Camera drive unit

Abstract

This invention provides a lens driving device, which includes an electromechanical conversion element capable of adjusting the focus of a lens by telescopic drive. The device is characterized by including a friction part for transmitting the movement of the electromechanical conversion element. The friction part includes a friction spring, a moving body, and a friction drive shaft. The friction spring is fixed integrally with the moving body or directly serves as the moving body, and the friction spring and friction drive shaft are connected by friction. The electromechanical conversion driver is configured such that its telescopic direction is parallel or non-parallel to the optical axis of the lens.

Description

Technical Field

[0001] This invention relates to a camera drive device, specifically a camera drive device that utilizes an electromechanical conversion element such as a piezoelectric element or a friction spring. Background Technology

[0002] Currently, cameras in portable smart devices such as smartphones and smartwatches are becoming increasingly functional and high-performance. This is specifically reflected in the high pixel count of image sensors and the corresponding high performance of lenses. Although the pixel size of image sensors can be reduced to some extent through manufacturing processes to reduce camera size, the limitations of image sensor and lens manufacturing processes have pushed the limits of size reduction to the limit. Lens drivers or motors, which occupy a certain volume within the camera, are currently mainly voice coil motors (VCMs) and piezoelectric ceramic actuators (PCAs). Voice coil motors (VCMs) are widely used due to their low cost and mature mass production. However, with the increasing pixel count of mobile phone lenses, the number of lens elements in matching optical lenses has grown to 6 to 9 or even more, making the lenses increasingly heavy; and due to the need for closer-up photography, the stroke requirements for drivers are also increasing. Due to structural limitations, VCMs are increasingly unable to meet market demands in terms of driving force and stroke. Piezoelectric ceramic actuators, on the other hand, have the characteristics of high thrust, long stroke, and small size. Therefore, the adoption of piezoelectric ceramic actuators in portable smart devices such as smartphones and smartwatches is a future trend. The following section provides a detailed explanation of the driving principle of piezoelectric ceramic actuators and the structural technology of previous products.

[0003] A piezoelectric drive device consists of a piezoelectric element, a counterweight (also called a hammer) bonded to one end of the piezoelectric element, and a friction rod (friction drive shaft) bonded to the other end. The driving principle is as follows: Figure 1 The explanation is as follows:

[0004] When an application of, for example, a certain force is applied to the piezoelectric element of the piezoelectric drive device Figure 1 As shown in the sawtooth waveform voltage with a slow rise (between A and B) and a sharp drop (between B and C), the piezoelectric element, in the slow rise portion (between A and B), slowly extends axially against the drive shaft fixed to the piezoelectric element, moving together with it in its direction of travel. The moving body on the drive shaft moves together with the drive shaft due to frictional force.

[0005] When the voltage drops sharply (between B and C), the piezoelectric element rapidly retracts along the axis, and the friction shaft also quickly moves backward. At this time, as... Figure 1 As shown in (a3), due to the inertial force of the moving body being greater than the frictional force generated with the drive shaft, sliding occurs, and therefore the moving body remains essentially stationary in that position. As a result, compared to... Figure 1Compared to the initial state shown in (a1), the amount of movement of the moving body in the forward direction is the difference between the amount of movement in the forward and backward directions. By repeatedly applying a sawtooth voltage to the piezoelectric element to cause it to stretch and contract, the moving body can be driven in the forward direction. If a reverse sawtooth voltage is applied, backward drive can be achieved.

[0006] The existing structural technical solutions for piezoelectric lens actuators used in mobile phones and other smart devices are available in the following publicly available literature:

[0007] Reference 1: Japanese Patent (Patent No. 5252260);

[0008] Reference 2: Japanese Patent (Patent No. 6024798).

[0009] These actuators utilize laminated piezoelectric ceramic elements as electromechanical conversion elements to drive moving bodies. For example, in camera devices embedded in mobile devices such as smartphones, these electromechanical conversion actuators are used as driving devices to move optical lenses along the optical axis to achieve miniaturization. A fixing body is bonded to one end of the piezoelectric ceramic element, and a friction drive shaft is fixed to its other end. The moving body and the friction drive shaft are engaged with each other through friction.

[0010] In the drive device described in the aforementioned publication, the driver is arranged parallel to the optical axis of the optical lens, and the frame supporting the optical lens acts as a moving body, engaging with the friction drive shaft to move the optical lens. Furthermore, to ensure frictional engagement with the friction rod, the moving body is pressed against the friction rod by the elastic force of an elastic body.

[0011] For example, as described in references 1-2, a lens drive device is proposed that uses a piezoelectric actuator arranged parallel to the optical axis of the lens at one corner (A) of the lens frame (or bracket). The drive shaft (or rod) of the piezoelectric actuator is formed by clamping the V-groove formed in the lens frame and the pressure rod supported by the lens frame and pressed by a cylindrical helical compression spring. Figure 2-4 The illustration is shown in Reference 1. Figure 2-4 As shown, the piezoelectric actuator is positioned parallel to the optical axis of the lens at point A. Furthermore, as... Figure 2-4 As shown in the bottom side view, the thickness of the piezoelectric lens driver along the optical axis is roughly equivalent to the length of the piezoelectric driver.

