CN112951976A - Polarization method of piezoelectric material, piezoelectric module and electrodeless ultrasonic wave transmitter - Google Patents
Polarization method of piezoelectric material, piezoelectric module and electrodeless ultrasonic wave transmitter Download PDFInfo
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 9
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- 229910052742 iron Inorganic materials 0.000 claims description 4
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- 239000000956 alloy Substances 0.000 claims description 3
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Abstract
The application discloses a polarization method of piezoelectric material, a piezoelectric component and an electrodeless ultrasonic wave transmitting device. The polarization method of the piezoelectric material comprises the following steps: processing the piezoelectric material to form an annular piezoelectric structure; the piezoelectric structure and a coil are sleeved on a magnetizer at intervals; a periodic excitation signal is input into the coil, so that a first annular electric field and a second annular electric field which are different in direction are sequentially generated in the circumferential direction of the magnetizer in each period, the strength of the first annular electric field is greater than that of the second annular electric field, and the piezoelectric structure is circularly polarized. The polarization method of the piezoelectric material realizes annular polarization which cannot be realized by the existing polarization mode; in the process of annular polarization of the piezoelectric structure, electrodes do not need to be printed on the piezoelectric structure, and adverse effects on the performance of the piezoelectric material caused by oxidation of the printed electrodes and additional mass generated by printing the electrodes are avoided.
Description
Technical Field
The application relates to the technical field of piezoelectric materials, in particular to a polarization method of a piezoelectric material, a piezoelectric assembly and an electrodeless ultrasonic transmitter.
Background
The acoustic piezoelectric material and the sensor thereof are widely applied to devices such as fingerprint identification, gesture identification, positioning and ranging, directional sounding and the like. The principle of the above-described devices for realizing acoustic emission is generally based on the following: the piezoelectric material is polarized in the thickness direction to have a piezoelectric effect, and an alternating voltage is applied to both ends of the piezoelectric material, and the piezoelectric material undergoes periodic contraction or elongation in the thickness direction and the length direction according to the frequency of the alternating voltage, and the piezoelectric material vibrates due to the periodic contraction or elongation, and further emits sound waves in the direction in which the piezoelectric material is deformed. The sound wave emitting surface of the piezoelectric material is a surface perpendicular to the deformation direction.
The polarization modes of the piezoelectric material mainly comprise corona polarization, in-situ polarization and direct polarization of an oil bath electrode. The corona polarization and in-situ polarization modes at least need to print or attach one surface of an electrode, or piezoelectric materials are prepared on a conductive base material, negative ions are ionized through an electrode wire and are transported to the surface of the piezoelectric materials without electrodes or deviating from the conductive base material through grid voltage, and the negative ions and the electrode or the conductive base material form potential difference to polarize the piezoelectric materials. Direct oil bath electrode polarization requires printing or attaching of double-sided electrodes and polarization with voltage source applied.
In the course of implementing the present application, the applicant has found that there are at least the following problems in the prior art: the piezoelectric material needs to be printed with electrodes on at least one surface in the polarization and working processes, and needs to be integrated with a device in a hard mode, so that the piezoelectric material cannot be replaced and separated; the printed electrodes are oxidized and the additional mass produced by the printing affects the acoustic emission performance of the piezoelectric material.
Disclosure of Invention
In view of the above, it is necessary to provide a polarization method of piezoelectric material, a piezoelectric module and an electrodeless ultrasonic wave emitting device to solve the above problems.
An embodiment of the present application provides a polarization method for a piezoelectric material, including the following steps:
processing the piezoelectric material to form an annular piezoelectric structure;
sleeving the piezoelectric structure and a coil on a magnetizer at intervals; and
inputting a periodic excitation signal into the coil, so that a first annular electric field and a second annular electric field are sequentially generated in the circumferential direction of the magnetizer in each period, and the piezoelectric structure is circularly polarized, wherein the strength of the first annular electric field is greater than that of the second annular electric field, and the direction of the first annular electric field is opposite to that of the second annular electric field.
