EP1005693B1 - Ultrasonic converter with a board for an electric circuit arranged in the longitudinal direction of the converter - Google Patents

Description

The invention relates to an ultrasonic transducer, in particular for a distance warning system in motor vehicles, with the Features of the preamble of claim 1.

Warning systems of this type are not used for the driver to report recognizable obstacles in the vicinity of the vehicle and to help the driver with parking and maneuvering his. Due to the constantly growing parking space a growing need for such parking assistance systems which usually have multiple ultrasonic transducers at the rear and front bumper. Since also such Parking assistance systems used for cheaper vehicle types should be, it is desirable to build and the To simplify the ease of installation of the ultrasonic transducers. The basic structure of such ultrasonic transducers is described for example in DE-OS 38 26 799.

From EP-A-0 283 823 an ultrasonic transducer is known, which in one housing is provided with a piezo crystal Resonator and has an electrical circuit. The electrical connection of the electrical components takes place using cables and contact pins. The problem is that the connection technology of the known ultrasonic transducer is complex.

The invention is therefore based on an ultrasonic transducer, such as it results from EP-A-0 283 823.

The task is solved by an ultrasonic transducer with the Features of claim 1.

In principle, the invention therefore consists in the Electronic circuit-bearing board (often also as PCB) no longer crossways in the usual way to the longitudinal direction of the housing, but this in insert essentially in the longitudinal direction of the transducer. This results in many advantageous training opportunities, as explained below.

These further training opportunities exist in particular in a greatly simplified connection technology of the assemblies inside the converter, in a simplified configuration of the Converter with its assemblies and components and one greatly simplified connection technology of the converter itself as well an improved position stabilization of the transducer within of the housing. A simplified assembly results from that the board in the longitudinal direction of the converter housing can be inserted into this. The difficult insertion the board in its transverse to the longitudinal direction of the housing Location is thus eliminated. The board also extends now in the direction of the first and second connecting lines, so that on the one hand the length of the connecting lines shortened and on the other hand the connecting lines no longer have to be bent so much. Seen differently, the Board itself so now a section of the connection between the piezo crystal and the external connections of the Converter.

In many cases it is desirable to have the electrical circuit on the Circuit board before finally closing the housing or measured during installation in the housing or match. It is therefore desirable, if possible short connection paths the reinforcement and / or Measure the vibration behavior of the electrical circuit. The use of the in Claim 2 features listed. The improvement is in Principle at this point in it, instead of single over Solder connection connecting wires a detachable provide electrical connection so that both the Measurement processes as well as the connection of the housing Connector in a simple manner with the circuit board electrically can be connected.

To make contact and set up the second connection lines can improve the second connecting lines by resilient contact arms preferably cast with the housing be educated. Here are the second connection lines by extending in the longitudinal direction of the housing resilient contact arms formed, so in other words, the Connector pins also the second connecting lines form.

The contact arms can be partially shed with the housing must be. It is also sufficient if they are in appropriate recesses are inserted and guided by these become.

To improve the contact, the second connection line be provided with electrical contacts, which PCB side with contacts of a contact strip on the Board are releasably connected. After that are the spring arms springy to ensure permanent contact to ensure slight changes in the position of the circuit board. For the rest, the contact springs ensure one on the PCB directional bias, which they also mechanically hold in the given position.

The resilient contact arms are shed with the housing at the same time for a good connection and a firm hold this arms in the case.

According to the invention, only a single flexible conductor foil is used provided on which both the first and second Connection lines are applied, so that this the number of components to be assembled is reduced.

To the for the assembly and the wire management on the rigid circuit board available space enlarge, according to the invention, on the flexible conductor film an all-round recess is provided in the short Sections of the contactable conductor tracks protrude. This Contacts are made with connecting contacts on the circuit board connected. This measure will spill over Conductor foil largely avoided over the rigid circuit board, so that a larger assembly room is available. There is also the possibility of using on both sides PCBs from both sides continue on the PCB to be able to access. The arrangement of the invention Printed circuit board still creates the possibility of a simple and secure storage of the board or circuit board, the connection board also as flexible conductor foil can be configured, as explained above. It can a corresponding guide groove on each side of the film or Plate may be provided or only one-sided Leadership.

