Flat plate resonant inertia linear ultrasonic motor

Abstract

This invention relates to a planar resonant inertial linear ultrasonic motor. The stator assembly includes a stator and piezoelectric ceramics. The stator is a rectangular disk-shaped metal substrate, comprising stator teeth, stator tooth bases, flexible webs, and fixed webs. Each long side of the stator tooth base is connected to the fixed web via the flexible web. Several piezoelectric ceramics are adhered to the bottom surface of the stator tooth base. Excitation of the piezoelectric ceramics causes the stator tooth base to produce longitudinal bending vibrations. Stator teeth are arranged at the nodes where bending vibrations occur on the surface of the stator tooth base. The mover assembly includes a mover and friction material. When the mover assembly is placed on the surface of the stator assembly, the friction material presses against the surface of the stator teeth, applying preload to the mover. The stator drives the mover to slide through friction, utilizing the principle of inertia to cause displacement of the mover. This invention's motor has a simple stator-motor structure, a large working bandwidth, and irreplaceable advantages in space-constrained applications.

Description

Technical Field

[0001] This invention relates to a planar resonant inertial linear ultrasonic motor, belonging to the field of ultrasonic motors. Background Technology

[0002] An ultrasonic motor (also known as an "ultrasonic motor") is a piezoelectric motor that utilizes the inverse piezoelectric effect of piezoelectric materials to convert electrical energy into the vibrational energy of the stator. This vibrational energy is then converted into rotational or linear motion of the moving parts through friction. Compared to traditional electromagnetic motors, ultrasonic motors have many characteristics and advantages, such as: 1. Compact structure, high energy density (torque / mass), and ease of miniaturization. 2. Low speed and high torque, eliminating the need for gear reduction mechanisms and enabling direct drive. 3. Fast motor response and self-locking upon power failure. 4. Good position and speed control and high displacement resolution. 5. Ultrasonic motors convert energy through vibration and friction, generating no magnetic field during the conversion process and are unaffected by external magnetic field interference, exhibiting strong resistance to electromagnetic interference. 6. Quiet and noiseless operation. Operating in the ultrasonic frequency band, ultrasonic motors can operate quietly and without noise because they do not require gears or other reduction mechanisms. 7. Flexible design and diverse structural forms.

[0003] Ultrasonic motors are characterized by their light weight, compact structure, and low driving voltage, making them particularly suitable for direct driving of equipment and mechanisms without the need for a reduction gear. Among them, inertial ultrasonic motors are a type of ultrasonic motor that operates using the inverse piezoelectric effect and the principle of inertia. Under a specific excitation voltage, the stator and rotor of this type of motor perform a reciprocating motion of "slow advance, fast return." Compared to other ultrasonic motors, inertial ultrasonic motors have a simpler structure and more flexible design, but they have higher requirements for friction materials and driving signals. For example, in 1992, Sugawara et al. published a metal-ceramic composite piezoelectric actuator named "ball-type," which can convert the radial displacement of a piezoelectric ceramic element into axial displacement and amplify the displacement by about 10 times. Aydin Dogan et al. from the International Center for Actuators and Transducers at Pennsylvania State University developed a cymbal-type brake, consisting of a cylindrical piezoelectric ceramic element sandwiched between two truncated conical metal caps, which produces a displacement approximately 40 times that of a ceramic element of the same size.

[0004] However, existing inertial motors have the following drawbacks: 1. Currently, most existing inertial ultrasonic motors are non-resonant inertial ultrasonic motors, which mainly increase the amplitude of the drive end through the stacking of piezoelectric ceramics and special displacement amplification structures. In the non-resonant state, the response of the stator drive end depends on the response characteristics of the piezoelectric ceramics. Piezoelectric ceramics are inherently capacitive loads, and the stacking of piezoelectric ceramics makes their capacitive load characteristics even more prominent, making it difficult for the stator drive end to achieve an ideal response.

