Sensor device for detecting filling level and / or quality of fluid and method for manufacturing the same

Abstract

The present invention relates to a fluid sensor device (100) and a method for producing a fluid sensor device (100), the fluid sensor device being arranged for detecting the filling level (10) and / or the quality of a fluid (12) in a fluid container (14). The fluid sensor device (100) according to the invention comprises a circuit board (120) having at least one recess (130) extending at least partially into the circuit board along the thickness direction of the circuit board (120). The circuit board (120) has at least one fastening region (122, 124, 126, 128). Furthermore, the fluid sensor device (100) includes an ultrasonic transducer (110), which is mounted on at least one fixing area (122, 124, 126, 128) of the circuit board (120) in such a way that the ultrasonic transducer (110) extends at least partially over the recess (130), and the fluid sensor device (100) includes a housing (140), which at least partially surrounds the circuit board (120) and the ultrasonic transducer (110) in such a way that the housing area (142) is at least partially arranged in the recess (130).

Description

[0001] The present invention relates to a fluid sensor device for detecting the fill level and / or quality of a fluid, preferably oil, an aqueous urea solution or water, and to a method for producing such a fluid sensor device.

[0002] To determine the height of the fluid surface in a fluid container, an acoustic measuring device can be used, for example. The acoustic transducer of the acoustic measuring device can function both as a sound generator and as a sound receiver. To determine the height of the fluid surface in the fluid container, a sound pulse or sound signal can be output into the fluid to be measured using the acoustic transducer. The sound pulse or sound signal can be reflected from the surface or interface of the fluid to another medium. The propagation time of the sound pulse or sound signal can be used to infer the height of the fluid surface in the fluid container and, therefore, the fluid filling level. The frequency of the sound signal preferably lies in the ultrasonic range.

[0003] In the prior art, it is known to manufacture fluid sensor devices as compact electronic components. For example, a printed circuit board can be equipped with all electronic components, in particular also with at least one ultrasonic transducer. The printed circuit board is then completely extruded with plastic to form a housing for the electronics and protect the electronic components from environmental influences such as moisture. It is known to solder the ultrasonic transducer fully to the surface of the printed circuit board and thereby electrically connect it to the printed conductors on the printed circuit board.

[0004] DE 10 2016 205 240 B3 discloses a method for producing an ultrasonic sensor and an ultrasonic sensor configured to detect the fill level and / or temperature of a fluid in an internal combustion engine. The disclosed method includes providing the electronics of the ultrasonic sensor, arranging the electronics of the ultrasonic sensor in an injection mold, and extruding the electronics with a plastic material used to form a housing for the electronics. The housing includes at least one functional section configured to perform a predetermined function.

[0005] Further ultrasonic sensor devices are known from CN 105 596 027 A, US Pat. No. 7,471,034 B2, CN 209 296 914 U and US Pat. No. 10,433,063 B2.

[0006] Full-surface soldering of an ultrasonic sensor to a printed circuit board can result in the formation of air pockets or defects in the solder layer between the ultrasonic transducer and the printed circuit board, even if the soldering process is performed as a vacuum soldering process. These air pockets or defects are very disruptive to the acoustic properties of the sound transducer, as they can represent random disturbances in the vibration, radiation, and expiration characteristics of the sound transducer. Furthermore, during the soldering process, the sound transducer can tend to float above the solder material and move laterally in an unpredictable manner, which can limit the positioning accuracy of the sound transducer on the printed circuit board and, therefore, the measurement accuracy of the entire fluid sensor device. This effect can tend to become even more severe if a smaller, single-point grid is chosen instead of a flat solder application. Another negative effect is that fluctuations in the thickness of the printed circuit board can lead to different acoustic properties of the sound transducer. Similar problems with air pockets or defects arise if the sound transducer is fixed to the printed circuit board using a (preferably conductive) adhesive instead of solder.

[0007] Therefore, the object of the present invention is to provide a fluid sensor device and a method for producing the fluid sensor device, with which the acoustic transducer can be precisely positioned on the printed circuit board and the measuring accuracy of the fluid sensor device is substantially improved.

