Constant-pre-pressure traveling wave rotary open type large-caliber ultrasonic motor and implementation method thereof

Abstract

The invention relates to the technical field of ultrasonic motors, and discloses a constant-pre-pressure traveling wave rotary open large-caliber ultrasonic motor and an implementation method thereof.The ultrasonic motor comprises a stator base assembly, an output shaft and a flexible rotor assembly, and the flexible rotor assembly further comprises damping rubber, a flexible rotor and a friction material which are sequentially connected from top to bottom; the ultrasonic motor further comprises a pre-pressing shaft and at least two elastic parts, the pre-pressing shaft, the output shaft, the stator elastic assembly and the flexible rotor assembly are coaxially arranged, and the pre-pressing shaft is provided with a flange plate arranged at one end. The elastic parts are arranged in positioning holes in the top of the flexible rotor assembly, and the elastic parts are arranged at intervals along the circumferential position between the flange plate of the pre-pressing shaft and the flexible rotor assembly. According to the ultrasonic motor, the stability of the mechanical output characteristic in the whole life cycle is improved; the axial space in the motor is reasonably utilized by the pre-pressure applying mode, and the assembling and debugging process is simplified while the size of the existing compact axial structure is ensured.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic motor technology, and in particular to a constant preload traveling wave rotary open-type large-diameter ultrasonic motor and its implementation method. Background Technology

[0002] The statements in this section are merely to provide background information related to the disclosure of this invention and do not necessarily constitute prior art.

[0003] In existing technologies, large-diameter traveling-wave rotary ultrasonic motors have high preload between the stator and rotor, primarily provided by the deformation of the rotor's flexible web, such as the open-type large-diameter hollow rotary ultrasonic motor proposed in our company's patent CN216162637U; especially ultrasonic motors with a larger hollow diameter ratio (usually referring to the ratio of the motor's effective hollow diameter to the stator's outer diameter or the motor's outer envelope diameter), such as the hollow rotary ultrasonic motor with a large hollow diameter ratio proposed in our company's patent CN118017870A and the open-type large hollow diameter ratio rotary traveling-wave ultrasonic motor and pressure application method disclosed in patent CN11824967A. These solutions generally feature relatively short flexible webs on the rotor, resulting in very small deformation displacement of the stator and rotor under working preload. When friction materials wear, the preload between the stator and rotor drops rapidly, leading to a sharp decline in mechanical output characteristics and a short lifespan, making them unsuitable for applications requiring longer lifespans.

[0004] To address the technical problem of short rotor webs in ultrasonic motors failing to provide large deformation displacements, existing technologies include pre-pressure application via springs acting on a floating stator assembly. For example, the annular ultrasonic motor mentioned in US Patent US2017015531A1 uses a stator without a web structure, applying pre-pressure by having wave springs and felt rings directly acting on the vibrating substrate, axially compressing the stator assembly onto the rotor. Chinese Patent CN108880322B presents a rotating traveling wave ultrasonic motor employing a novel pre-pressure application method. In this method, the stator retains a web, and the wave springs indirectly apply pre-pressure by acting on a stator support frame fixed to the stator, axially compressing the floating stator assembly onto the rotor assembly. Both of these pre-pressure application methods require high stability from the wave springs during motor operation, necessitating that all support points of the wave springs lie on a single plane to ensure parallelism between the stator tooth surface and the rotor friction material surface, guaranteeing good contact. The former is suitable for applications with low preload and low output torque, such as lens focusing; the latter is suitable for applications with higher preload and output torque, but it also sacrifices a lot of axial space, resulting in a less compact axial structure and making it unsuitable for some applications with small axial space.

