Abstract:
An ultrasonic sensor has an intermediate connection member for having electrical connection between an ultrasonic transducer and a circuit board . A connection pin of the transducer supported by the intermediate connection member is prevented from being damaged when an excessive pressing force on the transducer pushes the transducer into a case, because a deformation of the connection member releases the force without damaging the connection between the transducer and the circuit board.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based on and claims the benefit of priority of Japanese Patent Application No. 2006-107291 filed on Apr. 10, 2006, the disclosure of which is incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to an ultrasonic sensor for use in a vehicle. 
       BACKGROUND INFORMATION 
       [0003]    In recent years, an ultrasonic sensor is widely used for detecting objects, and the ultrasonic sensor having an ultrasonic transducer is proposed in, for example, Japanese patent document No. JP-A-2004-159351. The sensor disclosed in the above reference includes an ultrasonic transducer having a piezoelectric element pasted on a bottom of a cylindrical housing of the transducer and a case for housing the transducer that is inserted from an opening formed thereof. The piezoelectric element is electrically coupled with a circuit board in the case by a lead. 
         [0004]    The lead for coupling the piezoelectric element with the circuit board is replaced with a connection pin, mainly due to an increasing demand for improvement of workability. Therefore, an alternative structure for electrically coupling the piezoelectric element with the circuit board by using a connection pin with an insulating base disposed on the bottom of the housing with the connection pin piercing therethrough is proposed, for example, in Japanese patent documents No. JP-A-H08-130795, and No. JP-A-H11-87491. 
         [0005]    The ultrasonic transducer is conventionally disposed on a case with a vibration absorbing material pasted thereon for preventing the vibration to be transmitted to the case when the ultrasonic wave is generated by the transducer. That is, an outer surface of the transducer and a bottom of it are covered by the vibration absorbing material for preventing the vibration to be transmitted to an opening of the case. 
         [0006]    However, the elasticity of the absorbing material may lead to a deformation of the absorbing material, and thereby causing a break of the connection pin due to, for example, a dislocation of the transducer in an insertion direction into the case by a pressing force from outside. That is, the electrical coupling between the connection pin and the circuit board is broken due to the pressing force for warping the connection pin in the insertion direction for causing a reaction force at a soldered portion of the connection pin. 
         [0007]    Particularly, when an additional foaming member is disposed under the base of the housing, the pressing force on the transducer causes a larger dislocation of the transducer, and the problem described above may become more distinctive. 
       SUMMARY OF THE INVENTION 
       [0008]    In view of the above and other problems, the present invention provides an ultrasonic sensor that prevents unintended breakage of electrical connection between a piezoelectric element and a circuit board when an ultrasonic transducer in the sensor is pushed into a case. 
         [0009]    The ultrasonic sensor of the present disclosure includes an ultrasonic transducer in a housing with a bottom and a cylindrical body, a cylindrical elastic member that covers an outer peripheral surface and a connection pin pull-out surface of the transducer, a hollow case having an opening through which the transducer is inserted therein, a joining pin disposed in an exposing manner in a hollow space in the case, and a circuit board disposed in the hollow space of the case in an electrically coupled condition with the piezoelectric element. In the above structure, the bottom of the housing has a piezoelectric element disposed on an inside surface, and the piezoelectric element has a connection pin electrically coupled with the element with one end extending out of the housing. Further, the connection pin pierces a base that is disposed on the housing. In addition, the case holds the transducer with the elastic member disposed thereon in the opening. 
         [0010]    Further, an exposed portion of the joining pin is electrically coupled with the connection pin in the hollow space in the case, and the joining pin warps in an insertion direction when the connection pin is pressed in the insertion direction of the transducer into the opening. 
         [0011]    Furthermore, the electrically coupled condition of the circuit board with the piezoelectric element is achieved by an electrical coupling of the circuit board with the joining pin and the connection pin. 