[0008] This object is achieved by a fluid sensor device according to independent claim 1 and a method for producing a fluid sensor device according to independent claim 12. Preferred embodiments are described in the dependent claims.

[0009] The present invention is based essentially on the idea of ​​structuring or completely penetrating the printed circuit board of the fluid sensor device in the area of ​​the ultrasonic transducer so that the ultrasonic transducer is almost completely enclosed during the embedding process, for example by plastic molding or injection molding, and the acoustic properties are not adversely affected by the solder or adhesive layer between the acoustic transducer and the printed circuit board. Furthermore, measurement accuracy can be improved by providing only a few solder points, because the suspension of the ultrasonic transducer on the solder layer can be at least partially reduced, and the surface tension of the solder can hold the ultrasonic transducer in the desired position. Similar advantages arise when the ultrasonic transducer is (preferably conductively) bonded to a few fixing points.

[0010] According to a first aspect of the present invention, a fluid sensor device for detecting the fill level and / or quality of a fluid in a fluid container is disclosed. The fluid sensor device according to the present invention comprises a circuit board having at least one recess that extends at least partially into the interior of the circuit board along its thickness. The circuit board includes at least one fastening region that is preferably arranged in the immediate vicinity of or adjacent to the recess. Furthermore, the fluid sensor device according to the present invention comprises an ultrasonic transducer that is mounted on the at least one fastening region of the circuit board such that it extends at least partially over the recess, and a housing that at least partially surrounds the circuit board and the ultrasonic transducer such that the housing region is at least partially arranged in the recess.

[0011] The ultrasonic transducer is connected to the circuit board only via a (relatively small) fastening area, and the housing area is at least partially arranged in the recess, thereby at least partially overcoming the aspects identified above as disadvantages. In particular, air locks or defects that may occur during the soldering or gluing process can be largely avoided due to the complete contact of the housing with the ultrasonic sensor. Furthermore, better damping of the ultrasonic transducer's decay time can be achieved, and a smaller dispersion in the characteristics of different fluid sensor devices can be achieved. Furthermore, better positioning of the ultrasonic transducer during the soldering or gluing process is possible, as the ultrasonic transducer is fixed to the circuit board only via the at least small fastening area and no longer fully fixed to the circuit board as is known from the prior art.

[0012] In a preferred embodiment of the fluid sensor device according to the present invention, the recess extends completely through the circuit board in the thickness direction of the circuit board.

[0013] In another preferred design of the fluid sensor device, the housing area arranged in the recess has a concave section on the side facing away from the ultrasonic transducer, which is constructed to: divert the ultrasonic signal sent by the ultrasonic transducer at least partially away from the ultrasonic transducer, or reflect it back to the ultrasonic transducer in a defined manner, or transmit it to the environment.

[0014] For a completely penetrated printed circuit board, the rear side of the housing, or the rear side of the housing region located in the recess, can be structured in such a way as to selectively improve the acoustic properties of the ultrasonic transducer. For example, a conical recessed region can be hollowed out at this location, extending at least partially into the recess and configured to divert the ultrasonic signal emitted by the ultrasonic transducer so that it is no longer reflected back to the ultrasonic transducer as an interference signal.

[0015] Advantageously, the depression is formed by at least one drill hole. It can be preferred that the depression is formed by four drill holes having parallel drill axes, wherein the drill axes of three of the drill holes are arranged symmetrically relative to the drill axis of another drill hole in such a way that they lie at the corners of a triangle, preferably an equilateral triangle, which lies in a plane perpendicular to the drill axes, and the drill holes at least partially overlap one another, thereby forming an uninterrupted depression.

[0016] This symmetrically formed recess provides three distributed fixing areas, which are arranged symmetrically with respect to the central bore. This symmetry has the positive effect that the surface tension of the solder material ensures good positioning of the ultrasonic transducer when soldering it to the circuit board. Furthermore, it is desirable to maintain a sufficiently large area below the ultrasonic transducer to allow sufficient placement of housing material below the ultrasonic transducer and within the recess.

