CN114660326A - Triaxial piezoresistive accelerometer - Google Patents
Triaxial piezoresistive accelerometer Download PDFInfo
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- CN114660326A CN114660326A CN202210123320.0A CN202210123320A CN114660326A CN 114660326 A CN114660326 A CN 114660326A CN 202210123320 A CN202210123320 A CN 202210123320A CN 114660326 A CN114660326 A CN 114660326A
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- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
- G01P15/12—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by alteration of electrical resistance
Abstract
A tri-axial piezoresistive accelerometer, comprising: supporting the frame; a mass block; a plurality of compound cantilever beams; a plurality of piezoresistors distributed on the plurality of compound cantilever beams, wherein: the mass block is suspended in the center of the supporting frame through the compound cantilever beams, and the mass block is connected with the supporting frame through the compound cantilever beams in the X-axis direction and the Y-axis direction which are perpendicular to each other. Compared with the cantilever beam commonly used at present, the compound cantilever beam adopted by the invention has better rigidity, is beneficial to the resetting of the mass block, reduces the system error and improves the measurement accuracy.
Description
Technical Field
The invention relates to the field of sensors, in particular to a three-axis piezoresistive accelerometer.
Background
With the development and popularization of micro-electro-mechanical systems (MEMS), accelerometers are being developed toward miniaturization and integration. Piezoresistive accelerometers are widely favored because of their high sensitivity, good stability, good dynamic response characteristics, low cost of mass production, good process compatibility with semiconductor integrated circuits, and the like. Tri-axial piezoresistive accelerometers typically use the same mass to sense acceleration signals in three directions. When the mass block senses accelerations in different directions, the resistance values of the piezoresistors at different positions can be changed, so that the output voltage of a Wheatstone bridge formed by the piezoresistors is changed, and the magnitude and the direction of the acceleration are detected. The single-mass block triaxial piezoresistive accelerometer has the advantages of small volume, light weight, low cost, low power consumption and the like, and is rapidly developed in recent years.
However, the existing single-mass triaxial piezoresistive accelerometer has the problem of coupling between axes. How to effectively reduce the coupling between the axes is a problem which needs to be solved urgently in the design, production and application of the three-axis piezoresistive accelerometer.
Disclosure of Invention
The present invention is directed to a three-axis piezoresistive accelerometer, which solves the problems mentioned in the background art.
The technical solution of the invention is as follows: a tri-axial piezoresistive accelerometer, comprising:
supporting the frame;
a mass block;
a plurality of compound cantilever beams;
a plurality of piezoresistors distributed on the plurality of compound cantilever beams,
wherein:
the mass block is suspended at the central position of the supporting frame through the compound cantilever beam, and the mass block is connected with the supporting frame through the compound cantilever beam in the X-axis direction and the Y-axis direction which are perpendicular to each other;
an upper surface of the proof mass lies in a plane defined by the X-axis and the Y-axis, and a Z-axis is perpendicular to the upper surface of the proof mass;
the resistance values of the piezoresistors are equal in a non-stressed state;
the piezoresistors with the same number are distributed on each compound cantilever beam;
each compound cantilever beam is provided with at least one piezoresistor arranged along the direction parallel to the X axis and at least one piezoresistor arranged along the direction parallel to the Y axis;
the X axis, the Y axis and the Z axis are three axes in a three-dimensional rectangular coordinate system, and the coordinate system takes the center of the upper surface of the mass block as a coordinate origin.
Preferably, the plurality of compound cantilever beams includes four compound cantilever beams respectively located in an X-axis negative direction, an X-axis positive direction, a Y-axis negative direction, and a Y-axis positive direction.
Preferably, the compound cantilever beam includes a single-ended portion, a double-ended portion, and an intermediate portion connecting the single-ended portion and the double-ended portion;
the single-end portion is connected with the mass block, and the double-end portion is connected with the supporting frame.
Preferably, twenty-four piezoresistors are symmetrically distributed on the four compound cantilever beams, and six piezoresistors are distributed on each compound cantilever beam.
Preferably, six piezoresistors are distributed on the compound cantilever beam, wherein:
the two piezoresistors are positioned at the positions of the two end parts close to the supporting frame;
the two piezoresistors are positioned at the position of the single-end part close to the mass block;
the two piezoresistors are positioned at the middle part close to the position connected with the two end parts and at one side of the middle part close to the mass block.
Preferably, the metal pads are distributed on the supporting frame, and the metal pads are electrically connected with the piezoresistors on the compound cantilever beam through metal leads.
Preferably, twenty-four metal pads are distributed on the supporting frame;
each side of the supporting frame is provided with six metal bonding pads;
the six metal bonding pads on each edge of the supporting frame are electrically connected with the six piezoresistors on the adjacent compound cantilever beams in a one-to-one correspondence mode through metal leads.
