Bending shear coupling type acceleration sensor and forming method thereof

Abstract

The invention discloses a bending-shearing coupling type acceleration sensor and a forming method thereof, and belongs to the field of sensors, the bending-shearing coupling type acceleration sensor comprises an upper shell and a lower shell, an internal thread and a step are arranged in the upper shell, an external thread is arranged on the lower shell, and the upper shell and the lower shell are in threaded connection and jointly define a containing cavity; a metal piezoelectric composite sensitive element, a first mass block, a screw rod and a second mass block are arranged in the containing cavity, the metal piezoelectric composite sensitive element comprises a piezoelectric plate group, an electrode plate group and a second electrode plate, and the piezoelectric plate group comprises a first piezoelectric plate and a second piezoelectric plate which are radially polarized and opposite in polarization direction; the electrode plate group comprises a first electrode plate and a third electrode plate, the first electrode plate, the first piezoelectric plate, the second electrode plate, the second piezoelectric plate and the third electrode plate are sequentially and coaxially arranged and bonded, and the edge of the metal piezoelectric composite sensitive element is tightly pressed between the upper shell and the lower shell. And the charge sensitivity of the acceleration sensor is improved by utilizing the bending-shearing coupling effect of the radial polarization piezoelectric material.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and in particular relates to a bending-shear coupling acceleration sensor and a forming method thereof. Background Art

[0002] Accelerometers, which measure the acceleration of an object, are widely used in health monitoring applications such as aircraft engines and nuclear power plants. Because these applications expose them to strong electromagnetic interference, radiation, shock, and high temperatures, they must meet specific requirements for resistance to strong shock, radiation, and extreme temperatures.

[0003] Currently, the most commonly used accelerometers are compression sensors, which consist of a base, a piezoelectric element, and a mass. The piezoelectric element is placed on the base, and the mass is connected to the base, pressing the piezoelectric element against the base surface. With this structure, when the accelerometer moves as a whole, the mass applies pressure to the piezoelectric element, allowing the piezoelectric element to detect the pressure applied by the mass and then calculate the acceleration based on the pressure. However, because the piezoelectric element in this accelerometer is directly attached to the surface of the base, the contact area between the two is large. This results in significant strain interference from the base when the sensor is operating, which in turn affects the detection accuracy of the accelerometer. Summary of the Invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a bending-shear coupling acceleration sensor and a forming method thereof. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0005] In a first aspect, the present invention provides a bending-shear coupling acceleration sensor, comprising an upper shell and a lower shell, wherein the upper shell is provided with an internal thread and a step, and the lower shell is provided with an external thread, the upper shell and the lower shell are threadedly connected and together form an accommodating cavity, wherein a metal piezoelectric composite sensitive element, a first mass block, a screw, and a second mass block are provided in the accommodating cavity, the metal piezoelectric composite sensitive element comprising a piezoelectric sheet group, a pinless electrode sheet group, and a second electrode sheet with a pin, the piezoelectric sheet group comprising a first piezoelectric sheet and a second piezoelectric sheet with opposite polarization directions, the electrode sheet group comprising a first electrode sheet and a third electrode sheet, the first electrode sheet, the first piezoelectric sheet, the second electrode sheet, the second piezoelectric sheet, and the third electrode sheet being coaxially arranged and bonded in sequence;

[0006] The edge of the metal piezoelectric composite sensitive element is pressed tightly between the upper shell and the lower shell. A first through-hole is provided at the center of the piezoelectric sheet group. A second through-hole is provided at the center of each of the electrode sheet group and the second electrode sheet. The screw is coaxially inserted into the first through-hole and the second through-hole.

[0007] The first mass block and the second mass block are respectively engaged with threads at both ends of the screw rod, the metal piezoelectric composite sensitive element is pressed tightly between the first mass block and the second mass block, and there is a distance between the first mass block and the second mass block and the inner wall of the accommodating cavity;

[0008] The upper shell has a threaded through-hole on its side, and a connector is provided within the threaded through-hole. The connector and the threaded through-hole are matingly connected. The first electrode sheet is in direct contact with the upper shell, and the third electrode sheet is in direct contact with the lower shell. The shell is made of metal or ceramic with a metal coating. The first and third electrode sheets are electrically connected through the shell. The second electrode sheet has a pin, which is connected to a wire. The connector has a center hole, and the wire is led out from the center hole of the connector. In summary, the electrical signal of the sensor is led out one way from the wire and another way from the shell and connector shell.

[0009] In one embodiment of the present invention, the first piezoelectric sheet and the second piezoelectric sheet are radially polarized piezoelectric ceramics with opposite polarization directions, and the piezoelectric ceramics include lead zirconate titanate ceramics, bismuth layered structure ceramics, potassium sodium niobate, and bismuth scandate-lead titanate.

[0010] In one embodiment of the present invention, a first conductive adhesive layer is provided between the first electrode sheet and the first piezoelectric sheet, a second conductive adhesive layer is provided between the second electrode sheet and the first piezoelectric sheet, a third conductive adhesive layer is provided between the second electrode sheet and the second piezoelectric sheet, and a fourth conductive adhesive layer is provided between the third electrode sheet and the second piezoelectric sheet.

[0011] In one embodiment of the present invention, the first mass block and the second mass block are both double-layered annular blocks.

