Piezoelectric ceramic element, key structure, electronic equipment and method for improving drop impact resistance and feedback force of piezoelectric ceramic element

Abstract

The invention discloses a piezoelectric ceramic element, a key structure, electronic equipment and a method for improving falling impact resistance and feedback force of the piezoelectric ceramic element, and relates to the technical field of electronic equipment.The piezoelectric ceramic element comprises a substrate, a metal sheet and a piezoelectric ceramic piece, the substrate is made of a material with the loss factor larger than 0.01, and the metal sheet is made of a material with the loss factor larger than 0.01; the first end and the second end are opposite; the metal sheet is arranged on one surface of the substrate or embedded in the substrate and located between the first end and the second end. The piezoelectric ceramic piece is arranged on the surface, opposite to the substrate, of the metal piece or embedded in the substrate and located between the first end and the second end; vibration waves generated by falling impact are transmitted to the piezoelectric ceramic through the substrate and the metal sheet, so that the vibration waves transmitted to the piezoelectric ceramic are reduced, and the feedback force of the piezoelectric ceramic element is improved. According to the technical scheme provided by the invention, the drop impact resistance of the piezoelectric ceramic element can be improved, and meanwhile, the feedback force generated by the piezoelectric ceramic element is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic equipment, and in particular to a piezoelectric ceramic element, a key structure and electronic equipment, and a method for improving the drop impact resistance and feedback force of the piezoelectric ceramic element. Background Art

[0002] At present, the key structure usually uses piezoelectric ceramic elements as driving components. However, due to the structural reasons of the piezoelectric ceramic element material itself, the material has low toughness, low bending strength, and is extremely impact-resistant. When subjected to a small impact, it will crack and fail, that is, the key structure has poor drop impact resistance. At the same time, the piezoelectric ceramic element is also required to have a certain elastic modulus to ensure a good feedback force. Therefore, it is necessary to improve the drop impact resistance of the piezoelectric ceramic element without reducing the feedback force generated by the piezoelectric ceramic element. Summary of the invention

[0003] The main purpose of the present invention is to propose a piezoelectric ceramic element, a key structure and an electronic device, as well as a method for improving the drop impact resistance and feedback force of the piezoelectric ceramic element, aiming to improve the drop impact resistance performance of the piezoelectric ceramic element and at the same time improve the feedback force generated by the piezoelectric ceramic element.

[0004] To achieve the above-mentioned purpose, the present invention provides a piezoelectric ceramic element, which is applied to a key structure and includes:

[0005] A substrate is made of a material with a loss factor greater than 0.01 and has a first end and a second end opposite to each other;

[0006] A metal sheet, disposed on a surface of the substrate or embedded in the substrate, and located between the first end and the second end;

[0007] A piezoelectric ceramic sheet, disposed on a surface of the metal sheet facing away from the substrate or embedded in the substrate, and located between the first end and the second end;

[0008] The vibration wave generated by the drop impact is transmitted to the piezoelectric ceramic sheet through the substrate and the metal sheet, so as to reduce the vibration wave transmitted to the piezoelectric ceramic sheet and enhance the feedback force of the piezoelectric ceramic element.

[0009] In one embodiment, the substrate is made of at least one of a fiber material, an alloy material, a damping composite material, a plastic material, and a porous composite material.

[0010] In one embodiment, the metal sheet is disposed on one surface of the substrate, and the piezoelectric ceramic sheet is disposed on a surface of the metal sheet facing away from the substrate; the thickness of the first end and the second end are both greater than the thickness of the area between the first end and the second end.

[0011] In one embodiment, the thickness of the metal sheet is 0.25-1 times the thickness of the piezoelectric ceramic sheet, the thickness of the area between the first end and the second end is 0.5-3 times the thickness of the piezoelectric ceramic sheet; and / or the thickness of the area between the first end and the second end is 10-80% of the thickness of the first end or the second end.

[0012] In one embodiment, the thickness of the metal sheet is 0.67-1 times the thickness of the piezoelectric ceramic sheet, and the thickness of the area between the first end and the second end is 0.5-2 times the thickness of the piezoelectric ceramic sheet.

[0013] In one embodiment, the substrate includes a first substrate and a second substrate that are spaced apart, an end of the first substrate away from the second substrate forms the first end, an end of the second substrate away from the first substrate forms the second end, and two ends of the metal sheet are respectively overlapped on the first substrate and the second substrate and are located between the first end and the second end.

[0014] In one embodiment, the length of the contact surface between the metal sheet and the first substrate is greater than 1 mm;

[0015] The length of the contact surface between the metal sheet and the second substrate is greater than 1 mm.

[0016] In one embodiment, the substrate and the metal sheet are bonded by injection molding, and the metal sheet and the piezoelectric ceramic sheet are bonded; or, the substrate and the metal sheet, and the metal sheet and the piezoelectric ceramic sheet are both bonded.

[0017] The present invention also provides a key structure, which includes the piezoelectric ceramic element as described above.

[0018] The present invention further provides an electronic device, comprising the key structure as described above.

[0019] The present invention also provides a method for improving the drop impact resistance and feedback force of a piezoelectric ceramic element, the method comprising:

[0020] A material and a metal sheet with a loss factor greater than 0.01 are composited on the piezoelectric ceramic sheet so that the vibration wave generated by the drop impact is transmitted to the piezoelectric ceramic sheet through the material and the metal sheet with a loss factor greater than 0.01, thereby reducing the vibration wave transmitted to the piezoelectric ceramic sheet and enhancing the feedback force of the piezoelectric ceramic element.