[0017] In another preferred embodiment of the fluid sensor device according to the present invention, the four boreholes each have the same borehole diameter, and the spacing of the borehole axes of the three outer boreholes relative to the borehole axis of the center borehole corresponds to approximately 0.2 to 0.9 times the borehole diameter. This ensures that the symmetrical arrangement of the borehole axes relative to one another results in a sufficiently large overlap and an uninterrupted recess. Alternatively, the boreholes can have different borehole diameters. Thus, the preferred embodiments share the at least partial overlap between the boreholes and the resulting continuous, uninterrupted recess.

[0018] According to another preferred design of the fluid sensor device, the recess is formed by five boreholes having essentially parallel drilling axes, wherein the drilling axes of four of the boreholes are arranged relative to the drilling axis of another borehole in such a way that the drilling axes are located at the corners of a quadrangle, preferably a rectangle, and even more preferably a square, the quadrangle being in a plane perpendicular to the drilling axes, and the boreholes at least partially overlap with each other.

[0019] It is preferred that the five boreholes each have the same borehole diameter and that the spacing of the borehole axes of the four outer boreholes relative to the borehole axis of the middle borehole is approximately equivalent to 0.2 to 0.9 times the borehole diameter. Alternatively, the boreholes have different borehole diameters.

[0020] According to an advantageous embodiment of the fluid sensor device according to the present invention, the recess is formed at least partially by milling. In this case, it can be preferred that the recess is formed by three linear milling cuts, which extend symmetrically with respect to one another at an angle of approximately 120° starting from a common point.

[0021] Alternatively, the recess is a cross-shaped recess. That is, the recess is formed by two straight milling sections, which preferably intersect each other at a midpoint. Preferably, the two straight milling sections are substantially perpendicular to each other and form a symmetrical cross.

[0022] According to another aspect of the present invention, a method for manufacturing a fluid sensor device configured to detect the fill level and / or quality of a fluid in a fluid container is disclosed. The method includes providing a circuit board having a recess that extends at least partially into the interior of the circuit board along its thickness; attaching at least one ultrasonic transducer to the circuit board such that the ultrasonic transducer extends at least partially over the recess; and at least partially extruding the circuit board and ultrasonic transducer with a plastic material used to form a housing such that the housing is at least partially disposed within the recess.

[0023] In this case, the recess preferably extends completely through the printed circuit board in the thickness direction of the printed circuit board.

[0024] In another preferred embodiment of the method according to the invention, the recess is formed by at least one drilled hole and / or at least one milled portion.

[0025] Preferably, placing the at least one ultrasonic transducer on the circuit board includes positioning the ultrasonic transducer at a predetermined position on the circuit board, securing the ultrasonic transducer at the predetermined position using a positioning mechanism, and securing and electrically connecting the ultrasonic transducer to the circuit board. The positioning mechanism can be a template or a clip.

[0026] Other objects and features of the present invention will become clear to those skilled in the art through practice of the present invention and observation of the accompanying drawings, in which:

[0027] Figure 1 A schematic diagram of a fluid sensor device for determining a fill level and / or quality of a fluid in a fluid container is shown;

[0028] Figure 2 Shown in Figure 1 A schematic top view of a first embodiment of a circuit board of a fluid sensor device shown in FIG;

[0029] Figure 3 Shown in Figure 1 A schematic top view of another embodiment of a circuit board of a fluid sensor device shown in FIG.

[0030] Figure 4 Shown in Figure 1 A schematic top view of another embodiment of a circuit board of a fluid sensor device shown in FIG.

[0031] Figure 5 Shown in Figure 1 A schematic top view of another embodiment of a circuit board of a fluid sensor device shown in FIG.

[0032] Figure 6 The circuit board of the fluid sensor device according to the present invention is shown along the Figure 3 A sectional view along line AA of FIG. 1 together with a first possible design of a housing for a fluid sensor device;

[0033] Figure 7 The circuit board of the fluid sensor device according to the present invention is shown along the Figure 3 A sectional view along line AA of FIG. 1 together with another possible design of a housing for a fluid sensor device;

[0034] Figure 8 The circuit board of the fluid sensor device according to the present invention is shown along the Figure 3 A sectional view along line AA of FIG. 1 together with another possible design of a housing for a fluid sensor device;

[0035] Figure 9 An exemplary flow chart of a method according to the present invention for producing a fluid sensor device according to the present invention is shown.