[0012] In one embodiment of the present invention, a first annular protrusion is provided on a side of the first mass block facing the piezoelectric sheet group, and a cross-sectional area of ​​the first annular protrusion is smaller than a cross-sectional area of ​​the thick annular portion of the first mass block.

[0013] In one embodiment of the present invention, a second annular protrusion is provided on a side of the second mass block facing the piezoelectric sheet group, and a cross-sectional area of ​​the second annular protrusion is smaller than a cross-sectional area of ​​the thick annular portion of the second mass block.

[0014] In one embodiment of the present invention, the upper shell includes a top plate and an upper annular enclosure plate, wherein the upper annular enclosure plate and the top plate are connected to form a first chamber.

[0015] The upper annular enclosure includes a first annular portion and a second annular portion arranged in sequence along the axial direction. The outer diameter of the first annular portion is equal to the outer diameter of the second annular portion, and the inner diameter of the first annular portion is smaller than the inner diameter of the second annular portion.

[0016] In one embodiment of the present invention, the lower shell includes a bottom plate and a lower annular enclosure plate, the lower annular enclosure plate and the bottom plate are connected and the two form a second chamber, and the first chamber and the second chamber form a receiving chamber;

[0017] The bottom plate is a circular plate, the lower annular plate and the circular plate are coaxially arranged, and the outer diameter of the lower annular plate is smaller than the diameter of the circular plate;

[0018] The second annular portion is sleeved on the outer circumference of the lower annular enclosure, and one end of the second annular portion abuts against the surface of the circular plate, and the edge of the piezoelectric sheet group is clamped between the end face of the first annular portion and the end face of the lower annular enclosure.

[0019] In a second aspect, the present invention provides a forming method of a bending-shear coupling acceleration sensor, which is applied to the bending-shear coupling acceleration sensor provided in the above scheme. The bending-shear coupling acceleration sensor includes an upper shell, a lower shell, a metal piezoelectric composite sensitive element, a first mass block, a screw, and a second mass block. The metal piezoelectric composite sensitive element includes a piezoelectric sheet group, an electrode sheet group, and a second electrode sheet. The piezoelectric sheet group includes a first piezoelectric sheet and a second piezoelectric sheet with opposite polarization directions. The electrode sheet group includes a first electrode sheet and a third electrode sheet. The method includes:

[0020] Step 1: Perform structural parameter simulation on the index parameters required by the bending-shear coupling accelerometer, and prepare each corresponding component according to the parameters obtained by the simulation design;

[0021] Step 2: Applying high voltage to fully radially polarize the prepared annular piezoelectric disc;

[0022] Step 3: Grind away the electrodes set for radial polarization, and then set electrodes on the upper and lower main surfaces of the piezoelectric disc;

[0023] Step 4: Assemble the metal piezoelectric composite sensitive element, the first mass block, the screw and the second mass block to obtain an assembly;

[0024] Step 5: Connect the electrode leads, coaxially assemble the upper shell, lower shell and the obtained assembly, and connect the connectors.

[0025] In one embodiment of the present invention, step one specifically includes:

[0026] Using COMSOL Multiphysics software developed by the Swedish COMSOL Group for simulation, we designed and simulated the sensor's target sensitivity, frequency response, and lateral sensitivity, repeatedly adjusting the structural parameters until the design requirements were met.

[0027] Step 2 specifically includes:

[0028] Conductive silver glue was applied to the inner and outer annular surfaces of the first and second piezoelectric sheets, and wires were attached. The sheets were then placed in an oven for curing at a temperature of 100° C. for 30 minutes.

[0029] Place the first piezoelectric plate and the second piezoelectric plate in silicone oil, connect a current source to both ends of the wire, and heat the silicone oil to 120°C;

[0030] Start polarizing the first and second piezoelectric sheets by slowly increasing the constant current source voltage to 3 kV, waiting for 2-8 minutes, and then increasing the voltage by 0.5 kV every two minutes until it reaches 8 kV. Then wait for half an hour for polarization to be completed, thereby obtaining the first and second piezoelectric sheets with opposite polarization directions;

[0031] Step three specifically includes:

[0032] removing electrodes on the inner and outer annular surfaces of the first and second piezoelectric sheets;

[0033] The first piezoelectric sheet and the second piezoelectric sheet are polished to a specified thickness using sandpaper of different specifications. During the polishing process, the thickness of the first piezoelectric sheet and the second piezoelectric sheet is continuously measured using a thickness gauge to ensure that the overall thickness deviation of the first piezoelectric sheet and the second piezoelectric sheet does not exceed 3 microns.

[0034] Grind the electrode sheet to make its surface smooth and burr-free;

[0035] Step 4 specifically includes:

[0036] Spin-coating a conductive adhesive on the surfaces of the first piezoelectric sheet and the second piezoelectric sheet, attaching the electrode sheet to the surface of the first piezoelectric sheet or the second piezoelectric sheet, and continuously squeezing and adjusting the positions of the first piezoelectric sheet and the second piezoelectric sheet to thin the conductive adhesive layer and evenly distribute the conductive adhesive layer;

[0037] The first piezoelectric sheet and the second piezoelectric sheet were placed in a fixture and placed in an oven for curing at a temperature of 100° C. for 30 minutes.

