Piezoelectric actuator and camera module comprising a piezoelectric actuator

Abstract

The present disclosure relates to a piezoelectric actuator and a camera module including the same. The camera module includes a housing having an internal space, a carrier disposed in the internal space and accommodating a lens barrel in which a lens is installed, and a piezoelectric actuator disposed in the housing, supporting the carrier, and configured to apply a driving force to the carrier in an optical axis direction, wherein the piezoelectric actuator includes a driving rod extending in the optical axis direction and supporting the carrier, a bracket including an upper frame including a support surface supporting one end of the driving rod, a lower frame including at least one pair of holding surfaces facing each other and spaced apart from each other in a direction crossing the support surface, and an intermediate frame connecting the upper frame and the lower frame to each other, and a piezoelectric element fixed between the pair of holding surfaces and spaced apart from the upper frame.

Description

Technical Field

[0001] This disclosure relates to piezoelectric actuators and camera modules including piezoelectric actuators. Background Technology

[0002] Camera modules are typically installed in various electronic devices such as smartphones, cars, and smart home appliances to provide photos and videos. Although the image quality of a camera module may be slightly lower than that of a regular digital camera, it is built into most smartphones due to its excellent portability and ease of use. Camera modules have various features that enable high-quality photo and video capture, such as autofocus (AF), optical image stabilization (OIS), aperture control (IRIS), and optical zoom.

[0003] To achieve these functions, actuators that precisely control moving parts, such as lens units, are necessary. Representative types include voice coil motors (VCMs), piezoelectric actuators, electromagnetic actuators, and electrostatic actuators, which differ in their driving principles and characteristics. For example, the VCM method uses magnetic force for operation, while piezoelectric actuators work based on the principle of causing minute deformations by applying an electric field.

[0004] With the development of camera modules, the demand for miniaturized, low-power, and high-output actuators is also increasing. Therefore, there is ongoing research and development of next-generation actuator technologies that can provide new functions while overcoming the shortcomings of existing methods, and various attempts are being made to find more efficient and stable driving methods. Summary of the Invention

[0005] The summary portion of this invention is intended to provide a brief overview of the chosen concepts, which will be further described in the detailed description portion below. This summary portion is not intended to identify key or essential features of the claimed subject matter, nor is it intended to help determine the scope of the claimed subject matter.

[0006] In one general aspect, the camera module includes: a housing having an internal space; a support portion disposed within the internal space of the housing and housing a lens barrel in which a lens is mounted; and a piezoelectric actuator disposed within the housing, supporting the support portion and configured to apply a driving force to the support portion in the optical axis direction, wherein the piezoelectric actuator includes: a drive rod extending in the optical axis direction and supporting the support portion; a bracket including an upper frame, a lower frame, and a middle frame, wherein the upper frame includes a support surface supporting one end of the drive rod, the lower frame includes at least a pair of retaining surfaces facing each other and spaced apart from each other in a direction intersecting the support surfaces, and the middle frame connecting the upper frame and the lower frame to each other; and a piezoelectric element fixed between the pair of retaining surfaces and spaced apart from the upper frame.

[0007] One side surface of the drive rod can contact one corner of the load-bearing part.

[0008] The camera module may also include: a preload spring for the support portion, fixed to the support portion; and a preload spring for the housing, fixed to the housing, wherein a drive rod can be inserted between the preload spring for the support portion and the preload spring for the housing, such that the drive rod is pressed between the preload spring for the support portion and the preload spring for the housing.

[0009] A portion of the preload spring in the bearing section can be inserted into the bearing section, and another portion of the preload spring in the bearing section can protrude from the bearing section and contact the drive rod.

[0010] The opposite ends of the housing preload spring can be fixed to the adjacent sidewalls of the housing, and the middle part of the housing preload spring can contact the drive rod.

[0011] The bracket can be fixed to the housing.

[0012] The camera module may also include a rolling member disposed between the support and the housing, wherein the drive rod and the rolling member may be disposed at opposite corners of the support.

[0013] The piezoelectric element can be fixed in a pair with the lower frame of the support to maintain surface contact.

[0014] As a result of the piezoelectric element being spaced apart from the upper frame, a cavity can be formed between the piezoelectric element and the upper frame.

[0015] The middle frame can extend downwards from the opposite edge of the upper frame.

[0016] The intermediate frame may include an inclined surface that extends from the upper frame and connects to the lower frame.

[0017] The width of the piezoelectric element can be greater than the cross-sectional diameter of the drive rod.

[0018] The intermediate frame may include a first support hole, which is formed as a through opening in the intermediate frame.

[0019] The lower frame may include a second support hole, which is formed as a through opening in the lower frame.

[0020] In another general aspect, the piezoelectric actuator includes: a drive rod extending in one direction; a support including an upper frame, a lower frame, and an intermediate frame, wherein the upper frame includes a support surface supporting one end of the drive rod, the lower frame includes at least a pair of retaining surfaces facing each other and spaced apart from each other in a direction intersecting the support surfaces, and the intermediate frame connects the upper frame and the lower frame to each other; and a piezoelectric element fixed between the pair of retaining surfaces of the lower frame of the support and spaced apart from the upper frame.

[0021] The piezoelectric element can be fixed in a pair with the lower frame of the support to maintain surface contact.

[0022] As a result of the piezoelectric element being spaced apart from the upper frame, a cavity can be formed between the piezoelectric element and the upper frame.

[0023] The middle frame can extend downwards from the opposite edge of the upper frame.

[0024] The intermediate frame may include an inclined surface that extends from the upper frame and connects to the lower frame.

[0025] The width of the piezoelectric element can be greater than the cross-sectional diameter of the drive rod.

[0026] The intermediate frame may include a first support hole, which is formed as a through opening in the intermediate frame.

[0027] The lower frame may include a second support hole, which is formed as a through opening in the lower frame.

