CN107782916B

CN107782916B - Three-axis accelerometer

Info

Publication number: CN107782916B
Application number: CN201610743219.XA
Authority: CN
Inventors: 邹波; 郑青龙
Original assignee: Shendi Semiconductor Shaoxing Co ltd
Current assignee: Shendi Semiconductor Shaoxing Co ltd
Priority date: 2016-08-27
Filing date: 2016-08-27
Publication date: 2021-07-09
Anticipated expiration: 2036-08-27
Also published as: CN107782916A

Abstract

The invention discloses a triaxial accelerometer which comprises a mass block provided with grooves, wherein the grooves penetrate through the upper end surface and the lower end surface of the mass block and are symmetrical along the X-axis direction and the Y-axis direction; the mass block is connected to the fixed anchor point through the combined beam arranged in the groove. The three-axis accelerometer can greatly improve the sensitivity of the sensor, reduce the sensitivity quality and reduce the area of the three-axis accelerometer.

Description

Three-axis accelerometer

Technical Field

The invention relates to the technical field of MEMS, in particular to a triaxial accelerometer.

Background

Micro-accelerometers manufactured based on Micro-Electro-Mechanical-systems (MEMS) have been increasingly used in a wide variety of fields, such as industry, medical treatment, civilian use, and military use, due to their advantages, such as small size, low cost, good integration, and excellent performance.

At present, the standard configuration is already formed in the application of various products such as mobile terminals, cameras, game pads, navigators and the like. In the development process, a capacitive type, a resistive type and a piezoelectric type are mainly applied mechanisms as a mode for detecting acceleration; among them, the capacitive accelerometer is the most popular accelerometer because of its simple structure, low cost, and can possess the advantages of higher sensitivity and linearity in the low frequency range.

Disclosure of Invention

The invention aims to provide a triaxial accelerometer which can solve the problem of low sensitivity efficiency.

In order to achieve the above object, the present invention provides a triaxial accelerometer, comprising a mass block with a groove, wherein the groove penetrates through the upper and lower end surfaces of the mass block, and the groove is symmetrical along both the X-axis direction and the Y-axis direction; the mass block is connected to the fixed anchor point through the combined beam arranged in the groove.

Compared with the prior art, the triaxial accelerometer provided by the invention has the advantages that the mass block is connected to the fixed anchor point by utilizing the combined beam, and the combined beam is matched with the groove of the mass block; the grooves are symmetrical along the X-axis direction and the Y-axis direction, so that the mass blocks are divided into symmetrical shapes by the grooves; the triaxial accelerometer shares one mass block on an X axis, a Y axis and a Z axis, so that the translation of the mass block in the X axis, the Y axis and the Z axis direction is shared in the detection process, the sensitivity of the sensor is greatly improved, the sensitive quality is reduced, and the area of the triaxial accelerometer can be reduced.

Preferably, the groove is in an I shape which is symmetrical up and down and left and right, and comprises an upper horizontal groove, a lower horizontal groove and a communicating groove connected with the two horizontal grooves; the combined beam comprises spring beams which are respectively arranged in the two horizontal grooves and a rigid beam which is communicated with the two spring beams.

By adopting the arrangement mode, the structure of the triaxial accelerometer is further optimized, so that the mass block generates translation when the acceleration of an X axis, a Y axis and a Z axis is detected, the sensitivity efficiency is improved, and the detection efficiency of the triaxial accelerometer is improved.

Preferably, two of the horizontal grooves are arranged in parallel to the X axis, and the communication groove is arranged in parallel to the Y axis.

Preferably, the groove is disposed at a right middle portion of the mass.

Preferably, the fixing anchor is disposed outside the groove.

Preferably, the acceleration sensor further comprises detection capacitors for detecting the accelerations of the X axis, the Y axis and the Z axis.

Preferably, the detection capacitors specifically include 4X-axis detection capacitors for detecting the X-axis acceleration, 4Y-axis detection capacitors for detecting the Y-axis acceleration, and 4Z-axis detection capacitors for detecting the Z-axis acceleration.