[0038] Between Steps 4 and 5 also include:

[0039] Pass multiple strands of copper wire through the holes reserved on the electrode sheet. Then fold the wires in half and twist them into a twist. Use conductive glue to reinforce the joints. Place them in an oven to cure at 100°C for 30 minutes. Apply insulating glue around the wires to prevent them from coming into direct contact with the joints.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] In the above scheme of the present application, it includes an upper shell and a lower shell, the upper shell is provided with an internal thread and a step, the lower shell is provided with an external thread, the upper shell and the lower shell are threadedly connected and together form an accommodating cavity, the accommodating cavity is provided with a metal piezoelectric composite sensitive element, a first mass block, a screw and a second mass block, the metal piezoelectric composite sensitive element includes a piezoelectric sheet group, a pinless electrode sheet group and a second electrode sheet with a pin, the piezoelectric sheet group includes a first piezoelectric sheet and a second piezoelectric sheet with opposite polarization directions, the electrode sheet group includes a first electrode sheet and a third electrode sheet, the first electrode sheet, the first piezoelectric sheet, the second electrode sheet, the second piezoelectric sheet and the third electrode sheet are coaxially arranged and bonded in sequence; the edge of the metal piezoelectric composite sensitive element is pressed tightly between the upper shell and the lower shell, the center of the piezoelectric sheet group is provided with a first through hole, the electrode sheet group A second through-hole is provided at the center of the first and second electrode sheets, and the screw is coaxially inserted into the first through-hole and the second through-hole; the first mass block and the second mass block are respectively matched with the threads at both ends of the screw, and the metal piezoelectric composite sensitive element is pressed between the first mass block and the second mass block, and there is a distance between the first mass block and the second mass block and the inner wall of the accommodating cavity; a threaded through-hole is provided on the side of the upper shell, and a joint is provided in the threaded through-hole, and the joint and the threaded through-hole are matched and connected, the first electrode sheet is in direct contact with the upper shell, and the third electrode sheet is in direct contact with the lower shell, and the shell is made of metal material or ceramic material with metal plating, and the first electrode sheet and the third electrode sheet are electrically conductive through the shell; a pin is provided on the second electrode sheet, and a wire is connected to the pin, and a center hole is provided on the joint, and the wire is led out from the center hole of the joint. With this structure, when the acceleration sensor moves as a whole, the first mass block, the second mass block and the screw can exert downward or upward pressure on the center of the piezoelectric sheet group 3, so that the piezoelectric sheet group 3 as a whole can undergo downward or upward bending-shear coupling deformation, thereby generating an electrical signal and transmitting it to the electrode sheet. The electrode sheet transmits the electrical signal to an external signal receiver, and the acceleration of the target object can be calculated by detecting the electrical signal. The above-mentioned structure of the present application presses the edge of the piezoelectric sheet group through the upper shell and the lower shell, and applies pressure to the center of the piezoelectric sheet group through the first mass block and the second mass block, so that the acceleration sensor can detect the acceleration of the target object using the shear-bending coupling effect. Since the contact area between the piezoelectric sheet group and the upper shell and the lower shell is small, the strain interference of the upper shell and the lower shell on the piezoelectric sheet group is small, thereby improving the detection accuracy of the acceleration sensor.

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a cross-sectional view of an acceleration sensor according to an embodiment of the present invention;

[0044] Figure 2 is an exploded schematic diagram of an acceleration sensor in an embodiment of the present invention;

[0045] Figure 3 is a schematic diagram of an upper housing according to an embodiment of the present invention;

[0046] Figure 4 is a cross-sectional view of the upper housing in an embodiment of the present invention;

[0047] Figure 5 is a schematic diagram of the lower housing in an embodiment of the present invention;

[0048] Figure 6 is a cross-sectional view of the lower housing in an embodiment of the present invention;

[0049] Figure 7 is a schematic diagram of a first mass block in an embodiment of the present invention;

[0050] Figure 8 is a schematic diagram of a first piezoelectric sheet in an embodiment of the present invention;

[0051] Figure 9 Schematic diagram of a screw rod according to an embodiment of the present invention;

[0052] Figure 10 is a schematic diagram of a second electrode sheet in an embodiment of the present invention;

[0053] Figure 11 Schematic diagram of the first six resonant modes during simulation of the acceleration sensor according to an embodiment of the present invention;

[0054] Figure 12 FIG. 4 is a frequency response curve diagram of the acceleration sensor during simulation in an embodiment of the present invention.

[0055] Figure markings: 1-upper shell, 11-top plate, 12-upper annular enclosure, 121-first annular portion, 122-second annular portion, 2-lower shell, 21-bottom plate, 22-lower annular enclosure, 3-piezoelectric sheet group, 31-first piezoelectric sheet, 32-second piezoelectric sheet, 4-electrode sheet group, 41-first electrode sheet, 42-third electrode sheet, 5-second electrode sheet, 6-metal piezoelectric composite sensitive element, 7-first mass block, 8-screw, 9-second mass block, 10-connector. DETAILED DESCRIPTION

[0056] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0057] Example 1:

[0058] See Figures 1 to 10An embodiment of the present invention provides a bending-shear coupling accelerometer, comprising an upper housing 1 and a lower housing 2. The upper housing 1 is provided with internal threads and a step, while the lower housing 2 is provided with external threads. The upper housing 1 and the lower housing 2 are threadedly connected and together form a housing cavity, within which a metal piezoelectric composite sensing element 6, a first mass 7, a screw 8, and a second mass 9 are located. The piezoelectric sheet group 3 includes a first piezoelectric sheet 31 and a second piezoelectric sheet 32 ​​with opposite polarization directions. The electrode sheet group 4 includes a first electrode sheet 41 and a third electrode sheet 42. A first through-hole is defined at the center of the piezoelectric sheet group 3. The electrode sheet group 4 and the second electrode sheet 5 with a connecting sheet each have a second through-hole at their centers. The metal piezoelectric composite sensing element 6 is formed by coaxially bonding the piezoelectric sheet group 4 to the first electrode sheet 41, the second electrode sheet 5, and the third electrode sheet 42. A screw 8 is coaxially inserted through the first and second through-holes. The first mass 7 and the second mass 9, respectively, engage with the threads at both ends of the screw 8 to symmetrically press against the area near the central through-hole of the metal piezoelectric composite sensing element 6. The side of the upper shell 1 is provided with a threaded through hole that cooperates with the connector 10. The outer edge of the metal piezoelectric composite sensitive element 6 is pressed between the upper shell 1 and the lower shell 2. The first electrode sheet 41 is in direct contact with the upper shell 1, and the third electrode sheet 42 is in direct contact with the lower shell 2. The shell is made of metal or ceramic with a metal coating. The first electrode sheet and the third electrode sheet are electrically connected through the shell. The second electrode sheet 5 is provided with a pin, and the pin is connected to a wire. The connector 10 is provided with a center hole, and the wire is led out from the center hole of the connector 10. In summary, the electrical signal of the sensor is led out one way from the wire and the other way from the shell and the connector shell. It is required that the outer ring surface of the metal piezoelectric composite sensitive element 6 does not contact the metal shell to ensure the insulation of the sensor. In addition, there is a gap between the first mass block 7 and the second mass block 9 and the inner wall of the accommodating cavity, providing sufficient space for the movement of the mass blocks.

[0059] In some embodiments of the present application, the first piezoelectric plate 31 and the second piezoelectric plate 32 are radially polarized piezoelectric ceramics with opposite polarization directions. The piezoelectric materials used include lead zirconate titanate ceramics (Pb(Zr,Ti)O3), bismuth layered structure ceramics (such as Bi4Ti3O 12 (BIT), SrBi4Ti4O 15 (SBTi)), potassium sodium niobate ((K,Na)NbO3), bismuth scandate-lead titanate ((1-x)BiScO3-xPbTiO3), etc. When the material used is bismuth scandate-lead titanate ((1-x)BiScO3-xPbTiO3), it can be used for vibration and shock testing in a high temperature environment of 260°C.

[0060] In some embodiments of the present application, the electrode sheet is an annular sheet as a whole, and is divided into two forms: with a connecting sheet and without a connecting sheet. Figure 2 and Figure 10As shown, the first electrode sheet 41 and the third electrode sheet 42 have no connecting sheets, and the edge of the second electrode sheet 5 is provided with a pin connecting sheet extending along its radial direction, and the pins are provided with through holes for convenient wire connection.

[0061] In some embodiments of the present application, Figure 1 、 Figure 2 、 Figure 8 and Figure 10 As shown, the electrode sheet is attached to the surface of the piezoelectric sheet group 3, and the first through-hole of the piezoelectric sheet group 3 and the second through-hole of the electrode sheet are coaxially arranged. The metal piezoelectric composite sensor 6 is provided with three electrode sheets, namely the first electrode sheet 41, the second electrode sheet 5, and the third electrode sheet 42. The first electrode sheet 41 is arranged between the first mass block 7 and the first piezoelectric sheet 31, the second electrode sheet 5 is arranged between the first piezoelectric sheet 31 and the second piezoelectric sheet 32, and the third electrode sheet 42 is arranged between the second piezoelectric sheet 32 ​​and the second mass block 9.

[0062] In some embodiments of the present application, Figure 1 、 Figure 2 、 Figure 8 and Figure 10 As shown, a first conductive adhesive layer is provided between the first electrode sheet 4 and the first piezoelectric sheet 31, a second conductive adhesive layer is provided between the second electrode sheet 5 and the first piezoelectric sheet 31, a third conductive adhesive layer is provided between the second electrode sheet 5 and the second piezoelectric sheet 32, and a fourth conductive adhesive layer is provided between the third electrode sheet 42 and the second piezoelectric sheet 32. This improves the contact between the electrode sheets and the piezoelectric sheets, ensuring assembly reliability.

[0063] In some embodiments of the present application, the metal piezoelectric composite sensor 6 can be composed of one or more piezoelectric sheets. The number of electrodes used can be adjusted accordingly, depending on the specific application requirements. During assembly, it is necessary to ensure that adjacent piezoelectric sheets have opposite polarization directions. Using a structure with multiple piezoelectric sheets connected in parallel can increase the axial stiffness of the piezoelectric sheets, broaden the frequency response range, and improve the measurement accuracy of the sensor. However, this increases the difficulty of preparation and places higher demands on the reliability of the acceleration sensor.