According to the polarization method of the piezoelectric material, the annular piezoelectric structure and the coil are sleeved in the magnetizer, a periodic excitation signal is input into the coil, the excitation signal continuously changes in a period, so that the magnetizer generates a changed magnetic flux in the axial direction, the changed magnetic flux enables the circumferential direction of the magnetizer to generate a first annular electric field and a second annular electric field which are different in size and direction in each period, and the intensity of the first annular electric field is greater than that of the second annular electric field; the piezoelectric structure is circularly polarized based on the interaction of the first circular electric field and the second circular electric field, so that circular polarization which cannot be realized by the conventional polarization mode is realized; in the process of annular polarization of the piezoelectric structure, electrodes do not need to be printed on the piezoelectric structure, and adverse effects on the performance of the piezoelectric material caused by oxidation of the printed electrodes and additional mass generated by printing the electrodes are avoided.
In some embodiments, the step of inputting a periodic excitation signal into the coil, so that the circumferential direction of the magnetizer generates a first circumferential electric field and a second circumferential electric field sequentially in each period, so that the piezoelectric structure is circumferentially polarized further includes:
the piezoelectric structure is circularly polarized over one or more cycles.
Therefore, by controlling the magnitude and the period of the excitation signal, the piezoelectric structure can be circularly polarized in one period, and the process required by circularly polarizing the piezoelectric material is shortened; or by controlling the size and the period of the excitation signal, the piezoelectric structure can be circularly polarized in a plurality of periods, and the adoption of the existing excitation signal input coil is facilitated to carry out circular polarization on the piezoelectric structure.
In some embodiments, the magnetizer is any one of silicon steel sheet, pure iron, mild steel, non-silicon steel, iron-nickel alloy, iron-aluminum alloy, amorphous alloy, and microcrystalline alloy.
Therefore, the magnetizer is made of the materials, so that the magnetic conductivity of the magnetizer can be improved, and the magnetizer can generate larger magnetic induction intensity when the coil is energized with an excitation signal; meanwhile, the iron loss of the magnetizer can be reduced.
In some embodiments, the excitation signal is a pulsed electrical signal.
In this way, by using the pulse electrical signal as the excitation signal, it is advantageous to shorten the time required for the piezoelectric material to be circularly polarized by utilizing the high-frequency characteristics of the pulse electrical signal.
In some embodiments, the waveform of the excitation signal is a unidirectional triangular wave, and the excitation signal satisfies the following conditional expression:
2<a1/a2<5，
wherein a1 is the rising rate of the excitation signal in one period, and a2 is the falling rate of the excitation signal in one period.
Therefore, the waveform of the excitation signal is the unidirectional triangular wave, so that the first annular electric field and the second annular electric field which are different in direction and stable in size can be generated in one period, and the polarization process of the piezoelectric structure is prevented from being influenced by the generated electric fields. By satisfying the above range, the value a1/a2 of the excitation signal is beneficial to shortening the time of the second circular electric field acting on the piezoelectric structure on the basis of ensuring that the intensity of the first circular electric field is greater than that of the second circular electric field, so that the electric domain of the piezoelectric structure turned by the first circular electric field is not offset or turned again by the action of the second circular electric field, and the time required by the piezoelectric structure to be polarized in a circular shape can be shortened.
In some embodiments, the piezoelectric material is a piezoelectric film or a piezoelectric ceramic.
Thus, the piezoelectric film or the piezoelectric ceramic is adopted as the piezoelectric material, so that the piezoelectric material is favorably polarized and has the piezoelectric effect and the inverse piezoelectric effect.
An embodiment of the present application also provides a piezoelectric assembly including a piezoelectric material hoop-polarized by the above-described polarization method of a piezoelectric material.
