Piezoelectric actuator and moving device

Abstract

In this application, a piezoelectric actuator and a moving device are proposed. Such a piezoelectric actuator includes a housing assembly having an accommodation chamber with one end open inside, a piezoelectric assembly provided in the accommodation chamber and having a plurality of piezoelectric bodies sequentially stacked in the axial direction, and at least one protection assembly provided in the accommodation chamber and at least a part of which is provided between the inner wall of the housing assembly and the outer wall of the piezoelectric assembly. When the number of the protection assemblies is two or more, the plurality of protection assemblies are arranged so as to be spaced apart vertically. According to the piezoelectric actuator proposed in this application, the problem that the ceramics stack in the conventional piezoelectric actuator is likely to break is solved.

Description

[Technical Field]

[0001] This application claims priority to the patent application filed with the China National Intellectual Property Administration on June 22, 2022, with application number 202210708090.4 and the title of the invention "Piezoelectric Actuator and Moving Device".

[0002] This application relates to the technical field of microdrives, and more particularly to piezoelectric actuators and moving devices. [Background technology]

[0003] The operating principle of the piezoelectric actuator is as follows: When a predetermined voltage is applied to a piezoelectric ceramic stack, the inverse piezoelectric effect of the piezoelectric material causes a certain amount of strain along the axial direction of the piezoelectric ceramic stack, which results in a displacement output.

[0004] However, due to limitations in assembly precision, a certain tangential force F occurs during the use of the piezoelectric actuator, as shown in Figure 1. T It is unavoidable that the stack will be subjected to stress, and in the case of a long stack with low rigidity, large radial strain occurs, making it even more likely to fracture; also, as shown in Figure 2, when rigidity decreases, the stability of the stack piezoelectric rod weakens, and due to the brittleness and insufficient adhesive strength of the piezoelectric ceramic material, the ceramic stack may fracture directly; also, as shown in Figure 3, when rigidity decreases, the resonant frequency of the ceramic stack also decreases, making it even more likely that the ceramic stack will fracture due to external excitation (vibrations during transport, shocks, etc.).

[0005] In operating conditions with longer strokes, a longer piezoelectric ceramic stack is required. However, as the piezoelectric ceramic stack length increases, the overall rigidity of the ceramic stack decreases, making it even more susceptible to fracture. [Overview of the Initiative]

[0006] In view of the shortcomings of the conventional technology described above, the present invention aims to provide a piezoelectric actuator and a moving device that solve the problem of the ceramic stack prone to fracture in conventional piezoelectric actuators, and is advantageous for realizing an operating state with a long stroke of the piezoelectric actuator.

[0007] To achieve the above-mentioned objectives and other related objectives, the present invention provides a piezoelectric actuator, such piezoelectric actuator, A housing assembly having an internal containment chamber with one end open, A piezoelectric assembly provided within the aforementioned containment chamber, having several piezoelectric elements sequentially stacked in the axial direction, The enclosure includes at least one protective assembly provided within the enclosure, at least a portion of which is provided between the inner wall of the housing assembly and the outer wall of the piezoelectric assembly, If the number of protective assemblies is two or more, the multiple protective assemblies are arranged with vertical spacing between them.

[0008] Optionally, the protective assembly is fixed on at least one side to the inner wall of the housing assembly or the outer wall of the piezoelectric assembly, and the non-fixed side includes a stopper that is in close contact with the inner wall of the housing assembly and / or the outer wall of the piezoelectric assembly, the stopper having at least one lubricating surface, the lubricating surface being provided at least on the non-fixed side of the stopper.

[0009] Selectively, the stopper is fixedly connected on the outside to the inner wall of the housing assembly, and on the inside to the outer wall of the piezoelectric assembly, with the lubricating surface provided at least on the inside of the stopper.

[0010] Selectively, the stopper is configured such that its outer side is in close contact with the inner wall of the housing assembly, its inner side is fixedly connected to the outer wall of the piezoelectric assembly, and at least the outer side of the stopper is provided with the lubricating surface.

[0011] Selectively, the stopper is configured such that its outer side is in close contact with the inner wall of the housing assembly and its inner side is in close contact with the outer wall of the piezoelectric assembly, and the lubricating surface is provided on at least the outer and inner sides of the stopper.

