CN104597287B - Inertial measurement module and three-axis accelerometer - Google Patents

Abstract

The invention discloses an inertial measurement module and a three-axis accelerometer, which include a quality block suspended above a substrate through elastic beams; the elastic beam includes two first elastic beams for connecting the mass blocks, and two An elastic beam cross-connected with a second elastic beam used to connect the substrate, the two first elastic beams are symmetrically distributed along the center line of the X-axis direction of the mass block, and the second elastic beam deviates from the center line of the Y-axis direction of the mass block; the mass block A first movable electrode and a second movable electrode are also provided in the Y-axis and X-axis directions; in the inertial measurement module of the present invention, the movement of a certain axis in the plane will not be affected by the eccentricity of the structure, and two The mass block is connected to the first elastic beam that is symmetrical along the X-axis direction of the mass block, which can ensure that the mass block will not deflect along the first elastic beam, and only linear motion will occur between the mass block and the first elastic beam, thereby The accuracy of detection is improved; and the coupling between axes will not be aggravated.

Description

Inertial measurement module and three-axis accelerometer

technical field

The invention belongs to the field of micro-electro-mechanical (MEMS), more precisely, relates to a micro-electro-mechanical inertial measurement module, and the invention also relates to a three-axis accelerometer.

Background technique

MEMS accelerometer is an inertial device based on MEMS technology, which is used to measure the linear motion acceleration of object motion. It has the characteristics of small size, high reliability, low cost, suitable for mass production, etc., so it has broad market prospects, and its application fields include consumer electronics, aerospace, automobiles, medical equipment and weapons, etc.

At present, there are usually two implementation methods for three-axis accelerometers. One is a patchwork method, which combines three single-axis structures or a dual-axis and a single-axis structure to realize the measurement of three axial accelerations. The second is to use a single structure to realize the measurement of three-axis acceleration. In the single-structure implementation scheme, the z-axis acceleration is generally measured through the eccentric structure. In this scheme, in addition to the z-axis detection motion, the eccentric feature of the structure is used, and the detection motion of a certain axis (such as the x-axis or y-axis) in the plane is also It will be affected by the eccentric characteristics of the structure, so its motion is actually a swing rather than a linear motion. On the one hand, this motion will intensify the inter-axis coupling, and on the other hand, it will reduce the capacitance change, thereby greatly reducing the detection accuracy. On the other hand, when detecting the acceleration of the y-axis, due to the characteristics of its structure, its actual motion may also be a swing instead of a linear motion, which further reduces the detection accuracy.

Contents of the invention

An object of the present invention is to provide a new technical solution for an inertial measurement module.

According to a first aspect of the present invention, an inertial measurement module is provided, comprising:

a substrate, and a first pole piece positioned on the substrate as a lower electrode,

a mass block suspended above the substrate; the mass block is provided with an upper electrode that forms a Z-axis detection capacitor with the first pole piece;

An elastic beam for connecting the substrate and the mass block, the elastic beam includes two first elastic beams located in the X-axis direction and a second elastic beam located in the Y-axis direction and cross-connected with the two first elastic beams, Wherein, the two ends of the second elastic beam are connected to the anchor point of the substrate, and the two ends of the two first elastic beams are respectively connected to the mass block; wherein, the two first elastic beams are along the center line of the mass block in the X-axis direction Symmetrically distributed, the second elastic beam deviates from the center line of the mass block in the Y-axis direction;

The mass block is also respectively provided with a first movable electrode and a second movable electrode in the directions of the Y axis and the X axis; The first fixed electrode and the second fixed electrode of the axis detection capacitor and the X-axis detection capacitor.

Preferably, the mass block is provided with a through hole, and the first elastic beam is connected to side walls on both sides of the through hole.

Preferably, there are two first pole pieces, which are symmetrically distributed on both sides of the second elastic beam.

Preferably, there are two first movable electrodes and/or two second movable electrodes respectively located on opposite sides of the proof mass.