Preferably, a plurality of limiting modules, wherein an overload resisting gap in the X-axis direction and the Y-axis direction is left between each limiting module and the mass block.
Preferably, there is one said spacing module at each inner corner of said supporting rim.
Preferably, the mass blocks are respectively positioned above and below the supporting frame, and a Z-axis direction overload-resistant gap is reserved between the mass block and the upper cover plate and between the mass block and the lower cover plate.
Preferably, the wheatstone bridge for measuring the acceleration component of the X axis includes the piezoresistors distributed in the X axis direction on the two compound cantilevers in the X axis direction, and further includes the piezoresistors distributed in the X axis direction on the two compound cantilevers in the Y axis direction.
The Wheatstone bridge for measuring the acceleration component of the Y axis comprises the piezoresistors distributed on the two compound cantilever beams in the Y axis direction along the Y axis direction, and also comprises the piezoresistors distributed on the two compound cantilever beams in the X axis direction along the Y axis direction.
Preferably, the wheatstone bridge for measuring the Z-axis acceleration component includes said piezoresistors distributed on said single-ended portion of said composite cantilever beam and said piezoresistors distributed on said double-ended portion of said composite cantilever beam.
Preferably, six piezoresistors are distributed on the compound cantilever beam, wherein:
the two piezoresistors are positioned at the positions of the two end parts close to the supporting frame;
the two piezoresistors are positioned at the position of the single-end part close to the mass block;
the two piezoresistors are positioned at the position, close to the connection position with the single-end part, of the middle part and are positioned at one side, close to the mass block, of the middle part.
Preferably, the wheatstone bridge for measuring the acceleration component of the X axis includes the piezoresistors distributed in the X axis direction on the two compound cantilevers in the X axis direction, and further includes the piezoresistors distributed in the X axis direction on the two compound cantilevers in the Y axis direction.
The Wheatstone bridge for measuring the acceleration component of the Y axis comprises the piezoresistors distributed on the two compound cantilever beams in the Y axis direction along the Y axis direction, and also comprises the piezoresistors distributed on the two compound cantilever beams in the X axis direction along the Y axis direction.
Preferably, the wheatstone bridge for measuring the Z-axis acceleration component includes said piezoresistors distributed on said single-ended portion of said composite cantilever beam and said piezoresistors distributed on said double-ended portion of said composite cantilever beam.
The invention has the beneficial effects that:
compared with the prior art, the method and the device have the advantages that not only the compressive stress and the tensile stress directly caused by the components but also the compressive stress and the tensile stress caused by the shear stress caused by the components are utilized when the acceleration components of the X axis and the Y axis are measured. In addition, the compound cantilever beam adopted by the invention has better rigidity than the cantilever beam commonly used at present, is beneficial to the resetting of the mass block, reduces the system error and improves the measurement accuracy. Furthermore, the shear stress in the Y-axis (X-axis) direction caused by the acceleration component of the X-axis (Y-axis) is mainly concentrated in the middle part of the compound cantilever beam, so that the influence of the shear stress on the piezoresistors positioned at the single-end part and the double-end part of the compound cantilever beam is reduced, and the inter-axis coupling of the accelerometer is reduced.
Drawings
Fig. 1 is a schematic structural diagram of a three-axis piezoresistive accelerometer according to an embodiment of the present invention;
FIG. 2 is a cross-sectional view taken along line A-A' of FIG. 1;
FIG. 3 is an enlarged view of a portion of FIG. 1;
FIG. 4 is a wiring diagram of the piezoresistor of FIG. 3;
FIG. 5 is a diagram of a Wheatstone bridge formed by varistor connections for measuring an X-axis acceleration component according to an embodiment of the present invention;
FIG. 6 is a diagram of a Wheatstone bridge formed by varistor connections for measuring the acceleration component of the Y-axis according to an embodiment of the present invention;
FIG. 7 is a diagram of a Wheatstone bridge composed of piezo-resistor connections for detecting acceleration components in the Z-axis direction according to an embodiment of the present invention;
FIG. 8 is a schematic structural diagram of another triaxial piezoresistive accelerometer according to an embodiment of the present invention;
fig. 9 is a partially enlarged view of fig. 8.
In the figure: the structure comprises a supporting frame 1, a mass block 2, a compound cantilever beam 3, a compound cantilever beam 31 positioned in the negative direction of an X axis, a compound cantilever beam 32 positioned in the positive direction of the X axis, a compound cantilever beam 33 positioned in the negative direction of a Y axis, a compound cantilever beam 34 positioned in the positive direction of the Y axis, a single-end part 301, a middle part 302, a double-end part 303, a limit module 4, an upper cover plate 5, a lower cover plate 6, piezoresistors R1-R24, a metal pad 7 and a metal lead 8.