[0064] In some embodiments of the present application, the first mass block 7 and the second mass block 9 are both double-layered annular blocks, both made of alumina ceramics or metals with a thermal expansion coefficient very close to that of the piezoelectric element, and the center of the structure is a threaded through hole. Figure 1 、 7As shown, the side of the mass block facing the piezoelectric sheets is equipped with an annular protrusion with a relatively small diameter. The other layer of the mass block, facing away from the piezoelectric sheets, is a thick, larger-diameter ring. The first mass block 7 is equipped with a first annular protrusion on the side facing the piezoelectric sheet assembly 3, and the second mass block 9 is equipped with a second annular protrusion on the side facing the piezoelectric sheet assembly 3. This structure not only compresses the piezoelectric sheet assembly 3 with the first and second annular protrusions, but also reduces the contact area between the first and second mass blocks 7 and 9 and the electrode sheet, thereby increasing the effective length of the bent and deformed portion of the piezoelectric sheet assembly 3 and improving the sensitivity and accuracy of the measurement of the piezoelectric sheet assembly 3.

[0065] In some of the claimed embodiments, screw 8 has a "dumbbell" structure with external threads at both ends. It is coaxially mounted within the central through-hole of metal piezoelectric composite sensor 6. First mass 7 and second mass 9 engage the threads at either end of screw 8, symmetrically pressing against the two sides of the central through-hole of metal piezoelectric composite sensor 6. This symmetrical dual-mass structure ensures uniform force distribution between the two annular piezoelectric discs, improving structural reliability.

[0066] In some embodiments of the present application, Figure 3 、 Figure 4 、 Figure 7 and Figure 9 As shown, the upper shell 1 includes a top plate 11 and an upper annular enclosure plate 12. Figure 3 and 4 As shown, the sidewall of the upper housing 1 is provided with a threaded through-hole. The upper annular panel 12 and the top panel 11 are connected to form a first chamber. The upper annular panel 12 comprises a first annular portion 121 and a second annular portion 122, arranged axially. The outer diameters of the two portions are equal, while the inner diameter of the first annular portion 121 is smaller than that of the second annular portion 122. The protrusion of the inner ring of the first annular portion 121 relative to the second annular portion 122 forms a step for the subsequent assembly of the piezoelectric element. The inner wall of the second annular portion 122 is provided with assembly threads. The inner diameter of the components near the junction of the two annular portions is the largest, forming a storage space for the piezoelectric element.

[0067] In some embodiments of the present application, Figure 5 、 Figure 6 、 Figure 7 and Figure 9 As shown, the lower shell 2 includes a bottom plate 21 and a lower annular plate 22. Figure 5 and 6 As shown, the lower annular plate 22 and the bottom plate 21 are connected to form a second chamber; the bottom plate 21 is a circular plate, provided with a threaded mounting blind hole for device test installation, the lower annular plate 22 and the circular plate are coaxially arranged, and the outer diameter of the lower annular plate 22 is smaller than the diameter of the circular plate.

[0068] In some embodiments of the present application, the assembled metal piezoelectric composite sensitive element 6 is placed on the step of the upper shell 1, the wire is connected to the through hole of the connecting piece of the electrode sheet 5 and is led out from the central through hole of the connecting connector 11, and a gap exists between the inner wall of the shell 1 and the outer annular surface of the metal piezoelectric composite sensitive element 6.

[0069] In some embodiments of the present application, the piezoelectric sensitive element 3 is clamped between the upper shell 1 and the lower shell 2. The upper shell 1 and the lower shell 2 are connected by threads to clamp the piezoelectric sensitive element 3. The shell is required to be made of a metal or ceramic-metal composite material whose thermal expansion coefficient is very close to that of the piezoelectric sensitive element.

[0070] In some embodiments of the present application, Figure 1 and Figure 2 As shown, connector 10 connects to the threaded hole of upper housing 1 via threads on its outer wall. The wires leading from the electrode sheets can extend through connector 10. Insulating material is required around the wires to prevent them from direct contact with the connector housing. A gap is left between the end of the assembled connector 10 and the metal piezoelectric composite sensor 6 to ensure insulation of the device circuit.

[0071] In some embodiments of the present application, one end of the signal of the metal piezoelectric composite sensitive element 6 is led out from the pin of the electrode sheet 5 and through the central through hole of the connecting connector 11; the upper and lower end surfaces of the piezoelectric sensitive element 6 are in direct contact with the upper and lower shells 1 and 2, and the other end of the signal is led out from the outer shell of the connecting connector 10 through the upper and lower shells.

[0072] In some embodiments of the present application, the acceleration sensor is based on a radially polarized thin annular piezoelectric material. 15 The amount of charge generated in actual work is related to the polarization effect of the piezoelectric material and the overall stress conditions.

