particular to a comb-teeth capacitive accelerometer. Background Art

[0002] Micro-Electro-Mechanical System (MEMS) accelerometers have the advantages of small size, light weight, low cost, and high reliability, and have been widely used in the fields of automobiles, consumer electronics, and military industry. With the development of smart driving car technology, the demand for high-precision micro-mechanical accelerometers is also growing.

[0003] There are three main structural schemes for micro-electro-mechanical system (MEMS) accelerometers: sandwich pendulum accelerometer, comb-tooth capacitive accelerometer and torsion pendulum accelerometer. Comb-tooth capacitive accelerometer has become one of the most developed and widely used MEMS devices due to its high sensitivity, good stability and low temperature coefficient. The detection principle of comb-tooth capacitive accelerometer is: when there is an acceleration signal in the direction of the sensitive axis, the inertial sensitive mass block drives the movable comb-tooth electrode to displace, causing the plate spacing or overlapping area of ​​the comb-tooth capacitor to change, thereby generating a capacitance change, and then using a special measurement circuit to convert the capacitance change into an electrical signal to detect the input line acceleration information.

[0004] At present, China mainly adopts bulk silicon MEMS processing technology, wet SOG (silicon on glass), dry SOG, front bulk silicon and bulk silicon SOI (silicon on insulator) and other bulk silicon MEMS processes to process various MEMS chips. When processing comb-tooth capacitive accelerometers, due to the different thermal expansion coefficients between different materials, when the external ambient temperature changes, different materials will generate thermal stress, which will cause the accelerometer structure to deform; specifically, the movable structure of the comb-tooth capacitive accelerometer and the non-movable electrode of the comb-tooth capacitor are usually connected to the substrate through the electrode anchor structure. Since the electrode anchor is the only connection between the accelerometer structure and the substrate, the external thermal stress will be transmitted from the electrode anchor to the accelerometer structure, causing the accelerometer structure to deform and the detection capacitance to change, thereby affecting the stability of the accelerometer. If the accelerometer structure between different electrode anchors is constrained and cannot expand and contract freely, when the ambient temperature changes, thermal strain will also be generated inside the structure, affecting the stability of the device.

[0005] Therefore, how to reduce the impact of ambient temperature changes on accelerometer performance through reasonable accelerometer structure design and electrode anchor point layout is a problem that high-performance micromechanical accelerometers need to solve. Summary of the invention

[0006] The object of the present invention is to provide a comb-tooth capacitive accelerometer to solve the problems existing in the above-mentioned prior art, and to effectively reduce the thermal stress inside the accelerometer structure, thereby ensuring the stable performance of the accelerometer when the ambient temperature changes.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] The present invention provides a comb-tooth capacitive accelerometer, comprising a substrate and an accelerometer structure, wherein the accelerometer structure is arranged on the substrate; the accelerometer structure comprises a fixed support frame, a sensitive mass block frame and a non-movable electrode assembly, wherein the non-movable electrode assembly is fixed on the substrate through an electrode anchor point, and a movable electrode assembly is arranged on the sensitive mass block frame, wherein the movable electrode assembly corresponds to the non-movable electrode assembly one by one, and the corresponding movable electrode assembly and the non-movable electrode assembly constitute a comb-tooth capacitor structure; the fixed support frame is fixed on the substrate through a fixed support frame anchor point, and the fixed support frame is connected to the sensitive mass block frame through an elastic structure, and the elastic structure enables the sensitive mass block frame to move along the sensitive axis direction.

[0009] Preferably, the anchor point of the clamping frame is located at the center of the accelerometer structure.

[0010] Preferably, the fixing frame has only one anchor point.

[0011] Preferably, the fixed support frame is a cross-shaped frame, and the cross-shaped frame includes a longitudinal frame and a transverse frame that are perpendicular to each other, the center line of the transverse frame is collinear with the X-axis, the center line of the longitudinal frame is collinear with the Y-axis, the two ends of the longitudinal frame are symmetrical about the X-axis, the two ends of the transverse frame are symmetrical about the Y-axis, and the center of the anchor point of the fixed support frame is located at the intersection of the X-axis and the Y-axis; wherein the X-axis is parallel to the sensitive axis.

