Patent Publication Number: US-2021173062-A1

Title: Assembly for a motor vehicle with an ultrasonic sensor and with a damping element that comprises reinforcing elements and also a device

Description:
The present invention relates to an assembly with an ultrasonic sensor for a motor vehicle that is designed for concealed installation in a cladding part of the motor vehicle. The ultrasonic sensor comprises a membrane capable of oscillation for transmitting and/or receiving ultrasonic signals. Ultrasonic signals can be transmitted to the cladding part by means of the membrane. The ultrasonic sensor comprises a damping element that is arranged around a longitudinal axis of the membrane, so that oscillations of the cladding part can be attenuated when in the installed state. The invention further relates to a device with an assembly. 
     In order to enable an improved function of ultrasonic sensors with concealed installation in terms of the oscillation time and decay time, it is necessary that the oscillation energy that is introduced into the surrounding vehicle structure by the ultrasonic sensor is attenuated as effectively as possible over the entire operating temperature range. Very different types of damping materials or damping concepts are already known in this respect. Usual materials include for example bitumen, heavy foils, high-polymer materials or buty rubber. In the case of the materials just mentioned, it has been found that an improved attenuation is associated with a narrower operating range in terms of the temperature and frequency. Butyl rubber for example has a very high damping effect in the ultrasonic range over a wide temperature range. It is, however, disadvantageous here that at temperatures above room temperature (approx. 21° C.) the butyl rubber becomes increasingly soft. The consequence of this is that the oscillation energy cannot penetrate into the full depth of the damping material, but is only effective in the layers that bound the bodywork component. 
     US 2017/0059697 A1 discloses an ultrasonic sensor assembly with concealed ultrasonic sensor. A coupling element is arranged between the ultrasonic sensor, in particular the membrane, and the interior surface of the cladding part. The coupling element can comprise a matrix material that is reinforced with a filler. The ultrasonic sensor assembly further comprises a damping element that is placed against the interior surface of the cladding part. The damping element is arranged around the membrane and is formed of one material. 
     The object of the present invention is to provide an assembly and a device by means of which an improved attenuation of oscillations can be achieved over a large temperature range. 
     This object is achieved by an assembly and a device according to the independent claims. 
     One aspect of the invention relates to an assembly for a motor vehicle with an ultrasonic sensor. The ultrasonic sensor is designed for concealed installation at a cladding part of the motor vehicle. The ultrasonic sensor comprises a membrane capable of oscillation for transmitting and/or receiving ultrasonic signals. Ultrasonic signals can be transmitted to the cladding part by means of the membrane. The assembly comprises a damping element that is arranged surrounding a longitudinal axis of the membrane and around the ultrasonic sensor, wherein at least the membrane extends through a cutout of the damping element, wherein oscillations of the cladding part can be attenuated by means of the damping element when in the installed state. 
     The damping element comprises reinforcing elements. In the case for example of a temperature rise in the material of the damping element, and a consequent reduction in the stiffness of the material, deeper-lying regions of the damping element can thereby also be excited. The stiffer are the reinforcing elements, the earlier the oscillation energy can be introduced into the whole of the damping element. In particular, the dead-time of the ultrasonic sensor can thereby be reduced and at the same time an improved attenuation of oscillations can be achieved over a large temperature range. 
     In particular, the damping element comprises a basis material and the reinforcing elements are formed of a material that is different from the basis material. The reinforcing elements are in particular contained in the basis material. It is furthermore in particular provided that unwanted oscillations of the cladding part can be attenuated in the installed state. In other words, by means of the ultrasonic sensor, the ultrasonic signals that are transmitted from the ultrasonic sensor are thereby transmitted efficiently through the cladding part to the air, while the unwanted oscillations of the cladding part, in particular following the transmitting process of the ultrasonic sensor, are better damped. The settling time of the cladding part, and thereby of the ultrasonic sensor, in particular the membrane, can thereby be reduced, so that the dead time of the ultrasonic sensor can also be reduced. The dead time of the ultrasonic sensor refers in particular to the time that is required, following the transmitting process, for the ultrasonic sensor to be ready to receive. 
     Preferably the ultrasonic sensor comprises a coupling element that is separate from the damping element, by means of which the ultrasonic signals can be better transferred from the membrane to the cladding part. The coupling element is in particular arranged between the membrane and the cladding part. The coupling element and the damping element are different components of the assembly, and differ from one another in particular both in their installation position within the assembly as well as in the way that they function. The damping element is in particular arranged overlapping the membrane axially. It can be provided that the damping element is arranged encompassing the membrane at the outer perimeter of the membrane at a predefined distance around the longitudinal axis. The coupling element is designed in the form of a plate or disc, and is in particular arranged at the membrane at its face. The coupling element in particular does not comprise a cutout, and does not overlap the membrane axially. 
     According to one advantageous form of embodiment, the reinforcing elements can be distributed homogeneously in the damping element. The oscillation energy can thereby be introduced better into the whole damping element, and the deeper-lying regions of the damping element can also be reached better, so that an improved attenuation of the oscillations can be achieved. 
     It has furthermore been found advantageous if the damping element comprises hollow spheres as reinforcing elements. The hollow spheres exhibit a higher stiffness than the damping element, and can thus absorb the oscillations better. It is thereby in particular possible that the ultrasonic sensor can be used over a large temperature range, since the oscillation energy, in particular the unwanted oscillations, can be passed on better to the hollow spheres, and the damping element can thus dampen these oscillations better. 
     It is also advantageous if the damping element comprises fibres as reinforcing elements. In particular, the oscillation energy can be distributed better in the whole damping element through the introduction of fibres. The deeper-lying regions of the damping element can thereby also be reached by means of the transfer of the oscillation energy to the fibres. The process of introducing fibres into the damping element is, furthermore, very simple, since the fibres can be taken into consideration during the manufacture of the damping element. 
     It has further been found advantageous if the damping element comprises glass fibres and/or ceramic fibres and/or basalt fibres and/or mineral fibres and/or stainless steel fibres and/or aluminium fibres and/or plastic fibres as reinforcing elements. The above-mentioned fibres exhibit in particular a high modulus of elasticity over a wide temperature range, which means that these materials exhibit a high stiffness. The oscillation energy can thereby be better guided even into the deeper-lying regions of the damping element, and an improved attenuation of the oscillations thereby realized over a large temperature range. 
     It is also advantageous if the reinforcing elements exhibit a coefficient of elasticity greater than 1000 N/mm 2 . The reinforcing elements thereby exhibit a higher stiffness than the damping material, whereby the oscillations can be attenuated better. 
     According to a further advantageous form of embodiment, the basis material of the damping element can be formed of butyl rubber. Butyl rubber has in particular a very high damping effect in the ultrasonic range over a wide temperature range. As a result of the form of embodiment of the damping elements of butyl rubber, an improved attenuation of the oscillations thus can already be achieved over a high temperature range. 
     It has furthermore been found to be advantageous if the damping element with the reinforcing elements provides an attenuation at least of −250 dB, in particular for structure-borne sound waves in the ultrasonic frequency range over a temperature range from −30° C. to +90° C. Since the ultrasonic sensor is in particular designed for motor vehicles, and motor vehicles in particular are subject to this temperature range, it is advantageous if the damping element and the reinforcing elements exhibit a high attenuation in this temperature range. In particular, the attenuation in the present case is at least −250 dB, so that the oscillations, in particular the unwanted oscillations, of the cladding part can be better reduced. The ultrasonic sensor can thereby be better operated over the temperature range from −30° C. to +90° C., so that an improved resolution of the ultrasonic signals of the ultrasonic sensor can be achieved with a lower dead time of the ultrasonic sensor. 
     According to a further advantageous exemplary embodiment, at least the shape of the reinforcing elements and/or the position of the reinforcing elements in the damping element are matched to a resonant frequency of the ultrasonic sensor. The shape of the reinforcing elements and/or the position of the reinforcing elements, as well as the number of the reinforcing elements, in the damping element are in particular designed in such a way that a maximum attenuation occurs at the resonant frequency of the ultrasonic sensor. Since the ultrasonic sensor in particular, and in particular the transmitted ultrasonic signals, and the cladding part are matched to the resonant frequency, it is in particular advantageous if the shape of the reinforcing elements and/or the position of the reinforcing elements in the damping element are also matched to the resonant frequency. In the resonant frequency range in particular, an improved attenuation of those oscillations that are unwanted can thereby be achieved, so that these oscillations can be attenuated over a predetermined temperature range. 
     It is furthermore advantageous if the cutout of the damping element is annular in shape. The damping element can thereby in particular be arranged around the membrane, whereby the unwanted oscillations can be attenuated better with respect to the membrane, so that the dead time of the membrane after the transmitting process until the receiving process, and after the receiving process until the transmitting process, can be attenuated better. The unwanted oscillations can thereby be attenuated for the membrane in particular. 
     It has furthermore been found to be advantageous if the ultrasonic sensor comprises at least one holding element with which the ultrasonic sensor can be installed at the cladding part in a concealed manner. The ultrasonic sensor can thereby be arranged at the cladding part and decoupled from oscillations of the cladding part. The unwanted oscillations are thus transferred from the cladding part to the damping element, whereby the ultrasonic sensor, in particular the membrane, is decoupled from these oscillations, whereby an improved operation can be realized. 
     A further aspect of the invention relates to a device for a motor vehicle. The device comprises an assembly in accordance with one of the preceding aspects and a cladding part for a motor vehicle and at least one ultrasonic sensor. The ultrasonic sensor is arranged in a concealed manner at the cladding part, so that the ultrasonic sensor is arranged for the transmission of ultrasonic signals through the cladding part and/or for the reception of echo signals through the cladding part. 
     Yet another further aspect of the invention relates to a motor vehicle with a device. The motor vehicle is embodied in particular as a passenger motor vehicle. 
     Advantageous forms of embodiment of the assembly are to be seen as advantageous forms of embodiment of the device as well as of the motor vehicle. 
     Further features of the invention emerge from the claims, the figures and the description of the figures. The features and combinations of features that are cited in the description above, and also the features and combinations of features that are cited in the description of the figures below and/or as shown in the figures alone, can be used not only in the respectively indicated combination but also in other combinations or on their own without departing from the scope of the invention. Embodiments of the invention that are not explicitly shown and explained in the figures, but emerge and are producible from the explained embodiments by virtue of self-contained combinations of features, are therefore also intended to be regarded as included and as disclosed. Embodiments and combinations of features that therefore do not have all the features of an independent claim as originally worded are also intended to be regarded as disclosed. Embodiments and combinations of features that go beyond or differ from the combinations of features set out in the back-references of the claims, should furthermore be considered to be disclosed, in particular by the embodiments set out above. 
    
    
     
       The invention will now be explained in more detail on the basis of preferred exemplary embodiments and with reference to the attached drawings. 
       In the figures: 
         FIG. 1  shows a schematic plan view of a motor vehicle with one form of embodiment of an assembly; 
         FIG. 2  shows a schematic side view of a form of embodiment of an ultrasonic sensor; 
         FIG. 3  shows a further schematic view of a form of embodiment of the assembly; 
         FIG. 4  shows a schematic perspective view of a form of embodiment of a damping element; and 
         FIG. 5  shows a temperature-attenuation diagram of one form of embodiment of the ultrasonic sensor. 
     
    
    
     The same reference signs are given in the figures to identify elements that are identical and have the same functions. 
       FIG. 1  shows a motor vehicle  1 . The motor vehicle  1  is designed in the present exemplary embodiment as a passenger car. The motor vehicle  1  comprises a driver assistance system  2 . An object  3  that is located in a surroundings  4  of the motor vehicle  1  can for example be acquired with the driver assistance system  2 . A distance between the motor vehicle  1  and the object  3  can in particular be determined by means of the driver assistance system  2 . 
     The driver assistance system  2  comprises at least one assembly  5 . The assembly  5  in turn comprises at least one ultrasonic sensor  5   a . The assembly  5  can also comprise further ultrasonic sensors  5   a . The ultrasonic sensor  5   a  comprises a transmitting device  6  by means of which at least one ultrasonic signal  8 , in particular a plurality of ultrasonic signals  8 , can be transmitted. The assembly  5  is arranged in the present case at a front region of the motor vehicle  1 . The assembly  5  can also be arranged in other regions, for example at a rear region or a side region of the motor vehicle  1 . The following example is thus not to be considered as conclusive, but serves purely for illustration. 
     The ultrasonic signals  8  can be transmitted with the transmitting device  6  within a predetermined acquisition range E, or a predetermined angular range, by means of a membrane  13  ( FIG. 3 ). 
     The assembly  5  furthermore comprises a receiving device  7  by means of which reflected ultrasonic signals can be received as echo signals  9  that were reflected from the object  3 , in particular via the membrane  13 . Echo signals  9  reflected from the object  3  can thus be received with the receiving device  7  as received signals. The assembly  5  can furthermore comprise a control device  10  that can for example be formed by a microcontroller and/or a digital signal processor. The driver assistance system  2  further comprises a control device  11  that can for example be formed by an electronic control unit (ECU) of the motor vehicle  1 . The control device  11  is connected to the assembly  5  for data transfer. The data transfer can for example take place via the data bus of the motor vehicle  1 . 
       FIG. 2  shows a side view of the ultrasonic sensor  5   a , which is suitable for concealed installation at a cladding part  15  ( FIG. 3 ). The ultrasonic sensor  5   a  comprises a coupling element  12  that lies against the cladding part  15 , by means of which ultrasonic signals  8  can be transmitted and/or received by the membrane  13  of the ultrasonic sensor  5   a . Ultrasonic signals  8  can be transferred to the cladding part  15  by means of the membrane  13  and of the coupling element  12 . The coupling element  12  is here formed in particular in the direction surrounding a longitudinal axis L of the membrane  13 . Latching elements R are further shown in  FIG. 2 , by means of which the ultrasonic sensor  5   a  can be held in particular at the cladding part  15 . The latching elements R are in particular designed at an outer side  23  of the ultrasonic sensor  5   a.    
       FIG. 3  shows a schematic side view of an example of an installed ultrasonic sensor  5   a , at least in partial components. The ultrasonic sensor  5   a  is arranged at a rear side  16  of the cladding part  15 . The cladding part  15  can in particular be designed as the bumper of the motor vehicle  1 . A damping element  17 , having in particular an annular form, is arranged next to the membrane  13  in a circular manner around the ultrasonic sensor  5   a . The damping element  17  is in particular arranged at the rear side  16 . The damping element  17  is in particular arranged surrounding the longitudinal axis L of the membrane  13  and around the ultrasonic sensor  5   a . The membrane  13  extends through a cutout  31  of the damping element  17 . The cutout  31  can here in particular be annular in form. A transfer of energy, in particular sound energy, of the ultrasonic sensor  5   a  can thereby be attenuated in other regions of the cladding part  15 . By means of the damping element  17 , furthermore, oscillations from the cladding part  15  to the ultrasonic sensor  5   a  can be attenuated. 
     The coupling element  12  is in particular arranged between the membrane  13  and the cladding part  15 . The coupling element  12  and the damping element  17  are different components of the assembly  5 , and differ from one another in particular both in their installation position within the assembly  5  as well as in the way that they function. The damping element  17  is in particular arranged overlapping the membrane  13  axially. It can be provided that the damping element  17  is arranged encompassing the membrane  13  at the outer perimeter of the membrane  13  at a predefined distance A around the longitudinal axis L. The coupling element  12  is in particular designed in the form of a plate or disc, and is in particular arranged at the membrane  13  at its face. The coupling element  12  in particular does not comprise a cutout  31 , and does not overlap the membrane  13  axially. 
     The ultrasonic sensor  5   a  is structurally joined to the cladding part  15  in particular by way of at least one holding element. The holding elements can for example be joined to the latching elements R. It is furthermore possible that the holding elements have further damping elements at the end at which they are joined to the ultrasonic sensor  5   a . The further damping elements can in particular be provided so that oscillations of the ultrasonic sensor  5   a  are transmitted to the cladding part  15  to a reduced extent, or that oscillations of the cladding part  15  are prevented at the ultrasonic sensor  5   a . It can furthermore in particular be provided that the ultrasonic sensor  5   a  comprises a thick-walled region  21  and a thin-walled region  22 . 
     In the thin-walled region  22  the membrane  13  can in particular comprise a piezo element  24  that can be electrically driven, and the membrane  13  can be made to oscillate through the electric drive of the piezo element  24 . The ultrasonic signals  8  can in particular be generated thereby. The echo signals  9  can, furthermore, be received via the membrane  13  and the piezo element  24  and converted into electric signals. 
     It is provided that the damping element  17  comprises reinforcing elements  25 . In particular, the damping element  17  is made of a basis material and the reinforcing elements  25  are formed of a material that is different from the basis material. The reinforcing elements  25  are here in particular contained in the basis material. The basis material of the damping element  17  can be formed for example of butyl rubber. The reinforcing elements  25  can in particular exhibit a coefficient of elasticity greater than 1000 N/mm 2 . The reinforcing elements  25  in the following form of embodiment are designed as hollow spheres  26 . By means of this form of embodiment it is possible that the oscillation energy of the cladding part  15 , in particular after the transmitting process, can be better attenuated, since the reinforcing elements  25  raise the stiffness of the damping element  17  and thus guide the oscillations of the cladding part  15  into deeper regions of the damping element  17 , whereby an improved attenuation, in particular over a large temperature range, is made possible. The dead time of the ultrasonic sensor  5   a  can thereby be reduced, so that an improved operation of the ultrasonic sensor  5   a  is enabled over a large temperature range. 
     A device preferably comprises the assembly  5 . The device is in particular formed with the cladding part  15  for the motor vehicle  1 , wherein the ultrasonic sensor  5   a  is arranged in a concealed manner at the cladding part  15 , so that the ultrasonic sensor  5   a  is arranged for the transmission of ultrasonic signals  8  through the cladding part  15  and/or for the reception of echo signals  9  through the cladding part  15 . 
       FIG. 4  shows a schematic perspective view of a form of embodiment of the damping element  17 . The reinforcing elements  25  in the present form of embodiment are distributed, in particular homogeneously, in the damping element  17 . In the present exemplary form of embodiment, the damping element  17  comprises fibres  27  as reinforcing elements  25 . The damping element  17  can for example comprise glass fibres and/or ceramic fibres and/or basalt fibres and/or mineral fibres and/or stainless steel fibres and/or aluminium fibres and/or plastic fibres as fibres  27  as reinforcing elements  25 . The damping element  17  in the present case comprises in particular a covering layer  28  by means of which the damping element  17  can be better protected, in particular from environmental influences. 
     In particular it is provided that at least the shape of the reinforcing elements  25  and/or the position of the reinforcing elements  25  in the damping element  17  are matched to a resonant frequency of the ultrasonic sensor  5   a . In particular, the damping element  17  and the reinforcing elements  25  are so designed that a maximum attenuation occurs at the resonant frequency of the ultrasonic sensor  5   a.    
       FIG. 5  shows a temperature-attenuation diagram of an exemplary form of embodiment of the damping element  17 . The temperature, in particular the ambient temperature, is given in ° C. on the abscissa A, and the attenuation is given in db on the ordinate O. The line  29  here in particular shows the attenuation curve of a damping element without reinforcing elements  25 . The line  30  shows the attenuation curve over the temperature range of the damping element  17  with the reinforcing elements  25 . The diagram shown in  FIG. 5  is purely exemplary, and not to be thought of as conclusive. It serves merely to illustrate the idea according to the invention. It is in particular to be seen in the following diagram that the line  30 , which describes the damping element  17  with the reinforcing elements  25 , exhibits a very high attenuation, in particular in the range between +15° C. and +50° C. An improved attenuation is to be seen, in particular in comparison with the line  29 . As  FIG. 5  shows, an improved attenuation of the cladding part  15  is to be observed here, in particular at the ambient temperatures from +15° C. to +50° C. The attenuation depends in particular on the reinforcing elements  25 , so that it is also possible that an altogether better attenuation of the damping element  17  with the reinforcing elements  25  is to be observed in comparison with simply a damping element without reinforcing elements  25  in a temperature range from −30° C. up to +90° C. 
     It is in particular provided that the damping element  17  and the reinforcing elements  25  exhibit an attenuation of −250 db over a temperature range from −30° C. up to +90° C.