The piezoelectric component does not need to be printed with electrodes during assembly, and adverse effects on the performance of the piezoelectric component caused by additional mass generated by oxidation of the printed electrodes and printing of the electrodes are avoided. The piezoelectric component does not need to be printed with electrodes or hard integrated with devices, so that the piezoelectric material which is circularly polarized can be replaced at any time after the service life is reached or the piezoelectric material fails; the piezoelectric component can be replaced according to corresponding requirements so as to adapt to different sound wave emission requirements.
In some embodiments, the piezoelectric assembly further includes a coil and a magnetizer, the piezoelectric material is processed into an annular piezoelectric structure, and the piezoelectric structure and the coil are sleeved on the magnetizer at intervals.
Thus, the piezoelectric element can be used to emit sound waves by satisfying the above structure.
In some embodiments, the coil receives an excitation signal that satisfies the following conditional expression:
f is more than or equal to 20KHz, wherein f is the frequency of the excitation signal.
In this manner, the piezoelectric element can be used to emit ultrasonic waves by satisfying the above conditional expressions.
An embodiment of the present application also provides an electrodeless ultrasonic wave emitting device including the piezoelectric assembly as described above.
The piezoelectric component of the electrodeless ultrasonic transmitter does not need to be printed with electrodes during assembly, and the adverse effect of the additional mass generated by the printed electrodes due to oxidation on the performance of the electrodeless ultrasonic transmitter is avoided. The piezoelectric component does not need to be printed with electrodes or integrated with devices hard, so that the piezoelectric component can be replaced at any time after the service life is up to or the piezoelectric component is out of service; the piezoelectric component can be replaced according to corresponding requirements so as to adapt to different sound wave emission requirements.
Drawings
Fig. 1 is a schematic flow chart of a polarization method for a piezoelectric material according to an embodiment of the present disclosure.
Fig. 2 is a schematic waveform diagram of an input excitation signal in a polarization method of a piezoelectric material according to an embodiment of the present application.
Fig. 3 is a schematic waveform diagram of a circumferential electric field generated in a polarization method of a piezoelectric material according to an embodiment of the present application.
Fig. 4 is a schematic structural diagram of a piezoelectric assembly according to an embodiment of the present disclosure.
Fig. 5 is a schematic waveform diagram of an input excitation signal in a piezoelectric element according to an embodiment of the present application.
Fig. 6 is a schematic diagram of a waveform of a hoop electric field generated in a piezoelectric element according to an embodiment of the present application.
Description of the main elements
Detailed Description
Reference will now be made in detail to embodiments of the present application, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative and are only for the purpose of explaining the present application and are not to be construed as limiting the present application.
In the description of the present application, it is to be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the present application and for simplicity in description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed in a particular orientation, and be operated in a particular manner, and are not to be construed as limiting the present application.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.
In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; may be mechanically connected, may be electrically connected or may be in communication with each other; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
Some embodiments of the present application will be described in detail below with reference to the accompanying drawings. The embodiments described below and the features of the embodiments can be combined with each other without conflict.
Referring to fig. 1, fig. 1 is a schematic flow chart of a polarization method for a piezoelectric material according to an embodiment of the present application, for circularly polarizing the piezoelectric material. The polarization method of the piezoelectric material specifically comprises the following steps:
s1: the piezoelectric material is processed to form an annular piezoelectric structure.
In this embodiment, the piezoelectric material may be a piezoelectric film, a piezoelectric ceramic, or other materials having a piezoelectric effect or an inverse piezoelectric effect. The present embodiment is described by taking a piezoelectric film as an example. It is to be understood that this is not a limitation on the embodiments of the application.
The piezoelectric material is processed into an annular piezoelectric structure, namely piezoelectric films meeting the size requirement and the piezoelectric parameter requirement are connected end to form a piezoelectric film ring or a piezoelectric film cylinder. In this embodiment, the piezoelectric structure is a piezoelectric film ring or a piezoelectric film cylinder. The piezoelectric structure can be used for devices having acoustic wave emission requirements, such as acoustic wave emitting devices.