Detailed Description
Various exemplary embodiments of the present invention are described in detail below with reference to the accompanying drawings. The description of the exemplary embodiments is merely illustrative and is not intended to limit the invention, its application, or uses. It should be noted that: the relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.
Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.
As described in the background art, the conventional single-mass triaxial piezoresistive accelerometer has the problem of coupling between axes.
In order to solve the above technical problem, the present invention provides a three-axis piezoresistive accelerometer. Fig. 1 is a schematic structural diagram of a three-axis piezoresistive accelerometer according to an embodiment of the present invention; FIG. 2 is a cross-sectional view taken along line A-A' of FIG. 1; FIG. 3 is an enlarged view of a portion of FIG. 1; fig. 4 is a wiring diagram of the piezoresistor of fig. 3.
Referring to fig. 1 to 4, the triaxial piezoresistive accelerometer includes a supporting frame l, a mass 2, and a compound cantilever beam 3. The mass block 2 is suspended in the center of the supporting frame l through the compound cantilever beam 3. The mass block 2 is respectively connected with the supporting frame l through the compound cantilever beam 3 in the X-axis direction and the Y-axis direction which are vertical to each other. The upper surface of the mass 2 lies in a plane defined by an X-axis and a Y-axis, the Z-axis being perpendicular to the upper surface of the mass 2. The X axis, the Y axis and the Z axis are three axes in a three-dimensional rectangular coordinate system. The coordinate system takes the center of the upper surface of the mass 2 as the origin of coordinates.
Note that the upper surface of the mass 2 of the present embodiment is square. In other embodiments of the invention, the shape of the upper surface of the mass 2 may be other centrosymmetric situations, such as octagonal and circular.
The compound cantilever beams 3 comprise four compound cantilever beams positioned between the support frame l and the mass block 2, namely a compound cantilever beam 31, a compound cantilever beam 32, a compound cantilever beam 33 and a compound cantilever beam 34. The compound cantilever beam 31 is positioned in the X-axis negative direction, the compound cantilever beam 32 is positioned in the X-axis positive direction, the compound cantilever beam 33 is positioned in the Y-axis negative direction, and the compound cantilever beam 34 is positioned in the Y-axis positive direction.
The triaxial piezoresistive accelerometer also comprises a plurality of piezoresistors which are symmetrically distributed on the 4 compound cantilever beams. The resistances of the piezoresistors are equal in a state without stress. Each compound cantilever beam is distributed with piezoresistors with the same quantity. Each compound cantilever beam is provided with at least one piezoresistor arranged along the direction parallel to the X axis and at least one piezoresistor arranged along the direction parallel to the Y axis. In the embodiment, twenty-four piezoresistors Rl-R24 are symmetrically distributed on 4 compound cantilever beams, and six piezoresistors are distributed on each compound cantilever beam 3.
As shown in fig. 1, 3 and 4, the compound cantilever beam includes a single-ended portion 301, a double-ended portion 303, and an intermediate portion 302 connecting the single-ended portion 301 and the double-ended portion 303. The present invention does not limit the position of the intermediate portion 302 in a compound cantilever beam, i.e. the length ratio that connects and connects the single-ended portion 301 and the double-ended portion 303.
In this embodiment, the single end portion 301 of the compound cantilever 3 is connected to the mass 2 and the double end portion 303 of the compound cantilever 3 is connected to the support frame 1. Six piezoresistors (R1, R2, R9, R10, R17 and R18) are distributed on the compound cantilever beam 31 positioned in the negative direction of the X axis. Wherein, R1, R2, R17 and R18 are arranged along the direction parallel to the X axis, and R9 and R10 are arranged along the direction parallel to the Y axis. R1 and R2 are located at the double end portions near the support frame 1, R17 and R18 are located at the single end portions near the mass 2, and R9 and R10 are located at the middle portion 302 near the connection with the double end portions and at the side of the middle portion 302 near the mass 2. Six piezoresistors (R5, R6, R13, R14, R21 and R22) are distributed on the compound cantilever beam 32 positioned in the positive direction of the X axis. Wherein, R5, R6, R21 and R22 are arranged along the direction parallel to the X axis, and R13 and R14 are arranged along the direction parallel to the Y axis. R5 and R6 are located at the double end portions near the support frame 1, R21 and R22 are located at the single end portions near the mass 2, and R13 and R14 are located at the middle portion 302 near the connection with the double end portions and at the side of the middle portion 302 near the mass 2. Six piezoresistors (R3, R4, R11, R12, R19 and R20) are distributed on the compound cantilever beam 33 positioned in the negative direction of the Y axis. Wherein, R3, R4, R19 and R20 are arranged along the direction parallel to the Y axis, and R11 and R12 are arranged along the direction parallel to the X axis. R3 and R4 are located at the double end portions near the support frame 1, R19 and R20 are located at the single end portions near the mass 2, and R11 and R12 are located at the middle portion 302 near the connection with the double end portions and at the side of the middle portion 302 near the mass 2. Six piezoresistors (R7, R8, R15, R16, R23 and R24) are distributed on the compound cantilever 344 in the positive direction of the Y axis. Wherein, R7, R8, R23 and R24 are arranged along the direction parallel to the Y axis, and R15 and R16 are arranged along the direction parallel to the X axis. R7 and R8 are located at the double end portions near the support frame 1, R23 and R24 are located at the single end portions near the mass 2, and R15 and R16 are located at the middle portion 302 near the connection with the double end portions and at the side of the middle portion 302 near the mass 2.