[0021] In one embodiment, the step of compounding a material having a loss factor greater than 0.01 and a metal sheet on a piezoelectric ceramic sheet includes:

[0022] A metal sheet and a substrate made of a material with a loss factor greater than 0.01 are sequentially bonded and fixed to any surface of the piezoelectric ceramic sheet, and the metal sheet and the piezoelectric ceramic sheet are located between the two ends of the substrate, or,

[0023] The metal sheet is embedded in a substrate made of a material with a loss factor greater than 0.01, and the piezoelectric ceramic sheet is bonded and fixed so that the piezoelectric ceramic sheet is located between the two ends of the substrate; or,

[0024] The piezoelectric ceramic sheet and the metal sheet are embedded in a substrate made of a material with a loss factor greater than 0.01.

[0025] In one embodiment, the material with a loss factor greater than 0.01 is the same material or a composite material of two or more materials.

[0026] The technical solution of the present invention is that the piezoelectric ceramic element includes a substrate, a metal sheet and a piezoelectric ceramic sheet. The substrate is made of a material with a loss factor greater than 0.01 and has a first end and a second end opposite to each other; the metal sheet is arranged on a surface of the substrate or embedded in the substrate and is located between the first end and the second end; the piezoelectric ceramic sheet is arranged on the surface of the metal sheet facing away from the substrate or embedded in the substrate and is located between the first end and the second end; the vibration wave generated by the drop impact is transmitted to the piezoelectric ceramic sheet through the substrate and the metal sheet to reduce the vibration wave transmitted to the piezoelectric ceramic sheet and enhance the feedback force of the piezoelectric ceramic element. The present invention designs the piezoelectric ceramic element into a three-layer composite structure. During the drop process, the damping characteristics of the substrate can be used to transmit the vibration energy generated by the drop impact to the piezoelectric ceramic sheet along the substrate and the metal sheet, which will greatly reduce the transmission of the vibration energy to the piezoelectric ceramic sheet, thereby effectively reducing the fracture tendency of the piezoelectric ceramic sheet during the drop impact process, that is, the piezoelectric ceramic element has good drop impact resistance. At the same time, according to the principle of output force generation, in the three-layer composite structure of the present invention, the stiffness of the metal sheet superimposed on the stiffness of the substrate made of a material with a loss factor greater than 0.01 forms a matching relationship with the stiffness of the piezoelectric ceramic sheet, and its feedback force is significantly improved compared to that of a substrate simply made of a material with a loss factor greater than 0.01. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0028] Figure 1A schematic structural diagram of an embodiment of a piezoelectric ceramic element provided by the present invention;

[0029] Figure 2 for Figure 1 Schematic diagram of the structure of a piezoelectric ceramic element from another perspective;

[0030] Figure 3 for Figure 2 Schematic diagram of the exploded structure of a piezoelectric ceramic element;

[0031] Figure 4 for Figure 1 Schematic diagram of the structure of the substrate in the piezoelectric ceramic element;

[0032] Figure 5 A schematic structural diagram of another embodiment of a piezoelectric ceramic element provided by the present invention;

[0033] Figure 6 for Figure 5 Schematic diagram of the exploded structure of a piezoelectric ceramic element;

[0034] Figure 7 for Figure 6 Schematic diagram of the structure of the middle substrate from another perspective.

[0035] Description of Figure Numbers:

[0036] 100. Piezoelectric ceramic element; 1. substrate; 1a. first end; 1b. second end; 11. first substrate; 12. second substrate; 2. metal sheet; 3. piezoelectric ceramic sheet.

[0037] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0040] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0041] As a functional ceramic material, piezoelectric ceramics have positive piezoelectric effect and inverse piezoelectric effect. By using the positive piezoelectric effect of piezoelectric ceramics, positive and negative charges can be generated between the positive and negative electrodes of the piezoelectric ceramics when the piezoelectric ceramics are pressed, forming an electric field and current; by using the inverse piezoelectric effect of piezoelectric ceramics, when a certain driving waveform is applied between the positive and negative electrodes of the piezoelectric ceramics, the piezoelectric ceramics will deform in different directions. Using the positive and inverse piezoelectric effects of piezoelectric ceramics, various functional devices can be designed.

[0042] Piezoelectric touch feedback utilizes both the positive piezoelectric effect and the inverse piezoelectric effect of piezoelectric ceramics. When a finger presses the piezoelectric ceramic, the piezoelectric ceramic generates an electric charge, forming an electric field and current. The electrical signal is given to the receiving driver chip. After being recognized by the driver chip, the driver chip is triggered to output a certain electrical signal waveform, which is input into the piezoelectric ceramic, driving the piezoelectric ceramic to vibrate. The finger feels the vibration of the piezoelectric ceramic, which forms a tactile feedback action.

[0043] The pressure sensor, piezoelectric ceramic sheet and driver chip form a tactile feedback circuit. The pressure sensor generates a signal when the finger gently presses the pressure sensor. The signal is output to the driver chip. The driver chip outputs an electrical signal to the piezoelectric ceramic sheet, which drives the piezoelectric ceramic sheet to vibrate. The finger feels the vibration of the piezoelectric ceramic sheet, which forms a tactile feedback action. The solution using the pressure sensor has the characteristics of high sensitivity, small trigger force and short feedback time. The pressure sensor includes piezoresistive sensors, piezocalytic sensors and elastic wave sensors.

[0044] By utilizing the touch feedback principle of piezoelectric ceramics, a variety of new functional devices can be designed, such as new side function buttons on mobile phones, which can realize pressing and sliding functions. Long pressing, short pressing, and pressing with different forces of the pressing function can generate different electrical signals. The driver chip recognizes different electrical signals and outputs different vibration waveforms to the piezoelectric ceramics. Under the action of different driving waveforms, the piezoelectric ceramics form different vibration accelerations and displacements as well as feedback forces, which interact with the fingers. Similarly, when the finger slides the side function buttons of the mobile phone, the pressure sensor receives different sliding actions, such as fast sliding, slow sliding, strong sliding, or small force sliding, which can interact with the mobile phone software to generate a variety of flexible and changeable control and interactive actions, greatly improving the functions of the side buttons of the mobile phone and the human-computer interaction experience.

