Patent Publication Number: US-2020284890-A1

Title: Ultrasonic sensor and retainer

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority from Japanese Patent Application No. 2017-227063 filed Nov. 27, 2017 and Japanese Patent Application No. 2018-157614 filed Aug. 24, 2018, the descriptions of which are incorporated herein by reference. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to an ultrasonic sensor and a retainer which is a component for attaching and fixing the ultrasonic sensor to an auto body component. 
     Related Art 
     A mounting structure for an ultrasonic sensor is disclosed in which the performance thereof is not adversely affected by infiltration of water or the like. 
     SUMMARY 
     As an aspect of the present disclosure, an ultrasonic sensor is configured to be attached to an auto body component. The ultrasonic sensor includes: a sensor body including an ultrasonic microphone having a columnar shape and extending along an axial direction parallel to a central axis line and a microphone support unit which allows a protruding part of the ultrasonic microphone to protrude and supports a supported part of the ultrasonic microphone, the protruding part being located at a distal end in the axial direction, the supported part being located at a proximal end in the axial direction; a cushion member provided to cover the protruding part of the ultrasonic microphone and formed in a cylindrical shape from a synthetic resin-based elastic material; a retainer unit provided outward of the ultrasonic microphone in a radial direction extending from the central axis line, the retainer unit being configured so that an exposed part of the cushion member is exposed and a sandwiched part of the cushion member is sandwiched between the retainer unit and an outer peripheral surface of the protruding part of the ultrasonic microphone, the exposed part being located at the distal end in the axial direction, the sandwiched part being located at the proximal end in the axial direction; and a drainage path penetrating the retainer unit in the radial direction to allow water to be discharged out of the retainer unit from a gap between the retainer unit and the cushion member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is an external view of a vehicle in which an ultrasonic sensor according to an embodiment is installed; 
         FIG. 2  is a lateral cross-sectional view of the ultrasonic sensor illustrated in  FIG. 1 ; 
         FIG. 3  is a perspective view illustrating an external appearance of a retainer unit illustrated in  FIG. 2 ; 
         FIG. 4  is a perspective view illustrating an external appearance of a retainer unit according to one modification; 
         FIG. 5  is a perspective view illustrating an external appearance of a retainer unit according to another modification; 
         FIG. 6  is a perspective view illustrating an external appearance of a retainer unit according to yet another variation; 
         FIG. 7  is a perspective view illustrating an external appearance of a retainer unit according to yet another variation; 
         FIG. 8  is a plan view of the retainer unit illustrated in  FIG. 7 ; and 
         FIG. 9  is a magnified side view illustrating the configuration of one modification of a reinforcement rib illustrated in  FIGS. 7 and 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     JP 3999187 B discloses a mounting structure for an ultrasonic sensor in which the performance thereof is not adversely affected by infiltration of water or the like. Specifically, in the mounting structure disclosed in JP 3999187 B, a hole is formed in an outer plate exposed on the exterior, and the ultrasonic sensor is inserted into this hole. A rib for fixing the ultrasonic sensor is provided to an inner surface of the outer plate. The ultrasonic sensor is fixed to this rib via a vibration dampener. The outer plate, the rib, or the vibration dampener has a drainage hole vertically below the ultrasonic sensor. The drainage hole is connected to a space formed between a casing for the ultrasonic sensor and the outer plate, the rib, or the vibration dampener. 
     A known in-vehicle ultrasonic sensor is primarily attached to a bumper. This means that for a known in-vehicle ultrasonic sensor, the aforementioned “outer plate” is primarily a bumper. In the case where the ultrasonic sensor is attached to the bumper, providing a waterproof structure at an attachment portion is relatively easy. Therefore, in this case, the amount of water infiltration at the attachment portion is relatively small. Furthermore, even if water infiltration occurs, good drainage is possible through the aforementioned drainage hole. 
     Meanwhile, there can be cases where the in-vehicle ultrasonic sensor is attached to a front grille for reasons of obstacle sensing performance, vehicle designs, or the like. In these cases, providing the aforementioned drainage hole in the front grille is difficult from the design or structural perspective. If incoming water is retained at a portion where the ultrasonic sensor is attached to an auto body component such as the bumper or the front grille, the propagation of vibration through the retained water may cause an increase in unnecessary reflected waves, causing problems such as false detection. 
     The present disclosure is conceived in view of the above-cited circumstances and so on. Specifically, the present disclosure provides a configuration of an ultrasonic sensor which is configured to be attachable to an auto body component and in which degradation in the performance of the in-vehicle ultrasonic sensor that is caused by infiltration of water due to rain or the like can be sufficiently suppressed. 
     Hereinafter, an embodiment will be described with reference to the drawings. For the purpose of illustration, the forward, backward, left, right, upward, and downward directions in the configuration according to the present embodiment are defined by arrows in the drawings. Note that various applicable variations of one embodiment will be collectively described after the description of the embodiment because insertion of such variations into the sequential description about the embodiment may inhibit understanding of the embodiment. 
