Traveling wave rotary ultrasonic motor based on in-plane bending mode

Abstract

The invention belongs to the technical field of piezoelectric driving and ultrasonic motors, and relates to a traveling wave rotary ultrasonic motor based on an in-plane bending mode, which comprises a shell, a stator assembly and a rotor, the stator assembly is arranged in the shell and comprises a stator base body and two or six piezoelectric ceramic piece groups, each piezoelectric ceramic piece group comprises one or two piezoelectric ceramic pieces, and the rotor is arranged on the stator base body. The stator base body is in a circular ring shape, the inner side face of the stator base body is arranged to be a conical face, the piezoelectric ceramic pieces are evenly distributed on the outer side face of the stator base body, the piezoelectric ceramic pieces are connected with wires used for being connected with electricity, the rotor comprises a frustum body and an output shaft, the frustum body and the stator base body are coaxial, the frustum body is arranged on the inner side of the stator base body, and the output shaft is arranged on the output shaft. The peripheral surface of the frustum body is in contact with the conical surface; excitation signals with the same amplitude and frequency within the ultrasonic range are applied to the piezoelectric ceramic pieces at the same time, the third-order vibration mode of the stator base body is excited, traveling waves moving in the circumferential direction are synthesized on the stator base body, and the frustum body is driven to rotate.

Description

Technical Field

[0001] The present invention belongs to the technical field of piezoelectric drive and ultrasonic motor, and in particular relates to a traveling wave rotary ultrasonic motor based on an in-plane bending mode. Background Art

[0002] Ultrasonic motor is a new type of micro motor that uses the inverse piezoelectric effect of piezoelectric ceramic materials to make the motor stator vibrate at ultrasonic frequencies, and uses the friction coupling between the stator and rotor to achieve rotor rotation, linear or multi-degree-of-freedom motion. Ultrasonic motors have the advantages of simple structure, high power density, fast response and no electromagnetic radiation. As a new type of micro motor, it has become a hot topic for continuous research by many scholars at home and abroad, and also has great development potential and very broad application prospects.

[0003] However, most of the existing traveling wave rotary ultrasonic motors work based on the out-of-plane bending mode. For a circular ring structure, the out-of-plane bending mode means that the vibration displacement of the particle is perpendicular to the plane of the ring. In this mode, the deformation is along the axial direction of the ring, which will cause radial slip between the stator and rotor due to poor contact stability, further affecting its output performance such as speed and torque. Summary of the invention

[0004] In view of this, the present invention provides a traveling wave rotary ultrasonic motor based on an in-plane bending mode, which can reduce the radial slip phenomenon between the stator and rotor and improve its output performance.

[0005] The technical solution of the present invention is:

[0006] A traveling wave rotary ultrasonic motor based on an in-plane bending mode comprises a housing and further comprises:

[0007] A stator assembly is arranged in the housing, the stator assembly includes a stator matrix, two or six groups of piezoelectric ceramic sheets, each group of the piezoelectric ceramic sheets includes one or two piezoelectric ceramic sheets, the stator matrix is ​​annular, the inner side surface of the stator matrix is ​​set as a conical surface, and a plurality of piezoelectric ceramic sheets are evenly arranged on the outer side surface of the stator matrix, and the piezoelectric ceramic sheets are used to receive excitation signals;

[0008] The rotor comprises a frustum body and an output shaft, wherein the frustum body is coaxial with the stator base, the frustum body is arranged on the inner side of the stator base, the outer peripheral surface of the frustum body contacts the conical surface, one side of the frustum body is fixedly connected with the output shaft, and the output shaft extends out of the housing;

[0009] In two adjacent groups of piezoelectric ceramic sheets, a sine wave excitation signal is applied to one group of piezoelectric ceramic sheets, and a cosine wave excitation signal is applied to the other group of piezoelectric ceramic sheets, so that an alternating electric field is generated to act on each piezoelectric ceramic sheet, so that the piezoelectric ceramic sheets generate expansion and contraction strains in the thickness direction, excite the third-order vibration mode of the stator matrix, synthesize traveling waves moving in a circular direction on the stator matrix, and drive the frustum and the output shaft to rotate.

[0010] Preferably, the piezoelectric ceramic sheet groups are provided in two groups, and each piezoelectric ceramic sheet group is provided with two piezoelectric ceramic sheets.