Preferably, the 4X-axis detection capacitors, the 4Y-axis detection capacitors and the 4Z-axis detection capacitors are all vertically and bilaterally symmetrical with the center position of the mass block.

Preferably, the 4X-axis detection capacitors, the 4Y-axis detection capacitors and the 4Z-axis detection capacitors extend to the edge of the mass block in sequence.

Preferably, the detection capacitors are four capacitors that are vertically and horizontally symmetrical with respect to a center position of the mass block.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a schematic diagram of a three-axis accelerometer according to an embodiment of the invention;

FIG. 2 is a schematic view of the comb teeth of the Z-axis fixed electrode and the comb teeth of the mass block of FIG. 1;

fig. 3 is a schematic diagram of another triaxial accelerometer according to an embodiment of the present invention.

Wherein:

11-14-first X-axis detection capacitor-fourth X-axis detection capacitor, 21-24-first Y-axis detection capacitor-fourth Y-axis detection capacitor, 31-34-first Z-axis detection capacitor-fourth Z-axis detection capacitor, comb teeth of 4-Z-axis fixed electrodes, 5-fixed anchor points, 61-spring beams, 62-rigid beams, 7-mass blocks, 71-mass blocks, and 81-84-first capacitor-fourth capacitors.

Detailed Description

The core of the invention is to provide a triaxial accelerometer which can improve the detection efficiency and reduce the influence of stress on the performance of a chip.

In order that those skilled in the art will better understand the disclosure, the invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

Referring to fig. 1, fig. 2 and fig. 3, fig. 1 is a schematic diagram of a three-axis accelerometer according to an embodiment of the invention; FIG. 2 is a schematic view of the comb teeth of the Z-axis fixed electrode and the comb teeth of the mass block of FIG. 1; fig. 3 is a schematic diagram of another triaxial accelerometer according to an embodiment of the present invention.

For the prior art three-axis accelerometer, a common solution is to share the masses of three axes. However, the mass is twisted in the direction of the out-of-plane motion, so that the closer to the center of the rotation axis, the lower its sensitivity; conversely, the higher the sensitivity; this has a great influence on the sensitivity linearity of the sensor, and is also not conducive to the reduction of inertial mass and corresponding area due to low sensitivity efficiency.

In the present specification, taking the attached fig. 1 as an example, the horizontal direction is the X axis; in the same plane, the direction vertical to the X axis is the Y axis; the Z axis is perpendicular to the X axis and the Y axis.

The invention provides a three-axis accelerometer, as shown in the attached figure 1 of the specification; the mass block 7 is provided with a groove which penetrates through the upper end surface and the lower end surface of the mass block 7; the grooves are symmetrical up and down and left and right, namely, the grooves are symmetrical along the X-axis direction and the Y-axis direction; and a combined beam is arranged in the groove, and the mass block 7 is connected with the fixed anchor point 5 through the combined beam.

When the acceleration in the X-axis direction, the Y-axis direction and the Z-axis direction is detected, the mass block is shared, and the mass block can translate in three directions to replace a torsional movement mode in the prior art, so that the sensitivity efficiency of the three-axis accelerometer is improved, and the detection efficiency is improved.

Aiming at the specific shapes of the groove and the combination beam, the invention provides a more preferable embodiment; as shown in the attached figure 1 of the specification, the groove is in an I shape which is symmetrical up and down and left and right, the I-shaped groove comprises an upper horizontal groove and a lower horizontal groove, and a communicating groove is communicated between the two horizontal grooves; the composite beam comprises two spring beams 61 and a rigid beam 62, the two spring beams 61 are respectively positioned in the two horizontal grooves, and the rigid beam 62 is positioned in the communicating groove.

Obviously, the present invention may more preferably arrange the two horizontal grooves in parallel to the X-axis and the communicating groove in parallel to the Y-axis, so that the sensitivity efficiency is more superior in detecting the acceleration. The fixed anchor points 5 are arranged on the outer sides of the grooves; the fixed anchor points 5 are preferably located in the Y-axis direction where the communication grooves are located, so that the shape and the structure of the three-axis accelerometer are more symmetrical, and the detection efficiency of the three-axis accelerometer is improved.