[0005] In the prior art, a method of applying pre-pressure to the upper surface of the rotor by means of locking screws and springs is proposed, such as the hollow ultrasonic motor with adjustable pre-pressure proposed in published patent CN108667343 A. First, this solution requires a relatively large axial space. Second, with the further increase in the diameter of the stator and rotor and the hollow cavity diameter, for example, if the rotor diameter exceeds 30mm, it is impossible to select a spring with a small wire diameter, short length, and suitable elastic force in the existing spring standards. Third, as can be seen from the structural diagram and specific implementation method provided by the patent, in this solution, the locking nut is connected to the upper cover by threads, the locking nut axially compresses the spring, the spring presses on the hollow shaft connected to the rotor, and the rotor finally presses on the stator, thereby achieving the application of preload. The bearing supporting the hollow shaft is arranged on the base. Obviously, this solution has structural problems. One end of the spring acts on the end face of the locking nut fixedly connected to the upper cover, and the other end acts on the hollow shaft, causing the rotating shaft system to be connected to the upper cover. The hollow shaft and the rotor can only rotate after overcoming the frictional torque of the spring end face.

[0006] Therefore, it is particularly necessary to address the technical problem of the rapid decrease in preload of existing large-diameter hollow ultrasonic motors due to the wear of friction materials, and the inability to select springs with suitable stiffness, working height, and working pressure, in order to improve the service life of ultrasonic motors. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, this invention provides a large-diameter hollow ultrasonic motor product that can maintain stable preload, has a compact axial structure, makes reasonable use of the internal axial space of the motor, does not require additional axial space, improves the stability of the mechanical output characteristics of the ultrasonic motor throughout its entire life cycle, and significantly increases the service life of the ultrasonic motor. While ensuring the existing compact axial structure dimensions, it simplifies the assembly and debugging process to meet the needs of practical engineering applications.

[0008] The technical solution adopted in this invention is: a constant preload traveling wave rotary open-type large-diameter ultrasonic motor, including a stator assembly, an output shaft, and a flexible rotor assembly. The flexible rotor assembly further includes vibration-damping rubber, a flexible rotor, and friction material connected sequentially from top to bottom. The ultrasonic motor also includes: A preload shaft, coaxially arranged with the output shaft, stator elastic assembly, and flexible rotor assembly, and having a flange at one end; and At least two elastic members are placed in positioning holes at the top of the flexible rotor assembly, and the elastic members are arranged at intervals along the circumferential position between the flange of the preload shaft and the flexible rotor assembly.

[0009] In this technical solution, the elastic component is a spring, and the number n is greater than or equal to 3.

[0010] In this technical solution, the flexible rotor assembly includes a guide ring disposed below the inner web of the flexible rotor. The guide ring is coaxially disposed with the preload shaft, wherein: the guide ring is provided with a countersunk hole corresponding to the elastic component in the circumferential direction, and the countersunk hole is a positioning hole. Furthermore, the preload shaft also includes a stop-fit ​​end face located at the other end, and the stop-fit ​​end face connects the output shaft and the preload shaft through a bearing baffle.

[0011] In this technical solution, the outer cylindrical surface of the preload shaft is fitted with the inner hole of the flexible rotor and the inner hole of the guide ring. At least one pair of guide grooves / guide bosses and guide bosses / guide grooves are respectively provided in the circumferential direction of the outer cylindrical surface and the circumferential direction of the guide ring. Meanwhile, the guide ring can slide freely along the axial direction on the outer cylindrical surface of the preload shaft.

[0012] In this technical solution, at least two cylindrical countersunk holes are provided on the circumferential direction of the guide ring, and threaded holes corresponding to the cylindrical countersunk holes are opened on the inner web of the flexible rotor to allow corresponding screws to pass through the flexible rotor and the guide ring for fixed connection. Cylindrical holes corresponding to the countersunk holes are provided on the circumferential direction of the inner web of the flexible rotor; and the number of cylindrical holes and countersunk holes is greater than or equal to 3 and they are evenly distributed in the circumferential position.

[0013] In this technical solution, the preload shaft has a flange extending outward in a circumferential direction, and an encoder disk is connected to the top of the flange. The housing is coaxially and fixedly connected to the stator base, and the housing is sequentially and fixedly connected to the encoder read head assembly and the encoder cover; Meanwhile, bearing one, bearing two, and stator elastomer assembly are coaxially arranged on the inner side of the stator base. The output shaft passes through bearing one and bearing two and is fixedly connected to the preload shaft. Furthermore, a bearing end cap is arranged between the output shaft and the preload shaft.

[0014] In this technical solution, the inner web of the flexible rotor is provided with guide holes corresponding to the pin holes in the circumferential direction, and at the same time, countersunk holes corresponding to the second countersunk hole are opened on the inner web of the flexible rotor; the number of the second and third countersunk holes is greater than or equal to 3, and they are evenly distributed in the circumferential position.

[0015] The implementation method of a constant preload traveling wave rotary open large-diameter ultrasonic motor, wherein the resultant force F exerted by all elastic components on the flexible rotor of the aforementioned constant preload traveling wave rotary open large-diameter ultrasonic motor is... 弹 The optimal preload F between the stator and the flexible rotor is designed. 设 ,make sure: F弹 ≤F 设 (1).

[0016] In this technical solution, the stiffness of the elastic component is respectively , , ... The total stiffness of the elastic components that are preloaded in parallel is The following requirements must be met: (2); (3); in: To ensure the stiffness of the flexible rotor, the elastic components are uniformly distributed circumferentially, and the compression of the elastic components during operation is 10 times or more the thickness of the friction material.

[0017] In this technical solution, when the friction material is worn thin, the elastic component squeezes the flexible rotor assembly to move it along the axial direction, in order to maintain the pre-pressure between the stator and the flexible rotor within the predetermined working pre-pressure range.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. Without increasing the axial dimensions of existing large-diameter hollow ultrasonic motors, by circumferentially arranging springs between the flexible rotor assembly and the preloaded shaft flange, the problem of not being able to select springs with suitable stiffness, working height, and working pressure in practical engineering applications of existing large-diameter hollow ultrasonic motors is solved. This achieves compensation for large displacement of the flexible rotor in the axial direction, resulting in a significant improvement in the utilization rate of friction material thickness.

[0019] 2. Under the same operating environment and conditions, the preload of the ultrasonic motor can be maintained within the optimal design preload range throughout its entire life cycle, the resonant frequency drift range is reduced, the mechanical output characteristics are more stable, and the service life is significantly improved. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the present invention; Figure 2 for Figure 1 A partial cross-sectional structural schematic diagram of an embodiment; Figure 3 for Figure 1 Exploded view of the entire machine in an embodiment; Figure 4 for Figure 1 A schematic diagram of the structure of one embodiment of the flexible rotor 402; Figure 5 for Figure 1A schematic diagram of the structure of one embodiment of the guide ring 404; Figure 6 for Figure 1 A schematic diagram of the structure of one embodiment of the preload shaft 6; Figure 7 This is a partial cross-sectional view of another embodiment; Figure 8 for Figure 7 Exploded view of the entire machine in an embodiment; Figure 9 for Figure 7 A schematic diagram of the flexible rotor 402 structure in an embodiment; Figure 10 for Figure 7 A schematic diagram of the structure of one embodiment of the preload shaft 6; Figure 11 for Figure 7 A schematic diagram of the structure of one embodiment of the stator base 101; Among them: 1-stator base assembly, 101-stator base, 102-bearing, 103-wire clamping plate, 104-stator elastic assembly, 1041-stator, 1042-piezoelectric ceramic sheet, 1043-flexible printed circuit board, 1044-thermometer, 105-bearing one, 106-bearing two, 107-bearing end cover, 108-copper nose wire clamping clip; 2-Output shaft; 3-Bearing baffle; 4-Flexible rotor assembly; 401-Vibration damping rubber; 402-Flexible rotor; 402a-Cylindrical hole; 402b-Threaded hole; 402c-Flexible rotor inner hole; 402d-Rotor countersunk hole; 403-Friction material; 404-Guide ring; 404a-Guide ring inner hole; 404b-Countersunk hole; 404c-Guide boss / Guide groove; 404d-Cylindrical countersunk hole; 405-Positioning hole; 5-Elastic component; 6-Preload shaft; 6a-Outer cylindrical surface; 6b-Guide groove / Guide boss; 6c-Flange; 6d-Stove mating end face; 6e-Flange one; 6f-Pin hole; 6h-Countersunk hole two; 10-Pin shaft; 12-Housing; 14-Encoder code disk; 15-Encoder read head assembly; 16-Encoder cover. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0022] In the description of this invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," and "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the combination or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, in the description of the embodiments of this invention, the positional relationships of devices such as "upper," "lower," "front," "rear," "left," and "right" in all figures are based on… Figure 1 As the standard.

[0023] like Figure 1 As shown, a constant preload traveling wave rotary open-type large-diameter ultrasonic motor includes a stator assembly 1, an output shaft 2, and a flexible rotor assembly 4. The flexible rotor assembly 4 further includes a damping rubber 401, a flexible rotor 402, and a friction material 403 connected sequentially from top to bottom. The ultrasonic motor also includes a preload shaft 6 and at least two elastic components 5, wherein: The preload shaft 6 is coaxially arranged with the output shaft 2, the stator elastic component 10, and the flexible rotor component 4, and the preload shaft 6 has a flange 6c at one end; the elastic component 5 is placed in the positioning hole 405 at the top of the flexible rotor component 4, and the elastic component 5 is arranged at intervals along the circumferential position between the flange 6c of the preload shaft 6 and the flexible rotor component 4.

[0024] In the specific implementation process, from Figure 2 and Figure 7 As can be seen from the above, the stator base assembly 1 includes: stator base 101, bearing 102 and stator elastomer assembly 104. The stator elastomer assembly 104 includes: stator 1041, piezoelectric ceramic sheet 1042, flexible printed circuit board 1043 and thermistor 1044 connected sequentially from top to bottom. The flexible printed circuit board 1043 is bonded to the piezoelectric ceramic sheet with epoxy resin, and the grounding terminal on the inner side of the flexible printed circuit board 1043 is also fixedly connected to the stator 1041 with screws.

[0025] In at least some embodiments, the elastic component 5 is a spring, and the number n is greater than or equal to 3.

[0026] In at least some embodiments, the flexible rotor assembly 4 includes a guide ring 404 disposed below the inner web of the flexible rotor 402. The guide ring 404 is coaxially disposed with the preload shaft 6. The guide ring 404 is provided with at least two countersunk holes 404b in the circumferential direction. In this embodiment, the positioning hole 405 is the countersunk hole 404b. Furthermore, the preload shaft 6 also includes a stop-fit ​​end face 6d located at the other end, and the stop-fit ​​end face 6d connects the output shaft 2 to the preload shaft 6 through the bearing baffle 3.

[0027] In at least some embodiments, combined Figure 2 , Figure 4 and Figure 6 As shown, the outer cylindrical surface 6a of the preload shaft 6 mates with the inner hole 402c of the flexible rotor and the inner hole 404a of the guide ring. At least one pair of guide grooves / guide bosses 6b and guide bosses / guide grooves 404c are respectively provided in the circumferential directions of the outer cylindrical surface 6a and the guide ring 404. Simultaneously, the guide ring 404 can slide freely along the axial direction on the outer cylindrical surface 6a of the preload shaft 6, thereby achieving a double-fitting and pressing of the preload shaft 6 and the flexible rotor assembly 4. Firstly, the outer cylindrical surface 6a is respectively fitted with the flexible rotor assembly 4. Both the rotor inner hole 402c and the guide ring inner hole 404a are fitted together. Secondly, at least one pair of guide grooves / guide bosses 6b and guide bosses / guide grooves 404c are respectively provided on the outer cylindrical surface 6a and the guide ring 404 in the circumferential direction, which are fitted from multiple positions to further ensure that the preload shaft 6 can be pressed tightly against the flexible rotor assembly 4 in the circumferential direction to maintain the stability of the preload transmission during operation. At the same time, the guide ring 404 can slide freely along the axial direction on the outer cylindrical surface 6a of the preload shaft 6.

[0028] It should be noted that, in the specific implementation process, when the guide groove / guide boss 6b of the outer cylindrical surface 6a is a guide groove, the guide boss / guide groove 404c of the guide ring 404 is a guide boss; when the guide groove / guide boss 6b of the outer cylindrical surface 6a is a guide boss, the guide boss / guide groove 404c of the guide ring 404 is a guide groove, as long as sliding can be achieved.

[0029] In at least some embodiments, such as Figure 4 As shown, the guide ring 404 is provided with at least two cylindrical countersunk holes 404d in the circumferential direction, and the inner web of the flexible rotor 402 is provided with threaded holes 402d corresponding to the cylindrical countersunk holes 404d, so that corresponding screws can pass through the flexible rotor 402 and the guide ring 404 for fixed connection. The inner web of the flexible rotor 402 is provided with cylindrical holes 402a corresponding to the countersunk holes 404b in the circumferential direction; and the number of cylindrical holes 402a and countersunk holes 404b is greater than or equal to 3, and they are evenly distributed in the circumferential position.

[0030] In at least some embodiments, such as Figure 7 and Figure 8 , Figure 10As shown, the preload shaft 6 has a flange 6e extending outward in a circumferential direction, and the top of the flange 6e is connected to the encoder disk 14; this embodiment does not have a position sensor (i.e., encoder), and in use, it needs to be combined with an external sensing device of the coaxial system for closed-loop control.

[0031] Figure 7 In the embodiment shown, the ultrasonic motor has a built-in position sensor, which can be used for closed-loop position control.

[0032] The outer casing 12 is coaxially and fixedly connected to the stator base 101, and the outer casing 12 is sequentially and fixedly connected to the encoder read head assembly 15 and the encoder cover 16; simultaneously, bearing one 105, bearing two 106, and stator elastomer assembly 104 are coaxially arranged on the inner side of the stator base 101, and the output shaft 2 is fixedly connected to the preload shaft 6 through bearing one 105 and bearing two 106, and a bearing end cover 107 is also arranged between the output shaft 2 and the preload shaft 6. In the specific implementation process, such as Figure 10 As shown, a pin hole 6f for co-positioning with the pin shaft 10 and a countersunk hole 6h can also be provided on the preload shaft 6. The countersunk hole 6h is used to position the elastic component 5 on the other side. Using double bearings (or double row bearings) to support the output shaft 2 can improve the stability of the output shaft 2 during rotation. For example, the runout of the output shaft 2 will be smaller, and the control accuracy will also be improved.

[0033] In addition, Figure 7 It can also be seen that, in order to facilitate the fixing of the cable and prevent the solder joint from being directly stressed when the cable is pulled by external force, the stator base assembly 1 also includes a copper nose wire clamp 108, which is connected to the stator base 101.

[0034] In at least some embodiments, the flexible rotor 402 has a guide hole 402d corresponding to the pin hole 6f in the circumferential direction of the inner web plate, and a countersunk hole 402e corresponding to the countersunk hole 6h is opened on the inner web plate of the flexible rotor 402; the number of the countersunk holes 6h and the countersunk holes 402e is greater than or equal to 3, and they are evenly distributed in the circumferential position.

[0035] In addition, such as Figure 11 The figure shown is a three-dimensional structural diagram of an embodiment of the stator base 101 in this example. It can be seen that the structure is adapted to the structure of this embodiment. The specific structural design includes the connection between the outermost layer and the outer shell 12, and the inner hollow interlayer for supporting the flexible rotor 402.

[0036] The method for implementing a constant preload traveling wave rotary open-type large-diameter ultrasonic motor involves applying the resultant force F of all elastic components 5 to the flexible rotor 402 in the aforementioned constant preload traveling wave rotary open-type large-diameter ultrasonic motor. 弹The optimal preload F designed between the stator 1041 and the flexible rotor 402 设 It satisfies the following relationship: F 弹 ≤F 设 (1).

[0037] In at least some embodiments, the stiffness of the elastic member 5 is respectively , , ... The total stiffness of the elastic member 5, which is subjected to preload in parallel, is... The following requirements must be met: (2); (3); in: To ensure the stiffness of the flexible rotor 402, the elastic component 5 is uniformly distributed circumferentially. The compression of the elastic component 5 during operation is 10 times or more the thickness of the friction material 403. This combination of the two characteristics is crucial to ensuring that the preload between the stator 1041 and the flexible rotor 402 remains within the designed optimal working preload range throughout the entire lifespan of the ultrasonic motor. When the friction material 403 wears, the elastic component 5 elongates, and the elongation of the elastic component 5 is approximately equal to the wear amount of the friction material 403. Since the stiffness of the elastic component 5 is much smaller than that of the flexible rotor 402, the change in elastic force when the elastic component 5 elongates to compensate for axial displacement is very small. This ensures that the preload between the stator 1041 and the flexible rotor 402 remains within the optimal designed working preload range, thereby maintaining the stability of the preload.

[0038] In at least some embodiments, when the friction material 403 wears and thins, the elastic member 5 compresses the flexible rotor assembly 4, causing it to move along the axial direction, to maintain the pre-pressure between the stator 1041 and the flexible rotor 402 within a predetermined working pre-pressure range. Figure 1Taking the illustrated embodiment as an example, the application path of the ultrasonic motor preload is as follows: the preload shaft axially squeezes the elastic component 5, the elastic component 5 axially squeezes the flexible rotor assembly 4, and the flexible rotor assembly 4 finally squeezes the stator elastic body assembly 104, thereby achieving the application of preload between the ultrasonic motor stator 1041 and the flexible rotor 402. When the friction material 403 wears, the elastic component 5 elongates, and the elongation of the elastic component 5 is approximately equal to the wear of the friction material 403. Since the stiffness of the elastic component 5 is much smaller than that of the flexible rotor 402, the change in elastic force of the elastic component 5 when elongating to compensate for axial displacement is very small, so that the preload between the stator 1041 and the flexible rotor 402 remains within the optimal design working preload range, thereby achieving significant compensation for axial displacement and maintaining the stability of the preload.

[0039] The embodiments disclosed herein are preferred embodiments, but are not limited thereto. Those skilled in the art can readily grasp the spirit of the present invention based on the above embodiments and make different extensions and variations, but as long as they do not depart from the spirit of the present invention, they are all within the protection scope of the present invention.

Claims

1. A constant preload traveling wave rotary open-type large-diameter ultrasonic motor, comprising a stator assembly (1), an output shaft (2), and a flexible rotor assembly (4), wherein the flexible rotor assembly (4) further comprises a damping rubber (401), a flexible rotor (402), and a friction material (403) connected sequentially from top to bottom, characterized in that, The ultrasonic motor also includes: A preload shaft (6) is coaxially arranged with the output shaft (2), the stator elastic assembly (104), and the flexible rotor assembly (4), and the preload shaft (6) has a flange (6c) at one end; and At least two elastic members (5) are placed in a positioning hole (405) on the top of the flexible rotor assembly (4), and the elastic members (5) are arranged at intervals along the circumferential position between the flange (6c) of the preload shaft (6) and the flexible rotor assembly (4).

2. The constant preload traveling wave rotary open-type large-diameter ultrasonic motor according to claim 1, characterized in that: The elastic component (5) is a spring, and the number n is greater than or equal to 3.

3. A constant preload traveling wave rotary open-type large-diameter ultrasonic motor according to claim 1 or 2, characterized in that: The flexible rotor assembly (4) includes a guide ring (404) disposed below the inner web of the flexible rotor (402). The guide ring (404) is coaxially disposed with the preload shaft (6). The guide ring (404) is provided with a countersunk hole (404b) corresponding to the elastic component (5) in the circumferential direction. At this time, the countersunk hole (404b) is the positioning hole (405). Furthermore, the preload shaft (6) also includes a stop fitting end face (6d) located at the other end, and the stop fitting end face (6d) connects the output shaft (2) to the preload shaft (6) through the bearing baffle (3).

4. The constant preload traveling wave rotary open-type large-diameter ultrasonic motor according to claim 3, characterized in that: The outer cylindrical surface (6a) of the preload shaft (6) is fitted with the inner hole (402c) of the flexible rotor and the inner hole (404a) of the guide ring. At least one pair of guide grooves / guide bosses (6b) and guide bosses / guide grooves (404c) are respectively provided on the outer cylindrical surface (6a) and the guide ring (404) in the circumferential direction. Meanwhile, the guide ring (404) can slide freely along the axial direction on the outer cylindrical surface (6a) of the preload shaft (6).

5. The constant preload traveling wave rotary open-type large-diameter ultrasonic motor according to claim 4, characterized in that: The guide ring (404) is provided with at least two cylindrical countersunk holes (404d) in the circumferential direction. At the same time, the inner web of the flexible rotor (402) is provided with threaded holes (402d) corresponding to the cylindrical countersunk holes (404d) for the corresponding screws to pass through the flexible rotor (402) and the guide ring (404) for fixed connection. The inner web of the flexible rotor (402) is provided with cylindrical holes (402a) corresponding to the countersunk holes (404b) in the circumferential direction. Moreover, the number of cylindrical holes (402a) and countersunk holes (404b) is greater than or equal to 3 and they are evenly distributed in the circumferential position.

6. A constant preload traveling wave rotary open-type large-diameter ultrasonic motor according to claim 1 or 2, characterized in that: The preload shaft (6) has a flange (6e) extending outward in a circumferential direction, and the top of the flange (6e) is connected to an encoder disk (14). The outer casing (12) is coaxially and fixedly connected to the stator base (101), and the outer casing (12) is sequentially and fixedly connected to the encoder read head assembly (15) and the encoder cover (16); Meanwhile, bearing one (105), bearing two (106) and stator elastomer assembly (104) are coaxially arranged on the inner side of the stator base (101). The output shaft (2) passes through bearing one (105) and bearing two (106) and is fixedly connected to the preload shaft (6). A bearing end cap (107) is also arranged between the output shaft (2) and the preload shaft (6).

7. A constant preload traveling wave rotary open-type large-diameter ultrasonic motor according to claim 6, characterized in that: The flexible rotor (402) has a guide hole (402d) corresponding to the pin hole (6f) in the circumferential direction on the inner web plate. At the same time, a countersunk hole (402e) corresponding to the second countersunk hole (6h) is opened on the inner web plate of the flexible rotor (402). The number of the second countersunk hole (6h) and the third countersunk hole (402e) is greater than or equal to 3, and they are evenly distributed in the circumferential position.

8. A method for implementing a constant preload traveling wave rotary open-type large-diameter ultrasonic motor, characterized in that: For any one of claims 1-7, the constant preload traveling wave rotary open large-diameter ultrasonic motor, the resultant force F exerted by all elastic components (5) on the flexible rotor (402) is... 弹 The optimal preload F is designed between the stator (1041) and the flexible rotor (402). 设 It satisfies the following relationship: F 弹 ≤F 设 (1)。 9. The ultrasonic motor implementation method according to claim 8, characterized in that: The stiffness of the elastic component (5) are respectively , , ... The total stiffness of the elastic member (5) subjected to preload in parallel is... The following requirements must be met: （2）； （3）； in: To ensure the stiffness of the flexible rotor (402), the elastic component (5) is uniformly distributed circumferentially, and the compression of the elastic component (5) during operation is 10 times or more the thickness of the friction material (403).

10. The ultrasonic motor implementation method according to claim 9, characterized in that: When the friction material (403) is worn thin, the elastic component (5) squeezes the flexible rotor assembly (4) to move it along the axial direction, in order to maintain the pre-pressure between the stator (1041) and the flexible rotor (402) within the predetermined working pre-pressure range.

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