Patent Publication Number: US-2009223296-A1

Title: Attachment structure for ultrasonic sensor

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is based on Japanese Patent Application No. 2008-58422 filed on Mar. 7, 2008, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an attachment structure for attaching an ultrasonic sensor to a wall member of a movable body such as a vehicle bumper having a through-hole. 
     2. Description of Related Art 
     There has been proposed such an attachment structure for an ultrasonic sensor that a module (e.g., ultrasonic sensor) is fixed to a retain part (e.g., fixation member) attached to an inside (e.g., inner surface) of a bumper having a through-hole so that an end surface (e.g., an oscillation surface) of a head part of the ultrasonic sensor and an outer surface of the bumper are on the same plane. For instance, Patent Document 1 shows such attachment structures. 
     In a case of the above structure, the oscillation surface of the ultrasonic sensor is exposed to an outside through the through-hole of the bumper, and it is preferable in respects of design that a clearance between a wall surface defining the through-hole and the ultrasonic sensor is approximately constant in entire wall surface circumference. According to a structure shown in Patent Document 1, in order for the clearance to be constant in the entire wall surface circumference, it is however required to insert a centering member (e.g., cylindrical member) having an outer shape corresponding to a shape of the through-hole in the through-hole, and in this insertion state, it is required to attach a fixation member to a part of the inner surface of the bumper around the through-hole with reference to the centering member, and then to fix the ultrasonic sensor to the fixation member. Patent Document 2 proposes a fixation member for fixing a body (e.g., ultrasonic sensor) to an inside of a wall member (e.g., inner surface of the wall ember), the fixation member including a collar for positioning the fixation member relative to a hole (e.g., through-hole). 
     [Patent Document 1] JP-P2001-502406A corresponding to U.S. Pat. No. 6,279,210 
     [Patent Document 2] JP-P2001-527480A corresponding to U.S. Pat. No. 6,318,774 
     According to Patent Document 2, however, the collar is rigidly provided in the fixation member. Thus, when this fixation member is used for attaching an ultrasonic sensor having an ultrasonic transducer for both transmission and reception and a case receiving the ultrasonic transducer, there arises a problem that reverberant or echo remains longer and a nearby obstacle is difficult to be detected, if a member for restricting unwanted vibration transmission is not disposed between the ultrasonic transducer and the collar. 
     Further, if the member for restricting the unwanted vibration transmission is disposed between the ultrasonic transducer and the collar, the collar and the member for suppressing the unwanted vibration are disposed between the wall surface defining the through-hole and the ultrasonic transducer. Accordingly, a size of the through-hole enlarges and design becomes worse. 
     SUMMARY OF THE INVENTION 
     In view of the above points, it is an objective of the present invention to provide an attachment structure which provides coincidence between a center of an ultrasonic sensor and a center of a through-hole in a simple way, and which restricts unwanted vibration transmission between a wall member of a movable body and an ultrasonic transducer without spoiling design. 
     According to a first aspect of the present invention, an attachment structure including an ultrasonic sensor, a wall member equipped in a movable body, and a fixation member is provided. The ultrasonic sensor includes: an ultrasonic transducer having an oscillation surface for ultrasonic wave transmission and reception; a case receiving the ultrasonic transducer with the oscillation surface being exposed from the case; and an vibration insulation member disposed between the case and the ultrasonic transducer to suppress unwanted vibration transmission between the ultrasonic transducer and the case. The wall member has a through-hole with an opening shape corresponding to a shape of the oscillation surface. The fixation attaches the ultrasonic sensor to the wall member so that the oscillation surface is exposed to an outer surface side through the through-hole. The case of the ultrasonic sensor receives the ultrasonic transducer from a rear surface opposite to the oscillation surface to a part of a portion of a side surface, the side surface being other than the rear surface and the oscillation surface, the portion of the side surface is located on an inner surface side, wherein the fixation member is disposed on an inner surface of the wall member and disposed around the through-hole, wherein the case is fixed by the fixation member so that the oscillation surface and the outer surface of the wall member are on a substantially same plane. The fixation member includes a positioning member, wherein the positioning member is inserted into the through-hole, and contacts one of a wall surface defining the through-hole and an inner surface side corner part connecting to the wall surface, and the portion of the side surface of the ultrasonic transducer, the portion of the side surface being exposed from the case, wherein the positioning member cause a center of the through-hole to match a center of the oscillation surface of the ultrasonic sensor, which is fixed to the fixation member. The positioning member is made of a material suppressible of vibration transmission between the ultrasonic transducer and the wall member. 
