Piezoelectric motion and resonance driver

Abstract

The invention relates to a piezoelectric motion and resonance drive and a method for actuating a piezoelectric motion and resonance drive. The invention relates to a drive comprising a moving member (11) and at least one drive unit (1) comprising an assembly of a plurality of piezo actuators (2, 3.1, 3.2) and a friction element (4) designed to be in contact with the moving member (11), the assembly of piezo actuators (2, 3.1, 3.2) and the friction element (4) being coupled in such a way that when the piezo actuators (2, 3.1, 3.2) are actuated, the assembly of piezo actuators (2, 3.1, 3.2) and the friction element (4) are in contact with the moving member (11). The friction element (4) is able to perform a contact movement towards or away from the moving member (11) to establish or terminate contact with the moving member (11), and is also able to perform a drive movement along the moving member (11) to drive the moving member. The aim of the invention is to achieve high cost effectiveness and simple production. In order to achieve this object, each piezoelectric actuator (2, 3.1, 3.2) of the assembly is a linear actuator.

Description

Technical Field

[0001] The invention relates to a piezoelectric motion and resonant drive according to the preamble of claim 1 and to a method for actuating a piezoelectric motion and resonant drive. Background Art

[0002] Piezoelectric motion and resonance drivers mainly include a moving member and one or more drive units. The drive unit includes a piezoelectric actuator and an arrangement of friction elements suitable for contacting the moving member. In principle, it is arranged that when the actuator is properly actuated, the components of the actuator move the friction element toward or away from the moving member to establish or terminate contact with the moving member and move the friction element along the moving member to drive it. For example, such a driver is disclosed in DE 197 15 226 A1 and US 2010 / 0148629 A1.

[0003] In the actuators known from DE 197 15 226 A1 and US 2010 / 0148629 A1, shearing actuators or bending actuators are used. These actuators have the disadvantage that they are complex to manufacture and can only be produced at high cost. In addition, multilayer shearing actuators have the disadvantage that their ceramic layers are relatively thick, which increases the overall installation height of the actuator. At the same time, these actuators can only be operated at high voltages. Summary of the invention

[0004] In view of the above-mentioned disadvantages of the known actuators, it is an object of the present invention to provide a piezoelectric motion and resonance actuator which can be manufactured at low cost and with little effort and which requires only a low actuation voltage.

[0005] This problem is solved by a piezoelectric motion and resonance drive according to claim 1. According to the invention, each piezoelectric actuator of the assembly is a linear actuator. Linear actuators are generally inexpensive and easy to manufacture. In addition, they can be operated with relatively low actuation voltages, which facilitates the construction of the overall control system.

[0006] Preferred further developments are the subject matter of the dependent claims.

[0007] It may be advantageous if the components of the piezoelectric actuator and the friction element are coupled in such a way that upon actuation of the piezoelectric actuator the friction element can perform contact and drive movements independently of one another or in an overlapping manner.Depending on the actuation of the linear actuator, various movement paths of the friction element can be achieved.

[0008] This can be useful if the drive movement is in a plane or along an axis perpendicular to the axis of the contact movement. This allows the contact pressure of the friction element (which is generated by the contact movement and is necessary to drive the moving member) to be optimally set to generate static friction between the friction element and the bottom surface of the moving member and to match the drive force.

[0009] It may be suitable that the drive unit comprises a base carrying the piezoelectric actuator assembly, wherein the contact movement preferably occurs perpendicular to the base and / or the drive movement occurs parallel to the base. Since the actuator is mounted on the base, a self-contained drive unit can be provided and the drive unit can be easily assembled in a superordinate structure, such as a frame.

[0010] Preferably, the piezoelectric actuators in the assembly deflect in parallel directions upon actuation, preferably parallel to the axis of contact movement. Thus, all linear actuators in the assembly are oriented in the same way, which simplifies the construction of the assembly and makes the assembly itself compact.

[0011] It may be useful if each piezoelectric actuator is a multi-layer stack actuator which is configured to produce a deflection along its stack axis which is preferably oriented parallel to the axis of the contact movement.Multi-layer stack actuators can be produced easily, cheaply and quickly by sintering green films.

[0012] Preferably, the piezoelectric actuators are assigned to individually actuatable actuator units, wherein the friction element performs a contact movement when a first actuator unit is actuated with at least one piezoelectric actuator, and the friction element performs a drive movement when a second actuator unit is actuated with at least one, preferably two, further piezoelectric actuators. The movement parts of the friction element are assigned to the individual drive units, which simplifies the construction of the control system.

