Piezoelectric rotary- and resonance drive
Patent Information
- Application Number
- EP2023744119
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-08-01
- Filing Date
- 2023-07-14
- Publication Date
- 2025-06-11
AI Technical Summary
Existing piezoelectric running and resonance drives are complex, costly, and require high control voltages due to the use of shear or bending actuators with thick ceramic layers, limiting their production efficiency and operational simplicity.
The implementation of linear piezoelectric actuators, which are inexpensive, easy to manufacture, and operate with low control voltages, coupled with a friction element to achieve movement and contact with the rotor, allowing for optimal adjustment of contact pressure and driving force through independent or superimposed control of the actuators.
This solution enables the production of piezoelectric running and resonance drives at lower costs with simplified control systems, achieving efficient and compact designs capable of generating static friction and driving forces with reduced operational complexity.
Smart Images
Figure 1.1
Abstract
Description
[0001] Piezoelectric running and resonance drive
[0002] The present invention relates to a piezoelectric running and resonance drive according to the preamble of claim 1 and to a method for controlling a piezoelectric running and resonance drive.
[0003] Piezoelectric rotor and resonant drives essentially comprise a rotor and one or more drive units. A drive unit includes an arrangement of piezoelectric actuators and a friction element configured for contact with the rotor. The arrangement of the actuators, when suitably controlled, generally causes the friction element to move toward or away from the rotor to establish or release contact with the rotor, and the friction element to move along the rotor to drive it. Such drives are disclosed, for example, in DE 197 15226 A1 and US 2010 / 0148629 A1.
[0004] The drives known from DE 197 15 226 A1 and US 2010 / 0148629 A1 utilize shear actuators or bending actuators. Such actuators have the disadvantage of being complex and expensive to manufacture. Multilayer shear actuators also have the disadvantage of their comparatively thick ceramic layers, which increases the overall height of the actuator. At the same time, such actuators can only be operated with high drive voltages.
[0005] In view of the disadvantages of the known drives outlined above, it is the object of the present invention to provide a piezoelectric running and resonance drive which can be manufactured at low cost and with little effort and requires only low drive voltages.
[0006] This object is achieved by a piezoelectric travel and resonance drive according to claim 1. According to the invention, each of the piezoelectric actuators in the arrangement is a linear actuator. Linear actuators are generally inexpensive and easy to manufacture. Furthermore, they can be operated with comparatively low drive voltages, which simplifies the design of the entire control system.
[0007] Advantageous further training is the subject of the subclaims.
[0008] It can be advantageous if the arrangement of the piezoelectric actuators and the friction element are coupled in such a way that, when the piezoelectric actuators are controlled, the friction element can execute the contact movement and the drive movement independently of each other or superimposed. Depending on the control of the linear actuators, different movement paths of the friction element can be realized.
[0009] It can be useful if the drive movement occurs in a plane or along an axis perpendicular to the axis of the contact movement. This allows the contact pressure of the friction element generated by the contact movement and required to drive the slider to generate static friction between the friction element and the underside of the slider to be optimally adjusted and matched to the drive force.
[0010] It may prove practical if the drive unit comprises a base supporting the array of piezoelectric actuators, with the contact movement preferably occurring perpendicular to the base and / or the drive movement occurring parallel to the base. By mounting the actuators on a base, a self-contained drive unit can be provided and the mounting of the drive unit into a higher-level structure, such as a frame, can be facilitated.
[0011] It can be advantageous if the piezoelectric actuators of the array are deflected in parallel directions when controlled, preferably parallel to the axis of contact movement. This ensures that all linear actuators in the array are oriented in the same direction, which simplifies the assembly and makes the array itself compact.
[0012] It can be beneficial if each of the piezoelectric actuators is a multilayer stack actuator designed to generate a deflection along its stack axis, which is preferably oriented parallel to the axis of contact movement. Multilayer stack actuators can be manufactured easily, inexpensively, and quickly by sintering green foils.
[0013] It may be advantageous if the piezoelectric actuators are assigned to separately controllable actuator units, whereby the friction element executes the contact movement with at least one of the piezoelectric actuators when a first actuator unit is controlled, and executes the drive movement with at least one, preferably two, other piezoelectric actuators when a second actuator unit is controlled. The movement components of the friction element are assigned to individual drive units, which simplifies the design of the control system.