     Configuration 
     In  FIG. 1 , a vehicle V is what is called a four-wheeled vehicle and includes a vehicle body V 1  which is substantially rectangular in a plan view. A bumper V 2  and a front grille V 3  which are auto body components are attached to a front end portion of the vehicle body V 1 . The front grille V 3  is disposed above the bumper V 2 . Note that the vertical direction herein is defined assuming an installed-in-vehicle state in which an ultrasonic sensor  1  is attached to the front grille V 3 . Therefore, the vertical direction in the description of the configuration of each part of the ultrasonic sensor  1  is premised on an attitude in the installed-in-vehicle state. 
     A fitting hole V 4  which is a through-hole for fitting the ultrasonic sensor  1  is formed in each of the bumper V 2  and the front grille V 3 . Specifically, in the present embodiment, fitting holes V 4  are provided at both corner portions of the bumper V 2 . Furthermore, two fitting holes V 4  are symmetrically provided in the front grille V 3 . 
     The ultrasonic sensor  1  is configured to be attached to each of the bumper V 2  and the front grille V 3 . Hereinafter, with reference to  FIGS. 2 and 3 , details of the configuration of the ultrasonic sensor  1  that is attached to the front grille V 3  will be described. 
     In  FIG. 2 , a sensor body  2  constituting the body part of the ultrasonic sensor  1  includes an ultrasonic microphone  3  and a microphone support unit  4 . Furthermore, in the present embodiment, a cushion member  5  and a retainer unit  6  are included as components for fitting the ultrasonic sensor  1  to the front grille V 3 . 
     The ultrasonic microphone  3  is configured to be able to transmit and receive ultrasonic waves. Specifically, the ultrasonic microphone  3  is configured to transmit probe waves along a directional axis and receive reflected waves from an object located near the vehicle V. 
     The ultrasonic microphone  3  has a columnar contour having a central axis line CL parallel to the directional axis. Specifically, in the present embodiment, the ultrasonic microphone  3  is formed in the shape of a circular column extending along an axis parallel to the central axis line CL. In other words, the ultrasonic microphone  3  has an outer peripheral surface  30  which is a cylindrical surface having a generatrix parallel to the central axis line CL. 
     The ultrasonic microphone  3  includes a protruding part  31  and a supported part  32 . The protruding part  31  is a distal end portion of the ultrasonic microphone  3  in the axial direction and protrudes forward from the microphone support unit  4 . The wording “the distal end . . . in the axial direction” indicates a front area of the ultrasonic sensor  1 , specifically, the sensor body  2 , in the drawings in which the ultrasonic microphone  3  protrudes. The supported part  32  is a proximal end portion of the ultrasonic microphone  3  in the axial direction and is embedded within the microphone support unit  4 . The wording “the proximal end . . . in the axial direction” indicates the area opposite to the area indicated by the wording “the distal end . . . in the axial direction”. 
     The microphone support unit  4  includes an elastic support member  41  and a sensor case  42 . The elastic support member  41  is formed from a synthetic resin-based elastic material such as silicone rubber so as to elastically support the supported part  32  of the ultrasonic microphone  3 . Specifically, the elastic support member  41  has a bottomed cylindrical contour that is open toward the distal end in the axial direction and is configured to house the supported part  32  of the ultrasonic microphone  3  in an inner space. 
     The sensor case  42  is integrally formed from a hard synthetic resin such as polybutylene terephthalate. The sensor case  42  is configured to house the elastic support member  41  at the distal end portion in the axial direction while covering the outer peripheral surface of the elastic support member  41 . In other words, the microphone support unit  4  is configured to elastically support the supported part  32  of the ultrasonic microphone  3  at the proximal end in the axial direction while allowing the protruding part  31  of the ultrasonic microphone  3  at the distal end in the axial direction to protrude. 
     The sensor body  2  is formed in the shape of a stepped column in which the ultrasonic microphone  3  protruding, from the sensor case  42 , toward the distal end in the axial direction is a reduced diameter portion. A plurality of engagement protrusions  43  are provided on the sensor case  42 . The engagement protrusions  43  vertically protrude from the outer peripheral surface of the sensor case  42 . 
     The cushion member  5  is provided to cover the protruding part  31  of the ultrasonic microphone  3  in close contact. The cushion member  5  is seamlessly integrally formed from a synthetic resin-based elastic material such as silicone rubber. The synthetic resin-based elastic material is also referred to as a viscoelastic material or an elastomer. 
     The cushion member  5  is configured to be sandwiched between the outer peripheral surface  30  of the ultrasonic microphone  3  and an inner peripheral surface V 5  of the fitting hole V 4  when the protruding part  31  of the ultrasonic microphone  3  is inserted into the fitting hole V 4 . In the present embodiment, the cushion member  5  includes a cylindrical part  51  and a flange part  52 . 
