Patent Application
20240364239
The present disclosure relates to a technical field of piezoelectric drive, and more particularly to a piezoelectric drive device and a piezoelectric drive system having the same.
In the related art, a piezoelectric drive system generally has two types. One is USM type, and the other one is SIDM type. The piezoelectric drive system of the USM type is complicated and expensive, and the generated stroke is very small. On the other hand, the piezoelectric drive system of the SIDM type needs a weight and a shaft, and thus has a complicated structure. Further, the control method of the piezoelectric drive system of the SIDM type is very difficult, as a deformation speed of a piezoelectric element needs to be controlled accurately.
As such, it is necessary to propose a piezoelectric drive device and a piezoelectric drive system so as to solve at least one of the above technical problems in the related art.
To this end, embodiments of a first aspect the present disclosure provide a piezoelectric drive device, including: a case defining a cavity therein, the case having a closed end and an open end; a holder arranged in the cavity, and having a first end coupled to the closed end of the case, and a second end facing towards the open end of the case, the second end of the holder having a recess in an end face thereof, the recess including a first side wall, a second side wall and a bottom connected between the first side wall and the second side wall, the first side wall and the second side wall obliquely extending outwards from the bottom; a first piezoelectric element and a second piezoelectric element arranged on the first side wall and the second side wall of the recess, respectively, the first piezoelectric element being configured to expand or shrink in a direction perpendicular to the first side wall of the recess when powered on or off, the second piezoelectric element being configured to expand or shrink in a direction perpendicular to the second side wall of the recess when powered on or off; and a first actuating member and a second actuating member fixed to the first piezoelectric element and the second piezoelectric element, respectively, and facing towards each other.
Embodiments of a second aspect of the present disclosure further provide a piezoelectric drive system, including: a piezoelectric drive device; and a movable member arranged under the piezoelectric drive device. The piezoelectric drive device includes: a case defining a cavity therein, the case having a closed end and an open end; a holder arranged in the cavity, and having a first end coupled to the closed end of the case, and a second end facing towards the open end of the case, the second end of the holder having a recess in an end face thereof, the recess including a first side wall, a second side wall and a bottom connected between the first side wall and the second side wall, the first side wall and the second side wall obliquely extending outwards from the bottom; a first piezoelectric element and a second piezoelectric element arranged on the first side wall and the second side wall of the recess, respectively, the first piezoelectric element being configured to expand or shrink in a direction perpendicular to the first side wall of the recess when powered on or off, the second piezoelectric element being configured to expand or shrink in a direction perpendicular to the second side wall of the recess when powered on or off; a first actuating member and a second actuating member fixed to the first piezoelectric element and the second piezoelectric element, respectively, and facing towards each other; and a retaining member. The movable member is configured to be fitted with the first actuating member or the second actuating member of the piezoelectric drive device. The retaining member is configured to retain the first actuating member or the second actuating member against the movable member, and the movable member is configured to move under the drive of the first actuating member or the second actuating member.
The above and/or additional aspects and advantages of the present disclosure will become apparent and easy to understand from descriptions of embodiments in connection with following drawings.
Embodiments of the present disclosure are described in detail below, and examples of the embodiments are shown in the drawings. Same or similar reference numerals from beginning to end indicate same or similar elements or elements having same or similar functions. The embodiments described below with reference to the attached drawings are exemplary and are only intended to interpret the present disclosure and cannot be understood as a limitation to the present disclosure.
In the description of the present disclosure, it is should be understood that the orientation or position relationships indicated by the terms “central”, “up”, “down”, “front”, “rear”, “vertical”, “horizontal”, “top”, “bottom”, “inner”, “outer”, “axial”, “radial” and “circumferential” are based on the orientation or position relationships shown in the attached drawings, only for the convenience of describing the present disclosure and simplifying the description, instead of indicating or implying that the device or element referred to must have a specific orientation and be constructed and operated in a specific orientation, and thus cannot be understood as a limitation of the present disclosure.
A piezoelectric drive device 100 and a piezoelectric drive system 1000 according to embodiments of the present disclosure will be described with reference to the drawings. The piezoelectric drive device 100 can be used in the piezoelectric drive system 1000.