[0014] It can be practical if the piezoelectric actuators are provided in several, preferably two, levels within the arrangement, with all piezoelectric actuators of the same actuator unit preferably being arranged in the same level. By providing the actuators in several levels, a compact arrangement of the actuators can be realized, in which the actuators of the different levels can interact through coupling.
[0015] It can prove useful to place a support between two planes and couple the piezoelectric actuators of the different planes via the support. Using the support, the deformation motion of the actuators in one plane can be transferred to the other plane, allowing the deformation motions of the actuators of different planes to be combined.
[0016] It may be advantageous if the friction element is connected to two piezoelectric actuators arranged side by side within the assembly, preferably via a base that supports the friction element. The interaction of the two actuators can enable a movement of the friction element suitable for driving the rotor, in particular a tilting movement.
[0017] It may be useful if the drive unit is mounted in a frame, preferably via a support that penetrates the array of piezoelectric actuators and / or a spring element that preloads the array of piezoelectric actuators against the frame and particularly preferably has a recess through which the friction element protrudes. Using the support and the spring element, the drive unit can be easily mounted in the frame.
[0018] It may prove advantageous if the arrangement of piezoelectric actuators comprises three piezoelectric actuators, with one piezoelectric actuator arranged in a first plane and two piezoelectric actuators arranged in a second plane above the first plane, with the two piezoelectric actuators of the second plane arranged side by side. This arrangement is extremely compact and functional with regard to generating the contact movement and the drive movement of the friction element.
[0019] It can be advantageous if at least two drive units are arranged side by side in a direction parallel to the direction of the drive movement, or if at least three drive units are arranged along a circular path. These configurations can provide a linear drive with an extended travel range of the slider or increased drive force, or a rotary drive. It can be advantageous if the drive has a control unit for controlling the piezoelectric actuators with electrical control voltages. Using a control unit, controlling the linear actuators with electrical control voltages can be easily implemented.
[0020] A further aspect of the present invention relates to a method for controlling a piezoelectric running and resonance drive, which comprises: a rotor, and at least one drive unit which comprises an arrangement of several piezoelectric linear actuators and a friction element which is configured to come into contact with the rotor, wherein at least one piezoelectric linear actuator of the arrangement is controlled such that the friction element executes a contact movement towards or away from the rotor in order to establish or release contact with the rotor, and at least one other piezoelectric linear actuator, preferably two other piezoelectric linear actuators, of the arrangement is / are controlled such that the friction element executes a drive movement along the rotor.
[0021] It can be advantageous if the two piezoelectric linear actuators that drive the friction element's movement are controlled in such a way that they behave in antiphase. This makes it particularly easy to implement the friction element's drive movement.
[0022] Terms and definitions
[0023] Linear actuator
[0024] The term "linear actuator" describes an actuator designed to perform a deformation usable for driving, i.e., expansion or contraction, exclusively along one effective direction. The expansion or contraction of the actuator may be accompanied by a constriction or thickening of the actuator in a plane perpendicular to the effective direction, which, however, remains unused and is not relevant for the drive.
[0025] Short description of the characters
[0026] Fig. 1a shows an embodiment of a drive according to the invention in a perspective view. Fig. 1b shows the embodiment of Fig. 1a in an exploded view.
[0027] Figs. 2a and 2b show the deformation behavior of piezoelectric linear actuators in a drive unit of the drive according to the invention using a FEM simulation in two different states. Fig. 3 shows an embodiment of a drive group with multiple drive units for a linear drive.
[0028] Fig. 4 shows a further embodiment of a drive group with several drive units for a rotary drive.
[0029] Detailed description of the preferred embodiment
[0030] Figs. 1a and 1b show the structure of the drive according to the invention in a preferred embodiment. Essentially, the drive comprises at least one drive unit 1 and a rotor 11. Rotor 11 is only partially shown in the present figures as a flat, rod-shaped element, but can fundamentally have various shapes. In particular, rotor 11 can also be designed as a ring, table, or platform.