[0005] 2. Traditional inertial ultrasonic motors require special displacement amplification structures to increase the amplitude at the stator drive end. Due to their complex structure and high precision requirements, errors are easily caused during manufacturing, leading to substandard performance.

[0006] 3. Currently existing inertial linear ultrasonic motors are usually rod-shaped with an annular mover sleeved on the outside of the rod, which makes the preload adjustment process quite complicated.

[0007] 4. In order to avoid the stator fixing affecting its vibration effect, a complex clamping device is usually required, which makes the design and manufacturing of the motor more complicated.

[0008] Therefore, there is an urgent need to design a new inertial ultrasonic motor to fundamentally solve the above problems. Summary of the Invention

[0009] This invention provides a planar resonant inertial linear ultrasonic motor, which has stable driving speed, excellent output performance, and low cost.

[0010] The technical solution adopted by this invention to solve its technical problem is: A planar resonant inertial linear ultrasonic motor includes a stator assembly and a mover assembly disposed on its surface. The stator assembly includes a stator and piezoelectric ceramics. The stator is a metal substrate with a rectangular disk structure. The metal substrate includes stator teeth, stator tooth bases, flexible webs, and fixed webs. The stator tooth bases include two long sides, each of which is connected to the fixed webs through a flexible web. The stator tooth bases and the fixed webs have different cross-sectional thicknesses, and there is a difference in cross-sectional thickness after the stator tooth bases and the fixed webs are connected by the flexible webs. The piezoelectric ceramic is a rectangular piezoelectric ceramic sheet based on the d31 effect. Several piezoelectric ceramics are attached to the bottom surface of the stator tooth base. The piezoelectric ceramics are excited to cause the stator tooth base to generate longitudinal bending vibration. Stator teeth are arranged at the node position where bending vibration occurs on the surface of the stator tooth base, and the stator teeth are arranged perpendicular to the long side of the stator tooth base, which can convert the longitudinal bending vibration into the lateral displacement of the stator tooth drive end. The mover assembly includes a mover and friction material. When the mover assembly is arranged on the surface of the stator assembly, the friction material is pressed on the surface of the stator teeth to apply a preload to the mover. The stator drives the mover to slide through friction and uses the principle of inertia to make the mover displace. As a further preferred embodiment of the present invention, the stator teeth include three, one of which is located in the middle of the stator tooth base; As a further preferred embodiment of the present invention, the piezoelectric ceramic comprises eight pieces, and the width of the piezoelectric ceramic is the same as the width of the stator tooth base; Eight piezoelectric ceramics are arranged closely in sequence along the long side of the stator tooth base, wherein the length of the piezoelectric ceramics located at the two ends along the long side of the stator tooth base is one-third of the length of the other piezoelectric ceramics; As a further preferred embodiment of the present invention, when a sawtooth excitation voltage is applied to the piezoelectric ceramic, the polarization direction is perpendicular to the bottom surface of the stator tooth base, and the polarization directions of adjacent piezoelectric ceramics are opposite, so that the stator teeth generate asymmetric vibration. As a further preferred embodiment of the present invention, the moving element has an I-shaped structure, and friction material is arranged on its bottom surface opposite to the stator; As a further preferred embodiment of the present invention, the metal substrate of the stator is made of phosphor bronze, the piezoelectric ceramic is made of PZT-8 material, and the friction material is made of polytetrafluoroethylene.

[0011] By employing the above technical solutions, the present invention has the following beneficial effects compared to the prior art: 1. The planar resonant inertial linear ultrasonic motor provided by the present invention excites the stator to resonate by applying a suitable sawtooth voltage to the piezoelectric ceramic, causing the stator teeth to vibrate asymmetrically. The movement of the mover is controlled by the inertial principle. Since a single layer of piezoelectric ceramic is used, its capacitive load characteristics are not obvious, which can make the vibration response of the stator drive end reach a more ideal state. 2. The planar resonant inertial linear ultrasonic motor provided by the present invention causes the stator to resonate by applying a voltage of a specific frequency to the piezoelectric ceramic, thereby amplifying the amplitude of the stator drive end, making the stator structure simpler and greatly reducing the requirements for motor manufacturing. 3. The flat resonant inertial linear ultrasonic motor provided by the present invention adopts a metal substrate (flat plate structure) with a rectangular disk structure as the stator. It is only necessary to place the mover on the stator teeth and apply a unidirectional preload to solve the problem of complicated preload application and adjustment in traditional inertial ultrasonic motors. 4. The flat resonant inertial linear ultrasonic motor provided by the present invention connects the stator tooth base and the fixed web plate through a flexible web plate. The stator does not need to be fixed by a complex clamping device and will not have any impact on the stator vibration. Attached Figure Description