[0045] As the driving component of the side buttons of mobile phones, piezoelectric ceramics have the characteristics of low energy consumption, short feedback time, large vibration acceleration, and large feedback force. They have been researched and developed by many manufacturers. However, leaded piezoelectric ceramics such as PZT and lead-free piezoelectric ceramics such as KNN have low toughness, low bending strength, high notch sensitivity, and are extremely impact-resistant due to their own material structure. They will crack and fail when subjected to a small impact, which seriously limits the application of piezoelectric ceramics in smart wearable VR, AR, smart phones, smart headphones and other electronic products. Usually, smart wearable VR, AR, smart phones, smart headphones and other electronic products need to pass a variety of mechanical impact tests such as a 1.5m marble floor drop impact test, a drum drop test, and a micro-drop test. As mobile phone buttons, they are very likely to fall and crack and fail when subjected to impact, which seriously limits their application in smart wearable VR, AR, smart phones, smart headphones and other fields.

[0046] Based on this, the drop failure mechanism of the piezoelectric ceramic sheet used in the side keys of mobile phones is analyzed specifically as follows: At the moment the mobile phone falls, there are three types of forces acting on the piezoelectric ceramic sheet, causing the piezoelectric ceramic sheet to be destroyed: (1) Instantaneous acceleration. During the fall, the mobile phone rebounds at the moment of impact with the marble floor. The action time is less than 0.01s, and its instantaneous acceleration reaches 780m / s 2, under the action of the weight of the piezoelectric ceramic sheet itself and the gravity of the structural parts rigidly connected to it, a force is generated to act on the piezoelectric ceramic sheet, causing the piezoelectric ceramic sheet to produce instantaneous strain. When the instantaneous strain exceeds the strain that the piezoelectric ceramic sheet can withstand, the piezoelectric ceramic sheet will break; (2) Rigid impact of the key body. The key body protrudes from the side surface of the mobile phone. When the side of the mobile phone falls, the key body first touches the ground. The weight and impact force of the entire mobile phone act on the key, causing the key body to move inward and instantly act on the piezoelectric ceramic sheet, causing the piezoelectric ceramic sheet to impact and deform, that is, the piezoelectric ceramic sheet cracks. (3) Vibration impact on the piezoelectric ceramic sheet. When the mobile phone falls, the interaction between the ground and the mobile phone and the key body, as well as the interaction between the mobile phone frame and the piezoelectric ceramic sheet and the substrate, will generate a strong impact vibration wave. Under the action of the vibration wave, the piezoelectric ceramic sheet and the substrate will vibrate up and down. The superposition of vibration waves will cause the piezoelectric ceramic sheet to crack when the stress exceeds the limit that the piezoelectric ceramic sheet can withstand.

[0047] Based on the above technical problems and drop failure mechanism, the drop impact resistance of piezoelectric ceramic components can be improved by using a substrate of high damping material (i.e., material with loss factor greater than 0.01) and a matching combination of piezoelectric ceramic sheets. However, the large loss factor of the substrate material not only reduces the vibration energy transmission during the drop process, but also weakens its own energy conversion. High damping materials (i.e., materials with loss factor greater than 0.01) usually have a low elastic modulus. For example, the elastic modulus of epoxy glass fiber materials is usually 20-30GPa, the elastic modulus of engineering plastics is usually 1-4GPa, and the modulus of carbon fiber materials is usually 18.5GPa. That is, the elastic modulus of the material matched with the piezoelectric ceramic sheet is low, resulting in a smaller feedback force after matching with the piezoelectric ceramic sheet. For example, the piezoelectric ceramic material of the same size can reach a feedback force of 4.5N after matching and compounding with stainless steel material, but the maximum feedback force after matching and compounding with epoxy glass fiber material can only reach 3.7N, which is nearly 20% lower than the maximum feedback force of stainless steel material. The feedback force limits the use of high damping materials and piezoelectric ceramic materials to a certain extent. Therefore, it is necessary to improve the drop impact resistance of piezoelectric ceramic elements without reducing the feedback force generated by the piezoelectric ceramic sheet and its coupling material.

[0048] Based on this, the principle and influencing factors of the output force generated by the cooperation between the piezoelectric ceramic sheet and the substrate are analyzed in a targeted manner, as follows: when the piezoelectric ceramic sheet is subjected to a positive voltage, the polarization direction of the piezoelectric ceramic sheet is perpendicular to the direction of the piezoelectric ceramic sheet (that is, the thickness direction of the piezoelectric ceramic sheet). When a positive voltage with the same polarization direction is applied between the positive and negative electrodes of the piezoelectric ceramic sheet, the piezoelectric ceramic sheet produces an elongation deformation in a direction perpendicular to the piezoelectric ceramic sheet. According to the principle of volume invariance, the piezoelectric ceramic sheet produces a contraction deformation in a direction parallel to the piezoelectric ceramic sheet (that is, the length direction of the piezoelectric ceramic sheet). The piezoelectric ceramic sheet pulls the side where the substrate and the piezoelectric ceramic sheet contact each other toward the middle. Under the action of the supporting forces at both ends, the middle of the substrate pushes upward, forming an upward force and displacement, which is transmitted to the button body or finger or test pressure head in contact with it, thereby generating a touch and force.

[0049] In this process, the positively correlated factors that affect the generated force include electrical signals (voltage, frequency, waveform characteristics), piezoelectric ceramic sheet factors (elastic modulus of the piezoelectric ceramic sheet, thickness of the piezoelectric ceramic sheet, width of the piezoelectric ceramic sheet, length of the piezoelectric ceramic sheet), matching substrate factors (elastic modulus of the substrate, thickness of the substrate, width of the substrate, length of the substrate), and bonding glue factors (thickness of the glue, stiffness of the glue, bonding strength of the glue to the substrate and ceramics).