[0012] Additionally, reference 2 proposes a method of arranging the piezoelectric actuator parallel to the optical axis at one corner of the lens frame, such as... Figure 5-6 As shown, a lens drive device is formed by the mutual clamping of a V-shaped planar groove formed in the lens frame and a leaf spring supported by the lens frame and arranged along the outer periphery of the lens frame onto the drive shaft of the piezoelectric actuator. The length of the piezoelectric actuator is approximately equal to the thickness of the lens drive device along its optical axis.

[0013] Because the drive shaft, piezoelectric element, and counterweight of the piezoelectric actuator are fixed in series, the thickness of the actuator will not be less than the series length, even when the piezoelectric actuator is arranged parallel to the optical axis as described in references 1 and 2. This is detrimental to the development of camera modules for smartphones or smartwatches that require further miniaturization and thinning. Summary of the Invention

[0014] To address the aforementioned problems, this invention further miniaturizes the lens driving device utilizing piezoelectric elements and other electromechanical conversion elements by employing a friction spring that is fixed integrally with the moving body or directly serves as the moving body, and the friction spring and friction drive shaft are connected through friction.

[0015] The purpose of this invention is to achieve further miniaturization of a lens driving device utilizing electromechanical conversion elements such as piezoelectric elements, with a simple structure.

[0016] The purpose of this invention is to further miniaturize a lens driving device driven by a piezoelectric element using a series fixed structure of drive shaft-piezoelectric element-weight, with low cost and simple structure.

[0017] To achieve the above objectives, one embodiment of the present invention provides a lens driving device that adjusts the focus by using a telescopic drive lens via an electromechanical conversion element. The device employs a friction spring that is either integrally fixed to a moving body or directly serves as the moving body, with the friction spring and friction drive shaft connected through friction. In the lens driving device, the friction drive shaft is fixed to one end of the electromechanical conversion element, and the fixed object is fixed to the other end.

[0018] Another embodiment of the present invention provides a lens driving device, which adjusts the focus of the lens by extending and retracting the electromechanical conversion element, such that the extension and retraction direction of the electromechanical conversion element is arranged to intersect the optical axis of the lens, and can be further miniaturized based on the friction spring solution.

[0019] The electromechanical conversion element is configured such that its extension direction is not parallel to the lens optical axis, preferably orthogonal to the lens optical axis. Orthogonal configuration is most advantageous for reducing thickness, while non-parallel and non-orthogonal configurations are slightly less effective. Compared to existing technologies, configuring the electromechanical conversion element so that its extension direction is not parallel to the lens optical axis completely avoids or reduces the influence of the length of the electromechanical conversion element on the thickness along the lens optical axis, further reducing the thickness of the lens module.

[0020] The friction drive shaft is attached to one end of the electromechanical conversion element, and the counterweight is attached to the other end of the electromechanical conversion element;

[0021] The lens driving device converts the extension / retraction direction of the electromechanical conversion element into movement along the lens optical axis via a transformation structure. The transformation structure includes:

[0022] The friction part consists of a helical torsion friction spring that is frictionally engaged with the friction drive shaft and a movable body that covers the helical torsion friction spring and moves integrally with it; wherein, the helical torsion friction spring and the movable body covering it are fixed together, and the helical torsion friction spring and the friction drive shaft are frictionally engaged; compared with the prior art, the above-mentioned arrangement of the helical torsion friction spring can reduce the circumferential size of the lens module.

[0023] The inclined surface that moves synchronously with the moving body or the lens frame (preferably integrally formed) serves as the cam drive part or cam follower part (when the inclined surface moves synchronously with the moving body, it serves as the cam drive part, and when the inclined surface moves synchronously with the lens frame, it serves as the cam follower part), and is the conversion part that converts the extension and retraction direction movement of the electromechanical conversion element into the movement of the lens optical axis direction.

[0024] And an energizing spring section that continuously energizes and presses the driven part and the driving part together by means of the spring force energizing the spring through the helical torque.

[0025] When the inclined plane moves synchronously with the moving body as the driving part of the cam, the inclined plane forms a certain angle with respect to the extension and retraction direction of the electromechanical conversion element or the optical axis direction of the lens. The inclined plane acts on the driven part that moves synchronously with the lens or its frame (preferably integrally formed) to drive the lens or lens frame.

[0026] When the inclined plane moves synchronously with the lens frame as the cam follower, the active part on the moving body contacts the cam follower, and the lens or lens frame is driven by the active part pushing the cam follower.

[0027] Wherein, the driven part and the driving part of the cam push each other through the stored force of the energizing spring, or the driven part and the driving part of the cam push each other through the stored force of the energizing spring; preferably, the energizing part of the energizing spring is approximately parallel to the inclined part of the driven part of the above-mentioned transformation structure.

[0028] Preferably, the electromechanical conversion element is a layered piezoelectric element.