To equip the housing with the circuit board and also to simplify the other components such as the plug and resonator, The combination of features is recommended in further training according to claim 2. The circuit board can thus be easier With their edges in the parallel grooves inserted and held by the first housing part.

It can be provided that the first housing part with is provided lateral holding arms that the guide grooves wear and in the assembled state of the housing in the Interior of the second housing part protrude, the contacts the circuit board with the resilient contact arms of the second Housing part are connected, so that because of the projecting Arms the platinum is easily accessible for measurement purposes. To the measuring process can be provided with the second contact arm Housing part are joined together with the first housing part, the resilient contact arms on the associated Attack the contacts of the contact strip on the circuit board.

The resilient contact arms clamp the circuit board Direction of the interior of the housing of the first housing part before and thus hold the circuit board firmly in the desired Location.

In order to make good use of the space inside the housing and the To reduce the length of the case, the resilient Contact arms extend in the radial direction and in one radially outgoing connector from the second housing part lead. The contact arms come out in the radial direction the connector of the first housing part and can thereby obtained a comparatively large length. This in turn can improve the spring action Take advantage of contact arms. The arms can comparatively long and without complicated shape.

Through the measures according to claim 3, the two Join housing parts particularly easily and detachably.

The suggestion was made above, the second To form connecting lines by long contact arms, so that in other words, the connector pins at the same time Take over the connection function to the board.

A particularly advantageous development of the invention exists in the combination of features according to claim 4 the connecting cables are not to be soldered individually Wires still through resilient contact arms, but through one flexible conductor foil formed. This eliminates the need for soldering of the individual connecting lines to the contacts of the circuit board. Rather, all contacting processes can be carried out in one single operation. By the invention The flexible circuit film will only position the board slightly curved. Otherwise, the film can be made from one heavy-duty thermally stable material, so that also pouring or foaming the housing Connection line (conductor foil) not damaged.

To the electrical circuit with the flexible conductor foil too connect, is recommended in further development of the invention Combination of features according to claim 5. Here, the electrical circuit on a separate fixed in itself Printed circuit board applied so that this to measurement and Adjustment purposes easy to handle and mechanically attachable is. The attachment can be done by stamp soldering, Plated-through holes or a similar process respectively.

Another simplification that addresses the additional Can save circuit board, results in the combination of features according to claim 7. Here, the electrical circuit in essentially through a highly integrated component shown, which sits directly on the flexible film, so that the otherwise necessary connection between components and Printed circuit boards and the printed circuit board in turn with the film through a direct connection of the module to the Foil is replaced.

Another advantageous resulting from the invention Further development describes claim 8. Then the piezo crystal with its connections directly on the conductor foil put on and connected to it electrically. Here you can again several contact points simultaneously be contacted and you get a very stable and secure first connection between the electrical circuit and the piezo crystal. In addition, the first Connection line with the piezo crystal as mechanical Unit to be handled.

In order to make the transducer usually pot-shaped It is recommended to be able to store the membrane safely and without problems the combination of features in a development of the invention according to claim 9. The use of a silicone ring is on known and for example in DE-OS 19 601 656 described. The invention makes it possible that the Membrane into an injection molded annular layer more elastic material is poured in, with the regular Bottom of the diaphragm cup opposite the air transmission medium should be accessible, so that preferably at least parts of the The outer surface of the pot thanks to the elastic intermediate layer be enveloped. According to a development of the invention the outer housing wall can then at least cover the intermediate layer partially enclose (claim 10).

To dampen the interior of the housing in the desired manner and Closing the housing is recommended in further training Invention the combination of features according to claim 11. Here a strain relief is created because, for example jagged edge structures undercuts for example with regard to the pouring mass, which the Secure the circuit foil or the circuit board and thus simultaneously provide strain relief for the connecting lines.

As a pouring compound has according to the combination of features Claim 12 foaming the interior of the housing proven.

In many cases, it is desirable that the outgoing connection lines can be freely selected by the converter. in this connection In particular, the use of the combination of characteristics is recommended according to claim 13. By this measure achieved that the second connecting lines in a fixed and thermally and mechanically highly resilient and bendable Material is stored so that the location of the connecting lines uncritical to the cable set towards the converter housing becomes.

The contacting of the second connection lines to the connecting several converters with a central control Cable set can be made through simple contactable districts on the protruding part of the second connecting line exist. These districts can be accessed through a waterproof connector according to the combination of features according to claim 15, so that you get a flexible connecting cable for the converter.

Another connection option to the cable set is in the Feature combination according to claim 16 described. After that the cable set also preferably consists of a flexible conductor film, so that to connect the converter to the Cable set only the two foils e.g. through plated-through hole or stamp soldering must be connected.

The use of conductor foils for both the outgoing second connecting line of the converter as well as for the Cable set has the advantage that the combination of features Claim 17 for fastening these components to the bumpers can be applied. Because the conductor foils are flat, there is a sufficiently large area for one adhesive adhesive layer available.

As a connection option between the flexible conductor foils designed cable set and the connecting line or the connecting line and the printed circuit board a stamp soldering, but also others Connection options can prove themselves here for example a contact rivet or the like.

To secure the solder or rivet connection, we recommend in Further development of the invention, the combination of features according to claim 19. A strain relief clamp is provided, the possibility of movement of the conductor foils in the longitudinal direction prevent the conductor tracks. These clamps can be used directly be attached in the contacting area and at one corresponding structure of the clamp also the Make contact.

Fig. 1

in auseinandergezogener Darstellung einen erfindungsgemäßen Wandler in einer ersten Blickrichtung.

Fig. 2

den Wandler nach Fig. 1 aus einer zweiten Blickrichtung

Fig. 3

in auseinandergezogener Darstellung die Anwendung einer flexiblen Leiterfolie für die Verbindungsleitungen

Fig. 4

einen vergrößerten Ausschnitt aus Fig. 3 mit einer als Zugentlastung wirkenden Randstruktur der Folie

Fig. 5

einen vergrößerten Ausschnitt nach Fig. 3

Fig. 6

ausschnittsweise eine gegenüber Fig. 3 geänderte Ausführungsform

Fig. 7

eine Halterungsmöglichkeit der Platine innerhalb des Gehäuses

Fig. 8

in stark schematisierter Ausführungsform einen Schnitt durch den erfindungsgemäßen Wandler

Fig. 9

in perspektivischer Ansicht den Wandler mit herausgeführter flexibler Leitungsfolie als Wandleranschluß

Fig. 10

in symbolischer Darstellung einen Kabelsatz mit Anschlußmöglichkeit für die einzelnen Wandler

Fig. 11

eine Zugentlastungsschelle mit einem Kontaktierungsbereich zwischen Wandlerabgang und Kabelsatz und

Fig. 12

einen vergrößerten Ausschnitt nach Fig. 9 mit Zugentlastungsschelle.

Embodiments of the invention are explained below with reference to the drawing. It shows:

Fig. 1

in an exploded view a transducer according to the invention in a first viewing direction.

Fig. 2

1 from a second direction

Fig. 3

in an exploded view the use of a flexible conductor foil for the connecting lines

Fig. 4

an enlarged section of FIG. 3 with an edge structure of the film acting as a strain relief

Fig. 5

3 shows an enlarged detail according to FIG. 3

Fig. 6

sections of an embodiment modified from FIG. 3

Fig. 7

a possibility of mounting the board within the housing

Fig. 8

in a highly schematic embodiment, a section through the converter according to the invention

Fig. 9

a perspective view of the transducer with the flexible conduit foil led out as a transducer connection

Fig. 10

in a symbolic representation a cable set with connection option for the individual converters

Fig. 11

a strain relief clamp with a contact area between the converter outlet and cable set and

Fig. 12

an enlarged section of FIG. 9 with strain relief clamp.