[0013] It is possible if the piezoelectric actuators within the assembly are arranged in a plurality of, preferably two, planes, wherein preferably all piezoelectric actuators of the same actuator unit are arranged in the same plane. By arranging the actuators in a plurality of planes, a compact arrangement of the actuators can be achieved, wherein actuators of different planes can interact with each other via couplings.

[0014] It may be useful if a carrier is arranged between two planes and piezoelectric actuators of different planes are coupled to each other via the carrier. By means of the carrier, the deformation movement of the actuator in one plane can be transferred to the other plane, so that the deformation movement of the actuators of different planes can be combined.

[0015] It may be advantageous if the friction element is connected to two piezoelectric actuators arranged adjacent to each other within the assembly, preferably via a base carrying the friction element. The interaction of the two actuators may cause a movement, in particular a tilting movement, of the friction element adapted to drive a moving member.

[0016] It may be useful if the drive unit is mounted in the frame, preferably via a bracket passing through the piezoelectric actuator assembly and / or a spring element biasing the piezoelectric actuator assembly against the frame, and particularly preferably with a groove through which the friction element protrudes. With the help of the bracket and the spring element, the drive unit can be easily mounted in the frame.

[0017] It may be advantageous if the assembly of piezoelectric actuators comprises three piezoelectric actuators, one of which is arranged in a first plane and two of which are arranged in a second plane located above the first plane, wherein the two piezoelectric actuators of the second plane are arranged adjacent to each other. The assembly is very compact and practical in terms of generating the contact movement and the drive movement of the friction element.

[0018] It may be useful if at least two drive units are arranged adjacent to each other 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 be used to provide a linear drive with an extended stroke or increased drive force of the moving member, or a rotary drive.

[0019] It may be advantageous if the drive has a control unit for controlling the piezoelectric actuator with an electrical control voltage. With the help of the control unit, the linear actuator can be easily actuated with the electrical control voltage.

[0020] Another embodiment of the present invention relates to a method for actuating a piezoelectric motion and resonance drive, comprising: a moving member, and at least one drive unit, which includes an assembly of multiple piezoelectric linear actuators and a friction element suitable for contacting the moving member, wherein at least one piezoelectric linear actuator of the assembly is actuated in such a way that the friction element performs a contact movement toward or away from the moving member so as to establish or terminate contact with the moving member, and at least one other piezoelectric linear actuator of the assembly, preferably two other piezoelectric linear actuators, is actuated in such a way that the friction element performs a driving movement along the moving member.

[0021] It may be preferred to actuate the two piezoelectric linear actuators providing the drive movement of the friction element such that they are in anti-phase. This makes the drive movement of the friction element particularly easy to achieve.

[0022] Terms and Definitions

[0023] Linear Actuators

[0024] The term "linear actuator" describes an actuator that is suitable for performing deformations that can be used for actuation (i.e., extension or contraction only in an effective direction). Extension or contraction of the actuator may be accompanied by compression or thickening of the actuator in a plane perpendicular to the effective direction, but this remains unused and has nothing to do with actuation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1a An exemplary embodiment of a drive according to the invention is shown in a perspective view. Figure 1b The exploded view shows Figure 1a Embodiment of the invention.

[0026] Figure 2a and 2b The deformation behavior of a piezoelectric linear actuator in a drive unit of a drive according to the invention is shown based on a finite element method (FEM) simulation in two different states.

[0027] Figure 3 An exemplary embodiment of a drive group having a plurality of drive units for a linear drive is shown.

[0028] Figure 4 A further embodiment of a drive assembly for a rotary drive having a plurality of drive units is shown. DETAILED DESCRIPTION

[0029] Figure 1a and 1b The structure of the drive according to the invention in a preferred embodiment is shown. Basically, the drive comprises at least one drive unit 1 and a mobile member 11. In this figure, the mobile member 11 is only shown in cross-section as a flat rod-shaped element, but in principle it can have different shapes. Specifically, the mobile member 11 can also be configured as a ring or a workbench or a platform.