[0012] Preferably, both ends of the transverse frame are provided with connecting parts, and the connecting parts are connected to the sensitive mass block frame through the elastic structure, and both ends of the longitudinal frame are connected to the sensitive mass block frame through the elastic structure.

[0013] Preferably, the elastic structure is a single-degree-of-freedom elastic beam.

[0014] Preferably, one side of the outer edge of the sensitive mass block frame close to the connecting part is provided with anti-suction protrusions; the outer edge is located on the side of the connecting part away from the longitudinal frame, and the outer edge is perpendicular to the X-axis and parallel to the side of the sensitive mass block frame where the anti-suction protrusions are arranged.

[0015] Preferably, there are four non-movable electrode assemblies, including a first non-movable electrode assembly, a second non-movable electrode assembly, a third non-movable electrode assembly and a fourth non-movable electrode assembly, the first non-movable electrode assembly and the second non-movable electrode assembly are symmetrical about the Y-axis, the first non-movable electrode assembly and the third non-movable electrode assembly are symmetrical about the X-axis, and the second non-movable electrode assembly and the fourth non-movable electrode assembly are symmetrical about the X-axis.

[0016] Preferably, the electrode anchor point is arranged close to the Y-axis.

[0017] Preferably, the electrode anchor point and the fixing frame anchor point are both rectangular anchor points, and the long sides of the rectangular anchor points are perpendicular to the sensitive axis.

[0018] Compared with the prior art, the present invention has achieved the following beneficial technical effects:

[0019] In this embodiment, the accelerometer structure includes a fixed support frame, which is fixed on the substrate through a fixed support frame anchor point, and the fixed support frame is connected to the sensitive mass block frame through an elastic structure. The elastic structure enables the sensitive mass block frame to move along the sensitive axis to form a cantilever beam structure that can be freely extended and retracted. When the ambient temperature changes, compared with the structure with dispersed anchor points, the thermal stress inside the accelerometer structure can be effectively reduced, thereby ensuring that the performance of the accelerometer is stable when the ambient temperature changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 Schematic diagram of the structure of a comb-tooth capacitive accelerometer in an embodiment of the present invention;

[0022] Figure 2 Schematic diagram of the structure of a single-degree-of-freedom elastic beam in an embodiment of the present invention;

[0023] Figure 3 Schematic diagram of the structure of the anti-suction protrusion in the embodiment of the present invention;

[0024] Among them, 1 is the substrate, 2 is the fixed support frame, 3 is the sensitive mass block frame, 4 is the fixed support frame anchor point, 5 is the single-degree-of-freedom elastic beam, 6 is the single-degree-of-freedom elastic beam, 7 is the non-movable electrode, 8 is the non-movable electrode, 9 is the non-movable electrode, 10 is the non-movable electrode, 11 is the non-movable electrode, 12 is the non-movable electrode, 13 is the non-movable electrode, 14 is the non-movable electrode, 15 is the electrode anchor point, 16 is the electrode anchor point, 17 is the electrode Pole anchor point, 18 is the electrode anchor point, 19 is the electrode anchor point, 20 is the electrode anchor point, 21 is the electrode anchor point, 22 is the electrode anchor point, 23 is the movable electrode, 24 is the anti-attractive convex point, 25 is the anti-attractive convex point, 26 is the anti-attractive convex point, 27 is the anti-attractive convex point, 28 is the movable electrode, 29 is the movable electrode, 30 is the movable electrode, 31 is the movable electrode, 32 is the movable electrode, 33 is the movable electrode, and 34 is the movable electrode. DETAILED DESCRIPTION

[0025] 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.

[0026] The object of the present invention is to provide a comb-tooth capacitive accelerometer to solve the problems existing in the above-mentioned prior art, and to effectively reduce the thermal stress inside the accelerometer structure, thereby ensuring the stable performance of the accelerometer when the ambient temperature changes.