The housing of the converter shown in Fig. 1 consists of a first housing part 1 and a second housing part 2, wherein the second housing part partially broken open in the figures is shown.

The first housing part has two protruding one another opposite holding arms 3, the two guide grooves 4th wear which for guiding and receiving the edges 5 of the PCB 6 serve. So that the circuit board 6 between the holding arms 3 are inserted and held by them.

The circuit board is provided with a contact strip 7 which from individual contacts 8 on the second housing part 2 facing end 9 of the circuit board 6 are arranged. How are readily apparent when installing the circuit board 6 the contacts 8 are easily accessible from the outside in the holding arms 3, so that alignment measurements for those on the printed circuit board 6 circuits are carried out without difficulty can be.

After matching the circuit board, the second housing part 2 with the first housing part 1 via its locking tabs 10 put together, which shown recesses 13 on the second housing part 2 in the assembled state engage behind.

The rotational position of the sensor when installed in a bumper to define, the second housing part 2 is asymmetrical arranged recesses 33 provided. This will create a correct position of the two housing parts to each other enforced.

To the correct position of the assembled housing in the To force the bumper is a guide lug 14 on the External surface of the second housing part 2 is provided. The location in Longitudinal direction of the sensor is revolving Projection 15 set.

About a substantially annular plug 17 is the Resonator 18 of the transducer in the interior of the first Housing part 1 held.

The invention is not based on the application of the contact strip limited to the side 9 of the circuit board 6. Appropriate Contacts can also be found on the opposite page 19 of the Printed circuit board are provided and for example Contacting this plate with that in the resonator 18th located piezo crystal serve. You can do this as well in turn, spring arms are provided, which at one end attack the piezo crystal and join them at their other end Contacts, not shown, on the circuit board side 19 attack. The resonator 18 can, for example, be a Have use, which the resilient contact between the housing of the resonator or the piezo crystal on the a page and the contacts on page 19 of the Ensure circuit board 6.

In the holding elements (holding arms) could also Locking function can be integrated (outlined in Fig. 1), the by a locking hook, not shown, in the holding arm can be hinted at. Holding arms 3, constructed as a 3D-MID part (conductive plastic), can still be used for contacting serve between resonator 18 and circuit board 6.

The advantages of these measures are clearly evident because thereby the first housing part 1 of can be fitted on both sides in the longitudinal direction of the converter, whereby the circuit board 6 is inserted from one side and from the other side resonator 18 and plug 17 be inserted.

Fig. 2 shows an exploded view of a another view of the converter according to Fig. 1. For the The resilient contact arms 20 are particularly important to the invention, the radial direction of a not shown radially arranged connector 21 in the interior of the extend second housing part 2. The spring arms 20 wear on them in the interior of the second housing part 2 ends located in the longitudinal direction of the transducer extending terminals 22, the contacts 8 to both Pick up sides of the circuit board 2 and so a good one create electrical connection. To make contact improve and limit the path of the terminals 22, one Pick-up claw 23 on the rear wall of the second housing part 20 be injected. The invention can be described in other words Describe briefly as follows:

An ultrasonic transducer, consisting of the membrane 18 parts, Plug 17, housing front 1, printed circuit board 6 and Rear housing 2 should be installed. At the manufacturing time to lower, is supposed to be easier handling as well as saving of soldering processes. To do this are at the front Injection molded housing part holding the circuit board wear. There are plug connections on the circuit board attached to a simple connector contact with the modified rear housing part 2 to be able to realize. The membrane with the plug pushed on is inserted from the front into the front housing part.

On the front part of the housing 2 wings 3 are molded with groove 4, into which the circuit board is inserted, and during the Soldering the PCBs the strands to the PCB be fixed and the laser adjustment is carried out. The Handling the converter in this pre-assembled state hereby relieved. After the adjustment has been made rear housing part with molded, customer-specific Plug housing clipped on or clipped. In the rear part of the housing are plug pins with connector sockets injected, like they also with circuit board plug connections in the computer area are to be found. Accordingly, the circuit board is with provided plug-in socket contacts.