[0030] The drive unit 1 includes a first piezoelectric linear actuator 2, which is arranged on a plate-like base 5. Two second piezoelectric linear actuators 3.1, 3.2 are connected to the piezoelectric linear actuator 2 via a bracket 6. The linear actuators 2, 3.1 and 3.2 are all in the shape of a rectangular parallelepiped. The two second linear actuators 3.1 and 3.2 are arranged adjacent to each other on the bracket 6. The bracket 6 is located between the upper end surface of the first linear actuator 2 and the lower end surfaces of the two second linear actuators 3.1, 3.2. Through the bracket 6, the assembly of the linear actuators is thus divided into two planes, wherein the first linear actuator 2 is positioned in the first plane and the two second linear actuators 3.1 and 3.2 are positioned in the second plane above the first plane. In addition, the width of the first linear actuator 2 is greater than twice that of 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, more than two first linear actuators may also be used, each having a smaller width. In the present embodiment, all linear actuators 2, 3.1 and 3.2 have the same height and depth, but other dimensions may also be considered. Preferably, each of the linear actuators 2, 3.1 and 3.2 is constructed as a stacked or multilayer actuator consisting of 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 electrical contact connection of the internal electrode.

[0031] In addition, the drive unit 1 includes a friction element 4, which is arranged on a plate-like base. The friction element is connected to the upper end faces of the two second linear actuators 3.1, 3.2 via the plate-like base. The friction element 4 is hemispherical or dome-shaped and is arranged to establish contact with the flat bottom surface of the moving member 11.

[0032] Furthermore, the drive unit 1 comprises a spring element 7, by means of which a biasing force can be applied to the linear actuators 2, 3.1 and 3.2. The spring element 7 is constructed as a metal strip, which comprises at each of its two ends a mounting portion for attachment to a frame structure receiving the drive unit 1. Each mounting portion preferably has a hole. The central portion of the spring element 7 is offset parallel to the mounting portion and has a hole through which the friction element can protrude. In the installed state, the central portion of the spring element 7 presses on the base of the friction element 4, thereby applying pressure on the linear actuators 2, 3.1 and 3.2, biasing them. Similar to the spring element 7, the bracket 6 is also constructed as a metal strip that can be attached to the frame structure using a mounting portion. In addition to metal, other materials can also be considered for the bracket 6 and the spring element 7.

[0033] By means of the control unit, each linear actuator 2, 3.1 and 3.2 can be actuated with a suitable voltage. In this case, the linear actuators 2, 3.1 and 3.2 are actuated in such a way that the friction element 4 can perform a contact movement toward or away from the mobile member 11 to establish or terminate the contact with the mobile member 11, and can also perform a driving movement along the mobile member 11 to drive it.

[0034] The contact movement of the friction element 4 can be generated in particular by actuating the first linear actuator 2. When actuated with an electric voltage, the first linear actuator 2 extends or contracts in a direction perpendicular to the base 5. This movement is first transmitted to the bracket 6 and finally to the two second linear actuators 3.1, 3.2 on the friction element 4. The contact movement of the friction element 4 is therefore a movement of the friction element in a direction perpendicular to the base 5. For example, by applying a sinusoidal alternating voltage to the first linear actuator 2, a regular vibration of the friction element 4 in a direction perpendicular to the base 5 is achieved.

[0035] The driven movement of the friction element 4 can be generated by appropriate actuation of the two second linear actuators 3.1, 3.2. Each of the two second linear actuators 3.1, 3.2 is also adapted to extend or contract in a direction perpendicular to the base 5 when actuated by an electric voltage. However, the two second linear actuators 3.1, 3.1 are actuated in such a way that they act in opposite ways or oscillate in anti-phase. This behavior is Figure 2a and 2b As shown in the figure. Figure 2a In the state shown, the first second linear actuator 3.1 is extended, while the second second linear actuator 3.2 is retracted. In this state, the friction element 4 connected to the two second linear actuators 3.1, 3.2 via the base performs a tilting movement in the direction of the retracted second linear actuator 3.2. In the opposite state, as Figure 2b As shown, the first second linear actuator 3.1 is contracted, while the second second linear actuator 3.2 is extended. In this state, the friction element 4 performs a tilting movement in the direction of the contracted first linear actuator 3.1. Therefore, the tilting movement of the friction element 4 can perform a driving movement or a reset movement in a direction parallel to the base 5. The regular oscillation of the friction element 4 in a 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 and 3.2, wherein these alternating voltages are phase-shifted by 180° relative to each other. In this case, the polarization directions of the two second linear actuators 3.1 and 3.2 are the same. In the case where the polarization directions of the two second linear actuators 3.1 and 3.2 are opposite to each other, the two second linear actuators 3.1 and 3.2 can be actuated with the same sinusoidal alternating voltage without phase shift.