         [0012]    In the above structure, the connection pin coupled with the circuit board indirectly through the joining pin allows an external force for pushing the transducer into the case to be released in deformation of the joining pin. In this manner, the electrical connection between the piezoelectric element and the circuit board is prevented from being damaged. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    Other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings, in which: 
           [0014]      FIG. 1A  shows a cross-sectional view of an ultrasonic transducer in an embodiment of the present disclosure; 
           [0015]      FIG. 1B  shows a bottom view of a housing of the ultrasonic transducer having a piezoelectric element in the embodiment; 
           [0016]      FIG. 1C  shows a bottom view of an ultrasonic transducer in the embodiment; 
           [0017]      FIG. 1D  shows a side view of an ultrasonic transducer in the embodiment; 
           [0018]      FIG. 2A  shows a cross-sectional view of an ultrasonic sensor in the embodiment; 
           [0019]      FIG. 2B  shows a bottom view of a case of the ultrasonic sensor in the embodiment; 
           [0020]      FIG. 3A  shows a perspective exploded view of the ultrasonic transducer in the embodiment; 
           [0021]      FIG. 3B  shows another perspective exploded view of the ultrasonic transducer in the embodiment; 
           [0022]      FIG. 4A  shows a bottom view of a cylindrical elastic body in the embodiment; and 
           [0023]      FIG. 4B  shows a side view of the cylindrical elastic body in the embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    Preferred embodiments of the present invention will now be described with reference to the accompanying the drawings. Like parts have like numbers in the embodiments 
       First Embodiment 
       [0025]    The ultrasonic sensor in a first embodiment is described in the following. The ultrasonic sensor in the present embodiment is used, for example, as a back sonar or a corner sonar when it is disposed on a bumper of a vehicle. 
         [0026]      FIGS. 1A to 1D  show illustrations of an ultrasonic transducer  10  in an ultrasonic sensor  100  in a first embodiment of the present disclosure. That is,  FIG. 1A  is a cross-sectional view,  FIG. 1B  is a bottom view of a housing  11 ,  FIG. 1C  is a bottom view, and  FIG. 1D  is a side view of the transducer  10 . The cross-sectional view in  FIG. 1A  is taken along IA-IA line in  FIG. 1C .  FIG. 1B  shows an illustration that the housing  11  has a piezoelectric element  12  disposed therein. 
         [0027]    The ultrasonic transducer  10  includes the housing  11  having a bottom in a cylindrical shape, the piezoelectric element  12 , the base  14  disposed in an opening of the housing  11  with a spacer  13 , and a connection pin  15  in an electrical connection with the piezoelectric element  12  on one end. The other end of the connection pin  15  pierces the base  14  to be extended toward an outside of the housing  11 . 
         [0028]    The housing  11  is made of a conductive material (a metal or an insulation material with a metallic coat formed thereon). The housing  11  has an inner space  16  formed therein. A bottom  11 a of the housing  11  has the piezoelectric element  12  being pasted on an inner surface. An outer surface of the bottom  11   a  is a vibration surface  11   b . In the present embodiment, the conductive material is an aluminum, and the vibration surface  11   b  is in a round shape. An upper side of the inner space  16  has a rectangular shape having respectively different length and width (corners of the rectangular shape are rounded) as shown in  FIG. 1B . The shape of the inner space  16  defines directivity of the transducer  10 , that is, respectively different directivities in a horizontal and a vertical direction. In this case, the directivity of the transducer  10  is wide in the horizontal direction and narrow in the vertical direction. 
         [0029]    The piezoelectric element  12  includes a piezo-ceramic element (e.g., lead zirconate titanate) having electrodes on both surfaces on a front and a back side (not shown in the figure), and one of the electrode on the surface is attached to the bottom  11   a  of the housing  11  by using, for example, a conductive adhesive. One of the electrodes is in electrical coupling with one of a pair of the connection pins  15  by using a lead  17   a , and the other electrode is pasted on the bottom of the housing  11  with the conductive adhesive to be coupled with the other one of the pair of the connection pins  15  after being coupled with a lead  17   b  through the housing  11  that is made of conductive material. The inner space  16  of the housing  11  is filled with a felt and a silicon in order from the piezoelectric element  12  side poured from a hole (not shown in the figure) disposed on the spacer  13  and the base  14  for controlling an unnecessary vibration transferred from the vibration surface to the connection pins  15 . 
         [0030]    The spacer  13  disposed between an opening of the housing  11  and the base  14  is an elastic body for controlling transfer of the unnecessary vibration on a cylinder  11   c  of the housing  11  caused by the vibration of the bottom  11   a  of the housing  11  to the base that holds the connection pins  15 . The spacer  13  is made of, for example, a silicone rubber. The spacer  13  used in the present embodiment may be omitted. 
