In-plane traveling wave micro ultrasonic motor

Abstract

The application discloses an in-plane traveling wave type micro ultrasonic motor, which comprises a ring-shaped driving stator, a ring-shaped rotor, a plurality of support beams, a plurality of driving units and a chip substrate. The ring-shaped driving stator and the ring-shaped rotor are connected through a harmonic gear driving principle. The driving stator drives the rotor through the meshing in and out of the tooth-shaped structure designed on the ring-shaped driving stator. The support beams are uniformly distributed on the periphery of the stator based on the in-plane standing wave mode to realize the connection of the stator and the substrate, the symmetric influence of the support beams on the stator, and the independent participation of each driving unit in the stator traveling wave operation. The in-plane traveling wave type micro ultrasonic motor has high load capacity, and the tooth driving mode brings high rotation precision.

Description

Technical Field

[0001] This invention belongs to the field of piezoelectric micromotor technology, and in particular, an in-plane traveling wave micro-ultrasonic motor. Background Technology

[0002] Unlike traditional motors, ultrasonic motors do not require electromagnetic forces to generate driving force. Utilizing the inverse piezoelectric effect of piezoelectric ceramics, a traveling wave ultrasonic motor generates two orthogonal standing waves on its stator, which superimpose to form a traveling wave. The rotor is driven by friction generated through the elliptical motion of the stator surface. Therefore, it has no magnetic poles or windings, and does not introduce additional electromagnetic interference to the overall system. Furthermore, due to its advantages such as high output density, high speed at low speeds, low operating voltage, simple and compact structure, low operating noise, and small size, it is widely used in small applications such as medical actuators, robots, and camera focusing. With the development of MEMS technology, the size of traveling wave ultrasonic motors has been further reduced to the millimeter level, thus possessing enormous application potential in various micro-application fields. Currently, commonly used piezoelectric micromotors mostly employ a disk structure, generating two orthogonal standing waves on the disk through the inverse piezoelectric effect. These standing waves are then superimposed on the disk surface to excite a continuously propagating traveling wave.

[0003] However, existing ultrasonic micro motors have the following two main drawbacks: First, the frictional effect between the stator and rotor of the thin-film disc ultrasonic micro motor during operation brings great complexity and nonlinearity, making the rotor rotation process uncontrollable. It requires a high-precision closed-loop control system to achieve high-precision control of the rotation state, which makes it difficult to control costs. Second, the friction drive principle will continuously cause the rotor friction layer to wear down, resulting in a short lifespan for the micro ultrasonic motor, and the rotor needs to be manufactured independently. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the prior art by providing an in-plane traveling wave micro-ultrasonic motor structure.

[0005] The technical solution to achieve the purpose of this invention is as follows: an in-plane traveling wave micro-ultrasonic motor. The motor structure includes an annular drive stator, an annular rotor, several U-shaped support beams, several drive units, and a chip substrate. The annular drive stator and the annular rotor rely on the harmonic gear drive principle. An in-plane traveling wave is formed on the annular drive stator, causing its tooth structure to exhibit an elliptical motion trajectory. Based on its motion trajectory, the tooth structure between the stator and rotor repeatedly engages and disengages to achieve rotor drive. The support beams are uniformly distributed around the stator based on the in-plane standing wave mode to connect the stator and the substrate. At the same time, the support beams have a symmetrical influence on the stator. The drive units attached to the support beams provide a certain displacement to the support beams to drive the stator to generate the standing wave. Finally, a high-quality traveling wave is successfully generated on the stator, and the tooth drive method brings high rotational accuracy.

[0006] Furthermore, the chip substrate is formed by stacking a top silicon layer, a buried oxide layer, and a bottom silicon layer from top to bottom, and the annular drive stator, the annular rotor, and several U-shaped support beams are all disposed on the top silicon layer.

[0007] Furthermore, the annular drive stator, annular rotor, several U-shaped support beams, and the top silicon layer of the chip substrate are all integrally photolithographically formed.

[0008] Furthermore, several of the U-shaped support beams serve as carriers of the inverse piezoelectric effect of the piezoelectric material. The U-shaped support beams symmetrical about the stator center exhibit the same deformation at the same time, and the deformation of adjacent U-shaped support beams is orthogonal.

[0009] Furthermore, a portion of the U-shaped support beam is covered with piezoelectric material and electrodes to enable radial movement of the end of the U-shaped support beam under the inverse piezoelectric effect.