[0012] Optionally, if the stopper is provided at the connection point of two adjacent piezoelectric elements, the protective assembly further comprises a connecting member fixedly connected between the two adjacent piezoelectric elements, the stopper being fixedly connected to the connecting member on the inside and in close contact with the inner wall of the housing assembly on the outside, in which case the lubricating surface is provided at least on the outside of the stopper.

[0013] Selectively, a sliding groove is provided on the inner wall of the housing assembly at the location facing the stopper, and the stopper is provided within the sliding groove.

[0014] Selectively, the equivalent friction coefficient of the stopper is given by the formula

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[0015] Selectively, the piezoelectric actuator is A cover plate provided in the opening and connected to the housing assembly, having a through-hole with a stepped cross-sectional shape, The output assembly further comprises a base connected to the piezoelectric assembly, and a through member provided on the base and extending upward and passing through the through-hole, The cross-sectional shape of the output assembly is stepped, and a movement space is surrounded within the wide area of the through-hole by the output assembly and the cover plate.

[0016] Optionally, the piezoelectric actuator further includes an elastic assembly provided within the movement space and provided to go around the periphery outside the through-member.

[0017] Optionally, the elastic assembly includes a disc spring and / or a spring.

[0018] Optionally, there are a first gap and a second gap between the outer wall of the through-member and the inner wall of the through-hole, the second gap is larger than the first gap, and the first gap satisfies the formula δ1 < ω max where δ1 is the first gap and ω max is the maximum deflection of the strain due to the deflection of the piezoelectric assembly.

[0019] Optionally, the piezoelectric body includes a piezoelectric ceramic chip or a piezoelectric ceramic stack, and the piezoelectric ceramic stack includes at least two piezoelectric ceramic chips stacked up and down.

[0020] In the present application, a moving device is further proposed, and such a moving device includes the piezoelectric actuator according to any one of the above items.

[0021] As described above, in the piezoelectric actuator and moving device according to the present invention, a protective assembly is added, and by adding one or more stoppers in the radial direction of the piezoelectric assembly, the strain due to deflection of the piezoelectric assembly is reduced and its fracture is prevented; in addition, the protective assembly acts as a guide and provides a certain amount of motion space in the axial direction, so that the expansion and contraction motion of the piezoelectric assembly proceeds smoothly and unhindered, and motion locking and stacking fracture phenomena are prevented; moreover, the protective assembly is advantageous in increasing the stroke of the piezoelectric actuator by increasing the length of the piezoelectric assembly. The piezoelectric actuator according to the present invention not only has high stability and high reliability but also a longer stroke. [Brief explanation of the drawing]

[0022] [Figure 1] This is a schematic diagram illustrating how a long stack of piezoelectric actuators using conventional technology breaks when subjected to eccentric force. [Figure 2] This schematic diagram illustrates how a long stack of piezoelectric actuators using conventional technology becomes unstable and fractures under positive pressure. [Figure 3] This is a schematic diagram illustrating how a long stack of piezoelectric actuators using conventional technology can break under external excitation. [Figure 4] This is a schematic diagram showing the configuration of the piezoelectric actuator according to the present invention. [Figure 5] This is a schematic diagram showing one configuration of the protective assembly according to the present invention. [Figure 6] This is a schematic diagram showing another configuration of the protective assembly according to the present invention. [Figure 7] This is a schematic diagram showing the configuration of the cover plate, output assembly, and elastic assembly according to the present invention. [Figure 8] This is a schematic diagram illustrating the equivalent transformation of the piezoelectric assembly according to the present invention into a cantilever structure with one end fixed. [Figure 9] This is a schematic diagram illustrating the equivalent transformation of the piezoelectric assembly according to the present invention into an elongated rod structure with both ends fixed. [Figure 10] This is a schematic diagram illustrating the equivalent transformation of the piezoelectric assembly according to the present invention into a vibration system model with a simply supported beam. [Explanation of Symbols]

[0023] 10: Housing Assembly 11: Confinement Chamber 12: Sliding groove 20: Piezoelectric Assembly 21: Piezoelectric 30: Protective Assembly 31: Stopper 32: Connecting member 40: Cover plate 41: Through-hole 50: Output Assembly 51: Pedestal 52: Through member 60: Elastic assembly [Modes for carrying out the invention]

[0024] Embodiments of the present invention will be described below with specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present application from what is presented herein. The present application can be implemented or used in other different embodiments, and each detail herein can be modified or altered in various ways without departing from the spirit of the present application, based on different viewpoints and uses.