[0050] The contraction force F generated by the piezoelectric ceramic piece = d31 × the length of the piezoelectric ceramic piece × the elastic modulus of the piezoelectric ceramic piece × 1 / 2 × the width b of the piezoelectric ceramic piece × (the thickness h of the piezoelectric ceramic piece) 2 , the force delivered to one side of the substrate = the contraction force generated by the piezoelectric ceramic piece × the glue transfer coefficient, the force delivered to one side of the substrate = the reverse force generated by the substrate bending to a certain arc, the reverse force generated by the substrate bending to a certain arc = 1 / 2bh 2× elastic modulus × radian. When the stiffness of the substrate is equal to that of the piezoelectric ceramic sheet, the maximum feedback force can be generated. There is a certain correlation between the elastic modulus of the substrate and the loss factor of the substrate. For the same type of material, such as stainless steel, its elastic modulus is 200GPa, but its loss factor is very low, which is 0.001-0.008. The vibration energy loss is small during the conduction process, and the external input action energy is transmitted to the piezoelectric ceramic sheet almost without loss. In the actual falling process, using a steel sheet as a substrate, the piezoelectric ceramic sheet is almost 100% broken. According to the simulation calculation results, the maximum stress acting on the piezoelectric ceramic sheet reaches 300MPa, which is much higher than the maximum stress of 110MPa that the piezoelectric ceramic sheet can withstand. If the substrate is made of epoxy glass fiber material, its elastic modulus is between 20-30GPa, and its loss factor is relatively high, with a loss factor of 0.2, which is almost 200 times that of stainless steel. In the process of falling, the epoxy glass fiber material passed all the drops. The simulation results show that the maximum stress of epoxy glass fiber material as the substrate material plus the groove weakening structure at both ends of the substrate is 20MPa, which is much smaller than the 110MPa of ceramic fracture. However, the feedback force of the epoxy glass fiber material substrate was measured to be 3.7N in a 1.5m drop test. The reason is that the elastic modulus of the epoxy glass fiber material substrate coupled with the piezoelectric ceramic sheet is low, resulting in a low feedback force output after the piezoelectric ceramic sheet and the epoxy glass fiber material substrate are coupled. Therefore, it is necessary to increase its feedback force.

[0051] Based on the above analysis, the present invention proposes a composite structure solution for piezoelectric ceramic elements to solve the problem of failure and low feedback force when piezoelectric ceramic sheets are used as touch-pressure feedback power devices during a drop process. On the one hand, the piezoelectric ceramic elements can withstand the impact damage during the drop of mobile phones and other similar applications, and on the other hand, the problem of low feedback force of piezoelectric ceramic elements as touch-pressure feedback power devices is improved. The piezoelectric ceramic element 100 provided by the present invention is applied to the key structure of electronic devices.

[0052] See also Figures 1 to 3 In one embodiment of the present invention, a piezoelectric ceramic element 100 includes a substrate 1, a metal sheet 2 and a piezoelectric ceramic sheet 3. The substrate 1 is made of a material with a loss factor greater than 0.01 and has a first end 1a and a second end 1b opposite to each other; the metal sheet 2 is arranged on a surface of the substrate 1 or embedded in the substrate 1 and is located between the first end 1a and the second end 1b; the piezoelectric ceramic sheet 3 is arranged on a surface of the metal sheet 2 facing away from the substrate 1 or embedded in the substrate 1 and is located between the first end 1a and the second end 1b; the vibration wave generated by the drop impact is transmitted to the piezoelectric ceramic sheet 3 through the substrate 1 and the metal sheet 2, so as to reduce the vibration wave transmitted to the piezoelectric ceramic sheet 3 and enhance the feedback force of the piezoelectric ceramic element 100.

[0053] Specifically, the substrate 1 is roughly in the shape of a rectangular plate, and has one end and a second end 1b opposite to each other along its length. The substrate 1 is made of a material with a loss factor greater than 0.01, and can effectively absorb and weaken the vibration energy when subjected to the transmission of vibration energy. The metal sheet 2 and the piezoelectric ceramic sheet 3 are both roughly in the shape of long strips, and the lengths of the metal sheet 2 and the piezoelectric ceramic sheet 3 are both shorter than the length of the substrate 1. Optionally, the widths of the metal sheet 2 and the piezoelectric ceramic sheet 3 are the same as the widths of the substrate 1. In this way, the substrate 1 can effectively transmit the vibration energy, play a role in weakening the vibration energy, and greatly reduce the transmission of the vibration energy to the metal sheet 2 and the piezoelectric ceramic sheet 3, thereby effectively reducing the fracture tendency of the piezoelectric ceramic sheet 3 during the drop impact process.

[0054] The substrate 1, the metal sheet 2 and the piezoelectric ceramic sheet 3 can be stacked in sequence, and the connection and fixing method can be selected as an adhesive connection or injection molding into an integrated structure, which is not limited here. The piezoelectric ceramic sheet 3 is in direct contact with the metal sheet 2. According to the principle of output force generation, in the three-layer composite structure of the present invention, the stiffness of the metal sheet 2 is superimposed on the stiffness of the substrate 1 made of a material with a loss factor greater than 0.01 to form a matching relationship with the stiffness of the piezoelectric ceramic sheet 3, and its feedback force is significantly improved compared to the substrate 1 made of a material with a loss factor greater than 0.01.

