Mobile terminal

Abstract

A mobile terminal (100), comprising a middle frame (110), and a primary screen and a secondary screen (120) located on the middle frame (110), wherein the secondary screen (120) is folded in different states and is arranged on the back of the primary screen or arranged side by side on one side of the primary screen. The mobile terminal further comprises at least one piezoelectric actuator (130) fixed in the middle frame (110), wherein the middle frame (110) has a bottom wall (111) and a side wall (112) bent and extending from the bottom wall (111) to form an accommodating space with the bottom wall (111), one side of the piezoelectric actuator (130) is fixedly connected to the bottom wall (111), the other side of the piezoelectric actuator is fixedly connected to the secondary screen (120), and the piezoelectric actuator (130) converts transverse deformation of the piezoelectric actuator into longitudinal driving, so as to drive the secondary screen (120) to vibrate to produce sound and provide tactile feedback for the secondary screen (120). The piezoelectric actuator (130) can be used as a supplement to a receiver or a loudspeaker, and the secondary screen (120) vibrates to produce sound without a hole design, thereby improving the overall firmness of the mobile terminal (100), and facilitating waterproofing and dustproofing; and by means of the piezoelectric actuator (130), the secondary screen (120) is driven to vibrate within a suitable frequency range, thereby enabling tactile feedback for the secondary screen (120) on a palm or a finger in contact with the secondary screen, and enriching and enhancing the experience of a user using the mobile terminal (100).

Description

mobile terminals Technical Field

[0001] The embodiments of the present disclosure belong to the technical field of sound-to-electricity conversion, and specifically relate to a mobile terminal. Background Art

[0002] Current smartphones often feature a second screen (a secondary screen) on the back for convenient information display and operation. This is especially true with the rise of foldable phones, where a second screen (an external screen) is often included to facilitate user access to information and interface operations when the foldable main screen is not unfolded. However, current smartphone secondary screens only provide display functions and lack haptic feedback or on-screen sound, resulting in a poor user experience.

[0003] In view of the above problems, it is necessary to propose a mobile terminal with a reasonable design that can effectively improve the above problems. Summary of the Invention

[0004] The embodiments of the present disclosure aim to solve at least one of the technical problems existing in the prior art and provide a mobile terminal.

[0005] An embodiment of the present disclosure provides a mobile terminal, which includes a middle frame, a main screen and a sub-screen located on the middle frame, the sub-screen being folded and arranged on the back of the main screen or arranged side by side with the main screen in different states, the mobile terminal also including at least one piezoelectric actuator fixed in the middle frame, the middle frame including a bottom wall and a side wall bent from the bottom wall and extending to form a receiving space with the bottom wall, one side of the piezoelectric actuator being fixedly connected to the bottom wall, and the other side being fixedly connected to the sub-screen, the piezoelectric actuator converting its lateral deformation into a longitudinal drive to drive the sub-screen to vibrate and make sound and provide tactile feedback for the sub-screen.

[0006] Optionally, the piezoelectric actuator is used to detect pressing force information of the secondary screen.

[0007] Optionally, the number of the piezoelectric actuator is one, the one piezoelectric actuator is located in the central area of ​​the secondary screen, and its center of gravity is located on the midline of the secondary screen; or,

[0008] There are multiple piezoelectric actuators, and the multiple piezoelectric actuators are located in the edge area of ​​the sub-screen and are symmetrically arranged with the center line of the sub-screen as the center.

[0009] Optionally, the piezoelectric actuator includes a piezoelectric body and two sets of elastic supports provided at the ends of the piezoelectric body along the extension and contraction direction thereof;

[0010] Each group of the elastic supports comprises a first elastic sheet and a second elastic sheet spaced apart along the thickness direction of the piezoelectric body;

[0011] The first end of the first elastic piece is fixed to the first surface of the piezoelectric body, and the second end of the first elastic piece is fixedly connected to the auxiliary screen;

[0012] The first end of the second elastic piece is fixed to the second surface of the piezoelectric body, and the second end of the second elastic piece is fixedly connected to the middle frame.

