Sandwich type piezoelectric stack driver

Abstract

The invention discloses a sandwich type piezoelectric stack driver, which belongs to the technical field of piezoelectric drivers, is used for high-precision and large-stroke displacement output, and comprises a piezoelectric stack formed by alternately stacking piezoelectric ceramic pieces and metal electrode pieces, a front metal cover plate, a rear metal cover plate, a connecting rod, a pre-tightening mechanism and an adapter. The piezoelectric ceramic pieces are connected in a mechanical series connection and circuit parallel connection mode, the polarization directions are alternately arranged, longitudinal vibration of the piezoelectric ceramic pieces is overlapped in the same direction, and the driving efficiency is remarkably improved. And the connecting rod penetrates through each layer of structure and applies adjustable pre-tightening force through the elastic pre-tightening structure, so that the ceramic chip is kept in a compressed state in a high-dynamic working state, and breakage is avoided. The structure does not need high-temperature sintering, modular assembly, maintenance and component replacement are facilitated, and the maintenance cost is low. Driving parameters can be flexibly adjusted according to the size of the piezoelectric plate, and the device has the advantages of being easy and convenient to manufacture, rapid in response, high in reliability, controllable in displacement and the like and is suitable for the fields of precision manufacturing, optical adjustment, medical instruments and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of piezoelectric actuators, and particularly relates to a sandwich-type piezoelectric stack actuator. Background Art

[0002] The working principle of a piezoelectric actuator is based on the inverse piezoelectric effect, that is, when a piezoelectric material is subjected to an external electric field, it will produce a small mechanical deformation; it is particularly suitable for positioning tasks with a precision requirement in the range of 1 nm and a stroke range of dozens of μm. Since the movement of the piezoelectric actuator does not rely on friction, the resolution is almost unlimited, the precision is high, the response is fast, and the structure is compact. Therefore, it is widely used in the fields of precision manufacturing, integrated circuits, optical systems, medical equipment, etc.

[0003] A piezoelectric stack is one of the most commonly used piezoelectric actuators. It is co-fired by up to hundreds of layers of piezoelectric ceramic sheets and internal metal electrodes. The maximum driving force that a piezoelectric stack can generate is proportional to its cross-sectional area (about 35 MPa), the maximum displacement is proportional to its length (about 0.15%), and the driving voltage is proportional to the thickness of the internal single-layer piezoelectric ceramic sheet (about 1 - 2 kV / mm). This enables the piezoelectric stack to generate a driving force of up to several thousand Newtons and a displacement of the order of ten micrometers at a relatively low driving voltage (100 - 200 V) with a relatively small size (cross-sectional area of about 100 mm 2 or so and a length of about 10 mm), and at the same time has a fast response ability.

[0004] However, due to its laminated structure, the piezoelectric stack cannot withstand tensile and lateral shear forces, and an additional pre-tightening force needs to be provided when used in high-dynamic situations. In addition, the manufacturing of the piezoelectric stack requires a complex sintering process and has a high cost; it is extremely easy to heat up under high-power conditions, resulting in a decrease in energy conversion efficiency and even depolarization of the piezoelectric material; it is easily damaged by electric breakdown, depolarization, mechanical damage, etc., and is almost irreparable after damage. Summary of the Invention

[0005] Aiming at the problems existing in the existing piezoelectric stack actuators, such as the need to provide an additional pre-tightening force during dynamic use, complex sintering process, high cost, easy heating, non-detachable, and difficult to maintain, the present invention provides a sandwich-type piezoelectric stack actuator.