     According to the above attachment structure, it is possible to match the center of the ultrasonic sensor and the center of the through-hole and to restrict unwanted vibration transmission between the wall member of the movable body and the ultrasonic transducer without spoiling design. 
     According to a second aspect of the present invention, an attachment structure for use in a vehicle is provided that includes an ultrasonic sensor and a fixation member. The ultrasonic sensor includes: an ultrasonic transducer having an oscillation surface for ultrasonic wave transmission and reception; a case receiving a part of the ultrasonic transducer with the oscillation surface being exposed from the case; and an vibration insulation member disposed between the case and the ultrasonic transducer to suppress vibration transmission between the case and the ultrasonic transducer. The fixation member attaches the ultrasonic sensor to a wall member of the vehicle, wherein the wall member has: an outer surface exposed to an outside of the vehicle; an inner surface opposite to the outer surface; and a through-hole penetrating between the outer and inner surfaces with an opening shape corresponding to a shape of the oscillation surface. The fixation member is disposed on the inner surface of the wall member and disposed around the through-hole. The fixation member attaches the ultrasonic sensor to the wall member so that the oscillation surface is exposed to the outside of the vehicle through the trough-hole. The ultrasonic sensor further has a rear surface opposite to the oscillation surface, and a side surface located between the oscillation surface and the rear surface. The case receives the part of the ultrasonic transducer from the rear surface of the ultrasonic transducer so that a part of the side surface of the ultrasonic transducer is exposed from the case. The fixation member includes: a retainer that fixes the case so that the oscillation surface and the outer surface of the wall member are on a substantially same plane, and so that the exposed part of the side surface of the ultrasonic transducer is located in the through-hole and located closer the outer surface of the wall member than the inner surface; and a positioning member that is inserted into the through-hole, contacts the exposed part of the side surface of the ultrasonic transducer, further contacts at least of an inner wall surface side corner part and a wall surface defining the through-hole of the wall member, and positions the ultrasonic transducer at a place where a center of the oscillation surface substantially matches a center of through-hole, the inner surface side corner part which connects the wall surface of the through-hole and the inner surface of the wall member. The positing member is made of a material suppressible of vibration transmission between the ultrasonic transducer and the wall member. 
     According to the above attachment structure, it is possible to match the center of the ultrasonic sensor and the center of the through-hole and to restrict unwanted vibration transmission between the wall member of the movable body and the ultrasonic transducer without spoiling design. 
     According to a third aspect of the present invention, there is provided an attachment structure for use in attaching an ultrasonic sensor to a wall member of a vehicle. The ultrasonic sensor includes: an ultrasonic transducer having an oscillation surface for ultrasonic wave transmission and reception, and a rear surface opposite to the oscillation surface; a case receiving a part of the ultrasonic transducer from the rear surface of the ultrasonic transducer so that a part of a side surface located between the oscillation surface and the rear surface is exposed from the case; and an vibration insulation member disposed between the case and the ultrasonic transducer to suppress vibration transmission between the case and the ultrasonic transducer. The wall member has: an outer surface exposed to an outside of the vehicle; an inner surface opposite to the outer surface; and a through-hole penetrating between the outer and inner surfaces with an opening shape corresponding to the oscillation surface. The attachment structure includes a fixation member that is disposed on the inner surface of the wall member and disposed around the through-hole, and that attaches the ultrasonic sensor to the wall member so that the oscillation surface is exposed to the outside of the vehicle through the trough-hole. The fixation member includes: a retainer that fixes the case so that the oscillation surface and the outer surface of the wall member are on a substantially same plane, and so that the exposed part of the side surface of the ultrasonic transducer is located in the through-hole and located closer the outer surface of the wall member than the inner surface; and a positioning member that is inserted into the through-hole, contacts the exposed part of the side surface of the ultrasonic transducer, further contacts at least one of an inner wall surface side corner part and a wall surface defining the through-hole of the wall member, and positions the ultrasonic transducer at a place where a center of the oscillation surface substantially matches a center of through-hole, the inner surface side corner part which connects the wall surface of the through-hole and the inner surface of the wall member. The positing member is made of a material suppressible of vibration transmission between the ultrasonic transducer and the wall member. 