[0036] Elements of the same structure or function are provided with the same reference signs throughout the figures.

[0037] Within the scope of this disclosure, the term "fluid quality" describes parameters that characterize a fluid. Parameters that characterize fluid quality include, for example, the velocity of sound of the fluid, the density of the fluid (from which the chemical composition of the fluid can be derived), the electrical properties of the fluid, and the damping properties of the fluid. For example, in the case of an aqueous urea solution, such as urea, the urea content in the water can be estimated by determining the temperature-dependent velocity of sound of the aqueous urea solution.

[0038] In order to determine the fill level 10 of the fluid 12 in the fluid container 14, a fluid sensor device 100 is provided, which is arranged on the bottom section 16 of the fluid container 14. Figure 1 As shown in FIG, the fluid sensor device 100 can be mounted on the fluid container 14 from the outside in such a way that the ultrasonic signal emitted by the fluid sensor device 100 is coupled into the fluid 12 through the wall of the bottom section 16. As an alternative, it is also possible to provide an opening in the bottom section 16 of the fluid container 14 (in FIG. Figure 1 ), the opening is closed in a medium-tight manner by the fluid sensor device 100 , which is arranged on the bottom section 16 from the outside, so that the ultrasonic signal emitted by the fluid sensor device 100 can be directly coupled into the fluid 12 .

[0039] For example, the housing wall of fluid container 14 is formed from plastic, such as high-density polyethylene (HDPE). Fluid sensor device 100 can be bonded to the housing wall of fluid container 14 or mechanically pressed onto the housing wall with another intermediate layer to compensate for unevenness or roughness.

[0040] Furthermore, a control unit 20 is provided, which is connected to the fluid sensor device 100 and is designed to control the fluid sensor device 100 for emitting acoustic signals and to evaluate the signals received by the fluid sensor device 100 in order to determine the filling level and / or quality of the fluid 12 .

[0041] The filling level 10 of the fluid 12 is defined here as the “distance of the fluid surface 13 from the bottom section 3 ”, which is measured in the neutral position of the fluid container 14 , i.e. when there is no tilted position of the fluid container 14 and the fluid surface 13 is essentially parallel to the bottom section 16 .

[0042] In additional reference Figure 2In the case of the fluid sensor device 100, the fluid sensor device 100 includes at least one ultrasonic transducer (for example, see Figure 2 ), the ultrasonic transducer is arranged on the circuit board 120 and is configured to transmit and receive ultrasonic signals. The ultrasonic transducer 110 can be configured to transmit ultrasonic signals with different sound frequencies into the fluid 12 and receive them as reflected signals through different controls. For example, Figure 1 In FIG, the acoustic signal emitted by ultrasonic transducer 110 and received again for detecting fill level 10 is indicated by arrow 112 .

[0043] Furthermore, at least one reference element 30 is arranged in the fluid 12 (see Figure 1 ), which is preferably formed of a metal material. The reference element 30 is of course optional and is arranged at a predetermined constant distance from another ultrasonic transducer (not explicitly shown) arranged on the circuit board 120 and is configured to reflect at least a portion of the ultrasonic signal indicated by the arrow 114. As shown in Figure 1 As shown in , it may be preferred that the reference element 30 inside the fluid container 14 is mechanically coupled to the bottom section 16. It should be noted here that only the ultrasonic transducer 110 may be present, which transmits ultrasonic signals both to the surface 13 and to the reference element 30.

[0044] As described in detail in the prior art, the fill level 10 and / or quality of the fluid 12 is determined by evaluating an ultrasonic signal 112 transmitted by the ultrasonic transducer 110 to the fluid surface 13, reflected at the fluid surface 13, and received again, and by evaluating an ultrasonic signal 114 transmitted by another ultrasonic transducer to the reference element 30, reflected at the reference element 30, and received again. The quality of the fluid 12, such as the speed of sound in the fluid 12, can be determined based on the ultrasonic signal 114. Alternatively, as already mentioned, the fill level and quality can be ascertained based on the ultrasonic signal transmitted by a single provided ultrasonic transducer 110, which transmits ultrasonic signals both to the surface 13 and to the reference element 30.