[0006] To solve the above technical problems, a technical solution adopted by the present invention is:

[0007] A sandwich-type piezoelectric stack actuator, comprising a piezoelectric stack, a pre-tightening mechanism, and an adapter;

[0008] The pre-tightening mechanism includes a rear metal cover plate, a connecting rod vertically arranged on the top surface of the rear metal cover plate, a front metal cover plate sleeved on the outer side of the top of the connecting rod, and a pre-tightening nut threadedly connected to the top end of the connecting rod and located above the front metal cover plate. An elastic pre-tightening structure is arranged on the connecting rod, and the elastic pre-tightening structure applies a pre-tightening force to the top of the front metal cover plate;

[0009] The piezoelectric stack is sleeved on the outer side of the connecting rod and is clamped and pre-tightened at both ends by the rear metal cover plate and the front metal cover plate. It is composed of a plurality of piezoelectric ceramic sheets and metal electrode sheets alternately stacked. The polarization directions of adjacent two piezoelectric ceramic sheets are opposite, and the electric properties of adjacent two metal electrode sheets are opposite;

[0010] The adapter is arranged on the top of the front metal cover plate and moves synchronously with the front metal cover plate.

[0011] Further, the height of the piezoelectric stack is 10 - 120 mm, the outer diameter is 8 - 70 mm, and the inner diameter is 3 - 30 mm.

[0012] Further, the piezoelectric ceramic sheets are circular piezoelectric ceramic sheets.

[0013] Further, a wiring terminal is arranged on one side of the metal electrode sheet, and the wiring terminals on adjacent two metal electrode sheets are respectively located on both sides of the connecting rod.

[0014] Further, the elastic pre-tightening structure includes a disc spring and a disc spring gasket respectively sleeved on the outer side of the top of the connecting rod. The disc spring is located on the top of the front metal cover plate, and the disc spring gasket is located above the disc spring and below the pre-tightening nut.

[0015] Further, the number of the disc springs is multiple, and they are stacked and arranged in sequence along the length direction of the connecting rod.

[0016] Further, the connection between the adapter and the front metal cover plate is detachable, and the connection between the rear metal cover plate and the connecting rod is detachable.

[0017] Further, the adapter is threadedly connected to the top of the front metal cover plate, and the maximum distance between the top end of the connecting rod and the bottom wall of the top end of the adapter is not less than the total longitudinal vibration displacement range of the piezoelectric stack.

[0018] Further, the elastic pre-tightening structure is a grooved flexible hinge or a straight beam-shaped cut hinge arranged on the cylindrical surface of the connecting rod and uniformly distributed along the axial direction of the connecting rod.

[0019] Further, the rear metal cover plate, the connecting rod and the adapter are of an integral structure, and the top end of the adapter is located above the top surface of the pre-tightening nut.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] (1) The sandwich - type piezoelectric stack actuator of the present invention uses a pre - tightening mechanism to clamp multiple layers of stacked and alternately arranged piezoelectric ceramic sheets and metal electrode sheets, without the need for a high - temperature sintering process, and has a low manufacturing cost.

[0022] (2) The sandwich - type piezoelectric stack actuator of the present invention can use a variety of pre - tightening mechanisms to provide a pre - tightening force for the piezoelectric ceramic sheets and metal electrode sheets, so that the piezoelectric ceramic sheets are always in a compressed state even during strong vibrations, thus avoiding the rupture of the piezoelectric ceramic sheets; moreover, the pre - tightening force and the stiffness of the pre - tightening mechanism can be adjusted conveniently, which can adapt to different dynamic usage scenarios.

[0023] (3) In the sandwich - type piezoelectric stack actuator of the present invention, due to the use of front and rear metal cover plates, the heat conduction performance of the actuator will be greatly improved. As long as the thickness and lateral dimensions of the metal material and the piezoelectric ceramic material are selected appropriately, the temperature coefficient of the piezoelectric ceramic material can be compensated by the elastic coefficient of the metal material. Therefore, the frequency - temperature coefficient of the sandwich - type piezoelectric stack actuator can be made very small, and its temperature stability is also better.

[0024] (4) The present invention adopts a modular structural design. Parameters such as the driving voltage, output force, and output displacement of the actuator can be controlled by the thickness, cross - sectional area, and total height of the piezoelectric ceramic sheets, and different models of piezoelectric stacks can be designed conveniently; the detachable structure allows damaged piezoelectric ceramic sheets to be replaced separately, thereby reducing the maintenance and usage costs. Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the overall structure of the sandwich - type piezoelectric stack actuator in Embodiment 1 of the present invention.

[0026] Figure 2 It is an exploded assembly schematic diagram of the sandwich - type piezoelectric stack actuator in Embodiment 1 of the present invention.

[0027] Figure 3 It is a schematic cross - sectional view of the sandwich - type piezoelectric stack actuator in Embodiment 1 of the present invention.

[0028] Figure 4 It is a schematic diagram of the deformation when the piezoelectric stack actuator elongates and the disc spring compresses when the excitation voltage of the power supply rises in Embodiment 1.

[0029] Figure 5 It is a schematic diagram of the deformation when the piezoelectric stack actuator contracts and the disc spring returns to its initial state when the excitation voltage of the power supply drops in Embodiment 1.

[0030] Figure 6 It is a schematic diagram of four structural forms of the adapter corresponding to the end of the sandwich - type piezoelectric actuator in Embodiment 1.

[0031] Figure 7 It is a schematic diagram of the overall structure of the sandwich piezoelectric stack actuator in Embodiment 2 and Embodiment 3.

[0032] Figure 8 It is a schematic diagram of the structure of the connecting rod described in Embodiment 2.

[0033] Figure 9 It is a schematic cross-sectional view of the sandwich piezoelectric stack actuator in Embodiment 2.

[0034] Figure 10 It is a schematic diagram of the structure of the connecting rod described in Embodiment 3.

[0035] Figure 11 It is a schematic cross-sectional view of the sandwich piezoelectric stack actuator in Embodiment 3.

[0036] In the figure: 1, piezoelectric stack; 2, pre-tightening mechanism; 3, adapter; 4, rear metal cover plate; 5, connecting rod; 6, metal electrode plate; 7, piezoelectric ceramic plate; 8, front metal cover plate; 9, disc spring; 10, disc spring gasket; 11, pre-tightening nut. Specific embodiments

[0037] The following elaborates on the preferred embodiments of the present invention in conjunction with the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making the protection scope of the present invention more clearly defined.

[0038] It should be noted that when a component is referred to as "mounted on" another component, it can be directly on the other component or there may also be an intermediate component. When a component is considered to be "disposed on" another component, it can be directly disposed on the other component or there may be an intermediate component at the same time. When a component is considered to be "fixed to" another component, it can be directly fixed to the other component or there may be an intermediate component at the same time.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "or / and" used herein includes any and all combinations of one or more of the related listed items.

[0040] Embodiment 1:

[0041] Please refer to Figures 1 to 3, A sandwich piezoelectric stack actuator, comprising a piezoelectric stack 1, a pre-tightening mechanism 2 and an adapter 3. The pre-tightening mechanism 2 includes a rear metal cover plate 4, a connecting rod 5 vertically arranged on the top surface of the rear metal cover plate 4, a front metal cover plate 8 sleeved on the outer side of the top of the connecting rod 5, and a pre-tightening nut 11 threadedly connected to the top end of the connecting rod 5 and located above the front metal cover plate 8. An elastic pre-tightening structure is arranged on the connecting rod 5, and the elastic pre-tightening structure applies a pre-tightening force to the top of the front metal cover plate 8.

[0042] Specifically, the rear metal cover plate 4 serves as the base of the piezoelectric stack 1 for providing fixed support. In this embodiment, it is set as a cylindrical structure and made of heavy-density metal materials such as stainless steel and copper to minimize the loss of the actuator output displacement at the rear metal cover plate 4 and improve the unidirectional output power of the actuator. A threaded hole is opened at the center of the top surface of the rear metal cover plate 4, and the bottom end of the connecting rod 5 is provided with an external threaded section matching the threaded hole, so that the connecting rod 5 is threadedly connected to the rear metal cover plate 4 and is perpendicular to the top surface of the rear metal cover plate 4, realizing a detachable connection. The front metal cover plate 8 is a cylindrical structure with a diameter substantially the same as that of the rear metal cover plate 4 and is made of low-density metal materials such as aluminum alloy, aluminum-magnesium alloy and titanium alloy to minimize the load at the displacement output end of the actuator. A through hole is opened at the center of the front metal cover plate 8, and the radius of the through hole is larger than the outer diameter of the connecting rod 5, so that the front metal cover plate 8 can be sleeved on the connecting rod 5. The space between it and the rear metal cover plate 4 is used to accommodate the piezoelectric stack 1, and the piezoelectric stack 1 is clamped and pre-tightened by the pre-tightening mechanism 2.

[0043] In this embodiment, the elastic pre-tightening structure includes a disc spring 9 and a disc spring gasket 10 respectively sleeved on the outer side of the top of the connecting rod 5. The disc spring 9 is located on the top of the front metal cover plate 8, and the disc spring gasket 10 is located above the disc spring 9 and below the pre-tightening nut 11. Through the threaded fit between the pre-tightening nut 11 and the connecting rod 5, the disc spring 9 is deformed, and the pre-tightening force is transmitted through the front metal cover plate 8, so as to apply a constant pre-tightening force to the piezoelectric stack 1 to ensure that the piezoelectric stack 1 is always in a compressed state when the actuator vibrates. The magnitude of the pre-tightening force can be changed by adjusting the axial position of the pre-tightening nut 11 on the connecting rod 5 to correspondingly change the deformation amount of the disc spring 9. The pre-tightening mechanism 2 should be able to generate a large constant pre-tightening force and have good elasticity, that is, a small stiffness. The pre-tightening force is determined by the deformation and stiffness of the disc spring 9. The deformation size of the disc spring 9 can be adjusted by the tightening degree of the pre-tightening nut 11 on the connecting rod 5, and the stiffness of the disc spring 9 can be adjusted by selecting different models of the disc spring 9 and stacking different numbers of the disc spring 9. When the number of the disc spring 9 is multiple, the same model is selected and arranged in sequence along the length direction of the connecting rod 5.

[0044] Preferably, to make the structure more compact, a groove is provided on the top surface of the front metal cover plate 8, so that the disc spring 9, the disc spring gasket 10 and the pre-tightening nut 11 are all located in the groove.

[0045] A piezoelectric stack 1 is sleeved on the outside of the connecting rod 5 and is clamped and pre-tightened at both ends by the rear metal cover plate 4 and the front metal cover plate 8. It is composed of a plurality of piezoelectric ceramic sheets 7 and metal electrode sheets 6 stacked alternately. The polarization directions of two adjacent piezoelectric ceramic sheets 7 are opposite, and the electric properties of two adjacent metal electrode sheets 6 are opposite. That is, the piezoelectric ceramic sheets 7 in the piezoelectric stack 1 are connected in a way of mechanical series and electrical parallel, so that the longitudinal vibrations of each piezoelectric ceramic sheet 7 can be superimposed in the same direction to ensure that the piezoelectric stack 1 can vibrate in a coordinated manner.

[0046] Specifically, the piezoelectric ceramic sheet 7 is a circular piezoelectric ceramic sheet, which is made of an emission-type high-power material, such as any one of PZT-4, PZT-8, etc. The metal electrode sheet 6 is padded between two adjacent piezoelectric ceramic sheets 7, between the lowermost piezoelectric ceramic sheet 7 and the rear metal cover plate 4, and between the topmost piezoelectric ceramic sheet 7 and the front metal cover plate 8. Then, the same metal electrode sheet 6 provides electrodes with the same polarity for two adjacent piezoelectric ceramic sheets 7, and its material is selected from any one of beryllium bronze, brass, nickel sheet, etc. Therefore, the number of metal electrode sheets 6 is 1 more than the number of piezoelectric ceramic sheets 7. Preferably, the number of piezoelectric ceramic sheets 7 in the piezoelectric stack 1 is set to be an even number. In the case where the polarization directions of two adjacent piezoelectric ceramic sheets 7 are opposite, the front and rear metal cover plates of the sandwich-type piezoelectric stack actuator are connected to the electrodes with the same polarity; for safety considerations, the front and rear metal cover plates are connected to the negative pole of the power supply. Otherwise, the electrodes connected to the metal electrode sheets 6 at both ends of the piezoelectric stack 1 have opposite electric properties. Since the front metal cover plate 8 and the rear metal cover plate 4 are connected by a connecting rod 5, a disc spring 9 and a disc spring gasket 10 made of metal, an insulating sheet should be added between the front and rear metal cover plates and the piezoelectric stack 1 to prevent the metal electrode sheets 6 at both ends from being short-circuited.

[0047] The metal electrode sheet 6 can be a thin electrode, with a thickness generally about 0.2 mm; it can also be a thick electrode, and its thickness can be selected according to specific requirements. In addition to being used as an electrode wiring, the thick electrode also has other functions such as heat dissipation. The metal electrode sheet 6 is a circular metal sheet, and a wiring terminal is provided on one side of it for connecting to an external power electrode. Preferably, the wiring terminals on two adjacent metal electrode sheets 6 are located on both sides of the connecting rod 5 respectively, and the wiring terminals of two spaced metal electrode sheets 6 are located on the same side of the connecting rod 5, which is convenient for parallel connection to the same power electrode.

[0048] Parameters such as the driving voltage, output force, and output displacement of the sandwich piezoelectric stack actuator can be controlled by the thickness, cross-sectional area of the piezoelectric ceramic sheet 7, and the total height of the piezoelectric stack 1 to meet the requirements of different application scenarios. Preferably, the height of the piezoelectric stack 1 is 10-120 mm, the outer diameter is 8-70 mm, and the inner diameter is 3-30 mm. The outer diameter size is the larger of the outer diameters of the piezoelectric ceramic sheet 7 and the metal electrode sheet 6, and the inner diameter size is the smaller of the outer diameters of the piezoelectric ceramic sheet 7 and the metal electrode sheet 6, and the inner diameter is larger than the diameter of the connecting rod 5 so that the piezoelectric ceramic sheet 7 and the metal electrode sheet 6 can be easily sleeved on the connecting rod 5.

[0049] The preloading force applied by the preloading mechanism 2 to the piezoelectric stack 1 should keep the piezoelectric ceramic sheet 7 in a compressed state during high-dynamic use to avoid cracking of the piezoelectric ceramic sheet 7. The contact surfaces between the various components inside the sandwich piezoelectric stack actuator should be smooth and flat, and the surfaces of the various bonding parts should be ground to generally reach a level close to a mirror surface. The cross-section of the connecting rod 5 and the various parts of the actuator should be kept as perpendicular as possible, otherwise the actuator may not work or cause the piezoelectric ceramic sheet 7 to crack.

[0050] The adapter 3 is arranged on the top of the front metal cover 8 and moves synchronously with the front metal cover 8 as the displacement output end of the driving mechanism. For ease of assembly, disassembly, and replacement of components, a detachable connection method is adopted between the adapter 3 and the front metal cover 8. In this embodiment, the adapter 3 is a cylindrical shell structure with an open bottom. Since the front metal cover 8 is a cylindrical structure, a threaded connection is preferably used; and since the disc spring 9, the disc spring gasket 10, and the preloading nut 11 are all located in the groove on the top of the front metal cover 8, for ease of processing and manufacturing of components and assembling the groove seat, an external thread is provided on the outer wall of the front metal cover 8, and an internal thread is provided on the inner wall of the adapter 3. Preferably, the maximum distance between the top end of the connecting rod 5 and the bottom wall of the top end of the adapter 3 is not less than the total displacement range of the longitudinal vibration of the piezoelectric stack 1, so that when the piezoelectric stack 1 longitudinally contracts and the adapter 3 moves downward, the bottom wall of its top end will not collide with the top end of the connecting rod 5.

[0051] The top output interface of the adapter 3 can be connected to external force-receiving components in different forms such as internal threads, external threads, ball heads, and flat heads to meet the requirements of different scenarios. Such as Figure 6As shown, the adapter 3 adopts a replaceable design to meet different application requirements and improve the versatility and compatibility of the actuator. According to different usage requirements, the end adapter 3 can be designed in the following various forms: internal thread type, suitable for mating with bolts to enhance fixing stability; external thread type, suitable for directly screwing into external devices to achieve rigid connection; flat head type, suitable for contacting with planes to improve displacement accuracy; ball head type, used for angle compensation to improve adaptability. In addition, the end adapter 3 of the present invention can be customized according to actual needs. For example: magnetic end, suitable for non-contact loading systems; end with damping structure, integrating damping materials or elastic elements, for high-frequency vibration control or shock buffering occasions, etc.

[0052] The working principle of the piezoelectric stack actuator in this embodiment is described in detail as follows:

[0053] See Figures 3 to 5 , when an alternating current is applied to the piezoelectric stack 1, the driving voltage applies an electric field to each layer of piezoelectric ceramic sheet 7 through the metal electrode sheet 6; when the direction of the electric field is the same as the polarization direction of the piezoelectric ceramic sheet 7, the piezoelectric stack 1 elongates axially, moves upward through the front metal cover 8 to further compress the axial deformation of the disc spring 9, and pushes the adapter 3 to move synchronously and output an extended displacement externally; when the direction of the electric field of the driving voltage is opposite to the polarization direction of the piezoelectric ceramic sheet 7, the piezoelectric stack 1 shortens axially, the disc spring 9 releases a part of the axial deformation, pushes the front metal cover 8 downward to tightly press the piezoelectric stack 1, and outputs a contracted displacement externally through the adapter 3. Therefore, the piezoelectric stack 1 generates reciprocating telescopic deformation in the height direction, thereby causing the disc spring 9 to generate up and down telescopic deformation, driving the front metal cover 8 and the adapter 3 to generate reciprocating swings in opposite directions, and the adapter 3 realizes the displacement output of the piezoelectric actuator.

[0054] To avoid depolarization of the piezoelectric ceramic sheet 7, an electric field opposite to the polarization direction of the piezoelectric ceramic sheet 7 should be avoided as much as possible during use. Since the preloading mechanism 2 has applied an axial pre-compressive force to the piezoelectric stack 1, the piezoelectric stack 1 is always in a compressed state, thereby preventing the ceramic sheets from loosening, slipping or position offset, and ensuring that the stacked structure has good initial preloading conditions and structural integrity before driving.

[0055] See Figure 3 , during the driving process, the metal electrode sheet 6 is connected to an AC power supply through electrode leads, so that an electric field acts on the piezoelectric stack 1, causing it to undergo axial deformation. The piezoelectric stack actuator can work in two driving states, forward and reverse, that is, under the action of an alternating voltage, the piezoelectric stack 1 can periodically expand and contract in the polarization direction to achieve reciprocating driving. However, in this design, the actuator mainly considers the forward driving state and uses the unidirectional deformation amount as the effective displacement output.

[0056] As Figure 4As shown, this is the forward driving state of the actuator. When the excitation voltage of the AC power supply rises, the piezoelectric stack 1 elongates in the height direction, pushing the front metal cover plate 8 and the adapter 3 upward. As Figure 5 shown, this is the reverse driving state of the actuator. When the excitation voltage of the AC power supply drops, the piezoelectric stack 1 shortens in the height direction, driving the front metal cover plate 8 and the adapter 3 downward.

[0057] Embodiment 2:

[0058] Please refer to Figures 7 to 9 , in this embodiment, the connecting rod 5 adopts a bellows-type pre-tightening structure. Specifically, the rear metal cover plate 4, the connecting rod 5, and the adapter 3 are an integral structure, and the top end of the adapter 3 is located above the top surface of the pre-tightening nut 11. The elastic pre-tightening structure is a grooved flexible hinge arranged on the inner and outer cylindrical surfaces of the connecting rod 5 and evenly distributed along the axial direction of the connecting rod 5, forming a bellows structure with equal wall thickness, so that the connecting rod 5 has a large elastic deformation ability in the axial direction. The pre-tightening nut 11 is in threaded cooperation with the connecting rod 5, and the pre-tightening nut 11 applies pressure to the front metal cover plate 8 below, thereby clamping the piezoelectric stack 1 through the front metal cover plate 8. The grooved flexible hinge generates axial elastic deformation to apply a constant pre-tightening force to the piezoelectric stack 1, so as to ensure that the piezoelectric stack 1 is always in a compressed state when the actuator vibrates.

[0059] The metal electrode plate 6 is connected to the AC power supply through an electrode lead, so that an electric field acts on the piezoelectric stack 1. The piezoelectric stack 1 undergoes axial deformation along the polarization direction. The piezoelectric stack 1 pushes the pre-tightening nut 11 upward through the front metal cover plate 8, causing the connecting rod 5 to produce tensile deformation. The deformation amount is transmitted through the pre-tightening nut 11 and the connecting rod 5, and the displacement is output through the adapter 3 of the integral structure at the end of the connecting rod 5.

[0060] Compared with the disc spring pre-tightening method, this design uses a connecting rod integrated with a flexible hinge to provide a more stable axial pre-tightening force, thereby improving the long-term reliability and dynamic performance of the piezoelectric actuator. In this embodiment, the connecting rod 5 not only serves as an axial support component for the piezoelectric ceramic sheet 7, but also serves as an elastic pre-tightening structure.

[0061] Embodiment 3:

[0062] Please refer to Figure 10 and Figure 11, the overall structure, pre-tightening method, and working process in this embodiment are basically the same as those in Embodiment 2. The connecting rod 5 also adopts a corrugated tube type pre-tightening structure, which will not be elaborated here. The difference lies in that the elastic pre-tightening structure is a straight beam-shaped notch hinge arranged on the cylindrical surface of the connecting rod 5 and evenly distributed along the axial direction of the connecting rod 5. Specifically, straight beam-shaped notch hinges are evenly arranged on the surface of the connecting rod 5 along the axial direction, and the hinges are arranged in a two-layer four-point staggered 45° uniform layout. After applying the pre-tightening force, the straight beam-shaped notch hinge applies a constant pre-tightening force to the piezoelectric stack 1 through a small elastic deformation, so as to ensure that the piezoelectric stack 1 is always in a compressed state when the actuator vibrates.

[0063] Due to the low axial stiffness of the straight beam-shaped notch hinge, after the cumulative deformation of the piezoelectric ceramic sheet 7, the piezoelectric stack 1 can obtain a larger deformation under a smaller driving force. The straight beam-shaped structure will undergo a large axial elastic deformation, so that a larger displacement output can be achieved under a lower driving force, and thus it is suitable for application scenarios that require a larger displacement output. The corrugated tube structure in Embodiment 2 has a higher stiffness than the straight beam structure in this embodiment, can provide stable axial support, and maintain good dynamic response characteristics in a high-frequency driving environment. Therefore, the structural characteristics and applicable scenarios of the two are different.

[0064] Obviously, the detachable connection method in each of the above embodiments adopts the most common threaded connection form. Under the condition of ensuring the connection strength and stability performance, other detachable mechanical connection methods such as mortise and tenon insertion, snap insertion, and interference fit insertion can also be adopted.

[0065] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0066] The above description is only the embodiments of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied to other related technical fields, shall be included in the patent protection scope of the present invention by the same token.

Claims

1. A sandwich piezoelectric stack actuator, characterized in that: It includes a piezoelectric stack (1), a pre-tightening mechanism (2) and an adapter (3); The pre-tightening mechanism (2) includes a rear metal cover plate (4), a connecting rod (5) vertically arranged on the top surface of the rear metal cover plate (4), a front metal cover plate (8) sleeved on the outer side of the top of the connecting rod (5), and a pre-tightening nut (11) threadedly connected to the top end of the connecting rod (5) and located above the front metal cover plate (8). An elastic pre-tightening structure is arranged on the connecting rod (5), and the elastic pre-tightening structure applies a pre-tightening force to the top of the front metal cover plate (8); The piezoelectric stack (1) is sleeved on the outer side of the connecting rod (5) and is clamped and pre-tightened at both ends by the rear metal cover plate (4) and the front metal cover plate (8). It is composed of a plurality of piezoelectric ceramic sheets (7) and metal electrode sheets (6) stacked alternately. The polarization directions of adjacent two piezoelectric ceramic sheets (7) are opposite, and the electrical properties of adjacent two metal electrode sheets (6) are opposite; The adapter (3) is arranged on the top of the front metal cover plate (8) and moves synchronously with the front metal cover plate (8).

2. The sandwich piezoelectric stack actuator according to claim 1, wherein: The height of the piezoelectric stack (1) is 10 - 120 mm, the outer diameter is 8 - 70 mm, and the inner diameter is 3 - 30 mm.

3. The sandwich piezoelectric stack actuator according to claim 2, wherein: The piezoelectric ceramic sheet (7) adopts an annular piezoelectric ceramic sheet.

4. The sandwich piezoelectric stack actuator according to claim 2, wherein: One side of the metal electrode sheet (6) is provided with a wiring terminal, and the wiring terminals on adjacent two metal electrode sheets (6) are respectively located on both sides of the connecting rod (5).

5. The sandwich piezoelectric stack actuator according to any one of claims 1 to 4, characterized in that: The elastic pre-tightening structure includes a disc spring (9) and a disc spring gasket (10) respectively sleeved on the outer side of the top of the connecting rod (5). The disc spring (9) is located on the top of the front metal cover plate (8), and the disc spring gasket (10) is located above the disc spring (9) and below the pre-tightening nut (11).

6. The sandwich piezoelectric stack actuator according to claim 5, wherein: The number of the disc springs (9) is multiple, and they are stacked and arranged in sequence along the length direction of the connecting rod (5).

7. The sandwich piezoelectric stack actuator according to claim 5, characterized in that: The connection between the adapter (3) and the front metal cover plate (8) is detachable, and the connection between the rear metal cover plate (4) and the connecting rod (5) is detachable.

8. The sandwich piezoelectric stack actuator according to claim 8, wherein: The adapter (3) is threadedly connected to the top of the front metal cover plate (8), and the maximum distance between the top end of the connecting rod (5) and the bottom wall of the top end of the adapter (3) is not less than the total longitudinal vibration displacement range of the piezoelectric stack (1).

9. The sandwich piezoelectric stack actuator according to any one of claims 1 to 4, characterized in that: The elastic pre-tightening structure is a grooved flexible hinge or a straight beam-shaped cut hinge arranged on the cylindrical surface of the connecting rod (5) and uniformly distributed along the axial direction of the connecting rod (5).

10. The sandwich piezoelectric stack actuator according to claim 9, characterized in that: The rear metal cover plate (4), the connecting rod (5) and the adapter (3) are of an integral structure, and the top end of the adapter (3) is located above the top surface of the pre-tightening nut (11).

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