Actuating structure based on piezoelectric bimorph and linear actuator

Abstract

The application provides an actuating structure based on a piezoelectric bimorph and a linear actuator, the actuating structure comprising a piezoelectric bimorph and an actuating piece, the piezoelectric bimorph comprising a first piezoelectric wafer, a second piezoelectric wafer and an intermediate layer, the intermediate layer being fixedly arranged between the first piezoelectric wafer and the second piezoelectric wafer; the first end of the piezoelectric bimorph being fixed, and at the second end of the piezoelectric bimorph, the intermediate layer is fixedly connected to the actuating piece through a flexible section, the flexible section being used to increase the displacement output of the actuating piece; when an excitation signal is applied to the piezoelectric bimorph, the second end of the piezoelectric bimorph reciprocates, and the flexible section drives the actuating piece to reciprocate. After the above technical scheme is adopted, the actuating structure and the linear actuator have a larger displacement output.

Description

Technical Field

[0001] This invention relates to the field of linear actuator technology, and more particularly to an actuation structure and linear actuator based on a piezoelectric bicrystalline wafer. Background Technology

[0002] In modern communications, high-gain antennas are a key component of long-distance wireless communication. With the continuous development of radar and communication systems, the demand for antennas will increase significantly. To reduce the number and quality of antennas, research on high-gain beam-scanning antennas is particularly important. Planar reflective array antennas have attracted widespread attention and research. To achieve fast beam scanning and improve scanning performance, the phase of each array patch element in the reflective array antenna must be independently controllable. Different heights of the patch elements correspond to different phase angles. To achieve independent height adjustment for each patch element, each patch element requires an actuator capable of linearly moving the patch up and down.

[0003] Currently, actuators capable of linear motion mainly include: electromagnetic motors, which achieve linear motion by moving an energized coil in a magnetic field; shape memory alloy-based rotary actuators, which achieve linear motion by using temperature changes to cause material phase changes and thus structural dimension changes; electroactivated polymers, which achieve linear motion by using high voltage to cause structural dimension changes between electrode layers; piezoelectric driven actuators: ultrasonic motors, which use the inverse piezoelectric effect to generate elliptical vibration waves between the stator and mover, enabling the mover to achieve linear motion; and inchworm motors, which achieve linear motion of the mover through alternating combinations of piezoelectric or electrostatic actuation modules.

[0004] The shortcomings of existing technologies are that, for traditional electromagnetic motors, (1) ordinary DC rotary motors, adding a lead screw and nut mechanism to the motor output end can convert rotary motion into linear motion. The actuator structure is complex and the linear output speed is relatively low; (2) voice coil motors, the actuator has a large displacement output speed. However, when the actuator is working, it is necessary to add external slide rails and sliders to position the stator and mover of the actuator respectively, resulting in the actuator having a large volume and mass. Both of the above actuators are open-loop when working, and the position accuracy of the output displacement cannot be guaranteed. If a higher displacement output accuracy is required, a displacement sensor needs to be added. This type of actuator is based on electromagnetic coils, has high power consumption and requires a lot of control lines. Moreover, due to its own heat generation, it generates thermal radiation, resulting in low energy conversion efficiency. For shape memory alloy rotary actuators, the actuator requires a long temperature conversion time during operation, resulting in a low displacement output response speed. Moreover, due to its own heat generation, there is thermal radiation, resulting in low energy conversion efficiency. During the displacement output process, it is difficult to quickly achieve quantitative displacement output. Electro-activated polymer actuators have a large size and require a high input voltage when a large displacement output is required due to the use of electrostatic opposite charge compression principle. Piezoelectric actuators, such as linear ultrasonic motors and inchworm motors, have a small size and low input voltage (power consumption), but they have a low displacement output speed and require a high-performance displacement servo system.

[0005] Furthermore, although existing technologies disclose actuation structures based on piezoelectric bicrystalline wafers, where the deformation of the piezoelectric bicrystalline wafers under voltage or current excitation conditions drives the actuator, it is clear that in existing actuation structures, the ends of the piezoelectric bicrystalline wafers are typically directly connected to the actuator (without flexible connections, such as...). Figure 1 As shown in the figure, the displacement output of the actuator in such an actuation structure is usually relatively small. Summary of the Invention

[0006] In order to overcome the above-mentioned technical defects, the purpose of this invention is to provide an actuation structure with relatively large displacement output and a linear actuator having said actuation structure.