[0010] Furthermore, the area where the U-shaped support beam covers the piezoelectric material consists of, from top to bottom, a top insulating layer, an upper power supply electrode layer, a piezoelectric thin film layer, a lower grounding electrode layer, and a top silicon layer.

[0011] Furthermore, where the U-shaped support beam covers the piezoelectric material, the upper power supply electrode layer is etched based on the driving principle, and reasonable driving signals are applied to different electrode zones.

[0012] Furthermore, after the motor structure is running stably, the annular rotor requires one traveling wave cycle to rotate one tooth, and the inner circle of the annular rotor can be connected to the shaft to achieve torque transmission.

[0013] Furthermore, the annular drive stator can rotate while the annular rotor is fixed, and its U-shaped support beam can also be extended from the inside and anchored to the current annular rotor, so that the current annular rotor generates traveling waves to drive the current annular drive stator to operate, thereby realizing the interchangeability of stator and rotor.

[0014] Compared with the prior art, the significant advantages of this invention are:

[0015] 1) The in-plane traveling wave micro ultrasonic motor structure of the present invention is based on the harmonic gear principle. Based on the traveling wave of the annular stator and its elliptical motion, after the motor is working stably, the tooth structure between the stator and the rotor continuously meshes, so that the rotor can rotate one tooth in one cycle. Therefore, the rotation accuracy is proportional to the number of teeth. High-precision angle control can be achieved in high-tooth-count structures. Its rotation law is simple and easy to implement.

[0016] 2) The structure is suspended by the external support soft beam, which reduces the energy loss caused by in-plane friction. The U-shaped design of the support beam reduces the damping effect on the stator, increases the in-plane standing wave displacement, and improves the contact force between the stator and rotor teeth. Based on the high torque characteristics of the gear, it ensures that the in-plane traveling wave micro ultrasonic motor has a high load-carrying capacity.

[0017] 3) The support beam is covered with piezoelectric material and electrodes. Through a certain electrode distribution and drive control, the end of the support beam moves radially, eliminating its Z-axis movement, so that the stator traveling wave can operate in the required planar mode according to the characteristic frequency, further reducing energy loss.

[0018] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the in-plane traveling wave micro-ultrasonic motor structure of the present invention.

[0020] Figure 2 This is a cross-sectional view of the in-plane traveling wave micro-ultrasonic motor structure of the present invention.

[0021] Figure 3 This is a schematic diagram of the standing wave operating mode of the in-plane traveling wave micro-ultrasonic motor structure of the present invention, wherein... Figure 3 (a) in the diagram represents an in-plane standing wave mode of the stator. Figure 3 (b) in the text is related to... Figure 3 Another in-plane standing wave mode that is orthogonal to the modes in (a) of the above.

[0022] Figure 4 This is a schematic diagram showing the piezoelectric material and electrode distribution on the support beam of the in-plane traveling wave micro-ultrasonic motor structure of the present invention.

[0023] Figure 5 This is a schematic diagram of the deformation of the drive stator of the in-plane traveling wave micro ultrasonic motor structure of the present invention. Figure 5 (a) in the diagram shows the deformation of the supporting beam. Figure 5 (b) Schematic diagram of the elliptical motion of particles on the surface of the annular driven stator.

[0024] Figure 6 This is a simulation diagram of the rotor rotation characteristics of the in-plane traveling wave micro-ultrasonic motor structure of the present invention.

[0025] The reference numerals in the figures are as follows: 1. Annular rotor; 2. Annular drive stator; 3. Support beam; 4. Drive unit; 5. Chip substrate; 6. Top silicon layer; 7. Buried oxide layer; 8. Bottom silicon layer; 9. Piezoelectric thin film layer; 10. Upper power supply electrode layer; 11. Lower ground electrode layer. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0027] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0028] This invention provides an in-plane traveling wave micro-ultrasonic motor structure, including an annular drive stator, an annular rotor, several support beams, several drive units, and a chip substrate. The annular drive stator and the annular rotor rely on the harmonic gear drive principle. An in-plane traveling wave is formed on the annular drive stator, causing its toothed structure to exhibit an elliptical motion trajectory. Based on this motion trajectory, the toothed structure between the stator and rotor repeatedly engages and disengages, thereby achieving rotor drive. The support beams are uniformly distributed around the stator based on the in-plane standing wave mode, connecting the stator and the substrate. This achieves a symmetrical influence of the support beams on the stator. The drive units attached to the support beams provide a certain displacement to the support beams, thereby driving the stator to generate standing waves. Finally, a high-quality traveling wave is successfully generated on the stator.

