Piezoelectric accelerometer
Technical Field
The invention relates to the technical field of accelerometers, in particular to a piezoelectric type accelerometer.
Background
Inertial navigation systems are capable of measuring the acceleration of a vehicle relative to an inertial frame in real time via an accelerometer. At present, the acceleration sensor is mainly of a piezoresistive type, a capacitive type, a piezoelectric type, a force balance type, a micro-mechanical heat convection type and a micro-mechanical resonator. The piezoelectric accelerometer measures acceleration by using a material with a piezoelectric effect, when the acceleration is input, the beam and the thin film structure are deformed by the inertia force generated by the mass block, charges are generated on the surface of the beam and the thin film structure, and the charges or the voltages which are in direct proportion to the input acceleration are output through the charge amplifier or the voltage amplifier. The piezoelectric acceleration sensor has wide dynamic range and good linearity, and is very suitable for detecting impact and vibration.
Most of traditional piezoelectric accelerometers are single-axis accelerometers, and three single axes are required to be assembled to detect three axes, so that the defects of large volume, poor consistency and the like are inevitably caused; meanwhile, the thickness of the mass block is far larger than that of the beam, so that the accelerometer is subjected to torsional deformation in working, and the accurate measurement of the accelerometer is greatly influenced.
Disclosure of Invention
Based on the problems, the invention provides the piezoelectric type accelerometer, which strengthens the stability of the accelerometer and reduces the torsional deformation of the accelerometer under the working condition; the thickness of the mass block is consistent with that of the beam, so that the stability of the accelerometer is enhanced, the torsional deformation is reduced, and a higher dynamic bandwidth can be obtained.
In order to solve the technical problems, the invention provides a piezoelectric accelerometer which comprises a rectangular frame, wherein a cuboid mass block is arranged in the rectangular frame, a first beam, a second beam, a third beam and a fourth beam are fixed on a group of parallel side faces of the mass block, and the ends of the first beam, the second beam, the third beam and the fourth beam far away from the mass block are fixedly connected with the inner wall of the rectangular frame; the first beam and the second beam are symmetrical to each other and are positioned on the same side surface, the third beam and the fourth beam are symmetrical to each other and are positioned on the other side surface parallel to the side surface where the first beam is positioned, a gap is reserved between the first beam and the second beam, a gap is reserved between the third beam and the fourth beam, the first beam and the third beam are symmetrical to each other, and the second beam and the fourth beam are symmetrical to each other; piezoelectric sheets are arranged on the upper surfaces of the first beam, the second beam, the third beam and the fourth beam, and four corners of each piezoelectric sheet are respectively provided with a metal electrode; the thicknesses of the first beam, the second beam, the third beam and the fourth beam are the same as the thickness of the mass block.
Furthermore, the first beam, the second beam, the third beam and the fourth beam are cuboids, and the first beam, the second beam, the third beam and the fourth beam and the mass block form an I-shaped double-shaft piezoelectric accelerometer.
Furthermore, the first beam, the second beam, the third beam and the fourth beam are all L-shaped, and the first beam, the second beam, the third beam, the fourth beam and the mass block form a three-axis piezoelectric accelerometer with the L-shaped beams.
Furthermore, the first beam, the second beam, the third beam, the fourth beam and the mass block are integrally formed through machining.
Compared with the prior art, the invention has the beneficial effects that:
1) the beams are arranged on the two symmetrical sides of the mass block, so that the stability of the accelerometer is enhanced, and the torsional deformation of the accelerometer under the working condition is reduced;
2) the thickness of the mass block is consistent with that of the beam, so that the stability of the accelerometer is further enhanced, and the torsional deformation is reduced; meanwhile, a higher dynamic bandwidth can be obtained.