[0028] In another general aspect, the piezoelectric actuator includes: a drive rod; a support including a support surface and a pair of retaining surfaces, wherein the support surface supports one end of the drive rod such that the drive rod extends in a direction perpendicular to the support surface, and the pair of retaining surfaces face each other in a direction parallel to the support surface; and a piezoelectric element fixed between the pair of retaining surfaces, wherein the piezoelectric element is configured to bend away from the support surface in response to a voltage having a first polarity applied to the piezoelectric element, and to bend toward the support surface in response to a voltage having a second polarity opposite to the first polarity applied to the piezoelectric element, and the support is configured to deform by bending the piezoelectric element away from the support surface, causing the support surface to move away from the piezoelectric element, thereby moving the drive rod in a first direction, and is configured to deform by bending the piezoelectric element toward the support surface, causing the piezoelectric element to move toward the support surface, thereby moving the drive rod in a second direction opposite to the first direction.

[0029] The support may include: an upper frame including a support surface; a lower frame including a pair of retaining surfaces; and an intermediate frame connecting the upper frame and the lower frame to each other.

[0030] The width of the lower frame in the direction parallel to the supporting surface can be greater than the width of the upper frame in the direction parallel to the supporting surface, and the width of the middle frame in the direction parallel to the supporting surface increases from the upper frame toward the lower frame.

[0031] The intermediate frame may include a support hole, which is formed as a through opening in the intermediate frame and extends in a direction parallel to the support surface.

[0032] Other features and aspects will become apparent from the following detailed description and accompanying drawings. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a piezoelectric actuator used to illustrate the driving principle of a SIDM (Smooth Impact Drive Mechanism) piezoelectric actuator.

[0034] Figure 2 This is a graph showing the waveform of the applied voltage used to drive the SIDM piezoelectric actuator.

[0035] Figure 3 This is a perspective view showing a camera module according to an embodiment.

[0036] Figure 4 It is shown Figure 3 The exploded perspective view of the camera module shown.

[0037] Figure 5 It is shown Figure 3 The camera module shown has its cover removed from the plan view.

[0038] Figure 6 It is shown Figure 3 The camera module shown has its cover removed from the side view.

[0039] Figure 7 It is along Figure 5 The sectional view taken from line VII-VII' in the middle.

[0040] Figure 8 This is a perspective view showing a piezoelectric actuator according to an embodiment.

[0041] Figure 9 It is shown Figure 8 The side view of the piezoelectric actuator shown.

[0042] Figure 10 It is shown Figure 8 The diagram shows a simulated operating configuration of the piezoelectric actuator.

[0043] Figure 11 This is a perspective view showing a piezoelectric actuator according to another embodiment.

[0044] Figure 12 It is shown Figure 11 The figure shows a perspective view of the support for the piezoelectric actuator.

[0045] Figure 13 This is a perspective view showing a piezoelectric actuator according to another embodiment.

[0046] Figure 14 This shows the resonant frequency and driving displacement according to Figure 8 The graph shows the change in the height of the chamber of the piezoelectric actuator.

[0047] Figure 15 This shows the resonant frequency and driving displacement according to Figure 8 The graph shows the variation in the thickness of the support for the piezoelectric actuator.

[0048] Figure 16 This shows the resonant frequency and driving displacement according to Figure 11 The graph shows the variation of the horizontal length of the first support hole of the piezoelectric actuator.

[0049] Figure 17 This shows the resonant frequency and driving displacement according to Figure 11 The graph shows the variation of the vertical length of the first support hole of the piezoelectric actuator.

[0050] Throughout the accompanying drawings and detailed embodiments, the same reference numerals refer to the same elements. For purposes of clarity, illustration, and convenience, the drawings may not be drawn to scale, and the relative dimensions, scale, and depiction of elements in the drawings may be exaggerated. Detailed Implementation

[0051] The following detailed embodiments are provided to help readers gain a comprehensive understanding of the methods, apparatus, and / or systems described herein. However, various changes, modifications, and equivalents of the methods, apparatus, and / or systems described herein will become apparent upon understanding the disclosure of this application. For example, the order of operations described herein is merely illustrative and is not limited to the order set forth herein, except for operations that must occur in a specific order, as will become apparent upon understanding the disclosure of this application. Furthermore, for clarity and conciseness, descriptions of functions and structures well-known to those skilled in the art may be omitted.

[0052] The features described herein may be implemented in various forms and should not be construed as being limited to the examples described herein. Rather, the examples described herein are provided merely to illustrate some of the many possible ways in which the methods, apparatuses, and / or systems described herein will become apparent upon understanding the disclosure of this application.

[0053] The use of the word "may" in relation to examples or embodiments, such as what an example or embodiment may include or implement, means that there exists at least one example or embodiment that includes or implements such a feature, and not all examples and embodiments are necessarily limited thereto.

[0054] Throughout this specification, when an element such as a layer, region, or substrate is described as being "on," "connected to," or "attached to" another element, the element may be directly "on," directly "connected to," or directly "attached to" the other element, or there may be one or more other elements between the element and the other element, or these elements may be physically connected and electrically connected, or although they may be referred to by different names depending on their location or function, they may be integral. Conversely, when an element is described as being "directly on," "directly connected to," or "directly attached to" another element, there are no other elements between the element and the other element.

[0055] As used herein, the term “and / or” includes any one of the associated listed items and any combination of any two or more items.

[0056] Although terms such as “first,” “second,” and “third” may be used herein to describe various components, parts, regions, layers, or sections, these components, parts, regions, layers, or sections are not limited by these terms. Rather, these terms are used only to distinguish one component, part, region, layer, or section from another. Therefore, without departing from the teachings of the examples described herein, the first component, first part, first region, first layer, or first section mentioned in these examples may also be referred to as a second component, second part, second region, second layer, or second section.

[0057] Spatial relative terms such as “above,” “above,” “below,” and “under” may be used herein for descriptive convenience to describe the relationship of one element relative to another, as shown in the accompanying drawings. In addition to covering the orientation depicted in the drawings, these spatial relative terms are intended to also cover different orientations of the device in use or operation. For example, if the device in the drawings is flipped, an element described as being “above” or “above” another element would be located “below” or “under” that other element. Thus, depending on the spatial orientation of the device, the term “above” covers both orientations of “above” and “below”. The device may also be oriented in other ways (e.g., rotated 90 degrees or in other orientations), and the spatial relative terms used herein should be interpreted accordingly.

