Vibration sensor

Abstract

The invention relates to a vibration sensor comprising a mechanical vibration unit (1) and a transducer device (2) which mechanically vibrates the mechanical vibration unit (1) and / or receives mechanical vibrations. The transducer arrangement (2) has a piezoelectric element (3) with two end faces (30, 31) and a housing (32). Each end face (30, 31) is provided with an electrode (33, 34) which extends from one end face (30, 31) to the respective other end face (31, 30) via the housing (32).

Description

Technical Field

[0001] This invention relates to a vibration sensor. The vibration sensor is used, for example, to determine and / or monitor process parameters of a medium. These process parameters are, for example, fill levels, and the medium is, for example, a liquid, gas, or bulk material. Background Technology

[0002] Vibration sensors are known in the prior art and are designed, for example, as vibrating forks or single rods. Such sensors have a mechanical vibration unit that is excited by a drive / receiver unit to perform mechanical vibration. The vibrations generated by the interaction with the medium to be measured or monitored are received and transmitted by the drive / receiver unit for evaluation. For example, in the case of measurement, the change in vibration frequency or amplitude is utilized when the mechanical vibration unit transitions from an uncovered state to a state covered by the medium. This allows, for example, monitoring the fill level of the medium in a container.

[0003] A drive / receiver unit typically contains a transducer device that converts between electrical signals and mechanical vibrations. Piezoelectric elements are commonly used for this purpose; these elements have polarized ceramic and at least one electrode applied to an end face for electrical contact. If the mechanical force to be generated is to be increased, it is known to arrange multiple piezoelectric elements on top of each other in a stacked manner. Therefore, for electrical contact, it is necessary to ensure that all elements are in contact individually or at least with each other. This is very complex and expensive.

[0004] Examples of different embodiments of piezoelectric elements are described in the following publications: DE 103 50 086 B4, DE 102019 111 384 B3, DE 10 2016 113 447 A1, DE 16 48 582 A, or EP 0 985 916 A1.

[0005] The present invention is based on the purpose of providing a vibration sensor that is as simple as possible to manufacture in terms of piezoelectric elements. Summary of the Invention

[0006] This objective is achieved by a vibration sensor having a mechanical vibration unit and a transducer device, wherein the transducer device excites the mechanical vibration unit to perform mechanical vibration and / or receives mechanical vibration from the mechanical vibration unit, wherein the transducer device has at least one piezoelectric element, wherein the piezoelectric element has two end faces and a housing, wherein electrodes are applied to each end face, and wherein each electrode is guided from one of the two end faces via the housing to a corresponding other end face of the two end faces.

[0007] The vibration sensor according to the invention comprises a mechanical vibration unit (e.g., in the form of a vibrating fork, a single rod, or a diaphragm) and a transducer device that converts an electrical signal between the mechanical vibration of the mechanical vibration unit and / or vice versa. For this purpose, the transducer device has at least one piezoelectric element. The piezoelectric element has two end faces and a housing. Each end face has an electrode for electrical contact. Furthermore, each electrode is guided via the housing to a corresponding other end face. This means that there are two electrodes on each end face, which are preferably electrically insulated from each other. The electrodes themselves extend from one end face across the housing to the other end face. This provides the advantage that both sides of the piezoelectric element can be contacted via each end face. Therefore, it is not necessary to add a single contact to each end face; instead, extending two contacts to one end face is sufficient. This significantly simplifies the effort required for contact.

[0008] Furthermore, this makes it easier to arrange multiple piezoelectric elements in a stacked manner and make them electrically contacted. Finally, with a suitable arrangement and design, the contacts of the different piezoelectric elements are also opposite each other. Therefore, a design is provided in which the transducer device has at least two piezoelectric elements arranged in a stacked manner on top of each other, and the at least two piezoelectric elements are in direct electrical contact with each other. The electrodes must have a geometry that allows the mechanical contact surface to be large enough for electrical contact. Preferably, the piezoelectric elements have the same design.

[0009] To ensure adequate contact, one embodiment specifies that the piezoelectric elements are pressed together by mechanical force. Therefore, for example, solder or adhesive bonding is not required. In particular, this avoids the disadvantages of adhesive bonding, namely the potential for solidification effects that lead to a reduction in preload or preload force, and thus potentially alter the stiffness of the entire system.

