CN113156165A

CN113156165A - Three-axis acceleration sensor

Info

Publication number: CN113156165A
Application number: CN202110089261.5A
Authority: CN
Inventors: 谢国伟; 金怡; 颜培力
Original assignee: Shanghai Silicon Technology Co ltd
Current assignee: Shanghai Silicon Technology Co ltd
Priority date: 2020-12-31
Filing date: 2021-01-22
Publication date: 2021-07-23
Also published as: CN214585542U

Abstract

The invention provides a three-axis acceleration sensor, which comprises a substrate and at least one anchor point fixedly arranged on the substrate; the sensor further comprises: a first movable mass, a second movable mass, and a third movable mass. The centers of gravity of the second movable mass block and the third movable mass block are respectively positioned at two sides of the anchor point. According to the invention, the two mass blocks with different gravity center positions are arranged, and the influence of external stress on acceleration detection is eliminated through the rotation of the mass blocks.

Description

Three-axis acceleration sensor

Technical Field

The invention relates to the field of MEMS, in particular to a triaxial acceleration sensor.

Background

For the triaxial acceleration sensor, a plurality of mass blocks independent of each other are usually adopted in the prior art to sense acceleration in different axial directions, which has the disadvantages of large volume and complex structure, and thus is not favorable for manufacturing. And adopt single quality piece to detect triaxial acceleration, lead to trans-axial detection easily, the detection precision of Z direction is lower moreover, receives external stress influence easily moreover

Disclosure of Invention

The invention aims to provide a three-axis acceleration sensor which can improve the detection precision.

In order to solve the above problems, the present invention provides a three-axis acceleration sensor, which includes a substrate and at least one anchor point fixedly disposed on the substrate; two directions which are parallel to the surface of the substrate and are mutually vertical are defined as an X direction and a Y direction, the plane is an XY plane, and the direction vertical to the XY plane is a Z direction; the sensor further comprises: the first movable mass block is connected with the anchor point through a first elastic element, and the first elastic element is a bidirectional elastic element in the X direction and the Y direction and is connected with the beam; the second movable mass block is connected with the first movable mass block through a second elastic element, and the second elastic element is a rotating arm taking the Y axis as a rotating shaft, so that the second movable mass block can rotate around an XZ plane; the third elastic element is a rotating arm taking the Y axis as a rotating shaft, so that the third movable mass block can rotate around an XZ plane; the centers of gravity of the second movable mass block and the third movable mass block are respectively positioned at two sides of the anchor point in the Y-axis direction.

According to the invention, the two mass blocks with different gravity center positions are arranged, and the influence of external stress on acceleration detection is eliminated through the rotation of the mass blocks.

Drawings

Fig. 1 and fig. 2 are schematic structural diagrams of a three-axis acceleration sensor according to an embodiment of the present invention.

Fig. 3 to 5 are schematic structural diagrams illustrating deformation of a three-axis acceleration sensor under the influence of external acceleration according to an embodiment of the present invention.

Fig. 6 is a schematic diagram illustrating a technical improvement of a triaxial acceleration sensor with a double symmetric mass according to an embodiment of the present invention.

Fig. 7 is a schematic diagram illustrating a technical improvement of a triaxial acceleration sensor with multiple anchor points according to an embodiment of the present invention.

Detailed Description

The following describes in detail a specific embodiment of the triaxial acceleration sensor according to the present invention with reference to the drawings.

Fig. 1 is a schematic structural diagram of a three-axis acceleration sensor according to this embodiment, which includes: an outer frame 10 fixed on the substrate and at least one anchor point 11 fixedly arranged on the substrate; two opposite directions parallel to the substrate surface and perpendicular to each other are defined as an X direction and a Y direction, a plane on which the two opposite directions are located is an XY plane, and a direction perpendicular to the XY plane is a Z direction. In this embodiment, 4 anchor points are taken as an example for description, and the 4 anchor points are symmetrically arranged with respect to a center O point of the three-axis acceleration sensor and are connected to each other through a beam.