[0036] According to the construction of the driver of the present invention, the contact movement and the driving movement of the friction element 4 can be performed independently or overlappingly. This means that, by actuating only the first linear actuator 2, the friction element 4 can initially perform a contact movement in the direction of the mobile member 11 until it contacts the bottom surface of the mobile member 11 and applies a certain contact pressure on the mobile member 11. Then, the two second linear actuators 3.1, 3.2 can be actuated in such a way that the friction element 4 performs a tilting movement in a direction parallel to the bottom surface of the mobile member 11, as described above. The friction element 4 pressed against the mobile member 11 thus causes the mobile member 11 to be advanced in this direction. By appropriately actuating the first linear actuator 2, the contact between the friction element 4 and the bottom surface of the mobile member 11 can be terminated again. Finally, the two second linear actuators 3.1, 3.2 can be actuated in such a way that the friction element 4 performs a tilting movement in the opposite direction, and therefore performs a reset movement. By repeating these actuation steps, the continuous advancement of the mobile member 11 can be achieved.

[0037] On the other hand, it is also possible to actuate the linear actuators 2, 3.1 and 3.2 in such a way that the contact movement and the driving movement of the friction element 4 overlap. This can result in an elliptical oscillation path of the friction element 4, the major axis of which is inclined relative to the bottom surface of the mobile member 11. If the friction element 4 oscillates on this path, a continuous advancement of the mobile member can also be achieved.

[0038] Figure 3 A drive group 10a is shown, in which two drive units 1 are arranged adjacent to each other and fixed in a common frame 8a, 9a. In particular, each drive unit 1 is arranged on a base element 8a and is attached to a structural element 9a via a bracket 6 and a spring element 7 by screws. The drive unit 1 is arranged along the feed direction of the mobile member, thereby extending the stroke of the mobile member, or in the case of a correspondingly long mobile member, doubling the driving force acting on the mobile member. The use of two drive units arranged adjacent to each other is only an example. Of course, more than three drive units can also be arranged adjacent to each other in the corresponding frame. The frame 8a, 9a can also be composed of multiple elements, and can even be constructed as one body, as long as it provides a suitable receiving portion for the drive unit 1.

[0039] Figure 4 A drive group 10b is shown, in which three drive units 1 are arranged along a circular path and fixed in a common frame 8b, 9b. Attachment and bonding of the drive units to the base element 8b and the structural element 9b of the frame Figure 3 Since the drive unit 1 is arranged on a circular path, a circular moving member can be used to realize rotational drive. Figure 3 Similar to the embodiment of the present invention, the frames 8b, 9b of the present embodiment may also be composed of a plurality of elements or constructed as one piece.

[0040] Reference numerals list

[0041] 1 Driver

[0042] 2 Piezoelectric Linear Actuator

[0043] 3.1, 3.2 Piezoelectric Linear Actuator

[0044] 4 Friction element

[0045] 5. Base

[0046] 6 Bracket

[0047] 7 Spring element

[0048] 8a, 8b Base element of the frame

[0049] 9a, 9b Structural elements of the frame

[0050] 10a, 10b drive group

[0051] 11 Mobile components

Claims

1. A piezoelectric motion and resonance driver, comprising a moving member (11), and At least one drive unit (1), comprising an assembly of a plurality of piezoelectric actuators (2, 3.1, 3.2) and a friction element (4) adapted to contact a moving member (11), wherein the assembly of the piezoelectric actuators (2, 3.1, 3.2) and the friction element (4) are coupled in such a way that when the piezoelectric actuators (2, 3.1, 3.2) are actuated, the friction element (4) can perform a contact movement toward or away from the moving member (11) to establish or terminate contact with the moving member (11), and can also perform a driving movement along the moving member (11) to drive the moving member, characterized in that Each piezoelectric actuator (2, 3.1, 3.2) of the assembly is a linear actuator.

2. Piezoelectric motion and resonance actuator according to the preceding claim, characterized in that The components of the piezoelectric actuator (2, 3.1, 3.2) and the friction element (4) are coupled in such a way that, when the piezoelectric actuator (2, 3.1, 3.2) is actuated, the friction element (4) can perform contact movement and drive movement independently of each other or in an overlapping manner.

