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Method for producing a monolithic piezo actuator with stack elements, monilithic piezo actuator with stack elements, and use of the piezo actuator

Method for producing a monolithic piezo actuator with stack elements, monilithic piezo actuator with stack elements, and use of the piezo actuator description/claims

This application is a U.S. national stage application of International Application No. PCT/EP2006/007405 filed Jul. 26, 2006, which designates the United States of America, and claims priority to German application number 10 2005 034 814.9 filed Jul. 26, 2005, the contents of which are hereby incorporated by reference in their entirety.

The invention relates to a method for producing a monolithic piezo actuator featuring stack elements stacked one above the other. In addition a monolithic piezo actuator and a use of the piezo actuator are specified.

Piezo actuators are known that consist of a plurality of stack elements arranged one above the other. Each of the stack elements features piezoceramic layers arranged above one another made of a piezoceramic material and electrode layers (internal electrodes) arranged between the piezoceramic layers. With monolithic, i.e. one-piece piezo actuators, the entire arrangement consisting of piezoceramic layers and electrode layers is obtained in a common sintering process. The result is a total monolithic stack consisting of stack elements.

When such piezo actuators are electrically activated for the first time up into the high signal range (field strengths of several kV/mm) the piezoceramic material is polarized. This results in an irreversible length change, the so-called remanent extension. Because of the remanent extension and because of an additional extension occurring on electrical activation of the electrode layers in the operation of the piezo actuator, tensile stresses occur in the total stack. These tensile stresses lead, during the polarization or in the operation of the piezo actuator, to cracks (polarization cracks) occurring for example along a boundary surface between a piezoceramic layer and an electrode layer. Cracks which form branches or propagate in the longitudinal direction of the total stack are especially damaging here. Such cracks inevitably lead to the premature failure of the piezo actuator.

There exists a need for a method of producing piezo actuators in which excessive tensile stress which could lead to the formation of the polarization cracks described above does not occur either during polarization or in operation.

According to an embodiment, in a method for producing a monolithic multilayer piezo actuator, comprising: a stack element and at least one further stack element, wherein each of the stack elements comprises piezoceramic layers arranged above one another and electrode layers arranged between the piezoceramic layers, each of the electrode layers of the respective stack element extends to at least one of at least two side surface sections of the stack element,

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Electrical generator or motor structure

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