In addition, the three-axis accelerometer further includes sensing capacitors for sensing the acceleration of the X-axis, the Y-axis, and the Z-axis. The present invention provides two embodiments as follows for the arrangement of the detection capacitor.

The first embodiment: the detection capacitors specifically include 4X-axis detection capacitors for detecting X-axis acceleration, 4Y-axis detection capacitors for detecting Y-axis acceleration, and 4Z-axis detection capacitors for detecting Z-axis acceleration, as shown in fig. 1 of the specification.

When acceleration along the X axis is input, the mass block 7 translates along the X axis direction, and at this time, the 4X axis detection capacitors with the same initial value will generate slight changes. By accurately designing the directions of the comb teeth of the four capacitors, the capacitance values of the first X-axis detection capacitor 11 and the fourth X-axis detection capacitor 14 can be increased, the capacitance values of the second X-axis detection capacitor 12 and the third X-axis detection capacitor 13 are decreased, the relative change of the capacitance detection capacitor and the third X-axis detection capacitor (delta C11-delta C12-delta C13+ delta C14) can be measured by a capacitance detection and signal processing circuit, and the input X-axis acceleration can be obtained by reverse thrust.

When acceleration along the Y axis is input, the mass block 7 translates along the Y axis. At this time, the 4Y-axis detection capacitors for detecting the Y-axis acceleration having the same initial value are slightly changed. By accurately designing the directions of the comb teeth of these four capacitors, the capacitance values of the first Y-axis detection capacitor 21 and the second Y-axis detection capacitor 22 can be increased, and the capacitance values of the third Y-axis detection capacitor 23 and the fourth Y-axis detection capacitor 24 can be decreased. Therefore, the capacitance detection and signal processing circuit can be used to measure the relative change (Δ C21+ Δ C22- Δ C23- Δ C24), and the magnitude of the input Y-axis acceleration can be obtained by reverse estimation.

When acceleration along the Z-axis is input, the mass 7 translates along the Z-axis. As shown in fig. 2, the length of the comb teeth 71 of the mass block is greater than the length of the comb teeth 4 of the Z-axis fixed electrode; the 4Z-axis detection capacitors for detecting the Z-axis acceleration operate in a step-up/step-down manner, so that the 4Z-axis detection capacitors having the same initial value also slightly change at this time. By accurately designing the height directions of the comb teeth of the four capacitors, the capacitance values of the first Z-axis detection capacitor 31 and the third Z-axis detection capacitor 33 can be increased, and the capacitance values of the second Z-axis detection capacitor 32 and the fourth Z-axis detection capacitor 34 can be decreased. Therefore, the capacitance detection and signal processing circuit can be used to measure the relative change (Δ C31- Δ C32+ Δ C33- Δ C34, and the input Z-axis acceleration can be obtained by reverse estimation.

Of course, the 4X-axis detection capacitors, the 4Y-axis detection capacitors, and the 4Z-axis detection capacitors are all vertically and laterally symmetrical with the center position of the mass block, and as shown in fig. 1 of the specification, the 4X-axis detection capacitors, the 4Y-axis detection capacitors, and the 4Z-axis detection capacitors sequentially extend toward the edge of the mass block 7. Therefore, on the premise of effectively detecting the acceleration of the X axis, the acceleration of the Y axis and the acceleration of the Z axis, the shape of the three-axis accelerometer can be symmetrical, and the influence of external stress on the performance of the chip is reduced.

For the setting mode of the detection capacitor, the invention provides a second implementation mode:

the detection capacitors are specifically four capacitors which are symmetrical up, down, left and right with respect to the center position of the mass block 7, as shown in the attached figure 3 of the specification. When the above-mentioned 4X-axis detection capacitors, 4Y-axis detection capacitors and 4Z-axis detection capacitors are integrated into four capacitors, the directions and heights of the comb teeth of the four capacitors can be set as required to the operating principle described below.