[0045] As already mentioned, fluid sensor device 100 includes a printed circuit board 120, at least one ultrasonic transducer 110 arranged thereon, and optionally a further ultrasonic transducer. However, it goes without saying that further electronic components, such as capacitors, resistors, operational amplifiers, or even application-specific integrated circuits (ASICs), which are necessary for the proper operation of fluid sensor device 100, may be present on printed circuit board 120.

[0046] Figure 2 The schematic top view of the circuit board 120 of the fluid sensor device 100 is shown. The circuit board 120 has a recess 130. Figure 2 In the embodiment of FIG, a total of four drill holes 132, 134, 136, and 138 are formed. These drill holes 132, 134, 136, and 138 are preferably through-holes and extend completely through the circuit board 120 in the thickness direction. Alternatively, these four drill holes 132, 134, 136, and 138 can be configured as blind holes. It is also possible that drill holes 132, 134, 136, and 138 are configured as through-holes and the other drill holes 132, 134, 136, and 138 are configured as blind holes. For example, it may be preferable to configure drill hole 132 as a through-hole, while the other drill holes 134, 136, and 138 are configured as blind holes.

[0047] The respective drilling axes 133, 135, 137, 139 of the boreholes 132, 134, 136, 138 extend substantially parallel to one another and are arranged symmetrically with respect to one another such that the drilling axes 135, 137, 139 are arranged symmetrically about the central drilling axis 133. In particular, the drilling axes 135, 137, 139 lie at the corners of an imaginary equilateral triangle 131 extending substantially perpendicularly to the drilling axes 133, 135, 137, 139. In an alternative embodiment, the drilling axes 135, 137, 139 lie at the corners of each imaginary triangle, which does not necessarily have to be equilateral, and thus the drilling axes 135, 137, 139 do not necessarily have to be arranged symmetrically about the central drilling axis 133.

[0048] exist Figure 2 In the design scheme, the circuit board 120 has a total of three fixing areas 122, 124, and 126. Figure 2The ultrasonic transducer 110, schematically shown with dotted lines, can be fixed to the fixing area. The fixing areas 122, 124, 126 are preferably arranged in the immediate vicinity of the recess 130 or adjacent thereto, preferably adjacent to the bore 132 therein. The ultrasonic transducer 110 is mounted on the circuit board 120 by means of the fixing areas 122, 124, 126 in such a way that the ultrasonic transducer 110 at least partially extends over the recess 130. In other words, the ultrasonic transducer 110 is at least partially mounted above the recess 130 and the dimensions of the recess 130 are designed so that a sufficiently large area of ​​the recess exists outside the ultrasonic transducer 110 in the radial direction (as viewed in a top view), in which area the housing 140 (see FIG. 1 ) can be arranged. Figures 6 to 8 ): so that the housing region 142 (see also Figures 6 to 8 ) is at least partially arranged in the recess 130.

[0049] Recess 130 in circuit board 120 should be designed such that ultrasonic transducer 110 can be fixed to circuit board 120 and electrically connected thereto so that the overlap between ultrasonic transducer 110 and recess 120 is significantly greater than the overlap between ultrasonic transducer 110 and circuit board 120. Furthermore, it is preferred that the housing almost completely surrounds the ultrasonic transducer and is in contact with it over almost the entire surface.

[0050] Figure 3 Another possible embodiment for the form of the recess 130 is shown. Figure 3 , the depression 130 is formed by a total of five boreholes 132, 134, 136, 138, 144, whose borehole axes 133, 135, 137, 139, 145 extend essentially parallel to one another. The boreholes 132, 134, 126, 138, 144 are arranged so that they at least partially overlap to form an uninterrupted depression 130. As in Figure 3 As shown in FIG, the drilling axes 135, 137, 139, 145 are arranged symmetrically around the drilling axis 133 so that they are located at the corners of a virtual square 141. Figure 2 Similarly, here, as an alternative, it is also possible for the drilling axes 135 , 137 , 139 , 145 to be arranged at the corners of a quadrangle, preferably a rectangle.

