Abstract:
An ultrasonic transducer system includes at least one transducer element, a diaphragm, and at least one resonance body, the ultrasonic transducer system being configured for transmitting and/or receiving ultrasonic signals, the resonance body being coupled at an end face to the diaphragm and the at least one transducer element being coupled to a lateral surface of the resonance body so that the at least one transducer element and the resonance body have a shared interface. Also described is a method for the manufacture and to a motor vehicle having an ultrasonic transducer system of this type, the diaphragm of the ultrasonic transducer system being formed by an outer skin of a bumper, a side mirror, or a door section, and the transducer element(s) and resonance bodies being situated concealed behind the outer skin.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an ultrasonic transducer system which is configured for transmitting and/or receiving ultrasonic signals, and which includes at least one transducer element and a resonance body. The present invention additionally relates to a method for manufacturing an ultrasonic transducer system of this type and a motor vehicle including an ultrasonic transducer system of this type. 
       BACKGROUND INFORMATION 
       [0002]    Transducer systems for ultrasonic-based surroundings-sensing are used in relation to motor vehicles, moving or stationary machines, such as robots, agricultural machines, or construction machines. To achieve high transmitting power and/or reception sensitivity, these are predominantly resonant transducers, which are made up of solid state bodies and one or multiple transducer elements. 
         [0003]    An ultrasonic transducer is discussed in US 2010/0208553 A1 which is installed concealed in an automobile bumper and is used for example for parking assistance purposes. The piezo element is configured as a thin ceramic disk which is situated in parallel to an emission plane of the transducer. 
       SUMMARY OF THE INVENTION 
       [0004]    An ultrasonic transducer system according to the present invention includes at least one transducer element, a diaphragm, and at least one resonance body, the resonance body being coupled at an end face to the diaphragm, and the at least one transducer element being coupled to a lateral surface of the resonance body in such a way that the at least one transducer element and the resonance body have a shared interface. 
         [0005]    The definition of the transducer element is thereby to be broadly conceived and includes, for example, electrical-acoustic transducers, which function according to electrostatic, magnetostrictive, piezoelectrical effects, or combinations of these effects. Within the scope of the present invention, the transducer element may in particular be a piezoelectric element and the ultrasonic transducer system may be referred to as a piezoelectric ultrasonic transducer system. 
         [0006]    The diaphragm of the ultrasonic transducer system is formed, for example, by an outer skin of a bumper, a side mirror, or a door section of a motor vehicle, the transducer element(s) and the resonance body or resonance bodies being situated concealed behind the outer skin. Due to the coupling, the diaphragm forms a resonance diaphragm of the ultrasonic transducer system. In contrast to known transducer elements mounted in a concealed manner, the system according to the present invention represents an alternative in which there exist savings potentials, for example in that thinner transducer elements may be used or less material may be used for the transducer elements. 
         [0007]    Advantageous refinements and improvements of the subject matter defined in the independent claim are possible due to the features listed in the dependent claims. 
         [0008]    It may be provided that the diaphragm is formed from a thin material layer which is manufactured for example from a polymer material. The diaphragm may have a thickness between 0.1 mm and 5 mm, particularly less than 2 mm or less than 1 mm. The coupling of the resonance body at the end face to the diaphragm may be carried out directly or indirectly, however, in any case in such a way that an acoustic coupling is enabled at a sufficient level, i.e., that suitable oscillations may be transmitted. The coupling may be accomplished, for example, by a press fit or force fit, such as by screwing in, or also by adhesive bonding. The coupling may also be carried out by extrusion coating the resonance body with the material of the outer skin, which may also be referred to as embedding. An indirect coupling may mean that an additional material layer is provided between the resonance body and the diaphragm, for example, a fluid like a gel or an oil. The additional material layer may be provided in particular for the purpose of optimizing the acoustic coupling between the resonance body and the diaphragm, for example to compensate for tolerances in the dimensions of the components or the roughness of the surfaces of the coupling partners. 
