Longitudinal torsion type coaxial bidirectional rotation type ultrasonic motor and operation method

Abstract

The invention relates to a longitudinal torsion type coaxial bidirectional rotation type ultrasonic motor and an operation method, a stator assembly comprises a first stator, a second stator, a flange plate and 4n piezoelectric ceramic pieces, and a rotor assembly comprises a first rotor, a second rotor and an output shaft; the output shaft penetrates through the center of the flange plate and uniformly divides the piezoelectric ceramic pieces into two groups which are coaxially adhered to the two sides of the flange plate respectively; a first stator and a second stator are respectively adhered to one side, opposite to the head and the bottom of the output shaft, of each group of piezoelectric ceramic pieces; the head of the output shaft is inserted into the first rotor; the first rotor is tightly connected with the head of the output shaft; a bearing is installed between the interior of the second rotor and the output shaft, when the stator assembly generates vibration under sinusoidal voltage input, the first rotor rotates clockwise and transmits the rotation to the output shaft, the second rotor rotates anticlockwise under the support of the bearing, and the first rotor and the second rotor can rotate in different directions respectively. The two-way motion output device is simple in structure, high in driving speed, excellent in output performance, capable of outputting two-way motion at the same time, adjustable in pre-pressure and low in cost.

Description

Technical Field

[0001] The present invention relates to a longitudinal-torsional coaxial bidirectional rotary ultrasonic motor and an operation method thereof, belonging to the field of ultrasonic motors. Background Art

[0002] In recent years, the miniaturization of drive sources has become a mainstream trend in scientific research. As the most common drive device at present, DC motors have matured. However, with the miniaturization of motors, some inevitable problems have emerged in DC motors. The reduction in efficiency caused by extremely high Joule heat makes it impossible to be the first choice for micro-miniature motors. An ultrasonic motor (also known as an "ultrasonic wave motor", with the English name "Ultrasonic Motor") is a piezoelectric motor that uses the inverse piezoelectric effect of piezoelectric materials to convert electrical energy into the vibration energy of the stator of the ultrasonic motor, and then converts the vibration energy into the rotational motion of the moving part through the friction between the driving end of the stator and the rotor. Due to its miniaturizable characteristics, the ultrasonic motor is gradually becoming more suitable as the research direction for micro-motors.

[0003] Different ultrasonic motors can be classified into parallel motion, elliptical motion, and oblique line motion according to the motion trajectory of the driving end of the stator. The driving principle of parallel motion can also be called inertial driving, that is, the rotor is driven by the asymmetric motion of the driving end. This type of motor can have a high resolution. However, during the commutation process, due to the sudden change in the direction of the frictional force and the change in the internal vibration state of the motor, it is easy to cause fluctuations in the driving torque, so it has disadvantages such as slow speed and low efficiency. The ultrasonic motor with elliptical motion is currently the most mainstream one. Usually, it requires two working modes to drive. According to whether the types of its working modes are the same, it can be further divided into traveling wave type and composite type. The composite ultrasonic motor simultaneously excites two different types of standing waves at the same frequency, which requires a high frequency consistency. Therefore, extremely high requirements are put forward for the processing accuracy of the stator under miniaturization. Although the traveling wave type ultrasonic motor inherently has good frequency consistency, it has the same problem as the composite ultrasonic motor that the excitation method is complex. Usually, the piezoelectric ceramics need to be divided into multiple zones and multiple signals need to be input, making the drive circuit complex. The ultrasonic motor with oblique line motion only requires single-phase input and a single working mode to drive the rotor to move, and can achieve simultaneous output of bidirectional motion. However, the trajectory of the oblique line motion itself is relatively complex. When switching between bidirectional motions, since there is a certain angle between the motion direction and the drive shaft of the motor, overshoot or undershoot phenomena are likely to occur at the moment of commutation, and it is difficult to accurately stop at the target position, resulting in an impact on the commutation accuracy.