[0055] Of course, the metal sheet 2 can be embedded in the substrate 1, or the piezoelectric ceramic sheet 3 can be embedded in the substrate 1, or the piezoelectric ceramic sheet 3 and the metal sheet 2 can be embedded in the substrate 1 at the same time. Specifically, the piezoelectric ceramic sheet 3 and the metal sheet 2 can be embedded in the substrate 1 by injection molding. In this way, the vibration energy generated by external impact can also be transmitted through the substrate, thereby greatly reducing the transmission of vibration energy to the piezoelectric ceramic sheet 3 and the metal sheet. According to the principle of output force generation, in the three-layer composite structure of the present invention, the stiffness of the metal sheet 2 superimposed on the stiffness of the substrate 1 made of a material with a loss factor greater than 0.01 can also form a matching relationship with the stiffness of the piezoelectric ceramic sheet 3, and its feedback force is relatively high.

[0056] In order to increase the feedback force, optionally, the piezoelectric ceramic sheet 3 and the metal sheet 2 are both embedded in the substrate 1 , and the metal sheet 2 is in lateral contact with one side of the piezoelectric ceramic sheet 3 .

[0057] The present invention designs the piezoelectric ceramic element 100 into a three-layer composite structure. During the falling process, the damping characteristics of the substrate 1 can be used to transfer the vibration energy generated by the falling impact to the piezoelectric ceramic sheet 3 along the substrate 1 and the metal sheet 2. This will greatly reduce the transmission of vibration energy to the piezoelectric ceramic sheet 3, thereby effectively reducing the fracture tendency of the piezoelectric ceramic sheet 3 during the falling impact process, that is, the piezoelectric ceramic element 100 has good anti-falling impact performance. At the same time, the piezoelectric ceramic sheet 3 is in direct contact with the steel plate. According to the principle of output force generation, in the three-layer composite structure of the present invention, the stiffness of the metal sheet 2 is superimposed on the stiffness of the substrate 1 made of a material with a loss factor greater than 0.01 to form a matching relationship with the stiffness of the piezoelectric ceramic sheet 3, and its feedback force is significantly improved compared to the substrate 1 made of a material with a loss factor greater than 0.01.

[0058] The substrate 1 of this embodiment is made of high damping material (i.e., material with a loss factor greater than 0.01), which can more effectively reduce the transmission of vibration energy to the metal sheet 2 and the piezoelectric ceramic sheet 3 during the falling process, thereby effectively reducing the fracture tendency of the piezoelectric ceramic sheet 3 during the falling impact process, that is, the piezoelectric ceramic element 100 has better anti-drop impact performance.

[0059] In an optional embodiment of the present invention, the material of the substrate 1 includes at least one of a fiber material, an alloy material, a damping composite material, a plastic material, and a porous composite material. Among them, the fiber material can be selected from epoxy glass fiber, carbon fiber, asbestos fiber or other high-damping fiber materials; the alloy material can be selected from copper-zinc-aluminum alloy, iron-chromium-molybdenum alloy, manganese-copper series alloy, magnesium alloy or other high-damping alloy materials, the damping composite material can be selected from rubber metal composite material, rubber fiber composite material or other high-damping composite material; the plastic material can be selected from polyacrylate, polyurethane, polyvinyl butyral or other high-damping plastic materials, and the porous composite material can be selected from foam metal or other high-damping porous composite materials. In practical applications, the substrate 1 can be selected from one or more of the above materials.

[0060] In an optional embodiment of the present invention, the metal sheet 2 may be a steel sheet, a copper sheet or a nickel sheet, which has good mechanical strength. After being compounded to the piezoelectric ceramic sheet 3, the piezoelectric ceramic element 100 can have a higher feedback force.

[0061] Please refer again Figures 1 to 4 In one embodiment of the present invention, the metal sheet 2 is arranged on a surface of the substrate 1, and the piezoelectric ceramic sheet 3 is arranged on the surface of the metal sheet 2 facing away from the substrate 1; the thickness of the first end 1a and the second end 1b are both greater than the thickness of the area between the first end 1a and the second end 1b.

[0062] In this embodiment, the piezoelectric ceramic sheet 3, the metal sheet 2 and the substrate 1 are stacked in sequence, wherein the thickness of the first end 1a and the thickness of the second end 1b of the substrate 1 are both larger than the thickness of the middle area, that is, the substrate 1 forms a groove structure as a whole, so that during the falling process, when the vibration energy is transmitted to the substrate 1, it is transmitted to the middle area through the first end 1a and the second end 1b, and the substrate 1 made of high damping material (that is, a material with a loss factor greater than 0.01) and the formed groove structure can play a more effective role in weakening the vibration energy. At the same time, during the falling process, when the weight of the piezoelectric ceramic sheet 3 and the metal sheet 2 themselves and the impact force of the key body are applied to the piezoelectric ceramic sheet 3, the formed groove structure can absorb most of the deformation, so that the deformation of the piezoelectric ceramic sheet 3 and the metal sheet 2 is extremely small, which is not enough to cause impact damage to the piezoelectric ceramic sheet 3, that is, the piezoelectric ceramic element 100 has better anti-drop impact performance.

[0063] It should be noted that the thickness of the first end 1a and the thickness of the second end 1b can be the same or different, and there is no limitation here. Of course, in order to facilitate manufacturing and achieve more uniform weakening of vibration energy, the thickness of the first end 1a is the same as the thickness of the second end 1b.

[0064] In one embodiment of the present invention, the thickness of the metal sheet 2 is 0.25-1 times (such as 0.25 times, 0.5 times, 0.75 times, 1 times and any interval between the two end values) of the thickness of the piezoelectric ceramic sheet 3, and the thickness of the area between the first end 1a and the second end 1b is 0.5-3 times (such as 0.5 times, 1 times, 1.5 times, 2 times, 2.5 times, 3 times and any interval between the two end values) of the thickness of the piezoelectric ceramic sheet 3. In this embodiment, the thickness of the substrate 1, the thickness of the metal sheet 2 and the thickness of the piezoelectric ceramic sheet 3 are matched, so that the piezoelectric ceramic element 100 can have better anti-drop impact performance and higher feedback force.