[0013] Optionally, it further includes a first support plate and a second support plate;

[0014] The first support plate is arranged between the piezoelectric actuator and the sub-screen, and the second support plate is arranged between the piezoelectric actuator and the middle frame.

[0015] Optionally, the piezoelectric actuator includes a piezoelectric body and a first amplifying unit and a second amplifying unit supported and fixed on both sides of the piezoelectric body along the thickness thereof;

[0016] Two ends of the first amplifying unit are fixed to the first surface of the piezoelectric body, and a middle portion of the first amplifying unit extends in a direction away from the first surface and is connected to the auxiliary screen;

[0017] Two ends of the second amplifying unit are fixed to the second surface of the piezoelectric body, and a middle portion of the second amplifying unit extends in a direction away from the second surface and is connected to the middle frame.

[0018] Optionally, the first amplifying unit includes a first elastic portion and a first connecting portion extending horizontally from the first elastic portion, wherein a side of the first elastic portion close to the first surface is fixedly connected to the first surface, and a side of the first elastic portion away from the first surface is fixedly connected to the auxiliary screen;

[0019] The second amplifying unit includes a second elastic portion and a second connecting portion extending horizontally from the second elastic portion. The side of the second elastic portion close to the second surface is fixedly connected to the second surface, and the side of the second elastic portion away from the second surface is fixedly connected to the middle frame.

[0020] Optionally, a flexible connector is further included, and the secondary screen is flexibly connected to the middle frame through the flexible connector.

[0021] Optionally, a side of the flexible connector facing the interior of the middle frame is recessed to form a first recessed portion, and a size of the first recessed portion gradually decreases in a direction away from the receiving space; and / or,

[0022] A side of the flexible connector facing the auxiliary screen is recessed to form a second recessed portion, and a size of the second recessed portion gradually decreases in a direction away from the auxiliary screen.

[0023] The mobile terminal of the disclosed embodiment includes at least one piezoelectric actuator fixed within a middle frame. One side of the piezoelectric actuator is fixedly connected to the bottom wall of the middle frame, and the other side is fixedly connected to the secondary screen. The piezoelectric actuator converts its lateral deformation into longitudinal drive to drive the secondary screen to vibrate and produce sound, which can serve as a supplement to the receiver or speaker. The vibration and sound of the secondary screen does not require a hole design, thereby improving the overall robustness of the mobile terminal and facilitating waterproof and dustproofing. When the mobile terminal is a foldable screen phone, calls can be answered without unfolding the foldable screen, providing a high user experience. The piezoelectric actuator drives the secondary screen to vibrate within a suitable frequency range, so that the secondary screen generates tactile feedback in response to contact with the palm or finger, enriching and enhancing the user experience of the mobile terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG1 is a schematic diagram of an assembly of a mobile terminal according to an embodiment of the present disclosure;

[0025] FIG2 is a schematic diagram of the assembly of the middle frame, the auxiliary screen, and the piezoelectric actuator according to an embodiment of the present disclosure;

[0026] FIG3 is a cross-sectional view of the frame, the auxiliary screen, and the piezoelectric actuator in the cross-sectional view of a portion of the mobile terminal taken along the AA direction in FIG2 ;

[0027] FIG4 is a perspective exploded view of the middle frame, the auxiliary screen, and the piezoelectric actuator according to an embodiment of the present disclosure;

[0028] FIG5 is a schematic structural diagram of a piezoelectric actuator in a first embodiment of the present disclosure;

[0029] FIG6 is a schematic structural diagram of a piezoelectric actuator in a second embodiment of the present disclosure;

[0030] FIG7 is a schematic structural diagram of another piezoelectric actuator in the second embodiment of the present disclosure;

[0031] FIG8 is a schematic diagram of the distribution of piezoelectric actuators on the secondary screen in the second embodiment of the present disclosure;

[0032] FIG9 is a schematic diagram showing the distribution of piezoelectric actuators on the secondary screen in the second embodiment of the present disclosure;

[0033] FIG10 is a graph showing acceleration-frequency response of vibration of the secondary screen according to an embodiment of the present disclosure;

[0034] FIG11 is a schematic structural diagram of the first recessed portion in the flexible connector according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the technical solutions of the embodiments of the present disclosure, the embodiments of the present disclosure are further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0036] As shown in Figures 1 to 3, an embodiment of the present disclosure provides a mobile terminal 100, which includes a middle frame 110, a main screen and a sub-screen 120 located on the middle frame 110. The sub-screen 120 is folded and arranged on the back of the main screen or arranged side by side on the main screen in different states. The mobile terminal 100 also includes at least one piezoelectric actuator 130 fixed in the middle frame 110. The middle frame 110 includes a bottom wall 111 and a side wall 112 bent from the bottom wall 111 and extending to form a receiving space with the bottom wall 111. One side of the piezoelectric actuator 130 is fixedly connected to the bottom wall 111, and the other side of the piezoelectric actuator 130 is fixedly connected to the sub-screen 120. The piezoelectric actuator 130 converts its lateral deformation into longitudinal drive to drive the sub-screen 120 to vibrate and make sound and provide tactile feedback for the sub-screen 120.

[0037] It should be noted that the mobile terminal 100 can be a smart candy bar phone or a foldable screen phone, etc. If the mobile terminal 100 is a smart candy bar phone, the secondary screen 120 is set on the back side of the smart candy bar phone. If the mobile terminal 100 is a foldable screen phone, the secondary screen 120 is set on the outside of the foldable screen phone. In this embodiment, the mobile terminal 100 is described as a foldable screen phone.

[0038] The mobile terminal of the disclosed embodiment includes at least one piezoelectric actuator fixed within a middle frame. One side of the piezoelectric actuator is fixedly connected to the bottom wall of the middle frame, and the other side is fixedly connected to the secondary screen. The piezoelectric actuator converts its lateral deformation into longitudinal drive to drive the secondary screen to vibrate and produce sound, which can serve as a supplement to the receiver or speaker. The vibration and sound of the secondary screen does not require a hole design, thereby improving the overall robustness of the mobile terminal and facilitating waterproof and dustproofing. When the mobile terminal is a foldable screen phone, calls can be answered without unfolding the foldable screen, providing a high user experience. The piezoelectric actuator drives the secondary screen to vibrate within a suitable frequency range, so that the secondary screen generates tactile feedback in response to contact with the palm or finger, enriching and enhancing the user experience of the mobile terminal.

[0039] Exemplarily, the piezoelectric actuator 130 is used to detect the pressing force information of the sub-screen 120 .

[0040] In the mobile terminal of the embodiment of the present disclosure, the piezoelectric actuator can detect the pressing force information of the secondary screen and has the function of pressure sensing. When the secondary screen is pressed by external force, it can protect itself to avoid excessive vibration that may damage the secondary screen, and can be used as a pressure button to replace some power buttons or volume adjustment functions.

[0041] For example, as shown in FIG. 3 , the number of the piezoelectric actuator 130 may be one, and the piezoelectric actuator 130 is located in the central area of ​​the sub-screen 120 , and its center of gravity is located on the midline of the sub-screen 120 .

[0042] As shown in Figures 8 and 9, there can be multiple piezoelectric actuators 130, which are located in the edge area of ​​the secondary screen 120 and are symmetrically arranged around the center line of the secondary screen 120. Specifically, in this embodiment, the example of two piezoelectric actuators 130 is used for description.

[0043] In the first embodiment, the piezoelectric actuator 130 can adopt a separate inverted arch support structure piezoelectric actuator as shown in Figures 3 to 5, which is located in the central area of ​​the sub-screen 120 and its center of gravity is located on the midline of the sub-screen 120.

[0044] Specifically, the piezoelectric actuator 130 includes a piezoelectric body 131 and two sets of elastic supports 132 disposed at the ends of the piezoelectric body 131 along its extension direction. The elastic supports 132 are symmetrically distributed. In this embodiment, the piezoelectric body 131 can be a piezoelectric ceramic layer, which is used to detect touch pressure signals from the secondary screen.

[0045] As shown in FIG5 , each set of elastic supports 132 includes a first elastic piece 132a and a second elastic piece 132b spaced apart along the thickness of the piezoelectric body 131. The first end of the first elastic piece 132a is fixed to the first surface of the piezoelectric body 131, and the second end of the first elastic piece 132a is fixedly connected to the auxiliary screen 120. The second end of the first elastic piece 132a extends in the direction of expansion and contraction of the piezoelectric body 131. In other words, as shown in FIG5 , the second end of the first elastic piece 132a extends horizontally.

[0046] The first end of the second elastic piece 132b is fixed to the second surface of the piezoelectric body 131, and the second end of the second elastic piece 132b is fixedly connected to the middle frame 110. The second end of the second elastic piece 132b extends along the expansion and contraction direction of the piezoelectric body 131. In other words, as shown in Figure 5, the second end of the second elastic piece 132b extends horizontally.

[0047] In addition, as shown in FIG3 and FIG5 , the first elastic piece 132 a and the second elastic piece 132 b each have an angle with the plane where the piezoelectric body 131 is located, and the angle is less than 45°.

[0048] In this embodiment, the piezoelectric actuator 130 adopts the d31 vibration mode, and the lateral expansion and contraction movement of the piezoelectric body 131 is converted into vertical longitudinal vibration through the elastic supports 132 at both ends. Under the premise that the elastic supports 132 are symmetrical, it will push the sub-screen 120 as a whole to move along its thickness direction, thereby pushing the air to make sound.

[0049] When the secondary screen 120 is in the sound-generating state, the elastic supports 132 at both ends of the piezoelectric body 131 can reduce the natural frequency of the piezoelectric body 131 (piezoelectric ceramic layer), improve the frequency response performance, and increase the sound pressure level of the mid-bass. Through the vibration transmission effect of the elastic support 132, high-order vibration modes can be suppressed, thereby improving the distortion of the screen sound and improving the sound restoration.

[0050] In the tactile feedback state, the spring bracket 132 can reduce the resonant frequency, support the suspension of the piezoelectric body 131 (piezoelectric ceramic layer), and transmit the longitudinal pressure to the lateral force of the piezoelectric body 131, thereby enabling the piezoelectric body 131 to have a pressure detection function.

[0051] As shown in Figures 3 to 5, in the first embodiment, when the piezoelectric actuator 130 adopts the piezoelectric actuator with an inverted arch support structure as shown in Figure 5, the mobile terminal 100 further includes a first support plate 141 and a second support plate 142. The first support plate 141 is disposed between the piezoelectric actuator 130 and the secondary screen 120, and the second support plate 142 is disposed between the piezoelectric actuator 130 and the middle frame 110. The first support plate 141 and the second support plate 142 support the piezoelectric actuator 130.

[0052] Exemplarily, as shown in FIG6 and FIG7 , in the second embodiment, the piezoelectric actuator 130 includes a piezoelectric body 133 and a first amplifying unit 134 and a second amplifying unit 135 supported and fixed to both sides of the piezoelectric body 133 along the thickness thereof.

[0053] The first amplifying unit 134 has two ends fixed to the first surface of the piezoelectric body 133, and its middle portion extends away from the first surface of the piezoelectric body 133 and is connected to the auxiliary screen 120. The second amplifying unit 135 has two ends fixed to the second surface of the piezoelectric body 133, and its middle portion extends away from the second surface of the piezoelectric body 133 and is connected to the middle frame 110. In other words, as shown in Figure 6, the first amplifying unit 134 and the second amplifying unit 135 are symmetrically arranged about the piezoelectric body 133.

