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DE-102014101512-B4 - Piezoelectric actuator

DE102014101512B4DE 102014101512 B4DE102014101512 B4DE 102014101512B4DE-102014101512-B4

Abstract

Piezoelectric actuating device (11, 11'), in particular a piezoelectric metering valve, with a piezoelectric stack (17) comprising a plurality of stacked layers (21) of piezoelectric material, each provided with electrodes (19, 20), and a lever (22, 22') mechanically connected to the piezoelectric stack (17) for converting a drive movement of the stack (17) into an actuating movement of an actuating element (15) provided on the lever (22, 22'), in particular a valve plunger. and with a cooling device (30) for removing heat from the piezoelectric stack (17), wherein the piezoelectric stack (17) is divided into at least two substacks (17A, 17B) arranged side by side and each equipped with associated electrodes (19, 20), wherein the substacks (17A, 17B) are separated from each other by a space (34), wherein the cooling device (30) is at least partially arranged in the space (34) and/or fluid present in the space (34) forms part of the cooling device (30), and wherein the cooling device (30) comprises at least one cooling element (37, 39) made of a thermally conductive material, preferably metal, arranged at least partially in the space (34), characterized by the fact that as a heat sink a base cooling fin (37) extending from a base (25) and projecting into the space (34) and/or a base cooling fin extending from The lever cooling fin (39) is/are provided extending from the lever (22, 22') and projecting into the space (34).

Inventors

  • Martin Reuter

Assignees

  • MARCO SYSTEMANALYSE UND ENTWICKLUNG GMBH

Dates

Publication Date
20260513
Application Date
20140206

Claims (13)

  1. Piezoelectric actuating device (11, 11'), in particular a piezoelectric metering valve, comprising a piezoelectric stack (17) which includes a plurality of stacked layers (21) of piezoelectric material, each provided with electrodes (19, 20), a lever (22, 22') mechanically connected to the piezoelectric stack (17) for converting a drive movement of the stack (17) into an actuating movement of an actuating element (15) provided on the lever (22, 22'), in particular a valve plunger, and a cooling device (30) for dissipating heat from the piezoelectric stack (17), wherein the piezoelectric stack (17) is divided into at least two sub-stacks (17A, 17B) arranged side by side and each provided with associated electrodes (19, 20), wherein the sub-stacks (17A, 17B) are separated from each other by a space (34), wherein the cooling device (30) is at least partially arranged in the space (34) and/or fluid present in the space (34) forms part of the cooling device (30), and wherein the cooling device (30) comprises at least one cooling element (37, 39) made of a thermally conductive material, preferably metal, which is at least partially arranged in the space (34), characterized in that a base cooling fin (37) extending from a base (25) and projecting into the space (34) and/or a lever cooling fin (39) extending from the lever (22, 22') and projecting into the space (34) is/are provided as a cooling element.
  2. Actuating device according to Claim 1 , characterized in that the cooling device (30) comprises a layer (33) of thermally conductive material, via which at least one outer surface (31), in particular a side surface, of the piezoelectric stack (17) is in contact with a wall section of a housing (13) of the actuating device (11, 11').
  3. Actuating device according to Claim 1 or 2 , characterized in that the piezoelectric stack (17) is divided into exactly two substacks (17A, 17B) arranged next to each other and each provided with associated electrodes (19, 20).
  4. Actuating device according to Claim 3 , characterized in that the piezoelectric stack (17) is divided along a division plane parallel to the stacking direction (S), preferably into identically sized sub-stacks (17A, 17B).
  5. Actuating device according to one of the preceding claims, characterized in that the cooling device (30) comprises a thermally conductive material with which free spaces are filled that are present in the space (34) between the surfaces of the sub-stacks (17A, 17B) and, if applicable, components present in the space (34).
  6. Actuating device according to one of the preceding claims, characterized in that the piezoelectric stack (17) is clamped by means of a clamping element (43) between a base (25) common to all sub-stacks (17A, 17B) and a counter-base (27, 27') common to all sub-stacks (17A, 17B), wherein the clamping element (43) extends parallel to the stacking direction (S) through the space (34).
  7. Actuating device according to Claim 6 , characterized in that the clamping element (43) comprises a shaft section (45) with a flattened cross-section intended for arrangement in the space (34).
  8. Actuating device (11') according to one of the preceding claims, characterized in that the base (25) is mechanically connected to a first end face of the stack (17) and the lever (22') is mechanically connected to a second end face of the stack (17), wherein at least one section of a force transmission arrangement (55) comprising the base (25), the piezoelectric stack (17) and the lever (22') is spring-elastic in order to cause the actuating movement to overshoot the drive movement.
  9. Actuating device according to Claim 8 , characterized in that the lever (22') has a pivot point (50) which enables a spring-loaded pivoting of a first lever part relative to a second lever part or of the lever (22') itself relative to an adjacent component (27).
  10. Actuating device according to Claim 9 , characterized in that the joint point (50) is formed by a flexible section (49) of the lever (22').
  11. Actuating device according to Claim 9 or 10 , characterized in that the lever (22') has a reduced cross-sectional size and/or a changed cross-sectional shape in the area of the joint point (50).
  12. Actuating device according to one of the Claims 8 until 11 , characterized in that the resonance frequency of the oscillating force transmission arrangement (55) is adapted to a predetermined nominal frequency of the actuating element (15).
  13. Actuating device according to one of the Claims 8 until 12 , characterized by an electronic control device designed to operate the piezoelectric stack (17) substantially at the resonant frequency of the oscillating force transmission arrangement (55).

Description

The present invention relates to a piezoelectric actuating device, in particular a piezoelectric metering valve, with a piezoelectric stack comprising a plurality of stacked layers of piezoelectric material, each provided with electrodes, and a lever mechanically connected to the piezoelectric stack for converting a drive movement of the stack into an actuating movement of an actuating element provided on the lever, in particular a valve plunger. Piezoelectric actuators are characterized by high positioning accuracy and fast switching behavior. In such devices, the piezoelectric stack can be clamped between a base and a counter-base to provide the necessary preload. The lever can either be attached to the counter-base as a separate component or be integrally formed with it. Especially with metering valves in process engineering, the aim is to achieve the highest possible switching frequency. A limiting factor here is the heat energy inevitably generated within the piezoelectric stack during operation, which typically amounts to about 10% to 20% of the supplied energy and can lead to undesirable overheating of the stack. Since piezoelectric ceramic components have a comparatively low thermal conductivity, the problem of potential overheating is particularly acute with high-power piezoelectric stacks and correspondingly large volumes. The DE 100 42 941 A1 Disclosing a piezoelectric actuator with two stacks arranged side by side, clamped between two clamping plates, wherein the associated clamping element extends through the space formed between the stacks. In the DE 10 2010 015 171 A1 is disclosed a piezoelectric actuator with two adjacent stacks protected by a plastic casing provided with cooling channels. The DE 101 41 820 A1 reveals a piezoelectric component comprising several ceramic layers. In the DE 10 2006 026 932 A1 A piezo actuator with a housing and a heat sink attached to it is revealed. The WO 00/63 980 A1 reveals a piezoelectric actuator with an actuator body in the form of a multilayer laminate. It is an object of the invention to extend the application range of piezoelectric actuators of the type mentioned above and in particular to enable higher switching frequencies. The problem is solved by a piezoelectric actuator with the features of claim 1. According to the invention, a piezoelectric actuator comprises a cooling device for dissipating heat from the piezoelectric stack. Depending on the application, such a cooling device can operate passively, i.e., by transferring heat to the surrounding air, or actively using a transported cooling fluid. A combination of active and passive cooling is also possible. Due to the integrated cooling device, a piezoelectric stack of a given volume can be controlled at a higher frequency, as the risk of heat buildup within it is reduced. The cooling device can comprise a layer of thermally conductive material through which at least one outer surface, in particular a side surface, of the piezoelectric stack is in contact with a wall section of a housing of the actuator. Such a layer with increased thermal conductivity allows heat energy to be efficiently dissipated from the stack surface, ultimately contributing to a temperature reduction inside the stack. Preferably, the layer of thermally conductive material extends over the entire surface of the outer surface in question. Particularly in the case of the narrow housing shape desired for many metering valves, connecting two opposite side surfaces of the piezoelectric stack to the housing wall via corresponding separate layers of thermally conductive material can be advantageous. The invention provides that the piezoelectric stack is divided into at least two, preferably exactly two, adjacent sub-stacks, each equipped with its own electrodes. This increases the stack surface area while maintaining essentially the same power output, thus facilitating heat dissipation from the stack. If the application requires it, a division into more than two sub-stacks is also possible. The piezoelectric stack can be arranged in particular along a direction parallel to the stacking direction. The stack is divided along the dividing plane, preferably into identically sized sub-stacks. In other words, the thickness of the stack is preferably divided. Such a division does not affect the maximum deflection of the stack. According to the invention, the sub-stacks are separated from each other by an intermediate space. This counteracts unwanted heat transfer between the sub-stacks. Furthermore, it is planned that the cooling device is at least partially located in the space between the stacks and/or that fluid present in the space, such as air, forms part of the cooling device. This not only enables effective heat dissipation from the area between the stacks, but also a particularly space-saving design. According to the invention, the cooling device comprises at least one heat sink made of a thermally conductive material, preferably