         [0009]    According to one specific embodiment, the resonance body has a front mass and a rear mass which are manufactured from different materials. The electroacoustic emission emitted by the transducer element for surroundings sensing thus leaves the transducer system in the direction of the end face of the resonance body, therefore rearward emission is suppressed. The rear mass functions as a so-called inertial mass, i.e., due to its inertia, it enables the introduction of force into the front body and thus also functions to attenuate the oscillations with respect to the range in which no emission is desired. According to one specific embodiment, it is provided that the transducer element is coupled circumferentially at a lateral surface of the front mass. 
         [0010]    The front mass may be manufactured from a plastic or rubber material and the rear mass from a metal, for example, from aluminum, sheet metal, steel, or brass. The selection of suitable materials may be determined by limitations or specifications with respect to the reception sensitivities or transmission signal strengths to be achieved by the ultrasonic transducer system. In particular, however, additional surrounding influences, such as the ambient temperature or, for example, the mechanical load due to shaking, may also be considered in order to determine suitable materials. 
         [0011]    According to one specific embodiment, the resonance body has a shape tapering toward the end face. A taper of this type may, for example, be formed by one or multiple shoulders, i.e., a step-wise reduction of the cross section of the resonance body, or also by a continuous reduction of the cross section of the resonance body. 
         [0012]    The resonance body and/or the transducer element may have a ring-shaped design. It is possible that the resonance body is a solid body, for example a cylindrical body, which is accommodated in a ring-shaped transducer element or that the transducer element is a solid body, for example a cylindrical body, which is accommodated in a ring-shaped or pot-shaped resonance body. It may alternatively be provided that the resonance body and also the transducer element have a ring-shaped design; one ring may be fitted into the other so that the resonance body surrounds the transducer element or so that the transducer element surrounds the resonance body. Ring-shaped may mean here in particular that the corresponding body has a through opening so that there is an inner peripheral surface of the body and an outer peripheral surface. The inner and outer peripheral surfaces are thereby referred to as lateral surfaces. A coupling to a lateral surface of the resonance body may be referred to as a coupling to the inner peripheral surface as well as a coupling to the outer peripheral surface. 
         [0013]    Depending on the specific embodiment, the resonance body has a round, triangular, quadrangular, rectangular, or polygonal cross section. Polygonal may mean a pentagonal, hexagonal, or octagonal cross section, a regular structure, for example equally-long segments of a polygonal line approximating a circular area, which may be a particular embodiment. The cross sections may be determined by limitations or specifications with respect to the sensitivities to be achieved in the ultrasonic transducer system as well as by surrounding influences like, for example, vibration resistance or a temperature resistance, the objective of performance optimization having priority. 
         [0014]    According to one specific embodiment, the transducer element and the resonance body are coupled to one another by a press fit or by adhesive bonding. The selection of the coupling may be determined by the anticipated application area, for example by specifications of vibration resistance of the system. 
         [0015]    According to one specific embodiment, the ultrasonic transducer system has exactly one transducer element which is fully circumferentially coupled to the lateral surface. It may alternatively be provided that the ultrasonic transducer system has multiple transducer elements which are each partially circumferentially coupled to the lateral surface. 
         [0016]    The present invention may be used in particular in surroundings sensors of the type which are provided, for example, in front and/or rear bumpers of the vehicle for the purpose of parking assistance and/or collision avoidance. Ultrasonic signals are thereby conventionally transmitted by a medium like air or water from an emitter to a receiver, or are transmitted from an emitter into the surroundings, or ultrasonic signals reflecting from an object located in the surroundings are detected, and the transit time and/or transit time differences and/or additional variables, for example amplitudes and phases of the ultrasonic signals, are measured. Typically, ultrasonic transducers are thereby used which may emit ultrasonic waves as well as receive ultrasonic waves. However, it may also be provided that the ultrasonic transducers are used only as receivers or only as transmitters. 