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Embodiment 1

[0029] like Figure 1-Figure 3As shown, this embodiment provides a comb-tooth capacitive accelerometer, including a substrate 1 and an accelerometer structure, wherein the accelerometer structure is arranged on the substrate 1; the accelerometer structure includes a fixed support frame 2, a sensitive mass block frame 3 and a non-movable electrode assembly, wherein the non-movable electrode assembly is fixed to the substrate 1 through an electrode anchor point, and a movable electrode assembly is arranged on the sensitive mass block frame 3, wherein the movable electrode assembly corresponds to the non-movable electrode assembly one by one, and the corresponding movable electrode assembly and the non-movable electrode assembly constitute a comb-tooth capacitor structure, wherein a plurality of non-movable comb-tooth electrodes are arranged on the non-movable electrode assembly, and a plurality of Gaps are left between the non-movable comb-tooth electrodes to form a comb-tooth structure. The movable electrode assembly correspondingly includes a plurality of movable comb-tooth electrodes. The plurality of movable comb-tooth electrodes are inserted into the gaps between the non-movable comb-tooth electrodes to form a variable-gap comb-tooth capacitor structure. Alternatively, a variable-area comb-tooth capacitor structure can be selected according to work needs. The fixed support frame 2 is fixed to the substrate 1 through the fixed support frame anchor point 4, and the fixed support frame 2 is connected to the sensitive mass block frame 3 through an elastic structure. The fixed support frame anchor point 4 is the anchor point of the sensitive mass block frame 3. The elastic structure enables the sensitive mass block frame 3 to move along the sensitive axis direction.

[0030] In this embodiment, the detection electrode units are formed by the comb-teeth capacitor structure, and one or more groups of detection electrode units can be provided according to work requirements.

[0031] In this embodiment, the fixed support frame 2 is fixed on the substrate 1 through the fixed support frame anchor point 4, and the fixed support frame 2 is connected to the sensitive mass block frame 3 through an elastic structure. The elastic structure enables the sensitive mass block frame 3 to move along the sensitive axis direction to form a cantilever beam structure that can be freely extended and retracted. When the ambient temperature changes, compared with the structure with dispersed anchor points, the thermal stress inside the accelerometer structure can be effectively reduced, thereby ensuring the stable performance of the accelerometer when the ambient temperature changes.

[0032] In this embodiment, the fixed support frame anchor point 4 is located at the center of the accelerometer structure, which can reduce the thermal stress caused by the change of ambient temperature and the accelerometer performance drift caused by the thermal stress; specifically, the fixed support frame anchor point 4 is located at the center of the accelerometer structure, which will reduce the distance from the anchor point of the sensitive mass block frame 3 to the center line of the structure, and the zero-position temperature drift will decrease linearly as the distance from the anchor point of the sensitive mass block frame 3 to the center line of the structure decreases. Therefore, the anchor point of the sensitive mass block frame 3 is placed in an area relatively close to the center line of the structure, and the zero-position temperature drift can be greatly reduced. In this embodiment, the fixed support frame anchor point 4 adopts a single anchor point, that is, the fixed support frame anchor point 4 has and is only provided with one.

[0033] In this embodiment, the fixed support frame 2 is a cross-shaped frame, mainly including a longitudinal frame and a transverse frame that are perpendicular to each other, the center line of the transverse frame is collinear with the X-axis, the center line of the longitudinal frame is collinear with the Y-axis, the two ends of the longitudinal frame are symmetrical about the X-axis, the two ends of the transverse frame are symmetrical about the Y-axis, and the center of the fixed support frame anchor point 4 is located at the intersection of the X-axis and the Y-axis; wherein the X-axis is parallel to the sensitive axis, and the sensitive axis is parallel to the movement direction of the movable electrode assembly.

[0034] In this embodiment, connecting parts are provided at both ends of the transverse frame, and the connecting parts are connected to the sensitive mass block frame 3 through an elastic structure. Both ends of the longitudinal frame are also connected to the sensitive mass block frame 3 through an elastic structure; wherein the connecting parts are perpendicular to the transverse frame, and connecting parts are provided on both sides of the end of the transverse frame, and the connecting parts on both sides are symmetrically arranged.

[0035] In this embodiment, the elastic structure is a single-degree-of-freedom elastic beam, and the single-degree-of-freedom elastic beam is preferably a folding elastic beam structure, such as Figure 2 shown.

[0036] In this embodiment, if Figure 3 As shown, one side of the outer edge of the sensitive mass block frame 3 close to the connecting portion is provided with anti-attraction convex points; the outer edge is located on the side of the connecting portion away from the longitudinal frame, and the outer edge is perpendicular to the X-axis and parallel to the side of the sensitive mass block frame 3 where the anti-attraction convex points are arranged; in this embodiment, the anti-attraction convex points are provided to prevent the movable comb-tooth electrode on the sensitive mass block frame 3 from being attracted to the non-movable comb-tooth electrode after a large impact on the sensitive mass block frame 3.