[0058] The terminology used herein is for the purpose of describing various examples only and is not intended to limit this disclosure. Unless the context clearly indicates otherwise, the terms “a,” “an,” and “the” are intended to include the plural form as well. The terms “comprising,” “including,” and “having” indicate the presence of the stated features, quantities, operations, components, elements, and / or combinations thereof, but do not preclude the presence or addition of one or more other features, quantities, operations, components, elements, and / or combinations thereof.

[0059] Furthermore, throughout the specification, "plan view" means a view obtained by observing a portion of the object from above, and "sectional view" means a view obtained by observing a cross-section of a vertically cut portion of the object from the side.

[0060] When a voltage is applied to a piezoelectric element, it undergoes mechanical deformation, such as expansion and contraction, resulting in a very small driven displacement (on the order of a few micrometers (μm)). Various methods, particularly the inchworm method, ultrasonic methods, and methods using inertial forces, are used to overcome this small driven displacement and achieve larger displacements. Among these methods, the SIDM (Smooth Impact Drive Mechanism) method using inertial forces is advantageous for application in camera modules due to its simple structure and the ability to configure the system using only a single piezoelectric element.

[0061] Figure 1 This is a schematic diagram of a piezoelectric actuator used to illustrate the driving principle of a SIDM piezoelectric actuator, and Figure 2 This is a graph showing the waveform of the applied voltage used to drive the SIDM piezoelectric actuator.

[0062] refer to Figure 1 The SIDM piezoelectric actuator 50 may include three components: a piezoelectric element 51, a rod 53, and a slider 56. Here, the piezoelectric element 51 is the main component that converts electrical energy into mechanical displacement and is firmly bonded to the rod 53 with adhesive. Typically, one surface of the piezoelectric element 51 is fixed, and the slider 56, as the moving part, is located on the rod 53 and fixed by applying a preload to the slider 56. At this time, the slider 56 is connected to the rod 53 by friction, and the piezoelectric element 51 has the characteristic of repeatedly contracting and expanding according to the voltage difference between its two ends, and the slider 56 moves accordingly using this principle.

[0063] The driving process of the SIDM driving method is as follows. First, as the driving voltage applied to the piezoelectric element 51 is slowly increased, the piezoelectric element 51 is gradually stretched, and during this process, the slider 56 moves together with the rod 53 due to friction between the slider 56 and the rod 53 (step 1 → step 2). On the other hand, when the driving voltage is rapidly reduced to quickly contract the piezoelectric element 51, the slider 56 remains in its position because the inertial force becomes greater than the frictional force, causing the rod 53 to slide past the slider 56 (step 2 → step 3). By repeating this gradual expansion and rapid contraction drive, the slider 56 can travel a long distance continuously.

[0064] exist Figure 2 The upper curve diagram shows the voltage waveform when slider 56 moves in the positive direction. Conversely, when the operation of rapid expansion and slow contraction of piezoelectric element 51 is repeated, slider 56 is driven in the opposite direction, which is applying the positive drive principle in the opposite way. Figure 2 The lower part of the graph shows the voltage waveform at this time, which is the opposite of the waveform during forward drive.

[0065] Figure 3 This is a perspective view showing a camera module according to an embodiment, and Figure 4 It is shown Figure 3 The exploded perspective view of the camera module shown.

[0066] refer to Figure 3 and Figure 4 According to this embodiment, the camera module 101 may include a lens barrel 20 for capturing an object, a support portion 41 for supporting the lens barrel 20, an image sensor unit 70 for converting optical signals into electrical signals, a housing 110 for accommodating these components, and a piezoelectric actuator 150 for realizing autofocus.

[0067] The lens barrel 20 has a hollow cylindrical shape and can accommodate one or more lenses 22 inside. Multiple lenses 22 can be aligned in a row along the optical axis and mounted in the lens barrel 20, and each lens 22 can have the same or different optical properties (such as refractive index, radius of curvature, thickness, and other properties) according to design requirements. The optical axis can be set as the central axis of the lens 22 and can be aligned with the z-axis direction, while the x-axis and y-axis, which are perpendicular to each other, can be set in directions perpendicular to the optical axis and z-axis. This coordinate system clearly defines the position and direction of movement of each component of the camera module 101.

[0068] The support portion 41 is a structure for stably supporting the lens barrel 20 and has a central hole to precisely accommodate the lens barrel 20. The support portion 41, which is combined with the lens barrel 20, can be housed within the internal space of the housing 110, and the housing 110 can have a box-shaped shape with four corners and an open top and bottom. The central hole of the support portion 41 and the central hole of the housing 110 can be precisely aligned in the optical axis direction to ensure the alignment accuracy of the optical system.

[0069] The piezoelectric actuator 150 can be disposed inside any one of the four corners of the housing 110. The piezoelectric actuator 150 can be located in the space between the outer corner of the support portion 41 and the inner corner of the housing 110, and can include a piezoelectric element 152 mechanically connected via a bracket 155. Figure 3 and Figure 4 Not shown in the image, but see [link / reference]. Figure 7 The piezoelectric element 152 is fixed to the corner of the housing 110, and the drive rod 157 can be supported by the support portion 41.

[0070] The drive rod 157 has a cylindrical shape, and its side surface can contact the load-bearing preload spring 419 and the housing preload spring 119. For example, one side of the cylindrical side surface of the drive rod 157 contacts the load-bearing preload spring 419 disposed on the outer corner of the load-bearing portion 41, and the other side of the cylindrical side surface of the drive rod 157 contacts the housing preload spring 119 fixed to the housing 110. The preload spring can be in the form of a leaf spring and can be made of a durable metal material such as stainless steel (SUS), and can apply appropriate preload to the drive rod 157 to achieve stable drive force transmission.

[0071] The piezoelectric actuator 150 can perform the function of an autofocus (AF) drive unit that moves the carrier 41 relative to the housing 110 in the optical axis direction. The piezoelectric actuator 150 can be selectively located in any of the four corners of the housing 110, and therefore, the rolling member 54 can be located diagonally opposite the corner in which the piezoelectric actuator 150 is mounted.