     The cylindrical part  51  is a circular cylindrical part provided along the central axis line CL and has an inner peripheral surface like the inner surface of a circular cylinder. This inner peripheral surface is formed so as to closely contact a portion of the outer peripheral surface  30  of the ultrasonic microphone  3  that corresponds to the protruding part  31 . The flange part  52  is formed in the shape of a ring protruding outward in a radial direction from a proximal end portion, i.e., a rear end portion, of the cylindrical part  51  in the axial direction. The wording “radial direction” means directions radially extending from the central axis line CL. 
     A state where the cushion member  5  and the retainer unit  6  are temporarily attached to the sensor body  2  before the ultrasonic sensor  1  is attached to the front grille V 3  is referred to as a temporarily assembled state. Note that “the temporarily assembled state” is defined for the sake of description of the positional relationship between the respective parts of the ultrasonic sensor  1 . Therefore, there is not always this temporarily assembled state upon attaching the ultrasonic sensor  1  to the front grille V 3 . 
     In the temporarily assembled state, an exposed part  53  of the cushion member  5  which is located at the distal end in the axial direction is exposed from the retainer unit  6 . Furthermore, this exposed part  53  is in close contact with the inner peripheral surface V 5  of the fitting hole V 4  in the installed-in-vehicle state. A sandwiched part  54  of the cushion member  5  which is located at the proximal end in the axial direction is a portion that locks with the retainer unit  6  in the temporarily assembled state and the installed-in-vehicle state and includes the flange part  52  and the proximal end portion of the cylindrical part  51  in the axial direction. 
     The retainer unit  6  is a component used to attach the ultrasonic sensor  1 , specifically, the sensor body  2 , to the front grille V 3 , and is disposed outward of the ultrasonic microphone  3  and the microphone support unit  4  in the radial direction in the temporarily assembled state and the installed-in-vehicle state. In the present embodiment, the retainer unit  6  is configured so that the exposed part  53  of the cushion member  5  which is located at the distal end in the axial direction is exposed and the sandwiched part  54  of the cushion member  5  which is located at the proximal end in the axial direction is sandwiched between the retainer unit  6  and a portion of the outer peripheral surface  30  of the ultrasonic microphone  3  that corresponds to the protruding part  31 . Note that the retainer unit  6  is also referred to as “the retainer member  6 ” or “the retainer  6 ”. 
     The retainer unit  6  is integrally formed from a hard synthetic resin such as an acrylonitrile butadiene styrene (ABS) resin. In  FIGS. 2 and 3 , the retainer unit  6  includes a body holding part  61 , an auto body fixing part  62 , a microphone facing part  63 , and an engagement piece  64 . 
     The body holding part  61  is formed in the shape of a bottomed rectangular cylinder that is open rearward. In other words, the body holding part  61  is configured to cover, in the temporarily assembled state and the installed-in-vehicle state, a portion of the sensor case  42  that is located at the distal end in the axial direction. 
     The auto body fixing part  62  is provided so as to be fixed to the front grille V 3  by a fixing means such as welding or screwing upon attaching the ultrasonic sensor  1  to the front grille V 3 . In the present embodiment, in the retainer unit  6 , a plurality of auto body fixing parts  62  radially extend outward in the radial direction from the central axis line CL. 
     The auto body fixing part  62  extends from a rectangular cylindrical side wall part  611  of the body holding part  61  in a cross direction substantially orthogonal to the central axis line CL. In other words, in the present embodiment, the auto body fixing part  62  is integrally formed with the retainer unit  6 . 
     The microphone facing part  63  is a substantially circular cylindrical portion provided corresponding to the ultrasonic microphone  3  in the temporarily assembled state and the installed-in-vehicle state and is disposed at the distal end of the retainer unit  6  in the axial direction. Specifically, the microphone facing part  63  extends from a bottom wall part  612 , which closes a distal end portion of the rectangular cylindrical side wall part  611  of the body holding part  61  in the axial direction, toward the distal end in the axial direction. The bottom wall part  612  is a plate-shaped portion crossing the axis, specifically, orthogonal to the axis. 
     The microphone facing part  63  is disposed outward of the ultrasonic microphone  3  and the cushion member  5  in the radial direction in the temporarily assembled state and the installed-in-vehicle state. In other words, the microphone facing part  63  is disposed so that the sandwiched part  54  of the cushion member  5  is sandwiched between the microphone facing part  63  and the protruding part  31  of the ultrasonic microphone  3  in the temporarily assembled state and the installed-in-vehicle state. 
     The engagement piece  64  is a tongue-like plate-shaped part and extends along the central axis line CL from the microphone facing part  63  toward the proximal end in the axial direction. In the present embodiment, a pair of engagement pieces  64  are vertically arranged. 
     The engagement piece  64  includes an engagement part  65 . The engagement part  65  is a through-hole and is provided vertically so as to penetrate the engagement piece  64 . The engagement part  65  is an engagement hole for engaging with the engagement protrusion  43  provided to the sensor case  42  included in the sensor body  2  and is disposed at a position corresponding to the engagement protrusion  43  in the temporarily assembled state and the installed-in-vehicle state. In other words, the retainer unit  6  is configured to hold the sensor body  2  by the engagement protrusion  43  engaging with the engagement part  65  while housing the sensor body  2  in the inner space of the body holding part  61 . 