[0037] In this embodiment, there are four non-movable electrode assemblies, including a first non-movable electrode assembly, a second non-movable electrode assembly, a third non-movable electrode assembly, and a fourth non-movable electrode assembly. The first non-movable electrode assembly and the second non-movable electrode assembly are symmetrical about the Y axis, the first non-movable electrode assembly and the third non-movable electrode assembly are symmetrical about the X axis, and the second non-movable electrode assembly and the fourth non-movable electrode assembly are symmetrical about the X axis. Further, there are four corresponding movable electrode assemblies, including a first movable electrode assembly, a second movable electrode assembly, a third movable electrode assembly, and a fourth movable electrode assembly.

[0038] In this embodiment, the above-mentioned axisymmetric structure is adopted, and the influence trend of the processing error on the working mode of the accelerometer is consistent, which can reduce the influence of the processing error on the overall performance of the accelerometer.

[0039] In this embodiment, if Figure 1As shown, the first non-movable electrode assembly includes a non-movable electrode 7 and a non-movable electrode 8, the non-movable electrode 7 is fixed by an electrode anchor 15, the non-movable electrode 8 is fixed by an electrode anchor 16, and a plurality of non-movable comb-tooth electrodes are arranged on the non-movable electrode 7 and the non-movable electrode 8; and the first movable electrode assembly includes a movable electrode 23 and a movable electrode 29 corresponding to the non-movable electrode 7 and the non-movable electrode 8, respectively, and the movable electrode 23 and the movable electrode 29 each include a plurality of movable comb-tooth electrodes. The second non-movable electrode assembly includes a non-movable electrode 11 and a non-movable electrode 12, the non-movable electrode 11 is fixed by an electrode anchor 19, and the non-movable electrode 12 is fixed by an electrode anchor 20; and the second movable electrode assembly includes a movable electrode 28 and a movable electrode 30 corresponding to the non-movable electrode 11 and the non-movable electrode 12, respectively. The third non-movable electrode assembly includes a non-movable electrode 9 and a non-movable electrode 10, wherein the non-movable electrode 9 is fixed by an electrode anchor 17, and the non-movable electrode 10 is fixed by an electrode anchor 18; and the third movable electrode assembly includes a movable electrode 31 and a movable electrode 33 corresponding to the non-movable electrode 9 and the non-movable electrode 10, respectively. The fourth non-movable electrode assembly includes a non-movable electrode 13 and a non-movable electrode 14, wherein the non-movable electrode 13 is fixed by an electrode anchor 21, and the non-movable electrode 14 is fixed by an electrode anchor 22; and the fourth movable electrode assembly includes a movable electrode 32 and a movable electrode 34 corresponding to the non-movable electrode 13 and the non-movable electrode 14, respectively.

[0040] In this embodiment, electrode anchor point 15 and electrode anchor point 19, electrode anchor point 16 and electrode anchor point 20, electrode anchor point 17 and electrode anchor point 21, electrode anchor point 18 and electrode anchor point 22 are all symmetrical about the Y-axis, and the above-mentioned electrode anchor points are all arranged close to the Y-axis to be on the same line with the fixed support frame anchor point 4 to the maximum extent; when the ambient temperature changes, compared with other anchor point layout structures, the expansion and contraction effect caused by the influence of temperature on the change of the detection electrode unit gap can be effectively reduced, thereby ensuring the stable performance of the accelerometer when the ambient temperature changes.

[0041] In this embodiment, the electrode anchor point and the fixed support frame anchor point 4 are both rectangular anchor points, and the long side of the rectangular anchor point is perpendicular to the sensitive axis, which is beneficial to reducing the influence of thermal deformation caused by different materials and different thermal expansion coefficients on the direction of movement; when the ambient temperature changes, compared with other anchor point structures, it can effectively reduce the influence of thermal stress inside the accelerometer structure on the direction of the sensitive structure, thereby ensuring the stable performance of the accelerometer when the ambient temperature changes.