[0072] The rolling member 54 can be located between the support portion 41 and the housing 110 to reduce friction between the support portion 41 and the housing 110 when the support portion 41 moves. The rolling member 54 can be located diagonally opposite the piezoelectric actuator 150. The rolling member 54 has a spherical form in which multiple balls are placed on both sides of the corresponding angle of the support portion 41, which can minimize friction that occurs during the movement of the support portion 41 and enable smooth movement of the support portion 41.

[0073] The sensing magnet 415 can be located on the exterior of one side of the support portion 41. The flexible circuit board 116 is located on the exterior of one side of the housing 110, and the sensor 117 can be located on the flexible circuit board 116 at a position corresponding to the sensing magnet 415. A through hole 110a is formed in the side wall of the housing 110 to correspond to the sensor 117, and the sensor 117 and the sensing magnet 415 can be aligned to face each other through the through hole 110a. The sensor 117 can detect the position of the lens barrel 20 in the optical axis direction, and the flexible circuit board 116 can be configured to supply power to the sensor 117.

[0074] The image sensor unit 70 may be located at the bottom of the housing 110. The image sensor unit 70 is a device that converts light incident through the lens barrel 20 into an electrical signal. The image sensor unit 70 may include an image sensor 71 and a circuit board 75 connected to the image sensor 71, and may also include an infrared filter (not shown). The infrared filter is used to block light in the infrared region from the light incident through the lens barrel 20.

[0075] Cover 113 covers the outer surface of housing 110, protecting internal components from external impacts or foreign objects. Cover 113 is made of metal and effectively shields electromagnetic waves generated in camera module 101, preventing these waves from affecting surrounding electronic components in the portable electronic device. This minimizes electromagnetic interference within the electronic device and ensures stable operation.

[0076] Figure 5 It is shown Figure 3 The camera module shown has its cover removed from the plan view; Figure 6 It is shown Figure 3 The camera module shown has its side view of the cover removed; and Figure 7 It is along Figure 5 The sectional view taken from line VII-VII' in the middle.

[0077] refer to Figures 5 to 7 The drive rod 157 of the piezoelectric actuator 150 can be positioned in the space between the outer corner of the support portion 41 and the inner corner of the housing 110. The piezoelectric actuator 150 and the rolling member 54 can be positioned on the opposite side of the support portion 41, and this oblique arrangement makes balanced support and stable movement of the support portion 41 possible.

[0078] The drive rod 157 can be secured by pressing the sides of the drive rod 157 from two directions by the preload spring 419 of the support portion and the preload spring 119 of the housing. The preload spring 419 of the support portion can be securely fixed in place by engaging with the support portion 41 in an insert molding process, and a portion of it protrudes from one corner of the support portion 41 to contact the drive rod 157 and apply constant pressure. The preload spring 119 of the housing can be stably supported by fixing both ends to adjacent sidewalls of the housing 110, and the middle portion of the preload spring 119 exposed from the housing 110 contacts and presses the drive rod 157.

[0079] The load-bearing preload spring 419 and the housing preload spring 119 can precisely maintain the frictional force with the drive rod 157 positioned between them by applying a constant pressure in opposite directions. Specifically, the load-bearing preload spring 419 can be formed such that the two portions contacting the drive rod 157 face each other at a predetermined angle, and this double-contact structure can stably fix the position of the drive rod 157. The housing preload spring 119 can also provide uniform support force by bending its exposed middle portion at a predetermined angle to contact the side of the drive rod 157 at at least two points or along a portion of the circumference of the side of the drive rod 157.

[0080] The rolling member 54 is spherical and can be arranged symmetrically based on the diagonal of the support portion 41 or the housing 110. Guide grooves 411 and 111 extending along the optical axis can be recessed into the outer surface of the support portion 41 and the inner surface of the housing 110, respectively, to accommodate the rolling member 54 and guide it in the optical axis direction. The guide grooves 411 and 111 face each other, thus forming a receiving space in which the rolling member 54 can be inserted, thereby precisely guiding the linear movement of the support portion 41 in the optical axis direction.

[0081] The drive rod 157 of the piezoelectric actuator 150 can be securely attached and fixed to the bracket 155. The bracket 155 holds the piezoelectric element 152 and is fixed inside the housing 110 to stably support the piezoelectric actuator 150. When a voltage is applied to the piezoelectric element 152, the structure of the piezoelectric element 152 can deform, which causes a change in the shape of the bracket 155, thereby causing the drive rod 157 to rise or fall in the optical axis direction. The drive rod 157 is kept in contact with the support portion 41 by the preload spring 419 of the support portion and the preload spring 119 of the housing, thereby supporting the support portion 41 and realizing the precise autofocus (AF) function of the support portion 41.

[0082] Compared to conventional voice coil motor (VCM) methods, the piezoelectric actuator 150 of the camera module 101 according to this embodiment offers various advantages. Specifically, conventional voice coil motors can occupy a considerable volume by being positioned along one side of the camera module. In contrast, the piezoelectric actuator 150 can be located at a corner of the camera module 101, reducing the overall volume of the camera module 101 by approximately 8%. Furthermore, the height of the piezoelectric actuator 150 can be less than the height of the voice coil motor, reducing the overall height of the camera module 101 by approximately 12%.

[0083] Furthermore, the piezoelectric actuator 150 features a lower resonant frequency and improved drive displacement, which enhances the movement speed and accuracy of the carrier 41. As the number of layers of the piezoelectric element 152 decreases, the capacitance of the piezoelectric element 152 also decreases, thereby reducing manufacturing costs and, in particular, minimizing malfunctions and noise caused by interference between different vibration frequencies, thus providing stable drive characteristics. Through these structural features, both miniaturization and high performance of the camera module 101 can be achieved simultaneously.

[0084] Figure 8 This is a perspective view showing a piezoelectric actuator according to an embodiment, and Figure 9 It is shown Figure 8 The side view of the piezoelectric actuator shown.