[0010] One embodiment includes a transducer device having at least one contact electrode, which is in conductive contact with at least one piezoelectric element. Electrical signals can be applied to or received from the transducer device via the contact electrode (another name for, for example, a solder pad).

[0011] One design specifies that the transducer device has a sleeve, and the at least one piezoelectric element is arranged within the sleeve. The sleeve encloses the transducer device, and in one design, the sleeve also serves as thermal insulation against potentially higher applied temperatures by selecting a suitable material.

[0012] One embodiment involves the at least one piezoelectric element being arranged in the sleeve in a non-rotatable manner via a recess and a latching lug. Non-rotatable positioning is particularly advantageous when multiple piezoelectric elements are in electrical contact with each other solely by mechanical force via their electrodes. In this case, it is important to ensure the correct orientation of the electrodes or piezoelectric elements relative to each other to achieve optimal overlap between the electrodes of the individual piezoelectric elements located on top of each other.

[0013] According to one embodiment, the sleeve has at least one radially inwardly projecting support at its end. The support, also referred to as a step, serves as protection against the piezoelectric element or other components arranged in the stack, for example, falling out of the sleeve during assembly.

[0014] In one design, the completely discontinuous support consists of a plurality of latching arms distributed on the periphery.

[0015] In one design, a step is present at the opposite ends of the sleeve, which narrows the diameter compared to the inner diameter of the sleeve. In another design, the connecting element is located at this end and has a spherical tapered end, and therefore, conversely, has an inwardly increasing outer diameter. This means that the spherical end protrudes from the sleeve, while the connecting element as a whole remains held in place by the step of the sleeve.

[0016] In one embodiment, the piezoelectric element is designed as a disk. Attached Figure Description

[0017] The invention will be explained in more detail with reference to the following figures.

[0018] Figure 1 The structure of the vibration sensor is schematically shown. Figure 2 A cross-section through the transducer device is shown. Figure 3 It shows Figure 2 Spatial representation of the transducer device, Figure 4 The stacking of piezoelectric elements is shown. Figure 5 The end face of the piezoelectric element is shown, and Figure 6 It shows Figure 5 The other end face of the piezoelectric element. Detailed Implementation

[0019] Figure 1 An example of a so-called vibration fork, designed as a vibration sensor, is shown.

[0020] The mechanical vibration unit 1 has two so-called forked teeth connected to the membrane 5. In the housing 4 indicated herein, on the opposite side of the membrane 5, there is a transducer device 2, which, in the indicated example, has multiple piezoelectric elements 3 arranged in a stacked manner in a disc-like pattern. The piezoelectric elements 3 are clamped between a pressure screw 6 and a connecting element 7. The connecting element 7 for clamping the membrane 5 has a hemispherical shape.

[0021] exist Figure 2 As can be seen in the cross-sectional view, in the exemplary embodiment, a plurality of piezoelectric elements 3 and three insulating discs 11 are positioned between the pressure screw 6 and the connecting element 7. The piezoelectric elements 3 are surrounded by a sleeve 9. A contact electrode 8 extends from a window 10 in the sleeve 9 and contacts the piezoelectric elements 3 in the stack. For example, the sleeve 9 is attached to the pressure screw 6 via a snap hook.

[0022] Figure 3 The sleeve 9 is shown to be designed in two parts for easy assembly. This can be seen at the front separation point. Each of the two housing halves has a raised section on its upper end for interlocking.

[0023] The sleeve 9 has multiple windows 10 (alternative name: welding lugs) for contacting the electrode 8. On the upper side, latching lugs 12 are visible in the sleeve 9 and engage in corresponding recesses 35 of the piezoelectric element 3 or insulating disc (see...). Figures 4 to 6 ).

[0024] At the upper end of sleeve 9, there is an inwardly protruding step 13, which in this design consists of three separate latching arms (see...). Figure 2 Step 13 ensures that the end face of sleeve 9 has a smaller diameter than the inner region of sleeve 9. This prevents components located within sleeve 9 from falling out. This simplifies manufacturing. See also the underside of sleeve 9. Figure 2 There is also an inwardly protruding step that holds the connecting element 7 in place.