Another possibility is the elimination of all Solder connections in the converter. This is the contact To realize piezomembrane / circuit board by means of ring contact, which in the area of the membrane by means of springs, and in Area of the circuit board also with plug connections contacted.

Benefits:

• easier handling
• Soldering process for plug-in socket / PCB contacting deleted
• thus reducing the manufacturing time
• Easy removal if their failure occurs during the comparison.

In Fig. 3, a flexible conductor film 50 is shown, which first connection lines 51 and second connection lines 52 includes. The flexible conductor foil 50 has a continuous one Recess 53, protrude into the short lugs 54, in which the Conductor tracks 49 of the connecting lines 51, 52 open. This Conductor ends are designed as bare contact points, on which contacts of a board 56 can be placed, which, for example, as a rigid circuit board but also as flexible circuit board can be designed. On the Electronic components and circuit board sit corresponding line connections, for example, by an electronics module 57 are represented. The contacts 55 with the approaches acting as contact points 54 in suitably electrically connected to each other, for example by stamp soldering, through-plating or Nietkontaktierung. The advantage here is that the flexible Conductive foil both both connecting lines 51, 52 and includes the receiving surface for the circuit board 56. That the Piezzo crystal or the piezo ceramic 58 assigned Line end 59 is used to attach the piezo crystal of the conductor foil 50, with this conductor foil simultaneously the contacting of the piezo ceramic 58 compared to the first Connection line 51 is made. Details are in Fig. 5 shown.

The second connecting line 52 opens into one Plug housing 60, which corresponding plug contacts or Has pins and which via a locking element 61 in a plug receptacle can be inserted releasably. This as waterproof connector MQS connector can be made for example, be locked with the converter housing, but also as explained in connection with FIG. 8, via the Connection line 52 movable relative to the sensor housing be arranged.

In Fig. 4 a section A of Fig. 3 is enlarged enlarged drawn. The structured edge 63 is essential, which with a foamed or cast housing for a strain relief in the longitudinal direction of the flexible conductor film 50 provides.

However, it is not necessary that the first connection line 51 with the second connecting line 52 via the Edge areas 64, 65 are connected to one another. The connection can also on the circuit board 56 itself and corresponding mechanical or electrical connections happen, the electrical connections also mechanical Create a connection. The structured edge 63 can in this Trap also in the corresponding edge areas of the board 56 or the circuit board 56 are attached. Fig. 5 shows one Enlarged view of section B in Fig. 5. Here it can be seen that the piezo crystal 59 is essentially one has the shape of a circular disk, on the viewer facing surface the annularly cut end 66 of the Connection line 51 is, wherein, in the ring-shaped cut-out area the contacting planes 67 des Piezzo crystal 59 can be seen at the connection ends 68 of the interconnects of the connecting line 51 contacted are.

Fig. 6 shows a different solution for the structure of the Electronic circuit, with a high instead of the circuit board 56 integrated module on the one with no recess flexible conductor foil 50 is set.

The highly integrated ASIC chip is labeled 69. The areas of the conductor track not shown in FIG. 3 50 can be implemented as shown in FIG. 3.

In Fig. 7 is a cut part of a housing part shown for the converter. They are particularly important Insertion grooves 70 that guide the edge of the flexible Conductive foil 50 or the edge of the printed circuit board 56 or Serve circuit board.

The component group is shown in a symbolic representation in FIG Fig. 3 inserted into the one-piece sensor housing 71. It can be seen that the circuit board 56 with electronic components 57.87 is equipped on both sides, the 3 by the electronic module 57 Recess 53 of the flexible conductor film 50 protrudes. The piezo crystal 59 sits on the bottom 72 of the converter pot 73, the interior of the hollow cylindrical housing 71 is made of plastic poured or foamed to the in the housing 71st to secure seated assemblies or the interior of the as Resonator 73 serving converter pot in a suitable manner attenuate. A free end 74 of the second connection line 52 protrudes from the sealing compound 75 of the converter housing 71, so that 3 to the end of the connecting line 52 attached connector 60 to the converter housing free is movable. Usually, the converter housing 71 regularly provide a firm, slightly elastic material. There but on the other hand the lateral surfaces of the converter pot 73 must be suspended elastically, it is proposed to the Pot to pour an elastic layer 76 that has a gap fills between the pot 73 and the housing 71. The elastic layer can also be formed by an appropriately shaped Be silicone ring formed. On the other hand, it is possible only the elastic layer 76 to the outer surface of the Pour converter pot 73 and then in a second step to form the converter housing 71 in an injection molding process.