     The microphone facing part  63  includes a flange locking part  66 . The flange locking part  66  is formed in the shape of a ring protruding inward in the radial direction from a distal end portion of a cylindrical part  631  of the microphone facing part  63  in the axial direction. The cylindrical part  631  is a substantially circular cylindrical portion extending from the bottom wall part  612  along the axis. The flange locking part  66  has substantially the same inner diameter as the outer diameter of the cylindrical part  51  of the cushion member  5 . The flange locking part  66  is formed so that the amount of projection in the radial direction is substantially the same as the amount of projection of the flange part  52  of the cushion member  5  in the radial direction. 
     In other words, the flange locking part  66  is formed so as to come into close contact with a portion of the cylindrical part  51  of the cushion member  5  that corresponds to the sandwiched part  54 . Furthermore, the flange locking part  66  is configured to face and abut the flange part  52  of the cushion member  5  along the axis. 
     A drainage path  67  is formed at a lower end portion of the microphone facing part  63 . The drainage path  67  is disposed to penetrate the microphone facing part  63  in the radial direction, i.e., vertically, to allow water to be discharged out of the retainer unit  6  from a gap between the microphone facing part  63  and the cushion member  5 . 
     In the present embodiment, the drainage path  67  is disposed to extend between the microphone facing part  63  and the engagement piece  64 . In other words, the drainage path  67  is disposed from the microphone facing part  63  over to a base portion of the engagement piece  64 . 
     In the present embodiment, a distal end portion of the drainage path  67  in the axial direction has an opening  68  which is open along the axis. In other words, the drainage path  67  is formed as a cutout portion resulting from cutting from the side on which the flange locking part  66  is located toward the proximal end in the axial direction. Furthermore, in the present embodiment, the drainage path  67  is formed so that the widthwise dimension, i.e., the horizontal dimension, of the opening is substantially constant along the axis. 
     Advantageous Effects 
     Hereinafter, advantageous effects provided by the configuration according to the present embodiment will be described with reference to the drawings. 
     The microphone facing part  63  of the retainer unit  6  allows the exposed part  53  of the cushion member  5 , which is located at the distal end in the axial direction, to be exposed and allows the sandwiched part  54  of the cushion member  5 , which is located at the proximal end in the axial direction, to be sandwiched between the microphone facing part  63  of the retainer unit  6  and a portion of the outer peripheral surface  30  of the ultrasonic microphone  3  that corresponds to the protruding part  31 . Specifically, the flange locking part  66  disposed at the distal end portion of the microphone facing part  63  in the axial direction comes into close contact with a portion of the cylindrical part  51  that corresponds to the sandwiched part  54 . Furthermore, the flange locking part  66  faces and abuts the flange part  52  of the cushion member  5  along the axis, thereby locking onto the sandwiched part  54  of the cushion member  5 . 
     The protruding part  31  of the ultrasonic microphone  3  is covered by the exposed part  53  of the cushion member  5  in close contact therewith and is inserted into the fitting hole V 4  of the front grille V 3  in the installed-in-vehicle state. 
     In the installed-in-vehicle state, during rains, in a car wash, or the like, water may enter, from the outside, a portion where the ultrasonic sensor  1  is attached to the front grille V 3 . Specifically, water may enter the attachment portion from the outside of the vehicle body V 1  through a gap between the cushion member  5  and the inner peripheral surface V 5  of the fitting hole V 4  of the front grille V 3 . 
     At the portion where the ultrasonic sensor  1  is attached to the front grille V 3 , there may be a gap in which incoming water is retained. Such a gap is typically formed between the front grille V 3  and/or the retainer unit  6  and the cushion member  5  near the fitting hole V 4  of the front grille V 3 . If incoming water is retained in such a gap, propagation of vibration through the retained water may cause an increase in unnecessary reflected waves, causing trouble such as false detection. 
     In the ultrasonic sensor  1  configured as described above, for example, a gap in which water can be retained may be formed at a portion where the distal end portion of the flange locking part  66  in the axial direction, the rear surface of the front grille V 3 , and the outer peripheral surface of the exposed part  53  of the cushion member  5  face one another. Furthermore, a gap in which water can be retained may be formed between the cushion member  5  and the retainer unit  6 , specifically, between the cushion member  5  and the microphone facing part  63 . Therefore, incoming water may reach these gaps. 
     However, in the ultrasonic sensor  1  according to the present embodiment, the drainage path  67  is formed in the microphone facing part  63  of the retainer unit  6 . The drainage path  67  penetrates the microphone facing part  63  in the radial direction, i.e., vertically, to allow water to be discharged out of the retainer unit  6  from the gap between the retainer unit  6  and the cushion member  5 . In other words, the drainage path  67  is formed so as to connect the gap formed between the retainer unit  6  and the cushion member  5  and the space formed below the ultrasonic sensor  1 . Thus, water that has reached the gap between the retainer unit  6  and the cushion member  5  is discharged into the space below the ultrasonic sensor  1  through the drainage path  67 . 
