Patent Publication Number: US-2021170968-A1

Title: Retainer member

Description:
CROSS REFERENCE TO RELATED DOCUMENT 
     The present application claims the benefit of priority of Japanese Patent Application No. 2018-157615 filed on Aug. 24, 2018, the disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     This disclosure generally relates to a retainer member which firmly secures an ultrasonic sensor to a vehicle body component. 
     BACKGROUND ART 
     Patent literature 1 discloses a mount structure designed for an ultrasonic sensor to eliminate adverse effects, as arising from entry of water, on performance of the ultrasonic sensor. Specifically, the mounting structure has an outer plate with a hole exposed to an outer surface of the outer plate. The ultrasonic sensor is installed in the hole. The outer plate has a rib which is disposed on an inner surface of the outer plate to retain the ultrasonic sensor. The ultrasonic sensor is secured to the rib through a vibration absorber. A water drain hole is formed on the outer plate or the vibration absorber which is located vertically just beneath the ultrasonic sensor. The water drain hole communicates with space between a housing of the ultrasonic sensor and the outer plate, the rib, or the vibration absorber. 
     PRIOR ART DOCUMENT 
     Patent Literature 
     PATENT LITERATURE 1 Japanese Patent No. 3999187 
     SUMMARY OF THE INVENTION 
     A retainer member may be used to secure the ultrasonic sensor to a vehicle body component, such as a bumper. The retainer member is a component or member disposed between a body of the ultrasonic sensor and the vehicle body component. The retainer member is made from a hard synthetic resin, such as ABS resin or polypropylene. The firm attachment of the ultrasonic sensor to the vehicle body component is achieved by securing the retainer member to the body of the ultrasonic sensor and also firmly attaching the retainer member to the vehicle body component. 
     The patent literature 1 proposes a means for draining water from a portion of the ultrasonic sensor which is attached directly to the vehicle body component, but however, is still silent about a suitable means for draining water from a portion of the ultrasonic sensor which is attached to the vehicle body component through the retainer member. 
     This disclosure was made in view of the above described problem. Specifically, this disclosure provides a suitable solution to a problem of draining water from a portion of the ultrasonic sensor which is secured to the vehicle body component through the retainer member. 
     According to one aspect of this disclosure, there is provided a retainer member which secures an ultrasonic sensor to a vehicle body component, the ultrasonic sensor being equipped with a sensor body which includes a cylindrical ultrasonic microphone and a microphone support, the ultrasonic microphone extending in an axial direction parallel to a longitudinal center line and including a protruding portion located on a tip side thereof in the axial direction and a supported portion located on a base side thereof in the axial direction, the microphone support having the protruding portion protruding outside thereof and also retaining the supported portion. The retainer member comprises: (a) a body retaining portion which is formed in a cylindrical shape with a bottom and has an opening in a base side thereof in the axial direction, the body retaining portion having at least a portion of the microphone support disposed therein; (b) a microphone facing portion which is of a cylindrical shape accommodating the ultrasonic microphone, disposed outside the ultrasonic microphone in a radial direction oriented radially from the longitudinal center line, and extends from the body retaining portion toward the tip side in the axial direction; (c) a pair of fastening portions which are of a plate-like shape and equipped with engaging portions engaging the sensor body, the fastening portions extending from the microphone facing portion toward the base side in the axial direction along the longitudinal center line, the fastening portions facing each other across the longitudinal center line; (d) a drain path which passes through the microphone facing portion or a first one of the fastening portions in the radial direction and serves to discharge water from an inner space in the microphone facing portion to outside the inner space; and (e) a stamped wall portion which faces the drain path through the longitudinal center line and is located in the microphone facing portion or a second one of the fastening portions in alignment with the drain path. 
     In the above structure, the engaging portion of each of the fastening portions extending from the microphone facing portion of the retainer member engages the sensor body of the ultrasonic sensor, thereby attaching the retainer member to the ultrasonic sensor. Upon the attachment of the retainer member to the ultrasonic sensor, the body retaining portion accommodates at least a portion of the microphone support of the sensor body. The microphone facing portion is located outside the ultrasonic microphone of the sensor body. This has the ultrasonic microphone disposed in the space in the microphone facing portion. 
     A condition where the ultrasonic sensor is firmly attached to the vehicle body component using the retainer member is referred to as a vehicle-mounted condition. In the vehicle-mounted condition, there is a risk that when it is raining, water may enter a joint of the ultrasonic sensor with the vehicle body component. Specifically, an air gap into which water is admitted may be created between the ultrasonic microphone and the microphone facing portion of the retainer member. When water enters and is then accumulated in the air gap in the vehicle-mounted condition, it may result in an increase in unwanted reflected waves arising from propagation of vibration through the accumulated water, which leads to an error in detection of an object. 
     In the above structure, the retainer member is equipped with the drain path. The drain path is shaped to pass through the microphone facing portion or the fastening portion extending from the microphone facing portion in the radial direction. This enables the drain path to discharge water from the space in the microphone facing portion. The discharging of water from the air gap using the drain path minimizes a risk that water, as having entered from the outside, may be accumulated in the air gap. 
     The formation of the drain path will result in a decrease in mechanical stiffness of the microphone facing portion or the fastening portion, thereby resulting in imbalance in stiffness between areas of the microphone facing portion which face each other across the longitudinal center line or between the fastening portions. This leads to deterioration of fixation of the ultrasonic sensor in the vehicle-mounted condition. 
     In order to alleviate the above problem, the retainer member is equipped with the stamped wall portion. The stamped wall portion is formed in the microphone facing portion or the fastening portions and opposed to the drain path across the longitudinal center line. The stamped wall portion is arranged in correspondence with the drain path. For instance, in a case where the drain path is formed in the microphone facing portion, the stamped wall portion is also formed in the microphone facing portion. Alternatively, in a case where the drain path is formed in one of the fastening portions, the stamped wall portion is also formed in the other fastening portion. The stamped wall portion is, like the drain path, shaped to pass through the microphone facing portion or the fastening portion in the radial direction. 