When acceleration along the X-axis is input, the mass 7 translates along the X-axis. The capacitance values of the first capacitor 81 and the fourth capacitor 84 are increased, but the capacitance values of the second capacitor 82 and the third capacitor 83 are decreased. Therefore, the relative change (delta C81-delta C82-delta C83+ delta C84) can be finally measured by using the capacitance detection and signal processing circuit, the influence of the capacitance change of the sensitive other two axial directions is small and can be ignored, and therefore the magnitude of the input X-axis acceleration can be obtained by means of reverse estimation.

When acceleration along the Y-axis is input, the mass 7 translates along the Y-axis. Similarly, the capacitance values of the first capacitor 81 and the second capacitor 82 are increased, but the capacitance values of the third capacitor 83 and the fourth capacitor 84 are decreased. Therefore, the capacitance detection and signal processing circuit can be used to measure the relative change (Δ C81+ Δ C82- Δ C83- Δ C84), and the magnitude of the input Y-axis acceleration can be obtained by reverse estimation.

When acceleration input along the Z-axis occurs, the mass 7 translates along the Z-axis. The capacitance values of the first capacitor 81 and the third capacitor 83 are increased, but the capacitance values of the second capacitor 82 and the fourth capacitor 84 are decreased. Therefore, the capacitance detection and signal processing circuit can be used to measure the relative change (Δ C81- Δ C82+ Δ C83- Δ C84), and the magnitude of the input Z-axis acceleration can be obtained by reverse estimation.

According to the three-axis accelerometer provided by the invention, the sensitive movement modes of the mass block 7 in 3 linear directions are all translational movements through the connection mode of the I-shaped connecting beam, and compared with the sensitive mode of the traditional accelerometer, the sensitivity of a sensor is greatly improved; and the detection mode of the synthesized capacitor is combined, so that the area of the chip is further greatly reduced, and the production cost of the product is reduced.

It is noted that, in this specification, relational terms such as first and second, and the like are used solely to distinguish one entity from another entity without necessarily requiring or implying any actual such relationship or order between such entities.

The three-axis accelerometer provided by the present invention is described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

Claims

1. A triaxial accelerometer is characterized by comprising a mass block provided with grooves, wherein the grooves penetrate through the upper end surface and the lower end surface of the mass block and are symmetrical along the X-axis direction and the Y-axis direction; the mass block is connected to the fixed anchor point through the combined beam arranged in the groove; the groove is in an I shape which is symmetrical up and down and left and right, and comprises an upper horizontal groove, a lower horizontal groove and a communicating groove connected with the two horizontal grooves; the combined beam comprises spring beams respectively arranged in the two horizontal grooves and a rigid beam communicated with the two spring beams; the two horizontal grooves are arranged in parallel to an X axis, and the communication groove is arranged in parallel to a Y axis; the groove is arranged in the middle of the mass block; the fixed anchor points are arranged on the outer sides of the grooves and located in the Y-axis direction where the communication grooves are located.

2. The tri-axial accelerometer of claim 1, further comprising sensing capacitors to sense the X-, Y-, and Z-axis accelerations.

3. The triaxial accelerometer of claim 2, wherein the sensing capacitors specifically include 4X-axis sensing capacitors for sensing the X-axis acceleration, 4Y-axis sensing capacitors for sensing the Y-axis acceleration, and 4Z-axis sensing capacitors for sensing the Z-axis acceleration.

4. The triaxial accelerometer of claim 3, wherein 4 of said X-axis sensing capacitors, 4 of said Y-axis sensing capacitors and 4 of said Z-axis sensing capacitors are all vertically and laterally symmetric about a center position of said proof mass.

5. The tri-axial accelerometer of claim 4, wherein 4 of said X-axis sensing capacitors, 4 of said Y-axis sensing capacitors, and 4 of said Z-axis sensing capacitors extend sequentially toward an edge of said proof mass.

6. The triaxial accelerometer of claim 2, wherein the sensing capacitors are specifically four capacitors that are vertically and laterally symmetric about a central position of the proof mass.