         [0017]    In particular, the ultrasonic transducer system may be installed in an ultrasonic system which includes a group of ultrasonic sensors, at least one, which may have all, ultrasonic sensors including the features of the ultrasonic transducer system. The ultrasonic system may be configured, for example, for the purpose of detecting partial surroundings of the motor vehicle. For example, the ultrasonic sensors in the front area for detecting the surroundings ahead of the vehicle and/or the ultrasonic sensors in the side areas for detecting a side area of the vehicle and/or the ultrasonic sensors in the rear end for detecting rearward surroundings of the vehicle are each assigned to an ultrasonic system of this type. Typically, four to six sensors are hereby installed in a bumper, only a maximum of four sensors being mounted with approximately the same line of sight. In order to also particularly detect the surroundings next to the vehicle, additional sensors are positioned in the front bumper in such a way that they have detection areas to the left and to the right. Additionally or alternatively, sensors may also be positioned in the rear bumper in such a way that these detect an area to the left and right next to the motor vehicle. The ultrasonic system additionally also has a control device and a signal processing unit assigned to the respective group. To detect the side area of the vehicle, ultrasonic sensors installed laterally in the front and rear bumpers may be used as well as sensors of this type which are installed in a side mirror or in a door section. 
         [0018]    The present invention provides an ultrasonic transducer which is additionally suited for a use for the flow measurement of fluid media, in particular in the intake manifold and/or in the exhaust gas system and/or in the exhaust gas recirculation system and/or downstream from a turbocharger of internal combustion engines in the motor vehicle sector. 
         [0019]    A method for manufacturing an ultrasonic transducer system which is configured for transmitting and/or receiving ultrasonic signals, in particular one of the previously described ultrasonic transducer systems, includes the following steps: 
         [0020]    a) manufacturing a device including a transducer element and a resonance body, the at least one transducer element being coupled to a lateral surface of the resonance body in such a way that the at least one transducer element and the resonance body have a shared interface, 
         [0021]    b) fastening the device to a diaphragm which is formed by an outer skin of a component, the resonance body being coupled at an end face to the diaphragm. 
         [0022]    According to an additional aspect of the present invention, a motor vehicle has a bumper, a side mirror, or a door section and a previously described ultrasonic transducer system, the diaphragm of the ultrasonic transducer system being formed by an outer skin of the bumper, the side mirror, or the door section, and the transducer element(s) and the resonance body or resonance bodies being situated concealed behind the outer skin. 
         [0023]    If the thickness of the outer skin of the bumper or the side mirror or the door section, in which the ultrasonic transducer system is installed, does not correspond to the thicknesses listed above for acoustic transmission, it may be provided that the bumper, the side mirror, or the door section of the vehicle, in which the ultrasonic transducer system is to be installed, is configured to be correspondingly thinner than otherwise. Local attenuations of this type may be incorporated by subsequent machining, for example, by milling, or already in the manufacturing process, for example during injection molding. 
         [0024]    Exemplary embodiments of the present invention are shown in the drawings and are explained in greater detail in the subsequent description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIGS. 1A and 1B  show ultrasonic transducers according to the related art. 
           [0026]      FIGS. 2A, 2B and 2C  show ultrasonic transducers according to the related art. 
           [0027]      FIGS. 3A and 3B  show ultrasonic transducer systems according to the present invention. 
           [0028]      FIGS. 4A, 4B, 4C and 4D  show cross sections through ultrasonic transducer systems according to the present invention according to different specific embodiments. 
           [0029]      FIGS. 5A, 5B, 5C and 5D  show cross sections through ultrasonic transducer systems according to the present invention according to additional specific embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]      FIG. 1A  shows an ultrasonic transducer  2  including a transducer element  4  which is formed as a flat disk and whose main surface  5  abuts on a thick resonance body  6 .  FIG. 1B  shows an additional ultrasonic transducer  2  in which a flat transducer element  4  is adjacently situated between a thick resonance body  6  and a thick rear mass  8  with their main surfaces  5 . The ultrasonic transducers shown in  FIG. 1A  and  FIG. 1B  are also referred to as so-called thickness oscillators. 