[0004] In summary, the existing micro ultrasonic motors have the following disadvantages: First, they require multiple working modes with the same frequency, which has high requirements for machining accuracy and is not conducive to miniaturization; Second, they require the simultaneous input of multiple circuits, which places great demands on the driver; Third, the current motors usually can only output unidirectional motion at the same time and cannot meet some scenarios that require the simultaneous output of bidirectional motion. Therefore, there is an urgent need to design a new micro ultrasonic motor to fundamentally solve the above problems. Summary of the Invention

[0005] The present invention provides a longitudinal-torsional coaxial bidirectional rotary ultrasonic motor and an operation method thereof, which has a simple structure, fast driving speed, excellent output performance, can output bidirectional motion simultaneously, adjustable pre-pressure, and low cost.

[0006] The technical solution adopted by the present invention to solve its technical problems is:

[0007] A longitudinal-torsional coaxial bidirectional rotary ultrasonic motor includes a stator assembly and a rotor assembly. The stator assembly includes a first stator, a second stator, a flange, and 4n piezoelectric ceramic sheets, where n = 1, 2,... The rotor assembly includes a first rotor, a second rotor, and an output shaft;

[0008] One end of the output shaft is defined as the head, and the other end is defined as the bottom. The output shaft passes through the center of the flange. The 4n piezoelectric ceramic sheets are evenly divided into two groups and coaxially pasted on both sides of the flange respectively. The 2n piezoelectric ceramic sheets in each group are stacked and sleeved on the output shaft; on one side of each group of piezoelectric ceramic sheets facing the head and the bottom of the output shaft, the first stator and the second stator are bonded respectively;

[0009] A first rotor and a second rotor are respectively installed on one side of the first stator facing the head of the output shaft and one side of the second stator facing the bottom of the output shaft. The head of the output shaft is inserted into the first rotor, and the first rotor is tightly connected to the head of the output shaft; a bearing is installed between the second rotor and the output shaft. When the stator assembly vibrates under the input of a sinusoidal voltage, the first rotor will rotate clockwise and transmit to the output shaft, and the second rotor rotates counterclockwise under the support of the bearing, so that the first rotor and the second rotor can rotate in different directions respectively;

[0010] Further, a snap ring is sleeved on one side of the bearing facing the bottom of the output shaft to provide controllable pre-pressure for the ultrasonic motor;

[0011] A pre-pressure nut is screwed in from the bottom of the output shaft, and the pre-pressure nut is installed on the output shaft by means of threads;

[0012] Furthermore, 8 piezoelectric ceramic sheets are arranged in the stator assembly. The piezoelectric ceramic sheets are annular piezoelectric ceramic sheets based on the d33 effect. The piezoelectric ceramic sheets are divided into two groups and are stacked on both sides of the flange respectively. Each group of piezoelectric ceramic sheets is polarized along the thickness direction, and the polarization directions of adjacent piezoelectric ceramic sheets are opposite.

[0013] Furthermore, the first stator and the second stator have the same structure, both being hollow cylindrical structures, and a plurality of inclined grooves are evenly arranged along the outer circumference of the hollow cylindrical structure;

[0014] The inclined slots on the first stator and the second stator are close to one end of the corresponding stator. When the first stator and the second stator are distributed on both sides of the flange, the end with the inclined slots is close to the flange.

[0015] Furthermore, a boss structure is provided at the other end of the first stator and the second stator;

[0016] It is defined that during installation, one end of the first rotor and the second rotor relative to the first stator and the second stator is the bottom, and a T-shaped boss structure is arranged at the bottom of the first rotor and the second rotor. When the first rotor is tightly connected with the first stator and the second rotor is tightly connected with the second stator, the T-shaped boss structure of the first rotor is embedded in the first stator, and the T-shaped boss structure of the second rotor is embedded in the second stator, and both are connected and fixed by the bearings in the first stator and the second stator;

[0017] Furthermore, along the central axis direction of the output shaft, two adjacent piezoelectric ceramic sheets are sequentially regarded as a pair, and in each pair of piezoelectric ceramic sheets, a sinusoidal voltage is applied to the contacting surfaces, and a ground wire is connected to the non-contacting surfaces;