     With the above arrangements, the formation of the drain path results in a decrease in stiffness of the microphone facing portion or the fastening portion. The formation of the stamped wall portion also results in a decrease in stiffness of the microphone facing portion or the fastening portion. The stamped wall portion and the drain path face each other through the longitudinal center line in the microphone facing portion or the fastening portions. This minimizes the imbalance in stiffness between the areas facing each other through the longitudinal center line. 
     The above structure minimizes the imbalance in stiffness between portions of the microphone facing portion or between the fastening portions which face each other across the longitudinal center line and also eliminates the risk of a failure in operation of the ultrasonic sensor due to entry of water, such as rain, thereinto in the vehicle-mounted condition. The structure, thus, provides a suitable means for solving the problem with discharge of water from a joint of the ultrasonic sensor to a vehicle body component using the retainer member. 
     Symbols in brackets in each item of this document are used only to indicate exemplified correspondences between the symbols and means specified below in the embodiment. This disclosure is not limited to what are expressed by the symbols. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an outline view of a vehicle in which an ultrasonic sensor according an embodiment is mounted. 
         FIG. 2  is a cross sectional side view of the ultrasonic sensor in  FIG. 1 . 
         FIG. 3  is a perspective view which shows the appearance of a retainer member illustrated in  FIG. 2 . 
         FIG. 4  is a plan view which illustrates the appearance of the retainer member shown in  FIG. 3 . 
         FIG. 5  is a side view which illustrates the appearance of the retainer member shown in  FIG. 3 . 
         FIG. 6  is a perspective view which illustrates the appearance of a modified form of a retainer member. 
         FIG. 7  is a plan view which illustrates the appearance of the retainer member shown in  FIG. 6 . 
         FIG. 8  is an enlarged side view which illustrates a modified form of a reinforcing rib shown in  FIG. 7 . 
     
    
    
     EMBODIMENT FOR CARRYING OUT THE INVENTION 
     An embodiment in this disclosure will be described below with reference to the drawings. For the simplicity of explanation, longitudinal, lateral, and vertical directions referred to in the embodiment are defined by arrows in the drawings. Possible modifications of the embodiment will be described after discussion of the embodiment because if explanation of the modification is made in the middle of the discussion of the embodiment, it may interfere the understanding of the embodiment. 
     Structure 
     Referring to  FIG. 1 , the vehicle Vis a known four-wheeled vehicle and equipped with the vehicle body V 1  which is of a substantially rectangular shape in a plan view. The vehicle body V 1  has the bumper V 2  and the front grille V 3  which are vehicle body components secured to a front end thereof. The front grille V 3  is arranged above the bumper V 2 . The vertical or front-back direction, as referred to in the following discussion, is defined in a vehicle-mounted condition where the ultrasonic sensors  1  are mounted in the vehicle body V 1 . In the following discussion, the vertical or front-back direction used to refer to a structure of each part is, therefore, based on orientation of each part mounted in or on the vehicle body V 1 , i.e., in the vehicle-mounted condition. 
     The bumper V 2  and the front grille V 3  have formed therein the mounting holes V 4  in the shape of through-holes for attaching the ultrasonic sensors  1  thereto. Specifically, in this embodiment, the mounting holes V 4  are arranged in two corners of the bumper V 2 . The two mounting holes V 4  are also formed in the front grille V 3  to be bilaterally symmetrical with each other. The mounting holes V 4  are each shaped to be circular and have the cylindrical inner peripheral surfaces V 5 . 
     The ultrasonic sensors  1  are designed to be mountable to the bumper V 2  and the front grille V 3 . An outline of structure of the ultrasonic sensors  1  secured to the front grille V 3  and a mounting structure of the ultrasonic sensors  1  secured to the front grille V 3  will be described below with reference to  FIGS. 2 to 5 . 
     Ultrasonic Sensor 
     Referring to  FIG. 2 , the sensor body  2  which constitutes a body of the ultrasonic sensor  1  includes the ultrasonic microphone  3  and the microphone support  4 . This embodiment is also equipped with the cushion member  5  and the retainer member  6  which serve as parts for mounting the ultrasonic sensor  1  in the front grille V 3 . 
     A condition where the cushion member  5  and the retainer member  6  are temporarily mounted in the sensor body  2  before the ultrasonic sensor  1  is attached to the front grille V 3  will also be referred to as a temporarily assembled condition. The temporarily assembled condition is defined for the sake of convenience of discussion of a positional relation among parts in this embodiment. The temporarily assembled condition is, therefore, not necessarily created when the ultrasonic sensors  1  are mounted in the front grille V 3 . 
     The ultrasonic microphone  3  is designed to transmit and receive ultrasonic waves. Specifically, the ultrasonic microphone  3  is configured to output a radar wave in a direction along a directivity axis thereof and receive a wave reflected from an object present around the vehicle V. 
     The ultrasonic microphone  3  has a cylindrical outer shape with the longitudinal center line CL extending parallel to the directivity axis. Specifically, the longitudinal center line CL substantially coincides with the directivity axis. In this embodiment, the ultrasonic microphone  3  the ultrasonic microphone  3  is formed in a cylindrical shape extending in an axial direction parallel to the longitudinal center line CL. In other words, the ultrasonic microphone  3  has the outer peripheral surface  30  which is a cylindrical surface and whose generatrix extending parallel to the longitudinal center line CL. 
     The ultrasonic microphone  3  is equipped with the protruding portion  31  and the supported portion  32 . The protruding portion  31  defines a portion of the ultrasonic microphone  3  disposed on a tip side in an axial direction thereof and protrudes frontward from the microphone support  4 . “The tip side”, as referred to herein, means a side of the ultrasonic sensor  1 , i.e., the sensor body  2  where the ultrasonic microphone  3  protrudes and corresponds to a front side in the drawing. 
     The supported portion  32  defines a portion of the ultrasonic microphone  3  which is located on a base side of the ultrasonic microphone  3  in the axial direction and embedded in the microphone support  4 . “The base side in the axial direction”, as referred to herein, is opposite “the tip side in the axial direction” and corresponds to a rear side in the drawing. An end on the base side in the axial direction will also be referred to below as a base end portion. 
     The microphone support  4  is equipped with the elastic supporting member  41  and the sensor case  42 . The elastic supporting member  41  is provided to elastically retain the supported portion  32  of the ultrasonic microphone  3 . The elastic supporting member  41  is made from an elastic synthetic resin material such as silicon rubber. The elastic synthetic resin material is usually called soft synthetic resin, viscoelastic material, or elastomer. 
     Specifically, the elastic supporting member  41  is of a cylindrical outer shape with a bottom and has an opening oriented toward the tip side in the axial direction. The elastic supporting member  41  is designed to have the supported portion  32  of the ultrasonic microphone  3  disposed inside an inner space therein. In this embodiment, the elastic supporting member  41  has a substantially cylindrical outer peripheral surface and a substantially cylindrical inner surface which is placed in close contact with the outer peripheral surface of the ultrasonic microphone  3 . 
     The sensor case  42  is made from a hard synthetic resin, such as polybutylene terephthalate. The hard synthetic resin is not a resinous elastic material, such as elastomer. The sensor case  42  includes the case base  42   a  and the case head  42   b.  The case base  42   a  is of a substantially rectangular parallelepiped box shape in which a circuit board or lead wires (not shown) are disposed. The case base  42   a  is located closer to the base side than the case head  42   b  is in the axial direction. 
     The case head  42   b  is defined by a portion of the sensor case  42  located on the tip side in the axial direction and of a substantially cylindrical shape extending in the axial direction. The case head  42   b  surrounds an outer periphery of the elastic supporting member  41  and has the elastic supporting member  41  disposed therein. In other words, the microphone support  4  is shaped to have the protruding portion  31  which is located on the tip side in the axial direction of the ultrasonic microphone  3  and exposed outside thereof. The microphone support  4  is also shaped to elastically bear the supported portion  32  located on the base side thereof. 
     The sensor body  2  is shaped to be cylindrical and have a shoulder on the sensor case  42  so that the ultrasonic microphone  3  which protrudes outside the case head  42   b  in the axial direction has a decreased diameter. The sensor case  42  has a pair of fastening protrusions  43 . The fastening protrusions  43  project from the outer periphery of the case base  42   a  in a vertical direction perpendicular to the axial direction. 
     In the temporarily assembled condition or a vehicle-mounted condition, the cushion member  5  formed in a cylindrical shape is attached to the sensor body  2 . The cushion member  5  is located closer to the tip side than the case head  42   b  is in the axial direction and covers the protruding portion  31  of the ultrasonic microphone  3  in close contact therewith in the temporarily assembled condition or the vehicle-mounted condition. The cushion member  5  is made from an elastic synthetic resin, such as silicon rubber, in a one-piece form. 
     In this embodiment, the cushion member  5  includes the cylinder  51  and the flange  52 . The cylinder  51  is a cylindrical portion of the cushion member  5  extending in the longitudinal center line CL and has an inner peripheral surface. The inner peripheral surface is formed to create a close contact with a portion of the outer peripheral surface  30  of the ultrasonic microphone  3  which is occupied by the protruding portion  31 . The flange  52  is formed in a ring-shape and radially outwardly protrudes from a base end portion, i.e., a rear end of the cylinder  51  in the axial direction. “Radially” means a direction perpendicular to the longitudinal center line CL. In other words, “radially” or “radial direction” represents a radial direction of an imaginary circle defined around the center that is an intersection of the longitudinal center line CL and a plane defined to have a normal line coinciding with the longitudinal center line CL. “Outward” in the radial direction represents a direction oriented away from the longitudinal center line CL. The flange  52  is placed in contact with an end surface of the case head  42   b  which faces in the axial direction of the case head  42   b  and is located on the tip side of the case head  42   b  in the temporarily assembled condition or the vehicle-mounted condition. 
     In the temporarily assembled condition, the exposed portion  53  of the cushion member  5  which forms a tip side of the cushion member  5  in the axial direction is exposed outside the retainer member  6  in the axial direction. The exposed portion  53  is placed in close contact with the inner peripheral surface V 5  of the mounting hole V 4  in the vehicle-mounted condition where the protruding portion  31  of the ultrasonic microphone  3  is inserted into the mounting hole V 4 . The held portion  54  that is a portion of the cushion member  5  located on the base side in the axial direction is held by the retaining member  6  in the temporarily assembled condition or the vehicle-mounted condition. The held portion  54  includes a base end portion and the flange  52  of the cylinder  51 . 
     The cushion member  5  is designed to have the exposed portion  53  firmly held between the outer peripheral surface  30  of the ultrasonic microphone  3  and the inner peripheral surface V 5  of the mounting hole V 4  in the vehicle-mounted condition. The cushion member  5  is also designed to have the held portion  54  firmly gripped between the outer peripheral surface  30  of the ultrasonic microphone  3  and the retainer member  6  in the temporarily assembled condition and the vehicle-mounted condition. 
     Retainer Member 
     The retainer member  6  is a part or member used to secure the ultrasonic sensors  1 , i.e., the sensor body  2  to the front grille V 3 . The retainer member is also referred to as a retainer portion, a retainer, or a fastener. The structure of the retainer member  6  in this embodiment will be described below in detail with reference to  FIGS. 2 to 5 . 
     The retainer member  6  is, as can be seen in  FIG. 2 , arranged outside the ultrasonic microphone  3  and the microphone support  4  in the radial direction in the temporarily assembled condition or the vehicle-mounted condition. In this embodiment, the retainer member  6  is shaped to have the exposed portion  53  which is located on the tip side in the axial direction of the cushion member  5  and exposed outside the retainer member  6 . The retainer member  6  is configured to have the held portion  54  which is located on the base side in the axial direction of the cushion member  5  and firmly gripped between the retainer member  6  and a portion of the outer peripheral surface  30  of the ultrasonic microphone  3  which is occupied by the protruding portion  31 . 
     The retainer member  6  is formed by a one-piece member made from a hard synthetic resin, such as ABS resin. In this embodiment, the retainer member  6  includes the body retaining portion  61 , the vehicle body-attaching portions  62 , the microphone facing portion  63 , and the fastening portions  64 . 
     The body retaining portion  61  is formed in a hollow cylindrical shape with a bottom and opens at a rear or a base side thereof facing in the backward direction. The body retaining portion  61  is shaped to have at least a portion of the microphone support  4  disposed therein in the temporarily assembled condition and the vehicle-mounted condition. Specifically, the body retaining portion  61  is configured to cover almost the whole of the case base  42   a  from the tip side in the axial direction. 
     The body retaining portion  61  includes the side wall  611  and the bottom wall  612 . The side wall  611  is formed in a cylindrical shape extending in the axial direction. Specifically, the side wall  611  is formed in a rectangular cylindrical shape which is contoured to conform with an outer shape of the case base  42   a.  The bottom wall  612  is configured in a substantially flat plate shape which traverses the axial direction, specifically, extends perpendicular to the axial direction. The bottom wall  612  is arranged to close a tip portion of the side wall  611  in the axial direction. 
     The vehicle body-attaching portions  62  extend from the side wall  611  in an intersecting direction substantially perpendicular to the longitudinal center line CL. The vehicle body-attaching portions  62  are attached to the front grille V 3  using a fastening means, such as welding or screwing, when the ultrasonic sensors  1  is secured to the front grille V 3 . In this embodiment, the retainer member  6  has the two or more vehicle body-attaching portions  62  extending in a direction which is oriented radially and outwardly from the longitudinal center line CL. 
     The microphone facing portion  63  is a portion of the retainer member  6  which is of a cylindrical shape accommodating the ultrasonic microphone  3  in the temporarily assembled condition or the vehicle-mounted condition and is located on the tip side of the retainer member  6  in the axial direction. In other words, the microphone facing portion  63  is located radially outside the ultrasonic microphone  3  and the cushion member  5  in the temporarily assembled condition and the vehicle-mounted condition. The microphone facing portion  63  is configured to grip the held portion  54  of the cushion member  5  between itself and the protruding portion  31  of the ultrasonic microphone  3  in the temporarily assembled condition and the vehicle-mounted condition. 
     In this embodiment, the microphone facing portion  63  is formed in a substantially cylindrical shape extending in the axial direction. Specifically, the microphone facing portion  63  extends from the body retaining portion  61  to the tip side in the axial direction. 
     The microphone facing portion  63  includes the cylindrical portion  630  and the flanged attaching portion  631 . The cylindrical portion  630  is defined by a cylindrical portion of the microphone facing portion  63  and extends from the bottom wall  612  toward the tip side in the axial direction. In this embodiment, the cylindrical portion  630  is arranged to cover the case head  42   b  in the temporarily assembled condition and the vehicle-mounted condition. 
     The flanged attaching portion  631  is formed in a ring shape protruding from an axial tip end of the cylindrical portion  630  radially inwardly. The flanged attaching portion  631  has an inner diameter substantially equal to an outer diameter of the cylinder  51  of the cushion member  5 . The flanged attaching portion  631  is shaped to have an amount by which the flanged attaching portion  631  protrudes radially inwardly and which is substantially equal to that by which the flange  52  of the cushion member  5  protrudes radially outwardly. 
     In other words, the flanged attaching portion  631  is placed in close contact with the cylinder  51  of the cushion member  5  which corresponds to the held portion  54  in the temporarily assembled condition and the vehicle-mounted condition. The flanged attaching portion  631  is also arranged to face the flange  52  of the cushion member  5  in the axial direction and contacts the flange  52  in the temporarily assembled condition and the vehicle-mounted condition. 
     In this embodiment, the microphone facing portion  63  is equipped with the reinforcing ribs  632 . The reinforcing ribs  632  are arranged on an outer peripheral surface of the cylindrical portion  630 . The reinforcing ribs  632  protrude from the outer peripheral surface of the cylindrical portion  630  radially outwardly and also extend from the bottom wall  612  of the body retaining portion  61  in the axial direction. In other words, the reinforcing ribs  632  are joined both to the bottom wall  612  and to the cylindrical portion  630  in the form of a one-piece member. 
     The fastening portions  64  are each formed in a tongue-plate shape and extend from the microphone facing portion  63  toward the base side in the axial direction along the longitudinal center line CL. In this embodiment, the fastening portions  64  include a pair of upper and lower fasteners. Specifically, the two fastening portions  64  are diametrically opposed to each other about the longitudinal center line CL. In other words, the fastening portions  64  are located symmetrically with each other with respect to the longitudinal center line CL. 
     Each of the fastening portions  64  is equipped with the engaging portion  65 . The engaging portion  65  is defined by a through-hole extending through a thickness of the fastening portion  64  in the vertical direction. The engaging portion  65  serves as an engaging hole which achieves mechanical engagement with the fastening protrusion  43  on the case base  42   a  of the sensor body  2  and is located in coincidence with the fastening portion  43  in the temporarily assembled condition and the vehicle-mounted condition. The retainer member  6  serves to have the case base  42   a  disposed in inner space of the body retaining portion  61  and achieves joints of the fastening protrusions  43  to the engaging portions  65 , thereby holding the sensor body  2  therein. 
     The fastening portions  64  are formed in a cantilever shape to be swingable in the radial direction, i.e., a thickness-wise direction thereof within the respective moulded holes  66 . The moulded holes  66  pass through the body retaining portion  61  and the vehicle body-attaching portions  62  in the axial direction, i.e., the front-back direction. In this embodiment, fixed ends that are ends of the fastening portions  64  located on the tip side in the axial direction are rigidly joined to the microphone facing portion  63  substantially at the middle of the length of the cylindrical portion  630 . The engaging portions  65  are located closer to free ends of the fastening portions  64  than to the fixed ends. The free end of each of the fastening portions  64  is an end of the fastening portion  64  located on the base side in the axial direction of the fastening portion  64 . 
     The microphone facing portion  63  has formed in a lower end thereof the drain path  67  which extends through the microphone facing portion  63  or the fastening portions  64  in the radial direction, i.e., the vertical direction. The drain path  67  serves to drain water from an inner space SP in the microphone facing portion  63 . In other words, the drain path  67  is capable of discharging water from a gap between the microphone facing portion  63  and the cushion member  5 . 
     In this embodiment, the drain path  67  extends both in the microphone facing portion  63  and a lower one of the fastening portions  64 . Specifically, the drain path  67  extends from the microphone facing portion  63  to near the root (i.e., the fixed end) of the fastening portion  64 . 
     In this embodiment, the drain path  67  has formed in an axial end portion thereof the opening  68  which is oriented in the axial direction. In other words, the drain path  67  is defined by a cutout portion or slit extending from the flanged attaching portion  631  toward the base side in the axial direction. In this embodiment, the drain path  67  has a width or an opened lateral dimension substantially kept constant in the axial direction. 
     The microphone facing portion  63  has the stamped wall portion  69  formed in an upper end portion thereof. Specifically, the stamped wall portion  69  is diametrically opposed to the drain path  67  through the longitudinal center line CL. In other words, the microphone facing portion  63  has the drain path  67  and the stamped wall portion  69  arranged symmetrically with each other with respect to the longitudinal center line CL. 
     In this embodiment, the stamped wall portion  69  passes through the microphone facing portion  63  in the radial direction. Specifically, the stamped wall portion  69  is, like the drain path  67 , formed by a slit communicating between outside the retainer member  6  and the inner space SP in the retainer member  6 . 
     The stamped wall portion  69  is aligned with the drain path  67 . In other words, the stamped wall portion  69  in this embodiment extends both in the microphone facing portion  63  and in an upper one of the fastening portions  64 . The stamped wall portion  69  is formed by a cutout or a slit which extends from the flanged attaching portion  631  toward the base side in the axial direction and has an opening oriented to the tip side in the axial direction. The stamped wall portion  69  has a width or lateral opened dimension kept substantially constant in the axial direction and identical with that of the drain path  67 . In other words, the stamped wall portion  69  is formed to have the same shape as that of the drain path  67 . 
     As apparent from the above discussion, the microphone facing portion  63  is made of two sections: a right and a left section isolated by the drain path  67  and the stamped wall portion  69  made of slits arranged away from each other in the vertical direction. In other words, a pair of flanged attaching portions  631  which are isolated from each other by the drain path  67  and the stamped wall portion  69  which are vertically arranged are disposed away from each other in the lateral direction. 
     Each of the right and left sections of the microphone facing portion  63  is equipped with two reinforcing ribs  632 . Specifically, one of the two discrete sections of the microphone facing portion  63  has the two reinforcing ribs  632 , while the other section also has the two reinforcing ribs  632 . 
     The total of four reinforcing ribs  632  are arranged symmetrically with each other both in the vertical direction and in the lateral direction. Specifically, an upper one of the reinforcing ribs  632  of one of the discrete sections of the microphone facing portion  63  and a lower one of the reinforcing ribs  632  of the other section of the microphone facing portion  63  are located symmetrically with respect to the longitudinal center line CL. Similarly, a lower one of the reinforcing ribs  632  of one of the discrete sections of the microphone facing portion  63  and an upper one of the reinforcing ribs  632  of the other section of the microphone facing portion  63  are located symmetrically with respect to the longitudinal center line CL. 
     In this embodiment, the four reinforcing ribs  632  are arranged at angular or circumferential positions of 45°, 135°, 225°, and 315° in a circumferential direction which will be defined later. The circumferential direction is a direction surrounding the longitudinal center line CL. In other words, the circumferential direction is identical with a circumferential direction of the above described imaginary circle. The circumferential positions are points on the imaginary circle indicated by a chain double-dashed line in  FIG. 4  and expressed by angles. The center of the width of the stamped wall portion  69  in the circumferential direction is determined as a reference position for the circumferential positions expressed by angles and defined as 0°. The center of the width of the drain path  67  is defined as 180°. 
     Beneficial Effects 
     The beneficial effects offered by the structure in this embodiment will be described below with reference to the drawings. 
     In the structure in this embodiment, the engaging portion  65  in each of the fastening portions  64  extending from the microphone facing portion  63  of the retainer member  6  engages a corresponding one of the fastening protrusions  43  on the sensor body  2  of the ultrasonic sensor  1 . This establishes the temporarily assembled condition or the vehicle-mounted condition in which the retainer member  6  is secured to the ultrasonic sensor  1 . 
     Upon attachment of the retainer member  6  to the ultrasonic sensor  1 , the body retaining portion  61  has a portion of the microphone support  4  of the sensor body  2 , i.e., the case base  42   a  disposed therein. The microphone facing portion  63  of the retainer member  6  is located radially outside the ultrasonic microphone  3  of the sensor body  2 . The ultrasonic microphone  3  is, therefore, disposed in the inner space SP of the microphone facing portion  63 . 
     The microphone facing portion  63  has the exposed portion  53  which is located on the tip side of the cushion member  5  in the axial direction and exposed outside the microphone facing portion  63 . The microphone facing portion  63  grips the held portion  54  of the cushion member  5  located on the base side in the axial direction of the cushion member  5  between itself and a portion of the outer peripheral surface  30  of the ultrasonic microphone  3  corresponding to the protruding portion  31 . 
     The flanged attaching portion  631  which is formed by the tip end of the length of the microphone facing portion  63  is placed in close contact with a portion of the cylinder  51  of the cushion member  5  corresponding to the held portion  54 . The flanged attaching portion  631  faces the flange  52  of the cushion member  5  in the axial direction and contacts the flange  52 . The flanged attaching portion  631 , therefore, stops the held portion  54  of the cushion member  5  from being moved. The protruding portion  31  of the ultrasonic microphone  3  is shield or covered with the exposed portion  53  of the cushion member  5  in close contact with the exposed portion  53  and disposed in the mounting hole V 4  of the front grille V 3  in the vehicle-mounted condition. 
     When it is raining or the vehicle is being washed in the vehicle-mounted condition, there is a risk that water may enter a portion of each of the ultrasonic sensors  1  joined to the front grille V 3 . Specifically, water may be admitted from outside the vehicle body V 1  into an air gap between the inner peripheral surface V 5  of each of the mounting holes V 4  in the front grille V 3  and the cushion member  5 . 
     A portion of the ultrasonic sensor  1  joined to the front grille V 3  may have an air gap into which water is admitted from outside the ultrasonic sensor  1 . For instance, a gap may be formed between the ultrasonic microphone  3  and the microphone facing portion  63  of the retainer member  6 . Specifically, such an air gap is typically created between the front grille V 3  and/or the retainer member  6  and the cushion member  5  around the mounting hole V 4  in the front grille V 3 . 
     For example, an air gap into which water is admitted may occur among the tip of the flanged attaching portion  631  in the axial direction, the back surface of the front grille V 3 , and the outer peripheral surface of the exposed portion  53  of the cushion member  5 . Additionally, an air gap into which water is admitted may occur between the cushion member  5  and the retainer member  6 , i.e., between the cushion member  5  and the microphone facing portion  63 . This may cause water to enter the above air gap from outside the front grille V 3 . When such water is accumulated, it may result in an increase in unwanted reflected waves arising from propagation of vibration through the accumulated water, which leads to an error in detection of an object. 
     In contrast to the above, the retainer member  6  in this embodiment is equipped with the drain path  67 . The drain path  67  is formed to radially pass through the microphone facing portion  63  and the fastening portion  64  extending from the microphone facing portion  63 . Specifically, the drain path  67  radially passes through the microphone facing portion  63  and the fastening portions  64  at a lower end portion of the microphone facing portion  63  to communicate between the above described air gap and an external space below the retainer member  6 . 
     The drain path  67  is, therefore, capable of discharging water from the inner space SP in the microphone facing portion  63  to the outside. The water having entered the air gap is, thus, drained to the external space below the retainer member  6  through the drain path  67 , thereby avoiding undesirable accumulation of water in the air gap. 
     The formation of the drain path  67  will result in a decrease in mechanical stiffness of the microphone facing portion  63  and the fastening portion  64 , thereby resulting in imbalance in stiffness between areas of the microphone facing portion  63  which face each other across the longitudinal center line CL or between the fastening portions  64 . This leads to deterioration of fixation of the ultrasonic sensor  1  in the vehicle-mounted condition. 
     In order to alleviate the above problem, the retainer member  6  in this embodiment is equipped with the stamped wall portion  69 . The stamped wall portion  69  is formed in the microphone facing portion  63   a  and the fastening portions  64  and opposed to the drain path  67  across the longitudinal center line CL. The stamped wall portion  69  is arranged to face the drain path  67 . Specifically, the drain path  67  is formed in the microphone facing portion  63 . Similarly, the stamped wall portion  69  is also formed in the microphone facing portion  63 . The drain path  67  is also formed in the fastening portions  64 . Similarly, the stamped wall portion  69  is also formed in the fastening portions  64 . More specifically, the stamped wall portion  69  is, like the drain path  67 , formed to pass both through the microphone facing portion  63  and through the fastening portions  64  in the radial direction. 
     With the above arrangements, the formation of the drain path  67  results in a decrease in stiffness of the microphone facing portion  63  and the fastening portion  64 . The formation of the stamped wall portion  69  also results in a decrease in stiffness of the microphone facing portion  63  and the fastening portion  64 . The stamped wall portion  69  and the drain path  67  face each other through the longitudinal center line CL in the microphone facing portion  63  and the fastening portions  64  This minimizes the imbalance in stiffness between the areas facing each other through the longitudinal center line CL. 
     Specifically, the microphone facing portion  63  has formed therein the drain path  67  and the stamp wall portion  69  which radially pass through the thickness of the microphone facing portion  63  and face each other across the longitudinal center line CL. This minimizes the imbalance in stiffness of areas of the cylindrical microphone facing portion  63  which are opposed to each other through the longitudinal center line CL. 
     The instability in gripping the cushion member  5  covering the ultrasonic microphone  3  using the microphone facing portion  63  is, therefore, eliminated. In other words, the degree to which the flanged attaching portion  631  firmly grips the cushion member  5  is uniformed in the circumferential direction thereof. This minimizes a risk that the cushion member  5  may be undesirably deformed at a location of the drain path  67 , thereby removal of the cushion member  5  from the outer periphery of the ultrasonic microphone  3 . 
     In this embodiment, the drain path  67  is shaped to extend both in the microphone facing portion  63  and in a first one of the fastening portions  64 , thereby facilitating discharge of water which has entered an air gap between the retainer member  6  and the cushion member  5  to external space below the drain path  67 . 
     The stamped wall portion  69  is, like the drain path  67 , shaped to extend both in the microphone facing portion  63  and in a second one of the fastening portions  64 . In other words, the drain path  67  which radially extends through the thickness of the fastening portion  64  and the stamped wall portion  69  which radially extends through the thickness of the fastening portion  64  are opposed to each other through the longitudinal center line CL. 
     The above arrangements eliminates imbalance in retaining the sensor case  42  between the first fastening portion  64  in which the drain path  67  is formed and the second fastening portion  64  in which the stamped wall portion  69  is formed. In other words, the imbalance in retaining the sensor case  42  which will arise from the formation of the drain path  67  only in a lower one of the fastening portions  64  is eliminated. 
     In this embodiment, the drain path  67  has the opening  68  oriented in the axial direction. In other words, the drain path  67  is formed by a cutout or a slit extending from the flanged attaching portion  631  toward the base side in the axial direction. 
     Water, as described above, may enter an air gap among the tip of the flanged attaching portion  631  in the axial direction, the back surface of the front grille V 3 , and the outer peripheral surface of the exposed portion  53  of the cushion member  5 . Such water is, however, discharged by the drain path  67  to external space below the drain path  67 . 
     This embodiment also eliminates the risk, as described above, that water may enter an air gap created in a joint of the ultrasonic sensor  1  to the front grille V 3  and then be accumulated therein using the drain path  67 . This minimizes a failure in operation of the ultrasonic sensor  1  due to entry of rain thereinto in the vehicle-mounted condition. 
     This embodiment has the stamped wall portion  69  in addition to the drain path  67 , thereby, as described above, minimizing the imbalance in stiffness between portions of the microphone facing portion  63  and the fastening portions  64  which face each other across the longitudinal center line CL and also eliminating the risk of a failure in operation of the ultrasonic sensor  1  due to entry of water, such as rain, thereinto in the vehicle-mounted condition. This embodiment, thus, provides a suitable means for solving the problem with discharge of water from a joint of the ultrasonic sensor  1  to a vehicle body component, such as the front grille V 3 , using the retainer member  6 . 
     When the ultrasonic sensors  1  are required to be attached to the bumper V 2 , it may be preferably made without encountering the above problems by forming, like in the above patent literature 1, sensor fastening ribs with drain holes on an inner surface of the bumper V 2 . It is, however, difficult to form ribs with drain holes, like on the bumper V 2 , on the front grille V 3  in terms of design or structure thereof. 
     Accordingly, this embodiment is designed not to have the drain path  67  formed in the front grille V 3 , but in the retainer member  6  for use in attaching the sensor body  2  to the front grille V 3 . This enables a vehicle body component, such as the front grille V 3 , which has a relatively small continuous surface area and a complicated shape to be free from the problem of water draining. 
     In this embodiment, the cylindrical portion  630  is designed to have the reinforcing ribs  632  formed thereon. The reinforcing ribs  632  protrude radially outward and extend from the bottom wall  612  in the axial direction. In other words, each of the reinforcing ribs  632  is integrally joined both to the bottom wall  612  and to the cylindrical portion  630 . 
     With the above arrangements, the microphone facing portion  63  and the flanged attaching portion  631  are mechanically reinforced by the reinforcing ribs  632 . In other words, the reinforcing ribs  632  serve to minimize radially outward deformation of the microphone facing portion  63  due to pressure internally exerted on the inner periphery thereof when the retaining member  6  is secured to an assembly of the sensor body  2  and the cushion member  5 . The cushion member  5  is well retained even in the case where the rain path  67  is designed to have an increased width or the drain path  67  and the stamped wall portion  69  are formed as a pair to be aligned with each other in the vertical direction. 
     Modifications 
     This disclosure is not limited to the above embodiment. The above embodiment may, therefore, be modified in various ways. Principal modifications of the embodiment will be described below. The following discussion will mainly refer to differences from the above embodiment. The same or similar reference numbers as employed in the above embodiment will refer to the same or similar parts, and explanation thereof in detail will be omitted here unless otherwise specified. 
     This disclosure is not limited to attachment of the ultrasonic sensors  1  to the front grille V 3 . Specifically, the above embodiment may be realized when the ultrasonic sensors  1  are attached to the bumper V 2 . The above embodiment may alternatively be realized when the ultrasonic sensors  1  are attached to a vehicle body panel. The attachment of the ultrasonic sensors  1  to the bumper V 2  or the vehicle body panel may be achieved by modifying the structure of the retainer member  6  to match the structure of the bumper V 2  or the vehicle body panel. 
     The ultrasonic sensors  1  are not limited to the structure capable of transmitting and receiving an ultrasonic wave. For instance, the ultrasonic sensors  1  may be engineered only to transmit an ultrasonic wave. The ultrasonic sensors  1  may alternatively be designed only to receive a return of an ultrasonic wave or a radar wave which has been outputted from another ultrasonic sensor and reflected by an object existing around the vehicle V. 
     The structures of the sensor body  2 , the cushion member  5 , and the retainer member  6  are not limited to those described in the above embodiment. Details of the structures of the sensor body  2 , the cushion member  5 , and the retainer member  6  may be modified unless they decrease the beneficial effects offered in this disclosure. 
     In the above embodiment, the fastening portions  64  extend from a portion of the cylindrical portion  630 , as located closer to the tip side than the bottom wall  612  is, toward the base side in the axial direction. In other words, fixed ends of the fastening portions  64  which are jointed to the microphone facing portion  63  are located closer to the tip side (i.e., the front side) than the bottom wall  612  is. This disclosure is, however, not limited to the above arrangements. For instance, the fixed ends of the fastening portions  64  may alternatively be located closer to the base side (i.e., the rear side) than the bottom wall  612  is. 
     The configuration of the drain path  67  is not limited to that described above. For instance, the drain path  67  may be designed not to have the opening  68  on the tip side in the axial direction. Specifically, the drain path  67  may be shaped to have a tip closed by a bridge formed on the microphone facing portion  63 . 
     The width of the drain path  67  may not necessarily be constant in the axial direction. Specifically, the drain path  67  may be shaped to have a first width in the fastening portion  64  and also have a second width in the microphone facing portion  63  which is large than the first width. The drain path  67  may alternatively be shaped to have a maximum width in the opening  68 . Such structures well facilitate the draining of water from an air gap created in a joint of the ultrasonic sensor  1  to the front grille V 3 . 
       FIGS. 6 and 7  illustrate a modification of the retainer member  6  in  FIGS. 3 to 5 . Specifically, the drain path  67 , as can be seen in  FIGS. 6 and 7 , has a first width on the tip side and a second width on the base side. The first width is larger than the second width. Specifically, the drain path  67  is shaped to have the first width in the flanged attaching portion  631  and the second width in the cylindrical portion  630 . The first width is selected to be larger than the second width. In other words, the drain path  67  has a maximum width in the flanged attaching portion  631 , i.e., the opening  68 . The stamped wall portion  69  has the same shape as that of the drain path  67 . 
     More specifically, a portion of the drain path  67  formed in the flanged attaching portion  631  has the first width which, as can be seen in  FIG. 7 , occupies a central angle θ in a plan view which is larger than 20° or more and smaller than 90° or less in the circumferential direction. A portion of the drain path  67  in the fastening portion  64  has a minimum width in a fixed end thereof and also has a constant width, as viewed facing the side of the drain path  67 . The drain path  67  in the cylindrical portion  630  has the above maximum width on the tip side in the axial direction. The drain path  67  in the cylindrical portion  630  also has the above minimum width in a joint with the fastening portion  64 . The drain path  67  in the cylindrical portion  630  is stepwisely shaped to widen from the minimum with to the maximum width. 
     The flanged attaching portion  631  is, therefore, shaped to have a given width in the circumferential direction to firmly retain the cushion member  5  in the lateral direction in the vehicle-mounted condition. In other words, the cushion member  5  is firmly held by the flanged attaching portion  631  in the lateral direction. 
     The drain path  67  is, therefore, placed in the vehicle-mounted condition to have a relatively large opening oriented downward. This creates a clearance which lies between the front grille V 3  and the retainer member  6  in the vehicle-mounted condition and is capable of downward discharging water, as having entered into an air gap between the retaining member  6  and the cushion member  5 , regardless of the configuration of the front grille V 3 . This ensures the stability in discharging water, as having reached the air gap among the axial tip of the flanged attaching portion  631 , the back surface of the front grille V 3 , and the outer peripheral surface of the exposed portion  53  of the cushion member  5 , downward from the drain path  67 . 
     As an alternative to the above modification, the drain path  67  may be shaped to have a first width in the fastening portions  64  and a second width in the microphone facing portion  63  which is smaller than the first width. This enhances a mechanical joint of the flanged attaching portion  631  with the cushion member  5  without sacrificing the ability in draining water. 
     Each of the drain path  67  and the stamped wall portion  69  may alternatively be formed only in one of the microphone facing portion  63  and the fastening portions  64 . Specifically, each of the drain path  67  and the stamped wall portion  69  may be formed only in the microphone facing portion  63 . 
     Each of the drain path  67  and the stamped wall portion  69  may alternatively be formed only in the fastening portions  64 . This enhances the mechanical strength of the microphone facing portion  63  without sacrificing the ability in draining water from the clearance between the retainer member  6  and the cushion member  5 . 
     In the above embodiment, the drain path  67  and the stamped wall portion  69  coincide with the fastening portions  64  in a circumferential direction defined around the longitudinal center line CL, but however, this disclosure is not limited to such arrangements. 
     Specifically, each of the drain path  67  and the stamped wall portion  69  may alternatively be formed in the microphone facing portion  63  and located away from the fastening portions  64  in the circumferential direction. In such a case, the two fastening portions  64  are provided and face each other in the lateral direction. This layout minimizes a change in joining ability of the fastening portions  64  which is caused by the drain path  67  and the stamped wall portion  69 . 
     The shape of the stamped wall portion  69  is not limited to that referred to in the above embodiment. For instance, the stamped wall portion  69  may be formed to be different in shape from the drain path  67 . As an example, the stamped wall portion  69  may have a width which is different from that of the drain path  67  or alternatively be different in distribution in width from the drain path  67  in the axial direction. 
     Specifically, the stamped wall portion  69  in  FIGS. 6 and 7  may be designed to have the same shape as in  FIG. 3 . The stamped wall portion  69  may alternatively be implemented by a plurality of small through-holes formed in the microphone facing portion  63 . 
     The stamped wall portion  69  may be defined by a hole shaped not to extend thorough the microphone facing portion  63  in the radial direction thereof. In other words, the stamped wall portion  69  may be created by a thin-walled portion of the microphone facing portion  63 . 
     In the above embodiment, each of the two discrete sections of the microphone facing portion  63  is equipped with the two reinforcing ribs  632 , but however, this disclosure is not limited to such arrangements. For instance, the number of the reinforcing ribs  632  is not limited to two as long as the discrete sections of the microphone facing portion  63  have the same number of the reinforcing ribs  632 . For instance, each of the discrete sections of the microphone facing portion  63  may have a single reinforcing rib  632  or three reinforcing ribs  632  formed thereon. 
     The reinforcing ribs  632  may be, as illustrated in  FIG. 8 , shaped to have the through-hole  633  formed therein. The through-hole  633  extends through the thickness of a root portion of each of the plate-like reinforcing ribs  632  in the circumferential direction. The root portion of the reinforcing rib  632  corresponds to an axial end of the reinforcing ribs  632  located on the base side, that is, a joint thereof with the bottom wall  612 . The through-hole  633  minimizes a risk that water may be accumulated on the root portion of the reinforcing rib  632 . 
     A plurality of component parts which are formed integrally with each other in a seamless way referred to in the above discussion may alternatively be made of a plurality of discrete parts attached to each other. Similarly, an assembly of discrete parts joined together referred to in the above discussion may alternatively be made of a single seamless member without any joint. 
     A plurality of component parts, as referred to in the above discussion, which are made from the same material may alternatively be made from materials different from each other. Similarly, a plurality of component parts, as referred to in the above discussion, which are made from different materials may be made from the same material. 
     The term “part or component part”, as referred to in this disclosure, does not necessarily mean an integrally-formed member which is mechanically inseparable. For instance, a portion of each of the retainer members  6  may be designed to be removable from another portion thereof. The term “removable” means that an ordinary user other than skilled people can easily detach a portion of the retainer member  6  with or without any tool, such as a screw driver. 
     The component parts described in the above embodiment are not necessarily essential unless otherwise specified or viewed to be essential in principle. When the number of the component parts, a numerical number, a volume, or a range is referred to in the above discussion, this disclosure is not limited to it unless otherwise specified or viewed to be essential in principal. Similarly, when the shape of, the orientation of, or the positional relation among the component parts is referred to in the above discussion, this disclosure is not limited to it unless otherwise specified or viewed to be essential in principal. 
     The modifications are also not limited to the above described examples. A portion or whole of the embodiment may be combined with one or some of the modifications.