[0025] For example, during manufacturing, the individual components are placed in one half of the housing. Then, the other half of the housing is attached, such that the raised sections lock into each other. In the resulting assembled sleeve 9, the latch lug 12 prevents the components from twisting relative to each other and protects the support 13 from falling out.

[0026] In an alternative design (not shown), a hinge, such as a membrane hinge, is present. For assembly, in this variant, sleeve 9 is opened to accommodate the component. Sleeve 9 is then closed, and a secure fit is secured, for example, by snapping the aforementioned raised portion into place.

[0027] exist Figure 4In the image, on the housing 32 of the piezoelectric element 3, one can see how the electrode 34 extends continuously from the bottom to the top, thus resulting in continuous electrical contact. With the insulating disk 11 serving as the upper and lower terminals of this stack, and with the insulating disk 11 within this stack, a total of two separate stacks of piezoelectric elements 3 are obtained, one for exciting mechanical vibration and the other for receiving mechanical vibration. It can be seen that only four contact electrodes 8 are sufficient. Furthermore, there are no other electrical connecting elements between the piezoelectric elements 3. On the opposite side, a recess 35 can be seen, which engages in the latch lug 12 of the sleeve 9.

[0028] Figure 5 and Figure 6 Two end faces 30 and 31 of the piezoelectric element 3 are shown. On end faces 30 and 31, there are generally circular electrodes 33 and 34. Each electrode 33 and 34 partially abuts the edge of end faces 30 and 31 so as to be guided in that region to the opposite end face 31 and 30. This occurs via the portion of electrodes 33 and 34 extending along the housing 32 of the piezoelectric element 3. On the opposite end faces 31 and 30, there are significantly smaller extensions of electrodes 33 and 34. The smaller surface area is possible because the purpose of re-contact is electrical contact. Electrodes 33 and 34 are designed here such that on each end face 30 and 31, the two corresponding uncontacted portions for moving from one end face 30 to the other end face 31 are opposite to each other.

[0029] List of reference numerals

[0030] 1 Mechanical Vibration Unit

[0031] 2. Transducer device

[0032] 3. Piezoelectric elements

[0033] 4. Shell

[0034] 5. Membrane

[0035] 6 Pressure screws

[0036] 7 Connecting elements

[0037] 8. Contact Electrode

[0038] 9 sleeves

[0039] 10 windows

[0040] 11 Insulating disc

[0041] 12 latch lugs

[0042] 13 Support components

[0043] 30 End face of piezoelectric element

[0044] 31 End face of piezoelectric element

[0045] 32. Housing of piezoelectric element

[0046] 33 Electrodes

[0047] 34 electrodes

[0048] 35 recess

Claims

1. A vibration sensor, It has a mechanical vibration unit (1) and a transducer device (2). in, The transducer device (2) excites the mechanical vibration unit (1) to perform mechanical vibration and / or receives mechanical vibration from the mechanical vibration unit (1). The transducer device (2) has at least one piezoelectric element (3). The at least one piezoelectric element (3) has two end faces (30, 31) and a housing (32). Electrodes (33, 34) are applied to each end face (30, 31), and Each electrode (33, 34) is guided from one of the two end faces (30, 31) via the housing (32) to the corresponding other end face (31, 30) of the two end faces (30, 31).

2. The vibration sensor according to claim 1, in, The transducer device (2) has at least two piezoelectric elements (3). In this arrangement, at least two piezoelectric elements (3) are stacked on top of each other, and In this process, the at least two piezoelectric elements (3) are made to be in direct electrical contact with each other.

3. The vibration sensor according to claim 1 or 2, in, The transducer device (2) has at least one contact electrode (8). The contact electrode (8) is made to be in conductive contact with at least one piezoelectric element (3).

4. The vibration sensor according to any one of claims 1 to 3, in, The transducer device (2) has a sleeve (9), and The at least one piezoelectric element (3) is arranged in the sleeve (9).

5. The vibration sensor according to claim 4, in, The at least one piezoelectric element (3) is arranged in the sleeve (9) in a non-rotatable manner via a recess (35) and a latch lug (12).

6. The vibration sensor according to claim 4 or 5, in, The sleeve (9) has at least one radially inwardly protruding support (13) at its end.

7. The vibration sensor according to any one of claims 1 to 6, in, The piezoelectric element (3) is designed as a disk.

Images