[0085] refer to Figure 8 and Figure 9 The piezoelectric actuator 150 can be composed of a drive rod 157, a support 155, and a piezoelectric element 152. The support 155, as the main structure of the piezoelectric actuator 150, is formed as a single unit to ensure structural stability and may include an upper frame 1551, a middle frame 1552, and a lower frame 1553. Each frame may have different functional structures suitable for the driving characteristics of the piezoelectric actuator 150.

[0086] The upper frame 1551 of the bracket 155 may have a support surface 155a that stably supports one end of the drive rod 157. The lower frame 1553 includes at least one pair of retaining surfaces 155b, which face each other in a direction that intersects with and is spaced apart from the support surface 155a, thereby securely fixing the piezoelectric element 152. The intermediate frame 1552 structurally connects the upper frame 1551 and the lower frame 1553, thereby ensuring the overall rigidity and stability of the bracket 155.

[0087] The piezoelectric element 152 can be securely fixed between a pair of retaining surfaces 155b and spaced a predetermined distance from the upper frame 1551, thereby forming an empty space called a chamber C between them. This chamber C structure facilitates the deformation of the piezoelectric element 152, thereby improving driving efficiency. The piezoelectric element 152 can be fixed in stable contact with the retaining surfaces 155b, and in order to achieve effective driving force transmission, the width w of the piezoelectric element 152 can be designed to be greater than the cross-sectional diameter d of the drive rod 157.

[0088] The intermediate frame 1552 can extend downward from the opposite edge of the upper frame 1551, thereby providing structural rigidity. Additionally, the intermediate frame 1552 includes a sloping surface extending from the upper frame 1551 and connecting to the lower frame 1553, effectively dispersing stress caused by deformation of the piezoelectric element 152. This sloping surface structure prevents stress concentration during the actuation of the piezoelectric element 152 and improves the durability of the support 155.

[0089] The intermediate frame 1552 may have a first support hole 155c formed as a through opening. The first support hole 155c may be symmetrically formed on both sides of the intermediate frame 1552. The first support hole 155c may extend in a direction parallel to the support surface 155a. The first support hole 155c may be used to reduce the resonant frequency of the piezoelectric actuator 150 and increase the drive displacement. For example, the first support hole 155c may be a rectangular through opening, thereby maintaining structural rigidity while improving resonant characteristics. However, the shape of the first support hole 155c is not limited to a quadrilateral shape, and any shape that can reduce the resonant frequency and increase the drive displacement can be used.

[0090] Regarding the material of the bracket 155, it can be made of a metal with excellent durability, and to improve vibration characteristics, a phosphor bronze series alloy with high density and low Young's modulus can be used. These material properties can improve the response of the bracket 155 to deformation of the piezoelectric element 152, thereby improving the driving efficiency of the piezoelectric actuator 150. In addition, the excellent durability of the phosphor bronze series alloy can prevent deformation or fatigue failure of the bracket 155 even under repeated driving.

[0091] Figure 10 It is shown Figure 8 The diagram shows a simulated operating configuration of the piezoelectric actuator. Figure 10 Part (a) shows the initial state before the operation. Figure 10 Part (b) shows the state when a positive voltage is applied, and Figure 10 Section (c) shows the state when a negative voltage is applied.

[0092] refer to Figure 10The piezoelectric actuator 150 can be driven in different directions depending on the polarity of the voltage applied to the piezoelectric element 152. A sinusoidal voltage can be applied to the piezoelectric element 152, and the direction of deformation of the piezoelectric element 152 can be determined according to the polarity of the voltage, thereby controlling the direction of movement of the drive rod 157.

[0093] like Figure 10 As shown in section (a), the initial state of the piezoelectric actuator 150 allows the piezoelectric element 152 to remain in a neutral state without deformation. From this initial state, when a positive (+) voltage is applied to the piezoelectric element 152, the piezoelectric element 152 can bend and deform in the -z direction, as shown in section (a). Figure 10 As shown in section (b), at this time, due to the bending deformation of the piezoelectric element 152, the lower frame 1553 of the support 155, which is connected to the piezoelectric element 152, can receive compressive force in the inward direction. This structural deformation of the support 155 can cause the drive rod 157 to rise in the +z direction.

[0094] Conversely, when a negative (-) voltage is applied to the piezoelectric element 152, the piezoelectric element 152 can bend and deform in the +z direction, such as Figure 10 As shown in section (c). At this time, the deformation of the piezoelectric element 152 can stretch the lower frame 1553 of the support 155 in the outward direction. This structural deformation of the support 155 can cause the drive rod 157 to descend in the -z direction.

[0095] Through this structural mechanism, the bending deformation motion of the piezoelectric element 152 can be effectively converted into the linear up-and-down movement of the drive rod 157. Specifically, by controlling the period of the sinusoidal voltage applied to the piezoelectric element 152, the up-and-down movement period of the drive rod 157 can be precisely controlled. This enables the precise position control necessary for the autofocus function of the camera module.

[0096] Considering the relationship between the structure of the support 155 and the deformation of the piezoelectric element 152, when a voltage is applied, the bending deformation of the piezoelectric element 152 can be effectively transmitted to the drive rod 157 through the lower frame 1553 of the support 155. Through this structural connection, the deformation of the piezoelectric element 152 can be amplified and transmitted with the displacement of the drive rod 157, which improves the driving efficiency of the piezoelectric actuator 150 and reduces power consumption. Compared with the conventional voice coil motor method, this driving method using the bending deformation of the piezoelectric element 152 can provide faster response characteristics and higher positional accuracy.

[0097] This drive mechanism is designed to achieve stable operation even with repeated deformation of the piezoelectric element 152, providing reliable autofocus even during long-term use. Specifically, the structural design and material properties of the bracket 155 are selected to maintain durability even under repeated stress, which helps to improve the lifespan and reliability of the camera module.

[0098] Figure 11 This is a perspective view showing a piezoelectric actuator according to another embodiment, and Figure 12 It is shown Figure 11 The figure shows a perspective view of the support for the piezoelectric actuator.