Drawings
Fig. 1 is a schematic structural diagram of a piezoelectric accelerometer in embodiment 1;
FIG. 2 is a schematic structural view of an I-shaped biaxial piezoelectric accelerometer in example 2;
FIG. 3 is a schematic circuit diagram showing the connection of the "I" -shaped biaxial piezoelectric accelerometer in example 2;
FIG. 4 is a schematic view showing the structure of a three-axis piezoelectric accelerometer having L-shaped beams according to example 3;
FIG. 5 is a schematic circuit diagram showing the connection of the three-axis piezoelectric accelerometer having L-shaped beams in example 3;
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
Example 1:
referring to fig. 1, a piezoelectric accelerometer includes a rectangular frame 101, a rectangular mass block 102 is arranged in the rectangular frame 101, a first beam 103, a second beam 104, a third beam 105 and a fourth beam 106 are fixed on a group of parallel side surfaces of the mass block 102, and the ends of the first beam 103, the second beam 104, the third beam 105 and the fourth beam 106 far from the mass block 102 are all fixedly connected with the inner wall of the rectangular frame 101; the first beam 103 and the second beam 104 are symmetrical to each other and are positioned on the same side face, the third beam 105 and the fourth beam 106 are symmetrical to each other and are positioned on the other side face parallel to the side face where the first beam 103 is positioned, a gap is reserved between the first beam 103 and the second beam 104, a gap is reserved between the third beam 105 and the fourth beam 106, the first beam 103 and the third beam 105 are symmetrical to each other, and the second beam 104 and the fourth beam 106 are symmetrical to each other; piezoelectric sheets are arranged on the upper surfaces of the first beam 103, the second beam 104, the third beam 105 and the fourth beam 106, and a metal electrode is arranged at each of four corners of each piezoelectric sheet; the thickness of the first beam 103, the second beam 104, the third beam 105 and the fourth beam 106 is the same as that of the mass block 102.
In the present embodiment, the material of the mass block 102 and each beam may be structural steel, silicon, alloy, organic glass, etc.; the piezoelectric sheet can be made of piezoelectric materials such as AlN, PZT, ZnO and the like; the metal electrode can be made of Mo, Al, Au, Pt, Ag and other materials; the mass block 102, the beams, the piezoelectric plate and the metal electrode can be integrally formed by micro-machining (MEMS) or conventional machining, so that the accelerometer has good overall stability. The working principle is as follows: the mass block 102 is subjected to a load in a certain direction to generate micro displacement, and then the piezoelectric sheets on the first beam 103, the second beam 104, the third beam 105 and the fourth beam 106 are bent along with the bending of the beams, according to the positive piezoelectric effect, the piezoelectric sheets can generate charges in direct proportion to the acceleration, the acceleration can be deduced by measuring the charges, and then the acceleration in the corresponding axial direction can be deduced by measuring the charge or voltage signal values between different metal electrodes.
The sensitivity of the piezoelectric accelerometer can be the charge sensitivity SqIndicating that the voltage sensitivity S can also be usedvRepresents:
then can pass through
Calculating an acceleration value;
wherein Q isaFor measuring the amount of charge present at the terminals, charge sensitivity SqThe quantity of electric charge generated by the piezoelectric sheet under one unit acceleration can be measured by an instrument; vaFor measuring voltage values of terminals under certain load-related conditionsVoltage sensitivity SvThe voltage value generated by the piezoelectric sheet under one unit acceleration can be measured by an instrument.
Example 2:
as shown in fig. 2 and 3, a piezoelectric accelerometer includes a rectangular frame 101, a rectangular mass 102 is disposed in the rectangular frame 101, the mass 102 fixes a first beam 103, a second beam 104, a third beam 105 and a fourth beam 106 on a set of parallel sides, and the ends of the first beam 103, the second beam 104, the third beam 105 and the fourth beam 106 far from the mass 102 are all fixedly connected with the inner wall of the rectangular frame 101; the first beam 103 and the second beam 104 are symmetrical to each other and are positioned on the same side face, the third beam 105 and the fourth beam 106 are symmetrical to each other and are positioned on the other side face parallel to the side face where the first beam 103 is positioned, a gap is reserved between the first beam 103 and the second beam 104, a gap is reserved between the third beam 105 and the fourth beam 106, the first beam 103 and the third beam 105 are symmetrical to each other, and the second beam 104 and the fourth beam 106 are symmetrical to each other; piezoelectric sheets are arranged on the upper surfaces of the first beam 103, the second beam 104, the third beam 105 and the fourth beam 106, and a metal electrode is arranged at each of four corners of each piezoelectric sheet; the thickness of the first beam 103, the second beam 104, the third beam 105 and the fourth beam 106 is the same as that of the mass block 102.
The first beam 103, the second beam 104, the third beam 105 and the fourth beam 106 are cuboids, and the first beam 103, the second beam 104, the third beam 105 and the fourth beam 106, the mass block 102 and the rectangular frame 101 form an I-shaped biaxial piezoelectric accelerometer.