[0018] According to the operating method of the longitudinal-torsional coaxial bidirectional rotating ultrasonic motor, the working mode of the longitudinal-torsional coaxial bidirectional rotating ultrasonic motor is set to a first-order longitudinal-torsional mode, and a sinusoidal wave voltage is applied to 4n piezoelectric ceramic sheets to excite the set working mode, generating oblique slight vibrations in the same direction at both ends of the stator assembly relative to the head and bottom of the output shaft, and at the same time, the pre-pressure between the stator assembly and the rotor assembly drives the first rotor and the second rotor to rotate in opposite directions.

[0019] Through the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The longitudinal-torsional coaxial bidirectional rotary ultrasonic motor provided by the present invention adopts a single working mode, which effectively reduces the requirements for processing accuracy and thus reduces the manufacturing cost;

[0021] 2. The longitudinal-torsion coaxial bidirectional rotary ultrasonic motor provided by the present invention only requires a single-phase sinusoidal voltage input to excite the working mode, thereby reducing the load of the motor drive;

[0022] 3. The longitudinal-torsional coaxial bidirectional rotary ultrasonic motor provided by the present invention can convert unidirectional rotation into bidirectional rotary motion output simultaneously without a complex mechanical mechanism, providing a solution for scenarios that require bidirectional reverse rotary motion simultaneously. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below in conjunction with the drawings and embodiments.

[0024] Figure 1 is a schematic diagram of the overall structure of a preferred embodiment provided by the present invention;

[0025] Figure 2 is an exploded schematic diagram of the overall structure in a preferred embodiment provided by the present invention;

[0026] Figure 3 is a schematic diagram of the stator (the first stator or the second stator) structure in a preferred embodiment provided by the present invention;

[0027] Figure 4 is a schematic diagram of the rotor (the first rotor or the second rotor) structure in a preferred embodiment provided by the present invention;

[0028] Figure 5 is a schematic diagram of the polarization distribution of piezoelectric ceramics and the corresponding voltage excitation in a preferred embodiment provided by the present invention;

[0029] Figure 6 is a schematic diagram of the vibration mode shape in a preferred embodiment provided by the present invention.

[0030] In the figure: 1 is the stator, 2 is the rotor, 3 is the piezoelectric ceramic sheet, 4 is the flange, 5 is the output shaft, 6 is the bearing, 7 is the circlip, and 8 is the pre-pressure nut. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The present invention will now be further described in detail with reference to the drawings. In the description of the present application, it should be understood that the orientation or positional relationship indicated by terms such as "left side", "right side", "upper part", "lower part", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. "First", "second", etc. do not represent the importance of the components, so they cannot be understood as a limitation to the present invention. The specific dimensions adopted in this embodiment are only for illustrating the technical solution by way of example, and do not limit the protection scope of the present invention.

[0032] Multiple defects of existing micro ultrasonic motors are elaborated in detail in the background art. Mainly, the micro ultrasonic motors are small in size and have a compact internal structure, which makes it difficult to integrate or function some sensors and actuators for precise control. At the same time, due to miniaturization, the stator and rotor structures of the ultrasonic motors often adopt a thin and light design, which results in a relatively small driving torque that can be generated during bidirectional movement. To solve the above problems, the present application provides a longitudinal-torsional coaxial bidirectional rotary ultrasonic motor, which has a simple motor structure, small mass, high speed, and natural bidirectional movement, and can provide a solution for scenarios that require simultaneous bidirectional opposite rotary movements.