[0099] refer to Figure 11 According to this embodiment, the piezoelectric actuator 160 can be composed of a drive rod 157, a bracket 165, and a piezoelectric element 152. The bracket 165 can be formed as a single structure to ensure structural stability, and can include an upper frame 1651, a middle frame 1652, and a lower frame 1653. Each frame can have different functional structures suitable for the driving characteristics of the piezoelectric actuator 160.

[0100] A first support hole 165c, in the form of a through opening, can be formed in the intermediate frame 1652. The first support hole 165c can be symmetrically formed on both sides of the intermediate frame 1652. The first support hole 165c can reduce the weight of the support 165 and allow the support 165 to deform more flexibly when the piezoelectric element 152 undergoes bending deformation. This structural feature allows the driving force of the piezoelectric element 152 to be effectively transmitted to the drive rod 157 through the support 165.

[0101] A second support hole 165d for securely engaging with the piezoelectric element 152 can be formed in the lower frame 1653. The second support hole 165d can be symmetrically formed on both sides of the lower frame 1653 to provide space between the piezoelectric element 152 and the support 165d. Uniform application of adhesive allows the driving force of the piezoelectric element 152 to be effectively transmitted to the support 165. Furthermore, the second support hole 165d is formed as a through opening, which contributes to a reduction in the overall weight of the support 165, thereby improving the driving efficiency of the piezoelectric actuator 160.

[0102] refer to Figure 12 The upper frame 1651 may include a support surface 165a for stably connecting the drive rod 157. Precision-machined grooves may be formed in the support surface 165a, allowing the drive rod 157 to be positioned precisely. This groove structure prevents the drive rod 157 from detaching from the bracket 165 and effectively transmits the driving force from the bending deformation of the piezoelectric element 152 to the drive rod 157.

[0103] The lower frame 1653 includes at least a pair of retaining surfaces 165b, which face each other and are spaced apart in a direction intersecting with the support surface 165a, thereby securely fixing the piezoelectric element 152. The intermediate frame 1652 structurally connects the upper frame 1651 and the lower frame 1653, thereby ensuring the overall rigidity and stability of the support 165. The piezoelectric element 152 can be securely fixed between the pair of retaining surfaces 165b by applying an adhesive between the piezoelectric element 152 and the support 165.

[0104] Through this integrated structure and the specialized configuration of each frame, a stable engagement between the piezoelectric element 152 and the support 165 is possible, as is the precise positioning of the drive rod 157 and the transmission of driving force. Simultaneously, improved driving efficiency can be achieved by reducing weight. Specifically, the precise connection structure between each component ensures reliable operation of the piezoelectric actuator 160.

[0105] By utilizing the second support hole 165d to ensure space for applying adhesive between the piezoelectric element 152 and the support 165, the bonding area is increased, thereby improving the bond strength. This robust bond allows the driving force of the piezoelectric element 152 to be transmitted to the support 165 without loss. Furthermore, the precise connection structure between the drive rod 157 and the support surface 165a maintains stable operating characteristics even in repetitive driving environments.

[0106] Figure 13 This is a perspective view showing a piezoelectric actuator according to another embodiment.

[0107] refer to Figure 13 According to this embodiment, the piezoelectric actuator 170 can be composed of a drive rod 157, a bracket 175, and a piezoelectric element 152. The bracket 175 can be formed as a single integral structure made of a single metal material to ensure structural stability, and can include an upper frame 1751, a middle frame 1752, and a lower frame 1753. Each frame can have different functional structures suitable for the driving characteristics of the piezoelectric actuator 170.

[0108] According to this embodiment, the support 175 of the piezoelectric actuator 170 can have a similar design to... Figure 11 The bracket 165 of the illustrated embodiment has different structural features. Unlike the bracket 165 which includes a first bracket hole 165c and a second bracket hole 165d, the bracket 175 may not have any through openings. Specifically, the intermediate frame 1752 and the lower frame 1753 may be entirely formed without any openings.

[0109] This integrated structure increases the rigidity of the bracket 175, allowing for more efficient transmission of the driving force from the piezoelectric element 152. Due to the absence of a through-hole, the bracket 175 and the piezoelectric element 152 can have an increased contact area, improving the bonding strength. This enables a more stable transmission of the driving force from the bending deformation of the piezoelectric element 152 to the drive rod 157.

[0110] Furthermore, the integral structure of the bracket 175 without through openings improves the durability of the piezoelectric actuator 170. Due to this structural feature, deformation or damage to the bracket 175 can be prevented even in repetitive driving environments, and it can maintain a stable engagement with the piezoelectric element 152 for extended periods.

[0111] The metal material and integrated structure of the bracket 175 allow the driving force of the piezoelectric element 152 to be transmitted to the drive rod 157 without loss. This improves the driving efficiency of the piezoelectric actuator 170 and helps to achieve stable autofocus.

[0112] Simulation 1

[0113] To verify the resonant frequency and driving displacement characteristics, the main design parameters of the piezoelectric actuator 150 were simulated. These parameters include the height of the chamber C, the thickness of the support 155, and the horizontal and vertical lengths of the first support hole 155c. These design parameters directly affect the driving performance of the piezoelectric actuator 150.

[0114] Figure 14 This shows the resonant frequency and driving displacement according to Figure 8 The graph shows the change in the height of the piezoelectric actuator chamber, and... Figure 15 This shows the resonant frequency and driving displacement according to Figure 8 The graph shows the variation in the thickness of the support for the piezoelectric actuator.

[0115] refer to Figure 14 For ease of reference, a piezoelectric actuator is also shown, and the height of the chamber C is shown exemplary as 0.1T (0.1mm). Figure 14 In the diagram, the relationship between the height of the chamber C and the resonant frequency and the driving displacement can be observed. Specifically, as the height of the chamber C decreases, the driving displacement increases and the resonant frequency decreases. This indicates that the height of the chamber C affects the bending deformation characteristics of the piezoelectric element 152.

[0116] refer to Figure 15 For ease of reference, a piezoelectric actuator is also shown, and the thickness of the support 155 is exemplarily shown as 0.1T (0.1mm). Figure 15In the diagram, the relationship between the thickness of the support 155 and the resonant frequency and driving displacement can be observed. As the thickness of the support 155 decreases, the driving displacement does not change significantly, but the resonant frequency increases. This indicates that the thickness of the support 155 directly affects the stiffness of the piezoelectric actuator 150.

[0117] These simulation results confirm that the driving characteristics of the piezoelectric actuator 150 can be affected by the height of the chamber C and the thickness of the support 155, and that it is advantageous to use a low chamber C height and a thin support 155 thickness.

[0118] Simulation 2

[0119] Figure 16 This shows the resonant frequency and driving displacement according to Figure 11 The graph shows the variation of the horizontal length of the first support hole of the piezoelectric actuator, and Figure 17 This shows the resonant frequency and driving displacement according to Figure 11 The graph shows the variation of the vertical length of the first support hole of the piezoelectric actuator.

[0120] refer to Figure 16 and Figure 17 It can be observed that it forms in Figure 11 The diagram illustrates the relationship between the dimensions of the first support hole 165c in the bracket 165 and the resonant frequency and drive displacement. Simulation results show that as the horizontal and vertical lengths of the first support hole 165c increase, the resonant frequency decreases and the drive displacement increases. This indicates that the dimensions of the first support hole 165c directly affect the drive characteristics of the piezoelectric actuator 160.

[0121] In this embodiment, the size of each design parameter can be set with consideration for the stability of the manufacturing process. The thickness of the bracket 165 is formed to be 0.2T (0.2 mm), which is the minimum manufacturable thickness. Although the driving characteristics can be improved as the size of the first bracket hole 165c increases, there may be constraints on the reduction of the thickness of the frame around the first bracket hole 165c. Therefore, the size of the first bracket hole 165c is set to maintain a minimum thickness of 0.2T (0.2 mm) for the top, bottom, left, and right frames of the first bracket hole 165c. Taking these design constraints into account, the height of the chamber C is set to a minimum of 0.3T (0.3 mm). Here, T represents the unit of thickness, where 1T equals 1 mm. By optimizing the size of each design parameter in this way, both the driving performance and manufacturing stability of the piezoelectric actuator 160 can be ensured simultaneously.

[0122] Simulation 3

[0123] Next, simulations were performed on various metallic materials to analyze the material properties of the support 155. Figure 8 The effects on the performance of the piezoelectric actuator 150 shown are illustrated. Specifically, stainless steel (SUS316), phosphor bronze (C5210), and beryllium copper (C1720) were used as the materials for the support 155, and the resonant frequency characteristics and drive displacement characteristics based on the materials were compared when all other shapes were identical. The results are shown in Table 1 below.

[0124] Table 1

[0125] Referring to Table 1, different results were observed for the resonant frequency and driving displacement of the bracket 155, which is made of different materials but has the same shape. Specifically, when the bracket 155 is made of phosphor bronze (C5210) with high density and low elastic modulus, the bracket 155 has the lowest resonant frequency and the largest driving displacement.

[0126] These simulation results confirm that using a metal with high density and low Young's modulus as the material for the support 155 is beneficial for improving the driving characteristics of the piezoelectric actuator 150.

[0127] Simulation 4

[0128] In order to evaluate Figure 8 The driving stability of the piezoelectric actuator 150 shown was analyzed by performing frequency analysis according to the resonant mode. The results are shown in Table 2 below.

[0129] Table 2

[0130] Referring to Table 2, the frequency of each resonant mode occurring in the piezoelectric actuator 150 is shown. Because overlap between modes can lead to malfunctions and noise in the piezoelectric actuator 150, this frequency-based analysis of the modes aims to identify interference between different resonant modes.

[0131] Specifically, it has been confirmed that the longitudinal mode representing the vibration of the drive rod 157 in the length direction occurs at 332 kHz. Observing the resonant modes that appear before and after this longitudinal mode, the first X-axis bending mode occurs at 257 kHz, and the second X-axis bending mode occurs at 425 kHz.

[0132] This frequency distribution indicates that sufficient frequency spacing has been ensured between the target driving mode (vertical mode) and adjacent modes. Specifically, there is a 75kHz gap between the vertical mode (332kHz) and the first X-axis bending mode (257kHz), and a 93kHz gap between the vertical mode (332kHz) and the second X-axis bending mode (425kHz). By ensuring this sufficient frequency spacing, stable driving of the piezoelectric actuator 150 is possible.

[0133] Simulation 5

[0134] Referring to Table 3 below, the comparison according to the embodiments can be confirmed. Figure 8 The results of the comparison example of the piezoelectric actuator 150 and the piezoelectric actuator shown are presented. The lengths of the drive rod 157 are compared under the same conditions. The comparative example of the piezoelectric actuator has a structure in which a cuboid-shaped piezoelectric element formed by stacking multiple ceramic substrates is located in the center, the drive rod is located at the top, and the weight is located at the bottom.

[0135] Table 3

[0136] As a result of the simulation, the piezoelectric actuator 150 according to this embodiment has the following advantages compared to a comparative example of a piezoelectric actuator. Specifically, the overall size and height can be reduced, and the capacitance can be reduced. Furthermore, as the resonant frequency decreases, the driven displacement increases.

[0137] In particular, regarding interference between resonant modes, the comparative example of the piezoelectric actuator has a relatively small gap of 22 kHz between the frequency of the first twist mode (413 kHz) and the frequency of the longitudinal mode (435 kHz), creating a risk of interference between these modes. On the other hand, as previously mentioned, the piezoelectric actuator 150 according to this embodiment ensures sufficient frequency spacing between adjacent resonant modes, thereby minimizing the risk of interference between modes.

[0138] Thus, the piezoelectric actuator 150 according to this embodiment has a simplified structure, improved performance, and more stable driving capability compared to the comparative example.