         [0031]      FIG. 2A  through  FIG. 2C  show ultrasonic transducers  2  which are referred to as bending oscillators. The emission direction of ultrasonic transducer  2  is indicated in  FIG. 2A  by an arrow; the emission direction of ultrasonic transducer  2  shown in  FIG. 2B  and  FIG. 2C  is equivalent. Ultrasonic transducer  2  from  FIG. 2A  includes a flat transducer element  4  which abuts with its main surface  5  against a flat resonance body  10 . An ultrasonic transducer  2  is shown in  FIG. 2B  which is implemented by two transducer elements  12 ,  14  abutting against one another, these being contacted in opposition. For example, while first transducer element  12  is constricted with a first electrical signal, second transducer element  14  expands so that a spatial oscillation amplitude is produced. Another specific embodiment of a bending oscillator is ultrasonic transducer  2  shown in  FIG. 2C  in which two transducer elements  12 ,  14  are contacted and situated in parallel to one another, a flat resonance body  10  being situated between transducer elements  12 ,  14  in order to amplify the acoustic oscillations. 
         [0032]      FIG. 3A  shows an ultrasonic transducer system  18  according to a first specific embodiment of the present invention in a side sectional view. Ultrasonic transducer system  18  includes a transducer element  23 , a diaphragm  22 , and a resonance body  20 . Resonance body  20  is coupled to diaphragm  22  via an end face  24 , i.e., in the specific embodiment shown, end face  24  forms an interface to diaphragm  22 . The coupling between resonance body  20  and diaphragm  22  may be carried out directly or indirectly; an indirect contact means that at least one layer of an additional material, for example a fluid layer like an oil or gel, is situated between end face  24  of resonance body  20  and diaphragm  22  in order to improve the acoustic coupling. A mechanical coupling may be present between end face  24  of resonance body  20  and diaphragm  22 , for example via a screw joint or a clamping joint of resonance body  20  in diaphragm  22 , a suitable arrangement for this purpose not being shown in  FIG. 3A . It may likewise be provided that resonance body  20  is glued to diaphragm  22 . It may be provided that diaphragm  22  is configured to be thinner in a contact area  32  than outside of contact area  32  so that resonance body  20  is at least partially countersunk in the diaphragm in contact area  32 . This has the advantage that ultrasonic transducer system  18  may be configured on the one hand to be sufficiently sensitive for receiving ultrasonic waves or may emit sufficiently strong ultrasonic waves and on the other hand diaphragm  22  may be configured to be sufficiently thick outside of contact area  32 . 
         [0033]    Transducer element  23  is situated on a lateral surface  26  of the resonance body in such a way that these have a shared interface with one another. Lateral surface  26  extends approximately perpendicularly to end face  24  in the exemplary embodiment shown. A diameter  30  of the cross section of resonance body  20  on the level of transducer element  23  is greater than contact area  32  which corresponds to a diameter of the cross section of end face  24  of resonance body  20 . Resonance body  20  thus has a shape tapering toward end face  32 . The taper is formed in the exemplary embodiment shown in  FIG. 3A  by a shoulder  28 , i.e., it includes a step-wise reduction of the cross section of resonance body  20 . 
         [0034]    Resonance body  20  includes in the exemplary embodiment shown a front mass  36  and a rear mass  38  which may be made from different materials. Likewise, more than two material layers may be present; these may be surrounded partially or completely by transducer element  23 . In the exemplary embodiment shown, front mass  36  may be completely surrounded by transducer element  23  and rear mass  38  only partially. 
         [0035]      FIG. 3B  shows an ultrasonic transducer system  18  according to an additional specific embodiment of the present invention. Ultrasonic transducer system  18  also includes a resonance body  20  which contacts a diaphragm  22  at an end face  24 . Contact area  32 , which coincides with the diameter of the cross section of end face  24  of resonance body  20 , is smaller than diameter  30  of the cross section of resonance body  20  on the level where transducer element  23  circumferentially contacts resonance body  20  at a lateral surface  26 . The taper results in the exemplary embodiment shown due to a consistent reduction of the cross section, and in the exemplary embodiment shown due to a conic section  34  of resonance body  20 . 
         [0036]    Resonance body  20  has a ring-shaped design on the level of transducer element  23 . A radially symmetrical recess  35  having a diameter  37  is located centrally. An inner peripheral surface  39 , which is a peripheral surface of the recess, and also an outer peripheral surface  33  of the resonance body, are referred to as lateral surface  26 . Diameter  37  of recess  35  is selected as smaller in the exemplary embodiment shown than the diameter of the cross section of end face  24  which forms contact area  32 ; however, it may also be larger than the latter. The recess has a height  41  which here, for example, corresponds to the size of transducer element  23 . 