[0033] The overall structure of the longitudinal-torsional coaxial bidirectional rotary ultrasonic motor is as Figure 1 shown, including a stator assembly and a rotor assembly. Figure 2 It is an exploded view of the structure. It can be clearly seen that the stator assembly includes two stators 1, multiple piezoelectric ceramic sheets 3, and a flange 4. Similarly, the rotor assembly includes two rotors 2 and an output shaft 5. Regarding the piezoelectric ceramic sheets, generally 4n sheets are selected, where n = 1, 2,.... For the convenience of description, the two stators are respectively defined as the first stator and the second stator, the two rotors are respectively defined as the first rotor and the second rotor, one end of the output shaft is defined as the head, and the other end is defined as the bottom. The flange is sleeved on the output shaft. The 4n piezoelectric ceramic sheets are evenly divided into two groups and respectively coaxially pasted on both sides of the flange. The 2n piezoelectric ceramic sheets in each group are stacked and sleeved on the output shaft. One side of each group of piezoelectric ceramic sheets relative to the head and the bottom of the output shaft is respectively bonded to the first stator and the second stator. The first rotor and the second rotor are respectively installed on one side of the first stator relative to the head of the output shaft and one side of the second stator relative to the bottom of the output shaft. The head of the output shaft is inserted into the first rotor, and the first rotor is tightly connected to the head of the output shaft. A bearing 6 is installed between the second rotor and the output shaft.

[0034] Regarding the combination of the double stators and the double rotors, this is because when the stator assembly vibrates under the input of a sinusoidal voltage, the first rotor transmits the rotation to the output shaft, and the second rotor rotates under the support of the bearing, enabling the first rotor and the second rotor to rotate in different directions respectively, meeting the requirement of directly outputting bidirectional rotary movements simultaneously, that is, the unidirectional rotation can be converted into bidirectional rotation without using a complex mechanical structure.

[0035] As mentioned above, the present application uses 4n piezoelectric ceramic sheets, preferably 8 sheets. This is because the operation of the ultrasonic motor depends on the specific vibration mode of the stator, and the distribution and number of piezoelectric ceramic sheets will affect the vibration pattern. The 8 piezoelectric ceramic sheets are evenly divided into two groups and stacked on both sides of the flange. This layout can excite more complex vibration modes that are more conducive to the operation of the motor, providing a better driving basis for the bidirectional movement of the ultrasonic motor. At the same time, from the perspective of energy conversion, more piezoelectric ceramic sheets mean a higher electrical energy-mechanical energy conversion rate, which can improve the driving ability of the motor. However, an unlimited number of piezoelectric ceramic sheets will also affect the miniaturization of the ultrasonic motor. Obviously, the combination of 8 piezoelectric ceramic sheets can achieve bidirectional movement within a limited space and meet the driving requirements of the micro-miniature ultrasonic motor in different application scenarios.

[0036] As can be seen from Figure 2 , a snap ring 7 is sleeved on one side of the bearing relative to the bottom of the output shaft to provide a controllable pre-pressure for the ultrasonic motor; a pre-pressure nut 8 is screwed into the bottom of the output shaft. The pre-pressure nut is installed on the output shaft through threads, and the pre-pressure of the motor is adjusted by rotating the pre-pressure nut.

[0037] Another innovation of the present application is that it adopts a single working mode. Only a single-phase sinusoidal voltage input is required to excite the working mode, and then a same-direction oblique movement is generated at both driving ends on both sides of the stator assembly to drive the reverse rotation of the double rotors. The single working mode effectively reduces the requirement for machining accuracy, thereby reducing the manufacturing cost. Only a single-phase sinusoidal voltage input is required to excite the working mode, reducing the load of the motor drive. The structure for realizing the above functions is as Figure 3 shown. The first stator and the second stator are both hollow cylindrical structures. A number of inclined slots are evenly opened along the outer circumferential surface of the hollow cylindrical structure, which can convert the longitudinal vibration part transmitted by the piezoelectric ceramic stack into torsional vibration to achieve the longitudinal-torsional mode. Preferably, 8 inclined slots are opened. The inclined slots on the first stator and the second stator are close to one end of the corresponding stator. When the first stator and the second stator are distributed on both sides of the flange, the end with the inclined slots is close to the flange.