It will be appreciated that in other embodiments, where the piezoelectric material is a piezoelectric ceramic, the piezoelectric structure is a piezoelectric ceramic ring or cylinder.
S2: the piezoelectric structure and a coil are sleeved on a magnetizer at intervals.
In this embodiment, the magnetic conductor is substantially a cylindrical structure. The piezoelectric structure and the coil are sleeved on a magnetizer at intervals, namely the piezoelectric structure and the coil are sleeved on the magnetizer at intervals along the axial direction of the magnetizer, and the piezoelectric structure sleeved on the magnetizer is circularly polarized under the electromagnetic action of the coil and the magnetizer.
In this embodiment, the magnetic conductor is an iron core made of silicon steel sheets.
It is understood that in other embodiments, the magnetizer may be made of any one of pure iron, mild steel, non-silicon steel, iron-nickel alloy, iron-aluminum alloy, amorphous alloy, and microcrystalline alloy.
S3: inputting a periodic excitation signal into the coil, so that a first circumferential electric field E1 and a second circumferential electric field E2 are sequentially generated in the circumferential direction of the magnetizer in each period, and the piezoelectric structure is circularly polarized, wherein the strength of the first circumferential electric field E1 is greater than that of the second circumferential electric field E2, and the direction of the first circumferential electric field E1 is opposite to that of the second circumferential electric field E2.
In this embodiment, the excitation signal is a pulse electrical signal, and the electrical signal may be a current or a voltage, and the present embodiment is described by taking a pulse current I1 as an example.
It is understood that in other embodiments, the excitation signal may be a pulsed voltage.
Referring to fig. 2 and fig. 3 together, fig. 2 is a schematic waveform diagram of an input excitation signal in a polarization method of a piezoelectric material according to an embodiment of the present disclosure, and fig. 3 is a schematic waveform diagram of a circumferential electric field generated in the polarization method of the piezoelectric material according to the embodiment of the present disclosure. In the embodiment, the excitation signal is a pulse current I1, the waveform of the pulse current I1 is a unidirectional triangular wave, and the unidirectional triangular wave can be understood as that the current is from 0 to Imax, and from Imax to 0, and the cycle is repeated; or it can also be understood that the current is cycled from 0 to-Imax, and from-Imax to 0. However, the pulsed electrical signal should be a unidirectional current or a unidirectional voltage. Here, Imax is not an infinite value, that is, the pulse current I1 cannot be infinitely increased in a period of time, and the current is decreased to generate an opposite electric field, so that it is required to ensure that the intensity of the first circumferential electric field E1 generated in each period is greater than the intensity of the second circumferential electric field E2, so that the piezoelectric structure can be circumferentially polarized.
The period T1 of the pulse current I1 is (T1+ T2) s, and the frequency f1 is 1/(T1+ T2) Hz.
In this embodiment, the waveform of the pulse current I1 is a one-way triangle wave, and the pulse current I1 satisfies the following conditional expression: 2< a1/a2< 5. Wherein, a1 is the rising rate of the pulse current I1 in the t1 period, and a2 is the falling rate of the pulse current I1 in the t2 period. Thus, the value of a1/a2 is favorable for shortening the time of the second circumferential electric field E2 acting on the piezoelectric structure on the basis of ensuring that the intensity of the first circumferential electric field E1 is greater than that of the second circumferential electric field E2, so that the electric domain of the piezoelectric structure turned by the first circumferential electric field E1 is not offset or turned again by the action of the second circumferential electric field E2. However, when the value of a1/a2 is less than 2, the strength of the first circumferential electric field E1 is close to that of the second circumferential electric field E2, or the strength of the first circumferential electric field E1 is less than that of the second circumferential electric field E2, wherein when the strength of the first circumferential electric field E1 is close to that of the second circumferential electric field E2, the electric domain of the piezoelectric structure turned by the first circumferential electric field E1 may be offset by the action of the second circumferential electric field E2; when the intensity of the first circumferential electric field E1 is smaller than the intensity of the second circumferential electric field E2, the electric domain of the piezoelectric structure that is turned by the first circumferential electric field E1 may turn due to the effect of the second circumferential electric field E2, and after entering the next period, the electric domain that has been turned by the second circumferential electric field E2 may be turned again by the first circumferential electric field E2, so that the piezoelectric structure cannot have a stable turned electric domain, and the circumferential polarization of the piezoelectric structure cannot be guaranteed. When the value of a1/a2 is larger than 5, the time of the second ring-direction electric field E2 acting on the piezoelectric structure is longer, which is not beneficial to shortening the time of the ring-direction polarization of the piezoelectric structure.