[0025] Refer to Figures 4 to 10. It should be noted that the illustrations presented in this embodiment are merely illustrative examples illustrating the basic concept of the present invention. The illustrations do not depict the number, shape, or dimensions of assemblies in actual implementation, but only show assemblies relevant to the present invention. However, the form, number, and proportions of each assembly in actual implementation can be arbitrarily changed, and the layout of those assemblies may become more complex.

[0026] As shown in Figures 4 to 7, this embodiment proposes a piezoelectric actuator comprising a housing assembly 10, a piezoelectric assembly 20, and at least one protective assembly 30. Furthermore, the piezoelectric actuator further comprises a cover plate 40 and an output assembly 50. Even further, the piezoelectric actuator further comprises an elastic assembly 60.

[0027] The housing assembly 10 has a housing chamber 11 with one end open, which is used to mount and secure the piezoelectric assembly 20. A cover plate 40 is attached and secured to the opening of the housing chamber 11, and the opening of the housing chamber 11 also serves as a joint for mounting and positioning the piezoelectric actuator externally and a joint for displacement output. In actual applications, the housing assembly 10 is typically a metal or ceramic product that serves to protect the piezoelectric assembly 20 inside.

[0028] The piezoelectric assembly 20 is housed in a housing chamber 11 and has several piezoelectric elements 21 that are sequentially stacked in the axial direction.

[0029] Specifically, the piezoelectric assembly 20 is a displacement generating structure, with one end fixed to the bottom end away from the opening of the housing chamber 11, and the other end fixedly connected to the output assembly 50; when a predetermined voltage is applied to the piezoelectric assembly 20, the inverse piezoelectric effect of the piezoelectric material causes a certain amount of strain along the axial direction of the piezoelectric assembly 20, and this strain is transmitted to the output assembly 50 as a displacement output.

[0030] More specifically, the piezoelectric element 21 includes a piezoelectric ceramic chip or a piezoelectric ceramic stack, and the piezoelectric ceramic stack includes at least two piezoelectric ceramic chips stacked vertically. In other words, the piezoelectric assembly 20 consists of at least two piezoelectric ceramic chips stacked sequentially in the axial direction; such a stacked design allows for an increased axial length of the entire piezoelectric assembly 20, and further increases the displacement output of the piezoelectric actuator.

[0031] The protective assembly 30 is located within the housing chamber 11, with at least a portion of it situated between the inner wall of the housing assembly 10 and the outer wall of the piezoelectric assembly 20; if there are two or more protective assemblies 30, the multiple protective assemblies 30 are arranged vertically with spacing between them.

[0032] Specifically, the protective assembly 30 includes a stopper 31 that is fixed on at least one side to the inner wall of the housing assembly 10 or the outer wall of the piezoelectric assembly 20, and whose non-fixed side is in close contact with the inner wall of the housing assembly 10 and / or the outer wall of the piezoelectric assembly 20, wherein the stopper 31 has at least one lubricating surface, and the lubricating surface is provided on at least the non-fixed side of the stopper 31, in other words, at least one non-fixed side of the stopper 31 is provided with a lubricating surface.

[0033] More specifically, in order to ensure the stable operation of the piezoelectric actuator, the equivalent friction coefficient of the stopper 31 is given by the formula

number

[0034] Specifically, when the stopper 31 is fixed to the inner wall of the housing assembly 10, that is, when the outer side of the stopper 31 is the fixed side and the inner side is the non-fixed side, the equivalent friction coefficient of the stopper 31 is the friction coefficient between the stopper 31 and the outer wall of the piezoelectric assembly 20; when the stopper 31 is fixed to the outer wall of the piezoelectric assembly 20, that is, when the outer side of the stopper 31 is the non-fixed side and the inner side is the fixed side, the equivalent friction coefficient of the stopper 31 is the friction coefficient between the stopper 31 and the inner wall of the housing assembly 10; when the stopper 31 is not fixed to either the inner wall of the housing assembly 10 or the outer wall of the piezoelectric assembly 20, that is, when both the outer side and the inner side of the stopper 31 are non-fixed sides, the equivalent friction coefficient of the stopper 31 is the total friction coefficient existing between the stopper 31 and the inner wall of the housing assembly 10 and between the stopper 31 and the outer wall of the piezoelectric assembly 20.