As shown in
In some embodiments of the present disclosure, as shown in
It should be noted that “up”, “down”, “front”, “rear”, “left” and “right” are used herein to indicate the orientation in the drawings and intended for easy understanding of the present disclosure, but should not be interpreted as a limitation to the present disclosure.
In the piezoelectric drive device according to the embodiments of the present disclosure, when the first or second piezoelectric element 5 or 6 is powered on, the first or second piezoelectric element 5 or 6 will expand in the direction perpendicular to the first or second side wall 41 or 42 of the recess, so as to drive the first or second actuating part 7 or 8 to move in the same direction, and thus the first or second actuating part 7 or 8 can be fitted with a movable member 200 of the piezoelectric drive system 1000 to drive the movable member 200 to move in a desired direction. Further, when the first or second piezoelectric element 5 or 6 is powered off, the first or second piezoelectric element 5 or 6 will shrink in the direction perpendicular to the first or second side wall 41 or 42 of the recess, and hence the first or second actuating part 7 or 8 will also restore to its initial position without influence on the movable member 200. As repeated in this manner, the movable member 200 can move continuously in the desired direction.
Consequently, the piezoelectric drive device 100 according to the embodiments of the present disclosure has advantages of a simple structure, a precise drive stroke, a strong drive force and a high energy conversion efficiency.
Further, since the first piezoelectric element 5 is adhered to the first side wall 41 of the recess and the first actuating member 7 by hard glue, and the second piezoelectric element 6 is adhered to the second side wall 42 of the recess and the second actuating member 8 by hard glue, the connection between the first piezoelectric element 5 and the first side wall 41 of the recess, the connection between the first piezoelectric element 5 and the first actuating member 7, the connection between the second piezoelectric element 6 and the second side wall 42 of the recess, and the connection between the second piezoelectric element 6 and the second actuating member 8 are firm and stable, and the hard glue tends not to absorb the expansion of the first piezoelectric element 5 and the second piezoelectric element 6, so that the first piezoelectric element 5 and the second piezoelectric element 6 can expand to drive the first actuating member 7 and the second actuating member 8 to move reliably and efficiently.
In addition, since the first piezoelectric element 5 is adhered to the first side wall 41 of the recess by hard glue and the second piezoelectric element 6 is adhered to the second side wall 42 of the recess by hard glue, when the first piezoelectric element 5 is powered on to expand along the direction perpendicular to the first side wall 41 of the recess, the first side wall 41 of the recess will restrict the movement of the left end of the first piezoelectric element 5, so that the right end of the first piezoelectric element 5 will expand along the direction perpendicular to the first side wall 41 of the recess, and thus the first actuating member 7 is driven to move accordingly. Similarly, when the second piezoelectric element 6 is powered on to expand along the direction perpendicular to the second side wall 42 of the recess, the second side wall 42 of the recess will restrict the movement of the right end of the second piezoelectric element 6, so that the left end of the second piezoelectric element 6 will expand along the direction perpendicular to the second side wall 42 of the recess, and thus the second actuating member 8 is driven to move accordingly.
In some embodiments of the present disclosure, the piezoelectric drive device 100 further includes a retaining member 2 and a shaft 3. The retaining member 2 is arranged in the cavity 13, and has a first end abutting against the closed end of the case 1 and a second end opposite to the first end. The shaft 3 is arranged in the cavity 13 and fitted with the second end of the retaining member 2, and the shaft 3 is configured to move under the action of the retaining member 2. The first end of the holder 4 is fixed to the shaft 3 and abuts against the second end of the retaining member 2.
Specifically, as shown in
In some embodiments of the present disclosure, the case 1 at least includes two opposite side walls, each side wall has an opening 11, the openings 11 of the two opposite side walls of the case 1 are aligned with each other, two ends of the shaft 3 are received in the openings 11 of the two opposite side walls of the case 1, respectively, and the shaft 3 is configured to move within the openings 11 under the action of the retaining member 2.