[0029] Another embodiment of the present invention provides a lens driving device in which a movable body having a cam portion is frictionally coupled to a friction drive shaft. The movement of the movable body with the cam portion converts the extension / retraction direction of an electromechanical conversion element into movement along the optical axis of the lens. Specifically, the cam portion is an inclined surface forming a certain angle relative to the extension / retraction direction of the electromechanical conversion element and the optical axis of the lens. The optical axis of the lens is driven by the thrust exerted by the inclined surface of the cam, which acts as the driving part, on a driven part integrally formed with a lens frame housing the lens. Specifically, the driven part interacts with the aforementioned cam portion, which acts as the driving part, through the force of a wound helical torsion spring, with the straight arm of the spring approximately parallel to the inclined surface of the cam.

[0030] Another embodiment of the present invention provides a lens driving device, wherein a moving body having an active part that converts the movement of an electromechanical conversion element in the extension / retraction direction into movement in the optical axis direction of a lens is frictionally coupled to a friction drive shaft. Specifically, the aforementioned conversion structure has a driven part with a beveled portion integrally formed with the lens frame and forming a certain angle with respect to the extension / retraction direction of the electromechanical conversion element or the optical axis direction of the lens, and the active part and the driven part of the moving body are in contact with each other. The lens is driven by the active part pushing the driven body. Specifically, the driven part and the active part are mutually energized and pushed by an energizing spring, the energizing portion of the energizing spring being substantially parallel to the beveled portion of the driven part of the aforementioned conversion structure.

[0031] Another embodiment of the present invention provides a lens driving device, wherein a friction drive rod is bonded to one end of the electromechanical conversion element, and a fixing body is fixed to the other end. Another feature is that a movable body with a cam is frictionally engaged with the friction drive rod, converting the movement of the electromechanical conversion element in the extension / retraction direction into movement in the lens optical axis direction. The aforementioned cam is an inclined surface forming a certain angle with respect to the extension / retraction direction of the electromechanical conversion element and the lens optical axis direction, and its characteristic is that it drives the lens by pressing a driven part integrally formed with the lens frame housing the lens. In the aforementioned lens driving device, the driven part presses against the cam surface via a spring component, and the pressing portion of the spring is approximately parallel to the cam surface.

[0032] The electromechanical conversion element described in this invention can be a piezoelectric element, preferably a multilayer piezoelectric element, such as a multilayer piezoelectric ceramic.

[0033] It should be noted that the friction spring (wire spring / friction torsion spring / helical torsion friction spring) driving method of the present invention, even when applied to the common industry-standard driving structure where the extension and retraction direction of electromechanical conversion components is parallel to the optical axis of the lens, can obviously reduce the circumferential or axial dimensions of the lens module compared to the existing technology (the driving connection method of pressure rod spring or leaf spring in References 1 and 2. The pressing mechanism requires additional width in the driving axial direction, and the arrangement of the pressure spring or leaf spring in the circumferential direction also requires additional space). If the extension and retraction direction of the driving component is parallel to the optical axis of the lens, the driving structure can be implemented in any way that a person skilled in the art can conceive of based on their R&D design experience. In particular, under this configuration, the moving body fixed to the friction spring can be eliminated, and the driven components such as the lens frame can be directly pushed, further reducing the size.

[0034] The beneficial effects of the embodiments described in this invention are as follows:

[0035] 1. The friction contact area between the linear spring (friction torsion spring / helical torsion friction spring) and the drive shaft is larger than that of the flat spring used in previous technologies, which can directly drive the drive and compress the circumferential and optical axis dimensions of the drive structure.

[0036] 2. The electromechanical conversion element is configured such that its extension direction is not parallel to the lens optical axis, preferably orthogonal. At the same time, the directional power conversion is achieved by using a cam mechanism. Compared with the prior art, when the electromechanical conversion element is configured such that its extension direction is not parallel to the lens optical axis, the influence of the length dimension of the electromechanical conversion element on the thickness of the lens optical axis can be completely avoided or reduced, further reducing the thickness of the lens module and realizing a miniaturized and thinner photographic module.

[0037] 3. The friction contact area between the linear spring (friction torsion spring / helical torsion friction spring) and the drive shaft is larger than that of the flat spring used in previous technologies. Therefore, the wear caused by sliding friction will be reduced and the durability will be improved.

[0038] 4. By using a layered piezoelectric element for driving and employing a linear spring (friction torsion spring / helical torsion friction spring) to drive the moving body when the driving direction is not parallel to the optical axis, especially when it is orthogonal, the circumferential dimension of the lens module can be further reduced compared to existing technologies.

[0039] 5. The pressing part of the spring is roughly parallel to the cam surface, which can improve the accuracy of lens drive control.

[0040] The advantages and spirit of the present invention can be further understood from the following detailed description of the invention and the accompanying drawings. Attached Figure Description

[0041] Figure 1 The diagram shows the driving principle of a piezoelectric ceramic actuator in the background technology.

