Patent Application
20190280184
No federal government funds were used in researching or developing this invention.
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The present invention relates to a piezoelectric transmission and/or reception device, vibration sensor comprising a piezoelectric transmission and/or reception device of said type, and method for manufacturing a piezoelectric transmission and/or reception device.
The present invention relates to a piezoelectric transmission and/or reception device, a vibration sensor comprising such a piezoelectric transmission and/or reception device and a method for manufacturing such a piezoelectric transmission and/or reception device, each according to the following disclosure.
Piezoelectric transmission and/or reception devices, vibration sensors equipped with such transmission and/or reception devices, as well as methods for the production of piezoelectric transmission and/or reception devices are known from prior art, with the piezoelectric transmission and/or reception devices comprising at least one piezo-element, at least two electrodes for contacting the piezo-element, as well as at least two isolation elements for isolating towards the top and the bottom, with the individual elements to form piezoelectric transmission and/or reception devices being stacked loosely on top of each other. In order to ensure the correct alignment of the individual components they are either embodied in an annular fashion or arranged on a centrally arranged bolt, or the disk-shaped components are aligned in reference to each other in a sheath embodied as a housing.
The above-described piezoelectric transmission and/or reception devices may be used for example in vibration sensors, which are frequently used in fill level measuring technology as limit sensors, as transmission and/or reception devices. Frequently such piezoelectric transmission and/or reception devices are also called drives.
An electromechanical drive in a laminar design is known from WO 01/84642 A1, in which individual components, which are metal-coated at their mutually facing surfaces, are connected by way of diffusion welding. In order to allow connecting individual components to join with each other by way of diffusion welding, the surfaces abutting each other must show very high surface quality and the arrangement must be heated up to slightly below the solidus line of the material used for diffusion welding, so that then a solid connection of the individual components can form.
In the method using the technology of prior art, it is considered disadvantageous that the components provided for the diffusion welding must show a very high surface quality and a very high temperature must be given for the diffusion welding. In particular, in the piezoelectric transmission and/or reception devices underlying the present invention, this method can be used with difficulty only, since the piezo-elements lose their piezoelectric features when heated above their Curie-temperature, and thus become useless, or have to be newly polarized. Further, the components required for diffusion welding are expensive in their production and the manufacturing process is elaborate. This is caused by the expensive production of the necessary surface quality, as well as subsequent polarization of the piezo, which typically occurs at voltages from 500 to 1,000 V or more, and requires a protective atmosphere.
The objective of the present invention is to provide an improved piezoelectric transmission and/or reception device. In particular, considerably lower temperatures are sufficient for the production of it, so that it can be produced in a less costly and easier fashion. Further, the objective of the present invention is to provide a method for the production of such a piezoelectric transmission and/or reception device.
These objectives are attained in a piezoelectric transmission and/or reception device with the features and the method for producing a piezoelectric transmission and/or reception device with the features as described further herein. A vibration sensor with a piezoelectric transmission and/or reception device according to the invention is disclosed herein as well, along with advantageous additional embodiments.
In a preferred embodiment, a piezoelectric transmission and/or reception device (1) comprising
In another preferred embodiment, the piezoelectric transmission and/or reception device (1) as described herein, characterized in that the mono-block comprises additionally the isolation elements (7).
In another preferred embodiment, the piezoelectric transmission and/or reception device (1) as described herein, characterized in that the piezoelectric transmission and/or reception device (1) comprises n-piezo elements (3) and n+1 electrodes (5), which are arranged in an alternating fashion and are sintered to form a mono-block.
In another preferred embodiment, the piezoelectric transmission and/or reception device (1) as described herein, characterized in that the piezoelectric transmission and/or reception device (1) comprises a transmission device (10) and a reception device (11), which respectively comprise n-piezo elements (3) and n+1 electrodes (5), which are arranged in an alternating fashion, with the transmission device (10) and the reception device (11) being electrically isolated from each other by the separating ceramic (13) and all components being sintered to form a mono-block.
In another preferred embodiment, the piezoelectric transmission and/or reception device (1) as described herein, characterized in that the mono-block comprises additionally a preferably metallic pressure part (15) for transmitting any oscillation generated.
In another preferred embodiment, the piezoelectric transmission and/or reception device (1) as described herein, characterized in that the piezo elements (3) and the electrodes (5) are embodied as annular disks.
In another preferred embodiment, the piezoelectric transmission and/or reception device (1) as described herein, characterized in that the piezo elements (3) and the electrodes (5) are embodied as annular disks.