As shown in
For example, the retaining member 2 may be made of elastic materials, such as rubber, and should be mounted in the cavity 13 of the case 1 in a compressed state, so that the retaining member 2 can apply an elastic force of about 200 mN to the shaft 3 when the shaft 3 is inserted into the case 1 through the openings 11 and fitted with the retaining member 2. Further, since the holder 4 is fixed to the shaft 3 and the upper end of the holder 4 abuts against the lower end of the retaining member 2, the holder 4 is also subject to the elastic force of the retaining member 2. In this way, when the movable member 200 tends to move downwards, the retaining member 2 will push the shaft 3 and the holder 4 to move downwards along the openings 11, and hence the first and second piezoelectric elements 5, 6 and the first and second actuating member 7, 8 will also move downwards, so that the first and second actuating member 7, 8 can maintain a contact with and be fitted with the movable member 200.
Similarly, since the retaining member 2 has elasticity and can be further compressed, when the movable member 200 moves upwards, the first and second piezoelectric elements 5, 6 and the first and second actuating member 7, 8 will be driven by the movable member 200 to move upwards, and hence the shaft 3 and the holder 4 will also move upwards along the openings 11. In this process, the first and second actuating member 7, 8 maintain a contact with and are fitted with the movable member 200.
Thus, the piezoelectric drive device 100 according to the embodiments of the present disclosure may adapt to various vertical position changes of the movable member 200, so as to be stably fitted with the movable member 200, thus driving the movable member 200 to move smoothly and reliably.
In addition, the opening 11 may be centered horizontally, that is, positioned in a horizontal center of the front or rear side wall of the case 1, so that the shaft 3 passing through the opening 11 and the holder 4 fixed to be shaft 3 can also be centered horizontally.
Further, end faces of the two ends of the shaft 3 are flush with outer surfaces of the two opposite side walls of the case 1, respectively. Specifically, as shown in
In some embodiments of the present disclosure, each opening 11 has two arc ends matching with a shape of the end of the shaft 3 and configured to be fitted with the end of the shaft 3. For example, as shown in
Moreover, the second end of the retaining member 2 has a first groove 21 parallel to the shaft 3, and the shaft 3 is at least partially fitted in the first groove 21. For example, as shown in
Further, the first end of the holder 4 has a second groove 46 parallel to the shaft 3, and the shaft 3 is at least partially fitted in and is fixed in the second groove 46. For example, as shown in
The first groove 21, the shaft 3 and the second groove 46 are aligned with one another in a direction from the closed end to the open end of the case 1, each of the first groove 21 and the second groove 46 has a cross section of an arc shape matching with the shaft 3, and the first groove 21 and the second groove 46 enclose a periphery of the shaft 3.
Specifically, as shown in
In this way, the shaft 3 can be clamped between the retaining member 2 and the holder 4 stably, and the retaining member 2 can have a relatively large contact area with the holder 4, so that the retaining member 2 can drive the shaft 3 and the holder 4 to move smoothly.
In some other embodiments of the present disclosure, the openings 11 may not be provided in the front and rear side walls of the case 1. Instead, slots may be formed in inner surfaces of the front and rear side walls of the case 1, respectively, and the slot extends to the lower end of the case 1, so that the shaft 3 can be mounted into the case 1 through the slot, fitted in the slot and even moved within the slot. Thus, the retaining member 2 can drive the shaft 3 and the holder 4 to move up and down within the slots, just as described above.
In some other embodiments of the present disclosure, the shaft 3 and the opening 11 may not be provided, and only the retaining member 2 is clamped between the upper end of the case 1 and the holder 4. In this case, the retaining member 2 may be a block of rubber or a spring in a compressed state, so that it can drive the holder 4 to move up and down, just as described above.
In some other embodiments of the present disclosure, the retaining member 2, the shaft 3 and the opening 11 may not be provided, the holder 4 directly abuts against the upper end of the case 1 and the case 1 itself has certain elasticity. For example, the upper end of the case 1 is elastically deformed to always apply a downward force to the holder 4, so that the holder 4 can be driven to move up and down, just as described above.
In some embodiments of the present disclosure, the bottom 43 of the recess includes a first section 431, a second section 432 and a third section 433, the first section 431 is connected to the first side wall 41, the second section 432 is connected to the second side wall 42, and the third section 433 is connected between the first section 431 and the second section 432. For example, as shown in
Further, the first section 431 is fitted with the first piezoelectric element 5, and the second section 432 is fitted with the second piezoelectric element 6. That is, the first piezoelectric element 5 is in a contact with the first section 431, but is not fixed to the first section 431, and the second piezoelectric element 6 is in a contact with the second section 432, but is not fixed to the second section 432. In this way, when the first or second piezoelectric element 5 or 6 expands or shrinks, the first or second piezoelectric element 5 or 6 will not interfere with the first section 431 or the second section 432, so that the first or second piezoelectric element 5 or 6 can expand or shrink smoothly.
