DE102007056553A1 - Method for producing piezo actuator module, involves applying isolation protective layer made of plastic as passivating casing, which is created in electrically conductive manner by coating process - Google Patents

Abstract

The method involves applying isolation protective layer (6) made of plastic as passivating casing, which is created in electrically conductive manner by a coating process. A metallic protective layer (7) is applied galvanically on isolation protective layer made of plastic by another coating method. The portions for colonization are created with metallic elements during former coating process by etching process that is carried with chromic-sulfuric acid and metallic elements consist of palladium. The former coating process is carried with ductile materials, particularly copper or silver. An independent claim is included for a piezo actuator module.

Description

State of the art

The The invention relates to a manufacturing method for a piezoelectric actuator module and a piezoelectric actuator surrounded by liquid media with a wrapper to Anbindebauteile, preferably for Use in a piezo injector, according to the generic Features of method claim 1 and claim 7.

One Such piezo injector consists essentially of a holding body and the piezoelectric actuator module arranged in the holding body, arranged the between a head and foot as Anbindebauteile Piezo actuator made of several stacked piezo elements to form the piezoelectric actuator.

It is known per se that to build the aforementioned Piezoaktors or piezoelectric actuator piezoelectric elements are used so can, that taking advantage of the so-called piezo effect one Control of the needle stroke of a valve or the like made can be. Piezo layers of the piezo elements are made of one material with a suitable crystal structure so constructed that when plant an external electrical voltage a mechanical Reaction of the piezoelectric element takes place, depending on from the crystal structure and the plant areas of the electric Stress represents a pressure or train in a predeterminable direction. such Piezo actuators are suitable, for example, for applications in which strokes under high operating forces and high clock frequencies expire.

For example, such a piezoelectric actuator as part of a piezoelectric injector in so-called common rail injection systems (CR injector) from the DE 10026005 A1 known. In this piezoelectric actuator piezo elements are also arranged as a stack, which is held via an actuator base and an actuator head under bias between two stops. Each piezo layer is also enclosed between two internal electrodes, via which an electrical voltage can be applied from the outside. Because of this electrical voltage, the piezoelectric elements then each carry out small strokes in the direction of the potential gradient, which add up to the total stroke of the piezoelectric actuator. This total stroke is variable by the amount of voltage applied and can be transferred to a mechanical actuator.

at This known CR injectors is one indirectly from the piezoelectric actuator controlled nozzle needle as a fuel valve present, wherein the piezoelectric actuator a realization of the opening and closing function allows. To achieve an optimal deflection at The internal electrodes of the piezoelectric actuator need minimal space the entire cross section of the piezoelectric actuator, except for the inactive contacting zone, include. This means that the internal electrodes are more alternating Polarity on the sides of the ceramic layers exposed.

Out This reason is an electrical passivation of these sides of the piezoelectric actuator and the contact attachment or Anbindeteile for electrical passivation of the entire piezoelectric actuator module necessary, to an infiltration of the piezoelectric actuator with the flowing around Media and the possibly associated electrical flashovers or short circuits between adjacent internal electrodes to avoid. This can be caused for example by moisture or the Operating materials themselves, for example diesel, rapeseed methyl ester, water or the like, caused in the operation of the piezoelectric actuator.

In order to achieve an electrical and mechanical insulation of the piezoelectric actuator, a flexible sheathing of the piezoelectric actuator is often proposed. From the DE 10230032 A1 To avoid the disadvantages described above, an arrangement with a piezoelectric actuator module in flowing media is known in which the piezoelectric elements are encapsulated in a shape-changing insulating compound, which in turn is introduced into a laterally and at the upper and lower end opposite the medium sealed housing shell.

The Both ends of this housing shell can be in the range their attachment to the steel connection parts of the head part and the foot part However, the piezoelectric actuator module are infiltrated by the fuel and the known arrangements thus offer no reliable Density protection, so that the proper function of the piezoelectric actuator over its life is endangered.

From the DE 101 21 270 A1 or the DE 198 18 036 B4 For example, a passivation material for piezoelectric components is known that consists of polyurethane or a silicone rubber or a fluorinated silicone elastomer or solid silicone.

Disclosure of the invention

The invention relates to a method for producing a piezoelectric actuator and a surrounding the piezoelectric actuator sheath for electrical passivation, in which according to the invention in an advantageous manner as a passivating cladding first an insulation protective layer of plastic according to the characterizing part of the main claim is applied to the piezoceramic layers of the piezoelectric actuator to protect or isolate. As a bridge between the usually metallic actuator head or the actuator base as Anbindebauteile for Kunsstoffisolierung the piezoelectric actuator one or more layers are applied galvanically depending on the application. Advantageous embodiments are specified in the subclaims.