[0011] Preferably, the polarization direction of two of the piezoelectric ceramic sheets relative to the stator matrix is ​​a first direction and is excited by a sinusoidal wave excitation signal, and the polarization direction of the other two piezoelectric ceramic sheets is a second direction and is excited by a cosine wave excitation signal, the first direction is perpendicular to the second direction, and the first direction and the second direction are both perpendicular to the central axis of the stator matrix.

[0012] Preferably, the length of the arc between two adjacent piezoelectric ceramic sheets is three quarters of the wavelength of the traveling wave.

[0013] Preferably, a plurality of teeth are fixedly disposed on the inner side of the stator base, and the plurality of teeth are evenly distributed along the circumference of the stator base, and the surface of the teeth facing the center of the stator base is a part of the conical surface.

[0014] Preferably, a plurality of positioning grooves are formed on the outer peripheral surface of the stator matrix, and the piezoelectric ceramic sheets are fixed in the corresponding positioning grooves.

[0015] Preferably, the small end of the frustum body faces downward, and the output shaft is fixedly connected to the small end of the frustum body.

[0016] Preferably, the housing comprises a motor base and a motor cover, the motor cover is detachably connected to the motor base, a limiting groove is provided on the motor base, and the stator base is arranged in the limiting groove.

[0017] Preferably, the output shaft passes through the motor base, and the motor base is provided with a bearing, and the bearing is used to support the output shaft.

[0018] Preferably, a gasket is arranged in the limiting groove, the gasket is made of insulating material, and the motor seat is arranged on the gasket.

[0019] Compared with the prior art, the present invention provides a traveling wave rotary ultrasonic motor based on in-plane bending mode, which has the following beneficial effects:

[0020] By setting a circular stator base, setting the inner side of the stator base as a conical surface, setting the frustum body on the inner side of the stator base, and the outer peripheral surface of the frustum body in contact with the conical surface of the stator base, the vibration displacement of the particles on the stator base ring is along the radial direction of the ring, which can reduce the radial slip phenomenon between the stator and the rotor and improve its output performance. In addition, the frustum body and the stator base can also be set to be in contact with the conical tooth surface, which is very different from the structure of point contact between the stator and the rotor of the previous motor. In this way, the stator and the rotor can be in stable contact and energy loss can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention.

[0022] Figure 2 It is an exploded view of the overall structure of the present invention.

[0023] Figure 3 Schematic diagram of the structure of a stator assembly according to an embodiment of the present invention.

[0024] Figure 4 Schematic diagram of the polarization direction of the rotary ultrasonic motor of the present invention.

[0025] Figure 5 This is a third-order in-plane bending vibration modal diagram of the stator assembly of the rotary ultrasonic motor of the present invention.

[0026] Description of reference numerals:

[0027] 1. Motor cover; 2. Rotor; 3. Stator assembly; 4. Gasket; 5. Motor base; 6. Bearing; 31. Stator base; 32. Piezoelectric ceramic sheet. DETAILED DESCRIPTION

[0028] It should be noted that, in the description of the present invention, the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0029] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0030] In addition, it should be noted that the connections involved in the present invention can be achieved by using conventional connection methods and do not involve any innovation.

[0031] The subject of the present invention is a traveling wave rotary ultrasonic motor based on in-plane bending mode. The ultrasonic motor is a new type of micro motor that uses the inverse piezoelectric effect of piezoelectric ceramic materials to make the motor stator vibrate at ultrasonic frequencies, and uses the friction coupling between the stator and rotor to achieve rotor rotation, linear or multi-degree-of-freedom motion. Ultrasonic motors have the advantages of simple structure, high power density, fast response and no electromagnetic radiation. As a new type of micro motor, it has become a hot topic for continuous research by many scholars at home and abroad, and also has great development potential and very broad application prospects.

[0032] However, most of the existing traveling wave rotary ultrasonic motors work based on the out-of-plane bending mode. For a circular ring structure, the out-of-plane bending mode means that the vibration displacement of the particle is perpendicular to the plane of the ring. In this mode, the deformation is along the axial direction of the ring, which will cause radial slip between the stator and rotor due to poor contact stability, further affecting its output performance such as speed and torque.

[0033] Based on the above reasons, the present invention provides a traveling wave rotary ultrasonic motor based on in-plane bending mode to solve the above-mentioned technical problems. Figures 1 to 5 , the present invention is described in detail.

