Piezoelectric Actuator and Its Camera Module

Abstract

The present invention provides a piezoelectric actuator and a camera module. By arranging a driving rod between two piezoelectric elements and connecting the piezoelectric elements and the driving rod with a connecting structure at the top, the height of the piezoelectric actuator is reduced, the driving ability is improved, the driving stroke is increased under the same module height, and the module height is reduced under the same driving stroke, thereby taking into account the product requirements of a larger driving stroke and a lower module height, improving the imaging quality. Moreover, under the same driving signal, the piezoelectric actuator can achieve a larger single-step stroke and higher focusing efficiency, thus improving the overall performance of the camera module.

Description

Technical Field

[0001] The present invention relates to a piezoelectric actuator and a camera module thereof. Background Art

[0002] Existing camera modules generally include a lens assembly and an actuator for driving the lens assembly to move along the optical axis. With the rapid development of the portable electronic device industry, people's requirements for the imaging effect of camera modules are gradually increasing. Currently, the shooting quality is mainly improved by increasing the optical sizes of the lens and the image sensor. The increase in the lens size poses a challenge to the driving ability of the actuator. On the other hand, the existing voice coil actuators and shape memory alloy actuators have a short movable stroke and poor macro shooting effects. On the other hand, the lens of the existing camera module cannot perform telescopic movement over a large distance outside the mobile phone. To meet these requirements, the use of piezoelectric actuators is a major trend in the industry development.

[0003] However, existing piezoelectric actuators generally include a piezoelectric element and a driving rod disposed above the piezoelectric element. When the piezoelectric element vibrates at a high frequency, it will drive the driving rod to make high-frequency reciprocating movements up and down together. The heights of the piezoelectric element and the driving rod determine the driving ability and the driving stroke. Therefore, if a large stroke is to be achieved, it is very difficult to further reduce the height of the piezoelectric actuator. Limited by the overall height of the portable electronic device, it is difficult to balance the product requirements of a large driving stroke and a lower module height. Summary of the Invention

[0004] The purpose of the present invention is to provide a piezoelectric actuator and a camera module thereof, to reduce the height of the piezoelectric actuator, improve the driving ability, balance the product requirements of a large driving stroke and a lower module height, improve the imaging quality, and improve the overall performance of the camera module.

[0005] Based on the above considerations, the present invention provides a piezoelectric actuator, including: two piezoelectric elements; a driving rod located between the two piezoelectric elements; a connection structure for connecting the piezoelectric element and the driving rod; wherein, the connection structure is a rigid plate; the connection structure is located at the tops of the piezoelectric element and the driving rod.

[0006] The present invention also provides a camera module, including the piezoelectric actuator having the above technical features, and the piezoelectric actuator is used to drive the lens assembly to move along the optical axis.

[0007] Preferably, an elastic support structure is provided on the other side opposite to the two piezoelectric elements, and the elastic support structure abuts against the lens assembly through a ball to ensure the optical axis stability of the lens assembly.

[0008] Preferably, an elastic buckle fixedly connected to the lens assembly is in frictional contact with the driving rod to drive the lens assembly to move along the optical axis.

[0009] Preferably, a position detection element disposed corresponding to the piezoelectric actuator is configured to feedback position information of a corresponding part of the lens assembly.

[0010] Preferably, the position detection element is a Hall sensor or a capacitive grating sensor.

[0011] For the piezoelectric actuator and the camera module of the present invention, by disposing the driving rod between two piezoelectric elements and connecting the piezoelectric elements and the driving rod with a connecting structure located at the top, the height of the piezoelectric actuator is reduced, the driving ability is improved, the driving stroke is increased under the same module height, and the module height is reduced under the same driving stroke, thereby taking into account the product requirements of a larger driving stroke and a lower module height, improving the imaging quality, and under the same driving signal, the single-step stroke of the piezoelectric actuator can be made larger and the focusing efficiency can be higher, thus improving the overall performance of the camera module. Description of the Drawings

[0012] Other features, objects, and advantages of the present invention will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0013] Figure 1 、 Figure 2 is a schematic structural diagram of the camera module of the present invention.

[0014] In the figures, throughout the different views, the same or similar reference numerals denote the same or similar devices (modules) or steps. Detailed Description of the Embodiments

[0015] The present invention provides a piezoelectric actuator and a camera module thereof. By disposing the driving rod between two piezoelectric elements and connecting the piezoelectric elements and the driving rod with a connecting structure located at the top, the height of the piezoelectric actuator is reduced, the driving ability is improved, the driving stroke is increased under the same module height, and the module height is reduced under the same driving stroke, thereby taking into account the product requirements of a larger driving stroke and a lower module height, improving the imaging quality, and under the same driving signal, the single-step stroke of the piezoelectric actuator can be made larger and the focusing efficiency can be higher, thus improving the overall performance of the camera module.

[0016] In the following detailed description of the preferred embodiments, reference will be made to the accompanying drawings that form a part of the present invention. The accompanying drawings illustrate specific embodiments that can implement the present invention by way of example. The exemplary embodiments are not intended to exhaust all embodiments according to the present invention. It can be understood that other embodiments can be utilized without departing from the scope of the present invention, and structural or logical modifications can also be made. Therefore, the following detailed description is not restrictive, and the scope of the present invention is defined by the appended claims.

[0017] The present invention will be described in detail below in conjunction with specific embodiments.

