Vibration sensor

Abstract

The invention relates to a modular system for producing vibration sensors comprising a mechanically vibrating unit (1) and a transducer device (2). The transducer device (2) has a sleeve (9) and multiple components (3, 11) arranged in the sleeve (9). The components (3, 11) are either active components (3) or passive components (11) and have the same base area and the same height. A specifiable number of components (3, 11) can be introduced into the sleeve (9) to form a stack. The invention additionally relates to a vibration sensor.

Description

[0001] Vibration sensor

[0002] The invention relates to a vibration sensor. The vibration sensor is used, for example, to determine and / or monitor a process variable of a medium. The process variable is, for example, the fill level, and the medium is, for example, a liquid, a gas, or a bulk material.

[0003] Vibration sensors are known in the art, for example, in the form of tuning forks or single-rod sensors. Such sensors have a mechanically oscillating unit that is excited to mechanical vibrations by a drive / receiver unit. The vibrations resulting from the interaction with a medium to be measured or monitored are received by the drive / receiver unit and sent for evaluation. For example, a measurement exploits the fact that the vibration frequency or amplitude changes when the mechanically oscillating unit transitions from an uncovered state to one covered by the medium. This allows, for example, the monitoring of the fill level of the medium in a container.

[0004] The drive / receiver unit typically contains a converter device that converts between electrical signals and mechanical vibrations. Piezoelectric elements are often used for this purpose. These elements have a polarized ceramic and at least one electrode applied to one end for electrical contact. Electrical connections of the electrodes are shown, for example, in US Pat. No. 3,495,102 A. If the mechanical force to be generated is to be increased, it is known to arrange several piezoelectric elements one above the other in a stack, see, for example, EP 0 875 741 A1. In this case, one part of the piezoelectric elements serves as the drive unit and another part as the receiver unit. However, it is also known that the piezoelectric elements serve both to drive and to receive vibrations. It is also known to arrange such stacks in sleeves, see, for example,WO 01 / 66269 A1, US 2010 / 0327700 A1, DE102019120685, EP 1 134 038 A1 or DE 44 29 236 A1.

[0005] This allows vibration sensors to be produced with different specifications in terms of performance and internal design, each with its own unique features. This diversity leads to different manufacturing processes and necessitates the inventory of different components.

[0006] The invention is based on the object of simplifying the production of different types of vibration sensors.

[0007] The object is achieved by a modular system for producing vibration sensors, wherein each vibration sensor has a mechanically oscillatable unit and a transducer device, wherein the transducer device excites the mechanically oscillatable unit to mechanical vibrations and / or receives mechanical vibrations from the mechanically oscillatable unit, wherein the transducer device has at least one sleeve and a plurality of components, wherein the components are either active components or passive components, wherein the active components are piezo elements, wherein the passive components are insulating disks or electrically conductive intermediate elements, wherein the components are arranged in the sleeve, wherein the components have a common base area and a common height, and wherein the sleeve is designed such thatthat a predefined number of components can be stacked in the sleeve.

[0008] The problem is thus solved by a modular system (an alternative name is: building block) through which different vibration sensors can be created. The vibration sensors each have a mechanically oscillating unit and a transducer device. The mechanically oscillating unit is, for example, a tuning fork, a single rod, or a diaphragm. The transducer device serves to excite the mechanically oscillating unit to mechanical vibrations and / or to receive mechanical vibrations from the mechanically oscillating unit. The transducer device preferably converts electrical signals into mechanical vibrations and / or mechanical vibrations into electrical signals. The transducer device has at least one sleeve and several components arranged in the sleeve.The components are characterized by having a common base area and a common height (alternatively: thickness). The components essentially have the same base area and height. Therefore, the components are freely interchangeable in terms of their geometry. In terms of their properties and / or function, the components preferably belong to different groups. The sleeve allows a predefined number of components to be inserted into it to form a stack of components.

[0009] Two different groups of components are used. The distinction between active and passive refers to the primary function of the transducer device, i.e., generating or receiving mechanical vibrations. Active components are the familiar piezo elements, and passive components are insulating discs. Other passive components include, for example, electrically conductive intermediate elements. Since the components all have the same external dimensions, different stacks of components can be created in the sleeves. The electrically conductive intermediate elements ensure the electrical connection between the piezo elements.

[0010] The components are preferably designed as circular discs.

[0011] One embodiment provides for a plurality of piezo elements, for at least one insulation disk being arranged in the stack between two piezo elements, and for each insulation disk to delimit the stack at the top and bottom. In this embodiment, the piezo elements in the stack are electrically and thus functionally separated from one another by an insulation disk. Therefore, one part of the piezo elements serves as an excitation device and the other part serves as a receiving device. An alternative embodiment consists in the provision of a plurality of piezo elements, for only two piezo elements in the stack to have insulation disks arranged laterally adjacent thereto, and for each insulation disk to delimit the stack at the top and bottom. In this embodiment, a stack of components is produced, each of which is delimited by two insulation disks. There are no insulation disks within the stack.The pizo elements are therefore all coupled together so that they also perform both functions of the transducer device: excitation and reception of mechanical vibrations.