[0051] according to Figure 3Ultrasonic transducer 110 can be fastened to circuit board 120 via a total of four fastening regions 122, 124, 126, 128, which are preferably arranged in the immediate vicinity of or adjacent to the recess, preferably adjacent to a bore therein. Ultrasonic transducer 110 is again mounted on fastening regions 122, 124, 126, 128 of circuit board 120 in such a way that it extends at least partially beyond recess 130.

[0052] Figure 4 and 5 Two further possible designs for the recess 130 are shown. Figure 4 and 5 The pit 130 and Figure 2 and 3 The difference between the recess 130 and the recess 130 is that it is a milled recess.

[0053] Figure 4 The recess 130 is three straight milling sections 132, 134, 136, which extend symmetrically at an angle of approximately 120° to each other starting from a common point 133. Figure 4 In a design of , ultrasonic transducer 110 can be mounted on printed circuit board 120 via three fastening regions 122, 124, 126 in such a way that ultrasonic transducer 110 again extends at least partially over recess 130, preferably over an area above common point 133. Fastening regions 122, 124, 126 are arranged in the immediate vicinity of recess 130 or adjacent thereto, preferably adjacent to an area around common point 133 and symmetrically thereto.

[0054] Figure 5 The pit 130 is a cross-shaped pit. Figure 5 The recess 130 can be formed by two straight milling portions 132, 134, which substantially intersect each other in the midpoint 133. Preferably, the two straight milling portions 132, 134 are substantially perpendicular to each other. Figure 5 In the embodiment of , the four fastening regions 122 , 124 , 128 , 126 are arranged centrally above the region around the center point 133 in such a way that the ultrasonic transducer 110 again extends at least partially over the recess 130 and is arranged above it.

[0055] In other advantageous designs, the recess 130 can also be constituted in different ways, such as by a combination of drilling and milling. In addition, it is also in accordance with the present invention that the recess 130 is provided in each form and manufactured with each manufacturing method known from the prior art.

[0056] Figures 6 to 8 The circuit board 120 of the fluid sensor device 100 is shown along the Figure 3 A sectional view along line AA of FIG. 1 is shown together with different design possibilities for housing 140 of fluid sensor device 100 .

[0057] Depend on Figure 6 It is known that the housing 140 surrounds the ultrasonic transducer 110 and at least partially surrounds the printed circuit board 120 in such a way that the housing region 142 is at least partially arranged in the recess 130, in particular in the borehole 132. This can preferably be produced by means of a plastic injection molding method or a plastic extrusion method, wherein, as already mentioned, the dimensions of the recess 130 are designed so that the plastic can pass through the areas of the recess 130 not covered by the ultrasonic sensor 110, for example, through the areas of the boreholes 134, 135, 138 not covered by the ultrasonic sensor 110 (see Figure 2 ) flows into the recess 130 so as to at least partially fill the recess.

[0058] In an alternative embodiment, the printed circuit board 120 can also be substantially completely surrounded by the housing 140 , so that a substantially closed section of the housing 140 is also located on the side of the printed circuit board 120 facing away from the ultrasonic transducer 110 .

[0059] Furthermore, the housing region 142 arranged in the recess 130 has a concave section 143 arranged on the side facing away from the ultrasonic transducer 110 and designed to divert the ultrasonic signal emitted by the ultrasonic transducer 110 at least partially away from the ultrasonic transducer 110 . Figure 6 In FIG, the ultrasonic signal diverted by the concave section 143 is indicated by a bent arrow 116. Figure 6 The concave section 143 of the embodiment is formed in the form of a cone.

[0060] Figure 7 The design of the recessed section 143 is similar to Figure 6 The design of the concave section 143 differs in that a partially spherical, preferably hemispherical, concave section 143 is arranged in the housing region 142 which is designed to partially divert the ultrasonic signal emitted by the ultrasonic transducer 110 away from the ultrasonic transducer 110. Figure 7 In FIG, such a deflected ultrasonic signal is indicated by a bent arrow 116 .

[0061] Said in Figures 6 to 8 The recessed section 143 shown in FIG. 1 can at least partially prevent ultrasonic signals transmitted downward by ultrasonic transducer 110 and not required for the measurement of fluid sensor device 100 from being reflected back to ultrasonic transducer 110 and detected there as interference signals. Furthermore, the decay time of ultrasonic transducer 110 can thereby be at least partially reduced.

