Membrane pot for an ultrasonic transducer and ultrasonic transducer

Abstract

Membrane pot (10) for an ultrasonic transducer, with a blind-shaped recess (18) which is bounded by a side wall (12) and a bottom area (13), wherein the bottom area (13) is designed for attaching a transducer element (20), wherein the membrane pot (10) is bounded at one end face by the bottom area (13) and has a radially outwardly projecting circumferential flange (14) at the other end face, • wherein the recess (18) in a cross-sectional plane arranged perpendicular to a longitudinal axis (11) of the membrane pot (10) has an oval-shaped inner contour (25) with a principal axis (27) and a minor axis (28), • wherein the inner contour (25) is at least approximately elliptical, and wherein the inner contour (25) has, in the direction of the minor axis (28) and mirrored to the major axis (27), a central section (29) which is curved in certain areas, wherein, viewed from the two central sections (29) in the direction of the major axis (27), a contour section (31) extends which is arranged within the contour (26) of an ideal ellipse, wherein the ideal ellipse is the ellipse whose smallest diameter corresponds to the maximum extent in the direction of the minor axis (281) of the inner contour (25) and whose larger diameter corresponds to the maximum extent in the direction of the major axis (271) of the inner contour (251), wherein, viewed from the contour section (31) in the direction of the major axis (27), a further contour section (32) adjoins the contour section (31), wherein the further contour section (32) lies outside the contour (26) of the The ideal ellipse is characterized by the fact thatthat the recess (18) in the area of ​​the flange (14) has a conically shaped transition area (19).

Description

State of the art

[0001] The invention relates to a membrane pot for an ultrasonic transducer according to the preamble of claim 1. Furthermore, the invention relates to an ultrasonic transducer with a membrane pot according to the invention.

[0002] A membrane housing for an ultrasonic transducer with the features of the preamble of claim 1 is known from DE 10 2006 050 037 A1 of the applicant. A number of requirements and properties must be met in the design and construction of such a membrane housing. These include, for example, the ability to manufacture the membrane housing as cost-effectively as possible while maintaining a compact design, the ability of the membrane housing to radiate sound vibrations in a desired direction, and the ability to minimize the amount of energy transferred from the membrane housing to the body structure of a vehicle via the ultrasonic transducer housing, in order to prevent, for example, the reception of interference signals or similar interference. Furthermore, the membrane housing must be designed in the area of ​​its membrane base to accommodate a transducer element, typically in the form of a piezoelectric element.To best meet the aforementioned requirements, the known diaphragm pot is designed to have a round outer contour and an oval inner contour. This inner contour features radially outward-projecting (with respect to a longitudinal axis of the diaphragm pot) arc-shaped sections on both longer sides. These arc-shaped sections facilitate the arrangement and / or mounting of the transducer element in question.

[0003] Document DE 10123612 A1 discloses an ultrasonic wave transmitter / receiver comprising a cylindrical housing with a bottom surface and a piezoelectric vibration element attached to the inner bottom surface of the bottom of the housing.

[0004] Document DE 19917862 A1 discloses an ultrasonic sensor, with a housing component having a cavity in the same and a bottom section provided at one end of the cavity.

[0005] Document DE 19912772 A1 discloses an ultrasonic sensor for distance measurement.

[0006] Document DE 11 2009 003 590 B4 discloses an ultrasonic transducer.

[0007] Document DE 11 2004 001 315 T5 discloses an ultrasonic transmitting and receiving device.

[0008] Document DE 10 2004 031 310 A1 discloses a membrane pot for an ultrasonic transducer.

[0009] Document DE 10 2014 207 681 A1 discloses a membrane for an ultrasonic transducer and an ultrasonic transducer. Disclosure of the invention

[0010] The membrane pot according to the invention for an ultrasonic transducer with the features of claim 1 has the advantage that the aforementioned requirements or desired properties with regard to the best possible acoustic decoupling of the membrane pot from the housing, i.e. the avoidance of the transmission of sound waves to the body structure, as well as a desired radiation characteristic of the ultrasonic waves, are optimized while at the same time the membrane pot is relatively inexpensive to manufacture.

[0011] According to the invention, the membrane pot is bounded at one end face by the bottom area and has a radially outward projecting, circumferential flange at the other end face, wherein, according to the invention, the recess in the area of ​​the flange has a conically shaped transition area.

[0012] According to the invention, the inner contour of the recess of the membrane pot is formed at least approximately elliptically in a cross-sectional plane arranged perpendicular to the longitudinal axis of the membrane pot, wherein the inner contour has a central section in the direction of the secondary axis, mirroring the main axis, which is curved in some areas, wherein a contour section extends from the two central sections in the direction of the main axis, which is arranged within the contour, and wherein a further contour section adjoins the contour section in the direction of the main axis, wherein the further contour section runs outside the contour of the ideal ellipse.It has been found that approximating the inner contour to an ellipse optimizes the desired radiation pattern, which achieves a relatively large radiation angle in a horizontal plane and a relatively small radiation angle in a vertical plane (compared to the horizontal plane). Furthermore, it minimizes energy coupling into the side wall of the diaphragm pot, meaning that the sound vibrations are radiated primarily perpendicular to the plane of the diaphragm base, as desired. However, an ideal elliptical contour is relatively difficult to achieve given the other constraints, particularly the feasibility of integrating the transducer element (piezoelectric element) into the diaphragm base while maintaining a compact diaphragm pot. Therefore, an inner contour optimized for practical application typically deviates somewhat from the ideal elliptical shape.

[0013] In other words, according to the invention, the inner contour is at least approximately elliptical, wherein the inner contour has a central section in the direction of the minor axis, mirroring the major axis, which is curved in certain areas, wherein a contour section extends from the two central sections in the direction of the major axis, which is arranged within the contour of an ideal ellipse, wherein the ideal ellipse is the ellipse whose smallest diameter corresponds to the maximum extent in the direction of the minor axis of the inner contour and whose larger diameter corresponds to the maximum extent in the direction of the major axis of the inner contour, wherein a further contour section adjoins the contour section in the direction of the major axis, wherein the further contour section lies outside the contour of the ideal ellipse.

[0014] Advantageous further developments of the membrane pot according to the invention for an ultrasonic transducer are listed in the dependent claims.

[0015] In order to realize the aforementioned mounting of the transducer element (piezoelectric element) with a membrane pot that is as compact as possible with regard to its external dimensions, it is provided according to the invention that the inner contour, which is at least approximately elliptical, has a central section in the direction of the secondary axis that is symmetrical to the main axis and is curved in some areas.

[0016] In order to adapt the inner contour required due to the installation or arrangement of the converter element as closely as possible to the (ideal) elliptical shape, it is furthermore provided according to the invention that the maximum extent of the inner contour in the direction of the main axis and the secondary axis coincides with the contour of an (ideal) ellipse.

[0017] In practice, an inner contour has proven to be particularly advantageous in which, viewed in the direction of the main axis, it has, outside the curved central section (which serves to receive or is adapted for the transducer element), a first contour section which runs outside the ideal elliptical contour, and in which a second contour section is connected to the first contour section on the side facing away from the curved central section, which runs within the ideal elliptical contour, and which coincides with the ideal elliptical contour in the area of ​​maximum extension in the direction of the main axis.

[0018] In order to create a specific, consistently uniform distance between the inner contour of the membrane pot and the transducer element when the transducer element is circular, it is provided that the inner contour in the area of ​​the (curved) central section is shaped like a circular arc segment.

[0019] The invention further comprises an ultrasonic transducer with a membrane pot according to the invention as described so far. Such an ultrasonic transducer is characterized by optimized function and relatively cost-effective manufacturing.

[0020] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing.

[0021] This shows in: Fig. 1 a simplified longitudinal section through a membrane pot as part of an ultrasonic transducer, Fig. 2 a perspective view of the membrane pot according to Fig. 1 without a converter element arranged therein, Fig. 3 a cut in plane III-III of the Fig. 1 and Fig. 4 a semi-longitudinal section of the membrane pot according to the Fig. 1 and Fig. 2 to illustrate the vibration characteristics of the membrane pot in comparison to a membrane pot according to the state of the art.

[0022] Identical elements or elements with the same function are provided with the same reference numbers in the figures.

[0023] The figures show a membrane housing 10 for an ultrasonic transducer (not shown), wherein the ultrasonic transducer is arranged, in particular, in the area of ​​a motor vehicle's bumper and is part of a driver assistance system for detecting objects and their distance from the bumper. The membrane housing 10 shown in the figures is connected to a housing of the ultrasonic transducer (not shown), which, in the installed state, is at least indirectly connected to the aforementioned bumper.

[0024] The essentially cup-shaped membrane pot 10, made of metal, is manufactured using deep drawing or extrusion processes and has a longitudinal axis 11. A side wall 12 concentrically surrounds the longitudinal axis 11. The membrane pot 10 is further bounded at one end face by a base region 13 or membrane base, and has a radially outwardly projecting, circumferential flange 14 at the other end face. The outer contour 16 of the membrane pot 10, or its cross-section, is circular, and the blind-hole-shaped recess 18, bounded by the side wall 12 and the base region 13, has a conically shaped transition region 19 on its inner side.

[0025] While the wall thickness d of the side wall 12 is at least approximately constant when viewed in the direction of the longitudinal axis 11, except in the area of ​​the flange 14 and in the bottom area 13, the wall thickness d changes when viewed in the circumferential direction of the side wall 12.