[0012] One embodiment provides that the transducer device has at least one contacting electrode, that the sleeve has at least one window, that the contacting electrode is electrically conductively contacted with at least one piezoelectric element, and that the contacting electrode is led out of the sleeve via the window. In this embodiment, the sleeve has at least one window-shaped recess on its casing to enable electrical contact to the outside.

[0013] One design is for the sleeve to be thermally insulating. For example, in high-temperature applications, it is important that the piezo elements are protected from the high temperatures to prevent loss of polarization above the Curie temperature.

[0014] Alternatively, or additionally, the sleeve can be designed in multiple parts. This also simplifies production, especially since it makes it easier to insert the component stack into the sleeve.

[0015] One embodiment provides that the converter device has a pressure screw and a coupling element, that the stack is arranged between the pressure screw and the coupling element, and that the sleeve is connected - preferably reversibly - to the pressure screw and / or the coupling element. The pressure screw serves to ensure sufficiently close mechanical and, in one embodiment, also electrical coupling between the individual components. To ensure sufficient contact, one embodiment provides that the components in the sleeve are pressed together by a mechanical force. This means that, for example, no solder or adhesive connection is required. This avoids, among other things, the disadvantage of adhesive connections, which is that settling effects can occur which lead to a reduction in the preload or preload force and can therefore change the rigidity of the overall system.

[0016] One design involves the components being arranged in the sleeve in a rotationally fixed manner via a recess and a locking lug. This design provides anti-twist protection, which primarily focuses on ease of manufacture. In one design, the recess is present in the components, and the sleeve has the locking lug. In an alternative design, the recesses are located in the sleeve, and the piezo elements each have a locking lug.

[0017] According to one embodiment, the sleeve has at least one radially inwardly projecting support at its end. This support, which can also be referred to as a shoulder, serves as protection against the piezo element or other components arranged in the stack falling out of the sleeve, for example, during assembly.

[0018] In one embodiment, the circumferentially interrupted support consists of several circumferentially distributed locking arms.

[0019] In one embodiment, there is a shoulder on the opposite end of the sleeve, which also narrows the diameter compared to the diameter of the interior of the sleeve. In one embodiment, the coupling element is located on this end and has a spherically tapered end and, conversely, an outer diameter that increases towards the inside. The spherical end thus protrudes from the sleeve, while at the same time the coupling element as a whole is held against falling out by the shoulder of the sleeve. In one embodiment, at least one piezo element has two end faces and an outer casing, that an electrode is applied to each end face, and that each electrode is guided from one end face of the two end faces over the outer casing to the other end face of the two end faces. In this embodiment, at least one piezo element has double contact.Each electrode is thus routed from one end face to the other end face. Therefore, both electrodes can be electrically contacted via one of the two end faces.

[0020] Furthermore, the invention achieves the object with a vibration sensor manufactured using the system according to the preceding or following embodiments. The embodiments and explanations also apply accordingly to the vibration sensor, so they will not be repeated here.

[0021] The invention is explained in more detail with reference to the following figures.

[0022] Fig. 1 shows schematically the structure of a vibration sensor,

[0023] Fig. 2 shows a section through a converter device,

[0024] Fig. 3 shows a spatial representation of the converter device of Fig. 2,

[0025] Fig. 4 shows a stack of piezo elements,

[0026] Fig. 5 shows a front side of a piezo element and

[0027] Fig. 6 shows the other end face of the piezo element of Fig. 5.

[0028] Fig. 1 shows a so-called tuning fork as an example of a design of the vibration sensor.

[0029] The mechanically oscillating unit 1 has two so-called fork tines connected to a diaphragm 5. On the opposite side of the diaphragm 5, in a housing 4 (shown here), there is a transducer device 2, which, in the example shown, has several disc-like piezo elements 3 arranged in a stack. The piezo elements 3 are clamped between a pressure screw 6 and a coupling element 7. The coupling element 7 for clamping relative to the diaphragm 5 has the shape of a hemisphere.

[0030] The section in Fig. 2 shows that, in the exemplary embodiment, several piezo elements 3 and three insulation disks 11 are located between the pressure screw 6 and the coupling element 7. The piezo elements 3 are surrounded by a sleeve 9. A contacting electrode 8 extends from a window 10 in the sleeve 9 and is in contact with a piezo element 3 in the stack. The sleeve 9 is attached to the pressure screw 6, for example, via snap hooks.

[0031] Fig. 3 shows that the sleeve 9 is designed in two parts for easy assembly. This can be seen at the front separation point. The two housing halves each have a raised portion at their upper ends for mutual locking.

[0032] The sleeve 9 has several windows 10 for the contacting electrodes 8 (an alternative term is solder lug). On the top side, a locking lug 12 is visible in the sleeve 9, which engages the matching recesses 35 of the piezo elements 3 or the insulation discs (see Fig. 4 - Fig. 6).

