Hollow type rotary piezoelectric motor and its operation method

Abstract

The application discloses a hollow type rotary piezoelectric motor and a working method thereof, and the motor comprises a rotor, a first bearing, a second bearing, a shell, a base, a stator and a piezoelectric driving module; the stator comprises a fixing ring, three fixing bases, three connecting rods and three driving feet; the piezoelectric driving module comprises six driving units, and each driving unit comprises two piezoelectric bimorphs; the rotor realizes bidirectional super-high-precision positioning rotary motion by controlling the time sequence and frequency of the six driving units, and can realize large torque at low speed and high-precision rotation at high speed; the application has high reliability, large output torque and high precision, and can be widely applied in the fields of precision optics, aerospace, mechanical manufacturing and medical devices.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of piezoelectric precision driving, and particularly relates to a hollow rotary piezoelectric motor and a working method thereof. BACKGROUND

[0002] The rotary ultrasonic motor is a kind of driver based on piezoelectric effect, ultrasonic vibration and friction coupling. It has extremely wide application in the field of mechanical manufacturing due to its fast response speed, high precision and large quality moment ratio. However, the stator structure cannot pass through the optical beam and the precision mechanical arm, which greatly limits the application range of the rotary ultrasonic motor. The hollow ultrasonic motor can be applied to the field of precision optics and medical instruments due to its unique hollow structure. However, the existing hollow rotary ultrasonic motor structure and driving signal are relatively complex, and the input voltage signal wave frequency band is limited, which brings challenges to the simplified design of piezoelectric driving. Therefore, how to solve the problems of complex structure and driving signal of the existing hollow rotary ultrasonic motor, simplify the structure of the hollow rotary ultrasonic motor, meet the input voltage frequency from low to high, and realize the macro-micro driving fusion driving of the stator in the non-resonance mode and the resonance mode has become a difficult problem to be studied in the industry. SUMMARY

[0003] The present application relates to the technical field of piezoelectric precision driving, and particularly relates to a hollow rotary piezoelectric motor and a working method thereof.

[0004] The present application adopts the following technical solutions to solve the above technical problems:

[0005] A hollow rotary piezoelectric motor, comprising a rotor, a first bearing, a second bearing, a shell, a base, a stator and a piezoelectric driving module.

[0006] The rotor is a hollow cylinder with open ends, the first bearing is a deep groove ball bearing, and the second bearing is a thrust bearing.

[0007] The shell is fixed on the base, the outer ring of the first bearing is fixed with the shell, the inner ring is coaxially fixed with the outer wall of the rotor, the lower ring of the second bearing is fixed with the base, and the upper ring is coaxially fixed with the lower end of the bearing, so that the rotor can freely rotate relative to the base.

[0008] The stator comprises a fixed ring, three fixed seats, three connecting rods and three driving feet.

[0009] The fixed ring is a hollow cylinder with open ends, and the three fixed seats are uniformly arranged on the outer wall of the fixed ring and are fixed with the base, so that the fixed ring is located in the rotor and is coaxial with the rotor.

[0010] The three connecting rods are evenly arranged circumferentially between the fixed ring and the rotor, with one end fixed to the outer wall of the fixed ring and the other end fixed to the three driving feet respectively; the three driving feet abut against the inner wall of the rotor; the three fixed seats and the three connecting rods divide the fixed ring into six equal parts, and the first fixed seat is located between the first connecting rod and the second connecting rod;

[0011] Dovetail grooves are provided on both sides of the three fixed seats and the three driving feet;

[0012] The piezoelectric driving module includes six driving units, which are respectively disposed between the first driving foot and the first fixed base, the first fixed base and the second driving foot, the second driving foot and the second fixed base, the second fixed base and the third driving foot, the third driving foot and the third fixed base, and the third fixed base and the first driving foot. Each of these units includes a first piezoelectric bicrystalline wafer and a second piezoelectric bicrystalline wafer, wherein the first piezoelectric bicrystalline wafer is located inside the second piezoelectric bicrystalline wafer. One end of both the first and second piezoelectric bicrystalline wafers abuts against the dovetail groove on the driving foot corresponding to their respective driving unit, and the other end abuts against the dovetail groove on the fixed base corresponding to their respective driving unit, such that the first piezoelectric bicrystalline wafer protrudes inward and the second piezoelectric bicrystalline wafer protrudes outward.