[0029] The in-plane traveling wave micro-ultrasonic motor structure of the present invention achieves a suspended connection of the structure through an external support soft beam, reducing energy loss caused by in-plane friction. The U-shaped design of the support beam reduces the damping effect on the stator, increases the in-plane standing wave displacement, and improves the contact force between the stator and rotor teeth, ensuring that the in-plane traveling wave micro-ultrasonic motor has a high load-carrying capacity, and the tooth drive method brings high rotational accuracy.

[0030] In one embodiment, such as Figure 1 , 2As shown, the entire motor structure includes an annular rotor 1, an annular drive stator 2, eight U-shaped support beams 3, eight drive units 4 covering the support beams, and a chip substrate 5 for motor fixation. The annular rotor 1, the annular drive stator 2, and the support beams 3 not covering the drive units 4 are all composed of a top silicon layer 6, which can be integrally formed by photolithography. The number of teeth on the annular drive stator 2 is more than the number of teeth on the annular rotor 1. In this embodiment, the difference in the number of teeth is 2. The support beam 3, which is covered by the drive unit 4 at the U-shaped loop, is composed of an upper power supply electrode layer 10, a piezoelectric thin film layer 9 and a lower ground electrode layer 11 stacked from top to bottom. The upper power supply electrode layer 10 is further partitioned by etching. By further driving and controlling the different partitions, the end of the support beam 3 moves radially based on the inverse piezoelectric effect. The top insulating layer is deposited on the upper power supply electrode layer 10 after etching. The upper power supply electrode layer 10 is opened by etching the top insulating layer to facilitate the introduction of power supply signal lines into each partition to achieve potential introduction. The chip substrate 5 is composed of a top silicon layer 6, a buried oxide layer 7 and a bottom silicon layer 8 stacked from top to bottom. The top silicon layer is photolithographically formed at the same time as the above-mentioned annular rotor 1 and other units, and the bottom silicon layer 8 is released from the stagnation of the stator and rotor structure based on the deep silicon etching process.

[0031] After simplifying the toothed structure, this invention performs finite element characteristic frequency simulation to obtain the two in-plane standing wave modes of the annular drive stator 2, as follows: Figure 3 As shown. By Figure 3 As can be seen (the grayscale values ​​in the figure excluding the chip substrate represent the magnitude of displacement), the symmetrical anchoring of the support beam 3 ensures that its influence on the two generated standing wave modes is identical. Therefore, the natural frequencies of the two standing wave modes are 22.20 kHz and 22.21 kHz, respectively, indicating a very high degree of frequency matching. These two standing waves maintain the same frequency and have a one-quarter wavelength difference in phase, demonstrating that the ultrasonic micromotor drive stator of this invention can easily generate high-quality standard traveling waves.

[0032] Regarding the distribution of each drive unit 4 of the above-mentioned standing wave mode and in-plane traveling wave micro ultrasonic motor, as follows: Figure 4 As shown, each of the eight electrode zones on the U-shaped loop is configured as a drive unit 4 to control the movement of the support beam in which it is located, and in Figure 4 The image shows four types of support beam drive groups, where the deformation states of the support beams controlled by every two drive units 4 from top to bottom are 90 degrees out of phase in time. Figure 4 The supporting beam 3 where the upper and lower adjacent drive units 4 are located is Figure 1 The stator 2 of the intermediate ring drive is circumferentially adjacent; where A is numbered and the input amplitude is A. n The AC driving voltage is sin(2πf), where f is the average of the natural frequencies of the two standing wave modes obtained above, and B is the input amplitude of A. nThe AC drive voltage is sin(2πf+π / 2), and C is the input amplitude of A. n The AC drive voltage is sin(2πf+π); D is numbered as the input amplitude is A. n The AC driving voltage is sin(2πf+3π / 2), so that the phase difference between each pair of the four driving signals A, B, C, and D is 90 degrees. Through the application of these positive and negative potentials, the longitudinal displacements generated by the inverse piezoelectric effect of the piezoelectric film on the U-shaped loop of the supporting beam cancel each other out, while the lateral displacements are superimposed, ultimately forming a shape like... Figure 5 The deformation of the support beam shown in (a) generates a driving force through the radial displacement at the end of the support beam 3, causing the annular drive stator 2 to generate the aforementioned two-phase standing wave mode, thereby generating a traveling wave and based on... Figure 5 (b) shows the elliptical motion that drives the annular rotor 1 to rotate.