     Furthermore, in the ultrasonic sensor  1  according to the present embodiment, the drainage path  67  is provided so as to extend between the microphone facing part  63  and the engagement piece  64 . Thus, water that has reached the gap between the retainer unit  6  and the cushion member  5  is favorably discharged into the space below the ultrasonic sensor  1  through the drainage path  67 . 
     Furthermore, with the opening  68  open along the axis, the drainage path  67  is formed as a cutout portion resulting from cutting from the side on which the flange locking part  66  is located toward the proximal end in the axial direction. Thus, water that has reached the gap formed at the portion where the distal end portion of the flange locking part  66  in the axial direction, the rear surface of the front grille V 3 , and the outer peripheral surface of the exposed part  53  of the cushion member  5  face one another is favorably discharged into the space below the ultrasonic sensor  1  through the drainage path  67 . 
     As described above, in the ultrasonic sensor  1  according to the present embodiment, incoming water can be maximally kept from being retained in the gap formed at the portion where the ultrasonic sensor  1  is attached to the front grille V 3 . Therefore, with this configuration, degradation in the performance of the in-vehicle ultrasonic sensor that is caused by infiltration of water due to rain or the like can be sufficiently suppressed. 
     In the case of attaching the ultrasonic sensor  1  to the bumper V 2 , as described in PTL 1, a rib for fixing the sensor can be provided on an inner surface, i.e., a rear surface, of the bumper V 2 , and a drainage hole can be provided in the rib, to optimally reduce the aforementioned problems. However, in the case of attaching the ultrasonic sensor  1  to the front grille V 3 , providing the above rib and drainage hole in the front grille V 3  is difficult from the design or structural perspective. 
     In this regard, in the present embodiment, the drainage path  67  is provided not in the front grille V 3 , but in the retainer unit  6  which is a component for attaching the sensor body  2  to the front grille V 3 . Therefore, with this configuration, even for an auto body component having intricately-shaped continuous surfaces having relatively small areas, represented by the front grille V 3 , a good water removal measure can be applied with a simple structure. 
     Modifications 
     The present disclosure is not limited to the above-described embodiment. Therefore, the above-described embodiment can be changed, as appropriate. Representative modifications will be described below. In the following description of the modifications, differences from the above-described embodiment will be mainly described. In the above-described embodiment and the modifications, the same or equivalent portions are assigned the same reference signs. Thus, in the following description of the modifications, the preceding description in the above-described embodiment can be applied, as appropriate, to a structural element having the same reference sign as that in the above-described embodiment unless there is a technical inconsistency or any additional description is given. 
     The present disclosure is not limited to the embodiment in which the ultrasonic sensor  1  is attached to the front grille V 3 . In other words, the configuration according to the above-described embodiment can be optimally applied to an embodiment in which the ultrasonic sensor  1  is attached to the bumper V 2 . Furthermore, the configuration according to the above-described embodiment can be optimally applied to an embodiment in which the ultrasonic sensor  1  is attached to an auto body panel. In the case of attaching the ultrasonic sensor  1  to the bumper V 2  or the auto body panel, the configuration of the retainer unit  6  may be changed, as appropriate, according to an object to which the ultrasonic sensor  1  is attached. 
     The ultrasonic sensor  1  is not limited to a configuration capable of transmitting and receiving ultrasonic waves. In other words, for example, the ultrasonic sensor  1  may be configured to be only capable of transmitting ultrasonic waves. Alternatively, the ultrasonic sensor  1  may have only the function of receiving waves reflected from an object located near the vehicle V that are probe waves in the form of ultrasonic waves transmitted from another ultrasonic sensor  1 . 
     The configurations of the sensor body  2 , the cushion member  5 , and the retainer unit  6  are not limited to the specific examples described in the above embodiment. In other words, details of the configurations of the sensor body  2 , the cushion member  5 , and the retainer unit  6  can be changed, as appropriate, within a range in which the effects provided according to the present disclosure are not lessened. 
     The shape of the drainage path  67  is not limited to the above-described specific example. In other words, for example, the width of the drainage path  67  does not need to be substantially constant along the axis. Furthermore, the drainage path  67  is not required to have the opening  68  at the distal end in the axial direction. 
       FIG. 4  illustrates one modification of the retainer unit  6  according to the embodiment illustrated in  FIG. 3 . As illustrated in  FIG. 4 , the distal end portion of the drainage path  67  in the axial direction may be closed by a bridge portion  69  provided to the microphone facing part  63 . In other words, the drainage path  67  may be a through-hole provided at the distal end of the retainer unit  6  in the axial direction. With such a configuration, the strength of the microphone facing part  63  can be improved while maintaining favorable drainage performance resulting from the drainage path  67  being provided to extend between the microphone facing part  63  and the engagement piece  64 . Note that in this case, the drainage path  67  may be divided into two or more portions in the axial direction. This means that more than one bridge portion  69  may be provided. 