In this embodiment, the frequency f1 is greater than or equal to 20 KHz. In this manner, the time required for the piezoelectric material to be ring-polarized can be shortened.
In this embodiment, the pulse current I1 is a changing current, and inputting the changing current into the coil causes the magnetizer to generate a changing magnetic flux along the axial direction, and the changing magnetic flux causes the circumferential direction of the magnetizer to generate an annular electric field perpendicular to the axial direction of the magnetizer, and the strength and the direction of the annular electric field are determined according to the changing rate of the magnetic flux.
Specifically, during the time period t1, the increasing rate a1 of the current is relatively very fast, which results in a rapidly increasing magnetic flux in the magnetizer during the time period t1, the magnetic flux changes such that a first circumferential electric field E1 is generated in the circumferential direction of the magnetizer, and the piezoelectric structure is circumferentially polarized in the direction of the first circumferential electric field E1 under the action of the first circumferential electric field E1. When the increasing rate a1 of the current is reduced to 0, that is, the current reaches the maximum value (for example, Imax) in the time period t1, the magnetic flux does not increase any more in the time period t1, and the ring polarization of the piezoelectric structure in the time period t1 ends and starts to enter the time period t 2.
In the t2 time period, the rate of decrease of the current, a2, is slower relative to the rate of increase of the current, a1, in the t1 time period, i.e., a2< a1, where a1/a2 is 3. the current decreases relatively slowly during the time period t2, when the magnetic flux in the magnetizer will decrease, when the magnetic flux is still changing, the magnetic flux changes to make the circumferential direction of the magnetizer generate the second circumferential electric field E2 opposite to the direction of the first circumferential electric field E1.
In this embodiment, since the decreasing rate a2 of the current in the t2 period is very slow relative to the increasing rate a1 of the current in the t1 period, the rate of change of the decrease of the magnetic flux in the t2 period is small, the electric field strength of the generated second circumferential electric field E2 is low, and the electric field strength of the second circumferential electric field E2 is smaller than the electric field strength of the first circumferential electric field E2, that is, the strength of the first circumferential electric field E1 is greater than the strength of the second circumferential electric field E2.
According to the law of electromagnetic induction, by adjusting the increasing rate a1 of the pulse current I1 in the time period t1, the changing rate of the increase of the magnetic flux is correspondingly adjustable, and the strength of the generated first annular electric field E1 is correspondingly adjustable; by adjusting the rate of decrease a2 of the pulsed current over the time period t2, the rate of change of the magnetic flux decrease is also correspondingly adjustable, as is the strength of the second circular electric field E2 that it produces. The piezoelectric structure can be circularly polarized through the interaction of the first circular electric field E1 and the second circular electric field E2. However, it is still required to satisfy that the intensity of the first circumferential electric field E1 is greater than that of the second circumferential electric field E2, i.e. it can be understood that the increasing rate a1 of the current or voltage in the t1 period is greater than the decreasing rate a2 of the current or voltage in the t2 period.
In this embodiment, the electric field intensity of the second circumferential electric field E2 is smaller than the coercive field of the piezoelectric structure, that is, it can be ensured that the electric domain of the piezoelectric structure that has been turned by the first circumferential electric field E1 is not cancelled by the second circumferential electric field E2, so that the piezoelectric structure is circularly polarized.