[0065] In one embodiment of the present invention, the thickness of the area between the first end 1a and the second end 1b is 10-80% of the thickness of the first end 1a or the second end 1b, that is, the depth of the groove formed by the substrate 1 is 20-90% of the thickness of the first end 1a or the second end 1b. In this way, the vibration energy can be more effectively weakened, so that the piezoelectric ceramic element 100 has better anti-drop impact performance, while ensuring the overall strength of the substrate 1.

[0066] In one embodiment of the present invention, the thickness of the metal sheet 2 is 0.67-1 times (such as 0.67 times, 0.75 times, 0.85 times, 1 times and the interval between any two end values) of the thickness of the piezoelectric ceramic sheet 3, and the thickness of the area between the first end 1a and the second end 1b is 0.5-2 times (such as 0.5 times, 1 times, 1.5 times, 2 times and the interval between any two end values) of the thickness of the piezoelectric ceramic sheet 3. The difference between this embodiment and the above embodiment is that the thickness of the metal sheet 2 is increased, and the thickness of the area between the first end 1a and the second end 1b is reduced, so that the stiffness of the piezoelectric ceramic sheet 3 can match the stiffness of the metal sheet 2 and the substrate 1, the composite elastic modulus of the metal sheet 2 and the substrate 1 is higher, and its feedback force is further improved. At the same time, the piezoelectric ceramic element 100 has better drop impact resistance.

[0067] Please refer to Figure 7 In one embodiment of the present invention, the substrate 1 includes a first substrate 111 and a second substrate 121 that are spaced apart, an end of the first substrate 111 away from the second substrate 121 forms a first end 1a, an end of the second substrate 1 away from the first substrate 111 forms a second end 1b, and two ends of the metal sheet 2 are respectively overlapped on the first substrate 111 and the second substrate 121, and are located between the first end 1a and the second end 1b.

[0068] In this embodiment, the substrate 1 adopts a disconnected structure, that is, it includes a first substrate 111 and a second substrate 121 arranged at intervals, and the back-to-back ends of the first substrate 111 and the second substrate 121 form a first end 1a and a second end 1b respectively, and the two ends of the metal sheet 2 are respectively overlapped on the first substrate 111 and the second substrate 121, and are located between the first end 1a and the second end 1b, and the piezoelectric ceramic sheet 3 is completely matched with the metal sheet 2. Since the metal sheet 2 does not completely contact the substrate 1, the groove structure formed by the first substrate 111 and the second is weakened, which effectively reduces the resonance frequency of the overall structure, and the feedback force outputted is further improved, and the piezoelectric ceramic element 100 has a good drop impact resistance.

[0069] In an optional embodiment of the present invention, the length of the contact surface between the metal sheet 2 and the first substrate 111 is greater than 1 mm; the length of the contact surface between the metal sheet 2 and the second substrate 121 is greater than 1 mm. Such a design can achieve overlapping and fixing of the metal sheet 2, effectively reduce the resonance frequency of the overall structure, further improve its output feedback force, and save production costs to a certain extent.

[0070] The piezoelectric ceramic element 100 of the above embodiment of the present invention can be manufactured by two methods. The first method is to use injection molding to combine the substrate 1 and the metal sheet 2 into an integrated structure, and the metal sheet 2 and the piezoelectric ceramic sheet 3 are bonded and fixed. The second method is to use bonding to fix the substrate 1 and the metal sheet 2, and the metal sheet 2 and the piezoelectric ceramic sheet 3. The specific operation is: firstly, a material with a loss factor greater than 0.01 is processed by CNC processing to obtain a substrate 1, and then the substrate 1 and the metal sheet 2 are bonded and fixed by a tool, and then the piezoelectric ceramic sheet 3 and the metal sheet 2 are bonded and fixed by glue.

[0071] The present invention also proposes a key structure, which includes a piezoelectric ceramic element 100. The specific structure of the piezoelectric ceramic element 100 refers to the above embodiment. Since this key structure adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0072] The key structure provided by the present invention also includes a mounting shell, a key body and a pressure sensor. The mounting shell is a part of an electronic device, such as a mobile phone frame, a tablet frame, or other structural parts, which is convenient for user operation. The specific structure of the mounting shell is not limited. The material of the mounting shell can be plastic, or metal materials such as stainless steel, aluminum alloy, titanium alloy, etc., which are not limited here. The mounting shell is provided with a accommodating space with at least one side opening. The piezoelectric ceramic element 100 and the sensor are both located in the accommodating space, and the substrate 1 of the piezoelectric ceramic element 100 is fixed to the mounting shell. The key body is arranged on the surface of the mounting shell facing the opening, and at least partially extends into the opening and the accommodating space, and the extending portion of the key body abuts against the piezoelectric ceramic element 100.

[0073] The piezoelectric ceramic element 100 can be a positive structure, that is, the key body, substrate 1, metal sheet 2 and piezoelectric ceramic sheet 3 are stacked in sequence. Of course, the piezoelectric ceramic sheet 3 can also be a reverse structure, that is, the key body, piezoelectric ceramic sheet 3, metal sheet 2 and substrate 1 are stacked in sequence.

[0074] The pressure sensor can be set as one, and one pressure sensor can be optionally glued and fixed on any surface of the first end 1a2a or any surface of the second end 1b2b; of course, in order to improve the sensitivity of the key structure, the pressure sensor can also be set as two, and the two pressure sensors are respectively glued and fixed on any surface of the first end 1a2a and any surface of the second end 1b2b.