[0062] In accordance with Figure 8 In the embodiment of the present invention, recessed section 143 is formed in the form of a cylindrical section, which is shaped such that housing section 142 has a thickness 40 in the region below ultrasonic transducer 110, and this thickness is dimensioned such that the ultrasonic signal emitted by ultrasonic transducer 110 can either be reflected back to ultrasonic transducer 110 in a defined manner or can be emitted through this thickness into the environment of fluid sensor device 100. For example, if thickness 40 of housing section 142 below ultrasonic transducer 110 corresponds approximately to a multiple of half the wavelength of the ultrasonic signal emitted by ultrasonic transducer 110, virtually complete transmission through housing section 142 can be achieved. In contrast, if the thickness 40 is dimensioned such that it corresponds to a plurality of odd integer multiples of a quarter wavelength of the ultrasonic signal transmitted by the ultrasonic transducer 110 , then almost complete reflection of the ultrasonic signal transmitted by the ultrasonic transducer 110 at the interface between the housing section 143 and the environment can be achieved.

[0063] Figure 9 An exemplary flow chart for a method for producing fluid sensor device 100 according to the present invention is shown.

[0064] Figure 9The method begins in step 200 and then reaches step 210, in which a circuit board 120 is provided. In a subsequent step 220, at least one recess 130 is created in the circuit board, extending at least partially into the interior of the circuit board along the thickness direction of the circuit board 120. In a subsequent step 230, at least one ultrasonic transducer 110 is mounted on the circuit board 120 such that the ultrasonic transducer 110 extends at least partially across the recess 130. In a further step 240, the circuit board 120 together with the ultrasonic transducer 110 is extruded with a plastic material for forming a housing 140 such that the housing 140 is at least partially arranged in the recess 130, in particular, the housing section 142 is arranged in the recess 130.

[0065] Here, it can be preferred that the step 230 includes: positioning the ultrasonic transducer 110 in a predetermined position on the circuit board 120; fixing the ultrasonic transducer 210 in the predetermined position by means of a positioning mechanism (not explicitly shown); and fixing the ultrasonic transducer 210 in the predetermined position in the fixing areas 122, 124, 126 and 128 (see Figure 2 ) and electrically connects the ultrasonic transducer 110 to the printed circuit board 120. The positioning mechanism can at least partially prevent the ultrasonic transducer 110 from moving out of its predetermined position during the soldering process, thereby at least partially improving the positioning accuracy of the ultrasonic transducer 110 on the printed circuit board 120. The ultrasonic transducer 110 can be fixed, for example, by soldering or gluing with a conductive adhesive.

[0066] The locking means can preferably be removed again before forming the housing 140 . Alternatively, the locking means can remain on the fluid sensor device 100 and likewise be surrounded by the housing 140 .

[0067] The present invention has the advantage of establishing a defined connection of ultrasonic transducer 110 to a printed circuit board, at least partially reducing the risk of shrinkage cavities in conventional full-surface solder connections. This allows for better damping of the decay characteristics of ultrasonic transducer 110 and reduced dispersion of the characteristics among various fluid sensor devices 100.

Claims

1. A fluid sensor device (100) for detecting a filling level (10) and / or a quality of a fluid (12) in a fluid container (14), wherein the fluid sensor device (100) comprises: - a circuit board (120) having at least one recess (130) extending at least partially into the circuit board (120) in the thickness direction of the circuit board (120), wherein the circuit board (120) has at least one fixing area (122, 124, 126, 128), an ultrasonic transducer (110), which is arranged on the at least one fastening area (122, 124, 126, 128) of the circuit board (120) in such a way that the ultrasonic transducer (110) extends at least partially over the recess (130), and a housing (140) which at least partially surrounds the printed circuit board (120) and the ultrasonic transducer (110) in such a way that a housing region (142) is at least partially arranged in the recess (130), wherein the recess (130) extends completely through the circuit board (120) along the thickness direction of the circuit board, The housing region (142) arranged in the recess (130) has a concave section (143) on a side facing away from the ultrasonic transducer (110), the concave section being designed to: - directing the ultrasonic signal transmitted by the ultrasonic transducer (100) at least partially away from the ultrasonic transducer (110), or - is reflected back in a defined manner to the ultrasonic transducer (110), or -Teleport into the environment.