[0012] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0013] Figure 1 This is a schematic diagram of the overall structure of a preferred embodiment provided by the present invention; Figure 2 This is a schematic diagram of the stator assembly in a preferred embodiment of the present invention; Figure 3 This is a schematic diagram of the working mode shape of the stator assembly in a preferred embodiment of the present invention; Figure 4 This is a schematic diagram of the preferred embodiment of the piezoelectric ceramic polarization distribution and the corresponding sawtooth wave voltage excitation provided by the present invention; Figure 5 This is a schematic diagram of the sawtooth excitation voltage signal applied to the piezoelectric ceramic in a preferred embodiment of the present invention; Figure 6 This is a schematic diagram illustrating the working principle of a preferred embodiment of the present invention; Figure 7 This is a displacement-time curve of an ultrasonic motor in a preferred embodiment of the present invention.

[0014] In the diagram: 1 is the stator, 2 is the mover, 3 is the friction material, 4 is the piezoelectric ceramic, 5 is the stator tooth, 6 is the stator tooth base, 7 is the flexible web, and 8 is the fixed web. Implementation

[0015] The present invention will now be described in further detail with reference to the accompanying drawings. In the description of this application, it should be understood that the terms "left side," "right side," "upper part," "lower part," etc., indicate the orientation or positional relationship based on the orientation or positional relationship 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 orientation, or be constructed and operated in a specific orientation. "First," "second," etc., do not indicate the importance of the components, and therefore should not be construed as a limitation of the present invention. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of the present invention.

[0016] As described in the background section, traditional inertial motors require stacking piezoelectric ceramics 4 and setting up special displacement amplification structures to increase the amplitude of the stator drive end. However, this construction still cannot guarantee the amplitude and improve the operating frequency. Therefore, this application provides a planar resonant inertial linear ultrasonic motor, which solves the above problems by constructing a simple and special stator structure.

[0017] like Figure 1 The image shown is of a planar resonant inertial linear ultrasonic motor provided in this application, including a stator assembly and a mover assembly, with the mover assembly positioned on the surface of the stator assembly. The most significant highlight of this application is the unique structural design of the stator assembly. Figure 2As shown, the stator assembly includes a stator 1 and a piezoelectric ceramic (made of PZT-8 material). The stator is a rectangular disk-shaped metal substrate (made of phosphor bronze). The metal substrate includes stator teeth 5, stator tooth base 6, flexible web 7, and fixed web 8. The stator tooth base includes two long sides, each of which is connected to the fixed web through the flexible web. Here, the cross-sectional thickness of the stator tooth base and the fixed web is different. After the stator tooth base and the fixed web are connected by the flexible web, there is a difference in cross-sectional thickness. The design of the difference in cross-sectional thickness enables the stator assembly to play a vibration isolation role through the principle of abrupt change in cross-sectional area.