     According to the above attachment structure, it is possible to match the center of the ultrasonic sensor and the center of the through-hole and to restrict unwanted vibration transmission between the wall member of the movable body and the ultrasonic transducer without spoiling design. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and 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 the drawings: 
         FIG. 1  is a cross sectional diagram illustrating an attachment structure for an ultrasonic sensor according to a first embodiment; 
         FIG. 2  is a plan view corresponding to  FIG. 1 , the view being taken from an outside of a vehicle; 
         FIG. 3  is a cross sectional diagram illustrating an attachment structure for an ultrasonic sensor according to a modification example; and 
         FIG. 4  is a cross sectional diagram illustrating a positioning member according to another modification example. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     Exemplary embodiments are described below with reference to the accompany drawings. An attachment structure for use in a vehicle is presented below as an exemplary attachment structure for use in a movable body. 
     First Embodiment 
       FIG. 1  is a cross sectional diagram illustrating an attachment structure for an ultrasonic sensor in accordance with a first embodiment.  FIG. 2  is a plan view corresponding to  FIG. 1 , the view being taken from an outside of a vehicle. A direction in which a through-hole extends is refereed to hereinafter as a penetration direction, and a direction perpendicular to the penetration direction is referred to hereinafter as a perpendicular direction. 
     The ultrasonic sensor is attached to a front part of a vehicle, a rear part of the vehicle, or four-cornered parts of a bumper so that the ultrasonic sensor can detect an obstacle existing around the vehicle. As shown in  FIG. 1 , the ultrasonic sensor  10  includes: an ultrasonic transducer  20  (e.g., so called a microphone) for both of transmission and reception; a case  30  receiving the ultrasonic transducer  20  so that an oscillation surface  25  of the ultrasonic transducer  20  is exposed; and a vibration insulation member  31  disposed between the case and the ultrasonic transducer  20 . 
     The ultrasonic transducer  20  includes a piezoelectric element  22  and a housing  21  receiving therein the piezoelectric element  22 . The housing  21  is made of a conductive material such as aluminum etc. and formed in a tubular shape having a closed end. Alternatively, the housing  21  may be made of resin and has a metal coated inner surface. The housing  21  defines therein an internal space  23 , as shown in  FIG. 1 . The piezoelectric element  22  is bonded to an inner surface  24   a  of a bottom part  24  of the housing  21 . Accordingly, an outer surface of the bottom part  24  (which is opposite to the inner surface  24   a ) can function as an oscillation surface of the ultrasonic transducer  20 . The oscillation surface has a generally circular shape, as shown in  FIG. 2 . 
     The piezoelectric element  22  includes a sintered piezoelectric ceramic, such as lead zirconate titanate (PZT), barium titanat and the like. Electrodes (not shown) are respectively formed on a surface, which is a bonding surface between the piezoelectric element  22  and the housing, and its opposite surface. On end of a lead  26  is connected with the electrode located on the surface opposite to the boding surface and the electrode located on the bonding surface. Another end of the lead  26  sticks out from the housing  21 . Accordingly, it is possible apply an alternating current to ends of the piezoelectric element  22  through the lead  26  to drive the piezoelectric element  22  by the application of the alternating current drives. It is accordingly possible to oscillate the oscillation surface of the ultrasonic transducer  20 . After the lead  26  is connected (e.g., soldered), the internal space  23  of the housing  21  is filled with a vibration absorption member (not shown) so that the vibration absorption member surrounds the piezoelectric element  22  except a surface facing the bottom part  24 . The vibration absorption member is made of an elastic material such as silicon, polyurethane and the like, and restricts vibration due to the piezoelectric element  22  from transmitting to parts other than the bottom part  24  of the housing  21 . 
     Together with a circuit board  27 , the ultrasonic transducer  20  having the above-described configuration is installed in a case  30  made of an insulation material, e.g., resin. 
     The circuit board  27  is electrically connected to the piezoelectric element  22  via the lead  26 . The circuit board  27  includes a circuit for outputting a drive signal to the piezoelectric element  22  to oscillate and generate an ultrasonic wave, and for receiving a voltage signal generated due to an inverse piezoelectric effect when the piezoelectric element  22  has strains resulting from transmission of the ultrasonic wave to the piezoelectric element  22 . Further, the circuit board  27  is connected to a controller (not shown) via a connector  28 . The controller detects an obstacle existing rearward of a vehicle or around the corner parts. 