         [0037]      FIG. 4A  shows a possible cross section through ultrasonic transducer system  18  in  FIG. 3A  along line z-z. In the specific embodiment shown, resonance body  20  has a rectangular cross section with a cross-sectional depth  44  and a cross-sectional width  46  assignable to the cross section. Transducer element  23  includes here a first transducer element  50  and a second transducer element  52  which partially circumferentially contact resonance body  20  at two diametrically opposed peripheral surface sections  42 . Resonance body  20  of the rectangular cross section thus has two non-covered peripheral surface sections  40  and two covered peripheral surface sections  42 . 
         [0038]      FIG. 4B  shows an alternative specific embodiment of ultrasonic transducer system  18  from  FIG. 3A . In this exemplary embodiment, transducer element  23  is configured as one piece and surrounds resonance body  20  fully circumferentially, which is configured having a rectangular cross section. Resonance body  20  thus has only covered peripheral surface sections  42 . 
         [0039]      FIG. 4C  shows an additional specific embodiment of ultrasonic transducer system  18  shown in  FIG. 3A , in which resonance body  20  has a hexagonal cross section. Two transducer elements  23  are shown which cover two peripheral surface sections  42  which are situated diametrically opposite to one another. Alternatively, three transducer elements  23  may also be provided. 
         [0040]      FIG. 4D  shows an additional specific embodiment of an ultrasonic transducer system  18  from  FIG. 3A , a hexagonal cross section of resonance body  20  being shown with a transducer element  23  coupled fully circumferentially. 
         [0041]    Additional specific embodiments are possible, in which resonance body  20  may have a polygonal cross section and one or multiple transducer elements  23  may be provided, which are each coupled partially circumferentially to lateral surface  26  of the resonance body or are coupled fully circumferentially to lateral surface  26  of the resonance body. 
         [0042]      FIG. 5A  shows a cross-sectional view of the exemplary embodiment shown in  FIG. 3B  of ultrasonic transducer system  18  along line y-y. In this exemplary embodiment, resonance body  20  has a circular cross section with a centrally situated recess  35 . Transducer element  23  is situated fully circumferentially on an outer peripheral surface  33  of resonance body  20  and has therefore a ring-shaped design. 
         [0043]      FIG. 5B  shows an additional specific embodiment of ultrasonic transducer system  18  which is shown in  FIG. 3A . Resonance body  20  has a circular cross section without a recess, i.e., is configured as a cylinder. In addition, a transducer element  23  is shown which has a first transducer element  50  and a second transducer element  52  which surround resonance body  20  fully circumferentially along lateral surface  26 . 
         [0044]      FIG. 5C  shows an additional specific embodiment of an ultrasonic transducer system  18 . According to this specific embodiment, resonance body  20  has a ring-shaped design, as is described for example with reference to  FIG. 3B , and transducer element  23  has ring-shaped design, as is described for example with reference to  FIG. 5A  or  FIG. 5B . In this case, transducer element  23  is situated in recess  35  of resonance body  20  and contacts the latter on its inner peripheral surface  39 , which is a peripheral surface of recess  35 . It is possible that transducer element  23  is not ring-shaped as shown, but instead forms a cylindrical solid body. 
         [0045]      FIG. 5D  shows an additional possible specific embodiment including a resonance body  20  having a ring-shaped diameter on the level of transducer element  23 , transducer element  23  being situated in a recess  35 ′ and coupled partially circumferentially to resonance body  20 , more exactly to inner peripheral surface  39  of lateral surface  26  of resonance body  20 . Transducer element  23  includes a first transducer element  50  and a second transducer element  52  which are spaced at a distance from one another by a clearance  54 . Of course, it is possible that more than two transducer elements  23  are situated in such a way. 
         [0046]    The present invention is not limited to the exemplary embodiments described here and the aspects highlighted therein. Rather, within the range indicated by the claims, a plurality of variations is possible which lie within the scope of those skilled in the art.