[0075] It should be noted that the pressure sensor and the piezoelectric ceramic sheet 3 are both electrically connected to the control unit. The pressure sensor generates an electrical signal after receiving the pressure from the key body, and transmits the electrical signal to the control unit. After receiving the electrical signal, the control unit outputs a signal to realize the key response function, and outputs a pulse signal to the piezoelectric ceramic sheet 3. Under the action of the inverse piezoelectric effect, the piezoelectric ceramic sheet 3 generates vibration and transmits it to the key body, so that the key body vibrates to achieve a vibration feedback effect. Among them, the control unit can be selected as a driver chip in an electronic device, and the driver chip is electrically connected to the pressure sensor and the piezoelectric element through a connecting wire.

[0076] Of course, in order to further improve the drop impact resistance of the key structure, the key structure may also include a buffer pad, which is arranged on the side of the piezoelectric ceramic element 100 facing away from the key body. For example, when the piezoelectric ceramic sheet 3 is installed upright, the buffer pad is arranged between the piezoelectric ceramic sheet 3 and the mounting shell; when the piezoelectric ceramic sheet 3 is installed reversely, the buffer pad is arranged between the substrate 1 and the mounting shell.

[0077] The present invention also proposes an electronic device, which includes a key structure. The specific structure of the key structure refers to the above embodiment. Since the electronic device adopts all the technical solutions of all the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here. Among them, the electronic device includes but is not limited to smart phones, tablet computers, personal computers, laptops, smart watches, wearable devices, digital cameras, video cameras, game consoles, audio, video playback devices and smart home devices.

[0078] The present invention also proposes a method for improving the drop impact resistance and feedback force of the piezoelectric ceramic element 100, the method comprising:

[0079] A material with a loss factor greater than 0.01 and a metal sheet 2 are composited on the piezoelectric ceramic sheet 3 so that the vibration wave generated by the drop impact is transmitted to the piezoelectric ceramic sheet 3 through the material with a loss factor greater than 0.01 and the metal sheet 2, thereby reducing the vibration wave (i.e., vibration energy) transmitted to the piezoelectric ceramic sheet 3 and enhancing the feedback force of the piezoelectric ceramic element 100.

[0080] The method provided by the present invention uses a metal sheet 2 and a material with a loss factor greater than 0.01 to reduce the vibration wave (i.e., vibration energy) transmitted to the piezoelectric ceramic sheet 3 during the falling process, thereby improving the anti-drop impact of the piezoelectric ceramic element 100 and improving the feedback force of the piezoelectric ceramic element 100. The method is relatively effective and relatively simple to operate. The method for improving the anti-drop impact and feedback force of the piezoelectric ceramic element 100 provided by the present invention can be applied to the key structure of the above-mentioned electronic device, and of course, can also be applied to other functional devices containing piezoelectric ceramics.

[0081] In some embodiments of the present invention, the step of compounding a material having a loss factor greater than 0.01 and a metal sheet 2 on the piezoelectric ceramic sheet 3 includes:

[0082] A metal sheet 2 and a substrate 1 made of a material with a loss factor greater than 0.01 are sequentially bonded and fixed to any surface of the piezoelectric ceramic sheet 3 , and the metal sheet 2 and the piezoelectric ceramic sheet 3 are located between two ends of the substrate 1 .

[0083] Specifically, a material with a loss factor greater than 0.01 is first used to make a substrate 1, the substrate 1 is bonded and fixed to the metal sheet 2, the metal sheet 2 is bonded and fixed to the piezoelectric ceramic sheet 3, and the metal sheet 2 and the piezoelectric ceramic sheet 3 are located between the first end 1a and the second end 1b of the substrate, that is, the length of the substrate 1 is not less than the length of the metal sheet 2 and the length of the piezoelectric ceramic sheet 3, so that the vibration wave (that is, the vibration energy) transmitted to the piezoelectric ceramic sheet 3 during the falling process can be effectively reduced, the anti-fall impact of the piezoelectric ceramic element 100 is improved, and the feedback force of the piezoelectric ceramic element 100 is improved. This method is more effective and simple to operate. The specific structural settings of the piezoelectric ceramic sheet 3, the metal sheet 2 and the substrate 1 can refer to the above embodiments, and will not be repeated here.

[0084] In some other embodiments of the present invention, the step of compounding a material with a loss factor greater than 0.01 and a metal sheet on the piezoelectric ceramic sheet 3 includes:

[0085] The metal sheet 2 is embedded in a substrate 1 made of a material with a loss factor greater than 0.01, and the piezoelectric ceramic sheet 3 is bonded and fixed so that the piezoelectric ceramic sheet 3 is located between the two ends of the substrate 1 .

[0086] Specifically, the metal sheet 2 is embedded in a material with a loss factor greater than 0.01 by injection molding to form a substrate 1, and then the substrate 1 and the piezoelectric ceramic sheet 3 are bonded and fixed, and the piezoelectric ceramic sheet 3 is located between the first end 1a and the second end 1b of the substrate 1, that is, the length of the substrate 1 is not less than the length of the metal sheet 2 and the length of the piezoelectric ceramic sheet 3. This can also effectively reduce the vibration wave (that is, vibration energy) transmitted to the piezoelectric ceramic sheet 3 during the falling process, enhance the anti-fall impact of the piezoelectric ceramic element 100, and at the same time enhance the feedback force of the piezoelectric ceramic element 100. This method is relatively effective and relatively simple to operate.

[0087] In some other embodiments of the present invention, the step of compounding a material having a loss factor greater than 0.01 and a metal sheet 2 on the piezoelectric ceramic sheet 3 includes:

[0088] The piezoelectric ceramic sheet 3 and the metal sheet 2 are both embedded in a substrate 1 made of a material having a loss factor greater than 0.01.

[0089] Specifically, the piezoelectric ceramic sheet 3 and the metal sheet 2 are embedded in a material with a loss factor greater than 0.01 by injection molding, so that the substrate 1 completely covers the piezoelectric ceramic sheet 3 and the metal sheet 2. This can also effectively reduce the vibration wave (that is, vibration energy) transmitted to the piezoelectric ceramic sheet 3 during the falling process, enhance the drop impact resistance of the piezoelectric ceramic element 100, and enhance the feedback force of the piezoelectric ceramic element 100. This method is relatively effective and relatively simple to operate.

[0090] In order to further enhance the feedback force of the piezoelectric ceramic element 100 , one side of the piezoelectric ceramic sheet 3 is in contact with the metal sheet 2 .

[0091] In some embodiments of the present invention, the material with a loss factor greater than 0.01 composited on the piezoelectric ceramic sheet 3 can be the same material or a composite of two or more materials, which is not limited here and is within the protection scope of the present invention. Among them, the selection of materials with a loss factor greater than 0.01 can refer to the above embodiments and will not be repeated here. When the material with a loss factor greater than 0.01 is composited with two or more materials, the composite method can be doping composite, segmented composite, or other reasonable composite methods between materials, which is not limited here.

[0092] It should be noted that the specific structure of the substrate 1 made of a material with a loss factor greater than 0.01 can refer to the above embodiment and will not be described in detail here.

[0093] The above description is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A piezoelectric ceramic element, applied to a key structure, characterized in that: include: A substrate is made of a material with a loss factor greater than 0.01 and has a first end and a second end opposite to each other; A metal sheet, disposed on a surface of the substrate or embedded in the substrate, and located between the first end and the second end; A piezoelectric ceramic sheet, disposed on a surface of the metal sheet facing away from the substrate or embedded in the substrate, and located between the first end and the second end; The vibration wave generated by the drop impact is transmitted to the piezoelectric ceramic sheet through the substrate and the metal sheet, so as to reduce the vibration wave transmitted to the piezoelectric ceramic sheet and enhance the feedback force of the piezoelectric ceramic element.

2. The piezoelectric ceramic element according to claim 1, wherein: The substrate is made of at least one of a fiber material, an alloy material, a damping composite material, a plastic material, and a porous composite material.

3. The piezoelectric ceramic element according to claim 1, wherein: The metal sheet is arranged on a surface of the substrate, and the piezoelectric ceramic sheet is arranged on a surface of the metal sheet facing away from the substrate; The thickness of the first end and the second end are both greater than the thickness of the area between the first end and the second end.

4. The piezoelectric ceramic element according to claim 3, characterized in that: The thickness of the metal sheet is 0.25-1 times the thickness of the piezoelectric ceramic sheet, and the thickness of the area between the first end and the second end is 0.5-3 times the thickness of the piezoelectric ceramic sheet; and / or, The thickness of the region between the first end and the second end is 10-80% of the thickness of the first end or the second end.

5. The piezoelectric ceramic element according to claim 4, characterized in that: The thickness of the metal sheet is 0.67-1 times the thickness of the piezoelectric ceramic sheet, and the thickness of the area between the first end and the second end is 0.5-2 times the thickness of the piezoelectric ceramic sheet.

6. The piezoelectric ceramic element according to claim 3, characterized in that: The substrate includes a first substrate and a second substrate that are spaced apart from each other, wherein an end of the first substrate away from the second substrate forms the first end, and an end of the second substrate away from the first substrate forms the second end, and two ends of the metal sheet are respectively overlapped on the first substrate and the second substrate and are located between the first end and the second end.

7. The piezoelectric ceramic element according to claim 6, wherein: The length of the contact surface between the metal sheet and the first substrate is greater than 1 mm; The length of the contact surface between the metal sheet and the second substrate is greater than 1 mm.

8. The piezoelectric ceramic element according to any one of claims 1 to 7, characterized in that: The substrate and the metal sheet are bonded by injection molding, and the metal sheet and the piezoelectric ceramic sheet are bonded by bonding; or, The substrate and the metal sheet, and the metal sheet and the piezoelectric ceramic sheet are both fixed by bonding.

9. A key structure, characterized in that: The key structure comprises the piezoelectric ceramic element according to any one of claims 1 to 8.

10. An electronic device, characterized in that: The electronic device comprises the key structure as claimed in claim 9.

11. A method for improving the drop impact resistance and feedback force of a piezoelectric ceramic element, characterized in that: The method comprises: A material and a metal sheet with a loss factor greater than 0.01 are composited on the piezoelectric ceramic sheet so that the vibration wave generated by the drop impact is transmitted to the piezoelectric ceramic sheet through the material and the metal sheet with a loss factor greater than 0.01, thereby reducing the vibration wave transmitted to the piezoelectric ceramic sheet and enhancing the feedback force of the piezoelectric ceramic element.

12. The method for improving the drop impact resistance and feedback force of a piezoelectric ceramic element as claimed in claim 11, characterized in that: The step of compounding a material with a loss factor greater than 0.01 and a metal sheet on a piezoelectric ceramic sheet includes: A metal sheet and a substrate made of a material with a loss factor greater than 0.01 are sequentially bonded and fixed to any surface of the piezoelectric ceramic sheet, and the metal sheet and the piezoelectric ceramic sheet are located between the two ends of the substrate, or, The metal sheet is embedded in a substrate made of a material with a loss factor greater than 0.01, and the piezoelectric ceramic sheet is bonded and fixed so that the piezoelectric ceramic sheet is located between the two ends of the substrate; or, The piezoelectric ceramic sheet and the metal sheet are embedded in a substrate made of a material with a loss factor greater than 0.

01.

13. The method for improving the drop impact resistance and feedback force of a piezoelectric ceramic element as claimed in claim 11, characterized in that: The material with a loss factor greater than 0.01 is the same material or a composite material of two or more materials.

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