FIG. 3 is a schematic diagram showing the electrical connection of the metal electrodes of the I-shaped piezoelectric biaxial accelerometer, which has 16 metal electrodes 107-122. The metal electrodes 109, 114, 115, 120 are led out to an electrode connector 123 through wire interconnection, and the metal electrodes 108, 111, 118, 121 are led out to an electrode connector 127 through wire interconnection; when a load in the Z-axis direction is applied, the clamping end of the beam and the end of the connecting mass block 102 deform oppositely, so that the electrode joint 123 and the electrode joint 127 generate electric charges with opposite electric properties, and the acceleration of the Z-axis can be calculated by measuring the electric charges or voltage signals of the electrode joint 123 and the electrode joint 127;
the metal electrodes 107 and 117 are led out to an electrode joint 125 through wire interconnection, and the metal electrodes 112 and 122 are led out to an electrode joint 128 through wire interconnection; when a load in the Y-axis direction is applied, the upper and lower portions of the clamping end of each beam are deformed in opposite directions, so that the electrode contacts 125 and 128 generate electric charges in opposite directions, and the acceleration of the Y-axis can be calculated by measuring the electric charges or voltage signals of the electrode contacts 125 and 128;
the metal electrodes 110 and 113 are led out to an electrode joint 126 through wire interconnection, and the metal electrodes 116 and 119 are led out to an electrode joint 124 through wire interconnection; when a load in the X-axis direction is applied, the left beam and the right beam generate opposite deformations, the electrode contact 126 and the electrode contact 124 generate opposite charges, and the charges or voltage signals of the electrode contact 126 and the electrode contact 124 are measured.
When a load is applied to the Z-axis direction, the electrode terminal 123 and the electrode terminal 127 are used for measuring a Z-axis acceleration signal, while the electrode terminal 125 and the electrode terminal 128 for measuring a Y-axis acceleration signal, the electrode terminal 126 and the electrode terminal 124 for measuring an X-axis acceleration signal are symmetrically connected, charges are cancelled, and the signal output is substantially 0;
when a load is applied to the Y-axis direction, the electrode terminal 125 and the electrode terminal 128 are used for measuring a Y-axis acceleration signal, while the electrode terminal 123 and the electrode terminal 127 for measuring a Z-axis acceleration signal, the electrode terminal 126 and the electrode terminal 124 for measuring an X-axis acceleration signal are symmetrically connected, so that charges are cancelled out, and the signal output is substantially 0;
when a load is applied to the X-axis direction, the electrode terminal 126 and the electrode terminal 124 are used for measuring an X-axis acceleration signal, while the electrode terminal 123 and the electrode terminal 127 for measuring a Z-axis acceleration signal, the electrode terminal 125 and the electrode terminal 128 for measuring a Y-axis acceleration signal are symmetrically connected, so that charges are cancelled out, and the signal output is substantially 0.
Other parts in this embodiment are the same as embodiment 1, and are not described again here.
Example 3:
as shown in fig. 4 and 5, a piezoelectric accelerometer includes a rectangular frame 101, a rectangular mass 102 is disposed in the rectangular frame 101, the mass 102 fixes a first beam 103, a second beam 104, a third beam 105 and a fourth beam 106 on a set of parallel sides, and the ends of the first beam 103, the second beam 104, the third beam 105 and the fourth beam 106 far from the mass 102 are all fixedly connected with the inner wall of the rectangular frame 101; the first beam 103 and the second beam 104 are symmetrical to each other and are positioned on the same side face, the third beam 105 and the fourth beam 106 are symmetrical to each other and are positioned on the other side face parallel to the side face where the first beam 103 is positioned, a gap is reserved between the first beam 103 and the second beam 104, a gap is reserved between the third beam 105 and the fourth beam 106, the first beam 103 and the third beam 105 are symmetrical to each other, and the second beam 104 and the fourth beam 106 are symmetrical to each other; piezoelectric sheets are arranged on the upper surfaces of the first beam 103, the second beam 104, the third beam 105 and the fourth beam 106, and a metal electrode is arranged at each of four corners of each piezoelectric sheet; the thickness of the first beam 103, the second beam 104, the third beam 105 and the fourth beam 106 is the same as that of the mass block 102.
The first beam 103, the second beam 104, the third beam 105 and the fourth beam 106 are all L-shaped, and the first beam 103, the second beam 104, the third beam 105 and the fourth beam 106, the mass block 102 and the rectangular frame 101 form a three-axis piezoelectric accelerometer with L-shaped beams.