[0013] The first and second piezoelectric bicrystalline wafers of the six driving units are coplanar, and their planes are perpendicular to the rotor's axis of rotation.

[0014] In the six driving units, the piezoelectric ceramic sheets on both sides of the first piezoelectric bicrystalline wafer are polarized along their thickness direction, with the polarization direction simultaneously facing inward or outward; in the six driving units, the piezoelectric ceramic sheets on both sides of the second piezoelectric bicrystalline wafer are polarized along their thickness direction, with the polarization direction opposite to that of the piezoelectric ceramic sheets on both sides of the first piezoelectric bicrystalline wafer in the six driving units.

[0015] As a further optimization of the hollow rotary piezoelectric motor of the present invention, all three drive feet are made of flexible material.

[0016] As a further optimization of the hollow rotary piezoelectric motor of the present invention, the outer sides of the three driving feet are provided with a friction layer made of ceramic material to improve friction performance and wear resistance.

[0017] The present invention also discloses a method for operating the hollow rotary piezoelectric motor, comprising the following steps:

[0018] A) If it is necessary to drive the rotor to rotate in the forward direction:

[0019] Voltage signal waves u1, u2, u3, u4, u5, and u6 with the same signal amplitude and frequency but different phases are input to the first to sixth drive units. The phases of the electrical signals u1, u2, u3, u4, u5, and u6 are successively 60° apart. This causes the first and second piezoelectric double crystals in the six drive units to bend simultaneously, generating longitudinal tensile forces of the same frequency. This, in turn, causes the three drive feet to generate positive elliptical motion. The driving surfaces of the three drive feet have completely consistent running trajectories and driving directions, with only a phase difference in time. Under the synergistic effect of the three drive feet, the rotor obtains continuous positive output torque.

[0020] B) If it is necessary to drive the rotor to rotate in the opposite direction:

[0021] Voltage signal waves u1, u2, u3, u4, u5, and u6 with the same signal amplitude and frequency but different phases are input to the first to sixth drive units. The electrical signal phases of u6, u5, u4, u3, u2, and u1 are successively 60° apart. This causes the first and second piezoelectric bicrystalline wafers in the six drive units to bend simultaneously, generating longitudinal tensile forces of the same frequency. This, in turn, causes the three drive feet to produce elliptical motions in opposite directions. The driving surfaces of the three drive feet have completely consistent running trajectories and driving directions, with only a phase difference in time. Under the synergistic effect of the three drive feet, the rotor obtains continuous output torque in the opposite direction.

[0022] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0023] 1. This invention adopts a unique hollow structure and simplifies the design of the hollow rotary piezoelectric motor structure through 6 drive units, making it suitable for fields such as precision optics and medical devices that require hollow structures;

[0024] 2. Because the present invention uses a piezoelectric dual crystal assembly as the excitation source, the driving unit and the driving foot are non-fixed and are embedded in the dovetail groove of the driving foot and the fixed base. Therefore, it has a fast response speed and high accuracy, and its performance can be adjusted by changing the input frequency, voltage and driving mode.

[0025] 3. This invention is equipped with 6 driving units. By adjusting the amplitude and frequency of the input voltage, the ultrasonic motor can switch between resonant mode and non-resonant mode to achieve macro-micro fusion driving. Attached Figure Description

[0026] Figure 1 This is a top view of the present invention;

[0027] Figure 2 This is a cross-sectional view of the present invention;

[0028] Figure 3This is a schematic diagram of the structure of the stator and piezoelectric drive module in this invention.

[0029] Figure 4 This is a schematic diagram of the six-phase drive signal when the rotor is driven to rotate in the forward direction according to the present invention;

[0030] Figure 5 This is a schematic diagram of the six-phase drive signal when the rotor is driven to rotate in the reverse direction according to the present invention;

[0031] Figure 6 This is a deformation displacement cloud diagram of the stator when the rotor is driven to rotate in the forward direction according to the present invention;

[0032] Figure 7 This is a deformation displacement cloud diagram of the stator when the rotor is driven to rotate in the opposite direction according to the present invention.