[0042] When the comb-tooth capacitive accelerometer of this embodiment is in use, when there is acceleration input in the sensitive axis direction (X-axis direction), the sensitive mass block frame 3 generates a displacement in the X-direction, resulting in a corresponding change in the capacitance of the detection electrode unit; wherein, the capacitance change trend between the first movable electrode assembly and the first non-movable electrode assembly is consistent with that between the third movable electrode assembly and the third non-movable electrode assembly, forming a first detection electrode unit group; the capacitance change trend between the second movable electrode assembly and the second non-movable electrode assembly is consistent with that between the fourth movable electrode assembly and the fourth non-movable electrode assembly, forming a second detection electrode unit group; the capacitance change magnitude of the first detection electrode unit group and the second detection electrode unit group is the same, but the sign is opposite, that is, when the capacitance of the first detection electrode unit group increases, the capacitance of the second detection electrode unit group decreases, and the decrease amount is the same as the increase amount; and vice versa. By using an appropriate processing circuit to perform differential detection processing on the first detection electrode unit group and the second detection electrode unit group, the input acceleration information can be obtained.

[0043] The comb-tooth capacitive accelerometer of this embodiment can be widely used in detecting the linear acceleration of moving objects in various fields.

[0044] It should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any figure mark in the claims should not be regarded as limiting the claims involved.

[0045] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A comb-tooth capacitive accelerometer, characterized in that: The invention comprises a substrate and an accelerometer structure, wherein the accelerometer structure is arranged on the substrate; the accelerometer structure comprises a fixed support frame, a sensitive mass block frame and a non-movable electrode assembly, wherein the non-movable electrode assembly is fixed on the substrate through an electrode anchor point, and a movable electrode assembly is arranged on the sensitive mass block frame, wherein the movable electrode assembly corresponds to the non-movable electrode assembly one by one, and the corresponding movable electrode assembly and the non-movable electrode assembly form a comb-tooth capacitor structure; the fixed support frame is fixed on the substrate through a fixed support frame anchor point, wherein the fixed support frame anchor point is located at the center of the accelerometer structure, and the fixed support frame is connected to the sensitive mass block frame through an elastic structure, wherein the elastic structure enables the sensitive mass block frame to move along the sensitive axis direction; The fixed support frame is a cross-shaped frame, and the fixed support frame is located in the sensitive mass block frame. The cross-shaped frame includes a longitudinal frame and a transverse frame which are perpendicular to each other. The center line of the transverse frame is collinear with the X-axis, and the center line of the longitudinal frame is collinear with the Y-axis. The two ends of the longitudinal frame are symmetrical about the X-axis, and the two ends of the transverse frame are symmetrical about the Y-axis. The center of the anchor point of the fixed support frame is located at the intersection of the X-axis and the Y-axis; wherein the X-axis is parallel to the sensitive axis; both ends of the transverse frame are provided with connecting parts, and the connecting parts are connected to the sensitive mass block frame through the elastic structure, and the two ends of the longitudinal frame are connected to the sensitive mass block frame through the elastic structure.

2. The comb-tooth capacitive accelerometer according to claim 1, characterized in that: The fixing frame has one and only one anchor point.

3. The comb-tooth capacitive accelerometer according to claim 1, characterized in that: The elastic structure is a single-degree-of-freedom elastic beam.

4. The comb-tooth capacitive accelerometer according to claim 1, characterized in that: One side of the outer edge of the sensitive mass block frame close to the connecting part is provided with anti-suction protrusions; the outer edge is located on the side of the connecting part away from the longitudinal frame, and the outer edge is perpendicular to the X-axis and parallel to the side of the sensitive mass block frame where the anti-suction protrusions are arranged.

5. The comb-tooth capacitive accelerometer according to claim 1, characterized in that: The non-movable electrode components are provided in four, including a first non-movable electrode component, a second non-movable electrode component, a third non-movable electrode component and a fourth non-movable electrode component. The first non-movable electrode component and the second non-movable electrode component are symmetrical about the Y axis, the first non-movable electrode component and the third non-movable electrode component are symmetrical about the X axis, and the second non-movable electrode component and the fourth non-movable electrode component are symmetrical about the X axis.

6. The comb-tooth capacitive accelerometer according to claim 5, characterized in that: The electrode anchor point is arranged close to the Y-axis.

7. The comb-tooth capacitive accelerometer according to claim 1, characterized in that: The electrode anchor point and the fixed support frame anchor point are both rectangular anchor points, and the long sides of the rectangular anchor points are perpendicular to the sensitive axis.

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