         [0031]    The base  14  is made of an insulation material for having the connection pins  15  piercingly disposed therethrough, and is disposed around an outer surface on an opening side of the housing  11  with the spacer  13  interposed therebetween. The insulation material of the present disclosure is, for example, a synthetic material such as an ABS resin. Portions of the connection pins  15  are laid in the base  14  by using insert molding. In the base  14 , a protector portion  18  extends along a longitudinal direction of the connection pins  15  for protecting the pins  15 . The protector portion  18  protects a predetermined portion of the connection pins  15  extending toward an outside of the housing  11 . A single body of the protector portion  18  covers a pair of the connection pins  15 . 
         [0032]    Further, in the base  14 , a first marker  14 a is formed in a protruding manner in a protruding direction of the connection pins  15 . A tip end of the first marker  14   a , as shown in  FIGS.1C and 1D , partially protrudes from the outer surface of the base  14  in a radially outward direction. 
         [0033]    The connection pins  15  are, for example, mainly made of cupper, and has a thickness of 0.5 mm in diameter. In the present embodiment, the protector portion  18  and the connection pins  15  are positioned away from a center of the transducer  10  (i.e., the housing  11 ) because configuration of the respectively different directivities of the transducer  10  in the horizontal and vertical directions. 
         [0034]    The protector portion  18  may be separately formed from the base  14 , and may be attached on the base  14  by, for example, using an adhesive. Further, each of the pins  15  may be separately covered and protected. The pins  15  may be attached to a predetermined position of the base  14  and the protector portion  18  by using an adhesive instead of using insert molding. 
         [0035]    The ultrasonic transducer  10  includes a foamed elastic body  19  on the base  14  as a damper. The foamed elastic body  19  of the present disclosure is, for example, a foamed silicon. The connection pin  15  pierces the foamed elastic body  19 . The foamed elastic body  19  may be omitted. The housing  11 , the spacer  13 , the base  14 , and the foamed silicon  19  are attached to each other by using an adhesive (e.g., a silicon type adhesive) to form the transducer  10 . 
         [0036]      FIGS. 2A and 2B  show illustrations of the ultrasonic sensor  100  in  FIG. 1A  in the present embodiment. That is,  FIG. 2A  shows a cross-sectional view, and  FIG. 2B  shows a bottom view of a case  30  for housing a circuit board  20  of the sensor  100  taken from a reverse side of the case  30 . In  FIG. 2A , electrical components on the circuit board  20  are omitted for illustration purposes. 
         [0037]    The ultrasonic sensor  100  includes the ultrasonic transducer  10  and the circuit board  20  for applying voltage on the transducer  10  to generate the ultrasonic wave and for processing voltage induced by a reverse effect of the transducer  10 . The transducer  10  and the circuit board  20  are disposed in the case  30  that is made of synthetic resin. 
         [0038]    The case  30  has a guide portion  31  for positioning the pins  15  and the protector portion  18  relative to a connection portion of the circuit board  20 . the guide portion  31  is formed as a portion of the case  30 . 
         [0039]    The guide portion  31  is formed as a separator for separating the space in the case  30  to a space for the transducer  10  and a space for the circuit board  20 . The guide portion  31  has a positioning hole  31   a  for having the protector portion  18  inserted therein. The hole  31  a has a same shape as an outer shape of the protector portion  18  (e.g., an oval shape in the present embodiment), and has the same size or a slightly larger size than the protector portion  18 . By inserting protector portion  18  together with the connection pins  15  into the positioning hole  31   a  in the guide portion  31 , the transducer  10  is positioned relative to the case  30 , as well as the connection pins  15  of the transducer  10  relative to the circuit board  20 . 
         [0040]    Further, the guide portion  31  has another hole separately from the positioning hole  31   a . The another hole is designated as a piercing hole  31   b , and the hole  31   b  is a hole for an engagement with a hook  33   d  of a cylindrical elastic body  33  that is described later. 
         [0041]    A circuit board  20  side of the case  30  relative to the guide portion  31  has an insert pin  21  that serves as a joining pin. The number of the insert pins  21  is same as the number of the connection pins  15 . In the present embodiment, two insert pins  21  are paired for correspondence with the connection pins  15 . The insert pins  21  is insert molded in the case  30  to be integrated with the case  30 . One end of the insert pin  21  is exposed in a space in the case  30 , and the end extends to a position that corresponds to a position of the positioning hole  31   a  of the guide portion  31 . At least the end of the insert pin  21  protruding from the case  30  is formed to be deformable by having a thin shape. The end of the insert pin  21  has a hole  21 a, and a tip of the connection pin  15  is inserted in the hole  21   a . The other end  21   b  of the insert pin  21  is exposed in the case  30  in a protruding manner in a direction in parallel with an insertion direction of the circuit board  20  in the case  30 . The end  21   b  is inserted in a first through hole  20   a  that is formed on the circuit board  20 . 