[0054] Specifically, when subjected to an external voltage, the piezoelectric body 133 expands or contracts in a first direction parallel to the plane of the piezoelectric body 133. Simultaneously, the first and second amplifying units 134, 135 expand or contract in a second direction, with the first and second directions being perpendicular to each other. The expansion or contraction of the first and second amplifying units 134, 135 in the second direction can drive the secondary screen 120 to vibrate along its thickness. The piezoelectric body 133 can be a piezoelectric ceramic layer, used to detect touch pressure signals from the secondary screen.

[0055] As shown in FIG8 and FIG9 , in the second embodiment, there are two piezoelectric actuators 130 . The two piezoelectric actuators 130 are located at the edge of the sub-screen 120 and are symmetrically arranged around the center line of the sub-screen 120 .

[0056] As shown in Figure 8 , the two piezoelectric actuators 130 can be symmetrically distributed along their lengths, aligned with the length of the secondary screen 120. As shown in Figure 9 , the two piezoelectric actuators 130 can be symmetrically distributed along their lengths, aligned with the width of the secondary screen 120. In this embodiment, there are no specific requirements for the specific distribution of the two piezoelectric actuators 130; as long as they are symmetrically arranged around the midline of the secondary screen 120, the distribution can be selected based on actual needs.

[0057] Specifically, in the second embodiment, the piezoelectric actuator 130 can be implemented as two diamond-shaped piezoelectric actuators with amplification mechanisms, as shown in Figure 6. These two piezoelectric actuators are symmetrically arranged in pairs and utilize driving signals of the same frequency and phase to cause the auxiliary screen 120 to produce the same displacement at both support points, thereby causing the auxiliary screen 120 to move like a piston along its thickness. These two piezoelectric actuators can also integrate multiple functions, or independently implement functions such as screen sound generation, pressure sensing, and vibration feedback.

[0058] Further, as shown in Figure 7, in the third embodiment, the first amplifying unit 134 includes a first elastic portion 134a and a first connecting portion 134b extending horizontally from the first elastic portion 134a, and the side of the first elastic portion 134a close to the first surface of the piezoelectric body 133 is fixedly connected to the first surface of the piezoelectric body 133, and the side of the first elastic portion 134a away from the first surface is fixedly connected to the auxiliary screen 120.

[0059] The second amplifying unit 135 includes a second elastic portion 135a and a second connecting portion 135b extending horizontally from the second elastic portion 135a. The side of the second elastic portion 135a close to the second surface of the piezoelectric body 133 is fixedly connected to the second surface of the piezoelectric body 133, and the side of the second elastic portion 135a away from the second surface of the piezoelectric body 133 is fixedly connected to the middle frame 120.

[0060] That is, the first elastic portion 134 a and the second elastic portion 135 a are both rhombus-shaped and symmetrically distributed with respect to the piezoelectric body 133 , and the first connecting portion 134 b and the second connecting portion 135 b are symmetrically distributed with respect to the piezoelectric body 133 .

[0061] More specifically, in the third embodiment, the piezoelectric actuator 130 can be a two-layer piezoelectric device with a dual-layer amplification mechanism, as shown in Figure 7 . The two dual-layer piezoelectric devices are also symmetrically arranged in pairs. This piezoelectric actuator overcomes the problem of the piezoelectric body responding to small displacement or high applied voltage, thereby achieving a compact piezoelectric vibrator with fast response, adjustable resonant frequency, wide operating frequency range, and high energy conversion efficiency.

[0062] Existing foldable screen mobile phones have smaller screens and higher equivalent stiffness. Relying on screen bending and deformation to produce sound results in excessively high low frequencies and poor low- and mid-frequency effects. The mobile terminal 100 in this embodiment uses two diamond-shaped piezoelectric amplification devices to further enhance low-frequency effects and increase vibration displacement.

[0063] As shown in FIG10 , a vibration acceleration-frequency test is performed on the auxiliary screen 120 , and the vibration frequency of the auxiliary screen 120 has a very good effect.

[0064] Exemplarily, as shown in FIG. 3 and FIG. 4 , the mobile terminal 100 further includes a flexible connector 150 , and the sub-screen 120 is flexibly connected to the middle frame 110 via the flexible connector 150 .

[0065] In the embodiment of the present disclosure, the secondary screen is flexibly connected to the middle frame through a soft connector. On the one hand, the connection stiffness between the middle frame and the secondary screen is reduced, and the soft connector maintains the sealing between the middle frame and the secondary screen. On the other hand, the soft connector provides movement space for the vibration of the secondary screen.

[0066] Exemplarily, the flexible connector 150 covers at least a portion of the secondary screen 120. As shown in FIG4 , in this embodiment, the flexible connector 150 is a sealing ring that covers a portion of the secondary screen 120. Of course, the flexible connector 150 can cover the entire secondary screen 120, and the extent to which the flexible connector 150 covers the secondary screen 120 can be selected based on actual needs.

[0067] It should be noted that the flexible connector 150 can be made of cushioning materials such as rubber, foam, resin, latex, etc., and can be selected according to actual needs.

[0068] It should be further explained that the flexible connection between the sub-screen 120 and the middle frame 110 can also be other forms, such as springs and flexible cloth seals, which are more conducive to setting the stiffness of the connection, thereby adjusting the frequency of sound or vibration of the sub-screen 120.

[0069] For example, as shown in FIG11 , the side of the flexible connector 150 facing the interior of the middle frame 110 is recessed to form a first recessed portion 151, and the first recessed portion 151 gradually decreases in size as it moves away from the receiving space of the middle frame 110. Alternatively, the side of the flexible connector 150 facing the auxiliary screen 120 is recessed to form a second recessed portion, and the second recessed portion gradually decreases in size as it moves away from the auxiliary screen.

[0070] In this embodiment, as shown in FIG11 , the first recess 151 and the second recess have the same structure and can both be stepped. The flexible connector 150 can have the first recess 151 formed only on the side facing the interior of the middle frame 110, or the second recess formed only on the side facing the auxiliary screen 120. Of course, the flexible connector 150 can have both the first recess 151 and the second recess, and the choice can be made based on actual needs, which is not specifically limited in this embodiment.

[0071] In this embodiment, by forming the first recessed portion and / or the second recessed portion on the flexible connector, the middle frame and the auxiliary screen can be better accommodated, so as to better seal the middle frame and the auxiliary screen.

[0072] The mobile terminal in the embodiments of the present disclosure can be applied to the following scenarios:

[0073] 1) Secondary screen pressure sensing and sound generation: Because the secondary screen requires overall vibration, displaying content can be affected. Therefore, content display on the secondary screen should be disabled during calls. Pressure sensing can determine the status of the secondary screen or mobile terminal, preventing damage to the screen due to excessive force, further protecting the secondary screen. It can also determine whether a finger is pressing or close to the body to trigger corresponding actions.

[0074] 2) Pressure buttons and vibration feedback in gaming scenarios: The secondary screen can be designed as an additional touch button, providing a wider range of operational experiences. For example, it can provide tactile feedback when a finger or palm touches it. When gaming, the screen can be used as a pressure button, giving the main screen more display space and providing different operating force levels.

[0075] It is understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the embodiments of the present disclosure, but the embodiments of the present disclosure are not limited thereto. Those skilled in the art may make various modifications and improvements without departing from the spirit and essence of the embodiments of the present disclosure, and such modifications and improvements are also considered to be within the scope of protection of the embodiments of the present disclosure.

Claims

1. A mobile terminal, comprising a middle frame, a main screen and a secondary screen located on the middle frame, wherein the secondary screen is folded and disposed on the back of the main screen or juxtaposed on one side of the main screen in different states. Characterized in that: The mobile terminal further includes at least one piezoelectric actuator fixed within the middle frame. The middle frame includes a bottom wall and side walls bent and extending from the bottom wall to form a receiving space therewith. One side of the piezoelectric actuator is fixedly connected to the bottom wall, and the other side is fixedly connected to the secondary screen. The piezoelectric actuator converts its lateral deformation into longitudinal driving to drive the secondary screen to vibrate and generate sound and provide haptic feedback for the secondary screen.

2. The mobile terminal according to claim 1, Characterized in that, The piezoelectric actuator is used to detect the pressing force information of the secondary screen.

3. The mobile terminal according to claim 1, Characterized in that, The number of the piezoelectric actuators is one, and this one piezoelectric actuator is located in the central area of the secondary screen, and its center of gravity is located on the center line of the secondary screen; or, The number of the piezoelectric actuators is multiple, and the multiple piezoelectric actuators are located in the edge area of the secondary screen and are symmetrically arranged with the center line of the secondary screen as the center.

4. The mobile terminal according to any one of claims 1 to 3, Characterized in that, The piezoelectric actuator includes a piezoelectric body and two sets of elastic brackets arranged at the ends of the piezoelectric body along its telescopic direction; Each set of the elastic brackets includes a first elastic sheet and a second elastic sheet spaced along the thickness direction of the piezoelectric body; The first end of the first elastic sheet is fixed to the first surface of the piezoelectric body, and the second end of the first elastic sheet is fixedly connected to the secondary screen; The first end of the second elastic sheet is fixed to the second surface of the piezoelectric body, and the second end of the second elastic sheet is fixedly connected to the middle frame.

5. The mobile terminal according to claim 4, Characterized in that, It further includes a first support plate and a second support plate; The first support plate is disposed between the piezoelectric actuator and the secondary screen, and the second support plate is disposed between the piezoelectric actuator and the middle frame.

6. The mobile terminal according to any one of claims 1 to 3, Characterized in that, The piezoelectric actuator includes a piezoelectric body and a first amplification unit and a second amplification unit supported and fixed on both sides of the piezoelectric body along its thickness; Both ends of the first amplification unit are fixed to the first surface of the piezoelectric body, and the middle part of the first amplification unit extends in a direction away from the first surface and is connected to the secondary screen; Both ends of the second amplification unit are fixed to the second surface of the piezoelectric body, and the middle part of the second amplification unit extends in a direction away from the second surface and is connected to the middle frame.

7. The mobile terminal according to claim 6, Characterized in that, The first magnifying unit includes a first elastic portion and a first connecting portion horizontally extending from the first elastic portion. One side of the first elastic portion close to the first surface is fixedly connected to the first surface, and the other side of the first elastic portion away from the first surface is fixedly connected to the secondary screen. The second magnifying unit includes a second elastic portion and a second connecting portion horizontally extending from the second elastic portion. One side of the second elastic portion close to the second surface is fixedly connected to the second surface, and the other side of the second elastic portion away from the second surface is fixedly connected to the middle frame.

8. The mobile terminal according to any one of claims 1 to 3, characterized in that it further includes a flexible connecting member, and the secondary screen is flexibly connected to the middle frame through the flexible connecting member.

9. The mobile terminal according to claim 8, characterized in that a first recessed portion is formed by the side of the flexible connecting member facing the inside of the middle frame being recessed, and the size of the first recessed portion gradually decreases in a direction away from the receiving space; and / or, a second recessed portion is formed by the side of the flexible connecting member facing the secondary screen being recessed, and the size of the second recessed portion gradually decreases in a direction away from the secondary screen.

Images