Preferably, a comb-teeth capacitance structure is formed between the first movable electrode and the first fixed electrode and/or between the second movable electrode and the second fixed electrode.

Another object of the present invention is to provide a three-axis accelerometer, which includes two structurally symmetrical inertial measurement modules; and also includes connecting beams respectively connecting the two sides of the mass block in the two inertial measurement modules.

Preferably, the connecting beam includes a beam located in the X-axis direction, and also includes a longitudinal beam located in the Y-axis direction, one end of which is connected to the beam and the other end is connected to the side wall of the mass block; the longitudinal beam and the second elastic beam are in a in a straight line.

Preferably, a reinforcement beam connecting the two beams is also provided, wherein the second elastic beams in the two inertial measurement modules are distributed symmetrically with respect to the reinforcement beam.

Preferably, there are two reinforcing beams, and the two reinforcing beams are arranged in parallel to form a rectangular frame with the cross beam.

Preferably, a slanting beam located in the rectangular frame is also included.

In the inertial measurement module of the present invention, the movement of a certain axis in the plane will not be affected by the eccentricity of the structure. Moreover, two first elastic beams that are symmetrical along the X-axis direction of the mass block are used to connect the mass block. No matter which direction the mass block is accelerated, it can ensure that the mass block will not deflect along the first elastic beam. Only linear motion occurs between the elastic beams, thereby improving the detection accuracy; and the coupling between axes will not be aggravated.

The inventors of the present invention found that, in the prior art, when the mass block is subjected to an acceleration in a certain axis direction, what the mass block actually performs is a swinging motion, not the expected single linear motion or single rotation. Therefore, the technical tasks to be achieved or the technical problems to be solved by the present invention are never thought of or expected by those skilled in the art, so the present invention is a new technical solution.

Other features of the present invention and advantages thereof will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

Fig. 1 is a schematic structural diagram of an inertial measurement module of the present invention.

Fig. 2 is a schematic structural diagram of the elastic beam in Fig. 1 .

Fig. 3 is a schematic structural view of the triaxial accelerometer of the present invention.

Fig. 4 is a schematic structural diagram of the connecting beam in Fig. 3 .

detailed description

Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangements of components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.

The following description of at least one exemplary embodiment is merely illustrative in nature and in no way taken as limiting the invention, its application or uses.

Techniques, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such techniques, methods and devices should be considered part of the description.

In all examples shown and discussed herein, any specific values should be construed as exemplary only, and not as limitations. Therefore, other instances of the exemplary embodiment may have different values.

It should be noted that like numerals and letters denote like items in the following figures, therefore, once an item is defined in one figure, it does not require further discussion in subsequent figures.

Referring to FIG. 1 , the present invention provides an inertial measurement module in a three-axis accelerometer, including a substrate (not shown in the view), on which components such as circuits of the inertial measurement module can be laid out. The substrate is provided with a first pole piece 4 (indicated by a dotted line in the figure) as a lower electrode.

The inertial measurement module of the present invention also includes a mass block 1 located above the substrate, and a support system 5 supporting the mass block 1 above the substrate. The support system 5 can be an elastic beam, and the mass block 1 is suspended above the substrate through the elastic beam.

The elastic beams include two first elastic beams 12 located in the X-axis direction, and a second elastic beam 11 located in the Y-axis direction. The two first elastic beams 12 and the second elastic beams 11 are crossed and fixed together, that is to say , the second elastic beams 11 are respectively cross-fixed with two first elastic beams 12 arranged in parallel. Preferably, the two first elastic beams 12 are distributed symmetrically with respect to the center of the second elastic beam 11 .

Wherein, both ends of the second elastic beam 11 are connected to the anchor point 6 of the substrate, and two first elastic beams 12 are connected to the mass block 1 . The mass block 1 is supported above the substrate by the first elastic beam 12 , the second elastic beam 11 , and the anchor point 6 , so that the mass block 1 is in a suspended state. In a specific embodiment of the present invention, the mass block 1 is provided with a through hole, and the two ends of the first elastic beam 12 are respectively connected to the side walls on both sides of the through hole.

When it needs to be reminded here, the present invention is only for the convenience of describing the relationship between the first elastic beam 12 and the second elastic beam 11. The first elastic beam 12 is defined as the X-axis direction, and the second elastic beam 11 is defined as For the Y-axis direction, of course, the first elastic beam 12 may also be defined as the Y-axis direction, and the second elastic beam 11 is defined as the X-axis direction, and the two are opposite to each other.

In the inertial measurement module of the present invention, the mass block 1 is also respectively provided with a first movable electrode 9 and a second movable electrode 10 in the direction of the Y axis and the X axis; the two movable electrodes are fixed on the mass block 1 , for example, can be set on the edge of the proof mass 1, and can move synchronously with the movement of the proof mass. Correspondingly, the first fixed electrode 2 and the second fixed electrode 3 for forming the Y-axis detection capacitance and the X-axis detection capacitance together with the first movable electrode 9 and the second movable electrode 10 are arranged on the substrate. The two fixed electrodes are fixedly installed on the substrate. When the two movable electrodes move with the mass block 1, the area or distance between the fixed electrodes and the movable electrodes is changed, thereby changing the capacitance of the corresponding capacitor to realize The measurement of acceleration in this direction.

Wherein, there are two first movable electrodes 9 located on opposite sides of the proof mass 1 respectively. Referring to the view direction of FIG. 1, two first movable electrodes 9 are respectively arranged on the upper end and lower end of the mass block 1, and correspondingly, two first fixed electrodes that cooperate with the two first movable electrodes 9 are arranged on the substrate. 2. When there is acceleration in the Y-axis direction, the mass moves along the Y-axis direction, so that the area or distance between one of the first movable electrodes 9 and the first fixed electrode 2 becomes larger, while the other first movable The area or distance between the electrode 9 and the first fixed electrode 2 becomes smaller, and the two Y-axis detection capacitors form a differential capacitance structure, which improves the accuracy of Y-axis acceleration detection.

Based on the same principle, there may also be two second movable electrodes 10, which are respectively located on both sides of the proof mass 1 in the X-axis direction. Referring to the viewing direction of FIG. 1, two second movable electrodes 10 are respectively arranged on the left end and right end of the proof mass 1, and correspondingly, two second fixed electrodes that cooperate with the two second movable electrodes 10 are arranged on the substrate. 3. When there is an acceleration in the X-axis direction, the mass block 1 moves along the X-axis direction, so that the area or distance between one of the second movable electrodes 10 and the second fixed electrode 3 becomes larger, while the other second The area or distance between the movable electrode 10 and the second fixed electrode 3 becomes smaller, and the two X-axis detection capacitors form a differential capacitance structure, which improves the detection accuracy of the X-axis acceleration.

A comb-tooth-shaped capacitor structure can be used between the first movable electrode 9 and the first fixed electrode 2 and/or between the second movable electrode 10 and the second fixed electrode 3, and the structure of the comb-tooth capacitor belongs to the existing technology , which will not be described in detail here.

In the inertial measurement module of the present invention, the two first elastic beams 12 are distributed symmetrically along the centerline of the proof mass in the X-axis direction, and the second elastic beams 11 deviate from the centerline of the proof mass in the Y-axis direction. When the inertial measurement module is subjected to acceleration in the Z-axis direction, due to the eccentric arrangement of the second elastic beam 11 , the mass block 1 deflects around the second elastic beam 11 as the axis.

Specifically, with reference to the viewing direction of FIG. 1 , the two first elastic beams 12 are distributed symmetrically with respect to the centerline of the X-axis direction of the mass block, while the second elastic beams 11 deviate from the centerline of the Y-axis direction of the mass block, that is, The distance from the second elastic beam 11 to the left end of the mass block 1 is not equal to the distance from the second elastic beam 11 to the right end of the mass block 1 . For example, the second elastic beam 11 deviates to the right of the center line of the mass block in the Y-axis direction. The block 1 can rotate relative to the second elastic beam 11 .