         [0042]    An amount of protrusion of the insert pin  21  from the case  30  on the end that is connected with the connection pin  15  may be arbitrarily set as long as the end of the insert pin  21  can warp for absorbing a reaction force on the connection pin  15  when the reaction force is caused by a dislocation of the transducer due to a pressing force applied thereon for pressing the transducer into the case  30 . 
         [0043]    An upper side of the case  30  has an opening  32  in a round shape, and the transducer  10  having the cylindrical elastic body  33  pasted on the outer surface with the foaming elastic body  34  under the base  14  for suppressing vibration is inserted from the opening  32  to be assembled with the case  30 . The opening  32  of the case  30  exposes the vibration surface  11   b  of the transducer  11 , and the ultrasonic wave from the transducer  10  is emitted from the opening  32  toward an outside of the case  30 . 
         [0044]    An inner surface of the opening  32  of the case  30  has a third marker  38  for positioning a second marker  33   c  on the cylindrical elastic body  33 . The third marker  38  is formed as a groove along the insertion direction of the transducer  10  into the case  30 , and used for inserting the second marker  33   c  for positioning the transducer  10  in a circular direction. 
         [0045]      FIGS. 3A and 3B  show the exploded views in perspective. That is,  FIG. 3A  shows a perspective exploded view of the ultrasonic transducer  10  and the cylindrical elastic body  33 , and  FIG. 3B  shows a perspective exploded view of the case  30  and the ultrasonic transducer  10  with the elastic body  33  attached thereon.  FIGS. 4A and 4B  show illustrations of the cylindrical elastic body  33 . That is,  FIG. 4A  shows a bottom view (i.e., a case facing side) of the cylindrical elastic body  33 , and  FIG. 4B  shows a side view of the cylindrical elastic body  33 . 
         [0046]    The cylindrical elastic body  33  is made of silicon rubber, and covers the outer surface of a cylinder portion  11   c  of the housing  11  in the transducer  10  for preventing transfer of unnecessary vibration from the transducer  10  to the case  30 . 
         [0047]    As shown in  FIGS. 3A ,  3 B,  4 A, and  4 B, the cylindrical elastic body  33  has a flange  33   a  in a protruding shape on an opening  32  side of the case  30 , an outer wall  33   b  for covering the outer surface of the transducer  33   c , the hook  33   d  on an insertion end of the elastic body  33  into the opening  32  of the case  30 , and a cut  33   e  on an inner surface of the outer wall  33   b  of the elastic body  33  for receiving the first marker  14   a.    
         [0048]    The flange  33   a  and the hook  33   d  binds a wall of the opening  32  at both ends of insertion direction of the transducer  10  when the transducer  10  is inserted into the opening  32 . More practically, the hook  33   d  engages a reverse side (i.e., the circuit board side) of the guide portion  31  through a hole that is formed at a different position from the positioning hole  31   a  with a reaction force from the flange  33   a.    
         [0049]    The outer wall  33   b  has an inner diameter that has substantially the same value or slightly smaller value than that of the transducer  10 . Therefore, the transducer  10  is covered by the outer wall  33   b  of the cylindrical elastic body  33  without a gap. 
         [0050]    The second marker  33   c  is formed in parallel with the insertion direction of the transducer  10  into the opening  32  of the case  30 . When the cylindrical elastic body  33  covers the transducer  10 , the height of the second marker  33   c  is slightly smaller than the position of the tip end of the first marker  14   a  in a radial direction of the transducer  10 . 
         [0051]    The cut  33   e  is formed on the elastic body  33  for allowing the first marker  14   a  in a condition that the transducer  10  is covered by the elastic body  33 . 
         [0052]    When the transducer  10  is inserted in the cylindrical elastic body  33  with the first marker  14   a  aligned with the second marker  33   c , the tip end of the first marker  14   a  is exposed from the outer wall  33   b  of the elastic body  33  with the first marker  14   a  and the second marker  33   c  aligned on the same line. Then, the tip end of the first marker  14   a  is guided by the third marker  38  for inserting the transducer  10  into the opening  32  of the case  30 . In this manner, the protector portion  18  enters into the positioning hole  31   a  of the guide portion  31 , and the connection pins  15  enters into the hole  21   a  of the insert pin  21 . The transducer  10  is thereby fixed on the case  30  with the flange  33   a  and the hook  33   d.    