[0034] Example 1

[0035] This embodiment provides a traveling wave rotary ultrasonic motor based on an in-plane bending mode, including a housing, a stator assembly 3 , and a rotor 2 .

[0036] The stator assembly 3 is arranged in the shell, and the stator assembly 3 includes a stator base 31, two or six groups of piezoelectric ceramic sheets, each group of piezoelectric ceramic sheets includes one or two piezoelectric ceramic sheets 32, the stator base 31 is annular, the inner side surface of the stator base 31 is set as a conical surface, and a plurality of piezoelectric ceramic sheets 32 are evenly distributed on the outer side surface of the stator base 31. The piezoelectric ceramic sheets 32 are connected to wires for connecting electricity, and the piezoelectric ceramic sheets 32 are used to receive excitation signals.

[0037] The rotor 2 includes a frustum body and an output shaft. The frustum body is coaxial with the stator base 31. The frustum body is arranged on the inner side of the stator base 31. The outer peripheral surface of the frustum body contacts the conical surface. The output shaft is fixedly connected to one side of the frustum body and extends out of the housing.

[0038] At the same time, an excitation signal with the same amplitude and frequency within the ultrasonic range is applied to several piezoelectric ceramic sheets 32 to excite the third-order vibration mode of the stator matrix 31, synthesize a traveling wave moving in a circumferential direction on the stator matrix 31, drive the frustum body to rotate, and the frustum body drives the output shaft to rotate synchronously.

[0039] The number of piezoelectric ceramic sheets in the motor stator of the traveling wave rotary ultrasonic motor based on the in-plane bending mode is generally set according to the arc length of each group of adjacent piezoelectric ceramic sheets being one quarter of a wavelength. However, when the working mode is selected as the third-order in-plane bending vibration mode, Figure 5 The quarter wavelength of the third-order in-plane bending mode is 30°, and the three-quarter wavelength is 90°. Due to the unique symmetry of the annular structure, the in-plane vibration modes of the ultrasonic motor stator are the same when the arc lengths clamped by each adjacent group of piezoelectric ceramic sheets are one-quarter wavelength and three-quarter wavelength.

[0040] When the arc length between two adjacent piezoelectric ceramic sheets is one quarter of a wavelength, 6 piezoelectric ceramic sheets (i.e., 1 sheet in each group, for a total of 6 groups) and 12 piezoelectric ceramic sheets (i.e., 2 sheets in each group, for a total of 6 groups) can be set; when the arc length between two adjacent piezoelectric ceramic sheets is three quarters of a wavelength, 2 piezoelectric ceramic sheets (i.e., 1 sheet in each group, for a total of 2 groups) and 4 piezoelectric ceramic sheets (i.e., 2 sheets in each group, for a total of 2 groups) can be set.

[0041] The outer surface of the piezoelectric ceramic sheet 32 ​​is welded with a wire, which transmits the excitation signal to the piezoelectric ceramic sheet 32. The stator matrix 31 serves as a common ground electrode. 31 Working mode, in d 31 In the working mode, an alternating electric field is applied to the piezoelectric ceramic sheet, causing the piezoelectric ceramic sheet to generate a stretching strain in the thickness direction, thereby realizing traveling wave excitation of the stator assembly 3 .

[0042] In this embodiment, the length of the arc between two adjacent piezoelectric ceramic sheets 32 is three quarters of the wavelength of the traveling wave. Figure 4 shown.

[0043] In this embodiment, a plurality of teeth are fixedly disposed on the inner side of the stator base 31 , and the plurality of teeth are evenly distributed along the circumference of the stator base 31 , and the surface of the teeth facing the center of the stator base 31 is a part of the conical surface.

[0044] In order to improve the contact effect between the frustum body and the stator base 31 and ensure stable contact between the frustum body and the stator base 31, the frustum body is arranged with the small end facing downward, and the frustum body maintains close contact with the stator base 31 under the action of its own gravity.

[0045] The stator of the inner cone-shaped traveling wave rotary ultrasonic motor contains teeth. The processing of the tooth structure changes the geometric shape of the stator and adjusts the stiffness distribution of the stator, which is beneficial to amplify the vibration amplitude and vibration efficiency of the particles on the inner surface of the cone in the circumferential direction, thereby increasing the speed of the ultrasonic motor. In addition, the tooth gap can accommodate fine chips generated by friction when the motor is running and play a role in heat dissipation.

