Abstract:
The invention relates to an Ultrasound Sensor, especially for a vehicle and the passenger compartment thereof, comprising a can-shaped housing, a housing base, a housing closure and a sensor element arranged at the base inside the housing, and in the area of the housing closure there is arranged a contact device which is attachable, in locally fixed fashion, inside housing; the contact device presenting, in the direction of the longitudinal axis, a penetrating recess and being connected, in electrically conductive fashion, in at least one contact point with at least one electrode of the sensor element by means of thick-stranded wire. The invention also relates to a method for producing the Ultrasound Sensor.

Description:
BACKGROUND OF THE INVENTION 
     The subject invention is directed to the art of ultrasound sensors and their manufacture and, more particularly, to a manufacturing method and ultrasound sensor apparatus of the type particularly adapted for use in the passenger compartments of motor vehicle. 
     Ultrasound sensors of the type under consideration are commonly formed to include a cup-shaped housing defining an interior space and a base upon which a piezo element is glued or otherwise attached. Vibrations of the cup-shaped bottom or base of the housing are transferred directly to the piezo element. The electrodes of the piezo element extend from the base of the cup-shaped housing to the outside via soldered or welded electrically conductive wires or lines. The cup-shaped housing is typically sealed off by means of a pourable sealing compound, such as a synthetic resin or plastic material. The electrically conductive lines extend to the outside of the ultrasound sensor through the sealing compound and serve for connection between the piezo element at the base of the housing and associated external electronics. By theses means, it is possible to evaluate the vibration behavior of the piezo element including the characteristic power curve emitted from the piezo element. 
     One problem with piezo sensors of the type described above, however, is the need for tension relief in the electrically conductive wires. More particularly, since the cup-shaped housing member is sealed off by a pourable sealing compound, the electrically conductive lines extending from the piezo element to the outside of the cup-shaped housing become fixed in space within the housing by mechanical interaction with the surrounding sealing compound. The locking in place of the electric signal lines has an adverse effect on the sensitivity and accuracy in the representation of the recorded sound waves. Sensors constructed according to the above with electric signal lines extending through a sealing compound typically do not satisfy the requirements of greater sensitivity and accuracy in the representation of recorded sound waves. 
     It would be desirable, therefore, to provide an ultrasound sensor and method for manufacturing same which provides an improved recording of sound waves or ultrasound waves and uses a simple and cost-effective construction. It is further desirable to provide an ultrasound sensor and method for manufacturing same which converts sound waves or ultrasound waves into current response signals. 
     SUMMARY OF THE INVENTION 
     The subject invention provides an ultrasound sensor including a can-shaped housing, a sensor element arranged in the can-shaped housing, a contact device adapted for connection with the can-shaped housing, the contact device defining a central opening, and at least one electrically conductive wire connecting an electrode of the sensing element with a contact point on the contact device through the central opening. 
     In accordance with a further aspect of the invention, a method for manufacturing ultrasound sensors is provided and includes the steps of attaching a sensor element to the base of an outer housing, attaching a contact device onto a portion of the housing adapted to receive the contact device, and electrically connecting the contact device with the sensor element through a recess provided in the contact device using a thick-stranded electrically conductive wire. 
     As can be seen from the forgoing, a primary object of the invention is the provision of an improved ultrasound sensor which enables a thick flexible wire-bond connection between the electrode of a piezo element disposed within the sensor housing and a contact device. The contact device is fastened locally within the housing and includes a central aperture or opening for receiving the electrically conductive wire braid. Thereby, it is possible to assure a contact point at the piezo element which is reproducibly exactly defined in its position relative to the piezo element structure. 
     A further object of the invention is that the contact point beneficially has less mass in contrast to contact points in known prior art piezo elements. Accordingly, the present invention utilizes a pre-determined connection point between the conductive wire and the piezo element so that the lowest possible influence upon the vibrational behavior of the piezo element is attained. The pre-determined connection point between the electrically conductive wire and the piezo element is easily reproducible and can be employed as a contact point with high accuracy. 
     A further object of the invention is a reduction in the negative influence on the vibrational behavior of the piezo element due to the lower mass of the connection point relative to known contact methods practiced in the prior art ultrasound sensor technology. As a result of the thick flexible wire and connection point selection according to the invention, the lowest possible change in the mass effect, and thus in the vibrational behavior, of the piezo element is attained. 