[0018] Multiple through holes are made in the fixed web (corresponding to the preferred embodiment). Figure 2 The stator has eight through holes, which provide a fixed constraint. The mover assembly includes a mover 2 and friction material 3 (made of polytetrafluoroethylene). The mover is designed as a flexible structure, generally in the shape of an I-beam. The friction material is fixed to the bottom of the mover using adhesive bonding. This design makes the contact between the stator and the mover more uniform and reduces the impact of uneven preload on the contact between the mover and the stator. Several piezoelectric ceramics are fixed to the bottom surface of the stator tooth base by adhesive bonding. The piezoelectric ceramics are rectangular piezoelectric ceramic sheets based on the d31 effect. In the preferred embodiment, a single layer of piezoelectric ceramics is used, which has less capacitive load characteristics and can achieve a more ideal vibration response at the stator drive end. By applying a voltage of a specific frequency to the piezoelectric ceramics, the stator tooth base resonates, and the vibration displacement is amplified through the resonance principle. The simple stator structure can achieve the relevant objectives, greatly reducing the requirements for motor manufacturing.

[0019] In a preferred embodiment, the stator's operating mode is the B70 bending vibration mode. The piezoelectric ceramic is excited to cause the stator tooth base to generate longitudinal bending vibration. In order to convert the displacement in the Z direction of the bending vibration into the displacement in the Y direction, stator teeth are arranged at the node position where the bending vibration occurs on the surface of the stator tooth base, that is, the three stator teeth are set at the connection of adjacent waves of the bending vibration mode. Figure 3 As shown, the three stator teeth are defined as tooth number one, tooth number two, and tooth number three. Tooth number two is located at the center of the stator tooth base, and tooth number one and tooth number three are located at specific positions on both sides of tooth number two.

[0020] When the mover assembly is mounted on the surface of the stator assembly, friction material is pressed against the surface of the stator teeth, applying preload to the mover. The stator drives the mover to slide through friction, and the movement of the mover generates displacement using the principle of inertia. It is worth noting that the flexible web connecting the aforementioned stator tooth base and the fixed web has a sudden change in cross-sectional area, which prevents the fixed web from vibrating during stator operation. This ensures that the fixation of the stator does not affect the stator's operating modes, and eliminates the need for complex clamping devices to secure the stator.

[0021] Figure 3 The diagram shown is a schematic diagram of the working mode vibration structure of the preferred embodiment provided in this application. The working mode is a 7th order bending vibration with a frequency of 30745Hz. Figure 4 The diagram shows the preferred embodiment of the piezoelectric ceramic polarization distribution and electrical excitation scheme provided in this application. Eight piezoelectric ceramics based on the d31 effect are arranged in a row and bonded to the bottom of the stator. The eight piezoelectric ceramics are arranged sequentially and closely along the long side of the stator tooth base. The length of the piezoelectric ceramics located at the two ends along the long side of the stator tooth base is one-third of the length of the other piezoelectric ceramics. The polarization directions are all perpendicular to the bonding surface, and the polarization directions of adjacent piezoelectric ceramics are opposite. The upper surface of the piezoelectric ceramics is grounded, and a voltage is applied to the lower surface, causing the stator teeth to vibrate asymmetrically, thereby exciting the stator to produce bending vibration. A voltage is applied to the piezoelectric ceramics... Figure 5 The excitation electrical signal shown is used to excite asymmetric vibration at the stator tooth contact end using inertial drive. A sawtooth wave voltage is applied to all piezoelectric ceramics, exciting the stator's seventh-order bending vibration. This forces a difference in the forward and return motions of the stator tooth contact end, causing the stator tooth drive end to produce a "fast forward, slow return" reciprocating motion. The difference between sliding friction and static friction is used to drive the slider motion. If the direction of the mover's motion needs to be changed, only the voltage's polarity needs to be reversed.

[0022] The following implementation will proceed according to the aforementioned constraints, such as... Figure 6 As shown, in 6a, without applied voltage (point a), the mover presses against the stator teeth by preload; in 6b, when the voltage changes from a to b, the stator teeth and the mover move forward simultaneously and remain relatively stationary; in 6c, when the voltage drops rapidly from b to c, the stator teeth move rapidly in the opposite direction, and the mover moves accordingly. However, because the acceleration of the mover caused by friction is less than the acceleration of the stator teeth, relative sliding occurs between them; in 6d, when the voltage changes from c to d, the stator teeth and the mover move forward slowly again.