[0038] A boss structure is provided at the other end of the first stator and the second stator. The boss design can effectively increase the amplitude. Define the bottom of the first rotor and the second rotor relative to one end of the first stator and the second stator respectively during installation. A T-shaped boss structure ( Figure 4 shown) is provided at the bottom of the first rotor and the second rotor. When the first rotor is tightly connected to the first stator and the second rotor is tightly connected to the second stator, the T-shaped boss structure of the first rotor is embedded in the first stator, and the T-shaped boss structure of the second rotor is embedded in the second stator. Both are connected and fixed through the bearing bushes in the first stator and the second stator to constrain the horizontal displacement of the first rotor and the second rotor.

[0039] Matched, Figure 5 As shown, the same circuit is connected on the connecting surfaces of adjacent piezoelectric ceramic sheets. Taking the line passing through the center of each piezoelectric ceramic sheet as the center line, the two parts symmetrical with respect to the center line are defined as the two sides of the piezoelectric ceramic sheet. One side is used to connect the sine voltage, and the other side is used to connect the ground wire. The piezoelectric ceramic sheet is designed as an annular piezoelectric ceramic sheet based on the d33 effect. After being divided into two groups, they are respectively stacked on both sides of the flange. Each group of piezoelectric ceramic sheets is polarized along the thickness direction, and the polarization directions of adjacent piezoelectric ceramic sheets are opposite.

[0040] The flange provided in this application is a hollow disc as a whole. Three through holes are evenly arranged on the circumference of the disc for fixing the ultrasonic motor. The first stator, the second stator and the flange are all made of aluminum alloy, the output shaft is made of stainless steel, the piezoelectric ceramic is made of PZT-8 material, and the first rotor and the second rotor are made of polyimide.

[0041] This application further provides an operation method for the longitudinal-torsional coaxial bidirectional rotation type ultrasonic motor. It is set that the working mode of the longitudinal-torsional coaxial bidirectional rotation type ultrasonic motor is the first-order longitudinal-torsional composite vibration mode. A sine wave voltage is applied to 4n piezoelectric ceramic sheets to excite the set working mode, and diagonal micro-amplitude vibrations in the same direction are generated on the driving surfaces at both ends of the stator assembly relative to the head and bottom of the output shaft. At the same time, through the pre-pressure between the stator assembly and the rotor assembly, the first rotor and the second rotor are driven to rotate in opposite directions.

[0042] Finally, this application provides a preferred embodiment to verify the feasibility of the foregoing structure and operation method. Figure 6 It is a schematic diagram of the vibration mode of the working mode of the preferred embodiment. Its working mode is the first-order longitudinal-torsional composite vibration mode, and the frequency is 77831 Hz. By applying a sine wave voltage to the piezoelectric ceramic to excite this mode, diagonal micro-amplitude vibrations in the same direction are generated at both ends of the stator assembly. Through the pre-pressure between the stator and the rotor, the two rotors are driven to rotate in opposite directions.

[0043] In summary, the longitudinal-torsional coaxial bidirectional rotation type ultrasonic motor and the operation method provided in this application have the advantages of low manufacturing cost, simple processing technology, adjustable pre-pressure, high rotational speed, and short response time. Only a single drive source is required to drive and adjust the movement of the motor, and bidirectional movement can be output simultaneously, which has a wide application prospect in micro-miniature drive mechanisms.

[0044] Those skilled in the art can understand that, unless otherwise defined, all terms used herein (including technical terms and scientific terms) have the same meaning as the general understanding of those of ordinary skill in the field to which this application belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted in an idealized or overly formal sense unless defined as such here.

[0045] The meaning of "and / or" described in this application refers to the situation where each exists alone or both exist simultaneously.

[0046] The meaning of "connection" described in this application can be a direct connection between components or an indirect connection between components through other components.