[0042] Figure 2 This is a front view of a piezoelectric actuator in the prior art;

[0043] Figure 3 This is a three-dimensional structural diagram of a piezoelectric actuator in the prior art;

[0044] Figure 4 This is a bottom / side view of a piezoelectric actuator in the prior art;

[0045] Figure 5 An exploded view of a piezoelectric actuator in the prior art;

[0046] Figure 6 A two-dimensional diagram of a piezoelectric actuator in the prior art;

[0047] Figure 7 This is a perspective view of the configuration of a lens driving device according to one embodiment of the present invention;

[0048] Figure 8 An exploded view showing the configuration of a lens driving device according to one embodiment of the present invention. Figure 7 (Exploded view);

[0049] Figure 9 This is a side view of the configuration of a lens driving device according to one embodiment of the present invention. Figure 11 (Left view);

[0050] Figure 10 This is a cross-sectional view of the piezoelectric actuator section of a lens driving device according to one embodiment of the present invention. Figure 11 (DD cross-sectional view);

[0051] Figure 11 This is a front view of the configuration of a lens driving device according to one embodiment of the present invention;

[0052] Figure 12 This is a working diagram of the cam section of a lens driving device according to one embodiment of the present invention. Figure 5 (CC cross-section diagram); where,

[0053] (A) indicates the starting position before the camera (long-range camera) has been activated.

[0054] (B) indicates the driving position that has been driven (close-up camera);

[0055] Figure 13 This is a perspective view of a movable body 501 having a cam drive portion 55 according to one embodiment of the present invention;

[0056] Figure 14 The diagram shows the driving voltage waveform of a lens driving device according to one embodiment of the present invention.

[0057] Figure 15 This is a perspective view showing the configuration of a lens driving device according to another embodiment of the present invention;

[0058] Figure 16 This is an exploded view showing the configuration of a lens driving device according to another embodiment of the present invention. Figure 15 (Exploded view);

[0059] Figure 17 This is a side view showing the configuration of a lens driving device according to another embodiment of the present invention. Figure 19 (Left view);

[0060] Figure 18 This is a cross-sectional view of the piezoelectric actuator section showing the configuration of a lens driving device according to another embodiment of the present invention. Figure 19 (DD cross-sectional view);

[0061] Figure 19 This is a front view showing the configuration of a lens driving device according to another embodiment of the present invention;

[0062] Figure 20 This is a working diagram of the cam section illustrating the configuration of a lens driving device according to another embodiment of the present invention. Figure 5 (CC cross-section diagram); where,

[0063] (A) indicates the starting position before the camera (long-range camera) has been activated.

[0064] (B) indicates the driving position that has been driven (close-up camera);

[0065] Figure 21 This is a perspective view of a movable body 502 having an active part 155, illustrating another embodiment of the present invention.

[0066] Figure 22 This is a three-dimensional enlarged view of the cam follower 134 (cam inclined surface) in Embodiment 2;

[0067] Figure 23 This represents the driving voltage waveform of a lens driving device according to another embodiment of the present invention.

[0068] Figure 24 This is a schematic diagram of a focusing and image stabilization drive device according to another embodiment of the present invention (in both directions along the optical axis).

[0069] Explanation of symbols: 10 Lens bracket, 11 Camera element substrate joint, 12 Guide shaft holding part, 13 Lens rotation limiting part, 14a, 14b Drive shaft holding part, 15 Moving body rotation limiting part, 16a, 16b Piezoelectric actuator holding plate mounting part, 20 Guide shaft, 30 Lens frame, 31 Lens storage part, 32 Guide part, 33 Lens group rotation limiting part, 34 Follower part, 134 Cam follower part (cam slope), 40 Piezoelectric actuator holding plate, 41a, 41 b. Mounting part, 42. Piezoelectric actuator bonding part, 501. Moving body (with cam), 502. Moving body (with driving member, without cam), 51. Fitting part, 52. Friction spring storage part, 53. Rotation limiting part, 54a, 54b. Friction spring contact part, 155. Driving part, 55. Cam driving part, 56. Energizing spring mounting part, 60. Friction spring, 61, 62. Arm part, 70. Energizing spring, 71, 72. Energizing spring arm, 135. Energizing torsion spring mounting part, 136. Energizing torsion spring contact part.

[0070] A. Lens optical axis, L. Lens group, IS image sensor, CB camera element substrate, PA. Piezoelectric actuator, P. Piezoelectric element, P1. Drive shaft bonding part, P2. Hammer bonding part, S. Friction drive shaft, W. Weight, W1. Piezoelectric element bonding part, W2. Piezoelectric actuator retaining plate bonding part

[0071] 2 lenses

[0072] 3Z-axis moving component

[0073] 30 Lens frame (Z-axis movable body), 31a Z-axis through hole a,

[0074] 321Z-axis helical spring (moving part) 321a Z-axis helical spring arm a, 321b Z-axis helical spring arm b

[0075] 331 Fitting part a

[0076] 302 Axial mating surface a, 303 Axial mating surface b

[0077] 304 circumferential mating surface a, 305 circumferential mating surface b

[0078] 4XYZ axis drive assembly

[0079] 431Z-axis SIDM, Detailed Implementation

[0080] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. However, it should be understood that the present invention is not limited to the embodiments described below, and the technical concept of the present invention can be implemented in combination with other known technologies or other technologies with the same function as those known technologies.