Furthermore, the first piezoelectric element 5 matches with the first side wall 41 and the first section 431 of the recess in shape and orientation, respectively, and the second piezoelectric element 6 matches with the second side wall 42 and the second section 432 of the recess in shape and orientation, respectively. For example, the first piezoelectric element 5 has a flat surface parallel with a flat surface of the first side wall 41 and another flat surface parallel with a flat surface of the first section 431, and the second piezoelectric element 6 has a flat surface parallel with a flat surface of the second side wall 42 and another flat surface parallel with a flat surface of the second section 432.
In this way, the first piezoelectric element 5 can have a stable connection with the first side wall 41 and also have a smooth fit with the first section 431, and the second piezoelectric element 6 can have a stable connection with the second side wall 42 and also have a smooth fit with the second section 432. Thus, the first piezoelectric element 5 can expand or shrink stably and smoothly in the direction perpendicular to the first side wall 41, and the second piezoelectric element 6 can expand or shrink stably and smoothly in the direction perpendicular to the second side wall 42.
For example, as shown in
That is, the first piezoelectric element 5 has two orthogonal surfaces which are fixed to the first side wall 41 and fitted with the first section 431, respectively, and the second piezoelectric element 6 has two orthogonal surfaces which are fixed to the second side wall 42 and fitted with the second section 432, respectively.
In this way, the first piezoelectric element 5 can expand or shrink stably and smoothly in the direction perpendicular to the first side wall 41 under the guide of the first section 431, and the second piezoelectric element 6 can expand or shrink stably and smoothly in the direction perpendicular to the second side wall 42 under the guide of the second section 432.
In some embodiments of the present disclosure, a first transition part 44 is provided at a joint of the first side wall 41 and the first section 431 of the recess, and a second transition part 45 is provided at a joint of the second side wall 42 and the second section 432 of the recess. For example, each of the first transition part 44 and the second transition part 45 may be a groove having an arc cross section, which avoids a local stress concentration. It should be noted that the groove extends in a direction perpendicular to a paper surface of
Moreover, the holder 4 may be solid or hollow, which is not limited herein, as long as the holder 4 has the above structures and provides a desired rigidity. For example, in some embodiments of the present disclosure, the holder 4 is hollow, that is, the holder 4 is formed by bending a single sheet and connecting its head to its tail, or by connecting multiple sheets end to end.
In some embodiments of the present disclosure, as shown in
Further, the first included angle α ranges from 24 degrees to 25 degrees, and the second included angle β ranges from 24 degrees to 26 degrees.
For example, the first included angle α may be 24 degrees, 24.5 degrees, 25 degrees, 25.5 degrees or 26 degrees, and the second included angle β may be 24 degrees, 24.5 degrees, 25 degrees, 25.5 degrees or 26 degrees.
In some embodiments of the present disclosure, the first included angle α is 25 degrees, and the second included angle β is 25 degrees.
Since the first included angle α and the second included angle β range from 24 degrees to 26 degrees, the movable member 200 of the piezoelectric drive system 1000 can be moved stably and smoothly, and the piezoelectric drive device 100 can achieve a high drive efficiency.
Moreover, the first piezoelectric element 5 is symmetrical with the second piezoelectric element 6, and the first included angle α is equal to the second included angle β.
Thus, the whole structure of the piezoelectric drive device 100 is stable and has a high strength, so that the movable member 200 of the piezoelectric drive system 1000 can be driven to move smoothly and stably.
In some embodiments of the present disclosure, the first piezoelectric element 5 and the second piezoelectric element 6 are configured to operate in a d33 mode, so as to provide a large expanding force, such as about 500 mN. Herein, the d33 mode means that a piezoelectric material has a polarization direction and a deformation direction which are the same. In other words, the polarization direction of the first piezoelectric element 5 is consistent with the deformation direction of the first piezoelectric element 5, and both directions are perpendicular to the firs side wall 41 of the recess. Similarly, the polarization direction of the second piezoelectric element 5 is consistent with the deformation direction of the second piezoelectric element 5, and both directions are perpendicular to the second side wall 42 of the recess.
Further, the first piezoelectric element 5 and the second piezoelectric element 6 operating in the d33 mode can have a high energy conversion efficiency.
In some embodiments of the present disclosure, the first piezoelectric element 5 includes a plurality of stacked layers and the second piezoelectric element 6 includes a plurality of stacked layers in a direction perpendicular to paper surfaces of
In some embodiments of the present disclosure, each of the first actuating member 7 and the second actuating member 8 has a first end adjacent to the holder 4 and a second end away from the holder 4. The first end of the first actuating member 7 is spaced apart from the first end of the second actuating member 8, the second end of the first actuating member 7 protrudes beyond the first piezoelectric element 5 in a direction facing away from the holder 4, and the second end of the second actuating member 8 protrudes beyond the second piezoelectric element 6 in the direction facing away from the holder 4.
For example, as shown in
In some embodiments of the present disclosure, the lower end of the first actuating member 7 and the lower end of the second actuating member 8 each have a spherical-segment shape, so that the first actuating member 7 and the second actuating member 8 can have a stable contact with the movable member 200, thus ensuring the stable movement of the movable member 200.
In some embodiments of the present disclosure, the piezoelectric drive device 100 further includes a flexible printed circuit board 9 electrically connected to the first piezoelectric element 5 and the second piezoelectric element 6, and configured to power on or off the first piezoelectric element 5 and the second piezoelectric element 6. Further, the flexible printed circuit board 9 is arranged in the cavity 13 of the case 1 and clamped between a side wall of the case 1 and the holder 4.
For example, as shown in
When two flexible printed circuit boards 9 are provided, the two flexible printed circuit boards 9 are configured to power on or off the first piezoelectric element 5 and the second piezoelectric element 6 independently. When only one flexible printed circuit board 9 is provided, the only one flexible printed circuit board 9 is configured to power on or off the first piezoelectric element 5 and the second piezoelectric element 6 independently.
Furthermore, the flexible printed circuit board 9 has a first end received within the cavity 13 of the case 1 and a second end protrudes out of the cavity 13 of the case 1. The first end of the flexible printed circuit board 9 is flush with the first end of the holder 4, and has a first notch 91 fitted with the shaft 3. The second end of the flexible printed circuit board 9 includes two legs 92 spaced apart from each other to expose at least a part of the recess.
For example, as shown in
Moreover, the leg 92 of the flexible printed circuit board 9 may be bent to be horizontal after protruding out of the cavity 13 of the case 1, so as to be connected with an external power source for providing power to the first piezoelectric element 5 and the second piezoelectric element 6.
In some embodiments of the present disclosure, the piezoelectric drive device 100 further includes a pad 10 arranged in the cavity 13 of the case 1 and clamped between the flexible printed circuit board 9 and the side wall of the case 1.
For example, as shown in
Further, the pad 10 has an end flush with the first end of the holder 4, and the end of the pad 10 has a second notch 101 fitted with the shaft 3.
For example, as shown in
In some embodiments of the present disclosure, each of the first actuating member 7 and the second actuating member 8 may be made of ceramic materials. The ceramic materials have a great wear resistance, so that the first actuating member 7 and the second actuating member 8 have a long service life.
In some embodiments of the present disclosure, the case 1 is fixed according to actual requirements. For example, the case 1 may be provided with a flange surrounding at least a part of its outer peripheral surface, and the flange is fixed to a fixed external part by a screw or a bolt.
Embodiments of the present disclosure further provide a piezoelectric drive system 1000, as shown in
In some embodiments of the present disclosure, when an outer peripheral surface of the movable member 200 is flat, the first actuating member 7 and the second actuating member 8 will drive the movable member 200 to translate; when the outer peripheral surface of the movable member 200 is curved, the first actuating member 7 and the second actuating member 8 will drive the movable member 200 to rotate.
The working process of the piezoelectric drive system 1000 is briefly described below by taking the first piezoelectric element 5 as an example.