[0047] Taking the above-mentioned ideal embodiments of the present invention as an inspiration, through the above description, relevant staff can fully make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A longitudinal-torsional coaxial bidirectional rotary ultrasonic motor, characterized in that: It comprises a stator assembly and a rotor assembly, wherein the stator assembly comprises a first stator, a second stator, a flange and 4n piezoelectric ceramic sheets, where n=1, 2, etc., and the rotor assembly comprises a first rotor, a second rotor and an output shaft; One end of the output shaft is defined as the head, and the other end is defined as the bottom. The output shaft is passed through the center of the flange. The 4n piezoelectric ceramic sheets are evenly divided into two groups, which are coaxially pasted on both sides of the flange respectively. The 2n piezoelectric ceramic sheets in each group are stacked and sleeved on the output shaft. The first stator and the second stator are respectively pasted on one side of each group of piezoelectric ceramic sheets relative to the head and the bottom of the output shaft. The first rotor and the second rotor are respectively installed on the side of the first stator relative to the output shaft head and the side of the second stator relative to the output shaft bottom. The head of the output shaft is inserted into the first rotor, and the first rotor is tightly connected to the output shaft head. A bearing is installed between the second rotor and the output shaft. When the stator assembly vibrates under sinusoidal voltage input, the first rotor will rotate clockwise and transmit it to the output shaft, and the second rotor will rotate counterclockwise supported by the bearing, so that the first rotor and the second rotor can rotate in different directions respectively.

2. The longitudinal-torsional coaxial bidirectional rotary ultrasonic motor according to claim 1, wherein: A spring retaining ring is sleeved on one side of the bearing relative to the bottom of the output shaft to provide a controllable preload for the ultrasonic motor; A pre-stress nut is screwed in from the bottom of the output shaft and is installed on the output shaft through threads.

3. The longitudinal-torsional coaxial bidirectional rotary ultrasonic motor according to claim 1, wherein: Eight piezoelectric ceramic sheets are arranged in the stator assembly. The piezoelectric ceramic sheets are annular piezoelectric ceramic sheets based on the d33 effect. They are divided into two groups and stacked on both sides of the flange respectively. Each group of piezoelectric ceramic sheets is polarized along the thickness direction, and the polarization directions of adjacent piezoelectric ceramic sheets are opposite.

4. The longitudinal-torsional coaxial bidirectional rotary ultrasonic motor according to claim 1, wherein: The first stator and the second stator have the same structure, both being hollow cylindrical structures, and a plurality of inclined grooves are evenly arranged along the outer circumference of the hollow cylindrical structure. The inclined slots on the first stator and the second stator are close to one end of the corresponding stator. When the first stator and the second stator are distributed on both sides of the flange, the end with the inclined slots is close to the flange.

5. The longitudinal-torsional coaxial bidirectional rotary ultrasonic motor according to claim 1, wherein: A boss structure is provided at the other end of the first stator and the second stator; It is defined that during installation, one end of the first rotor and the second rotor relative to the first stator and the second stator respectively is the bottom, and a T-shaped boss structure is arranged at the bottom of the first rotor and the second rotor. When the first rotor is tightly connected to the first stator and the second rotor is tightly connected to the second stator, the T-shaped boss structure of the first rotor is embedded in the first stator, and the T-shaped boss structure of the second rotor is embedded in the second stator, and both are connected and fixed by the bearings in the first stator and the second stator.

6. The longitudinal-torsional coaxial bidirectional rotary ultrasonic motor according to claim 1, characterized in that: Along the central axis direction of the output shaft, two adjacent piezoelectric ceramic sheets are sequentially regarded as a pair. In each pair of piezoelectric ceramic sheets, a sinusoidal voltage is applied to the contacting surfaces, and a ground wire is connected to the non-contacting surfaces.

7. The operating method of the longitudinal-torsional coaxial bidirectional rotary ultrasonic motor according to any one of claims 1-6, characterized in that: The working mode of the longitudinal-torsional coaxial bidirectional rotating ultrasonic motor is set to a first-order longitudinal-torsional mode. A sinusoidal wave voltage is applied to 4n piezoelectric ceramic sheets to excite the set working mode, and slight oblique vibrations in the same direction are generated at both ends of the stator assembly relative to the head and bottom of the output shaft. At the same time, the pre-pressure between the stator assembly and the rotor assembly drives the first rotor and the second rotor to rotate in opposite directions.

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