[0031] The drive unit 1 comprises a first piezoelectric linear actuator 2, which is arranged on a plate-shaped base 5. Two second piezoelectric linear actuators 3.1, 3.2 are coupled to the piezoelectric linear actuator 2 via a carrier 6. The linear actuators 2, 3.1 and 3.2 are each cuboid-shaped. The two second linear actuators 3.1 and 3.2 are arranged next to one another on the carrier 6. The carrier 6 is located between the upper end face of the first linear actuator 2 and the lower end faces of the two second linear actuators 3.1, 3.2. The carrier 6 therefore divides the arrangement of the linear actuators into two levels, with the first linear actuator 2 positioned in a first level and the two second linear actuators 3.1 and 3.2 in a second level above the first level. Furthermore, the first linear actuator 2 is more than twice as wide as one of the second linear actuators 3.1, 3.2, so that the two second linear actuators 3.1, 3.2 can be arranged within the width of the first linear actuator 2. Instead of a wide first linear actuator 2, two or more first linear actuators can also be used, each of which is smaller in width. In the present embodiment, all linear actuators 2, 3.1 and 3.2 have the same height and depth, but other dimensions are conceivable. Preferably, each of the linear actuators 2, 3.1 and 3.2 is designed as a stacked or multi-layer actuator constructed from an alternating arrangement of ceramic layers and internal electrodes. Each of the linear actuators 2, 3.1 and 3.2 has a surface electrode on one of its side surfaces for electrically contacting the internal electrodes.
[0032] The drive unit 1 further comprises a friction element 4, which is provided on a plate-shaped base. The friction element is connected to the upper end faces of the two second linear actuators 3.1, 3.2 via the plate-shaped base. The friction element 4 is hemispherical or dome-shaped and is intended for contact with a flat underside of the rotor 11.
[0033] In addition, the drive unit 1 comprises a spring element 7, with which a preload of the linear actuators 2, 3.1, 3.2 can be achieved. The spring element 7 is designed as a metal strip, which has a mounting section at each of its two ends for attachment to a frame structure receiving the drive unit 1. Each mounting section preferably has a bore. A central section of the spring element 7 is offset parallel to the mounting sections and has a bore through which the friction element can protrude. In the assembled state, the central section of the spring element 7 presses on the base of the friction element 4 and thus exerts a compressive force on the linear actuators 2, 3.1, 3.2, so that they are subject to preload. Similar to the spring element 7, the carrier 6 is also designed as a metal strip, which can be attached to the frame structure using mounting sections.In addition to metal, other materials are also conceivable for the carrier 6 and the spring element 7.
[0034] Using a control unit, the individual linear actuators 2, 3.1, and 3.2 can be controlled with suitable electrical voltages. The linear actuators 2, 3.1, and 3.2 are controlled in such a way that the friction element 4 can perform both a contact movement toward or away from the slider 11 to establish or release contact with the slider 11, as well as a drive movement along the slider 11 to drive it.
[0035] The contact movement of the friction element 4 can be generated in particular by controlling the first linear actuator 2. When controlled with an electrical voltage, the first linear actuator 2 performs an expansion or contraction in a direction perpendicular to the base 5. This movement is initially transmitted to the friction element 4 via the carrier 6 and finally via the two second linear actuators 3.1, 3.2. Consequently, the contact movement of the friction element 4 is a movement of the friction element in a direction perpendicular to the base 5. A regular oscillation of the friction element 4 in the direction perpendicular to the base 5 is achieved, for example, by applying a sinusoidal alternating voltage to the first linear actuator 2.
[0036] The drive movement of the friction element 4 can be generated by suitable control of the two second linear actuators 3.1, 3.2. Each of the two second linear actuators 3.1, 3.2 is also designed to carry out an expansion or contraction in a direction perpendicular to the base 5 when controlled with an electrical voltage. However, the two second linear actuators 3.1, 3.1 are controlled in such a way that they behave in opposite directions or oscillate in antiphase. This behavior is illustrated in Fig. 2a and 2b. In the state shown in Fig. 2a, the first of the second linear actuators 3.1 is expanded and the second of the second linear actuators 3.2 is contracted. The friction element 4, which is connected to both second linear actuators 3.1, 3.2 via a base, experiences a tilting movement in the direction of the contracted second linear actuator 3.2 in this state. In an opposite state, which is shown in Fig.2b, the first of the second linear actuators 3.1 is contracted and the second of the second linear actuators 3.2 is expanded. In this state, the friction element 4 experiences a tilting movement in the direction of the contracted first linear actuator 3.1. The tilting movements of the friction element 4 consequently enable a drive movement or a return movement in a direction parallel to the base 5. A regular oscillation of the friction element 4 in the direction parallel to the base 5 is achieved, for example, by applying a sinusoidal alternating voltage to each of the two second linear actuators 3.1, 3.2, wherein these alternating voltages are 180° out of phase with one another. In this case, the polarization directions of the two second linear actuators 3.1, 3.2 are the same. In a case in which the polarization directions of the two second linear actuators 3.1. 3.2 are opposite to each other, the two second linear actuators 3.1, 3.2 can be controlled with the same sinusoidal alternating voltage without phase shift.