[0035] In actual applications, as long as the stopper 31 is made of a self-lubricating material (such as polytetrafluoroethylene, polyether ether ketone, etc.), the frictional force between the stopper 31 and the housing assembly 10 and / or between the stopper 31 and the piezoelectric assembly 20 will be reduced, and it will play a guiding role for the piezoelectric assembly 20. Therefore, the telescopic movement of the piezoelectric assembly 20 proceeds smoothly and unobstructed, and the phenomena of movement locking and stack breakage are prevented; in addition, the self-lubricating material has a certain degree of elasticity and plays a buffering role for the displacement and vibration in the radial direction of the piezoelectric assembly 20, so it can be prevented from breaking after being subjected to vibration or impact.

[0036] In actual applications, the shapes of the cross-sections of the accommodation chamber 11 and the piezoelectric assembly 20 are usually circular, and the stopper 31 is an annular workpiece made of a self-lubricating material; of course, the stopper 31 may also be a plurality of rectangular workpieces made of a self-lubricating material, etc., which will not affect this embodiment.

[0037] In the first example, the stopper 31 is in close contact with the inner wall of the housing assembly 10 on the outside and in close contact with the outer wall of the piezoelectric assembly 20 on the inside, and lubricating surfaces are provided on at least the outside and inside of the stopper 31. In this example, the stopper 31 is provided in an interference fit between the inner wall of the housing assembly 10 and the outer wall of the piezoelectric assembly 20, with both its inside and outside being non-fixed sides; by making its inner and outer surfaces lubricating surfaces, the frictional force between the piezoelectric assembly 20 and the stopper 31 during movement, and between the stopper 31 and the housing assembly 10 is reduced, preventing the piezoelectric assembly 20 from breaking due to large stress on the stopper 31 caused by high frictional force during the movement of the piezoelectric assembly 20, and in addition, the stopper 31 can act as a guide for the movement of the piezoelectric assembly 20.

[0038] In the second example, the stopper 31 is fixedly connected on the outside to the inner wall of the housing assembly 10 and in close contact with the outer wall of the piezoelectric assembly 20 on the inside, and a lubricating surface is provided on at least the inside of the stopper 31. In this example, the stopper 31 has a fixed side on the outside and an unfixed side on the inside; by making its inner surface a lubricating surface, the frictional force between the piezoelectric assembly 20 and the stopper 31 during motion is reduced, preventing the piezoelectric assembly 20 from breaking due to large stress on the stopper 31 caused by high frictional force during the motion of the piezoelectric assembly 20, and in addition, the stopper 31 can act as a guide for the motion of the piezoelectric assembly 20.

[0039] In the third example, the stopper 31 is fixedly connected to the outer wall of the housing assembly 10 on the outside and to the outer wall of the piezoelectric assembly 20 on the inside, and at least the outer surface of the stopper 31 is provided with a lubricating surface. In this example, the inside of the stopper 31 is the fixed side and the outside is the non-fixed side; by making its outer surface a lubricating surface, the frictional force between the stopper 31 and the housing assembly 10 during movement is reduced, preventing the piezoelectric assembly 20 from breaking due to large stress on the stopper 31 caused by high frictional force during the movement of the piezoelectric assembly 20, and in addition, the stopper 31 can act as a guide for the movement of the piezoelectric assembly 20.