A first movable mass 121 connected to the anchor point 11 through a first elastic element 131, which is a bidirectional elastic element in the X-direction and the Y-direction and connected to the beam; a second movable mass 122 connected to the first movable mass 121 via a second elastic element 132, which is a rotating arm having a Y-axis as a rotating axis, so that the second movable mass 122 can rotate around an XZ plane; and a third movable mass 123 connected to the first movable mass 121 through a third elastic element 133, wherein the third elastic element 133 is a rotating arm having a Y axis as a rotating axis, so that the third movable mass 123 can rotate around an XZ plane; the centers of gravity of the second movable mass 122 and the third movable mass 123 are located on both sides in the Y-axis direction of the anchor point, respectively.

In one embodiment, comb electrodes shown in fig. 1 are used to detect acceleration in the XY plane in order to detect deformation of the structure in response to external acceleration. When acceleration is applied in the X direction, the deformation of the structure is shown in fig. 3, and the working principle is as follows: when acceleration is applied in the X direction, the first elastic element 131 deforms in the X direction, the first movable mass 121 displaces in the X direction, the X electrode gap changes, the differential capacitance of the X electrode group is checked, and the acceleration of X is detected. Since the second elastic element 132 and the third elastic element 133 have high rigidity in the X direction, the relative displacement of the second movable mass 122 and the third movable mass 123 with respect to the first movable mass 121 is large, and the second movable mass 122 and the third movable mass 123 provide an inertial mass for the X-direction inspection, and no transaxial noise is generated, it can be considered that the second elastic element and the third movable mass 121 are displaced in the X direction integrally, and a function of weighting the inertial mass is performed.

In one embodiment, comb electrodes shown in fig. 1 are used to detect acceleration in the XY plane in order to detect deformation of the structure in response to external acceleration. When acceleration exists in the Y direction, the deformation of the structure is shown in FIG. 4, and the working principle is as follows: when there is acceleration in the Y direction, the first elastic element 131 deforms in the Y direction, the first movable mass 121 displaces in the Y direction, the gap between the Y electrodes changes, the differential capacitance of the Y electrode group is checked, and the acceleration of Y is detected. Since the second elastic element 132 and the third elastic element 133 have higher rigidity in the Y direction, the relative displacement of the second movable mass 122 and the third movable mass 123 with respect to the first movable mass 121 is smaller, and the second movable mass 122 and the third movable mass 123 provide an inertial mass for the Y-direction inspection without generating cross-axis noise, they can be regarded as being displaced in the Y direction integrally with the first movable mass 121, and thus, they play a role of weighting the inertial mass.

In order to more accurately detect the acceleration in the Z direction, the present embodiment adopts the electrode arrangement shown in fig. 2 to arrange the electrode structure for detecting the acceleration in the Z direction. At least two first Z electrodes composed of metal layers disposed on the surface of the substrate, in this embodiment, negative electrodes ZN1 and ZN2, and positive electrodes ZP3 and ZP4, respectively located on both sides of the anchor point, corresponding to the electrodes on the surface of the second movable mass 122, to form at least one differential capacitor pair; and at least two second Z electrodes, in this embodiment negative electrodes ZN3 and ZN4, and positive electrodes ZP1 and ZP2, made of metal layers on the substrate, on both sides of the anchor point, corresponding to the electrodes on the surface of the third movable mass 123, forming at least one differential capacitor pair.

The deformation of the structure when there is acceleration in the Z direction is shown in fig. 5. The second elastic element 132 will deform and the second movable mass 122 will rotate, with the main motion form of the second movable mass 122 rotating around the Y-axis, and due to the arrangement of the negative electrodes ZN1 and ZN2 and the positive electrodes ZP3 and ZP4, a differential capacitance will be created, so that the acceleration in the Z-direction can be checked. While the third elastic element 133 will also be deformed, the third movable mass 123 will be caused to rotate about the Y-axis, and its main movement form is that the third movable mass 123 will rotate about the Y-axis, and due to the arrangement of the negative electrodes ZN3 and ZN4 and the positive electrodes ZP1 and ZP2, a differential capacitance will be created, so that the acceleration in the Z-direction can be detected.