     A yet further object of the invention is to ensure tension relief of the electrically conductive lines extending between the contact device and the piezo sensor element. More particularly, the ultrasound sensor construction provided in accordance with the present invention enables a device without the need of additional pourable sealing compound within the can-shaped housing. Thereby, tension relief of the electrically conductive lines extending between the piezo sensor element and the contact device is assured. 
     Still other advantages and benefits of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may take physical form in certain parts and arrangements of parts, the preferred embodiments of which will be described in detail in this specification and illustrated in the accompanying drawings which form a part hereof, and wherein: 
     FIG. 1 is a perspective view in partial cross section of an ultrasound sensor formed in accordance with the present invention; 
     FIG. 2 is an exploded perspective view of the ultrasound sensor shown in FIG. 1 in partial cross section and in a partial state of disassembly before installation of the lid onto the housing jacket; 
     FIG. 3 is a perspective view of an electrically conductive pressed screen portion of a contact device used in the ultrasound sensor shown in FIGS. 1 and 2; 
     FIG. 4 is a perspective view of the pressed screen member shown in FIG. 3 subsequent to an initial manufacturing work step prior to assembly of the subject ultrasound sensor illustrated in FIGS. 1 and 2; 
     FIG. 5 is a perspective view of a contact device used in the ultrasound sensor of the present invention shown in FIGS. 1 and 2 and incorporating the pressed screen member shown in FIG. 4; 
     FIG. 6 is a cross sectional view of the ultrasound sensor housing jacket illustrated in FIGS. 1 and 2; and 
     FIG. 7 is a top elevational view of the housing jacket shown in FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings wherein the showings are for the purposes of illustrating the preferred embodiments of the invention only and not for purposes of limiting same, the figures illustrate an ultrasound sensor formed in accordance with the present invention and method for making same, the sensor including a cup-shaped or can-shaped housing  1  including a housing base  3 , and a housing jacket  5  shaped as a hollow cylinder. Preferably, the housing jacket  5  is can-shaped but may be formed in any other configuration as desired such as, for example, with straight or tapered walls having round or polygonal cross-sections which may have bottoms and/or lids extending in straight or oblique panes toward each other. 
     With particular reference to FIGS. 1 and 2, a sensor element  7  is attached at the interior bottom  3  of the housing  1  in a locally fixed and electrically conductive fashion. Preferably, the sensor element  7  is a piezo ceramic sensor element. A preferred sensor element  7  is of a plate condenser type construction in design and presents, therefore, at its underside, a lower electrode which is connected with the housing  1 . The lower electrode of the sensor element  7  consists of an electrically conductive material such as, for example, aluminum. The upper side of the sensor element includes an upper electrode  15  arranged in parallel with the lower electrode (not shown) of the sensor in contact with the base of the housing. Although the disk-shaped sensor element shown in the FIGURES has a circular shape, other shapes such as, for example, oval, polygonal, or any other shape sensor can be used. Both the upper electrode  15  and the lower electrode (not shown) can be formed by a conductive layer applied by the piezo ceramics by a vacuum evaporation process for vacuum depositing silver, gold, or other materials. 
     With continued reference to FIGS. 1 and 2, the upper electrode  15  is electrically joined with the contact surface  19  of a contact device by use of a thick-stranded flexible electrically conductive wire  17 . As shown, the contact device  9  is arranged in the housing container in the area of the opposing closure. A lid  11  preferably in the form of a disk, is arranged above the contact device  9  as shown. The upper area of the housing jacket  5  forms a flange in response to a force actuated from above the housing jacket during the manufacturing process so that the flange formed by the housing jacket presses the contact device  9  against a straight shoulder  20  (FIG. 6) formed on the inner wall of the housing jacket. A plug receptacle area  13  is formed on the outer surface of the lid  11  for electrode connection of the ultrasound sensor to associated electronic devices. Preferably, the plug receptacle area  13  is formed as a connecting piece. 
     As can be seen, the plug receptacle area  13  has a generally rectangular layout (FIG. 1) with rounded-off corners (FIG. 2) and a height which is selected to adequately mechanically fix therein an insertable associated plug. It is to be appreciated, however, that the plug receptacle area  13  can also include a locking or counter-locking element which assures a mechanical connection within an inserted plug having a corresponding opposite internatable locking means. 