In another preferred embodiment, the piezoelectric transmission and/or reception device (1) as described herein, characterized in that the piezo elements (3) show a thickness (d) of less than 1.0 mm, preferably less than 0.5 mm.
In another preferred embodiment, the piezoelectric transmission and/or reception device (1) as described herein, characterized in that the piezo elements (3) and/or the electrodes (5) and/or the isolation elements (7) and/or the separating ceramic (13) show an average surface roughness of more than 6.3, preferably more than 16.
In another preferred embodiment, the piezoelectric transmission and/or reception device (1) as described herein, characterized in that The mono-block is produced via a silver-sintering process.
In an alternate preferred embodiment, a vibration sensor (100) with a piezoelectric transmission and/or reception device (1) with a diaphragm (90) that can be made to vibrate, a clamping device (96) for clamping the piezoelectric transmission and/or reception device (1) towards the diaphragm (90) such that oscillations of the transmission and/or reception device (1) are transferred to the diaphragm (90) and the oscillations of the diaphragm (90) to the transmission and/or reception device (1), characterized in that the transmission and/or reception device (1) are embodied according to any of the previous claims.
In an alternate preferred embodiment, a method for the production of a piezoelectric transmission and/or reception device (1) with the following steps:
In another preferred embodiment, the method as described herein, characterized in that the coating process comprises the application of a sinter paste via template printing, a dispenser, or serigraphy, or the application of a sinter film.
In another preferred embodiment, the method as described herein, characterized in that the coating process comprises a drying step after the application.
In another preferred embodiment, the method as described herein, characterized in that a sintering material is used comprising silver particles with a size from 100 nm to 500 nm.
In another preferred embodiment, the method as described herein, characterized in that the sinter temperature (T) amounts to less than 300° C., preferably less than 280° C., further preferred ranges from 200° C. to 250° C.
In another preferred embodiment, the method as described herein, characterized in that the sintering process occurs at a pressure (p) of less than 20 MPa, preferably occurs at 5 MPa, further preferred at atmospheric pressure.
Piezoelectric transmission and/or reception devices, vibration sensors equipped with such transmission and/or reception devices, as well as methods for the production of piezoelectric transmission and/or reception devices are known from prior art, with the piezoelectric transmission and/or reception devices comprising at least one piezo-element, at least two electrodes for contacting the piezo-element, as well as at least two isolation elements for isolating towards the top and the bottom, with the individual elements to form piezoelectric transmission and/or reception devices being stacked loosely on top of each other. In order to ensure the correct alignment of the individual components they are either embodied in an annular fashion or arranged on a centrally arranged bolt, or the disk-shaped components are aligned in reference to each other in a sheath embodied as a housing.
The above-described piezoelectric transmission and/or reception devices may be used for example in vibration sensors, which are frequently used in fill level measuring technology as limit sensors, as transmission and/or reception devices. Frequently such piezoelectric transmission and/or reception devices are also called drives.
An electromechanical drive in a laminar design is known from WO 01/84642 A1, in which individual components, which are metal-coated at their mutually facing surfaces, are connected by way of diffusion welding. In order to allow connecting individual components to join with each other by way of diffusion welding, the surfaces abutting each other must show very high surface quality and the arrangement must be heated up to slightly below the solidus line of the material used for diffusion welding, so that then a solid connection of the individual components can form.
In the method using the technology of prior art, it is considered disadvantageous that the components provided for the diffusion welding must show a very high surface quality and a very high temperature must be given for the diffusion welding. In particular, in the piezoelectric transmission and/or reception devices underlying the present invention, this method can be used with difficulty only, since the piezo-elements lose their piezoelectric features when heated above their Curie-temperature, and thus become useless, or have to be newly polarized. Further, the components required for diffusion welding are expensive in their production and the manufacturing process is elaborate. This is caused by the expensive production of the necessary surface quality, as well as subsequent polarization of the piezo, which typically occurs at voltages from 500 to 1,000 V or more, and requires a protective atmosphere.
The objective of the present invention is to provide an improved piezoelectric transmission and/or reception device. In particular, considerably lower temperatures are sufficient for the production of it, so that it can be produced in a less costly and easier fashion. Further, the objective of the present invention is to provide a method for the production of such a piezoelectric transmission and/or reception device.
These objectives are attained in a piezoelectric transmission and/or reception device with the features of claim 1 as well as the method for producing a piezoelectric transmission and/or reception device with the features of claim 12. A vibration sensor with a piezoelectric transmission and/or reception device according to the invention is disclosed in claim 11.
Advantageous embodiments are disclosed in the dependent claims.