The tri-axial piezoresistive accelerometer also comprises a plurality of metal pads distributed on the supporting frame l. The metal bonding pad is electrically connected with the piezoresistor on the compound cantilever beam through a metal lead. In this embodiment, twenty-four metal pads are distributed on the supporting frame l. Each side of the frame support I is provided with six metal pads. Six metal pads on each edge of the supporting frame l are electrically connected with six piezoresistors on the adjacent compound cantilever beams 3 in a one-to-one correspondence mode through metal leads 8.
The triaxial piezoresistive accelerometer further comprises a limiting module. As shown in fig. 1, the support frame 1 has a limiting module 4 at each inner corner. And overload resisting gaps in the X-axis direction and the Y-axis direction are reserved between each limiting module 4 and the mass block 2. When the acceleration component in one direction exceeds the preset maximum load, the limiting module can prevent the mass block 2 from further moving in the direction, and the effect of protecting and protecting the accelerometer is achieved.
The triaxial piezoresistive accelerometer also comprises an upper cover plate 5 and a lower cover plate 6 which are respectively positioned above and below the supporting frame I. Z-axis overload resisting gaps are reserved between the mass block 2 and the upper cover plate 5 and the lower cover plate 6 respectively. When the acceleration component in the Z-axis direction exceeds the preset maximum load, the upper cover plate 5 or the lower cover plate 6 can prevent the mass block 2 from further moving in the Z-axis direction, and the effect of protecting and protecting the accelerometer is achieved.
The principle of measuring acceleration of the provided three-axis piezoresistive accelerometer is explained below. The acceleration of the mass 2 of the accelerometer has components in the X, Y and Z axes. Without loss of generality, the components of the acceleration of the mass 2 in the X, Y and Z axes are positive.
The Wheatstone bridge for measuring the acceleration component of the X axis comprises piezoresistors distributed along the X axis direction on two compound cantilever beams in the X axis direction and also comprises piezoresistors distributed along the X axis direction on two compound cantilever beams in the Y axis direction. The Wheatstone bridge for measuring the acceleration component of the Y axis comprises piezoresistors distributed along the Y axis direction on two compound cantilever beams in the Y axis direction and piezoresistors distributed along the Y axis direction on two compound cantilever beams in the X axis direction.
FIG. 5 is a diagram of a Wheatstone bridge consisting of varistor connections for measuring the X-axis acceleration component according to an embodiment of the present invention. The piezoresistor R5 and the piezoresistor R18 are connected in series to form a first arm of the Wheatstone bridge, the piezoresistor Rl and the piezoresistor R22 are connected in series to form a second arm of the Wheatstone bridge, the piezoresistor R11 and the piezoresistor R16 are connected in series to form a third arm of the Wheatstone bridge, and the piezoresistor R12 and the piezoresistor R15 are connected in series to form a fourth arm of the Wheatstone bridge. The varistor R5 of the first arm and the varistor Rl of the second arm are connected to one input of the wheatstone bridge, and the varistor Rl6 of the third arm and the varistor R15 of the fourth arm are connected to the other input of the wheatstone bridge. The piezoresistor R18 on the first bridge arm and the piezoresistor Rl1 on the third bridge arm are connected to one output end of the Wheatstone bridge, and the piezoresistor R22 on the second bridge arm and the piezoresistor R12 on the fourth bridge arm are connected to the other output end of the Wheatstone bridge.
Referring to fig. 1 and 5, under the action of the positive X-axis acceleration component, the resistances of the piezoresistors R1, R2, R21 and R22 increase, the resistances of the piezoresistors R17, R18, R5 and R6 decrease, and the piezoresistors R9, R10, R13 and R4 do not change. At this time, shear stress is generated in the compound cantilever 33 positioned in the Y-axis negative direction and the compound cantilever 34 positioned in the Y-axis positive direction. In the case where the beam width is much larger than the thickness, the deformation by the shear stress is negligible, and it is considered that the resistance values of R19, R20, R23, R24, R3, R4, R7, and R8 do not change. This shear stress, however, deforms the intermediate portions 302 of the compound cantilever beams 33 and 34, causing the resistances of the piezo-resistors R11 and R16 to increase,the resistances of the piezoresistors R12 and R15 decrease. Thus, the output signal V in FIG. 5outReflecting the magnitude of the X-axis acceleration component.