[0023] Finally, as Figure 7 As shown, the working performance of the ultrasonic motor was simulated using the commercial finite element software ADINA to obtain the working displacement-time diagram. It can be clearly seen from the figure that the maximum operating speed of the ultrasonic motor is 68 mm / s under a preload of 114 N and a sawtooth wave voltage of 400 V and 32000 Hz, which indicates that the motor has a large output force.

[0024] In summary, the planar resonant inertial linear ultrasonic motor provided in this application has low manufacturing cost, few parts, simple processing technology, high precision and short response time. The motor speed can be adjusted by controlling only a single drive source. It can be applied to occasions with limited longitudinal dimensions and has wide applications in precision instruments.

[0025] Those skilled in the art will understand 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 application 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.

[0026] The meaning of "and / or" as used in this application includes situations where each exists alone or both exist simultaneously.

[0027] The term "connection" as used in this application can mean a direct connection between components or an indirect connection between components through other components.

[0028] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A planar resonant inertial linear ultrasonic motor, comprising a stator assembly and a mover assembly disposed on its surface, characterized in that: The stator assembly includes a stator (1) and a piezoelectric ceramic (4). The stator (1) is a metal substrate with a rectangular disk structure. The metal substrate includes stator teeth (5), stator tooth base (6), flexible web (7), and fixed web (8). The stator tooth base (6) includes two long sides, and each long side is connected to the fixed web (8) through the flexible web (7). The cross-sectional thickness of the stator tooth base (6) and the fixed web (8) is different. After the stator tooth base (6) and the fixed web (8) are connected through the flexible web (7), there is a difference in cross-sectional thickness. The piezoelectric ceramic (4) is a rectangular piezoelectric ceramic sheet based on the d31 effect. Several piezoelectric ceramics (4) are pasted on the bottom surface of the stator tooth base (6). The piezoelectric ceramics (4) are excited to cause the stator tooth base (6) to generate longitudinal bending vibration. Stator teeth (5) are arranged at the node position where bending vibration occurs on the surface of the stator tooth base (6). The stator teeth (5) are arranged perpendicular to the long side of the stator tooth base (6), which can convert the longitudinal bending vibration into the lateral displacement of the driving end of the stator teeth (5). The moving part assembly includes a moving part (2) and a friction material (3). When the moving part assembly is placed on the surface of the stator assembly, the friction material (3) is pressed on the surface of the stator teeth (5) to apply a preload to the moving part (2). The stator (1) drives the moving part (2) to slide through friction, and the moving part (2) is displaced by the principle of inertia.

2. The planar resonant inertial linear ultrasonic motor according to claim 1, characterized in that: The stator teeth (5) include three, one of which is located in the middle of the stator tooth base (6).

3. The planar resonant inertial linear ultrasonic motor according to claim 1, characterized in that: The piezoelectric ceramic (4) comprises eight pieces, and the width of the piezoelectric ceramic (4) is the same as the width of the stator tooth base (6); Eight piezoelectric ceramics (4) are arranged closely in sequence along the long side of the stator tooth base (6), wherein the length of the piezoelectric ceramics (4) located at the two ends along the long side of the stator tooth base (6) is one-third of the length of the other piezoelectric ceramics (4).

4. The planar resonant inertial linear ultrasonic motor according to claim 3, characterized in that: When a sawtooth excitation voltage is applied to the piezoelectric ceramic (4), the polarization direction is perpendicular to the bottom surface of the stator tooth base (6), and the polarization directions of adjacent piezoelectric ceramics (4) are opposite, causing the stator tooth (5) to produce asymmetric vibration.

5. The planar resonant inertial linear ultrasonic motor according to claim 1, characterized in that: The moving part (2) has an I-shaped structure, and friction material (3) is laid on its bottom surface opposite to the stator (1).

6. The planar resonant inertial linear ultrasonic motor according to claim 1, characterized in that: The metal substrate of the stator (1) is made of phosphor bronze, the piezoelectric ceramic (4) is made of PZT-8 material, and the friction material (3) is made of polytetrafluoroethylene.

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