[0007] This invention discloses an actuation structure based on a piezoelectric bicrystalline wafer, the actuation structure comprising a piezoelectric bicrystalline wafer and an actuator. The piezoelectric bicrystalline wafer includes a first piezoelectric wafer, a second piezoelectric wafer, and an intermediate layer, wherein the intermediate layer is fixedly disposed between the first piezoelectric wafer and the second piezoelectric wafer; The first end of the piezoelectric bicrystalline wafer is fixed, and at the second end of the piezoelectric bicrystalline wafer, the intermediate layer is fixedly connected to the actuator through a flexible segment, the flexible segment being used to increase the displacement output of the actuator; When an excitation signal is applied to the piezoelectric bicrystalline wafer, causing the second end of the piezoelectric bicrystalline wafer to reciprocate, the flexible segment drives the actuator to reciprocate as well.

[0008] Preferably, the local thickness of the flexible segment is less than the thickness of the intermediate layer located between the first piezoelectric wafer and the second piezoelectric wafer.

[0009] Preferably, the thickness of the flexible segment is equal to the thickness of the intermediate layer between the first piezoelectric wafer and the second piezoelectric wafer, and the flexible segment is provided with at least one hollow portion, the hollow portions being of equal size and arranged in an array at the flexible segment.

[0010] Preferably, the thickness of the flexible segment is equal to the thickness of the intermediate layer between the first piezoelectric wafer and the second piezoelectric wafer, and the length of the flexible segment is 1~2mm.

[0011] Preferably, each of the piezoelectric bicrystalline wafers has at least two layers arranged in an array.

[0012] This invention discloses a linear actuator, which includes a housing, an actuation structure as described above, a rotating shaft, and an output shaft; The first end of the piezoelectric bicrystalline wafer is fixedly connected to the housing, and the actuator is a first rack. The rotating shaft is rotatably fixed to the housing, and a first gear and a second gear are fixedly disposed on the rotating shaft, wherein the first gear meshes with the first rack; The output shaft is fixed to the housing for reciprocating linear motion, and a second rack is fixedly provided on the output shaft, which meshes with the second gear.

[0013] The second gear is a sector gear, and the pitch circle diameter of the second gear is larger than that of the first gear.

[0014] Preferably, the rotating shaft is rotatably fixed to the housing via bearings, and the rotating shaft is configured to rotate only about its own central axis.

[0015] Preferably, a first through hole is provided on the outer wall of the housing, a fixing part is provided inside the housing, a second through hole is provided on the fixing part, the output shaft passes through the first through hole and the second through hole, and the rack is located between the first through hole and the second through hole.

[0016] Preferably, the surface of the output shaft and / or the through hole is provided with a WS2 coating.

[0017] Compared with existing technologies, the above technical solution has the following advantages: 1. The actuation structure of the present invention, by providing a flexible part, enables the actuator to be flexibly connected to the piezoelectric bicrystalline wafer, thereby significantly increasing the displacement output of the actuation structure; 2. Compared with existing linear actuators, the linear actuator of the present invention has the following advantages: 1) The active unit of the linear actuator of the present invention is a piezoelectric bicrystalline wafer, which has lower power consumption and is not affected by electromagnetic interference compared with electromagnetic actuators; 2) The linear actuator of the present invention uses a piezoelectric material with a high elastic modulus as the active element, which has high structural stiffness and a faster displacement output response speed compared with shape memory alloy actuators. 3) The linear actuator of the present invention utilizes the inverse piezoelectric effect of piezoelectric materials. Since the maximum driving voltage per unit thickness of piezoelectric materials is small (15V / 10μm), the actuator has a smaller excitation voltage, requiring a smaller excitation voltage and input power compared with electroactivated polymer actuators. 4) The linear actuator of the present invention adopts a multi-piezoelectric dual-crystal structure, which has a large structural rigidity while ensuring output displacement. Compared with high-frequency small-step ultrasonic motors and inchworm motors, it has a faster displacement output response speed. 5) The linear actuator of the present invention enables the actuator to be flexibly connected to the piezoelectric bicrystalline wafer by setting the flexible part, thereby greatly increasing the displacement output of the actuator while basically maintaining the output force; 6) The linear actuator of the present invention achieves linear displacement output through the elastic deformation of dual crystals. During the linear displacement positioning process, no additional position sensor (e.g., grating ruler) is required to achieve displacement feedback. Compared with the above actuator, the linear actuators currently available on the market and reported in the literature, the servo control system of this actuator is simpler and the number of control wires is reduced. 7) The linear actuator of the present invention has a WS2 lubricating and wear-resistant coating on the surface of the output shaft and / or the surface of the through hole, thereby significantly improving the response speed and service life of the actuator. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of an actuation structure based on piezoelectric bicrystalline wafers in the prior art; Figure 2 This is a schematic diagram of an actuation structure based on a piezoelectric bicrystalline wafer in one embodiment of the present invention; Figure 3 This is a schematic diagram of an actuation structure based on a piezoelectric bicrystalline wafer in another embodiment of the present invention; Figure 4 This is a schematic diagram of an actuation structure based on a piezoelectric bicrystalline wafer in another embodiment of the present invention; Figure 5for Figure 2 A schematic diagram illustrating the relationship between the length of the flexible segment and the output displacement and output force in the embodiment; Figure 6 This is a schematic diagram of the structure of a linear actuator in one embodiment of the present invention, in which the housing is partially transparent; Figure 7 for Figure 6 A schematic diagram of the linear actuator in the embodiment.