Referring to fig. 1 and 5, under the action of the positive Y-axis acceleration component, the resistances of the piezoresistors R3, R4, R23 and R24 increase, the resistances of the piezoresistors R19, R20, R7 and R8 decrease, and the piezoresistors R11, R12, R15 and R6 do not change. At this time, shear stress is generated in the compound cantilever beam 31 positioned in the negative X-axis direction and the compound cantilever beam 32 positioned in the positive X-axis direction. In the case where the beam width is much larger than the thickness, the deformation by the shear stress is negligible, and it is considered that the resistance values of R17, R18, R21, R22, R1, R2, R5, and R6 do not change. However, the shear stress deforms the intermediate portions 302 of the compound cantilever beams 31 and 32 such that the resistances of the piezo-resistors R10 and R13 increase and the resistances of the piezo-resistors R9 and R14 decrease. It can be seen that the Y-axis acceleration component does not affect the resistance of the respective piezoresistors in fig. 5, and does not affect the output signal Vout in fig. 5, so that the coupling between the X-axis and the Y-axis is negligible.
Referring to fig. 1 and 5, under the action of the positive Z-axis acceleration component, the resistances of the piezoresistors R17, R18, R19, R20, R21, R22, R23, and R24 increase, the resistances of the piezoresistors R1, R2, R3, R4, R5, R6, R7, and R8 decrease, and the resistances of the piezoresistors R9, R10, R11, R12, R13, R14, R15, and R16 do not change. In the wheatstone bridge shown in fig. 5, since the changes of the piezoresistors R1 and R5 are the same, the changes of the piezoresistors R22 and R18 are the same, the changes of the piezoresistors R12 and R11 are the same, and the changes of the piezoresistors R15 and R16 are the same, it can be seen that the Z-axis acceleration component does not affect the resistance values of the piezoresistors in fig. 5, and does not affect the output signal V in fig. 5outTherefore, the coupling between the X-axis and the Z-axis is negligible.
Fig. 6 is a diagram of a wheatstone bridge formed by connecting piezoresistors for measuring the acceleration component of the Y axis according to the embodiment of the present invention. The piezoresistor R7 and the piezoresistor R20 are connected in series to form a first arm of the Wheatstone bridge, the piezoresistor R3 and the piezoresistor R24 are connected in series to form a second arm of the Wheatstone bridge, the piezoresistor R10 and the piezoresistor R13 are connected in series to form a third arm of the Wheatstone bridge, and the piezoresistor R9 and the piezoresistor R14 are connected in series to form a fourth arm of the Wheatstone bridge. The varistor R7 in the first arm and the varistor R3 in the second arm are connected to one input terminal of the wheatstone bridge, and the varistor Rl3 in the third arm and the varistor R14 in the fourth arm are connected to the other input terminal of the wheatstone bridge. The piezoresistor R20 on the first bridge arm and the piezoresistor R10 on the third bridge arm are connected to one output end of the Wheatstone bridge, and the piezoresistor R24 on the second bridge arm and the piezoresistor R9 on the fourth bridge arm are connected to the other output end of the Wheatstone bridge.
Similarly, the output signal V in FIG. 6outThe magnitude of the Y-axis acceleration component is reflected and the coupling between the Y-axis and the X-axis is negligible and the coupling between the Y-axis and the Z-axis is negligible.
A wheatstone bridge for measuring Z-axis acceleration components includes piezoresistors distributed on a single-ended portion 301 of composite cantilever beam 301 and piezoresistors distributed on a double-ended portion 303 of composite cantilever beam 301.
Fig. 7 is a diagram of a wheatstone bridge formed by connecting piezoresistors and used for detecting an acceleration component in the Z-axis direction according to an embodiment of the present invention. The piezoresistor R2 and the piezoresistor R6 are connected in series to form a first arm of the Wheatstone bridge, the piezoresistor R17 and the piezoresistor R21 are connected in series to form a second arm of the Wheatstone bridge, the piezoresistor R19 and the piezoresistor R23 are connected in series to form a third arm of the Wheatstone bridge, and the piezoresistor R4 and the piezoresistor R8 are connected in series to form a fourth arm of the Wheatstone bridge. The varistor R2 of the first arm and the varistor R17 of the second arm are connected to one input terminal of the wheatstone bridge, and the varistor R23 of the third arm and the varistor R8 of the fourth arm are connected to the other input terminal of the wheatstone bridge. The piezoresistor R6 on the first bridge arm and the piezoresistor R19 on the third bridge arm are connected to one output end of the Wheatstone bridge, and the piezoresistor R21 on the second bridge arm and the piezoresistor R4 on the fourth bridge arm are connected to the other output end of the Wheatstone bridge.