The piezoelectric transmission and/or reception device according to the invention comprises at least one piezo element, at least two electrodes for contacting the piezo element, as well as at least two isolation elements for the isolation towards the top and the bottom, with at least one piezo element and the electrodes being sintered to a mono-block. If applicable, it may be advantageous to electrically connect a piezoelectric transmission and/or reception device with the housing, in order to yield grounding.
Due to the fact that the piezo element and the electrodes are sintered to form a mono-block, they are connected to each other in a fixed manner such that their arrangement in reference to each other is set. It is therefore no longer necessary to provide additional devices or arrangements for centering piezo elements or electrodes in reference to each other. This is advantageous since, in addition to saving components here, an optimal alignment of piezo elements and electrodes in reference to each other is also ensured in this way, which simplifies the application of an optimal electric field at the piezo element, since a holohedral and completely overlapping alignment of electrodes and piezo element is ensured. The sintering process can be performed at low processing temperatures, so that the sintered component therefore shows low internal mechanic stress and thus also high quality and resistance.
For the sintering process preferably the sinter material, particularly sinter paste or sinter film on a silver base, is used with nano-scaled silver particles showing a size from 10 nm to 15 μm.
Another simplified arrangement can be achieved when the mono-block additionally comprises isolation elements. When the isolation elements arranged at the top and the bottom and provided with appropriate isolation are also sintered with the electrodes and at least one piezo element to form a mono-block, this way, a compact and uniformly handled arrangement is created.
In a first embodiment, the piezoelectric transmission and/or reception device comprises a number of n-piezo elements and n+1 electrodes, arranged alternating and sintered to form a mono-block.
In a second embodiment, the piezoelectric transmission and/or reception device comprises a transmission device and a reception device, which comprise respectively n-piezo elements and n+1 electrodes, arranged alternating, with the transmission device and the reception device being electrically isolated from each other by a separating ceramic and all components are sintered to form a mono-block.
In order to ensure optimal transmission of oscillations generated via the piezoelectric transmission and/or reception device upon other elements or oscillations of other elements upon the transmission and/or reception device, the mono-block may comprise additionally a pressure part, preferably made from a metallic or ceramic material. For this purpose, the pressure part can be embodied for example conically tapering starting with a diameter of the mono-block, such that a punctual or linear coupling or decoupling of oscillations is possible.
In order to allow using the here described piezoelectric transmission and/or reception device in already existing devices with a centrally arranged bolt, it may be advantageous for the piezo elements and the electrodes, and preferably the isolation elements and the pressure part, to be embodied in an annular fashion.
In order to yield higher forces of the piezoelectric transmission and/or reception devices, here a maximum surface of the piezo elements is required.
This can be achieved in a particularly easy fashion when the piezo elements and the electrodes are formed as circular disks.
Due to the fact that additional centering elements, such as a centrally arranged bolt and/or a sheath covering the components of the piezoelectric transmission and/or reception device can be waived, it is also possible to utilize the structural space available almost in its entirety in the radial direction so that a greater area is available to generate a piezoelectric effect and thus a stronger force can develop by the piezoelectric transmission and/or reception device.
In an advantageous embodiment, the piezo elements show a thickness of less than 0.1 mm, preferably less than 0.5 mm. Due to the fact that the piezo elements are sintered with the other components of the piezoelectric transmission and/or reception device to form a mono-block, it is possible to embody them with a reduced thickness since mechanic influences upon the piezo elements are here also avoided. In particular, the uneven surface characteristics of the piezo elements, the electrodes, or the ceramic elements used for isolation, are compensated by the sinter material used for the production here, so that additionally any mechanic influences upon the piezo elements are minimized. Due to the fact that that piezo elements can be embodied with a reduced thickness, with identical operating voltages of the piezoelectric transmission and/or reception device a higher electric field develops the piezo elements, allowing to utilize in the piezoelectric effect to a considerably better extent.
By the use of sinter material, particularly a sinter paste or sinter film when sintering the piezoelectric transmission and/or reception device, it is further possible to use piezo elements and/or the electrodes and/or the isolation elements and/or the separating ceramic with a greater average surface roughness of more than RZ (roughness grade number) 6.3, preferably more than RZ 16. This way it is possible to produce the piezo elements particularly at considerably reduced costs, so that the costs for the sintering process can be compensated entirely or at least partially.
The averaged surface roughness can particularly amount for the piezo elements to more than 6.3, for the isolation elements more than 4, and for the metallic parts more than 16.
Particularly low processing temperatures can be yielded for the production process of the mono-block when the mono-block is produced with a silver-sintering method. In such a silver-sintering method, preferably sinter paste or sinter film with nano-scaled silver is used, since they allow processing temperatures and pressures for the sintering method, which are considerably below the Curie-temperature of approx. 350° C. of the piezo elements used.