[0019] Figure label: 10-Piezoelectric bicrystalline wafer, 11-First piezoelectric wafer, 12-Intermediate layer, 121-Flexible segment, 13-Second piezoelectric wafer, 20-Actuator, 100-Piezoelectric bicrystalline wafer, 200-First rack, 300-Housing, 310-Fixing part, 400-Rotating shaft, 410-First gear, 420-Second gear, 500-Bearing, 600-Output shaft, 610-Second rack. Detailed Implementation

[0020] The advantages of the present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments.

[0021] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0022] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0023] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0024] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0025] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0026] See appendix Figure 2 This is a schematic diagram of an actuation structure based on a piezoelectric bicrystalline wafer in one embodiment of the present invention. The actuation structure includes a piezoelectric bicrystalline wafer 10 and an actuator 20. The piezoelectric bicrystalline wafer 10 is used to drive the actuator 20 to move.

[0027] The piezoelectric bicrystalline wafer 10 includes a first piezoelectric wafer 11, a second piezoelectric wafer 13, and an intermediate layer 12, wherein the intermediate layer 12 is fixedly disposed between the first piezoelectric wafer 11 and the second piezoelectric wafer 13. Specifically, the intermediate layer 12 is an elastic beam, and the first piezoelectric wafer 11 and the second piezoelectric wafer 13 are symmetrically bonded to the elastic beam to form the piezoelectric bicrystalline wafer. The intermediate layer 12 can be a glass fiber layer. The structure and manufacturing method of the piezoelectric bicrystalline wafer have been fully disclosed in the prior art and will not be described in detail here.

[0028] The first end of the piezoelectric bicrystalline wafer 10 is fixed, for example, to the housing of the device. At the second end of the piezoelectric bicrystalline wafer 10, the intermediate layer is fixedly connected to the actuator 20 via a flexible segment 121. The flexible segment 121 extends from the intermediate layer 12. This flexible segment ensures that the ends of the first piezoelectric wafer 11 and the second piezoelectric wafer 13 are not directly abutted or fixed to the actuator 20, but rather at a certain distance, thereby significantly increasing the displacement output of the actuator 20. In this embodiment, the thickness of the flexible segment 121 is equal to the thickness of the intermediate layer 12 between the first piezoelectric wafer 11 and the second piezoelectric wafer 13. See Appendix. Figure 5As can be seen from the relationship curves in the figure, the output force increases monotonically with the increase of the length of the flexible segment 121 within the range of 0-2.0 mm. The length of the flexible segment 121 shows a significant trend of change within the range of 0-1 mm, and tends to stabilize within the range of 1-2 mm. When the length of the flexible segment 121 increases from 2.0 mm to 2.5 mm, the output force shows a decreasing trend. Therefore, the length of the flexible segment 121 in this embodiment can be taken within the range of 1-2 mm. It should be noted that the length of the flexible segment 121 mentioned here refers to the distance from the ends of the first piezoelectric wafer 11 and the second piezoelectric wafer 13 to the actuator 20. In this embodiment, the piezoelectric bicrystalline wafer 10 is provided with 3 layers, arranged in a parallel array, and each piezoelectric bicrystalline wafer 10 is fixedly connected to the actuator 20 through the flexible segment 121. By providing multiple layers of piezoelectric bicrystalline wafers, the overall structural rigidity can be improved and a larger output force can be provided. In some other embodiments, the piezoelectric bicrystalline wafer 10 may also be provided with only one layer.