For the same reason, in FIG. 7Output signal VoutThe magnitude of the Z-axis acceleration component is reflected and the coupling between the Z-axis and the X-axis is negligible and the coupling between the Z-axis and the Y-axis is negligible.
In this embodiment, the supporting frame 1, the mass block 2 and the compound cantilever beam 3 therebetween are made of an SOI sheet material by a conventional standard piezoresistive semiconductor micromachining process. The twenty-four piezoresistors arranged on the elastic beam arm 3 are processed and manufactured by the existing diffusion or ion implantation process. The upper cover plate 5 and the lower cover plate 6 are made of Pyrex glass, and the upper cover plate 5 and the lower cover plate 6 are connected with the supporting frame 1 through electrostatic bonding.
In this embodiment, the overall dimensions of the accelerometer are: about 6000 μm in length, about 6000 μm in width and about 2000 μm in height. Wherein the side length of the mass block is about 2400 μm, and the thickness of the mass block is about 300 μm; the beam length of the compound cantilever beam is about 800 μm, the width of the single-end part beam is about 200 μm, the width of the double-end part beam is about 1200, and the beam thickness is about 20 μm; the side length of the supporting frame is about 4000 μm and the width of the frame is about 1000. mu.m.
In the present embodiment, when measuring the acceleration components of the X axis and the Y axis, not only the compressive stress and the tensile stress directly caused by the components but also the compressive stress and the tensile stress caused by the shear stress caused by the components are used. In addition, the compound cantilever beam that this embodiment adopted, cantilever beam commonly used at present has better rigidity, helps the reseing of quality piece, has reduced system error, has improved the measurement accuracy. Furthermore, the shear stress in the Y-axis (X-axis) direction caused by the acceleration component of the X-axis (Y-axis) is mainly concentrated in the middle part of the compound cantilever beam, so that the influence of the shear stress on the piezoresistors positioned at the single-end part and the double-end part of the compound cantilever beam is reduced, and the inter-axis coupling of the accelerometer is reduced.
Optionally, fig. 8 is a schematic structural diagram of another triaxial piezoresistive accelerometer according to an embodiment of the present invention, and fig. 9 is a partially enlarged view of fig. 8. As shown in fig. 8 and 9, in the present embodiment, the double-ended cantilever 3 is a double-ended cantilever including a single-ended portion 301, a double-ended portion 303, and an intermediate portion 302. In the present embodiment, a single end portion of the compound cantilever 3 is connected to the mass block, and a double end portion of the compound cantilever 3 is connected to the support frame 1. Six piezoresistors (R1, R2, R9, R10, R17 and R18) are distributed on the compound cantilever beam 31 positioned in the negative direction of the X axis. Wherein R1 and R2 are located at the double end portions near the support frame 1, R17 and R18 are located at the single end portions near the mass 2, and R9 and R10 are located at the middle portions near the connection with the single end portions and at the side of the middle portion near the mass 2. Six piezoresistors (R5, R6, R13, R14, R21 and R22) are distributed on the compound cantilever beam 32 positioned in the positive direction of the X axis. Wherein R5 and R6 are located at the double end portions near the support frame 1, R21 and R22 are located at the single end portions near the mass 2, and R13 and R14 are located at the middle portions near the connection with the single end portions and at the side of the middle portion near the mass 2. Six piezoresistors (R3, R4, R11, R12, R19 and R20) are distributed on the compound cantilever beam 33 positioned in the negative direction of the Y axis. Wherein R3 and R4 are located at the double end portions near the support frame 1, R19 and R20 are located at the single end portions near the mass 2, and R11 and R12 are located at the middle portions near the connection with the single end portions and at the side of the middle portion near the mass 2. Six piezoresistors (R7, R8, R15, R16, R23 and R24) are distributed on the compound cantilever beam 34 positioned in the positive direction of the Y axis. Wherein R7 and R8 are located at the double end portions near the support frame 1, R23 and R24 are located at the single end portions near the mass 2, and R15 and R16 are located at the middle portions near the connection with the single end portions and at the side of the middle portion near the mass 2.
It should be noted that, in the two embodiments shown in fig. 1 and fig. 8, the numbers of the piezoresistors R9 and R10, R11 and R12, R13 and R14, and R15 and R16 are exchanged. As can be seen from the analysis method of the embodiment shown in fig. 1, in the embodiment shown in fig. 8, the output signal Vout in fig. 5 reflects the magnitude of the acceleration component of the X-axis, and the coupling between the X-axis and the Y-axis is negligible, and the coupling between the X-axis and the Z-axis is negligible; output signal V in FIG. 6outThe magnitude of the acceleration component of the Y axis is reflected, the coupling between the Y axis and the X axis can be ignored, and the coupling between the Y axis and the Z axis can be ignored; in FIG. 7The output signal Vout reflects the magnitude of the Z-axis acceleration component, and the coupling between the Z-axis and the X-axis is negligible, and the coupling between the Z-axis and the Y-axis is negligible.