2. The fluid sensor device (100) according to claim 1, wherein the recess (130) is formed by at least one borehole (132, 134, 136, 138, 144).

3. A fluid sensor device (100) according to claim 2, wherein the recess (130) is formed by four boreholes (132, 134, 136, 138) having parallel borehole axes (133, 135, 137, 135), wherein the borehole axes (133, 135, 137, 135) of three of the boreholes (134, 136, 138) are arranged relative to the borehole axis (133) of the other borehole (132) such that the borehole axes are located at the corners of a triangle (131), wherein the triangle is located in a plane perpendicular to the borehole axes (133, 135, 137, 139), and the boreholes (132, 134, 136, 138) at least partially overlap one another.

4. A fluid sensor device (100) according to claim 3, wherein the four boreholes (132, 134, 136, 138) respectively have the same borehole diameter, and the spacing of the borehole axes (135, 137, 139) of the three boreholes (134, 136, 138) relative to the borehole axis (133) of the middle borehole (132) approximately corresponds to 0.2 to 0.9 times the borehole diameter.

5. A fluid sensor device (100) according to claim 2, wherein the recess (130) is formed by five boreholes (132, 134, 136, 138, 144) having parallel borehole axes (133, 135, 137, 139, 145), wherein the borehole axes (135, 137, 139, 145) of four of the boreholes (134, 136, 138, 144) are arranged symmetrically with respect to the borehole axis (133) of the other borehole (132) so that the borehole axes are located at the corners of a quadrilateral (141), the quadrilateral being located in a plane perpendicular to the borehole axes (133, 135, 137, 139, 145), and the boreholes (132, 134, 136, 138, 144) at least partially overlap one another.

6. A fluid sensor device (100) according to claim 5, wherein the five boreholes (132, 134, 136, 138, 144) respectively have the same borehole diameter, and the spacing of the borehole axes (135, 137, 139, 145) of the four boreholes (134, 136, 138, 144) relative to the borehole axis (133) of the middle borehole (132) approximately corresponds to 0.2 to 0.9 times the borehole diameter.

7. The fluid sensor device (100) according to any one of the preceding claims 1 to 6, wherein the recess (130) is formed at least partially by milling.

8. The fluid sensor device (100) according to claim 7, wherein the recess (130) is formed by three linear milling portions (132, 134, 136), which extend symmetrically to one another at an angle of approximately 120° starting from a common point (133).

9. The fluid sensor device (100) according to claim 7, wherein the dimple is a cross-shaped dimple (130).

10. A method for producing a fluid sensor device (100) configured to detect a fill level (10) and / or a quality of a fluid (12) in a fluid container (14), the method comprising: - providing a circuit board (120), - generating at least one recess (130) in the circuit board (120), the recess extending at least partially into the inside of the circuit board along the thickness direction of the circuit board (120); - placing at least one ultrasonic transducer (110) on the circuit board (120) in such a way that the ultrasonic transducer (110) extends at least partially over the recess (130); and The printed circuit board (120) and the ultrasonic transducer (110) are at least partially extruded with the plastic used to form the housing (140) in such a way that the housing is at least partially arranged in the recess (130).

11. The method according to claim 10, wherein the recess (130) extends completely through the circuit board (120) along a thickness direction of the circuit board.

12. Method according to claim 10 or 11, wherein the recess (130) is produced by at least one drilling (132, 134, 136, 138, 144) and / or at least one milling (132, 134, 136).

13. The method according to claim 10 or 11, wherein the at least one ultrasonic transducer (110) is arranged on a circuit board (120) with: - positioning the ultrasonic transducer (110) at a predetermined position on the circuit board (120); - fixing the ultrasonic transducer (110) at the predetermined position by means of a positioning mechanism; and - Fixing the ultrasonic transducer (110) and electrically connecting it to the circuit board (120).

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