[0046] In order to fix the piezoelectric ceramic sheets 32, the outer peripheral surface of the stator base 31 is provided with a plurality of positioning grooves, and the piezoelectric ceramic sheets 32 are fixed in the corresponding positioning grooves. The four piezoelectric ceramic sheets 32 are bonded and fixed to the stator base 31 by an adhesive made of a 1:1 mixture of epoxy resin and polyamide resin.

[0047] In this embodiment, the shell includes a motor base 5 and a motor cover 1. The motor base 5 is detachably connected to the motor cover 1. An accommodating cavity is formed between the motor cover 1 and the motor base 5. The stator assembly 3 and the frustum body are both arranged in the accommodating cavity.

[0048] In this embodiment, an output shaft is fixedly connected to one end of the frustum body. The output shaft passes through the accommodating cavity on the motor base 5. A bearing 6 is provided on the motor base 5 to support the output shaft.

[0049] In order to improve stability, a limiting groove is provided on the motor base 5 , and a gasket 4 is arranged in the limiting groove. The gasket 4 is fixed to the motor base 5 and the stator base 31 .

[0050] The size of the motor seat 5 of the present invention is larger than the size of the stator assembly 3. The stator assembly 3 is placed in the stator assembly positioning groove of the electrode seat through the gasket 4 to ensure the stability of the stator assembly 3 during operation. The gasket 4 is made of rubber material.

[0051] Figure 5 It is the third-order in-plane bending mode of the ultrasonic motor stator with the same frequency, shape and orthogonality, which is a necessary condition for synthesizing traveling waves on the ultrasonic motor stator.

[0052] Working principle of this embodiment

[0053] In this specific embodiment, the sinusoidal wave excitation signal of the third-order vibration mode (approximately 22kHz in this specific embodiment) is abbreviated as sin(wt), and the cosine wave excitation signal is abbreviated as cos(wt); when the input signal of the two piezoelectric ceramic sheets 32 in the vertical direction of the stator matrix 31 is sin(wt), and the input signal of the two piezoelectric ceramic sheets 32 in the horizontal direction of the stator matrix 31 is cos(wt), the stator matrix 31 is excited by the piezoelectric ceramic sheets 32 to produce a two-phase standing wave of the third-order vibration mode, and both of the two-phase standing waves satisfy the difference of π / 2 between the spatial phase and the time phase, so that a traveling wave moving in a circular direction can be synthesized on the stator assembly 3, and the traveling wave pushes the particles on the stator surface to move along its own elliptical trajectory, and the elliptical trajectory motion of the particles and the friction of the contact surface between the stator and the rotor jointly drive the frustum to rotate, meeting the normal working requirements of the traveling wave rotary ultrasonic motor.

[0054] The rotor 2 of the present invention is a frustum-shaped structure with an output shaft at the bottom. Under the pre-pressure generated by the weight of the rotor 2 (approximately 0.1N in this specific embodiment), the friction coupling between the stator assembly 3 and the rotor 2 is used to achieve stable output of the rotor 2 speed and torque.

[0055] Example 2

[0056] Different from the first embodiment, in order to improve the output performance of the ultrasonic motor, the present embodiment has two piezoelectric ceramic sheet groups, each of which has two piezoelectric ceramic sheets 32 .

[0057] Since the solution of setting one piezoelectric ceramic sheet in each group will destroy the symmetry of the ultrasonic motor stator, and the number of piezoelectric ceramic sheets is not the more the better, too many piezoelectric ceramic sheets will affect the effective electromechanical coupling coefficient, mechanical quality factor and impedance of the ultrasonic motor stator. Therefore, considering all aspects, the number of piezoelectric ceramic sheets of the traveling wave rotary ultrasonic motor based on the in-plane bending mode in this patent is selected as 4.

[0058] In this embodiment, the polarization direction of two piezoelectric ceramic sheets 32 opposite to the stator matrix 31 is a first direction and is excited by a sine wave excitation signal, and the polarization direction of the other two piezoelectric ceramic sheets 32 is a second direction and is excited by a cosine wave excitation signal. The first direction is perpendicular to the second direction, and both the first direction and the second direction are perpendicular to the central axis of the stator matrix 31.

[0059] like Figure 4 As shown, the polarization direction of the two piezoelectric ceramic sheets in the vertical direction of the stator base 31 is vertically downward, and they are excited by the sinusoidal wave excitation signal.