[0081] In the following description of specific embodiments, in order to clearly demonstrate the structure and working method of the present invention, a number of directional terms will be used for description. However, terms such as "front", "rear", "left", "right", "outer", "inner", "outward", "inward", "axial", and "radial" should be understood as convenient terms and not as limiting terms.

[0082] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0083] The following, combined with Figure 7-14 This describes one implementation of the lens driving device.

[0084] The lens holder 10 has an image sensor substrate engagement portion 11 that engages with an image sensor substrate CB to which an image sensor IS is attached, a support portion 12 for a guide post 20 that is fixed and held parallel to the optical axis (A), and a lens limiting portion 13 that prevents the lens frame 30 from rotating along the optical axis.

[0085] The lens frame 30 has a lens tube 31 for housing the lens group L, a guide portion 32 that is movably fitted with the guide post 20 along the optical axis, and a lens group rotation limiting portion 33 that is movable in the optical axis and cooperates with the lens limiting portion 13 to limit the rotation around the guide post 20 of the lens frame 30 and to position the center of the image sensor IS and the optical axis of the lens group L in the same direction.

[0086] In this way, the lens group L moves along the optical axis while keeping the center of the photosensitive chip IS aligned with the optical axis, and the distance between the lens group L and the photosensitive chip IS can change. Therefore, even if the shooting distance changes, the focal position of the lens group L can be made to match the image plane of the photosensitive chip IS.

[0087] The piezoelectric actuator PA consists of a piezoelectric element, a drive shaft S bonded to its front end face P1, and a counterweight bonded to its rear end face.

[0088] On the rear end face W2 of the aforementioned counterweight W of the aforementioned piezoelectric actuator PA, a piezoelectric actuator retaining plate 40 is attached and fixed thereto, and the retaining portions 41a and 41b of the aforementioned piezoelectric actuator retaining plate 40 are fixed to the aforementioned lens bracket 10.

[0089] The piezoelectric element P expands and contracts in the front-to-back direction (P1-P2) by the amount corresponding to the applied voltage, and the aforementioned drive shaft S moves axially in accordance with the expansion and contraction of the piezoelectric element S.

[0090] Furthermore, the drive shaft S is formed of a material with low specific gravity (e.g., carbon fiber resin), while the weight W is formed of a material with high specific gravity (e.g., tungsten). Since the expansion and contraction of the piezoelectric element P is an action that occurs within a short time of a few microseconds, the displacement of the front end surface P1 side of the drive shaft S, which has low specific gravity and low inertia, can be suppressed, while the displacement of the rear end surface P2 side of the weight W, which has high specific gravity and high inertia, can be suppressed.

[0091] Since the two ends of the drive shaft S are movable in the axial direction and held on the drive shaft mounting portions 14a and 14b of the lens holder 10, the piezoelectric actuator PA is positioned and mounted in such a way that the axis of the drive shaft is orthogonal to the optical axis.

[0092] In addition, the inner diameter is smaller than the outer diameter of the drive shaft S, the friction torsion spring 60 of the wire spring is pressed into the drive shaft S and rubs against each other, and the fitting part 51 of the moving body 501 with the cam portion is movably fitted onto the drive shaft S in the axial direction.

[0093] The movable body 501 has a friction torsion spring housing portion 52 covering the friction torsion spring 60, and friction torsion spring arms 61 and 62 of the friction torsion spring 60 respectively pressed against friction torsion spring contact portions 54a and 54b. The friction spring contact portions 54a and 54b are inclined surfaces with a certain angle relative to the axial direction. The elastic force of the friction torsion spring 60 is applied by the friction torsion spring arms 61 and 62, and the movable body 501 and the friction torsion spring 60 can move together under a certain frictional force on the drive shaft S.

[0094] Furthermore, because the friction contact area between this linear spring (friction torsion spring) and the drive shaft is larger than that of the flat spring used in previous technologies, wear caused by sliding friction is reduced, and durability is improved.

[0095] In addition, the movable body 501 has a rotation limiting part 53, which, by engaging with the movable body rotation limiting part 15 of the lens bracket 10, enables the movable body 501 to move along the axial direction of the drive shaft s while preventing rotation.

[0096] The moving body 501 has a cam drive part 55. The driven part 34 is subjected to force by the energizing spring arm 72 of the energizing spring 70 installed on the energizing spring mounting part 56, so that the driven part 34 is always in force contact with the cam drive part 55. Thus, when the moving body 501 moves in the drive shaft S direction (Y direction), it is linked with the lens frame 30 to move in the optical axis direction (Z direction).

[0097] When applied to the piezoelectric actuator PA Figure 14As shown in the voltage diagram, when the applied voltage changes rapidly, the piezoelectric element P rapidly extends (contracts), causing the drive shaft S to displace with a large acceleration, making the friction torsion spring 60 prone to sliding. When the applied voltage changes slowly, the piezoelectric element P extends (contracts) slowly, resulting in the drive shaft S displacing with a smaller acceleration, making the friction torsion spring 60 less prone to sliding.