[0033] In the figure, 1-shell, 2-rotor, 3-stator, 4-base, 5-first bearing, 6-second bearing, 7-fixed ring, 8-drive foot, 9-fixed seat, 10-connecting rod, 11-first piezoelectric bicrystalline wafer, 12-second piezoelectric bicrystalline wafer. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings:

[0035] This invention can be implemented in many different forms and should not be considered limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully express the scope of the invention to those skilled in the art. In the drawings, components are enlarged for clarity.

[0036] like Figure 1 , Figure 2 As shown, the present invention discloses a hollow rotary piezoelectric motor, comprising a rotor, a first bearing, a second bearing, a housing, a base, a stator, and a piezoelectric drive module;

[0037] The rotor is a hollow cylinder with openings at both ends. The first bearing is a deep groove ball bearing, and the second bearing is a thrust bearing.

[0038] The outer casing is fixed to the base; the outer ring of the first bearing is fixedly connected to the outer casing, and the inner ring is coaxially fixedly connected to the outer wall of the rotor; the lower ring of the second bearing is fixedly connected to the base, and the upper ring is coaxially fixedly connected to the lower end of the bearing, so that the rotor can rotate freely relative to the base.

[0039] like Figure 3 As shown, the stator includes a fixed ring, three fixed seats, three connecting rods, and three driving feet;

[0040] The fixing ring is a hollow cylinder with open ends; the three fixing seats are evenly arranged on the outer wall of the fixing ring and are all fixedly connected to the base, so that the fixing ring is located inside the rotor and is coaxial with the rotor.

[0041] The three connecting rods are evenly arranged circumferentially between the fixed ring and the rotor, with one end fixed to the outer wall of the fixed ring and the other end fixed to the three driving feet respectively; the three driving feet abut against the inner wall of the rotor; the three fixed seats and the three connecting rods divide the fixed ring into six equal parts, and the first fixed seat is located between the first connecting rod and the second connecting rod;

[0042] Dovetail grooves are provided on both sides of the three fixed seats and the three driving feet;

[0043] The piezoelectric driving module includes six driving units, which are respectively disposed between the first driving foot and the first fixed base, the first fixed base and the second driving foot, the second driving foot and the second fixed base, the second fixed base and the third driving foot, the third driving foot and the third fixed base, and the third fixed base and the first driving foot. Each of these units includes a first piezoelectric bicrystalline wafer and a second piezoelectric bicrystalline wafer, wherein the first piezoelectric bicrystalline wafer is located inside the second piezoelectric bicrystalline wafer. One end of both the first and second piezoelectric bicrystalline wafers abuts against the dovetail groove on the driving foot corresponding to their respective driving unit, and the other end abuts against the dovetail groove on the fixed base corresponding to their respective driving unit, such that the first piezoelectric bicrystalline wafer protrudes inward and the second piezoelectric bicrystalline wafer protrudes outward.

[0044] The first and second piezoelectric bicrystalline wafers of the six driving units are coplanar, and their planes are perpendicular to the rotor's axis of rotation.

[0045] In the six driving units, the piezoelectric ceramic sheets on both sides of the first piezoelectric bicrystalline wafer are polarized along their thickness direction, with the polarization direction simultaneously facing inward or outward; in the six driving units, the piezoelectric ceramic sheets on both sides of the second piezoelectric bicrystalline wafer are polarized along their thickness direction, with the polarization direction opposite to that of the piezoelectric ceramic sheets on both sides of the first piezoelectric bicrystalline wafer in the six driving units.

[0046] All three drive feet are made of flexible material; the outer side of each of the three drive feet is provided with a friction layer made of ceramic material to improve friction performance and wear resistance.

[0047] The present invention also discloses a method for operating the hollow rotary piezoelectric motor, comprising the following steps:

[0048] A) If it is necessary to drive the rotor to rotate in the forward direction:

[0049] like Figure 4As shown, for voltage signal waves u1, u2, u3, u4, u5, and u6 with the same signal amplitude and frequency but different phases input to the 1st to 6th drive units, the formula can be expressed in the following form:

[0050] u i =V i f i

[0051] The electrical signals u1, u2, u3, u4, u5, and u6 are sequentially 60° out of phase, and are represented as follows:

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

[0058] A positive voltage is applied to the driving unit, causing the symmetrically excited first and second piezoelectric bicrystalline wafers in the driving unit to simultaneously produce bending vibrations. The symmetrically arranged first and second piezoelectric bicrystalline wafers with opposite polarization directions in each driving unit simultaneously receive a voltage input (u). i The voltage signal wave, the vibration of the first and second piezoelectric bicrystalline wafers has no time phase difference, and the two ends of the driving unit generate longitudinal tensile forces of the same frequency. According to Figure 6 As shown, taking the first driving foot as an example, the phase difference between the voltage signal waves u1 and u2 of the driving units at the left and right ends of the driving foot is... The two ends of the drive unit generate longitudinal tensile forces with different time phase differences, which causes the drive foot to produce positive elliptical motion. The elliptical motion causes the contact state between the drive surface of the drive foot and the rotor to be divided into four states according to the time step sequence: disengagement, pre-contact, full contact, and pre-disengagement.

[0059] The driving surface of the driving foot forms an elliptical trajectory with a circumference of x1. Based on the friction coefficient of the contact surface and the size of the elliptical trajectory, the rotation efficiency of the driving rotor is μ1. Each step of the elliptical motion is transmitted to the rotor friction surface with an effective step length of μ1x1. The driving rotor rotates in the positive direction around the axis. After waiting for a preset time t1 seconds, the driving foot has performed λ1 elliptical motions. The effective step length of the rotor's positive rotation is λ1μ1x1.

[0060] The driving surfaces of the three driving feet have the same trajectory and driving direction, with only a phase difference in time. Therefore, under the synergistic effect of the three driving feet, the rotor obtains continuous positive output torque.

[0061] B) If it is necessary to drive the rotor to rotate in the opposite direction:

[0062] like Figure 5 As shown, for voltage signal waves u1, u2, u3, u4, u5, and u6 with the same signal amplitude and frequency but different phases input to the 1st to 6th drive units, the formula can be expressed in the following form:

[0063] u i =V i f i

[0064] The electrical signals u6, u5, u4, u3, u2, and u1 are sequentially 60° out of phase, and are represented as follows:

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071] A positive voltage is applied to the driving unit, causing the symmetrically excited first and second piezoelectric bicrystalline wafers in the driving unit to simultaneously produce bending vibrations. The two symmetrically arranged first and second piezoelectric bicrystalline wafers with opposite polarization directions in each driving unit are simultaneously input to u. i The voltage signal wave, the vibration of the first and second piezoelectric bicrystalline wafers has no time phase difference, and the two ends of the driving unit generate longitudinal tensile forces of the same frequency. According to Figure 7 As shown, taking the first driving foot as an example, the phase difference between the voltage signal waves u1 and u2 of the driving units at the left and right ends of the driving foot is... The two ends of the drive unit generate longitudinal tensile forces with different time phase differences, causing the drive foot to produce an elliptical motion in the opposite direction. The elliptical motion causes the contact state between the drive surface of the drive foot and the rotor to be divided into four states according to the time step sequence: disengagement, pre-contact, full contact, and pre-disengagement.

[0072] The driving surface of the driving foot forms an elliptical trajectory with a circumference of x2. Based on the friction coefficient of the contact surface and the size of the elliptical trajectory, the rotation efficiency of the driving rotor is μ2. Each step of the elliptical motion is transmitted to the rotor friction surface with an effective step length of μ2x2. The driving rotor rotates in the opposite direction around the axis. After waiting for a preset time t2 seconds, the driving foot has performed λ2 elliptical motions. The effective step length of the rotor's reverse rotation is λ2μ2x2.

[0073] The driving surfaces of the three driving feet have the same running trajectory and driving direction, with only a phase difference in time. Under the coordinated action of the three driving feet, the rotor obtains continuous output torque in the opposite direction.

[0074] By adjusting the voltage amplitude and frequency, the step size of each driven elliptical motion and the time required to complete one elliptical motion can be changed, thereby altering the rotor's rotational speed. The voltage amplitude is adjusted within the permissible range of preventing breakage of the piezoelectric bicrystalline wafers used; in the experimental embodiment, the voltage amplitude ranges from 0 to 500 Vpp. The adjusted voltage frequency can satisfy requirements from low to high frequencies; in the experimental embodiment, the voltage frequency ranges from 0 to 20 kHz, thus enabling the motor to operate in both non-resonant and resonant modes, achieving macro-micro fusion drive.