When powered on, the first piezoelectric element 5 expands along the direction perpendicular to the first side wall 41 of the recess. During the expanding process, since the left end of the first piezoelectric element 5 is restricted by the first side wall 41 of the recess, the right end of the piezoelectric element 5 expands rightwards and downwards, and then the first actuating member 7 is driven to move rightwards and downwards. The first actuating member 7 abuts against the movable member 200 and applies a driving force to the movable member 200. The driving force applied by the first actuating member 7 has a rightward component and a downward component. Thus, the movable member 200 is driven to move rightwards. For example, the movable member 200 can be driven to move 40 nm precisely at one stroke.
When powered off, the first piezoelectric element 5 shrinks, thereby driving the first actuating member 7 to move leftwards and upwards. Since the direction perpendicular to the first side wall 41 of the recess has the first included angle α ranging from 24 degrees to 26 degrees with the plane where the end face of the upper end of the holder 4 is, the first actuating member 7 moving leftwards and upwards cannot apply a driving force to the movable member 200. When viewed microscopically, the first actuating member 7 moving leftwards and upwards is even separated from the movable member 200. Thus, the movable member 200 does not move together with the first actuating member 7 and still remains in its position. In this way, the piezoelectric drive system 1000 has completed a movement cycle. A periodic pulse signal may be applied to the first piezoelectric element 5, and thus the first piezoelectric element 5 can alternately complete the movements of expanding when powered on and shrinking when powered off. As the movement cycle is repeated, the movable member 200 will move rightwards continuously under the drive of the first actuating member 7.
The working process of the second piezoelectric element 5 is substantially the same with that of the first piezoelectric element 6. The difference is that a moving direction of the movable member 200 when the first piezoelectric element 5 operates is opposite to a moving direction of the movable member 200 when the second piezoelectric element 6 operates. For example, the first piezoelectric element 5 drives the movable member 200 to move rightwards, and the second piezoelectric element 6 drives the movable member 200 to move leftwards. In some other embodiments of the present disclosure, the first piezoelectric element 5 may drive the movable element 200 to move clockwise, and the second piezoelectric element 6 may drive the movable element 200 to move counterclockwise. Moreover, in the same time period, only one of the first piezoelectric element 5 and the second piezoelectric element 6 operates. That is, the first piezoelectric element 5 and the second piezoelectric element 6 operate in a mutually exclusive manner. According to the above embodiments of the present disclosure, the piezoelectric drive system 1000 has advantages of a simple structure, a precise drive stroke, a strong drive force and a high energy conversion efficiency.
In the piezoelectric drive device and the piezoelectric drive system according to the embodiments of the present disclosure, when the first or second piezoelectric element is powered on, the first or second piezoelectric element will expand in the direction perpendicular to the first or second side wall of the recess, so as to drive the first or second actuating part to move in the same direction, and thus the first or second actuating part can be fitted with the movable member to drive the movable member to move in a desired direction. Further, when the first or second piezoelectric element is powered off, the first or second piezoelectric element will shrink in the direction perpendicular to the first or second side wall of the recess, and hence the first or second actuating part will also restore to its initial position without influence on the movable member. As repeated in this manner, the movable member can move continuously in the desired direction.
Consequently, the piezoelectric drive device and the piezoelectric drive system according to the embodiments of the present disclosure have advantages of a simple structure, a convenient control, a precise drive stroke, a strong drive force and a high energy conversion efficiency.
In the descriptions of the present disclosure, it should be noted that unless specified or limited otherwise, the terms “installed”, “interconnected” and “connected” shall be broadly understood. For example, they may be fixed connections, or detachable connections or integrated connections; they may be mechanical connections or electric connections; they may also be direct connections or indirect connections through intermediate medium, and may also be inner communications of two elements. For those skilled in the art, the specific meaning of the above terms in the present disclosure may be understood according to specific circumstances.
Reference throughout this specification to terms “an embodiment,” “a specific embodiment,” “an example,” means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In this specification, exemplary descriptions of aforesaid terms are not necessarily referring to the same embodiment or example. Moreover, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
Although embodiments of the present disclosure have been illustrated and described above, it should be understood by those skilled in the art that changes, modifications, alternatives, and variations can be made in the embodiments without departing from principles and purposes of the present disclosure. The scope of the present disclosure is defined by the claims and their equivalents.
The present application is a US national phase application of International Application No. PCT/CN2021/122791, filed on Oct. 9, 2021, the entire content of which is incorporated by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2021/122791 | 10/9/2021 | WO |