The mass block 1 is also provided with an upper electrode (not shown) that forms a Z-axis detection capacitor with the first pole piece 4. In a preferred embodiment of the present invention, the mass block 1 itself is the Z-axis detection capacitor At this time, the proof mass 1, the first movable electrode 9, and the second movable electrode 10 can be used as the ground electrodes of their respective capacitors.

There can be two first pole pieces 4 , which are symmetrically distributed on both sides of the second elastic beam 11 . When there is acceleration in the Z-axis direction, the mass block 1 deflects relative to the second elastic beam 11, that is, the mass block 1 rotates around the second elastic beam 11, thereby changing the distance between the mass block 1 and the first pole piece 4. The distance to realize the change of Z-axis detection capacitance. The distance between the mass block 1 and one of the first pole pieces 4 becomes larger, and the distance between the other first pole piece 4 becomes smaller, so that a differential capacitance can be formed between the two first pole pieces 4 and the mass block structure to improve the accuracy of Z-axis acceleration detection. When there is acceleration in the Y-axis direction, the proof mass 1 is displaced in the Y-axis direction by the deformation of the first elastic beam 12 , so that the acceleration in the Y-axis direction is measured through the first movable electrode 9 and the first fixed electrode 2 . When there is acceleration in the X-axis direction, the proof mass 1 is displaced in the X-axis direction by the deformation of the second elastic beam 11 , so that the acceleration in the X-axis direction is measured through the second movable electrode 10 and the second fixed electrode 3 .

In the inertial measurement module of the present invention, the movement of a certain axis (X axis, Y axis) in the plane will not be affected by the eccentricity of the structure. Moreover, two first elastic beams that are symmetrical along the X-axis direction of the mass block are used to connect the mass block. No matter which direction the mass block is subjected to acceleration, it can be ensured that it will not deflect along the first elastic beam. The mass block and the first Only linear motion occurs between the elastic beams, thereby improving the accuracy of detection; and the coupling between axes will not be exacerbated.

The inertial measurement modules of the present invention can be used in combination to form a three-axis accelerometer, for example, the masses 1 in multiple inertial measurement modules can be connected through connecting beams.

With reference to Fig. 3, a kind of three-axis accelerometer disclosed by the present invention comprises two structurally symmetrical inertial measurement modules, and two connecting beams are used to respectively connect the two sides of the mass block 1 in the two inertial measurement modules; The connecting beam includes a crossbeam 7 located in the X-axis direction, and a longitudinal beam 8 located in the Y-axis direction, one end connected to the crossbeam 7 and the other end connected to the side wall of the proof mass 1; the longitudinal beam 8 is collinear with the second elastic beam 11 , that is to say, the longitudinal beam 8 and the second elastic beam 11 are in a straight line to reduce the influence of the longitudinal beam 8 on the flipping of the mass block along the Z-axis direction; furthermore, the longitudinal beam 8 can be made of non-rigid material production.

Referring to the view direction of FIG. 3 , the upper beam 7 and the longitudinal beam 8 connect the upper side walls of the two mass blocks 1 together; the lower beam 7 and the longitudinal beam 8 connect the lower end side walls of the two mass blocks 1 together; a rigid reinforcement beam 130 is also provided between the two beams 7, and the two beams 7 are connected together by the reinforcement beam 130, and the position of the reinforcement beam 130 on the two beams 7 makes the two inertial measurement The second elastic beams 11 in the module are distributed symmetrically with respect to the reinforcing beam 130 .