     The vibration insulation member  31  is interposed inside the case  30  to suppress unwanted vibration transmission between the ultrasonic transducer and the case  30 . In the present embodiments, the vibration insulation member  31  is made of silicon rubber and disposed in a periphery of the ultrasonic transducer  20 . To seal an inside of the case  30 , rear of the circuit board  27  is filled with a sealing member  32  made of, for example, silicon rubber. The periphery of the ultrasonic transducer  20  includes, for example, a part of a side surface  20   a  of the ultrasonic transducer  20  and a rear surface  25   a  of the ultrasonic transducer  20  opposite to the oscillation surface  25 . 
     The case  30  receives a part of the side surface  20   a  of the ultrasonic transducer  20  from the rear surface  25   a  opposite to the oscillation surface  25 , so that the part of the side surface  20   a  becomes located closer to the inner surface  40   a  of the bumper  40  than the outer surface, the bumper  40  being an example of the wall member. In the present embodiments, the case  30  is formed in a cylindrical shape, a middle of an inside of which a stopper  33  is formed. The stopper  33  can fix the ultrasonic transducer  20  which is applied by the vibration insulation member  31  and which is inserted from one open end. The stopper  33  can fix the circuit board  27  which is inserted from another open end. When the ultrasonic transducer  20  applied by the vibration insulation member  31  is installed in the case  30 , the open end of the case  30  located on a bumper  40  side becomes concentric with the oscillation surface  25  of the ultrasonic transducer  20 . In the present embodiments, an end part of the vibration insulation member  31  located on the bumper  40  side is also concentric with the open end of the case  30  located on the bumper  40  side and the shape of the oscillation surface  25  of the ultrasonic transducer  20 . 
     As shown in  FIG. 2 , the ultrasonic sensor  10  having the above-described configuration is fixed to the bumper  40  by the use of the fixation member  50  with a part of the ultrasonic sensor  10  being located inside the through-hole  41 , so that sensing is possible through the through-hole  41 , or in other words, ultrasonic transmission and reception is possible without involving the bumper  40 , wherein the through-hole  41  of the bumper  40  has a circular opening shape corresponding to the shape of the oscillation surface  25 . In the above fixed state, the oscillation surface  25  of the ultrasonic transducer  20  and the outer surface  40   b  of the bumper  40  are on the same plane. As shown in  FIG. 1 , the fixation member  50  contacts both of the case  30  of the ultrasonic sensor  10  and the inner surface  40   a  of the bumper  40 . The fixation member  50  includes a retainer  51  for fixing the ultrasonic sensor  10  to the bumper  40  and a positioning member  52  for positioning the retainer  51  relative to the bumper  40  with reference to the through-hole  41 . 
     The retainer  51  positions the ultrasonic sensor  10  in the penetration direction of the through-hole  41 , and maintains this positioning state. In the present embodiments, the retainer  51  is made of polybutylene terephthalate resin (PBT), and includes a bumper fixation portion  53 , a sensor fixation portion  54  and a connection portion  55 . The bumper fixation portion  53  has a plate shape, and is adhesively fixed to the inner surface  40   a  of the bumper  40 . The sensor fixation portion  54  has a cylindrical shape surrounding an outer periphery surface  30   a  of the case  30  so as to receive and support the case  30  of the ultrasonic sensor  10  therein. Further, at least a part of the sensor fixation portion  54  contacts the outer periphery surface  30   a , thereby forming a fixation structure between the part of the sensor fixation portion and the case  30 . The connection portion  55  connects the bumper fixation portion  53  and the sensor fixation portion  54 . More specifically, a fitting connection concave part  56  is disposed on the sensor fixation portion  54 , and a fitting connection convex part  34  for fitting into the fitting connection concave part  56  is disposed on the outer periphery surface  30   a  of the case  30 . With the bumper fixation portion  53  being fixed to the inner surface  40   a  of the bumper  40 , the ultrasonic sensor  10  is inserted into the inside of the tubular-shaped sensor fixation portion  54  while the oscillation surface  25  is being a lead of the insertion until the fitting connection convex part  34  fits into the fitting connection concave part  56 , and thereby, the oscillation surface  25  and the outer surface  40   b  are on the same plane. 
     The positioning member  52  positions the retainer  51  relative to the bumper  40  with reference to the through-hole  41 , as described above. Thereby, in the perpendicular direction, the positioning member  5  functions to generally match the center of the through-hole  41  and the oscillation surface  25  of the ultrasonic sensor  10  fixed to the retainer  51 . The positioning member  52  is made of a material different from that of the retainer  51 , more specifically made of a material such as silicon rubber etc., which is capable of suppressing unwanted vibration transmission between the ultrasonic transducer  20  and the bumper  40 . Accordingly, the positioning member  52  can function as an absorber that suppresses the unwanted vibration transmission between the ultrasonic transducer  20  and the bumper  40 . 