[0040] As shown in Figure 6, in the fourth example, when the stopper 31 is provided at the connection point of two adjacent piezoelectric elements 21, the protective assembly 30 further comprises a connecting member 32 fixedly connected between the two adjacent piezoelectric elements 21, the stopper 31 being fixedly connected to the connecting member 32 on the inside and in close contact with the inner wall of the housing assembly 10 on the outside, and at this time, a lubricating surface is provided on the outside of the stopper 31. In this example, the stopper 31 has a fixed side on the inside and an unfixed side on the outside; by making its outer surface a lubricating surface, the frictional force between the moving stopper 31 and the housing assembly 10 is reduced, preventing the piezoelectric assembly 20 from breaking due to large stress on the stopper 31 caused by high frictional force during the movement of the piezoelectric assembly 20, and in addition, the stopper 31 can act as a guide for the movement of the piezoelectric assembly 20.

[0041] In particular, the protective assembly 30 according to the first to third examples is characterized by its simple structure, low cost, and suitability for piezoelectric actuators with low load force and moderate displacement stroke, as it only includes a stopper 31, compared to the one according to the fourth example; on the other hand, the protective assembly 30 according to the fourth example includes a connecting member 32 in addition to the stopper 31, and it is precisely because of the design of the connecting member 32 that it becomes suitable for piezoelectric actuators with longer displacement strokes.

[0042] In the example described above, if the outside of the stopper 31 is the non-fixed side, a sliding groove 12 is provided on the inner wall of the housing assembly 10 at the location facing the stopper 31, and the stopper 31 is placed within the sliding groove 12, thereby restricting the movement of the stopper 31.

[0043] As shown in Figure 7, the cover plate 40 is provided at the opening of the housing chamber 11, connected to the housing assembly 10, and has a through-hole 41 with a stepped cross-sectional shape. In actual applications, the cover plate 40 can be manufactured together with the housing assembly 10 and thus integrally molded.

[0044] The output assembly 50 has a base 51 connected to the piezoelectric assembly 20, and a through member 52 provided on the base 51 and extending upward and passing through the through opening 41; the cross-sectional shape of the output assembly 50 is stepped, and the motion space is enclosed within a wide area of ​​the through opening 41 by the output assembly 50 and the cover plate 40.

[0045] Specifically, the output assembly 50 is a rigid structure that is directly fixedly connected to the piezoelectric assembly 20 and is intended to output the position of the piezoelectric assembly 20 directly to the outer end of the piezoelectric actuator.

[0046] Specifically, there is a first gap δ1 and a second gap δ2 between the outer wall of the through member 52 and the inner wall of the through opening 41, with the second gap δ2 being larger than the first gap δ1, and the first gap δ1 being given by equation δ1 < ω max Satisfying the condition, in the formula, ω max This is the maximum deflection due to the distortion of the piezoelectric assembly.

[0047] As shown in Figure 7, the elastic assembly 60 is provided within the aforementioned motion space and is positioned to rotate around the outside of the through member 52. Specifically, the elastic assembly 60 is located between the cover plate 40 and the base 51, and the elastic force generated by its compression reacts to the piezoelectric assembly 20, preloading the piezoelectric assembly 20 and accelerating its contraction. In actual applications, the elastic assembly 60 includes a disc spring and / or a spring.

[0048] As described in the preamble (background technology), the fracture of the long stack can be divided into three types depending on the cause of fracture: (1) fracture due to eccentric force, (2) fracture due to instability of the piezoelectric rod, and (3) fracture due to vibration. Below, the performance of the piezoelectric actuator according to this embodiment will be briefly analyzed based on these three types of fracture. Here, the protective assembly 30 of the piezoelectric actuator according to this embodiment is the structure shown in the fourth example.

[0049] (1) Fracture due to eccentric force In the piezoelectric actuator structure according to this embodiment, the operating state under eccentric force is actually a state in which axial force and tangential force are coupled, and the following will explain by breaking down the two types of force-receiving conditions.

[0050] When subjected to a tangential force, the piezoelectric assembly 20 can be simplified to a cantilever structure with one end fixed, as shown in Figure 8, where F T is the tangential force acting on the cantilever structure; the strain due to the deflection of the cantilever is given by equation

number

[0051] As can be seen from the above, as the axial length of the piezoelectric assembly 20 increases, the overall rigidity

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[0052] When subjected to an axial force, as described above, if the first gap between the cover plate 40 and the output assembly 50 is controlled to be within a fairly small range, the piezoelectric assembly 20 can be simplified to an elongated rod structure with both ends fixed, as shown in Figure 9, and Euler's formula for the critical pressure of the piezoelectric rod is

number

number

[0053] As can be seen from the above, as the length of the piezoelectric assembly 20 increases, the critical pressure of the piezoelectric rod decreases significantly, making it more susceptible to fracture under pressure. For piezoelectric assemblies with fixed materials and cross-sections, the only way to increase the critical pressure of the piezoelectric rod and prevent it from fracturing under pressure is to increase the number of positioning points, thereby dividing the elongated rod into a combination of multiple short rods.