In the triaxial accelerometer of the present invention, when subjected to an acceleration in the Z-axis direction, due to the eccentric arrangement between the mass block 1 and the second elastic beam 11, the mass block 1 deflects relative to the second elastic beam 11, through two The first pole piece 4 is tested. And when receiving the acceleration in the X-axis direction, due to the effects of the beam 7, the longitudinal beam 8, the reinforcing beam 130 and the two first elastic beams 12, the mass block 1 can only move in translation in the X-axis direction, thereby improving the The accuracy of X-axis direction detection. When the mass block receives acceleration in the Y-axis direction, since the second elastic beam 11 is symmetrically distributed relative to the reinforcing beam 130, the center of gravity of the Z-axis structure overlaps with the geometric center of gravity, and two first elastic beams 12 are used to connect the mass block 1, thus ensuring that the mass block will only translate in the Y-axis direction without twisting.

In order to further improve the torsion resistance of the connecting beam, two reinforcement beams 130 are provided, and the two reinforcement beams 130 are arranged in parallel to form a rectangular frame with the cross beam 7 . Further, it also includes two slanting beams 131 located in the rectangular frame, and the two slanting beams 131 may be distributed along the diagonals of the rectangular frame, etc., refer to FIG. 4 .

Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and not intended to limit the scope of the present invention. Those skilled in the art will appreciate that modifications can be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

Claims (10)

1. a kind of inertia measuring module, it is characterised in that including：

Substrate, and the first pole piece (4) on substrate as bottom electrode,

The hanging mass (1) in surface；The mass (1) is provided with and the first pole piece (4) composition Z axis detection electric capacity Top electrode；

For connecting substrate and the spring beam of mass (1), the spring beam includes two the first spring beams positioned at X-direction (12) the second spring beam (11) and positioned at Y direction and with two the first spring beam (12) right-angled intersections being connected, wherein, The two ends of second spring beam (11) are connected on the anchor point of substrate (6), two the first spring beams (12) difference quality of connection blocks (1)；Wherein, center line of two first spring beams (12) along mass (1) X-direction is symmetrical, second bullet Property beam (11) deviate mass (1) Y direction center line；

The mass (1) is also respectively provided with the first movable electrode (9), the second movable electrode (10) in Y-axis, X-direction； It is provided with the substrate for separately constituting Y-axis detection electric capacity, X-axis with the first movable electrode (9), the second movable electrode (10) Detect the first fixed electrode (2), the second fixed electrode (3) of electric capacity.

2. inertia measuring module according to claim 1, it is characterised in that：The mass (1) is provided with through hole, described First spring beam (12) is connected on the side wall of through hole both sides.

3. inertia measuring module according to claim 1, it is characterised in that：The quantity of first pole piece (4) has two, It is symmetrically distributed in the both sides of the second spring beam (11).

4. inertia measuring module according to claim 1, it is characterised in that：First movable electrode (9) and/or second Movable electrode (10) is respectively arranged with two, respectively positioned at the relative both sides of mass (1).

5. inertia measuring module according to claim 1, it is characterised in that：First movable electrode (9) fixes electricity with first Broach capacitance structure is constituted between pole (2) and/or between the second movable electrode (10) and the second fixed electrode (3).

6. a kind of three axis accelerometer, it is characterised in that：Including two symmetrical configurations as described in any one of claim 1 to 5 Inertia measuring module；Also include the tie-beam for connecting the both sides of mass (1) in two inertia measuring modules respectively.

7. three axis accelerometer according to claim 6, it is characterised in that：The tie-beam includes being located in X-direction Crossbeam (7), in addition in Y direction, one end and the longeron that is connected with mass (1) side wall of crossbeam (7) connection one end (8)；The longeron (8) and the second spring beam (11) are point-blank.

8. three axis accelerometer according to claim 7, it is characterised in that：It is additionally provided with adding for two crossbeams (7) of connection Brutal (130), wherein, the second spring beam (11) in two inertia measuring modules is symmetrical relative to buttress brace (130).

9. three axis accelerometer according to claim 8, it is characterised in that：The buttress brace (130) is provided with two, two Individual buttress brace (130) is be arranged in parallel, and a rectangle frame is surrounded with crossbeam (7).

10. three axis accelerometer according to claim 9, it is characterised in that：Also include the cant beam being located in rectangle frame (131)。