An etching process as preparation for the coating can, for example, with chromic acid can be performed and the metallic elements preferably made of palladium and the subsequent galvanic Coating process may preferably be done with ductile depositable materials, preferably copper or silver.

Consequently can according to the invention, the compound of electrical passivation of the piezoelectric actuator to the tethering components, as actuator head and actuator foot of a piezoelectric actuator, on galvanic base by means of single-layer or multilayer systems easy way in the first or in the second coating process done. It is thus a moisture-proof or fuel-tight and pressure-tight bond between the electrical passivation made of plastic and the connecting parts on the front surfaces the piezoelectric actuator generates, whereby the infiltration of moisture or supplies to the ceramic piezoelectric actuator of the piezoelectric actuator module is avoided.

With this galvanic connection by means of single-layer or multilayer systems is a cost effective for a mass production process and process-safe coating variant has been found. additionally resulting in competitive advantages and thus increased Market share. The layer thicknesses start in the single-digit ⫿m range and so do not affect the installation conditions. The used Depending on the requirements of the media resistance, materials can be used be adjusted.

at A preferred application is the piezoelectric actuator module thus produced Part of a piezo injector with direct needle control for an injection system for fuel in an internal combustion engine, wherein the fuel flows around the enclosure under high pressure.

Brief description of the drawings

One Embodiment of the inventive Method produced piezoelectric actuator is based on the drawing explained. It shows:

1 a section through a piezoelectric actuator with a galvanically coated piezoelectric actuator with tethering components.

Embodiment of invention

In 1 is a basic structure of a piezoelectric actuator module 1 , For example, shown for a piezo injector, which can be used for example for Nadelhubsteuerung in an injection system for fuel in an internal combustion engine.

Inside the piezo actuator module 1 is a piezoelectric actuator 2 with the piezo elements described in the introduction to the description 3 present, the end face with an actuator head 4 and an actuator foot 5 is connected as a metallic tethering components. Essentially on the electrically active outer surface of the piezoelectric actuator 2 and the border areas to the actuator head 4 and to the actuator base 5 is an enveloping insulation protection layer 6 , preferably made of plastic, for electrical passivation of the components 2 to 5 placed in a first coating process.

According to the invention, the insulation protective layer 6 made media stable in the first and / or second coating process and with the adjacent attachment parts 4 and 5 galvanically connected.

It is thus a moisture-tight or fuel-tight and pressure-tight bond between the electrical passivation with the insulation protective layer 6 made of plastic on the piezoelectric actuator 2 and the tethering components 4 and 5 at the end face areas of the piezoelectric actuator 2 available. This is the infiltration of moisture or the piezoelectric actuator 1 flowing fluids to the ceramic piezoelectric actuator 2 avoided.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10026005 A1 [0004]
• - DE 10230032 A1 [0007]
• - DE 10121270 A1 [0009]
• - DE 19818036 B4 [0009]

Claims (8)

Method for producing a piezoelectric actuator module ( 1 ) with attachment parts, consisting of actuator head ( 4 ) and actuator base ( 5 ), and one the piezoelectric actuator module ( 1 ) surrounding enclosure for electrical passivation, characterized in that as passivating cladding an insulation protective layer ( 6 ) is applied from plastic, which is made electrically conductive by means of a first coating process and that by means of a second coating process, a metallic protective layer ( 7 ) on the insulation protective layer ( 6 ) is applied galvanically from plastic. A method according to claim 1, characterized in that in the second galvanic coating process, the passivating coating with the insulation protective layer ( 6 ) made of plastic and the actuator head ( 4 ) and the actuator base ( 5 ) are galvanically coated contiguously. Method according to claim 1 or 2, characterized that in the first coating process metallic elements in the Plastic are incorporated as the basis for which serve the subsequent second galvanic coating process. Method according to claim 3, characterized that in the first coating process by an etching process Areas for colonization with the metallic elements be created. Method according to claim 4, characterized in that that carried out the etching process with chromic acid and the metallic elements are made of palladium. Method according to one of the preceding claims, characterized in that the second coating process with ductile depositable materials, preferably copper or silver, is carried out. Piezoactuator module, which is produced according to a method of the preceding claims, characterized in that the layer composite with the insulation protective layer ( 6 ) and the metallic protective layer ( 7 ) has a layer thickness which begins in the single-digit ⫿m range and represents a galvanic coating that can be applied by means of single-layer or multilayer systems. Piezoelectric actuator according to claim 7, characterized in that the piezoelectric actuator module ( 1 ) Is part of a piezo injector with direct needle control for an injection system for fuel in an internal combustion engine, wherein the fuel flows around the enclosure under high pressure.