[0098] like Figure 12 As shown in (A)(B), the cam drive portion 55 (inclined surface) is approximately parallel to the energizing spring arm portion 72, that is, the action angle of the energizing spring 70 hardly changes during the drive operation of the driver, thus reducing the difference in driving force (round trip difference) in the driving direction of the lens frame 30.

[0099] Apply to the piezoelectric actuator PA Figure 14 The voltage is shown. When the applied voltage changes drastically, the drive shaft S displaces with a large acceleration due to the rapid elongation (contraction) of the piezoelectric element P, so the friction torsion spring 60 is prone to sliding. When the applied voltage changes slowly, the drive shaft S displaces with a small acceleration due to the slow extension (contraction) of the piezoelectric element P, so the friction torsion spring 60 becomes less prone to sliding.

[0100] By utilizing the round-trip difference in displacement acceleration of the drive shaft S caused by the applied voltage waveform, the movable body 501, which can move integrally with the friction torsion spring 60, is moved in a predetermined direction, thereby moving the lens frame 30 linked with the movable body 501, so that the distance of the lens group L relative to the photosensitive chip IS can be changed.

[0101] For example, by repeatedly applying a voltage that rises sharply and falls slowly as shown in Figure (a), the lens group L is driven forward; and by repeatedly applying a voltage that rises slowly and falls sharply as shown in Figure (b), the lens group L is driven backward.

[0102] The following, combined with Figure 15-23 This describes another implementation of the lens drive device.

[0103] like Figure 15 As shown in 16 and 20, the lens holder 10 has an image sensor substrate engagement portion 11 that engages with an image sensor substrate CB to which an image sensor IS is attached, a support portion 12 for a guide post 20 that is fixed and held parallel to the optical axis (A), and a lens limiting portion 13 that prevents the lens frame 30 from rotating along the optical axis.

[0104] The lens frame 30 has a lens tube 31 for housing the lens group L, a guide portion 32 that is movably fitted with the guide post 20 along the optical axis, and a lens group rotation limiting portion 33 that is movable in the optical axis and cooperates with the lens limiting portion 13 to limit the rotation around the guide post 20 of the lens frame 30 and to position the center of the image sensor IS and the optical axis of the lens group L in the same direction.

[0105] In this way, the lens group L moves along the optical axis while keeping the center of the photosensitive chip IS aligned with the optical axis, and the distance between the lens group L and the photosensitive chip IS can change. Therefore, even if the shooting distance changes, the focal position of the lens group L can be made to match the image plane of the photosensitive chip IS.

[0106] The piezoelectric actuator PA consists of a piezoelectric element, a drive shaft S bonded to its front end face P1, and a counterweight bonded to its rear end face.

[0107] On the rear end face W2 of the aforementioned counterweight W of the aforementioned piezoelectric actuator PA, a piezoelectric actuator retaining plate 40 is attached and fixed thereto, and the retaining portions 41a and 41b of the aforementioned piezoelectric actuator retaining plate 40 are fixed to the aforementioned lens bracket 10.

[0108] The piezoelectric element P expands and contracts in the front-to-back direction (P1-P2) by the amount corresponding to the applied voltage, and the aforementioned drive shaft S moves axially in accordance with the expansion and contraction of the piezoelectric element S.

[0109] Furthermore, the drive shaft S is formed of a material with low specific gravity (e.g., carbon fiber resin), while the weight W is formed of a material with high specific gravity (e.g., tungsten). Since the expansion and contraction of the piezoelectric element P is an action that occurs within a short time of a few microseconds, the displacement of the front end surface P1 side of the drive shaft S, which has low specific gravity and low inertia, can be suppressed, while the displacement of the rear end surface P2 side of the weight W, which has high specific gravity and high inertia, can be suppressed.

[0110] Since the two ends of the drive shaft S are movable in the axial direction and held on the drive shaft mounting portions 14a and 14b of the lens holder 10, the piezoelectric actuator PA is positioned and mounted in such a way that the axis of the drive shaft is orthogonal to the optical axis.

[0111] In addition, the inner diameter is smaller than the outer diameter of the drive shaft S. The spiral torsion spring 60, which is a coil spring, is pressed into the drive shaft S and rubs against each other. The fitting part 51 of the moving body 502 is movably fitted onto the drive shaft S along the axial direction.

[0112] like Figure 17As shown in 18, 19, 20, and 21, the movable body 502 with the active part 155 has a friction torsion spring housing part 52 covering the friction torsion spring 60 and friction torsion spring arms 61 and 62 of the friction torsion spring 60 respectively pressed against friction torsion spring contact parts 54a and 54b. The friction spring contact parts 54a and 54b are inclined surfaces with a certain angle to the axial direction. The elastic force of the friction torsion spring 60 is applied by the friction torsion spring arms 61 and 62, so that the movable body 502 and the friction torsion spring 60 can be subjected to a certain frictional force on the drive shaft S and move as a whole.