9 shows a two-part housing 77, wherein from this converter housing the free end 74 of the connecting line 52 protrudes. The applied on the flexible conductor foil Conductor tracks 78 open into contact areas 79, via which the Converter 77 can be connected to a central controller. By doing Free end 74 are still four holes 80 shown for example to relieve the strain on the connecting line 52 in the Contact area can serve. For this purpose, as in FIG. 12 a clamp 82 can be provided, which has the free end 74 the connecting line 52, the converter 77 secures.

A suitable strain relief clamp 82 is shown in FIG. 11 shown, the clamp body relative to the vehicle, for example via a bumper 83 shown in FIG. 10 is secured. The clamp 82 in FIG. 11 can, for example by suitable design not only for strain relief serve, but also support the contacting, whereby for Grip the strain relief pins 85 through the holes 80. The Cover of the clamp 82 is secured by a snap connection.

In Fig. 10 it is also shown that a cable set 85 for Connection of individual transducers attached to the bumper 83 can serve with a central plug 86. The cable set 85 can in turn be designed as a flexible conductor foil be, the conductor tracks 78 according to FIG. 11 via the associated contact areas 79 by stamp soldering with each other are connected. The cable set 85 is in a number of outgoing ends 86 divided to the free ends 74 of the individual converters, not shown, are performed. The as flat flexible conductor foil designed cable set 85 can be provided with an adhesive layer with which he on the Is glued inside the bumper 83. The Contact areas form solder joints and serve as prepared ones Solder deposits. The tines 88 reach through corresponding holes 80 in both film sections 86, 74, with the Foil sections tab-like from the converter housing 74 or protrude the cable set 85 (Fig. 9, Fig. 10). The flexible Conductor foils can be made from polyamide. Acting it is a plastic with high mechanical and thermal resilience. Be on this plastic the individual conductor tracks by means of suitable processes applied and covered with another film.

With regard to the manufacturing process can be as follows be followed: The membrane is either in one Silicone ring stored inside the housing or directly in it Injected housing or in the one-piece cylindrical Housing part 71 inserted. Via the circuit board or The flexible circuit film 50 is placed on the circuit board 56 and the Circuit board by means of stamp soldering (5-fold) with the foil electrically conductive and mechanically connected. Then will the entire strand including the pre-assembled piezo crystal inserted forward into the housing. The piezo crystal 59 is applied to the case back by Plastic applied and glued to the membrane and the flexible circuit foil in the area of the circuit board over the in the housing 71 integrated slot 70 secured. The Part of the circuit board, which is still to be measured and with to be compared to a laser, look here from the Housing out. After the laser adjustment, the Printed circuit board fully inserted into the housing 51 and potted or foamed. It is also conceivable, as shown in FIG. 7, to execute the housing 71 in two parts.

Claims (19)