     In the present embodiments, the positioning member  52  includes a retainer fixation portion  57  to be fixed to the retainer  51  and an insertion portion  58  to be inserted into the through-hole  41 . The retainer fixation portion  57  is fixed to the retainer  51 . The insertion portion  58  is inserted into the through-hole  41 , contacts a exposed part of a side surface  20   a  of the ultrasonic transducer  20  that is exposed from the case  30 , and further contacts one of the wall surface defining the through-hole  41  and an inner surface side corner part (a corner part between the wall surface and the inner surface  40   a ) connecting to the wall surface. 
     The retainer fixation portion  57  has a ring shape so as to surround the side surface  20   a  of the ultrasonic transducer  20 . Its sectional shape has a generally L shape, and includes: a part that contacts a part of an outer periphery surface of the sensor fixation portion  54  of the retainer  51 ; and a part that contacts the inner surface  40   a  of the bumper  40 . A ditch part  57   a  is formed in the part that contacts the inner surface  40   a  of the bumper  40 , and the ditch part  57   a  fits into a bumper side end part of the sensor fixation portion  54 . Thereby, the retainer  51  and the positioning member  52  are integrated as the fixation member  50 . The insertion portion  58  is extended toward a through-hole side tip of the part of the retainer fixation member  57 , the part which contacts the inner surface  40   a  of the bumper  40 . 
     The insertion portion  58  includes a part of the positioning member  52 , wherein the part is located (radially) inward of the wall surface defining the through-hole  41  in the perpendicular direction, and the part surrounds the side surface  20   a  of the ultrasonic transducer  20  in a manner similar to the retainer fixation portion  57 . Compared to the part connecting the retainer fixation portion  57 , the part contacting the side surface  20   a  of the ultrasonic transducer  20  is located closer the outer surface  40   b  of the bumper  40 . As closer to the outer surface  40   b  of the bumper  40 , an opening area defined by the ring-shaped insertion portion  58  becomes smaller. The insertion portion  58  is located closer to the inner surface  40   a  of the bumper  40  than the outer surface  40   b  of the bumper  40  while an end part of the insertion portion  58  located on the outer surface  40   b  side does not project from the outer surface  40   b  of the bumper  40 . Further, the insertion portion  58  contacts the corner part (which is an inner surface side corner part connecting with the wall surface defining the through-hole  41 ) defined between the wall surface of the through-hole  41  and the inner surface  40   a  of the bumper  40 . 
     Further, the ring-shaped insertion portion  58  contacts the exposed part of the ultrasonic transducer in an entire side surface circumference, the exposed part being exposed from the case  30  (vibration insulation member  31 ). More specifically, a perpendicular direction length (a thickness in a radial direction of the through-hole  41 ), which is from a wall surface side end of the through-hole to the part that contacts the side surface  20   a  of the ultrasonic transducer  20 , is generally constant in the entire circumference. 
     In the present embodiments, since the inner surface side corner part is used as a reference for the positioning as described above, the part of the insertion portion  58  contacting the side surface  20   a  of the ultrasonic transducer  20  is located closer to the outer surface  40   b  of the bumper  40  compared to the part of the insertion portion  58  connecting the retainer fixation portion  57 , and further, the insertion portion  58  contacts the exposed part of the side surface  20   a  of the ultrasonic transducer  20  in the through-hole  41 , wherein the exposed part of the side surface  20   a  of the ultrasonic transducer  20  is exposed from the case  30 . Further, an inner periphery surface of the ring-shaped insertion portion  58  has a tapered part which is located in a predetermined range starting from an end distant from the outer surface  40   b  and which approaches the side surface  20   a  of the ultrasonic transducer  20  as closer to the outer surface  40   b  in the penetration direction. 
     In the followings, explanation is given on advantages of the above-described attachment structure for the ultrasonic sensor  10 . 