     As shown in FIG. 1, the interior of the plug receptacle area  13  includes a longitudinally extending set of first and second contact pins  21 ,  23 . The first and second contact pins  21 ,  23  form part of the contact device member  9  to be described below. As shown best in FIG. 2, the upwardly pointing contact pins  21  and  23  extend along the longitudinal axis of the housing and penetrate through the lid  11  in the area of the plug receptacle area  13  by means of a set of recesses formed to closely surround the outer surface of the contact pins. It is, however, also to be appreciated that the lid  11  could be formed to have a larger opening so that a portion of the contact  9  is received within the plug receptacle area  13 , the portion of the contact device surrounding the contact pins  21  and  23  in this area. Further connection of the contact device  9  is provided in a marginal region of the contact device  9  by providing a round hole  37  (FIG.  5 ), which is in alignment with a recess  22  (FIGS. 6 and 7) in the shoulder of the housing jacket  5  and extending in a longitudinal direction A and formed as bore opening  22 . As shown best in FIG. 2, the contact device  9  is connected with the housing jacket  5  in an electrically conductive fashion using a rivet  27 . The rivet  27  extends into the recess  22  of the housing jacket  5  to mechanically and electrically connect the contact device  9  with the outer housing jacket  5 . 
     FIGS. 3-5 illustrate the preferred method of manufacturing the contact device  9  using individual components in sequential work steps. Turning first to FIG. 3, an electrically conductive pressed screen member  31  is provided. As shown, first and second contact pins  21 ,  23  are formed by the pressed screen  31  and arranged in a parallel relationship relative to each other. The contact pins are initially mechanically connected by means of a bridge portion  33  extending between opposite quarter circle segments  32 ,  34  of the pressed screen  31 . As shown, the quarter circle segments  32 ,  34  are substantially in the shape of right-angled triangles. A U-shaped recess  35  is provided in the first quarter circle segment  32 . As shown, the U-shaped recess is open in the direction of the circumference of an imaginary circle  39 . A circular partial region  41  is arranged along the circumference of the circle  39  and connected with the second quarter circle segment  34 . 
     FIG. 4 illustrates the pressed screen member  31  after the first and second contact pins  21 ,  23  are bent in accordance with an initial work step in the manufacture of the subject ultrasound sensor. As illustrated, the contact pins  21  and  23  are bent vertically in an upward direction from a plane defined by the pressed screen member  31 . Preferably, as illustrated, the contact pins  21  and  23  extend in a direction substantially perpendicular with the plane defined by the pressed screen portion  31 . 
     Next, in FIG. 5, a subsequent work step includes the pouring or a spraying of a synthetic material or synthetic resin onto the pressed screen member  31 . The thus produced contact device  9  has a disk-shaped layout which is perforated by a central opening or a recess  25 . Preferably, the recess  25  is outside of the region of the poured pressed screen  31 . More particularly, the recess  25  provides a non-conductive path to the central opening of the contact device  9 . The outer synthetic material or synthetic resin poured or sprayed on the electrically conductive pressed screen  31  isolates the pressed screen  31  from the opening  25 . Preferably, the opening  25  has a half-moon or even three-quarter moon shape layout which is surrounded on its outer sides by an evenly thick circular ring. As shown, the straight edge portions of the half-moon recess basically correspond with the straight edge portions of the circular segments  32 ,  34  and by the straight lines facing the recess  25  and the poured sealing compound facing the same. 
     With continued reference to FIG. 5, it is to be noted that the contact device  9  includes a hole  37  defined therein in alignment with the recess  35  of the pressed screen member  31  shown in FIGS. 2 and 3. By using the round hole  37  described above, the contact device  9  is connected in an electrically conductive fashion by means of a rivet  27  which engages with the aligned recess  22  (FIG. 6) in the shoulder of the housing jacket  5 . 
     Preferably during the manufacturing process, the bridge  33  in the contact device  9  is separated during the synthetic resin pouring process by means of a special tool so that the second contact pin  23  is connected solely with the circular segment  35  and the first contact pin  21  is connected solely with the circular segment  34  and the partial circular edge piece  41 . In that way, the first and second contact pins  21 ,  23  in the circular segments  32  and  34 , respectively, are both mechanically and electrically separated within the contact device  9  (FIG.  5 ). It is to be appreciated, however, that the separation of the bridge member  33  can also be performed before or after the synthetic resin pouring process. 