[0139] While this disclosure includes specific examples, it will be apparent upon understanding the disclosure of this application that various changes in form and detail may be made to these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein are for descriptive purposes only and not for limiting purposes. The description of features or aspects in each example should be considered applicable to similar features or aspects in other examples. Suitable results may still be achieved if the described techniques are performed in a different order, and / or if components in the described system, architecture, device, or circuit are combined in a different manner and / or replaced or supplemented by other components or their equivalents. Therefore, the scope of this disclosure is not limited by the specific embodiments but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents should be understood to be included in this disclosure.

Claims

1. Camera module, including: The shell has an internal space; A support portion is disposed in the internal space of the housing and houses a lens barrel in which a lens is mounted; as well as A piezoelectric actuator, disposed within the housing, supports the carrier portion and is configured to apply a driving force to the carrier portion in the optical axis direction. The piezoelectric actuator includes: A drive rod extends in the direction of the optical axis and supports the bearing portion; The support structure is formed as a single unit and includes: The upper frame includes a support surface that supports one end of the drive rod; The lower frame includes at least a pair of retaining surfaces that face each other and are spaced apart from each other in a direction intersecting the supporting surface; and The middle frame connects the upper frame and the lower frame to each other; and A piezoelectric element is fixed between the pair of retaining surfaces and spaced apart from the upper frame.

2. The camera module according to claim 1, wherein, One side surface of the drive rod contacts one corner of the bearing portion.

3. The camera module according to claim 1, further comprising: A preloaded spring is fixed to the bearing portion; as well as The housing is preloaded with a spring and fixed to the housing. The drive rod is inserted between the preload spring of the bearing portion and the preload spring of the housing, such that the drive rod is pressed between the preload spring of the bearing portion and the preload spring of the housing.

4. The camera module according to claim 3, wherein, A portion of the preloaded spring of the bearing portion is inserted into the bearing portion, and another portion of the preloaded spring of the bearing portion protrudes from the bearing portion and contacts the drive rod.

5. The camera module according to claim 3, wherein, The opposite ends of the housing preload spring are fixed to the adjacent sidewalls of the housing, and the middle portion of the housing preload spring contacts the drive rod.

6. The camera module according to claim 1, wherein, The bracket is fixed to the housing.

7. The camera module according to claim 1, further comprising a rolling member disposed between the support portion and the housing. in, The drive rod and the rolling member are respectively located at opposite angles of the bearing portion.

8. The camera module according to claim 1, wherein, The piezoelectric element is fixed to maintain surface contact with the pair of lower frames of the bracket.

9. The camera module according to claim 1, wherein, As a result of the piezoelectric element being spaced apart from the upper frame, a cavity is formed between the piezoelectric element and the upper frame.

10. The camera module according to claim 1, wherein, The intermediate frame extends downward from the opposite edge of the upper frame.

11. The camera module according to claim 1, wherein, The intermediate frame includes an inclined surface that extends from the upper frame and connects to the lower frame.

12. The camera module according to claim 1, wherein, The width of the piezoelectric element is greater than the cross-sectional diameter of the drive rod.

13. The camera module according to claim 1, wherein, The intermediate frame includes a first support hole, which forms a through opening in the intermediate frame.

14. The camera module according to claim 1, wherein, The lower frame includes a second support hole, which forms a through opening in the lower frame.

15. A piezoelectric actuator, including: The drive rod extends in one direction; The support structure is formed as a single unit and includes: The upper frame includes a support surface that supports one end of the drive rod; The lower frame includes at least a pair of retaining surfaces that face each other and are spaced apart from each other in a direction intersecting the supporting surface; and The middle frame connects the upper frame and the lower frame to each other; and A piezoelectric element is fixed between the pair of retaining surfaces of the lower frame of the bracket and spaced apart from the upper frame.

16. The piezoelectric actuator according to claim 15, wherein, The piezoelectric element is fixed to maintain surface contact with the pair of lower frames of the bracket.

17. The piezoelectric actuator according to claim 15, wherein, As a result of the piezoelectric element being spaced apart from the upper frame, a cavity is formed between the piezoelectric element and the upper frame.

18. The piezoelectric actuator according to claim 15, wherein, The intermediate frame extends downward from the opposite edge of the upper frame.

19. The piezoelectric actuator according to claim 15, wherein, The intermediate frame includes an inclined surface that extends from the upper frame and connects to the lower frame.

20. The piezoelectric actuator according to claim 15, wherein, The width of the piezoelectric element is greater than the cross-sectional diameter of the drive rod.

21. The piezoelectric actuator according to claim 15, wherein, The intermediate frame includes a first support hole, which forms a through opening in the intermediate frame.

22. The piezoelectric actuator according to claim 15, wherein, The lower frame includes a second support hole, which forms a through opening in the lower frame.

23. A piezoelectric actuator, including: Drive lever; The support structure is formed as a single unit and includes: A support surface supports one end of the drive rod such that the drive rod extends in a direction perpendicular to the support surface, and A pair of retaining surfaces facing each other in a direction parallel to the supporting surface; and The piezoelectric element is fixed between the pair of retaining surfaces. The piezoelectric element is configured to bend away from the support surface in response to a voltage having a first polarity applied to the piezoelectric element, and to bend toward the support surface in response to a voltage having a second polarity opposite to the first polarity applied to the piezoelectric element. The bracket is configured to bend and deform by the piezoelectric element away from the support surface, causing the support surface to move away from the piezoelectric element, thereby moving the drive rod in a first direction, and is also configured to bend and deform by the piezoelectric element toward the support surface, causing the support surface to move toward the piezoelectric element, thereby moving the drive rod in a second direction opposite to the first direction.

24. The piezoelectric actuator according to claim 23, wherein, The support includes: The upper frame includes the supporting surface; The lower frame includes the pair of retaining surfaces; and The middle frame connects the upper frame and the lower frame to each other.

25. The piezoelectric actuator according to claim 24, wherein, The width of the lower frame in the direction parallel to the supporting surface is greater than the width of the upper frame in the direction parallel to the supporting surface. The width of the intermediate frame increases from the upper frame toward the lower frame in a direction parallel to the supporting surface.

26. The piezoelectric actuator according to claim 24, wherein, The intermediate frame includes a support hole, which is formed as a through opening in the intermediate frame and extends in a direction parallel to the support surface.

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