[0075] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0076] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A hollow type rotary piezoelectric motor characterized by comprising: The rotor, the first bearing, the second bearing, the shell, the base, the stator and the piezoelectric driving module are included. The rotor is a hollow cylinder with open ends, the first bearing is a deep groove ball bearing, and the second bearing is a thrust bearing. The shell is fixed on the base, the outer ring of the first bearing is fixed with the shell, and the inner ring is coaxially fixed with the outer wall of the rotor, and the lower ring of the second bearing is fixed with the base, and the upper ring is coaxially fixed with the lower end of the bearing, so that the rotor can freely rotate relative to the base. The stator includes a fixed ring, three fixed seats, three connecting rods and three driving feet. The fixed ring is a hollow cylinder with open ends, and the three fixed seats are evenly arranged on the outer wall of the fixed ring and are fixed with the base, so that the fixed ring is located in the rotor and coaxial with the rotor. The three connecting rods are evenly arranged between the fixed ring and the rotor, one end of each connecting rod is fixed with the outer wall of the fixed ring, and the other end is fixed with one of the three driving feet; the three driving feet are in contact with the inner wall of the rotor; the three fixed seats and the three connecting rods divide the fixed ring into six equal parts, and the first fixed seat is located between the first and second connecting rods. Both sides of the three fixed seats and the three driving feet are provided with dovetail grooves. The piezoelectric driving module includes six driving units, which are respectively arranged between the first driving foot and the first fixed seat, the first fixed seat and the second driving foot, the second driving foot and the second fixed seat, the second fixed seat and the third driving foot, the third driving foot and the third fixed seat, and the third fixed seat and the first driving foot, and each driving unit includes a first piezoelectric bimorph and a second piezoelectric bimorph, wherein the first piezoelectric bimorph is located inside the second piezoelectric bimorph; one end of each piezoelectric bimorph is in contact with the dovetail groove on the corresponding driving foot of the driving unit, and the other end is in contact with the dovetail groove on the corresponding fixed seat of the driving unit, so that the first piezoelectric bimorph protrudes inward, and the second piezoelectric bimorph protrudes outward. The first piezoelectric bimorph and the second piezoelectric bimorph of the six driving units are coplanar, and the plane thereof is perpendicular to the rotation axis of the rotor. The piezoelectric ceramic sheets on both sides of the first piezoelectric bimorph in the six driving units are polarized along the thickness direction, and the polarization directions are inward or outward at the same time; the piezoelectric ceramic sheets on both sides of the second piezoelectric bimorph in the six driving units are polarized along the thickness direction, and the polarization directions are opposite to those of the piezoelectric ceramic sheets on both sides of the first piezoelectric bimorph in the six driving units.

2. The hollow-type rotary piezoelectric motor according to claim 1, characterized by The three driving feet are made of flexible material.

3. The hollow type rotary piezoelectric motor according to claim 1, characterized by The outer side of each driving foot is provided with a friction layer made of ceramic material to improve the friction performance and wear resistance.

4. The operating method of the hollow-type rotary piezoelectric motor according to claim 1, characterized by The method comprises the following steps: A) If the rotor needs to be driven to rotate forward: The voltage signal waves u1, u2, u3, u4, u5, u6, u1, u2, u3, u4, u5, u6 of the same signal amplitude and frequency and different phases input into the first to sixth driving units are 60° apart in phase, so that the first and second piezoelectric bimorphs in the six driving units produce bending vibration at the same time, generate longitudinal tensile force of the same frequency, and further make the three driving feet produce forward elliptical motion, the driving surface running track and driving direction of the three driving feet are completely consistent, only have a phase difference in time, under the synergistic effect of the three driving feet, the rotor obtains continuous forward direction output torque; B) If the rotor needs to be driven to rotate reversely: The voltage signal waves u1, u2, u3, u4, u5, u6, u6, u5, u4, u3, u2, u1 of the same signal amplitude and frequency and different phases input into the first to sixth driving units are 60° apart in phase, so that the first and second piezoelectric bimorphs in the six driving units produce bending vibration at the same time, generate longitudinal tensile force of the same frequency, and further make the three driving feet produce reverse elliptical motion, the driving surface running track and driving direction of the three driving feet are completely consistent, only have a phase difference in time, under the synergistic effect of the three driving feet, the rotor obtains continuous reverse direction output torque.

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