     First of all, in the present embodiments, the fixation member  50  for fixing the ultrasonic sensor  10  to the bumper  40  includes: the retainer  51  which is fitted into the ultrasonic sensor  10  and determine a position of the ultrasonic sensor  10  relative to the bumper  40  in the penetration direction; and the positioning member  52  which determines the position of the ultrasonic sensor  10  relative to the bumper  40  in the perpendicular direction. This positioning member  52  includes: a retainer fixation portion  57  which is to be fixed to the retainer  51 ; and the insertion portion  58  which has a ring shape, is to be inserted into the through-hole  41  and is to contact the inner surface side corner part of the bumper  40  in the entire circumference. Accordingly, the positioning of the fixation member  50  relative to the bumper  40  is possible in attaching the fixation member  50  to the bumper  40 , by inserting the insertion portion  58  into the through-hole  41  and making contact between the insertion portion  58  and the inner surface side corner part of the bumper  40  in the entire circumference. In other words, it is possible determines a position (e.g., x-y coordinates) on a plane extending along the inner surface  40   a  of the bumper. Further, the positioning of the fixation member  50  relative to the bumper  40  in the penetration direction is possible by making contact between the bumper fixation portion  53  of the retainer  51  and the inner surface  40   a  of the bumper  40 . In other words, it is possible determines a position (e.g., z-coordinate) in a direction perpendicular to the inner surface  40   a  of the bumper  40 . Further, it is possible to maintain the positioned state in such manner that the bumper fixation portion  53  is adhered to the inner surface  40   a  of the bumper  40  with the positioning in the perpendicular and penetration directions being made. Since the ultrasonic sensor  10  can be fixed to the fixation member  50  fixed in the above manner, it is possible to provide an attachment structure where the center of the oscillation surface  25  matches the center of the through-hole  41  in the perpendicular direction. As described above, according to the present embodiments, in fixing the fixation member  50  to the bumper  40 , it is possible to determine the position of the fixation member  50  with reference to the bumper  40  by using the fixation member itself. Therefore, the centering member is not necessary, and the center of the ultrasonic sensor  10  (the oscillation surface  25 ) and that of the through-hole can match each other in a simple way. Further, according to the present embodiments, the positioning member  52  is made of a material (e.g., silicon rubber) capable of suppressing unwanted vibration transmission between the ultrasonic transducer  20  and the bumper  40 . Therefore, while the positioning member  52  contacts both of the ultrasonic transducer  20  and the bumper  40 , the positioning member  52  can suppress unwanted vibration transmission between both. 
     Further, as described above, the positioning member  52  of the fixation member  50  has a perpendicular direction positioning function and a function of suppression of unwanted vibration transmission between the ultrasonic transducer  20  and the bumper  40 . Thus, since the positioning member  52  contacts both of the ultrasonic transducer  20  and the bumper  40 , and thus, a clearance between the side surface  20   a  (the oscillation surface  25 ) of the ultrasonic transducer  20  and the through-hole wall surface (open end) of the bumper  40  may be ensured to a thickness of the positioning member  52  (the insertion portion  58 ) or the like. Therefore, it is possible to reduce a radial size (opening area) of the through-hole  41  compared to a structure where a member having a positioning function (positioning member) and a member for suppressing an un-wanted wave transmission are laminated, or compared to a structure where a positioning member does not contact the side surface  20   a  of the ultrasonic transducer  20  (a structure where there exist a gap to the positioning member in the perpendicular direction). Accordingly, it is possible to suppress design aggravation. 
     Further, according to the present embodiments, the shape of the oscillation surface  25  (a shape defined by side surface of the ultrasonic transducer  20 ) is the same of the opening shape of the through-hole  41  (the through-hole  41  is larger in dimensions). Because of the above-described advantages associated with the positioning, as shown in  FIG. 2 , the clearance (the above-described clearance) between the oscillation surface  25  and the open end of the bumper  40  can be approximately constant in the entire circumference. It is accordingly possible to provide design improvement. 
     Further, according to the present embodiments, the insertion portion  58  has a ring shape and contacts the side surface  20   a  of the ultrasonic transducer  20  in the entire circumference. Thus, as shown in  FIG. 2 , when the bumper  40  is viewed from an outer surface  40   b  side, the clearance between the oscillation surface  25  and the bumper  40  does not have a clearance (gap) in the perpendicular direction (a space located on the outer surface  40   b  of the bumper  40  and a space located on the inner surface  40   a  side are interrupted by the insertion portion  58 ). Accordingly, design improvement is also made possible. Further, according to the present embodiments, the positioning member  52  (the insertion portion  58 ) does not project from the outer surface  40   b  of the bumper although the positioning member  52  is inserted in the through-hole  41 . It is accordingly possible to provide design improvement. 
