Abstract: A block of stacked green films provided with internal electrodes is laminated, at least one actuator is separated from the block, the actuator obtains its shape by means of a machining operation, is then sintered, and the sinter skin produced by the sintering is used as an insulating layer. The sinter skin is abraded at the points where the internal electrodes are connected to the external electrodes.

Abstract: The invention relates to a method for the manufacture of piezoelectric multilayer actuator in which thin layers of a piezoceramic material, called “green leaves” on which at least one internal electrode is applied, are stacked to form a block such that the internal electrodes are guided in alternation to oppositely lying surfaces of the actuator, where they become bound together by an external electrode, the actuator compact being sintered and subjected to abrasive shaping, and then the base metallization is applied for the external electrode.

Abstract: In piezoceramic multilayer actuators, the head region and the foot region consist of inactive, that is to say electrode-free, piezoceramic layers. Due to the arrangement of the metallic electrodes and the layers of the piezoceramic materials, the shrinkage of the piezoceramic material, in particular in the passive head region and foot region, is influenced during the sintering process and can cause the formation of cracks. Different expansion behavior of the active and of the passive region during operation also lead to stresses which favor crack formation, in particular at the boundary between both regions. According to the invention, it is therefore proposed that a transition region (11), whose shrinkage and expansion behavior lies between the shrinkage and expansion behavior of the active region (10) and the shrinkage and expansion behavior of an inactive region (8, 9) which are electrode free, adjoins the active region (10) up to the inactive head region (8) and up to the inactive foot region (9).

Abstract: In external electrodes on piezoceramic multi-layer actuators, high tensile stresses act during operation on the insulating region below the base metallic coating. Problems are caused by the linking of the electrode with a conductive connection, via which the electric voltage is to be supplied. The soldering or welding process reinforces the external electrode, which thus loses elasticity at the soldering or welding point. During operation, mechanical shear stresses then occur beneath said soldering or welding points, as the electrode region lying above no longer expands. After several million operating cycles, this causes the external electrode together with the base metallic coating to become detached, thus leading to the failure of the component.

Abstract: The invention relates to a monolithic multilayer actuator comprising a sintered stack of thin films, made from piezo-ceramic with inlaid metallic inner electrodes which extend from the stack on alternate sides and are electrically wired in parallel with external electrodes (3, 4) and are provided with connector wires (5). According to the invention, the actuator may be supplied with nominal voltage over a long period of time, without a change in the properties thereof, whereby the multilayer actuator (1) is sealed within a metallic or ceramic housing (8, 11, 16), the connector wires (5) are integral parts of the housing base (11) and the housing (8, 11, 16) is filled with a water-absorbing medium (14) and a water-transporting, electrically-insulating medium (15).

Abstract: The invention relates to a monolithic multilayer actuator comprising a sintered stack of thin films, made from piezo-ceramic with inlaid metalic inner electrodes which extend from the stack on alternate sides and are electrically wired in parallel with external electrodes (3, 4) and are provided with connector wires (5). According to the invention, the actuator may be supplied with nominal voltage over a long period of time, without a change in the properties thereof, whereby the multilayer actuator (1) is sealed within a metallic or ceramic housing (8, 11, 16), the connector wires (5) are integral parts of the housing base (11) and the housing (8, 11, 16) is filled with a water-absorbing medium (14) and a water-transporting, electrically-insulating medium (15).

Abstract: For the manufacture of multilayer actuators, the laminate is split into several actuators, which are pyrolized and then sintered. Because lamination in the unsintered body often produces non-homogeneity in the density, and the shrinkage during the firing of the ceramic is not of a constant value, the final geometry of the actuators can only be accurately obtained by the hardening of the sintered actuators. But in this case the internal electrode layers deposited in the actuators are thereby also processed, which can cause electrical flashovers and leakage currents during operation.

Abstract: The invention relates to a method for the manufacture of piezoelectric multilayer actors in which thin layers of a piezoceramic material, called “green leaves” on which at least one internal electrode is applied, are stacked to form a block such that the internal electrodes are guided in alternation to oppositely lying surfaces of the actor, where they become bound together by an external electrode, the actor compact being sintered and subjected to abrasive shaping, and then the base metallization is applied for the external electrode.

Abstract: During operation, large tensile stresses act on the insulating region under the base metallization with external electrodes on piezoceramic multilayer actuators. Since this insulating region forms a homogeneous unit together with the base metallization and the interconnecting layer, this fails when the tensile strength of the weakest element is exceeded and cracks develop. The cracks running unchecked through the insulating region are very critical, since they reduce the insulation distance and seriously increase the probability of actuator failure due to flashovers. According to the invention it is therefore proposed that, in the inactive region (14), the surface (10) of the multilayer actuator (1) has a pattern (18) that is produced by erosions (19) interrupting the surface (10), and that the base metallization (11) is deposited exclusively on the surface (10) left by the pattern (18).

Abstract: A directly actuated electric valve is proposed that has a piezoelectric drive unit (3) for direct actuation of a valve member (2). The piezoelectric drive unit (3) contains, extending transverse to the displacement direction of valve member (2), at least one piezo-flexural element (8, 8′), which acts on valve member (2) at one end and is mounted stationary with respect to the housing at the other, such that its electrically induced flexural motion produces the linear displacement motion of valve member (2). Such a configuration permits very short switching times with compact dimensions.

Abstract: In piezoceramic multilayer actuators, the head region and the foot region consist of inactive, that is to say electrode-free, piezoceramic layers. Due to the arrangement of the metallic electrodes and the layers of the piezoceramic materials, the shrinkage of the piezoceramic material, in particular in the passive head region and foot region, is influenced during the sintering process and can cause the formation of cracks. Different expansion behaviour of the active and of the passive region during operation also lead to stresses which favour crack formation, in particular at the boundary between both regions.

Abstract: For the manufacture of multilayer actuators, the laminate is split into several actuators, which are pyrolized and then sintered. Because lamination in the unsintered body often produces non-homogeneity in the density, and the shrinkage during the firing of the ceramic is not of a constant value, the final geometry of the actuators can only be accurately obtained by the hardening of the sintered actuators. But in this case the internal electrode layers deposited in the actuators are thereby also processed, which can cause electrical flashovers and leakage currents during operation.

Abstract: During operation, large tensile stresses act on the insulating region under the base metallization with external electrodes on piezoceramic multilayer actuators. Since this insulating region forms a homogeneous unit together with the base metallization and the interconnecting layer, this fails when the tensile strength of the weakest element is exceeded and cracks develop. The cracks running unchecked through the insulating region are very critical, since they reduce the insulation distance and seriously increase the probability of actuator failure due to flashovers.

Abstract: A monolithic multi-layer actuator includes a sintered stack of thin films of piezoceramic material with metallic internal electrodes which lead out of the stack (2) in alternate directions and are connected electrically in parallel by way of external electrodes, with the external electrodes on the contact sides of the stack consisting of an applied basic metallisation and being connected to electrical connection elements preferably by way of soldering. In order to avoid failures of the actuator during dynamic loads it is suggested that an electroconductive electrode which is structured to be three-dimensional in structure be arranged between the basic metal lining and the connection elements, which electrode is connected to the basic metallisation by way of partial contact points and is constructed to be expandable between the contact points.