[0033] At the upper end of the sleeve 9 is an inwardly projecting shoulder 13, which in this design consists of three individual locking arms (see Fig. 2). The shoulder 13 ensures that the end face of the sleeve 9 has a smaller diameter than the interior of the sleeve 9. Therefore, components located in the sleeve 9 are prevented from falling out. This simplifies manufacturing. On the underside of the sleeve 9 - see Fig. 2 - there is also an inwardly projecting shoulder, which holds the coupling element 7 there.

[0034] During production, for example, the individual components are inserted into one housing half. The other housing half is then applied so that the raised portions engage each other to lock them in place. In the resulting assembled sleeve 9, the locking lugs 12 prevent the components from twisting relative to each other and protect the supports 13 from falling out.

[0035] In an alternative design (not shown), a hinge, e.g., a film hinge, is provided. For assembly, in this variant, the sleeve 9 is opened to accommodate the components. Then, the sleeve 9 is closed again, and a snap-in of the previously mentioned protrusions ensures fixation.

[0036] In Fig. 4, it can be seen on the outer casings 32 of the piezo elements 3 how an electrode 34 extends continuously from bottom to top, thus creating a continuous electrical contact. The insulating disks 11 as the upper and lower ends of the stack, respectively, as well as the insulating disk 11 in the stack, result in a total of two separate stacks of piezo elements 3, which separately serve to excite and receive the mechanical vibrations. It can be seen that only four contacting electrodes 8 are sufficient for this. Furthermore, there are no further electrical connections between the piezo elements 3. On the rear side, the recess 35 can be seen, which engages with the locking lug 12 of the sleeve 9.

[0037] Fig. 5 and Fig. 6 show the two end faces 30, 31 of a piezo element 3. On each of the end faces 30, 31 there is a largely circular electrode 33, 34. Each electrode 33, 34 borders in sections on the edge of the end face 30, 31 in order to be guided in this area to the opposite end face 31, 30. This occurs via the part of the electrode 33, 34 that extends along the outer casing 32 of the piezo element 3. On the respective opposite end faces 31, 30 there is a significantly smaller extension of the electrode 33, 34. The smaller area is possible because the purpose of the recontacting is electrical contact. The electrodes 33, 34 are designed here such that on each end face 30, 31, the two sections for the respective non-contacting from one end face 31 to the other face 31, 30 are opposite each other. List of reference symbols mechanically oscillatable unit

[0038] converter device

[0039] Piezo element

[0040] pressure screw

[0041] coupling element

[0042] Contacting electrode

[0043] sleeve

[0044] Window

[0045] Insulating disc

[0046] locking lug

[0047] Edition

[0048] front side

[0049] front side

[0050] Outer jacket

[0051] electrode

[0052] electrode

[0053] recess

Claims

Patent claims 1. A modular system for producing vibration sensors, each vibration sensor comprising a mechanically oscillatable unit (1) and a transducer device (2), the transducer device (2) exciting the mechanically oscillatable unit (1) to mechanical vibrations and / or receiving mechanical vibrations from the mechanically oscillatable unit (1), the transducer device (2) comprising at least one sleeve (9) and a plurality of components (3, 11), the components (3, 11) being either active components (3) or passive components (11), the active components being piezoelectric elements (3), the passive components being insulating disks (11) or electrically conductive intermediate elements, the components (3, 11) being arranged in the sleeve (9), the components (3, 11) having a common base area and a common height, and the sleeve (9) being configured such thatthat a predeterminable number of components (3, 11) can be introduced into the sleeve (9) to form a stack., 2. System according to claim 1, wherein the converter device (2) has at least one contacting electrode (8), wherein the sleeve (9) has at least one window (10), wherein the contacting electrode (8) is provided with at least one piezo element (3) is electrically conductively contacted, and wherein the contacting electrode (8) protrudes from the sleeve via the window (10) (9) is brought out.

3. System according to claim 1 or 2, wherein the sleeve (9) is designed to be thermally insulating.

4. System according to one of claims 1 to 3, wherein the sleeve (9) is designed in several parts.

5. System according to one of claims 1 to 4, wherein the converter device (2) comprises a pressure screw (6) and a coupling element (7), wherein the stack is arranged between the pressure screw (6) and the coupling element (7), and wherein the sleeve (9) is connected - preferably reversibly - to the pressure screw (6) and / or the coupling element (7).

6. System according to one of claims 1 to 5, wherein the components (3, 11) are arranged in the sleeve (9) via a recess (35) and a locking lug (12) in a rotationally fixed manner.

7. System according to one of claims 1 to 6, wherein the sleeve (9) has at least one radially inwardly projecting support (13) at its end.

8. System according to one of claims 1 to 7, wherein at least one piezo element (3) has two end faces (30, 31) and an outer casing (32), wherein an electrode (33, 34) is applied to each end face (30, 31), and wherein each electrode (33, 34) is guided from one end face (30, 31) of the two end faces (30, 31) via the outer casing (32) to the respective other end face (31, 30) of the two end faces (30, 31).

9. Vibration sensor manufactured with the system according to claims 1 to 8.

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