[0113] Furthermore, because the friction contact area between this linear spring (friction torsion spring) and the drive shaft is larger than that of the flat spring used in previous technologies, wear caused by sliding friction is reduced, and durability is improved.

[0114] In addition, the movable body 502 has a rotation limiting part 53, which, by engaging with the movable body rotation limiting part 15 of the lens bracket 10, enables the movable body 502 to move along the axial direction of the drive shaft s while preventing rotation.

[0115] The moving body 502 has an active part 155 that contacts a cam follower (sloping surface) 134 integrally formed with the lens frame. An energizing spring 70 is mounted on an energizing torsion spring mounting part 135, and the arms 72 and 71 of the energizing spring are respectively mounted on the active part 155 and the energizing torsion spring contact part 136 integrally formed with the lens frame 30, and press against them. Due to the pushing force of the torque applied by the energizing spring 70 to the active part 155 and the cam follower (sloping surface) 134, the cam follower (134) is always in force contact with the active part 155 on the moving body 502, so that when the moving body 502 moves in the drive shaft S direction (Y direction), it is linked with the lens frame 30, which can move in the optical axis direction (Z direction).

[0116] When applied to the piezoelectric actuator PA Figure 22 As shown in the voltage diagram, when the applied voltage changes rapidly, the piezoelectric element P rapidly extends (contracts), causing the drive shaft S to displace with a large acceleration, making the friction torsion spring 60 prone to sliding. When the applied voltage changes slowly, the piezoelectric element P extends (contracts) slowly, resulting in the drive shaft S displacing with a smaller acceleration, making the friction torsion spring 60 less prone to sliding.

[0117] like Figure 20 As shown in (A)(B), the cam follower (inclined surface) 134 is approximately parallel to the arm 72 of the energizing torsion spring, that is, the angle of action of the energizing spring 70 hardly changes during the driving operation of the driver, thus reducing the difference in driving force (round trip difference) in the driving direction of the lens frame 30.

[0118] Apply to the piezoelectric actuator PA Figure 22 The voltage is shown. When the applied voltage changes drastically, the drive shaft S displaces with a large acceleration due to the rapid elongation (contraction) of the piezoelectric element P, so the friction torsion spring 60 is prone to sliding. When the applied voltage changes slowly, the drive shaft S displaces with a small acceleration due to the slow extension (contraction) of the piezoelectric element P, so the friction torsion spring 60 becomes less prone to sliding.

[0119] By utilizing the round-trip difference in displacement acceleration of the drive shaft S caused by the applied voltage waveform, the movable body 502, which can move integrally with the friction torsion spring 60, is moved in a predetermined direction, thereby moving the lens frame 30 linked with the movable body 502, so that the distance of the lens group L relative to the photosensitive chip IS can be changed.

[0120] For example, by repeatedly applying a voltage that rises sharply and falls slowly as shown in Figure (a), the lens group L is driven forward; and by repeatedly applying a voltage that rises slowly and falls sharply as shown in Figure (b), the lens group L is driven backward.

[0121] The following, combined with Figure 24 This describes an implementation of a lens driving device in which the electromechanical conversion element is configured such that its extension and retraction direction is parallel to the optical axis of the lens.

[0122] like Figure 24 As shown, the inner diameter of the Z-axis helical spring 321 and the outer diameter of the drive shaft of the Z-axis SIDM 431 are fitted together, generating frictional force to fix them in place. The Z-axis helical spring 321 is fixed in the axial and axial directions by the fitting of the Z-axis helical spring arm a 32a with the circumferential fitting surface a 304 and the axial fitting surface a 302 of the fitting part a 331, and the Z-axis helical spring arm b 32b is fixed in the axial and circumferential directions by the fitting of the fitting part a 331 with the circumferential fitting surface b 305 and the axial fitting surface b 303. When a pulse voltage of appropriate frequency is applied to the Z-axis SIDM 431, the Z-axis helical spring 321 moves in a specified direction due to the frictional force between itself and the drive shaft of the Z-axis SIDM 431. Furthermore, the Z-axis helical spring 321 is restricted in the axial and circumferential directions by the drive shaft of the fitting part a 331, so that the arm of the Z-axis helical spring 321 in the forward direction drives the fitting part a 331, that is, drives the lens frame 30 of the driven body to move together in the Z-axis (i.e. optical axis direction), that is, AF focusing drive.

[0123] Compared to the friction structure used in the prior art to generate friction, this solution uses the inner diameter of a helical spring and its interlocking mechanism on the outer diameter of the piezoelectric drive shaft as the moving part, thus reducing the size of the friction structure. Even using the same drive shaft configuration parallel to the optical axis as the prior art, it still has the technical advantage of miniaturization in the drive shaft direction. Furthermore, unlike the prior art where there are only a few points of contact on the circumferential section of the drive shaft, the continuous full-circumference friction contact of the helical spring makes the friction force more stable. The reduced loss at the concentrated points of friction force improves reliability.

[0124] The advantages are summarized as follows:

[0125] 1. By using a helical spring to form the moving part, the space of the friction structure can be reduced.