     Further, according to the present embodiments, the inner periphery surface of the insertion portion  58  has a tapered part which is located in the predetermined range starting from the end distant from the outer surface  40   b  and which approaches the side surface  20   a  of the ultrasonic transducer  20  as closer to the outer surface b in the penetration direction. Thus, when the part of the ultrasonic transducer  20  of the ultrasonic sensor  10  is inserted into the through-hole  41  from the inner surface  40   a  side while the oscillation surface  25  is a lead of the insertion, the taper can guide the ultrasonic transducer  20  to a predetermined position, and thereby, it is possible to ease the insertion. 
     While the present invention is described above with reference to the exemplary embodiments, the present invention is not limited to the above-described embodiments. The present invention can be modified in various ways for embodiments to an extent without departing from the scope of the present invention. 
     According to the above embodiments, the insertion portion  58  inserted into the through-hole  41  contacts the inner surface side corner part of the bumper  40 , and thereby enabling determination of a position of the fixation member  50  relative to the bumper  40 . However, as shown in  FIG. 3  for instance, the insertion portion  58  may contact the wall surface defining the though-hole. This configuration also can determine the position of the fixation member  50  relative to the bumper  40 .  FIG. 3  is a cross sectional diagram illustrating a modification example corresponding to  FIG. 1 . According to an example illustrated in  FIG. 3 , the ditch part  57   a  is not disposed in the retainer fixation portion  57  of the positioning member  52 , and the positioning member  52  made of silicon rubber is adhered to the retainer  51 . 
     Further, according to the above embodiments, the insertion portion  58  having a ring shape contacts the inner surface side corner part of the bumper  40  in the entire circumference, and thereby, the position of the fixation member  50  relative to the bumper  40  in the perpendicular direction is determined. However, a shape of the insertion portion  58  for providing the positioning function is not limited to the ring-shape. Three or more insertion portions  58  may be spaced away from each other so as to surround a periphery of the ultrasonic transducer  20 , and radial thicknesses of parts to be located in the through-hole  41  may be almost the same. According to an example illustrated in  FIG. 4  for instance, three insertion portions  58  are disposed so that a distance between adjacent insertion portions  58  (an angle between a line interconnecting one of two adjacent insertion portions  58  and the center of the through-hole  41  and a line interconnecting the other of two adjacent insertion portions  58  and the center of the through-hole  41 ) is constant. Further, radial thicknesses of parts of the insertion portions  58  located inside the through-hole  41  are generally equal to each other. Although not shown in the drawings, the three insertion portions  58  extend from a through-hole side end part of the retainer fixation portion  57  having a ring shape. In the case of using the multiple insertion portions  58  spaced away from each other, a portion in which the insertion portions  58  exist has clearances between adjacent insertion portions  58  in a gap between the oscillation surface  25  and the bumper  40  in a laminating direction (in other words, the insertion portions  58  interrupt only parts of a ring-shaped gap that connects between the outer surface  40   b  of the bumper  40  and the inner surface  40   a  of the bumper  40 ). Thus, in terms of design, it may be preferable that the insertion portion  58  have a ring shape as illustrated in the above embodiments.  FIG. 4  is a plan view illustrating a modification example of the positioning member corresponding to  FIG. 2 . 
     Further, according to the above embodiments, the inner periphery surface of the ring-shaped insertion portion  58  has the tapered part which is located in the predetermined range starting from the end distant from the outer surface  40   b  and which tapers toward the outer surface  40   b  while reducing a radial dimension. However, the part having a tapered shape is not limited to the above-described example, and may be an arbitrary part of the inner periphery surface of the ring-shaped insertion portion  58 . For example, in the example illustrated in  FIG. 3 , the inner periphery surface of the ring-shaped insertion portion  58  has: a part which occupies a predetermined region starting from an end distant from the outer surface  40   b  and which is generally parallel to the side surface  20   a  of the ultrasonic transducer  20 ; and another part which occupies another predetermined region from the parallel part and which tapers while reducing a radial dimension. 
     Further, according to the above embodiments, the retainer  51  fixation portion and the insertion portion  58  of the positioning member  52  are spaced away. However, in a fixation method such as adhering, integral molding and the like, an end part of the insertion portion  58  may function as the retainer fixation portion to provide a structure where the insertion portion  58  and the retainer  51  is fixed. For example, there may be provided a structure where the retainer fixation portion  57  illustrated in  FIG. 1  is replaced with the retainer  51 . 