[0037] According to the configuration of the drive according to the invention, the contact movement and the drive movement of the friction element 4 can be carried out independently of one another or superimposed. This means that by controlling the first linear actuator 2 alone, the friction element 4 can initially carry out the contact movement in the direction of the slider 11 until it comes into contact with the underside of the slider 11 and exerts a certain contact pressure on the slider 11. Subsequently, the two second linear actuators 3.1, 3.2 can be controlled such that the friction element 4, as described above, executes a tilting movement in a direction parallel to the underside of the slider 11. The friction element 4 pressed against the slider 11 thereby propel the slider 11 in this direction. By appropriately controlling the first linear actuator 2, the contact between the friction element 4 and the underside of the slider 11 can be released again.Finally, the two second linear actuators 3.1, 3.2 can be controlled such that the friction element 4 executes a tilting movement in the opposite direction and consequently a return movement. Repeated sequences of these control steps enable continuous propulsion of the slider 11.
[0038] On the other hand, it is also possible to control the linear actuators 2, 3.1, and 3.2 in such a way that the contact movement and the drive movement of the friction element 4 overlap. As a result, an elliptical oscillation path of the friction element 4 can be generated, the main axis of which is inclined relative to the underside of the slider 11. If the friction element 4 oscillates along this path, continuous propulsion of the slider is also achieved.
[0039] Fig. 3 shows a drive group 10a in which two drive units 1 are arranged next to one another and fixed in a common frame 8a, 9a. In particular, each drive unit 1 is arranged on a base element 8a and fastened to structural elements 9a via the support 6 and the spring element 7 with the aid of screws. The drive units 1 are arranged along the feed direction of a slider and thus extend the travel of the slider or, in the case of a correspondingly long slider, make it possible to double the drive force acting on the slider. The use of two drive units arranged next to one another is merely an example. Of course, three or more drive units can also be arranged next to one another in a corresponding frame. The frame 8a, 9a can also consist of several elements or even be formed in one piece, as long as it provides suitable receiving sections for the drive units 1.
[0040] Fig. 4 shows a drive group 10b in which three drive units 1 are arranged along a circular path and fastened in a common frame 8b, 9b. The fastening of the drive units to the base element 8b and the structural elements 9b of the frame essentially corresponds to the fastening described in connection with Fig. 3. Because the drive units 1 are arranged on a circular path, a rotary drive can be realized using an annular rotor. Just as in the embodiment according to Fig. 3, the frame 8b, 9b of the present embodiment can also consist of several elements or be formed in one piece.
[0041] List of reference symbols
[0042] 1 drive unit
[0043] 2 piezoelectric linear actuators
[0044] 3.1 , 3.2 piezoelectric linear actuator
[0045] 4 Friction element
[0046] 5 Base
[0047] 6 carriers
[0048] 7 Spring element
[0049] 8a, 8b Basic element of the frame
[0050] 9a, 9b Structural element of the frame
[0051] 10a, 10b drive group
[0052] 11 runners
Claims
CLAIMS 1. Piezoelectric running and resonance drive, comprising a rotor (11), and at least one drive unit (1) which comprises an arrangement of several piezoelectric actuators (2, 3.1, 3.2) and a friction element (4) which is designed to come into contact with the rotor (11), wherein the arrangement of the piezoelectric actuators (2, 3.1, 3.2) and the friction element (4) are coupled in such a way that the friction element (4), when the piezoelectric actuators (2, 3.1, 3.2) are controlled, can execute both a contact movement towards the rotor (11) or away from it to establish or release contact with the rotor (11) and a drive movement along the rotor (11) to drive it, characterized in that each of the piezoelectric actuators (2, 3.1, 3.2) of the arrangement is a linear actuator.
2. Piezoelectric running and resonance drive according to the preceding claim, characterized in that the arrangement of the piezoelectric actuators (2, 3.1, 3.2) and the friction element (4) are coupled in such a way that the friction element (4) can carry out the contact movement and the drive movement independently of one another or superimposed upon actuation of the piezoelectric actuators (2, 3.1, 3.2).