As shown in FIG. 4, in the triaxial piezoelectric accelerometer with L-shaped beams, the mass block 102 is a cuboid, a beam I103, a beam II 104, a beam III 105 and a beam IV 106 are arranged on two symmetrical sides of the mass 202, one end of each beam is fixed on the rectangular frame 101, the other end of each beam is connected with the mass block 102, and piezoelectric sheets are arranged on the surfaces of the beams. Metal electrodes 207, 208, 209 and 210 are distributed on the piezoelectric sheet of the first beam 103; metal electrodes 211, 212, 213 and 214 are distributed on the piezoelectric sheet of the second beam 104; metal electrodes 215, 216, 217 and 218 are distributed on the piezoelectric sheet of the beam III 105; metal electrodes 219, 220, 221, 222 are distributed on the piezoelectric sheet of beam four 106.
FIG. 5 is a schematic diagram of the electrical connections of the metal electrodes of the three-axis piezoelectric accelerometer with L-shaped beams, which has 16 metal electrodes 207-222. The metal electrodes 210, 216, 213, 219 are led out to the electrode connector 228 through the wire interconnections, and the metal electrodes 207, 212, 222, 217 are led out to the electrode connector 225 through the wire interconnections; when a load in the Z-axis direction is applied, the clamping end and the end of the connecting mass block 102 will deform oppositely, so that the electrode joint 225 and the electrode joint 228 generate electric charges with opposite electric properties, and the Z-axis acceleration can be calculated by measuring the electric charges or voltage signals of the electrode joint 225 and the electrode joint 228;
the metal electrodes 209 and 215 are led out to an electrode joint 224 through wire interconnection, and the metal electrodes 214 and 210 are led out to an electrode joint 227 through wire interconnection; when a load in the Y-axis direction is applied, the upper and lower portions of the beam near one end of the mass block 102 deform oppositely, so that the electrode joint 224 and the electrode joint 227 generate electric charges with opposite electric properties, and the acceleration of the Y-axis can be calculated by measuring the electric charges or voltage signals of the electrode joint 224 and the electrode joint 227;
the metal electrodes 208 and 211 are led out to an electrode joint 223 through a lead interconnection, and the metal electrodes 218 and 221 are led out to an electrode joint 226 through a lead interconnection; when a load in the X-axis direction is applied, the upper and lower parts of the clamping end of the beam are deformed oppositely, so that the electrode joint 223 and the electrode joint 226 generate electric charges with opposite electric properties, and the acceleration of the X-axis can be calculated by measuring the electric charges or voltage signals of the electrode joint 223 and the electrode joint 226;
when a load is applied to the Z-axis direction, the electrode joint 225 and the electrode joint 228 are used for measuring a Z-axis acceleration signal, the electrode joint 224 and the electrode joint 227 for measuring a Y-axis acceleration signal, the electrode joint 223 and the electrode joint 226 for measuring an X-axis acceleration signal are symmetrically connected, charges are mutually counteracted, and the signal output is basically 0;
when a load is applied to the Y-axis direction, the electrode joint 224 and the electrode joint 227 are used for measuring a Y-axis acceleration signal, the electrode joint 225 and the electrode joint 228 for measuring a Z-axis acceleration signal, the electrode joint 223 and the electrode joint 226 for measuring an X-axis acceleration signal are symmetrically connected, charges are mutually counteracted, and the signal output is basically 0;
when the load in the X-axis direction is applied, the electrode joint 223 and the electrode joint 226 are used for measuring the X-axis acceleration signal, while the electrode joint 225 and the electrode joint 228 for measuring the Z-axis acceleration signal, the electrode joint 224 and the electrode joint 227 for measuring the Y-axis acceleration signal are symmetrically connected, the charges are mutually cancelled, and the signal output is substantially 0.
Other parts in this embodiment are the same as embodiment 1, and are not described again here.
The model specifications of the metal electrodes and the model specifications of the electrode joints in the above embodiments 2 and 3 are the same, and are distinguished by numerical labels for convenience of explaining the working principle of the present invention.
The above is an embodiment of the present invention. The embodiments and specific parameters in the embodiments are only for the purpose of clearly illustrating the verification process of the invention and are not intended to limit the scope of the invention, which is defined by the claims, and all equivalent structural changes made by using the contents of the specification and the drawings of the present invention should be covered by the scope of the present invention.