In the present embodiment, when measuring the acceleration components of the X axis and the Y axis, not only the compressive stress and the tensile stress directly caused by the components but also the compressive stress and the tensile stress caused by the shear stress caused by the components are used. In addition, the compound cantilever beam that this embodiment adopted, cantilever beam commonly used at present has better rigidity, helps the reseing of quality piece, has reduced system error, has improved the measurement accuracy. Furthermore, the shear stress in the Y-axis (X-axis) direction caused by the acceleration component of the X-axis (Y-axis) is mainly concentrated in the middle part of the compound cantilever beam, so that the influence of the shear stress on the piezoresistors positioned at the single-end part and the double-end part of the compound cantilever beam is reduced, and the inter-axis coupling of the accelerometer is reduced.
The above description is only an example of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (15)
1. A tri-axial piezoresistive accelerometer, comprising:
supporting the frame;
a mass block;
a plurality of compound cantilever beams;
a plurality of piezoresistors distributed on the plurality of compound cantilever beams,
wherein:
the mass block is suspended at the center of the supporting frame through the compound cantilever beams, and the mass block is connected with the supporting frame through the compound cantilever beams in the X-axis direction and the Y-axis direction which are perpendicular to each other;
an upper surface of the proof mass lies in a plane defined by the X-axis and the Y-axis, a Z-axis being perpendicular to the upper surface of the proof mass;
the resistance values of the piezoresistors are equal in a non-stressed state;
the piezoresistors with the same number are distributed on each compound cantilever beam;
each compound cantilever beam is provided with at least one piezoresistor arranged along the direction parallel to the X axis and at least one piezoresistor arranged along the direction parallel to the Y axis;
the X axis, the Y axis and the Z axis are three axes in a three-dimensional rectangular coordinate system, and the coordinate system takes the center of the upper surface of the mass block as a coordinate origin.
2. The accelerometer of claim 1, wherein:
the plurality of compound cantilever beams comprise four compound cantilever beams which are respectively positioned in the X-axis negative direction, the X-axis positive direction, the Y-axis negative direction and the Y-axis positive direction.
3. The accelerometer of claim 2, wherein:
the compound cantilever beam includes a single-ended portion, a double-ended portion, and an intermediate portion connecting the single-ended portion and the double-ended portion;
the single-end part is connected with the mass block, and the double-end part is connected with the supporting frame.
4. An accelerometer according to claim 3, wherein:
twenty-four piezoresistors are symmetrically distributed on the four compound cantilever beams, and six piezoresistors are distributed on each compound cantilever beam.
5. The accelerometer of claim 4, wherein:
six piezoresistors are distributed on the compound cantilever beam, wherein:
the two piezoresistors are positioned at the positions of the two end parts close to the supporting frame;
the two piezoresistors are positioned at the position of the single-end part close to the mass block;
the two piezoresistors are positioned at the middle part close to the position connected with the two end parts and at one side of the middle part close to the mass block.
6. The accelerometer of claim 5, further comprising:
a plurality of metal pads distributed on the support bezel, wherein the plurality of metal pads are electrically connected with the piezoresistors on the compound cantilever beam through metal leads.
7. The accelerometer of claim 6, wherein:
twenty-four metal pads are distributed on the supporting frame;
each side of the supporting frame is provided with six metal bonding pads;
the six metal bonding pads on each edge of the supporting frame are electrically connected with the six piezoresistors on the adjacent compound cantilever beams in a one-to-one correspondence mode through metal leads.
8. The accelerometer of claim 1, further comprising:
and the overload resisting gaps are reserved between each limiting module and the mass block in the X-axis direction and the Y-axis direction.
9. The accelerometer of claim 8, wherein:
and each inner angle of the supporting frame is provided with one limiting module.
10. The accelerometer of claim 1, further comprising:
and the upper cover plate and the lower cover plate are respectively positioned above and below the supporting frame, and Z-axis overload resisting gaps are reserved between the mass blocks and the upper cover plate and between the mass blocks and the lower cover plate.
11. The accelerometer of claim 5, wherein:
the Wheatstone bridge for measuring the acceleration component of the X axis comprises the piezoresistors distributed along the X axis direction on the two compound cantilever beams in the X axis direction, and also comprises the piezoresistors distributed along the X axis direction on the two compound cantilever beams in the Y axis direction.
The Wheatstone bridge for measuring the acceleration component of the Y axis comprises the piezoresistors distributed on the two compound cantilever beams in the Y axis direction along the Y axis direction, and also comprises the piezoresistors distributed on the two compound cantilever beams in the X axis direction along the Y axis direction.
12. The accelerometer of claim 5, wherein:
a wheatstone bridge for measuring a Z-axis acceleration component comprising said piezoresistors distributed on said single-ended portion of said composite cantilever beam and said piezoresistors distributed on said double-ended portion of said composite cantilever beam.