[0029] When an excitation signal is applied to the piezoelectric bicrystalline wafer 10, causing the second end of the piezoelectric bicrystalline wafer 10 to reciprocate, the flexible segment 121 drives the actuator 20 to reciprocate as well. The flexible segment reduces the connection stiffness between the piezoelectric bicrystalline wafer and the actuator, and at the same time can release the interlayer misalignment / shear caused by the actuation of the piezoelectric bicrystalline wafer layers, greatly reducing the internal attraction and strain caused by the actuation, thereby significantly increasing the displacement output of the actuator.

[0030] See appendix Figure 3 This is a schematic diagram of an actuation structure based on a piezoelectric bicrystalline wafer in another embodiment of the present invention. The actuation structure in this embodiment is similar to... Figure 2 The actuation structures in the embodiments are basically the same, differing only in the flexible segment 121. In this embodiment, the flexible segment 121 is also formed by extending from the intermediate layer 12, and the local thickness of the flexible segment 121 is less than the thickness of the intermediate layer 12 between the first piezoelectric wafer 11 and the second piezoelectric wafer 13. Specifically, as can be seen from the figure, the thickness of the flexible segment 121 first gradually decreases and then gradually increases. This arrangement reduces the bending stiffness at the connection between the piezoelectric bicrystalline wafer and the actuator, thereby significantly increasing the displacement output of the actuator.

[0031] See appendix Figure 4 This is a schematic diagram of an actuation structure based on a piezoelectric bicrystalline wafer in another embodiment of the present invention. The actuation structure in this embodiment is similar to... Figure 2The actuation structure in the embodiments is basically the same, with the only difference being the flexible segment 121. In this embodiment, the flexible segment 121 is also formed by extending from the intermediate layer 12. The thickness of the flexible segment 121 is equal to the thickness of the intermediate layer 12 between the first piezoelectric wafer 11 and the second piezoelectric wafer 13. The flexible segment 121 is provided with at least one hollow portion, which is of equal size and arranged in an array at the flexible segment, in this embodiment in a linear array. The hollow portion can be formed by etching on the glass fiber intermediate layer 12. With this arrangement, the bending stiffness at the connection between the piezoelectric bicrystalline wafer and the actuator is reduced, thereby significantly increasing the displacement output of the actuator.

[0032] See appendix Figure 6 Appendix Figure 7This is a schematic diagram illustrating the structure and principle of a linear actuator according to an embodiment of the present invention. The linear actuator includes the actuation structure described above, wherein the actuating element is a first rack 200, and the piezoelectric bicrystalline wafer 100 is connected to the first rack 200 via the flexible segment described above. The linear actuator also includes a housing 300, a rotating shaft 400, and an output shaft 600. The first end of the piezoelectric bicrystalline wafer 100 is fixedly connected to the housing 300. The rotating shaft 400 is rotatably fixed to the housing 300 and is configured to rotate only about its own central axis. In this embodiment, the rotating shaft 400 is rotatably fixedly connected to the housing 300 via a bearing 500. A first gear 410 and a second gear 420 are fixedly disposed on the rotating shaft 400, and the first gear 410 and the second gear 420 are coaxially disposed with the rotating shaft 400. In some embodiments, the rotating shaft 400, the first gear 410, and the second gear 420 are integrally formed. In some embodiments, the first gear 410 and the second gear 420 can also be fixed to the rotating shaft 400 by a fixing member. The first gear 410 meshes with the first rack 200. In this embodiment, the second gear 420 is a sector gear, and the pitch circle diameter of the second gear 420 is larger than that of the first gear 410. The second gear 420 is used to amplify the angular displacement generated by the rotation of the shaft 400. The output shaft 600 is fixed to the housing 300 in a reciprocating linear motion, that is, it is configured to perform linear reciprocating motion relative to the housing 300. In this embodiment, a first through hole is provided on the outer wall of the housing 300, a fixing part 310 is provided inside the housing 300, and a second through hole is provided on the fixing part 310. The output shaft 600 passes through the first through hole and the second through hole, so that it can perform reciprocating linear motion in the two through holes. Preferably, a WS2 coating can be sputtered onto the surface of the output shaft and / or the through hole. The WS2 coating has good lubrication and wear resistance, which can significantly improve the response speed and service life of the linear actuator. A second rack 610 is fixedly mounted on the output shaft 600, and the second rack 610 meshes with the second gear 420. The second rack 610 is located between the first through hole and the second through hole. In this embodiment, the output shaft 600 has two sections: the first section is fixed to the left side of the second rack 610 and passes through the first through hole, and the second section is fixed to the right side of the second rack 610 and passes through the second through hole.