1. Ultrasonic transducer, in particular for a distance-warning unit with a housing (71, 77) in which are arranged a resonator (73) provided with a piezo crystal (59) and a board (56) carrying an electric circuit (57, 87), the board (56) being arranged in a plane of which the perpendicular is substantially at right angles to the longitudinal direction of the housing (71, 77) and the transducer being provided with contactable terminal contacts, characterised in that first connecting lines (51) connect the piezo crystal (59) to the electric circuit (57, 87) and second connecting lines (52) connect the electric circuit to the contacts (79, 60), in that the contacts may be connected to a cable loom (85), in that the first and second connecting lines (51, 52) are arranged on a common integral elastic conducting foil (50) and in that the electric circuit is arranged on a substantially rigid printed-circuit board or board (56), the printed-circuit board (56) carrying electric circuit contacts which may be connected to the connecting lines (51, 52) on the flexible conducting foil (50).
2. Ultrasonic transducer according to claim 1, characterised in that the housing (71, 72) is divided in the radial direction and the first housing part (71) receiving the resonator (73) is provided with guide grooves (70) which extend in the longitudinal direction of the transducer or the radiation direction and hold the printed-circuit board (56) at its lateral edges.
3. Ultrasonic transducer according to claim 1 or 2, characterised in that the two housing parts (71, 77) may be mutually connected by latching.
4. Ultrasonic transducer according to any of the preceding claims, characterised in that the first and/or second connecting lines (51, 52) are formed by a flexible conducting foil (50) on which conductor tracks (55) are arranged.
5. Ultrasonic transducer according to any of the preceding claims, characterised in that the flexible conducting foil (50) is provided with a continuous aperture (53) in which contactable conductor tracks (49) project and in that the connecting contacts (55) of the electric circuit (57, 58) on the printed-circuit board (56) may be connected to the contactable conductor tracks (49).
6. Ultrasonic transducer according to any of the preceding claims, characterised in that at least one insertion groove (70) is provided which extends in the longitudinal direction of the housing and in which the associated edge region (64, 65) of the conducting foil and/or the printed-circuit board (56) is laterally mounted.
7. Ultrasonic transducer according to any of the preceding claims, characterised in that the electric circuit (57, 58) in the form of a highly integrated module (57) rests directly on the conducting foil (50) and may be connected via the terminal strip thereof directly to the conductor tracks (49).
8. Ultrasonic transducer according to any of the preceding claims, characterised in that the piezo crystal (59) is placed directly onto the end (58), facing it, of the conducting foil (50) and its electric contact planes (67) are contacted directly by the associated conductor tracks (49) of the conducting foil (50).
9. Ultrasonic transducer according to any of the preceding claims, characterised in that the substantially pot-shaped membrane (73) is inserted via an elastic intermediate layer (76) surrounding it into the membrane-side end of the housing (71) and in that the intermediate layer (76) is formed by a silicone ring or by an injection-moulded annular layer of a more flexible material different from the housing material.
10. Ultrasonic transducer according to claim 9, characterised in that the housing wall at least partially surrounds the intermediate layer (76).
11. Ultrasonic transducer according to any of the preceding claims, characterised in that strain relief structures (63) are grovided at the lateral edges (64, 65) of the conducting foil (50) and/or of the printed-circuit board (56).
12. Ultrasonic transducer according to any of the preceding claims, characterised in that the housing (71) provided with the resonator (73), the piezo crystal (59), the conducting foil (50) and optionally the printed-circuit board (56) is filled by foaming or casting with a suitable casting compound (75).
13. Ultrasonic transducer according to any of the preceding claims, characterised in that at least one free end (74) of the second connecting line (52) projects from the housing (71).
14. Ultrasonic transducer according to claim 13, characterised in that the terminal contacts (79) are contactable areas on the projecting part (74) at the free end (74) of the second connecting line (52).
15. Ultrasonic transducer according to claim 14, characterised in that the contactable areas (79) are located in the end region of the second connecting line (52) and are surrounded by a watertight plug terminal (60).
16. Ultrasonic transducer according to claim 8, characterised in that the contactable areas (79) are connected to a cable loom (85) by a soldering process, the cable loom (85) preferably being formed by a flexible conducting foil in the form of a flat strip.
17. Ultrasonic transducer according to any of the preceding claims, characterised in that the flat strip serving as the cable loom (85) is provided with an adhesive layer on one side by means of which the flat strip can be fastened to the internal face of a bumper (83).
18. Ultrasonic transducer according to any of the preceding claims, characterised in that the contact areas (79) are plated through by the associated conductor tracks of the flat strip (85) by stamp soldering.
19. Ultrasonic transducer according to any of the preceding claims, characterised in that at least one cord grip (82) is provided to secure the conducting foils (74, 85, 86) relative to the bumper (83) in the region of contact.

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