[0054] In other words, the piezoelectric assembly 20 is divided into multiple thick, short piezoelectric rods by connecting members 32, and in this case, the piezoelectric assembly 20 is equivalently transformed into multiple elongated rods with both ends fixed. For example, the piezoelectric assembly 20 is divided into (n+1) elongated rods by n connecting members 32, and the critical pressure of these piezoelectric rods is given by equation

number

[0055] (2) Breakage due to instability of the piezoelectric rod Regarding fracture due to instability of the piezoelectric rod, it is the same as fracture due to axial force as described above, and will not be explained again here.

[0056] (3) Fracture due to vibration As described above, once the first gap between the cover plate 40 and the output assembly 50 is controlled to a fairly small range, the piezoelectric assembly 20 can be simplified to a vibration system model with a simply supported beam, as shown in Figure 10. When the characteristics of the free vibration of the piezoelectric assembly were analyzed using the static strain method, the equation

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number

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[0057] As can be seen from the above, in the case of piezoelectric assemblies with predetermined materials and cross-sections, the elongated rod can also be divided into a combination of multiple short rods by increasing the number of positioning points, thereby increasing the natural frequency of the entire system and preventing the piezoelectric actuator from resonating and fracturing due to external shocks and vibrations.

[0058] In other words, the piezoelectric assembly 20 is divided into a plurality of thick, short piezoelectric rods by connecting members 32. For example, the piezoelectric assembly 20 is divided into (n+1) piezoelectric rods by n connecting members 32, and in this case, the natural frequency of the piezoelectric assembly 20 is

number

[0059] In this embodiment, a mobile device equipped with the piezoelectric actuator described above is proposed. Here, the mobile device may be any of the conventional devices to which the piezoelectric actuator is applied, and this embodiment is not limited to such devices.

[0060] To summarize the above, the piezoelectric actuator and moving device according to this application have an additional protective assembly, and by adding one or more stoppers in the radial direction of the piezoelectric assembly, the distortion due to deflection of the piezoelectric assembly is reduced and its fracture is prevented; furthermore, the protective assembly acts as a guide and provides a certain amount of axial movement space, so that the expansion and contraction motion of the piezoelectric assembly proceeds smoothly and unhindered, preventing motion locking and stacking fracture phenomena; moreover, the protective assembly is advantageous in increasing the length of the piezoelectric assembly, thereby increasing the stroke of the piezoelectric actuator. The piezoelectric actuator according to this application has not only high stability and high reliability but also a longer stroke. Therefore, this application effectively overcomes various shortcomings of the prior art and has high industrial application value.

[0061] The embodiments described above are for illustrative purposes only to illustrate the principles and effects of the present application and do not limit it. Anyone familiar with the art may modify and alter the embodiments described above without departing from the spirit and scope of the present application. Accordingly, all equivalent modifications or alterations completed by a person with general art knowledge without departing from the spirit and technical concept presented herein shall be covered by the claims of the present application.