[0026] Within the recess 18, on the floor area 13, there is only a [missing word - likely "] in the Fig. Figure 1 shows a transducer element 20, in particular in the form of a piezoelectric actuator, which is rigidly connected to the base area 13 via an adhesive layer (not shown) or similar material. During a transmission phase, the transducer element 20 excites the base area 13 to vibrate in a direction of vibration along the longitudinal axis 11, as indicated by the double arrow 21. Due to the rigid coupling of the base area 13 to the side wall 12, the side wall 12 is also excited to vibrate, specifically transverse vibrations, as illustrated by the double arrow 22.

[0027] While, as explained above, the outer contour 16 of the diaphragm pot 10 is at least approximately round or circular, the inner contour 25 of the diaphragm pot 10 is at least approximately elliptical in the area between the flange 14 and the bottom area 13. The exact shape of the inner contour 25 compared to an ideal contour 26 of an ellipse is shown in the Fig. Figure 3 shows in more detail. In particular, it can be seen that the inner contour 25 has a principal axis 27 and a minor axis 28, which are arranged perpendicular to each other, with the intersection of the principal axis 27 and the minor axis 28 coinciding with the longitudinal axis 11 of the diaphragm pot 10. Furthermore, it can be seen that, viewed in the direction of the minor axis 28 and symmetrically to the principal axis 27, two arc-shaped central sections 29 are provided. When the transducer element 20 is mounted, these central sections 29 preferably have a constant distance from the outer circumference of the (circular or disc-shaped) transducer element 20. The two central sections 29 extend, in particular, within the (ideally elliptical) contour 26. From the two central sections 29, a contour segment 31 extends in the direction of the principal axis 27 and is arranged within the contour 26.Adjoining contour section 31 in the direction of the major axis 27 is a further contour section 32, characterized in that this further contour section 32 lies outside the contour 26 of the ideal ellipse. A further characteristic of the inner contour 25 is that, in the region of the major axis 27 and the minor axis 28, the maximum extent of the inner contour 25 coincides with the maximum extent of the (elliptical) contour 26.

[0028] In the Fig.Figure 4 illustrates the advantage of an approximately elliptical inner contour 25, as described above, compared to a conventional contour according to the prior art, when the membrane pot 10 is vibrated by a transducer element 20. It is particularly evident that the vibration amplitude a of the side wall 12 in the radial direction of the membrane pot 10, as shown in graph X, is significantly lower than the vibration amplitude a in the side wall of a conventional membrane pot, as shown in graph Y. In other words, this means that the vibration energy transmitted by the transducer element 20 into the membrane pot 10 is transmitted in the desired manner essentially in the direction of the longitudinal axis 11, and not in a direction perpendicular to the longitudinal axis 11, i.e., coupled into the side wall 12.In particular, due to such a radiation characteristic, no or fewer disturbing sound waves are detected by a further membrane pot 10 or ultrasound transducer arranged next to the membrane pot 10 than by a conventional membrane pot.

[0029] The membrane pot 10 described so far, or its geometry, may deviate at least slightly from the geometry described so far without deviating from the inventive concept. This concept consists in forming the inner contour 25 of the membrane pot 10 at least approximately elliptical.

Claims

[1] Membrane pot (10) for an ultrasonic transducer, with a blind-shaped recess (18) which is bounded by a side wall (12) and a bottom area (13), wherein the bottom area (13) is designed for attaching a transducer element (20), wherein the membrane pot (10) is bounded at one end face by the bottom area (13) and has a radially outwardly projecting circumferential flange (14) at the other end face, • wherein the recess (18) in a cross-sectional plane arranged perpendicular to a longitudinal axis (11) of the membrane pot (10) has an oval-shaped inner contour (25) with a principal axis (27) and a minor axis (28), • wherein the inner contour (25) is at least approximately elliptical, and wherein the inner contour (25) has, in the direction of the minor axis (28) and mirrored to the major axis (27), a central section (29) which is curved in certain areas, wherein, viewed from the two central sections (29) in the direction of the major axis (27), a contour section (31) extends which is arranged within the contour (26) of an ideal ellipse, wherein the ideal ellipse is the ellipse whose smallest diameter corresponds to the maximum extent in the direction of the minor axis (281) of the inner contour (25) and whose larger diameter corresponds to the maximum extent in the direction of the major axis (271) of the inner contour (251), wherein, viewed from the contour section (31) in the direction of the major axis (27), a further contour section (32) adjoins the contour section (31), wherein the further contour section (32) lies outside the contour (26) of the follows an ideal ellipse, characterized by, that the recess (18) in the area of ​​the flange (14) has a conically shaped transition area (19). [2] Membrane pot according to claim 1, characterized by , that the inner contour (25) in the area of ​​the middle section (29) is formed in the shape of a circular arc segment. [3] Membrane pot according to one of claims 1 or 2, characterized by , that the outer contour (16) of the membrane pot (10) is circular. [4] Ultrasonic transducer with a membrane pot (10) designed according to one of claims 1 to 3.

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