     Furthermore, in the configuration illustrated in  FIG. 4 , the drainage path  67  is formed so that the width of the drainage path  67  in the engagement piece  64  is greater than the width of the drainage path  67  in the microphone facing part  63 . This enables the flange locking part  66  to more securely lock onto the cushion member  5  while maintaining favorable drainage performance. 
     The drainage path  67  may be provided only in one of the microphone facing part  63  and the engagement piece  64 .  FIG. 5  illustrates an example configuration of the retainer unit  6  when the drainage path  67  is provided only to the engagement piece  64 . With such a configuration, the strength of the microphone facing part  63  can be improved while maintaining favorable performance of drainage from the gap between the retainer unit  6  and the cushion member  5 . 
     In the above-described embodiment, etc., the drainage path  67  is provided at the same position as the engagement piece  64  in a circumferential direction surrounding the central axis line CL. The circumferential direction extends along the circumference of a circle, drawn on a plane having the central axis line CL as a normal thereto, centered on the intersection between the plane and the central axis line CL. However, the present disclosure is not limited to such an embodiment. 
     Specifically, as illustrated in  FIG. 6 , the drainage path  67  may be provided to the microphone facing part  63 , at a position different from the position of the engagement piece  64  in the circumferential direction. In this case, a pair of engagement pieces  64  are horizontally arranged. Such a configuration allows optimal reduction in the trouble resulting from providing the drainage path  67  only to the engagement piece  64  located on the lower side, in other words, the occurrence of the engagement force between the pair of engagement pieces  64  becoming unbalanced. 
     Note that in the configuration in  FIG. 6 , the positional relationship between the engagement piece  64  and the drainage path  67  in the circumferential direction is not limited. Specifically,  FIG. 6  illustrates a typical example in which the distance between the engagement piece  64  and the drainage path  67  in the circumferential direction is one-fourth of the circumference of the circle defining said circumferential direction. However, the present disclosure is not limited to such a typical example. For example, the distance between the engagement piece  64  and the drainage path  67  in the circumferential direction may be one-eighth to one-third of the circumference of the circle defining said circumferential direction. 
     Furthermore, in the configuration in  FIG. 6 , the distal end portion of the drainage path  67  in the axial direction may be closed, as illustrated in  FIG. 4 or 5 . 
     Combining the configurations in  FIG. 3 to 5  and the configuration in  FIG. 6  results in a configuration in which the drainage path  67  is provided in two places, specifically, a position corresponding to the engagement piece  64  and a position different from the position of the engagement piece  64  in the circumferential direction. With such a configuration, the degree of flexibility for attaching the retainer unit  6  improves. Specifically, attaching the retainer unit  6  to the vehicle body V 1  in such a manner that one of the drainage path  67  provided at the position corresponding to the engagement piece  64  and the drainage path  67  provided at a position different from the position of the engagement piece  64  is on the lower side can result in a high level of drainage. 
     In the above-described embodiment, etc., at the distal end relative to the bottom wall part  612  in the axial direction, the engagement piece  64  extends from the cylindrical part  631  toward the proximal end in the axial direction. In other words, a fixed end of the engagement piece  64  that is a portion joined to the microphone facing part  63  is provided at the distal end (i.e., forward) relative to the bottom wall part  612  in the axial direction. However, the present disclosure is not limited to such an embodiment. Specifically, for example, the fixed end of the engagement piece  64  may be located at the proximal end (i.e., backward) relative to the bottom wall part  612  in the axial direction. 
     The drainage path  67  may be formed so that the width of the drainage path  67  in the microphone facing part  63  is greater than the width of the drainage path  67  in the engagement piece  64 . Alternatively, the drainage path  67  may be formed so as to have the greatest width in the opening  68 . Such a configuration allows very good drainage through the gap formed at the portion where the ultrasonic sensor  1  is attached to the front grille V 3 . 
       FIGS. 7 and 8  illustrate examples in which the drainage path  67  is formed to have a greater width at the distal end than at the proximal end in the axial direction. Note that the configurations illustrated in  FIGS. 7 and 8  and the configurations illustrated in  FIGS. 3 to 6  are different in detail. However, these are not substantially different in the function of the retainer unit  6 . Therefore, portions in these configurations that are construed as substantially the same structural elements as a result of having the same or equivalent function or structure are assigned the same reference signs. Hereinafter, the configuration according to the present modification will be described mainly with reference to  FIGS. 7 and 8 . 
     In the present modification, the microphone facing part  63  includes the cylindrical part  631  and the flange locking part  66 , as in the configurations illustrated in  FIGS. 3 to 6 . The cylindrical part  631  is a substantially circular cylindrical portion extending along the axis. The flange locking part  66  protrudes inward in the radial direction from a distal end portion of the cylindrical part  631  in the axial direction. The flange locking part  66  is configured to lock onto the cushion member  5  by coming into close contact with the cushion member  5 . 