Claims

1. A housing assembly (10) having an internal containment chamber (11) with one end open, A piezoelectric assembly (20) is provided within the aforementioned housing chamber (11), with one end fixed to the bottom away from the opening of the housing chamber (11), and having several piezoelectric elements (21) sequentially stacked in the axial direction, The system includes at least one protective assembly (30) provided within the housing chamber (11), at least a portion of which is provided between the inner wall of the housing assembly (10) and the outer wall of the piezoelectric assembly (20), If the number of protective assemblies (30) is two or more, the multiple protective assemblies (30) are arranged with vertical spacing between them. The protective assembly (30) is fixed at least one side to the inner wall of the housing assembly (10) or the outer wall of the piezoelectric assembly (20), and the unfixed side is in close contact with the inner wall of the housing assembly (10) and / or the outer wall of the piezoelectric assembly (20). The device comprises a stopper (31), the stopper (31) having at least one lubricating surface, and the lubricating surface is provided at least on the non-fixed side of the stopper (31). The equivalent friction coefficient of the stopper (31) is given by the formula [Math 1] The following conditions are met in the formula, where k is the stiffness of the stopper (31), D is the thickness of the stopper (31), δ is the distance between the inner wall of the housing assembly (10) and the outer wall of the piezoelectric assembly (20), μ is the equivalent coefficient of friction of the stopper (31), E is the Young's modulus of the stopper (31), A is the cross-sectional area of ​​the piezoelectric assembly (20), A ｉ σ is the effective pressing area of ​​the piezoelectric assembly (20) against the stopper (31), σ is the tensile strength of the piezoelectric assembly (20), σ ａｄ The tensile adhesive strength of the piezoelectric assembly (20), σ ｃｅ This is the tensile strength of the piezoelectric ceramic chip in the piezoelectric assembly (20). A piezoelectric actuator characterized by the following features.

2. The stopper (31) is fixedly connected on its outer side to the inner wall of the housing assembly (10), and its inner side is in close contact with the outer wall of the piezoelectric assembly (20). The piezoelectric actuator according to claim 1, characterized in that the lubricating surface is provided at least on the inside of the stopper (31).

3. The stopper (31) has its outer side in close contact with the inner wall of the housing assembly (10) and its inner side fixedly connected to the outer wall of the piezoelectric assembly (20). The piezoelectric actuator according to claim 1, characterized in that the lubricating surface is provided at least on the outside of the stopper (31).

4. The stopper (31) has its outer side in close contact with the inner wall of the housing assembly (10) and its inner side in close contact with the outer wall of the piezoelectric assembly (20), The piezoelectric actuator according to claim 1, characterized in that the lubricating surface is provided on at least the outside and inside of the stopper (31).

5. If the stopper (31) is provided at the connection point of two adjacent piezoelectric elements (21), the protective assembly (30) further comprises a connecting member (32) fixedly connected between the two adjacent piezoelectric elements (21), The piezoelectric actuator according to claim 1, characterized in that the stopper (31) is fixedly connected to the connecting member (32) on the inside and in close contact with the inner wall of the housing assembly (10) on the outside, and at this time, the lubricating surface is provided on the outside of the stopper (31).

6. The piezoelectric actuator according to claim 3, characterized in that a sliding groove (12) is provided on the inner wall of the housing assembly (10) at a location facing the stopper (31), and the stopper (31) is provided within the sliding groove (12).

7. The piezoelectric actuator is A cover plate (40) is provided in the opening, connected to the housing assembly (10), and has a through-hole (41) having a stepped cross-sectional shape, The output assembly (50) further comprises a base (51) connected to the piezoelectric assembly (20), and a through member (52) provided on the base (51) and extending upward and passing through the through opening (41), The piezoelectric actuator according to claim 1, characterized in that the cross-sectional shape of the output assembly (50) is stepped, and the motion space is enclosed within a wide area of ​​the through-hole (41) by the output assembly (50) and the cover plate (40).

8. The piezoelectric actuator according to claim 7, further comprising an elastic assembly (60) provided in the motion space and positioned to rotate around the outside of the through member (52).

9. The elastic assembly (60) is characterized by including a disc spring and / or a spring. The piezoelectric actuator according to claim 8.

10. Between the outer wall of the through member (52) and the inner wall of the through opening (41), there is a first gap and a second gap, the second gap is larger than the first gap, and the first gap is given by equation δ¹ < ω ｍａｘ The following conditions are met, where δ¹ is the first gap, ω ｍａｘ The piezoelectric actuator according to claim 7, wherein is the maximum deflection of the distortion due to the deflection of the piezoelectric assembly (20).

11. The piezoelectric element (21) includes a piezoelectric ceramic chip or a piezoelectric ceramic stack. The piezoelectric actuator according to claim 1, characterized in that the piezoelectric ceramic stack includes at least two piezoelectric ceramic chips stacked vertically.

12. A mobile device characterized by comprising a piezoelectric actuator according to any one of claims 1 to 11.

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