[0018] As Figure 1 , Figure 2 shown, the camera module of the present invention includes a lens assembly 1 and a piezoelectric actuator 2 for driving the lens assembly 1 to move along the optical axis direction. The piezoelectric actuator 2 includes two piezoelectric elements 21; a driving rod 22 located between the two piezoelectric elements 21; and a connection structure 23 for connecting the piezoelectric element 21 and the driving rod 22. Among them, the connection structure 23 is a rigid plate; the connection structure 23 is located at the tops of the piezoelectric element 21 and the driving rod 22.

[0019] Compared with the piezoelectric actuator of the prior art, the driving rod 22 is transferred from above the piezoelectric element 21 to between the two piezoelectric elements 21, thereby effectively reducing the overall height of the piezoelectric actuator 2. Therefore, there is more space to increase the height of the piezoelectric element 21 or the driving rod 22, thereby improving the driving ability of the piezoelectric actuator 2. Therefore, the driving stroke can be increased under the same module height, and the module height can be effectively reduced under the same driving stroke, so as to meet the product requirements of a larger driving stroke and a lower module height, and improve the imaging quality. Due to the improvement of the driving ability, under the same driving signal, a larger single-step stroke and higher focusing efficiency of the piezoelectric actuator can be achieved, thereby improving the overall performance of the camera module.

[0020] Specifically, the shape of the driving rod 22 can be set as needed. Here, it is shown as a cylindrical shape as an example rather than a limitation. When the piezoelectric elements 21 on both sides vibrate at high frequency, the vibration will be transferred to the middle driving rod 22 through the rigid connection structure 23 at the top, so as to drive the driving rod 22 to reciprocate up and down at high frequency. The driving rod 22 is in frictional contact with an elastic buckle 4 in the tangential direction, and the other end of the elastic buckle 4 is fixedly connected to the lens assembly 1. The driving rod 22 and the elastic buckle 4 can provide a driving force for the lens assembly 1 to move along the optical axis under the action of friction and inertia, so that the lens assembly 1 moves up and down smoothly in the optical axis direction.

[0021] In Figure 1 , Figure 2In the preferred embodiment shown, a piezoelectric actuator 2 is provided on one side of the lens assembly 1, and an elastic support structure, shown here as a flat spring 6, is provided on the other side opposite to the two piezoelectric elements 21 of the piezoelectric actuator 2. Two balls 5 are provided between the flat spring 6 and the lens assembly 1. The two balls 5 are respectively located at both ends of the flat spring 6. The flat spring 6 abuts against the lens assembly 1 through the balls 5, thereby applying an elastic pressure to the lens assembly 1. On the one hand, this can ensure that the center of gravity of the lens assembly 1 moves along a fixed axis in the optical axis direction, thus ensuring the optical axis stability of the lens assembly 1; on the other hand, the elastic pressure on the opposite side can also ensure better contact between the driving rod 22 and the elastic buckle 4 in the normal direction, thereby providing effective frictional force for the two.

[0022] In other preferred embodiments not shown, the same piezoelectric actuator 2 can also be symmetrically provided on the other side of the lens assembly 1. In this case, there is no need to provide the elastic support structure 6 and the balls 5.

[0023] In addition, a position detection element 3 (such as a Hall sensor or a capacitive grating sensor) can also be provided at a position corresponding to the piezoelectric actuator 2, shown here as between the two piezoelectric elements 21. The position detection element 3 is used to feedback the position information of the corresponding part of the lens assembly 1 to the piezoelectric actuator 2 to determine the movement distance of the lens assembly 1.

[0024] In summary, for the piezoelectric actuator and the camera module of the present invention, by arranging the driving rod between two piezoelectric elements and connecting the piezoelectric element and the driving rod with the connecting structure at the top, the height of the piezoelectric actuator is reduced, the driving ability is improved, the driving stroke is increased under the same module height, and the module height is reduced under the same driving stroke, thereby taking into account the product requirements of a larger driving stroke and a lower module height, improving the imaging quality, and moreover, under the same driving signal, the single-step stroke of the piezoelectric actuator can be made larger and the focusing efficiency can be higher, thus improving the overall performance of the camera module.

[0025] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, in any case, the embodiments should be regarded as exemplary and non-limiting. In addition, obviously, the word "including" does not exclude other elements and steps, and the term "one" does not exclude a plurality. A plurality of elements stated in the device claims can also be implemented by one element. The words first, second, etc. are used to denote names and do not denote any particular order.

Claims

1. A piezoelectric actuator, characterized in that, comprising: two piezoelectric elements; a driving rod located between the two piezoelectric elements; a connection structure for connecting the piezoelectric element and the driving rod; the connection structure is located at the top of the piezoelectric element and the driving rod; the extending directions of the driving rod and the piezoelectric element are consistent with the optical axis; wherein, when the two piezoelectric elements vibrate at high frequency, they will transfer the vibration to the middle driving rod through the connection structure at the top, so as to drive the driving rod to reciprocate up and down at high frequency; the connection structure is a rigid plate.

2. A camera module, characterized in that, comprising the piezoelectric actuator as described in claim 1, and the piezoelectric actuator is used to drive the lens assembly to move along the optical axis direction.

3. The camera module as described in claim 2, characterized in that, an elastic support structure is arranged on the other side opposite to the two piezoelectric elements, and the elastic support structure abuts against the lens assembly through a ball to ensure the optical axis stability of the lens assembly.

4. The camera module as described in claim 2, characterized in that, an elastic buckle fixedly connected to the lens assembly is in frictional contact with the driving rod to drive the lens assembly to move along the optical axis direction.

5. The camera module as described in claim 2, characterized in that, a position detection element arranged corresponding to the piezoelectric actuator is used to feedback the position information of the corresponding part of the lens assembly.

6. The camera module as described in claim 5, characterized in that, the position detection element is a Hall sensor or a capacitive grating sensor.

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