     In the present variation, the drainage path  67  is provided to the cylindrical part  631  and the flange locking part  66 , as in the configuration illustrated in  FIG. 3 . Furthermore, with the opening  68  at the distal end in the axial direction, the drainage path  67  is provided so as to cut the flange locking part  66  in a circumferential direction. 
     Meanwhile, in the present variation, the drainage path  67  is formed so that the width of the drainage path  67  on the flange locking part  66  side is greater than the width of the drainage path  67  on the cylindrical part  631  side. Specifically, the drainage path  67  has the greatest width at the flange locking part  66 . Specifically, as illustrated in  FIG. 8 , the drainage path  67  in the flange locking part  66  is formed to have such a width that a center angle θ is between 20 degrees and 90 degrees, inclusive, in a plan view. On other hand, the drainage path  67  at a fixed end portion of the engagement piece  64  has the least width and is constant in width in a side view. The drainage path  67  in the cylindrical part  631  has the aforementioned greatest width at the distal end in the axial direction. Furthermore, the drainage path  67  in the cylindrical part  631  has the aforementioned least width at a portion where the drainage path  67  in the cylindrical part  631  is connected to the drainage path  67  in the engagement piece  64 . Furthermore, the drainage path  67  in the cylindrical part  631  is formed so as to expand in width stepwise from the aforementioned least width toward the greatest width. 
     In such a configuration, the flange locking part  66  is provided having a predetermined width in the circumferential direction to lock onto the cushion member  5  in the horizontal direction in the installed state. Thus, with the flange locking part  66 , the cushion member  5  can be reliably retained in the horizontal direction. 
     Meanwhile, the drainage path  67  is provided so as to open downward with a relatively large width in the installed-in-vehicle state. Therefore, in the installed-in-vehicle state, regardless of the shape of the front grille V 3 , clearance through which water that has reached the gap between the retainer unit  6  and the cushion member  5  can be discharged downward is optimally formed between the front grille V 3  and the retainer unit  6 . Thus, water that has reached the gap formed between the distal end portion of the flange locking part  66  in the axial direction, the rear surface of the front grille V 3 , and the outer peripheral surface of the exposed part  53  of the cushion member  5  face one another is favorably discharged into the space below the ultrasonic sensor  1  through the drainage path  67 . 
     Furthermore, in the present modification, the drainage path  67  is provided as a pair with the central axis line CL therebetween. Specifically, the pair of drainage paths  67  is vertically symmetrical with respect to the central axis line CL in the installed-in-vehicle state. With such a configuration, the degree of flexibility for attaching the retainer unit  6  improves. Specifically, attaching the retainer unit  6  to the vehicle body V 1  in such a manner that one of the pair of drainage paths  67  is on the lower side can result in a high level of drainage. 
     Unlike the configurations illustrated in  FIGS. 3 to 6 , in the present modification, the flange locking part  66  includes the drainage paths  67  at both the upper end and the lower end in the installed-in-vehicle state. In other words, in the microphone facing part  63 , a pair of flange locking parts  66  separated by the pair of vertically arranged drainage paths  67  are horizontally arranged. With such a configuration, the flange locking part  66  locks onto the cushion member  5  more evenly in the circumferential direction. This allows optimal reduction in problems of the cushion member  5  deforming at the position of the drainage path  67  and separating from the outer peripheral surface of the ultrasonic microphone  3 . 
     Furthermore, in the present modification, the drainage path  67  is provided in each of the pair of the vertically arranged engagement pieces  64 . Such a configuration allows optimal reduction in the occurrence of the engagement force between the pair of engagement pieces  64  becoming unbalanced as a result of providing the drainage path  67  only in the engagement piece  64  located on the lower side. 
     Furthermore, in the present modification, a reinforcement rib  632  is provided to the cylindrical part  631 . The reinforcement rib  632  protrudes outward in the radial direction and extends from the bottom wall part  612  along the axis. In other words, the reinforcement rib  632  is integrally joined to both the bottom wall part  612  and the cylindrical part  631 . 
     With such a configuration, the reinforcement rib  632  reinforces the microphone facing part  63  and the flange locking part  66  in a favorable manner. Specifically, the microphone facing part  63  can be optimally suppressed from deforming in such a manner as to open outward with a pressing force applied from the inside of the microphone facing part  63  in the state where the retainer unit  6  is attached to an assembly of the sensor body  2  and the cushion member  5 . Therefore, even in the case where the drainage path  67  is formed to have a great width to increase the level of drainage, the cushion member  5  can be retained well. Alternatively, even in the case where a pair of upper and lower drainage paths  67  is formed, the cushion member  5  can be retained well. 
     Note that the number of reinforcement ribs  632  to be installed is not limited. Specifically, in the example illustrated in  FIGS. 7 and 8 , two reinforcement ribs  632  are provided to each of the pair of left and right flange locking parts  66 . However, the present disclosure is not limited to such an embodiment. 