It should be noted that the coercive field is one of the characteristics of a magnetic material, such as a piezoelectric material and a magnetizer, and refers to the magnetic field strength required for reducing the magnetization of the magnetic material to zero after the magnetic material is magnetized to magnetic saturation. In this embodiment, the first circumferential electric field E1 magnetizes the piezoelectric structure, so that the annular piezoelectric mechanism generates a coercive field when being circularly polarized by the second circumferential electric field E2, and the electric field strength of the second circumferential electric field E2 is smaller than the strength of the coercive field of the piezoelectric structure, thereby ensuring that the piezoelectric structure is always in the process of being circularly polarized by the circumferential electric field in one direction. After one or more periods T1, the piezoelectric structure is always in the process of being hoop polarized by a ring-shaped electric field in one direction, so that the piezoelectric structure is hoop polarized.
It should be noted that an electric domain exists in a ferroelectric (for example, a piezoelectric structure), and the electric domain means that energy is increased when the ferroelectric is spontaneously polarized, a state is unstable, a crystal tends to be divided into a plurality of small regions, electric dipoles of each small region are along the same direction, directions of electric dipoles of different small regions are different, each small region is an electric domain, and a boundary region between electric domains becomes a domain wall. The factors that determine the thickness of the domain wall are a result of various energy balances. Under the action of an external electric field (e.g. the first circumferential electric field E1), the electric domains tend to align with the external electric field, which is called domain steering. The domain turning is realized by the appearance and development of a new domain and the movement of a domain wall, after an external electric field is removed, a small part of electric domain deviates from the polarization direction and returns to the original position, and a large part of electric domain stays in the polarization direction of the new turning, so that residual polarization is generated. When a reverse electric field (for example, the second circumferential electric field E2) is added, the remanent polarization may be cancelled, and according to the law of electromagnetism, the electric field strength required for cancelling the remanent polarization may be understood as the strength of the coercive field, and the electric field strength of the second circumferential electric field E2 is smaller than that of the coercive field of the piezoelectric structure, that is, it is ensured that the electric domain, to which the piezoelectric structure has been turned by the first circumferential electric field E1, is not cancelled by the second circumferential electric field E2, so that the piezoelectric structure is circularly polarized.
It is understood that, in other embodiments, the directions of the first circumferential electric field E1 and the second circumferential electric field E2 may be changed accordingly, however, the electric field strength of the first circumferential electric field E1 is still required to be larger than that of the second circumferential electric field E2.
In some embodiments, inputting a periodic excitation signal into the coil, so that the circumferential direction of the magnetizer generates a first circumferential electric field and a second circumferential electric field sequentially in each period, and the step of circumferentially polarizing the piezoelectric structure further includes:
the piezoelectric structure is circularly polarized over a plurality of cycles.
In this embodiment, the conventional periodic pulse current I1 can be used, and the pulse current I1 does not need to be designed additionally. In each period, the piezoelectric structure is circularly polarized, but the polarization requirement cannot be met in one period, and the piezoelectric structure can be jointly acted on by utilizing the circular polarization effect of a plurality of periods, so that the piezoelectric structure is circularly polarized under the joint action of the plurality of periods.
In some embodiments, inputting a periodic excitation signal into the coil, so that the circumferential direction of the magnetizer generates a first circumferential electric field and a second circumferential electric field in sequence in each period, and the step of circumferentially polarizing the piezoelectric structure further includes:
the piezoelectric structure is circularly polarized in one period.
In this embodiment, the time of the first toroidal electric field E1 acting on the piezoelectric structure is increased by increasing the time t1 and increasing the rate a1 until the piezoelectric structure reaches the polarization requirement; then, at the time of increasing t2 and the rate of decreasing a2, the generated second circumferential electric field E2 is far smaller than the first circumferential electric field E1, i.e. it can be ensured that the electric domain of the piezoelectric structure that has been turned by the first circumferential electric field E1 is not cancelled by the second circumferential electric field E2, so that the piezoelectric structure is circularly polarized in one period. The embodiment needs additional design of pulse current or annular polarization of piezoelectric materials with low polarization requirements.