3. Piezoelectric running and resonance drive according to one of the preceding claims, characterized in that the drive movement takes place in a plane or along an axis perpendicular to an axis of the contact movement.
4. Piezoelectric running and resonance drive according to one of the preceding claims, characterized in that the drive unit (1) comprises a base (5) which carries the arrangement of the piezoelectric actuators (2, 3.1, 3.2), wherein the contact movement preferably takes place perpendicular to the base (5) and / or the drive movement takes place parallel to the base (5).
5. Piezoelectric running and resonance drive according to one of the preceding claims, characterized in that the piezoelectric actuators (2, 3.1, 3.2) of the arrangement are deflected in parallel directions when controlled, preferably parallel to the axis of the contact movement.
6. Piezoelectric running and resonance drive according to one of the preceding claims, characterized in that each of the piezoelectric actuators (2, 3.1, 3.2) is a multi-layer Stack actuator which is designed to generate a deflection along its stack axis, which is preferably oriented parallel to the axis of the contact movement.
7. Piezoelectric running and resonance drive according to one of the preceding claims, characterized in that the piezoelectric actuators (2, 3.1, 3.2) are assigned to separately controllable actuator units (2, 3), wherein the friction element (4) executes the contact movement when a first actuator unit (2) is controlled with at least one of the piezoelectric actuators (2) and executes the drive movement when a second actuator unit is controlled with at least one, preferably two, other of the piezoelectric actuators (3.1, 3.2).
8. Piezoelectric running and resonance drive according to one of the preceding claims, characterized in that the piezoelectric actuators (2, 3.1, 3.2) are provided within the arrangement in several, preferably two, planes, wherein preferably all piezoelectric actuators (2, 3.1, 3.2) of the same actuator unit (2, 3) are arranged in the same plane.
9. Piezoelectric running and resonance drive according to the preceding claim, characterized in that a carrier (6) is arranged between two levels and the piezoelectric actuators (2, 3.1, 3.2) of the different levels are coupled to one another via the carrier (6).
10. Piezoelectric running and resonance drive according to one of the preceding claims, characterized in that the friction element (4) is connected to two piezoelectric actuators (3.1, 3.2) arranged next to one another within the arrangement, preferably via a base which supports the friction element (4).
11. Piezoelectric running and resonance drive according to one of the preceding claims, characterized in that the drive unit (1) is fastened in a frame (8a, 8b, 9a, 9b), preferably via a carrier (6) which penetrates the arrangement of the piezoelectric actuators (2, 3.1, 3.2), and / or a spring element (7) which prestresses the arrangement of the piezoelectric actuators (2, 3.1, 3.2) against the frame (8a, 8b, 9a, 9b) and particularly preferably has a recess through which the friction element (4) projects.
12. Piezoelectric running and resonance drive according to one of the preceding claims, characterized in that the arrangement of the piezoelectric actuators (2, 3.1, 3.2) comprises three piezoelectric actuators, wherein a piezoelectric actuator (2) is arranged in a first plane. and two piezoelectric actuators (3.1, 3.2) are arranged in a second level located above the first level, wherein the two piezoelectric actuators (3.1, 3.2) of the second level are arranged next to one another.
13. Piezoelectric running and resonance drive according to one of the preceding claims, characterized in that at least two drive units (1) are arranged next to one another in a direction parallel to the direction of the drive movement or that at least three drive units (1) are arranged along a circular path.
14. Piezoelectric running and resonance drive according to one of the preceding claims, characterized in that the drive has a control unit for controlling the piezoelectric actuators (2, 3.1, 3.2) with electrical control voltages.
15. A method for controlling a piezoelectric running and resonance drive, comprising: a rotor (11), and at least one drive unit (1) comprising an arrangement of several piezoelectric linear actuators (2, 3.1, 3.2) and a friction element (4) which is designed to come into contact with the rotor, wherein at least one piezoelectric linear actuator (2) of the arrangement is controlled such that the friction element (4) executes a contact movement towards or away from the rotor in order to establish or release contact with the rotor, and at least one other piezoelectric linear actuator (3.1, 3.2), preferably two other piezoelectric linear actuators (3.1, 3.2), of the arrangement is / are controlled such that the friction element (4) executes a drive movement along the rotor (11).
16. Method according to the preceding claim, characterized in that the two piezoelectric linear actuators (3.1, 3.2) which cause the drive movement of the friction element (4) are controlled in such a way that they behave in antiphase.