[0073] In the above scheme of the present application, the acceleration sensor includes an upper shell 1 and a lower shell 2, the upper shell 1 and the lower shell 2 are detachably connected and together form an accommodating cavity, in which a metal piezoelectric composite sensitive element 6, a first mass block 7, a screw 8 and a second mass block 9 are provided; the edge of the metal piezoelectric composite sensitive element 6 is pressed between the upper shell 1 and the lower shell 2, the electrode sheet is arranged on the piezoelectric sheet group 3 and is used to connect to an external signal receiver, the center of the piezoelectric sheet group 3 is provided with a first through-hole, the center of each electrode sheet is provided with a second through-hole, and the screw 8 is inserted into the first through-hole and the second through-hole; the first mass block 7 and the second mass block 9 are arranged on both sides of the piezoelectric sheet group 3 and are respectively connected to the two ends of the screw 8, the metal piezoelectric composite sensitive element 6 is pressed between the first mass block 7 and the second mass block 9, and there is a distance between the first mass block 7 and the second mass block 9 and the inner wall of the accommodating cavity. With this structure, when the acceleration sensor moves as a whole, the first mass block, the second mass block and the screw can exert downward or upward pressure on the center of the piezoelectric sheet group 3, so that the piezoelectric sheet group 3 as a whole can undergo upward or downward bending-shear coupling deformation, thereby generating an electrical signal and transmitting it to the electrode sheet, which transmits the electrical signal to the external signal receiver through the electrode sheet. The acceleration of the target object can be calculated by testing the electrical signal. Since the contact area between the above-mentioned metal piezoelectric composite sensitive element 6 and the upper shell 1 and the lower shell 2 is small, the strain interference of the upper shell 1 and the lower shell 2 on the piezoelectric sheet group 3 is small, thereby improving the detection accuracy of the acceleration sensor. And when the shear-bending coupling effect is used to detect the acceleration of the target object, the piezoelectric sheet group 3 can obtain a larger deformation under the condition that the mass of the first mass block 7 and the second mass block 9 is small, and a larger charge signal can be obtained while ensuring the lightweight design of the acceleration sensor.

[0074] Example 2:

[0075] An embodiment of the present invention provides a forming method for a bending-shear coupling acceleration sensor, which is applied to the bending-shear coupling acceleration sensor provided in the first embodiment above. The bending-shear coupling acceleration sensor includes an upper shell, a lower shell, a metal piezoelectric composite sensitive element, a first mass block, a screw, and a second mass block. The method includes:

[0076] Step 1: Perform structural parameter simulation on the index parameters required by the bending-shear coupling piezoelectric accelerometer; prepare each corresponding component according to the parameters obtained from the simulation design.

[0077] Step 2: Fully radially polarize the prepared annular piezoelectric disc using a high-voltage DC polarization power supply;

[0078] Step 3: Grind away the electrodes set for radial polarization, and then bond the electrode sheets to the upper and lower end surfaces of the piezoelectric disc.

[0079] Step 4: Assemble the metal piezoelectric composite sensitive element, the first mass block, the screw and the second mass block to obtain an assembly;

[0080] Step 5: Connect the electrode leads, coaxially assemble the upper shell, lower shell and the obtained assembly, and connect the connectors.

[0081] The beneficial effects of the second embodiment of the present invention and its various implementations can be analyzed with reference to the beneficial effects of the first embodiment and its various implementations, and will not be repeated here.

[0082] In some embodiments of the present application, the piezoelectric sheet group includes a first piezoelectric sheet and a second piezoelectric sheet, and the first piezoelectric sheet and the second piezoelectric sheet are both annular sheets;

[0083] In some embodiments of the present application, step one specifically includes:

[0084] First, simulations were performed using COMSOL Multiphysics, developed by the Swedish COMSOL Group. Material parameters (including but not limited to density, Young's modulus, Poisson's ratio, and piezoelectric coefficient) were sourced from relevant literature. Parameter design and simulation calculations were performed based on the sensor's target sensitivity, frequency response, and lateral sensitivity. Structural parameters were repeatedly adjusted until the design requirements were met. Figure 11 The figure shows the schematic diagram of the first six resonance modes during the acceleration sensor simulation. Figure 12 The frequency response curve of the acceleration sensor simulation is shown in Figure 2. Figure 11 and Figure 12 As can be seen, the first two orders are lateral bending modes, and the third order is the main resonant mode. The frequency response curve for the three axes ranges from 50Hz to 40kHz, with the X-axis being the sensitive axis. The first two orders correspond to lateral resonances, which strongly interfere with the X-axis signal at these resonant frequencies. With a 10% deviation, the upper limit of the usable frequency range is 6.5kHz. Within this frequency range, lateral crosstalk is very weak, allowing the accelerometer to maintain stable output.

[0085] Step 2 specifically includes:

[0086] Conductive silver glue was applied to the inner and outer annular surfaces of the first and second piezoelectric sheets, and wires were attached. The sheets were then placed in an oven for curing at a temperature of 100° C. for 30 minutes.

[0087] The piezoelectric sheet was placed in a silicone oil bathtub, and a pair of positive and negative electrode rods connected to a voltage source were respectively introduced to the outer annular electrode and the inner annular electrode of the piezoelectric sheet. The silicone oil bathtub was heated to 120°C by an electric heater. Then, the voltage of the high-voltage DC polarization power supply was slowly increased to 3kV, and the voltage was increased by 0.5kV every two minutes until the voltage rose to 8kV. The piezoelectric sheet was polarized with high voltage for half an hour to complete the forward polarization of the first piezoelectric sheet.

[0088] In this embodiment, 0.365BS-0.635PT high-temperature ceramic is used as the piezoelectric element. When the second piezoelectric sheet and the first piezoelectric sheet are polarized, the polarization voltage and polarization time are kept the same, but the connection relationship between the positive and negative poles of the voltage source and the inner and outer annular electrodes of the piezoelectric sheet is opposite, thereby obtaining the first and second piezoelectric sheets with opposite polarization directions.

[0089] Step three specifically includes:

[0090] removing electrodes on the inner and outer annular surfaces of the first and second piezoelectric sheets;

[0091] The first piezoelectric sheet and the second piezoelectric sheet are polished to a specified thickness using sandpaper of different specifications. During the polishing process, the thickness of the first piezoelectric sheet and the second piezoelectric sheet is continuously measured using a thickness gauge to ensure that the overall thickness deviation of the first piezoelectric sheet and the second piezoelectric sheet does not exceed 3 microns.

[0092] Grind the electrode sheet to make its surface smooth and burr-free;

[0093] Step 4 specifically includes:

[0094] Spin-coating high-temperature conductive adhesive on the upper and lower end surfaces of the first piezoelectric sheet and the second piezoelectric sheet, attaching the electrode sheet to the end surface of the first piezoelectric sheet or the second piezoelectric sheet, and continuously squeezing and adjusting the positions of the first piezoelectric sheet and the second piezoelectric sheet to thin the conductive adhesive layer and evenly distribute it;

[0095] Place the assembled piezoelectric sheet and electrode sheet assembly in a fixture and place in an oven for curing. The curing temperature and time should be determined based on the desired curing temperature and time parameters for the conductive silver adhesive used. Typically, the curing temperature is set at 100°C and the curing time is 30 minutes. After curing, sand off any excess conductive adhesive.

[0096] Between Steps 4 and 5 also include:

[0097] Pass multiple strands of copper wire through the holes reserved on the electrode sheet. Then fold the wires in half and twist them into a twist. Use conductive glue to reinforce the joints. Place them in an oven to cure at 100°C for 30 minutes. Apply insulating glue around the wires to prevent them from coming into direct contact with the joints.

[0098] In some embodiments of the present application, step five specifically includes:

[0099] Clean the surface of each part, insert the screw into the first through-hole and the second through-hole, screw the first mass block and the second mass block onto the screw, place the piezoelectric sheet group on the lower shell, adjust the position to ensure the concentricity of the two, and screw into the upper shell so that the edge of the piezoelectric sheet group is pressed tightly.

[0100] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0101] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0102] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0103] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A bending-shear coupling acceleration sensor, characterized in that: The invention comprises an upper shell and a lower shell, wherein the upper shell is provided with an internal thread and a step, and the lower shell is provided with an external thread. The upper shell and the lower shell are threadedly connected and together form an accommodating cavity. A metal piezoelectric composite sensitive element, a first mass block, a screw and a second mass block are provided in the accommodating cavity. The metal piezoelectric composite sensitive element comprises a piezoelectric sheet group, a pinless electrode sheet group and a second electrode sheet with a pin. The piezoelectric sheet group comprises a first piezoelectric sheet and a second piezoelectric sheet with opposite polarization directions. The electrode sheet group comprises a first electrode sheet and a third electrode sheet. The first electrode sheet, the first piezoelectric sheet, the second electrode sheet, the second piezoelectric sheet and the third electrode sheet are coaxially arranged and bonded in sequence. The edge of the metal piezoelectric composite sensitive element is pressed tightly between the upper shell and the lower shell, a first through-hole is provided at the center of the piezoelectric sheet group, a second through-hole is provided at the center of each of the electrode sheet group and the second electrode sheet, and a screw is coaxially inserted into the first through-hole and the second through-hole; The first mass block and the second mass block are respectively threadedly engaged with the two ends of the screw rod, the metal piezoelectric composite sensitive element is compressed between the first mass block and the second mass block, and there is a distance between the first mass block and the second mass block and the inner wall of the accommodating cavity; A threaded through hole is provided on the side of the upper shell, and a joint is provided in the threaded through hole. The joint and the threaded through hole are cooperatively connected. The first electrode sheet is in direct contact with the upper shell, and the third electrode sheet is in direct contact with the lower shell. The shell is made of metal or ceramic with metal plating. The first electrode sheet and the third electrode sheet are electrically connected through the shell; the second electrode sheet is provided with a pin, and the pin is connected to a wire. The joint is provided with a center hole, and the wire is led out from the center hole of the joint. The outer periphery of the wire is coated with insulating material to isolate it from direct contact with the joint.

2. The bending-shear coupling acceleration sensor according to claim 1, characterized in that: The first piezoelectric sheet and the second piezoelectric sheet are radially polarized piezoelectric ceramics with opposite polarization directions, and the piezoelectric ceramics include lead zirconate titanate ceramics, bismuth layered structure ceramics, potassium sodium niobate, and bismuth scandate-lead titanate.

3. The bending-shear coupling acceleration sensor according to claim 1, characterized in that: A first conductive adhesive layer is provided between the first electrode sheet and the first piezoelectric sheet, a second conductive adhesive layer is provided between the second electrode sheet and the first piezoelectric sheet, a third conductive adhesive layer is provided between the second electrode sheet and the second piezoelectric sheet, and a fourth conductive adhesive layer is provided between the third electrode sheet and the second piezoelectric sheet.

4. The bending-shear coupling acceleration sensor according to claim 1, characterized in that: The first mass block and the second mass block are both double-layer annular blocks.

5. The bending-shear coupling acceleration sensor according to claim 1 or 4, characterized in that: A first annular protrusion is provided on a side of the first mass block facing the piezoelectric sheet group, and a cross-sectional area of ​​the first annular protrusion is smaller than a cross-sectional area of ​​the thick annular portion of the first mass block.

6. The bending-shear coupling acceleration sensor according to claim 5, characterized in that: A second annular protrusion is provided on a side of the second mass block facing the piezoelectric sheet group, and a cross-sectional area of ​​the second annular protrusion is smaller than a cross-sectional area of ​​the thick annular portion of the second mass block.

7. The bending-shear coupling acceleration sensor according to claim 5, characterized in that: The upper shell includes a top plate and an upper annular enclosure plate, wherein the upper annular enclosure plate and the top plate are connected to form a first chamber; The upper annular enclosure includes a first annular portion and a second annular portion sequentially arranged along the axial direction. The outer diameter of the first annular portion is equal to the outer diameter of the second annular portion, and the inner diameter of the first annular portion is smaller than the inner diameter of the second annular portion.

8. The bending-shear coupling acceleration sensor according to claim 7, characterized in that: The lower shell includes a bottom plate and a lower annular enclosure plate, the lower annular enclosure plate and the bottom plate are connected to form a second chamber, and the first chamber and the second chamber constitute the accommodating chamber; The bottom plate is a circular plate, the lower annular plate and the circular plate are coaxially arranged, and the outer diameter of the lower annular plate is smaller than the diameter of the circular plate; The second annular portion is sleeved on the outer circumference of the lower annular enclosure, and one end of the second annular portion abuts against the surface of the circular plate, and the edge of the piezoelectric sheet group is clamped between the end face of the first annular portion of the upper annular enclosure and the end face of the lower annular enclosure.

9. A forming method of a bending-shear coupling acceleration sensor, characterized in that: The bending-shear coupling acceleration sensor according to any one of claims 1 to 8 comprises an upper shell, a lower shell, a metal piezoelectric composite sensing element, a first mass block, a screw, and a second mass block, the metal piezoelectric composite sensing element comprises a piezoelectric sheet group, an electrode sheet group, and a second electrode sheet, the piezoelectric sheet group comprises a first piezoelectric sheet and a second piezoelectric sheet having opposite polarization directions, the electrode sheet group comprises a first electrode sheet and a third electrode sheet, and the method comprises: Step 1: Perform structural parameter simulation on the index parameters required by the bending-shear coupling acceleration sensor, and prepare each corresponding component according to the parameters obtained by the simulation design; Step 2: Fully radially polarize the prepared annular piezoelectric disc using a high-voltage DC polarization power supply; Step 3: Grind away the electrodes set for radial polarization, and then bond the electrode sheets to the upper and lower main surfaces of the piezoelectric disc; Step 4: Assembling the metal piezoelectric composite sensitive element, the first mass block, the screw and the second mass block to obtain an assembly; Step 5: Connect the electrode leads, coaxially assemble the upper shell, lower shell and assembly, and connect the connectors.

10. The forming method of the bending-shear coupling acceleration sensor according to claim 9, characterized in that: The step 1 specifically includes: Using COMSOL Multiphysics software developed by the Swedish COMSOL Group for simulation, we designed and simulated the sensor's target sensitivity, frequency response, and lateral sensitivity, repeatedly adjusting the structural parameters until the design requirements were met. The second step specifically includes: Conductive silver glue is applied to the inner and outer annular surfaces of the first and second piezoelectric sheets, and wires are attached thereto. The sheets are then placed in an oven for curing at a temperature of 100° C. for 30 minutes. The first piezoelectric sheet and the second piezoelectric sheet are placed in silicone oil, a high-voltage polarized DC power supply is connected to both ends of the wire, and the silicone oil is heated to 120° C. Start polarizing the first piezoelectric sheet and the second piezoelectric sheet by slowly increasing the power supply voltage to 3 kV, waiting for 2-8 minutes, then increasing the voltage by 0.5 kV every two minutes until it reaches 8 kV, and then standing for half an hour to wait for the polarization to be completed. When polarizing the second piezoelectric sheet and the first piezoelectric sheet, the polarization voltage and polarization time are kept the same, but the connection relationship between the positive and negative poles of the voltage source and the inner and outer annular electrodes of the piezoelectric sheet is opposite, so as to obtain the first piezoelectric sheet and the second piezoelectric sheet with opposite polarization directions; The step three specifically includes: removing electrodes on the inner and outer annular surfaces of the first and second piezoelectric sheets; The first piezoelectric sheet and the second piezoelectric sheet are sequentially polished to a specified thickness using sandpaper of different specifications, and the thickness of the first piezoelectric sheet and the second piezoelectric sheet are continuously measured at multiple points on the first piezoelectric sheet and the second piezoelectric sheet using a thickness gauge during the polishing process, so that the thickness deviation between the first piezoelectric sheet and the second piezoelectric sheet does not exceed 3 microns; Grinding the electrode sheet to make its surface smooth and burr-free; The step 4 specifically includes: Spin-coating a conductive adhesive on the surfaces of the first piezoelectric sheet and the second piezoelectric sheet, attaching the electrode sheet to the surface of the first piezoelectric sheet or the second piezoelectric sheet, and continuously squeezing and adjusting the positions of the first piezoelectric sheet and the second piezoelectric sheet to thin the conductive adhesive layer and evenly distribute the conductive adhesive layer; The first piezoelectric sheet and the second piezoelectric sheet were placed in a fixture and placed in an oven for curing at a temperature of 100° C. for 30 minutes. The steps between step 4 and step 5 also include: Pass multiple strands of copper wire through the wire holes reserved on the electrode sheet, then fold the wires in half and twist them into a twist shape and reinforce the joints with conductive glue. Place them in an oven for curing at a temperature of 100°C for 30 minutes, and apply insulating glue around the wires to isolate them from direct contact with the joints.

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