13. The accelerometer of claim 4, wherein:
six piezoresistors are distributed on the compound cantilever beam, wherein:
the two piezoresistors are positioned at the positions of the two end parts close to the supporting frame;
the two piezoresistors are positioned at the position of the single-end part close to the mass block;
the two piezoresistors are positioned at the position, close to the connection position with the single-end part, of the middle part and are positioned at one side, close to the mass block, of the middle part.
14. The accelerometer of claim 13, wherein:
the Wheatstone bridge for measuring the acceleration component of the X axis comprises the piezoresistors distributed along the X axis direction on the two compound cantilever beams in the X axis direction, and also comprises the piezoresistors distributed along the X axis direction on the two compound cantilever beams in the Y axis direction.
The Wheatstone bridge for measuring the acceleration component of the Y axis comprises the piezoresistors distributed on the two compound cantilever beams in the Y axis direction along the Y axis direction, and also comprises the piezoresistors distributed on the two compound cantilever beams in the X axis direction along the Y axis direction.
15. The accelerometer of claim 13, wherein:
a wheatstone bridge for measuring a Z-axis acceleration component comprising said piezoresistors distributed on said single-ended portion of said composite cantilever beam and said piezoresistors distributed on said double-ended portion of said composite cantilever beam.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210123320.0A CN114660326A (en) | 2022-02-10 | 2022-02-10 | Triaxial piezoresistive accelerometer |
| PCT/CN2022/077535 WO2023151129A1 (en) | 2022-02-10 | 2022-02-23 | Triaxial piezoresistive accelerometer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210123320.0A CN114660326A (en) | 2022-02-10 | 2022-02-10 | Triaxial piezoresistive accelerometer |
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| CN114660326A true CN114660326A (en) | 2022-06-24 |
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| CN202210123320.0A Withdrawn CN114660326A (en) | 2022-02-10 | 2022-02-10 | Triaxial piezoresistive accelerometer |
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| CN (1) | CN114660326A (en) |
| WO (1) | WO2023151129A1 (en) |
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| JP2004177233A (en) * | 2002-11-26 | 2004-06-24 | Matsushita Electric Works Ltd | Semiconductor acceleration sensor |
| CN101042411A (en) * | 2007-04-19 | 2007-09-26 | 中北大学 | Three-axis piezoresistance micro-accelerometer |
| WO2012106799A1 (en) * | 2011-02-07 | 2012-08-16 | The Governors Of The University Of Alberta | Piezoresistive load sensor |
| CN111735989A (en) * | 2020-05-29 | 2020-10-02 | 湖州久鼎电子有限公司 | Triaxial piezoresistive accelerometer |
| CN111766401A (en) * | 2020-05-28 | 2020-10-13 | 湖州久鼎电子有限公司 | Triaxial piezoresistive accelerometer |
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| US4901570A (en) * | 1988-11-21 | 1990-02-20 | General Motors Corporation | Resonant-bridge two axis microaccelerometer |
| US5507182A (en) * | 1993-02-18 | 1996-04-16 | Nippondenso Co., Ltd. | Semiconductor accelerometer with damperless structure |
| JP2007101413A (en) * | 2005-10-05 | 2007-04-19 | Sharp Corp | Acceleration detecting device |
| CN102768291B (en) * | 2012-07-21 | 2014-06-25 | 中北大学 | Piezoresistive monolithic integrated four-beam tri-axial accelerometer |
| CN103575932B (en) * | 2013-11-20 | 2016-03-02 | 大连理工大学 | A kind of MEMS piezoresistive accelerometer |
| CN107271724A (en) * | 2017-05-18 | 2017-10-20 | 中北大学 | Single chip integrated pressure resistance type three axis accelerometer and preparation method |
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2022
- 2022-02-10 CN CN202210123320.0A patent/CN114660326A/en not_active Withdrawn
- 2022-02-23 WO PCT/CN2022/077535 patent/WO2023151129A1/en unknown
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004177233A (en) * | 2002-11-26 | 2004-06-24 | Matsushita Electric Works Ltd | Semiconductor acceleration sensor |
| CN101042411A (en) * | 2007-04-19 | 2007-09-26 | 中北大学 | Three-axis piezoresistance micro-accelerometer |
| WO2012106799A1 (en) * | 2011-02-07 | 2012-08-16 | The Governors Of The University Of Alberta | Piezoresistive load sensor |
| CN111766401A (en) * | 2020-05-28 | 2020-10-13 | 湖州久鼎电子有限公司 | Triaxial piezoresistive accelerometer |
| CN111735989A (en) * | 2020-05-29 | 2020-10-02 | 湖州久鼎电子有限公司 | Triaxial piezoresistive accelerometer |
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| WO2023151129A1 (en) | 2023-08-17 |
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