3. Piezoelectric motion and resonance actuator according to one of the preceding claims, characterized in that The driving movement takes place in a plane or along an axis perpendicular to the axis of the contact movement.

4. Piezoelectric motion and resonance actuator according to one of the preceding claims, characterized in that The drive unit (1) comprises a base (5) which carries an assembly of piezoelectric actuators (2, 3.1, 3.2), wherein the contact movement preferably takes place perpendicularly to the base (5) and / or the drive movement takes place parallel to the base (5).

5. Piezoelectric motion and resonance actuator according to one of the preceding claims, characterized in that The piezoelectric actuators (2, 3.1, 3.2) of the assembly deflect in parallel directions, preferably parallel to the axis of the contact movement, when actuated.

6. Piezoelectric motion and resonance actuator according to one of the preceding claims, characterized in that Each piezoelectric actuator (2, 3.1, 3.2) is a multi-layer stack actuator which is designed to produce a deflection along its stack axis, which is preferably oriented parallel to the axis of the contact movement.

7. Piezoelectric motion and resonance actuator according to one of the preceding claims, characterized in that The piezoelectric actuators (2, 3.1, 3.2) are assigned individually actuatable actuator units (2, 3), wherein when a first actuator unit (2) is actuated by at least one piezoelectric actuator (2), the friction element (4) performs a contact movement, and when a second actuator unit is actuated by at least one, preferably two, other piezoelectric actuators (3.1, 3.2), the friction element (4) performs a drive movement.

8. Piezoelectric motion and resonance actuator according to one of the preceding claims, characterized in that The piezoelectric actuators (2, 3.1, 3.2) are arranged in the component along a plurality of, 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 motion and resonance actuator according to the preceding claim, characterized in that The bracket (6) is arranged between the two planes, and the piezoelectric actuators (2, 3.1, 3.2) in different planes are connected to each other via the bracket (6).

10. Piezoelectric motion and resonance actuator 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 adjacent to each other in the assembly, preferably via a base that carries the friction element (4).

11. Piezoelectric motion and resonance actuator according to one of the preceding claims, characterized in that The drive unit (1) is mounted in a frame (8a, 8b, 9a, 9b), preferably via a bracket (6) and / or a spring element (7) that passes through the piezoelectric actuator (2, 3.1, 3.2) assembly, the spring element (7) biasing the piezoelectric actuator (2, 3.1, 3.2) assembly against the frame (8a, 8b, 9a, 9b), and particularly preferably including a groove through which the friction element (4) protrudes.

12. Piezoelectric motion and resonance actuator according to one of the preceding claims, characterized in that The assembly of piezoelectric actuators (2, 3.1, 3.2) comprises three piezoelectric actuators, wherein one piezoelectric actuator (2) is arranged in a first plane and two piezoelectric actuators (3.1, 3.2) are arranged in a second plane located above the first plane, wherein the two piezoelectric actuators (3.1, 3.2) of the second plane are arranged adjacent to each other.

13. Piezoelectric motion and resonance actuator according to one of the preceding claims, characterized in that At least two drive units (1) are arranged adjacent to each other in a direction parallel to the direction of the drive movement, or at least three drive units (1) are arranged along a circular path.

14. Piezoelectric motion and resonance actuator according to one of the preceding claims, characterized in that The driver comprises a control unit for actuating a piezoelectric actuator (2, 3.1, 3.2) with an electrical control voltage.

15. A method for actuating a piezoelectric motion and resonant actuator, comprising: a moving member (11), and At least one drive unit (1) comprising an assembly of a plurality of piezoelectric linear actuators (2, 3.1, 3.2) and a friction element (4) suitable for contacting a moving member, wherein at least one piezoelectric linear actuator (2) of the assembly is actuated in such a way that the friction element (4) performs a contact movement towards or away from the moving member in order to establish or terminate contact with the moving member, and at least one other piezoelectric linear actuator (3.1, 3.2), preferably two other piezoelectric linear actuators (3.1, 3.2) are arranged in such a way that the friction element (4) performs a driving movement along the moving member (11).

16. The method according to the preceding claim, characterized in that The two piezoelectric linear actuators (3.1, 3.2) causing the driving movement of the friction element (4) are actuated so that they are in anti-phase.

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