[0033] Figure 6 The diagram shows the rotor rotation angle versus time obtained through transient simulation of the in-plane traveling wave micro-ultrasonic motor under a simplified model. It also shows the motion trajectory of the particles on the rotor tooth surface during the start-up and uniform rotation processes. It can be seen that the rotor rotates one tooth after one stator traveling wave cycle when running stably, indicating that the stator traveling wave can drive the rotor to rotate according to the harmonic gear drive principle. This fully verifies that the in-plane traveling wave micro-ultrasonic motor of the present invention can operate effectively, achieve high torque output, and ensure a certain degree of angular accuracy.

[0034] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit and essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0035] Finally, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An in-plane traveling wave type micro ultrasonic motor, characterized in that, The motor structure includes an annular drive stator, an annular rotor, several U-shaped support beams, several drive units, and a chip substrate. The annular drive stator and the annular rotor rely on the harmonic gear drive principle. An in-plane traveling wave is formed on the annular drive stator, causing its tooth structure to exhibit an elliptical motion trajectory. Based on this motion trajectory, the tooth structure between the stator and rotor repeatedly engages and disengages, realizing rotor drive. The U-shaped support beams are uniformly distributed around the annular drive stator based on the in-plane standing wave mode, realizing the connection between the annular drive stator and the chip substrate. At the same time, the U-shaped support beams have a symmetrical influence on the annular drive stator. The drive units attached to the U-shaped support beams provide a certain displacement to the U-shaped support beams, thereby driving the stator to generate standing waves, ultimately producing traveling waves on the annular drive stator.

2. The in-plane traveling wave micro-ultrasonic motor according to claim 1, characterized in that, The chip substrate is formed by stacking a top silicon layer, a buried oxide layer, and a bottom silicon layer from top to bottom. The annular drive stator, the annular rotor, and several U-shaped support beams are all located in the top silicon layer.

3. The in-plane traveling wave micro-ultrasonic motor according to claim 2, characterized in that, The annular drive stator, annular rotor, several U-shaped support beams, and the top silicon layer of the chip substrate are all integrally photolithographically formed.

4. The in-plane traveling wave micro-ultrasonic motor according to claim 2, characterized in that, Several of the U-shaped support beams serve as carriers of the inverse piezoelectric effect of the piezoelectric material. The U-shaped support beams symmetrical about the stator center exhibit the same deformation at the same time, and the deformation of adjacent U-shaped support beams is orthogonal.

5. The in-plane traveling wave micro-ultrasonic motor according to claim 4, characterized in that, The U-shaped support beam is partially covered with piezoelectric material and electrodes to enable the end of the U-shaped support beam to move radially under the action of the inverse piezoelectric effect.

6. The in-plane traveling wave micro-ultrasonic motor according to claim 5, characterized in that, The area where the U-shaped support beam covers the piezoelectric material consists of, from top to bottom, a top insulating layer, an upper power supply electrode layer, a piezoelectric thin film layer, a lower grounding electrode layer, and a top silicon layer.

7. The in-plane traveling wave micro-ultrasonic motor according to claim 6, characterized in that, The upper power supply electrode layer is etched based on the driving principle at the location where the U-shaped support beam covers the piezoelectric material, and driving signals are applied to different electrode zones.

8. The in-plane traveling wave micro-ultrasonic motor according to claim 1, characterized in that, After the motor structure is running stably, it takes one traveling wave cycle for the annular rotor to rotate one tooth. The inner circle of the annular rotor can be connected to the shaft to realize torque transmission.

9. The in-plane traveling wave micro-ultrasonic motor according to claim 1, characterized in that, The annular drive stator can rotate when the annular rotor is fixed, and its U-shaped support beam can also be led out from the inside and anchored to the current annular rotor, so that the current annular rotor generates a traveling wave to drive the current annular drive stator to operate, thereby realizing the interchangeability of stator and rotor.

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