Two mass blocks are arranged, and the gravity center position of the third movable mass block 123 is opposite to that of the second movable mass block 122, so that the system error caused by the inclination of the anchor point can be counteracted. The upper part is subjected to Z-direction acceleration, and the lower part is subjected to anchor point offset. It can be seen that when subjected to acceleration in the Z direction, the single mass is tilted, i.e. reflects the acceleration; for the dual-mass block, when the first Z electrode and the second Z electrode are arranged in a crossed manner on two sides of the anchor point, the metal electrode corresponding to the second movable mass block 122 is the positive electrode of the differential capacitor on one side, and the metal electrode corresponding to the third movable mass block 123 on the same side is the negative electrode of the differential capacitor, so that the two mass blocks with opposite offsets contribute to the capacitance value uniformly through the reverse arrangement of the capacitors. When the anchor point is deviated, for the condition of the left side, the inclination of the anchor point directly causes the capacitance value change to cause the zero deviation of the accelerometer, and the inclination of the mass block is caused by the inclination of the anchor point caused by stress or acceleration cannot be distinguished; in the case of the right side, because the first Z electrode and the second Z electrode are arranged in a crossed manner on two sides of the anchor point, when the metal electrode corresponding to the second movable mass block 122 is the positive electrode of the differential capacitor on one side, and the metal electrode corresponding to the third movable mass block 123 on the same side is the negative electrode of the differential capacitor, the contribution of the two substrates in the same inclination direction to the capacitor is opposite, the differential capacitor is generated between the second movable mass block 122 and the first Z electrode, and the differential capacitor generated between the third movable mass block 123 and the second Z electrode is in the same direction, and finally the total differential capacitors are mutually offset to be 0, so that the influence of external stress on acceleration detection is eliminated. Furthermore, the two mass blocks are set to have the same moment relative to the anchor point, so that the differential capacitance can be better accurately zeroed.

A schematic diagram of the above arrangement is shown in fig. 7, and a plurality of anchor points, for example, four anchor points distributed at four corners of a rectangle in the above embodiment, can be used to offset the system error caused by the inclination of the anchor points. For the condition of one anchor point, when the anchor point inclines, the mass block can incline, and when two anchor points with two distances exist in the corresponding inclination direction, the influence caused by the inclination of the mass block can be greatly reduced. Since the above-mentioned situation may occur in both the X and Y directions, two anchor points, i.e., four anchor points in the rectangular four-corner distribution in the above-mentioned embodiment, should be required corresponding to both the X and Y directions.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A triaxial acceleration sensor comprises a substrate and at least one anchor point fixedly arranged on the substrate; two directions which are parallel to the surface of the substrate and are mutually vertical are defined as an X direction and a Y direction, the plane is an XY plane, and the direction vertical to the XY plane is a Z direction; characterized in that the sensor further comprises:

the first movable mass block is connected with the anchor point through a first elastic element, and the first elastic element is a bidirectional elastic element in the X direction and the Y direction and is connected with the beam;

the second movable mass block is connected with the first movable mass block through a second elastic element, and the second elastic element is a rotating arm taking the Y axis as a rotating shaft, so that the second movable mass block can rotate around an XZ plane; and

a third movable mass block connected to the first movable mass block through a third elastic element, wherein the third elastic element is a rotating arm with the Y axis as a rotating shaft, so that the third movable mass block can rotate around the XZ plane;

the centers of gravity of the second movable mass block and the third movable mass block are respectively positioned at two sides of the anchor point in the Y-axis direction.

2. The triaxial acceleration sensor of claim 1, wherein the anchor points are four, are arranged symmetrically about the center of the triaxial acceleration sensor, and are connected to each other by a beam.

3. The triaxial acceleration sensor of claim 1, wherein the X-direction and Y-direction bi-directional elastic elements are right angle folded springs.

4. The three-axis acceleration sensor of claim 1, characterized by further comprising:

at least two first Z electrodes consisting of metal layers arranged on the surface of the substrate are positioned on two sides of the anchor point and correspond to the electrodes on the surface of the second movable mass block to form at least one differential capacitor pair;

and at least two second Z electrodes consisting of metal layers arranged on the surface of the substrate are positioned on two sides of the anchor point and correspond to the electrodes positioned on the surface of the third movable mass block to form at least one differential capacitor pair.

5. The triaxial acceleration sensor of claim 1, wherein the first Z electrode and the second Z electrode are arranged crosswise on both sides of the anchor point, and when the metal electrode corresponding to the second movable mass block is a positive electrode of the differential capacitor on one side, the metal electrode corresponding to the third movable mass block on the same side is a negative electrode of the differential capacitor.

6. The triaxial acceleration sensor of claim 1, wherein the centers of gravity of the second movable mass and the third movable mass are located on both sides of the anchor point in the Y-axis direction, respectively, and the moments with respect to the anchor point are the same.