[0033] In this embodiment, when the linear actuator is working, by applying an excitation voltage to the piezoelectric bicrystalline wafer 100, the second end of the piezoelectric bicrystalline wafer 110 can perform a reciprocating motion in an approximately linear manner up and down. This, in turn, drives the first rack 200 to perform a reciprocating motion in an approximately linear manner up and down via the flexible part. The first rack 200 meshes with the first gear 410, driving the rotating shaft 400 to perform a reciprocating rotational motion. The second gear 420 meshes with the second rack 610, and the reciprocating rotation of the second gear 420 drives the second rack 610 and the output shaft 600 to perform a reciprocating linear motion. Simultaneously, since the pitch circle diameter of the second gear 420 is larger than that of the first gear 410, the angular displacement generated by the rotation of the rotating shaft 400 can be significantly amplified, thereby significantly improving the displacement output of the output shaft 600.

[0034] The linear actuator of this invention amplifies the approximately linear motion of small vertical displacement generated by the piezoelectric bicrystalline wafers into large horizontal linear motion through gears and a rack, thus realizing the reciprocating linear motion of the output shaft. Furthermore, the linear actuator can have different structures depending on the magnitude of the output linear displacement and the response time of the displacement output. The output linear displacement can be achieved by adjusting the length of the piezoelectric bicrystalline wafers; the output response time of the linear displacement can be achieved by changing the number of stacked piezoelectric bicrystalline wafers and the width of the piezoelectric bicrystalline wafers.

[0035] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. An actuation structure based on a piezoelectric bicrystalline wafer, characterized in that, Including piezoelectric bilayers and actuators, The piezoelectric bicrystalline wafer includes a first piezoelectric wafer, a second piezoelectric wafer, and an intermediate layer, wherein the intermediate layer is fixedly disposed between the first piezoelectric wafer and the second piezoelectric wafer; The first end of the piezoelectric bicrystalline wafer is fixed, and at the second end of the piezoelectric bicrystalline wafer, the intermediate layer is fixedly connected to the actuator via a flexible segment. The flexible segment is used to increase the displacement output of the actuator. The thickness of the flexible segment is less than the thickness of the intermediate layer between the first and second piezoelectric wafers; or, the thickness of the flexible segment is equal to the thickness of the intermediate layer between the first and second piezoelectric wafers, and the length of the flexible segment is 1~2mm. When an excitation signal is applied to the piezoelectric bicrystalline wafer, causing the second end of the piezoelectric bicrystalline wafer to reciprocate, the flexible segment drives the actuator to reciprocate as well.

2. The actuation structure as described in claim 1, wherein, The thickness of the flexible segment is equal to the thickness of the intermediate layer between the first and second piezoelectric wafers; characterized in that, The flexible segment has at least one hollowed-out portion, the hollowed-out portions being of equal size and arranged in an array at the flexible segment.

3. The actuation structure as described in claim 1, characterized in that, Each of the piezoelectric bicrystalline wafers has at least two layers arranged in an array.

4. A linear actuator, characterized in that, The linear actuator includes a housing, an actuation structure as described in any one of claims 1 to 3, a rotating shaft, and an output shaft; The first end of the piezoelectric bicrystalline wafer is fixedly connected to the housing, and the actuator is a first rack. The rotating shaft is rotatably fixed to the housing, and a first gear and a second gear are fixedly disposed on the rotating shaft, wherein the first gear meshes with the first rack; The output shaft is fixed to the housing for reciprocating linear motion, and a second rack is fixedly provided on the output shaft, which meshes with the second gear.

5. The linear actuator as described in claim 4, characterized in that, The second gear is a sector gear, and the pitch circle diameter of the second gear is larger than that of the first gear.

6. The linear actuator as described in claim 4, characterized in that, The shaft is rotatably fixed to the housing via bearings, and the shaft is configured to rotate only about its own central axis.

7. The linear actuator as described in claim 4, characterized in that, A first through hole is provided on the outer wall of the housing, a fixing part is provided inside the housing, a second through hole is provided on the fixing part, the output shaft passes through the first through hole and the second through hole, and the second rack is located between the first through hole and the second through hole.

8. The linear actuator as described in claim 7, characterized in that, The output shaft and / or the through hole are coated with a WS2 coating.

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