[0126] 2. Because the contact with the drive shaft of the moving parts is spiral, the pressure is relatively dispersed, and the contact parts are not easily worn.

[0127] Unless otherwise specified, qualifiers such as "first" and "second" in this document do not refer to limitations on chronological order, quantity, or importance, but are merely used to distinguish one technical feature from another in this technical solution. Similarly, qualifiers such as "one" do not refer to limitations on quantity, but describe technical features not mentioned previously. Likewise, modifiers such as "approximately" or "about" preceding numerals in this document usually include the number itself, and their specific meaning should be understood in conjunction with the context. Similarly, unless a noun is modified by a specific quantifier, it should be considered in this document as including both singular and plural forms; the technical solution may include either a singular or plural number of the technical feature.

[0128] The embodiments described in this specification are merely preferred embodiments of the present invention, and are only used to illustrate the technical solutions of the present invention and not to limit the present invention. Any technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation should be within the scope of the present invention.

Claims

1. A driving device for a camera, which can include a driven member driven by a telescopic drive of an electromechanical conversion element, characterized in that, The friction part includes a helical torsion friction spring, a moving body, and a friction drive shaft. The coil inner diameter of the helical torsion friction spring is smaller than the outer diameter of the friction drive shaft, the helical torsion friction spring is pressed into the friction drive shaft and is frictionally embedded with the friction drive shaft, and the coil inner wall of the helical torsion friction spring and the outer circumferential surface of the friction drive shaft form a circumferential continuous friction of at least one full circle. The helical torsion friction spring is fixed to the moving body or the helical torsion friction spring is the moving body, the moving body moves along the axial direction of the friction drive shaft, the moving body is linked with the driven part, and the movement of the moving body drives the movement of the driven part.

2. The driving device for a camera according to claim 1, wherein the electromechanical conversion element is arranged in a manner in which the extension and contraction direction thereof is parallel to the optical axis of the lens.

3. The driving device for a camera according to claim 2, wherein the driven part has an embedded portion that restricts the position of the helical torsion friction spring, and the helical torsion friction spring is fixed in the axial and circumferential directions by the embedding of the embedded portion, so that the helical spring moves to drive the movement of the driven part having the embedded portion.

4. The driving device for a camera according to claim 1, wherein the electromechanical conversion element is arranged in a manner in which the extension and contraction direction thereof is non-parallel to the optical axis of the lens, including a perpendicular manner, and the driving device has a conversion structure that converts the movement in the extension and contraction direction of the electromechanical conversion element into the movement in the optical axis direction of the lens.

5. The driving device for a camera according to any one of claims 1 to 4, characterized in that, The moving body covers the helical torsion friction spring embedded in the friction drive shaft, and the arm portions at both ends of the helical torsion friction spring are in elastic contact with the inclined surface of the moving body.

6. The driving device for a camera according to claim 4, wherein The conversion structure is a cam portion.

7. The driving device for a camera according to claim 6, wherein The cam portion includes a cam driven portion and a corresponding driving portion, or a cam driving portion and a corresponding driven portion, and the inclined surface that moves synchronously with the moving body or the lens frame serves as the cam driving portion or the cam driven portion.

8. The driving device for a camera according to claim 7, wherein The cam driven portion and the driving portion are pushed against each other by the force storage of an energizing spring.

9. The driving device for a camera according to claim 7, wherein The driven portion and the cam driving portion are pushed against each other by the force storage of an energizing spring.

10. The driving device for a camera according to claim 7, wherein The cam driving portion has an inclined surface that forms a certain angle with respect to the extension and contraction direction of the electromechanical conversion element or the optical axis direction of the lens, and drives the lens or the lens frame by acting on the driven portion that is integrally formed with the lens or the frame body through the cam inclined surface.

11. The driving device for a camera according to claim 10, wherein The driven portion forms a mutual force with the cam driving portion by the force of an energizing spring, and the straight arm of the energizing spring is parallel to the inclined surface.

12. The driving device for a camera according to claim 11, wherein The energizing spring is a torsion spring of the wire-wound helical torsion spring type.

13. The driving device for a camera according to claim 7, wherein The movement in the extension and contraction direction of the electromechanical conversion element is converted into the movement in the optical axis direction of the lens, and the moving body having the driving portion is frictionally combined on the friction drive shaft.

14. The driving device for a camera according to claim 13, wherein The transformation structure has a cam-driven portion formed with an inclined surface portion integrally formed with a lens frame and at an angle with respect to a telescopic direction of the electromechanical transformation element or a lens optical axis direction, the driving portion on the moving body and the cam-driven portion being in contact with each other, and the cam-driven portion being driven by the driving portion pushing against it to drive the lens.

15. The driving device for a camera according to claim 14, wherein The cam-driven portion and the driving portion are mutually energized and pushed against by an energizing spring, and an energizing portion of the energizing spring is parallel to the inclined surface of the cam-driven portion.

16. The driving device for a camera according to claim 1, wherein The electromechanical transformation element is a laminated piezoelectric element.

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