The piezoelectric transmission and/or reception device of the present invention can be used in a particularly beneficial fashion in a vibration sensor with a diaphragm set to oscillate, a tension device for stressing the piezoelectric transmission and/or reception device towards the diaphragm such that oscillations of the transmission and/or reception device are transferred to the diaphragm and oscillations of the diaphragm to the transmission and/or reception device.
The method according to the invention for the production of a piezoelectric transmission and/or reception device comprises the following steps:
providing at least one piezo element, at least two electrodes for contacting the piezo element, as well as at least two isolation elements for the isolation at the top and the bottom,
coating with a sinter material on a silver base at least the piezo element on its contacting sides as well as the electrodes on their side facing the piezo element in the finished state of the arrangement,
arranging electrodes and piezo elements in an aligned fashion in a stack,
sintering the stack for a predetermined sinter period at a defined sinter temperature to form a mono-block.
The method can be implemented in a particularly simple fashion when the coating process comprises the applying of the sinter material via template printing, a dispenser or serigraphy, or the application of a sinter film. The coating may further include a drying step after the application of the sinter material, particularly in the form of sinter paste, with this occurring in a drying kiln, for example.
Preferably a sinter material with silver particles showing a size from approx. 100 nm to approx. 500 nm is used for the process. By using sinter material with nano-scale silver, the processing temperature can be lowered considerably so that temperatures of less than 300° C., preferably less than 280° C., further preferred from 200° C. to 250° C. can be yielded.
These temperatures are particularly far below the Curie-temperature of commonly used piezo elements, so that their piezoelectric features and their polarization is preserved and thus a renewed polarization of the piezo elements can be avoided.
Alternatively, there are sintering films, which render the application of a paste unnecessary.
With the lower temperature, the present method allows to reduce mechanic stress between the individual components of the piezoelectric transmission and/or reception device.
Further, when using a sinter paste with nano-scaled silver, here the sintering can occur at a pressure of less than 20 MPa, preferably at 10 MPa, further preferred at atmospheric pressures. This way, the equipment required for the sintering process can be a lot less expensive and costs can be saved.
In particular, the sintering process can occur at ambient pressure and preferably at ambient air.
The piezoelectric transmission and/or reception device 1 according to
The transmission device 10 and the reception device 11 are each embodied with a piezo element 3.1, 3.2, each electrically contacted via electrodes 5.1, 5.2; 5.3, 5.4. In the embodiment shown in
All above-described components are sintered via a sintering process based on a sinter paste with nano-scaled silver to form a mono-block. This allows, in particular, that the piezo elements 3.1, 3.2 can be formed with a thickness d of less than 1.0 mm, since due to the embodiment of the piezoelectric transmission and/or reception device 1 as a mono-block as well as the sinter paste used for the sintering process mechanic influences upon the piezo elements 3.1, 3.2 can be largely avoided and uneven surface characteristics, which may lead to negative mechanic influences upon the piezo elements 3.1, 3.2, are compensated by the sinter paste.
Alternatively, a sinter film may also be used with respective characteristics.
The piezoelectric transmission and/or reception device 1 in the exemplary embodiment shown in
The sinter layer 16 is here formed by the residue of the sinter paste and generates a mechanical as well as conductive connection between the electrodes 5.1, 5.2; 5.3, 5.4 and the piezo elements 3.1, 3.2 and/or a mechanic connection to the separating ceramic 13 and the isolation elements 7.1, 7.2
For the production of the piezoelectric transmission and/or reception device, the individual components of the piezoelectric transmission and/or reception device 1, as initially shown in
Alternatively, silver-sinter films may also be used.
Subsequently, the components are subjected to a drying step (402.2), then arranged in reference to each other in a centered fashion in a stack (403), and sintered at a temperature of 250° C. and a pressure of 10 to 20 MPa for 1 to 3 minutes to form a mono-block (404).
When using a sinter film here a drying step is mandatory.
In a cross-section,
As discernible from
At the front, a mechanic vibrator 88 is arranged at the diaphragm 90, which vibrates like a tuning fork depending on the thickness and viscosity of a medium surrounding it at a resonance frequency such that a covering of the mechanic oscillator 88 with a medium can be detected by way of measuring the resonance frequency.
The exemplary embodiment shown in
The clamping device 96 is formed in the exemplary embodiment shown in
This patent application claims priority to International Patent Application PCT/EP2016/078172, filed on Nov. 18, 2016.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/078172 | 11/18/2016 | WO | 00 |