Fig. 1 to 3 describe in detail a polarization method of a piezoelectric material of the present application, by which circular polarization, which cannot be achieved by a conventional polarization method (corona polarization, in-situ polarization, direct polarization of an oil bath electrode), can be achieved. In the process of circumferential polarization of the piezoelectric structure, electrodes do not need to be printed on the piezoelectric structure, and adverse effects on the performance of the piezoelectric structure caused by oxidation of the printed electrodes and additional mass generated by printing the electrodes are avoided.
Referring to fig. 4, fig. 4 is a schematic structural diagram of a piezoelectric device according to an embodiment of the present disclosure. The piezoelectric element 100 includes a piezoelectric structure 10, a coil 20, and a magnetizer 30, which are processed into a ring shape, and the piezoelectric structure 10 is formed by forming a ring shape of a piezoelectric material which is circularly polarized by the above-mentioned polarization method of the piezoelectric material.
When the piezoelectric assembly 100 is assembled, the piezoelectric structure 10 and the coil 20 are sleeved on the magnetizer 30, and the piezoelectric structure 10 does not need to print electrodes, thereby avoiding adverse effects on the performance of the piezoelectric structure 10 caused by additional mass generated by the printed electrodes due to oxidation of the printed electrodes.
It should be noted that the coil 20 and the magnetizer 30 used in the piezoelectric assembly may be the same as or different from those used in the polarization method of the piezoelectric material, and the present application is not limited herein.
Referring to fig. 5 and fig. 6 together, fig. 5 is a schematic waveform diagram of an excitation signal input by the piezoelectric element 100 according to an embodiment of the present disclosure, and fig. 6 is a schematic waveform diagram of a circumferential electric field generated in the piezoelectric element 100 according to an embodiment of the present disclosure. In this embodiment, the excitation signal is a pulse current I2, the waveform of the pulse current I2 is a unidirectional triangular wave, the period T2 of the pulse current I2 is (T3+ T4) s, and the frequency f2 is 1/(T3+ T4) Hz.
In use of the piezoelectric assembly 100, the coil 20 receives a periodic pulsed current I2.
In a period t3, the increase rate a3 of the current is smaller than the increase rate a1 in a period t1 when the piezoelectric structure 10 is hoop polarized, that is, the corresponding magnetic flux change rate is relatively slow in a period t3, and the correspondingly generated third hoop electric field E3 causes the piezoelectric structure 10 to generate an inverse piezoelectric effect along the direction of the third hoop electric field E3, and deformation occurs in the polarization direction under the induction of the third hoop electric field E3, which is expressed as an increase or decrease in the diameter of the piezoelectric structure 10.
In the period t4, the decreasing rate a4 of the current is consistent with the increasing rate a3 of the current in the period t3, that is, a3 is a4, and correspondingly, a fourth ring electric field E4 with the same direction and the same magnitude as the third ring electric field E3 is generated in the period t4, so that the piezoelectric structure 10 generates deformation in the direction opposite to the period t3, and the diameter of the piezoelectric structure 10 is reduced or increased.
During a period T2 of (T3+ T4), the deformation of the piezoelectric structure 10 appears as an increase-decrease or decrease-increase in the diameter of the piezoelectric structure 10, i.e., the diameter of the piezoelectric structure 10 periodically increases or decreases, causing respiratory vibration, thereby enabling the piezoelectric structure 10 to emit sound waves.
In this embodiment, the frequency f2 of the pulse current I2 satisfies the following conditional expression: f2 is more than or equal to 20KHz, and can control the piezoelectric component 100 to emit ultrasonic waves.
It is understood that in other embodiments, by controlling the frequency f2 of the pulse current I2, the frequency of the sound wave emitted by the piezoelectric assembly 100 can be controlled, for example, the frequency f2 of the pulse current I2 is reduced, so that the frequency f2 is less than or equal to 20KHz, and the normal sound wave emitted by the piezoelectric assembly 100 can be controlled. By controlling the rate a at which the pulse current I2 increases and decreases, the amount of deformation and amplitude in the diameter direction of the piezoelectric structure 10 can be controlled, however, the rate a3 at which the pulse current I2 increases during the t3 period and the rate a4 at which the pulse current I4 decreases remain the same.
It is understood that in other embodiments, the piezoelectric structure 10 does not need to be printed with electrodes, and does not need to be hard-integrated with the device, so that the piezoelectric structure 10 can be separated and replaced in the piezoelectric assembly 100, so that the piezoelectric assembly 100 can emit sound waves in different frequency bands to meet more use requirements.
An embodiment of the present application provides an electrodeless ultrasonic wave emitting device (not shown) for emitting an acoustic wave, including the piezoelectric assembly 100 as described above. By controlling the frequency f2 of the pulse current, it is possible to transmit ultrasonic waves. The electrodeless ultrasonic wave emitting device may be a cellular phone.
It is understood that in other embodiments, the electrodeless ultrasonic wave emitting device may also be a device capable of emitting sound waves or ultrasonic waves, such as a tablet computer, a camera, a cooking device, an audio device, a distance measuring device, a positioning device, an acoustic device, and the like.
It will be evident to those skilled in the art that the present application is not limited to the details of the foregoing illustrative embodiments, and that the present application may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present application and not for limiting, and although the present application is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present application without departing from the spirit and scope of the technical solutions of the present application.
Claims (10)
1. A method of poling a piezoelectric material, comprising the steps of:
processing the piezoelectric material to form an annular piezoelectric structure;
sleeving the piezoelectric structure and a coil on a magnetizer at intervals; and
inputting a periodic excitation signal into the coil, so that a first annular electric field and a second annular electric field are sequentially generated in the circumferential direction of the magnetizer in each period, and the piezoelectric structure is circularly polarized, wherein the strength of the first annular electric field is greater than that of the second annular electric field, and the direction of the first annular electric field is opposite to that of the second annular electric field.
2. The method for polarizing a piezoelectric material according to claim 1, wherein the step of inputting a periodic excitation signal into the coil so that the circumferential direction of the magnetizer generates a first circumferential electric field and a second circumferential electric field sequentially in each period, so that the piezoelectric structure is circularly polarized further comprises:
the piezoelectric structure is circularly polarized over one or more cycles.
3. The method for polarizing a piezoelectric material according to claim 1, wherein the magnetic conductor is any one of a silicon steel sheet, pure iron, mild steel, non-silicon steel, iron-nickel alloy, iron-aluminum alloy, amorphous alloy, and microcrystalline alloy.
4. The method of poling piezoelectric material of claim 1, wherein the excitation signal is a pulsed electrical signal.
5. The polarization method of a piezoelectric material according to claim 4, wherein the waveform of the excitation signal is a one-way triangular wave, and the excitation signal satisfies the following conditional expression:
2<a1/a2<5，
wherein a1 is the rising rate of the excitation signal in one period, and a2 is the falling rate of the excitation signal in one period.
6. A polarization method of a piezoelectric material according to claim 1, wherein the piezoelectric material is a piezoelectric film or a piezoelectric ceramic.
7. A piezoelectric assembly comprising a piezoelectric material hoop-polarized by a polarization method of the piezoelectric material according to any one of claims 1 to 6.
8. The piezoelectric assembly of claim 7, further comprising a coil and a magnetic conductor, wherein the piezoelectric material is formed into an annular piezoelectric structure, and the piezoelectric structure and the coil are disposed on the magnetic conductor in a spaced manner.
9. The piezoelectric assembly of claim 8, wherein the coil receives an excitation signal that satisfies the following condition:
f is more than or equal to 20KHz, wherein f is the frequency of the excitation signal.
10. An electrodeless ultrasonic wave emitting device comprising the piezoelectric module as defined in any one of claims 7 to 9.
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