     Further, according to the above embodiments, in the insertion portion  58 , the part contacting the side surface  20   a  of the ultrasonic transducer  20  is located closer to the outer surface  40   b  of the bumper  40  compared to the part connecting with the retainer fixation portion  57 . Further, the opening area defined by the insertion portion  58  with the ring shape reduces as closer to the outer surface  40   b  of the bumper  40 . However, in an alternative configuration, the part connecting with the retainer fixation portion  57  may be located closer to the outer surface  40   b  of the bumper  40  compared to the part contacting the side surface  20   a  of the ultrasonic transducer  20 , and the opening area defined by the insertion portion  58  with the ring shape may reduce as closer to the inner surface  40   a  of the bumper  40 . 
     Further, according to the above embodiments, the retainer  51  is adhesively fixed to the bumper  40 . However, a fixing way is not limited to the above example. For example, it is also possible to appropriately employ a known fixing way such as fitting, screwing and the like. 
     Further, according to the above embodiments, the fixation member  50  is configured such that the positioning member  52  is fitted into and combined with the retainer  51  for fixing the ultrasonic sensor  10  to the bumper  40 . However, a way of fixing the positioning member  52  to the retainer  51  is not limited to the above example. For example, it is possible to employ bonding, screwing, integral molding (e.g., molding with the use of two materials), clumping with another member, and the like. 
     Further, according to the above embodiments, a vehicle is illustrated as an example of a movable body. Alternatively, application to a movable body other than a vehicle is possible. Further, a vehicle bumper is illustrated as an example of a wall member. Alternatively, a wall member may be other than a vehicle bumper, such as a vehicle body (e.g., a thin plate made of metal), a resin molding (e.g., protection member disposed on a part of a bumper or a part of body) and the like. 
     Further, according to the above embodiments, an opening shape of the through-hole  41  and a shape of the oscillation surface (a shape defined by the side surface of the ultrasonic transducer  20 ) are mutually circular. However, these shapes are not limited to circular. Arbitrary shapes that are mutually the same (different in dimension) can be employed. 
     Further, according to the above embodiments, the retainer  51  is made of PBT. However, the material for the retainer  51  is not limited to the above example if the material allows the fixing of the ultrasonic sensor  10  to the bumper  40 . 
     Further, according to the above embodiments, the positioning member  52  is made of silicon rubber. However, the material for the positioning member  52  is not limited to the above example if the material allows restriction of unwanted vibration transmission between the ultrasonic transducer  20  and the bumper  40 . 
     Further, according to the above embodiments, the sensor fixation portion  54  has a cylindrical shape so as to surround an outer peripheral surface  30   a  of the case  30 . Alternatively, as the shape the sensor fixation portion  54 , it is also possible to appropriately employ the shape that allows the case  30  of the ultrasonic sensor  10  to be received and retained therein. 
     Further, according to the above embodiments, in the retainer fixation portion  57 , the ditch part  57   a  is formed on a part that contacts the inner surface  40   a  of the bumper  40 , and the ditch part  57   a  is fitted into the bumper  40  side end part of the sensor fixation portion  54  to thereby combine the retainer  51  and the positioning member  52 . Alternatively, as shown in  FIG. 3 , the retainer fixation portion  57  may not have the ditch part  57   a . This also enables combination of the retainer  51  and the positioning member  52 . 
     Further, according to the above embodiments, the housing  21  of the ultrasonic transducer  20  has a tubular shape with a closed end. However, the shape of the housing  21  is not limited to the above example. 
     Further, according to the above embodiments, the housing  21  is made of aluminum. Alternatively, it is possible to employ a material with an electric conductivity accordingly. 
     Further, according to the above embodiments, the case  30  is made of PBT. Alternatively, it is possible to arbitrarily employ a material having an insulation characteristic. 
     Further, according to the above embodiments, the case  30  has a cylindrical shape. However, the shape of the case  30  is not limited to this example. 
     Further, according to the above embodiments, the vibration insulation member  31  is made of silicon rubber. Alternatively, as the material for the vibration insulation member  31 , it is possible to employ a material that allows the restriction of unwanted vibration transmission between the ultrasonic transducer  20  and the case  30 . 
     While the invention has been described above with reference to various embodiments thereof, it is to be understood that the invention is not limited to the above described embodiments and constructions. The invention is intended to cover various modifications and equivalent arrangements. In addition, while the various combinations and configurations described above are contemplated as embodying the invention, other combinations and configurations, including more, less or only a single element, are also contemplated as being within the scope of embodiments.