     With reference once again to FIG. 2, the lower electrode of the sensor element  7  is connected to the housing base  3  perferably using an electrically conductive glue. In that way, the lower electrode of the sensor element is connected with the circular segment  32  of the pressed screen member  31  in the region of the recess  35  through the housing bottom  3 , the housing jacket  5 , and the rivet  27 . On the other hand, the first contact pin  21  is isolated relative to the housing  1  by means of the poured resin layer surrounding the pressed screen  31 . The first contact pin  21  is electrically connected to only the circular segment  34  and to the circular partial edge  41 . The top surface of the partial edge  41  forms a contact surface  19  best shown in FIGS. 1,  2 , and  5 . A thick-stranded flexible bond wire  17  (FIGS. 1 and 2) connects the upper electrodes of the sensor element  7  with the contact surface  19  and in turn to the first contact pin  21  through the circular partial region  41 . Again, as noted above, the bridge portion  33  is separated to electrically isolate the first and second circular segments  32 ,  34  from each other and thereby separating the first and second contact pins  21 ,  23 . 
     As shown in FIG. 2 an attenuator foam  29  is selectively positioned in the sensor housing  1  in the space between the bottom  3  and up to the shoulder member  20  or up to the contact device  9  positioned on the shoulder edge  20 . The attenuator foam  29  is selected to modify the vibration behavior in the sensor in a pre-determined manner such as, for example, to provide increase broad-band or bandwidth, less after-vibration or increased dampening, and the like. Additionally, the attenuator foam contributes to the position stabilization of the braided bond wire  17  to reduce the risk of unwelcome tearing and/or breaking of the bond wire  17 . 
     With reference once again to the preferred manufacturing method, subsequent to the formation of the contact device and gluing the sensor element  7  onto the bottom  3  of the housing  1 , the contact device  9  is installed on a shoulder lip  20  on the interior side of the housing jacket  5  with the round hole or bore  37  of the contact device  9  aligned with the recess  22  provided in the shoulder of the housing. As noted, the sensor element  7  is glued on the bottom  3  of the housing using an electrically conductive specialty glue. Alternatively, it is possible to utilize a non-conductive glue such as, for example, an instant glue, whereby electrical contact is established, due to the roughness of at least one of the surfaces to be contacted via the tips or peaks of the rough surface which perforate the thin layer of glue. In any case, subsequently or simultaneously, the contact pin  23  of the contact device  9  is electrically connected with the housing  1  using a rivet  27 . In that way, the contact pin  23  is electrically connected with the lower electrode of the sensor  7  via the circular segment  32 , the rivet  27 , the outer housing jacket  5  and the electrically conductive specialty glue. 
     In another manufacturing step, the contact surface  19  of the contact device  9  is bonded using a thick-stranded wire with the upper electrode  15  of the sensor element  7 . The recess  25  or opening formed in the contact device  9  is advantageously used to enable the bond wire  17  to connect the upper electrode  15  in a first plane and with the contact surface  19  in a second plane. Overall, the bond wire  17  extends in a longitudinal direction between the plane of the contact surface  19  and the plane of the upper electrode  15 . 
     After the upper electrode  15  is connected with the contact surface  19  using the bond wire  17 , attenuation foam  29  is selectively added within the housing jacket  5  to exercise a desired effect on the vibrational characteristics of the ultrasound sensor. As noted above, the attentuation foam  29  is not necessary, but is used selectively when vibrational characteristics are to be controlled. 
     Next in the manufacturing process, the lid member  11  is inserted into the upper end of housing jacket  5  and, thereafter, an upper marginal area of the housing jacket  5  protruding above the lid  11  is bent downwardly by means of an associated crimping or a forming tool in the direction toward the center of the housing. In this manner, a flanging is created as best shown in FIG.  1 . The flanging of the upper area of the housing jacket  5  mechanically secures the lid member  11  in contact with the contact device  9  which in turn rests on the shoulder  20  of the housing jacket  5 . 
     As is apparent in FIG. 1, a plug receptacle  13  is formed in the upper region of the lid  11 . The first and second electrical contact pins  21  and  23  extend from below and into a receptacle region of the plug  13 . Thereby, the first and second contact pins  21 ,  23  can be selectively connected to associate electronic circuitry using a plug having similar mechanical characteristics. 
     It is to be appreciated that the preferred contact pins  21  and  23  described above and illustrated in the accompanying drawings can be formed as contact sockets without departing from the spirit and scope of the present invention. Additionally, the present invention contemplates a receptacle region  13  to be formed as a jack-type member, a plug-type member or as any other connection type. 
     The invention has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon a reading and understanding of this specification. It is intended to include all such modifications and alterations in so far as they come within the scope of appended claims or the equivalence thereof.