     Furthermore, as illustrated in  FIG. 9 , the reinforcement rib  632  may have a through-hole  633 . The through-hole  633  is provided at a base portion of the reinforcement rib  632  in such a manner as to penetrate, in the thickness direction, the plate-shaped reinforcement rib  632  having a thickness along the circumferential direction. The base portion of the reinforcement rib  632  is a proximal end portion of the reinforcement rib  632 , which extends along the axis, in the axial direction and is a portion where the reinforcement rib  632  is joined to the bottom wall part  612 . This optimally reduces the occurrence of water staying at the base portion of the reinforcement rib  632 . 
     Two or more seamlessly and integrally formed structural elements in the above description may be formed by bonding separate members to each other. Likewise, two or more structural elements formed by bonding separate members to each other in the above description may be seamlessly and integrally formed. 
     Two or more structural elements formed from the same material in the above description may be formed from different materials. Likewise, two or more structural elements formed from different materials in the above description may be formed from the same material. 
     It goes without saying that the elements included in the above-described embodiment are not necessarily indispensable unless otherwise indicated in particular or considered obviously indispensable in principle, for example. Furthermore, when the numerical figures, such as the number, numerical values, amount, range, etc., of structural elements are mentioned, the present disclosure is not limited to these specific numerical figures unless indicated as required in particular or obviously limited in principle to a specific figure, for example. Likewise, when the shape, direction, positional relationship, etc., of the structural elements and the like are mentioned, the present disclosure is not limited to these shape, direction, positional relationship, etc., unless indicated as required in particular or limited in principle to a specific shape, direction, positional relationship, etc., for example. 
     The modification is not limited to the above-described example. Furthermore, two or more modifications can be combined together. Moreover, the entirety or a portion of the above-described embodiment and the entirety or a portion of the modification can be combined together. 
     Hereinafter, aspects of the above-described embodiments will be summarized. 
     An ultrasonic sensor ( 1 ) is configured to be attached to an auto body component (V 3 ). 
     According to one aspect of the present disclosure, this ultrasonic sensor includes: 
     a sensor body ( 2 ) including an ultrasonic microphone ( 3 ) having a columnar shape and extending along an axial direction parallel to a central axis line (CL) and a microphone support unit ( 4 ) which allows a protruding part ( 31 ) of the ultrasonic microphone to protrude and supports a supported part ( 32 ) of the ultrasonic microphone, the protruding part being located at a distal end in the axial direction, the supported part being located at a proximal end in the axial direction; 
     a cushion member ( 5 ) provided to cover the protruding part of the ultrasonic microphone and formed in a cylindrical shape from a synthetic resin-based elastic material; 
     a retainer unit ( 6 ) provided outward of the ultrasonic microphone in a radial direction extending from the central axis line, the retainer unit being configured so that an exposed part ( 53 ) of the cushion member is exposed and a sandwiched part ( 54 ) of the cushion member is sandwiched between the retainer unit and an outer peripheral surface ( 30 ) of the protruding part of the ultrasonic microphone, the exposed part being located at the distal end in the axial direction, the sandwiched part being located at the proximal end in the axial direction; and 
     a drainage path ( 67 ) penetrating the retainer unit in the radial direction to allow water to be discharged out of the retainer unit from a gap between the retainer unit and the cushion member. 
     A retainer ( 6 ) corresponds to the retainer unit. In other words, the retainer is a component for attaching and fixing, to an auto body component (V 3 ), an ultrasonic sensor ( 1 ) including a sensor body ( 2 ) in which an ultrasonic microphone ( 3 ) having a columnar shape and extending in an axial direction parallel to a central axis line (CL) protrudes toward a distal end thereof in the axial direction. 
     According to one aspect of the present disclosure, this retainer includes: 
     a microphone facing part ( 63 ) corresponding to the ultrasonic microphone and formed in a cylindrical shape extending along the axis toward the distal end in the axial direction; 
     an engagement piece ( 64 ) which is a plate-shaped part extending along the central axis line from the microphone facing part toward a proximal end in the axial direction, the engagement piece including an engagement part ( 65 ) which engages the sensor body; and 
     a drainage path ( 67 ) provided in one of the microphone facing part or the engagement piece and penetrating the one of the microphone facing part and the engagement piece in a radial direction to allow water to be discharged out of the retainer. 
     In the ultrasonic sensor, the gap can be formed between the retainer unit and the cushion member. A state where the ultrasonic sensor is attached to the auto body component is referred to as being installed-in-vehicle state. In the installed-in-vehicle state, if incoming water is retained in the gap, the propagation of vibration through the retained water may cause an increase in unnecessary reflected waves, causing trouble such as false detection. 
     In this regard, in the ultrasonic sensor configured as described above, the retainer unit includes the drainage path. The drainage path penetrates the retainer unit in the radial direction to allow water to be discharged out of the retainer unit from the gap. Therefore, incoming water can be maximally suppressed from being retained in the gap. Therefore, with this configuration, degradation in the performance of the in-vehicle ultrasonic sensor that is caused by infiltration of water due to rain or the like can be sufficiently suppressed.