[0060] like Figure 4 As shown, the polarization direction of the two piezoelectric ceramic sheets in the horizontal direction of the stator base 31 is horizontal to the right, and is excited by the cosine wave excitation signal.

[0061] The above disclosure is only a preferred specific embodiment of the present invention, but the embodiments of the present invention are not limited thereto, and any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A traveling wave rotary ultrasonic motor based on an in-plane bending mode, comprising a housing, characterized in that: Also includes: A stator assembly (3) is arranged in the housing, the stator assembly (3) comprising a stator base (31), two or six groups of piezoelectric ceramic sheets, each group of the piezoelectric ceramic sheets comprising one or two piezoelectric ceramic sheets (32), the stator base (31) being annular, the inner side surface of the stator base (31) being arranged as a conical surface, a plurality of the piezoelectric ceramic sheets (32) being evenly arranged on the outer side surface of the stator base (31), and the piezoelectric ceramic sheets (32) being used to receive an excitation signal; The rotor (2) comprises a frustum body and an output shaft, wherein the frustum body is coaxial with the stator base (31), the frustum body is arranged on the inner side of the stator base (31), the outer peripheral surface of the frustum body is in contact with the conical surface, one side of the frustum body is fixedly connected to the output shaft, and the output shaft extends out of the housing; In two adjacent groups of piezoelectric ceramic sheets, a sine wave excitation signal is applied to one group of piezoelectric ceramic sheets, and a cosine wave excitation signal is applied to the other group of piezoelectric ceramic sheets, so that an alternating electric field is generated to act on each piezoelectric ceramic sheet, causing the piezoelectric ceramic sheet to generate a stretching strain in the thickness direction, thereby exciting the third-order vibration mode of the stator matrix (31), synthesizing a traveling wave moving in a circumferential direction on the stator matrix (31), and driving the frustum body and the output shaft to rotate.

2. The traveling wave rotary ultrasonic motor based on in-plane bending mode according to claim 1, characterized in that: The piezoelectric ceramic sheet groups are arranged in two groups, and each group of piezoelectric ceramic sheet groups is arranged with two piezoelectric ceramic sheets (32).

3. The traveling wave rotary ultrasonic motor based on in-plane bending mode according to claim 2, characterized in that: Two of the piezoelectric ceramic sheets (32) opposite to the stator matrix (31) have a polarization direction of a first direction and are excited by a sine wave excitation signal, and the other two piezoelectric ceramic sheets (32) have a polarization direction of a second direction and are excited by a cosine wave excitation signal, the first direction is perpendicular to the second direction, and the first direction and the second direction are both perpendicular to the central axis of the stator matrix (31).

4. The traveling wave rotary ultrasonic motor based on in-plane bending mode according to claim 1, characterized in that: The length of the arc between two adjacent piezoelectric ceramic sheets (32) is three quarters of the wavelength of the traveling wave.

5. The traveling wave rotary ultrasonic motor based on in-plane bending mode according to claim 1, characterized in that: A plurality of teeth are fixedly arranged on the inner side of the stator base (31), and the plurality of teeth are evenly distributed along the circumference of the stator base (31), and the surface of the teeth facing the center of the stator base (31) is a part of the conical surface.

6. The traveling wave rotary ultrasonic motor based on in-plane bending mode according to claim 1, characterized in that: The outer peripheral surface of the stator base body (31) is provided with a plurality of positioning grooves, and the piezoelectric ceramic sheets (32) are fixed in the corresponding positioning grooves.

7. The traveling wave rotary ultrasonic motor based on in-plane bending mode according to claim 1, characterized in that: The small end of the frustum body faces downward, and the output shaft is fixedly connected to the small end of the frustum body.

8. The traveling wave rotary ultrasonic motor based on in-plane bending mode according to claim 1, characterized in that: The housing comprises a motor base (5) and a motor cover (1); the motor cover (1) is detachably connected to the motor base (5); a limiting groove is provided on the motor base (5); and the stator base (31) is arranged in the limiting groove.

9. The traveling wave rotary ultrasonic motor based on in-plane bending mode according to claim 8, characterized in that: The output shaft passes through the motor seat (5), and a bearing (6) is provided on the motor seat (5), and the bearing (6) is used to support the output shaft.

10. The traveling wave rotary ultrasonic motor based on in-plane bending mode according to claim 8, characterized in that: A gasket (4) is arranged in the limiting groove, the gasket (4) is made of insulating material, and the motor seat (5) is arranged on the gasket (4).

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