         [0053]    The foaming elastic body  34  is made of, for example, a foaming rubber, a silicon or the like. The foaming elastic body  34  has the connection pins  15  and the protector portion  18  disposed therein. The foaming elastic body  34  has a cut, and the cut receives the protector portion  18 . Further, the transducer  10 , the elastic body  33 , and the foaming elastic body  34  are pasted with each other by silicon adhesive. 
         [0054]    A portion of the case  30  separated by the guide portion  31  is filled with a damp-proof member  35 . More practically, the circuit board  20  positioning side of the case  30  has a filling of the damp-proof member  35  for preventing dampness. The dampproof member  35  is, for example, a silicon resin or a urethane resin. The dampproof member  35  of the present embodiment is a silicon resin. In this case, as shown in  FIGS. 2A and 2B , the circuit board  20  has external output terminals  36  for outputting signals, and one end of the output terminal  36  is exposed from a connector  37  that is formed on one face of the case  30 . 
         [0055]    The transducer  10  is assembled with the case  30  in the following manner. That is, the transducer  10  covered by the cylindrical elastic body  33  and the foaming elastic body  34  is inserted into the opening  32  of the case  30 . The protector portion  18  is, with the connection pins  15 , inserted into the positioning hole  31   a  of the guide portion  31  in the course of insertion of the transducer  10 . Then, the hook  33   d  of the elastic body  33  enters into the through hole  31   b  of the guide portion  31  to be engaged with the reverse side of the guide portion  31 . 
         [0056]    In this manner, the transducer  10  is positioned at a predetermined position of the case  30 , and the connection pins  15  are inserted into the hole  21   a  of the insert pins  21 . Further, the transducer  10  with the elastic body  33  pasted thereon is fixed in the opening of the case  30 . The insert pins  21  and the connection pins  15  are soldered for electrical coupling. 
         [0057]    Further, the circuit board  20  is disposed in the case  30 . In this manner, the end  21   b  of the insert pins  21  are inserted into the through holes  20   a  of the circuit board  20 , and the external output terminals  36  are inserted into the through holes  20   b  (i.e., first through hole) of the circuit board  20 . Then, the soldering of the terminals/pins with the holes enables electrical coupling of the piezoelectric element  12  with the circuit board  20  through the insert pins  31  as well as the electrical coupling of the external output terminals  36  with the circuit board  20 . 
         [0058]    After soldering the terminals and pins, the inner space of the case  30  are filled with the damp-proof member  35 . In this case, the circuit board  20  is disposed in the case  30  after positioning the transducer  10 . However, the circuit board  20  may be disposed in the case  30  before positioning the transducer  10  in the case  30 . 
         [0059]    The ultrasonic sensor  100  of the present disclosure has the connection pins  15  that protrude from a predetermined position of the base  14  and that are covered by the protector portion  18 , thereby enabling an easy positioning of the ultrasonic transducer  10  relative to the positioning hole  31  a of the case  30 . In this manner, the connection pins  15  are protected from being damaged in the course of insertion into the holes  21   a  of the insert pins  21 , together with the insertion of the end  21   b  of the insert pins  21  into the through holes  20   a  of the circuit board  20 . As a result, the workability of assembling operation of the ultrasonic sensor  100  is improved. 
         [0060]    The advantages of the present disclosure are derived from the connection structure of the connection pins  15  with the circuit board  20 . That is, the connection pins  15  are connected to the circuit board  20  through the insert pins  21 , instead of directly connected to the circuit board  20 , thereby enabling a reaction force against excessive insertion of the transducer  10  into the case  30  to be released toward the insert pins  21 . Further, ease of the positioning of the transducer  10  relative to the case  30  is improved by having the hole  21   a  to be aligned with the connection pins  15 . Furthermore, the insert pins  21  and the external output terminals  36  are aligned with the holes  20   a ,  20   b , thereby enabling the improvement of the workability of the assembling operation of the ultrasonic sensor  100 . 
         [0061]    Although the present invention has been fully described in connection with the preferred embodiment thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. 
         [0062]    For example, the insert pins  21  are insert molded with the case  30  in the above embodiment. However, the insert pins  21  may be formed in a different manner as long as they are integrated in the case  30 . Further, the shape of the insert pins  21  may be different from the above embodiment. That is, the portion of the insert pin  21  exposed in the case  30  entirely formed as a thin portion in the above embodiment may be formed as a partially thinned portion for having the same effect of easy bending on an application of the excessive force. 
         [0063]    Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims.