Abstract:
A foldable mirror device for a vehicle, in which a case is mounted on a support shaft erected from a base. The case includes a ring-shaped support portion for supporting the shaft, a motor connected to a transmission for swinging the mirror, and a clutch portion for disengageably engaging with the base. The support portion can be strengthened by ribs between the support portion and other portions of the case. A worm gear of the transmission can be mounted on a motor output shaft to be freely movable therealong, and supported and constrained by supporting a bottom end of the worm gear on the case and accommodating an upper end of the worm gear in a cylindrical projection from a motor base which supports the motor. End portions of convexities and concavities at the engagement portion can be formed in a concave or convex screw shape.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a mirror device for a vehicle.  
         [0003]     2. Description of the Related Art  
         [0000]     Prior Art 1  
         [0004]     In a mirror device for a vehicle, such as an electrically powered housable-type door mirror device, a mirror stay is fixed to a side of the vehicle body so as to extend in a substantially transverse direction from the vehicle, and a mirror main body portion is supported by the mirror stay such that the mirror main body can swing between a housed position and a position for viewing. This type of conventional door mirror device  100  is illustrated in FIGS.  18  to  21  and a brief description thereof follows.  
         [0005]     As illustrated in  FIG. 18 , a stand  104  whose axial direction is a substantially vertical direction of the vehicle, is fixed on a mirror stay  102  which is fixed at a side of the vehicle. An electrically powered housing unit  106  is provided on the rotation shaft  104 A of the stand  104 , so as to be rotatable about the axis of the shaft. A mirror main body portion  110  comprising a mirror  108  and the like is connected to and supported by the electrically powered housing unit  106 .  
         [0006]     When a driving motor inside the electrically powered housing unit  106  operates, it works to rotate a gear plate  112  (See  FIG. 20 ), which is axially supported by the rotation shaft  104 A, via a gear mechanism. However, the gear plate  112  is always held so that it does not rotate with respect to the rotation shaft  104 A. Thus, the electrically powered housing unit  106  itself rotates around the rotation shaft  104 A. Since the mirror main body  110  is connected to and supported by the electrically powered housing unit  106 , the mirror main body  110  rotates, along with the electrically powered housing unit  106 , between the housed position and the position for viewing.  
         [0007]     The schematic structure of a case  114 , which forms the exterior of the electrically powered housing unit  106 , will be described with reference to  FIGS. 19 and 20 .  
         [0008]      FIG. 19  shows a schematic plan view of the case  114 , which forms the exterior of the electrically powered housing unit  106  in the door mirror device  100 .  FIG. 20  shows a longitudinal section view of the case  114 . A cylindrical support shaft portion  116  is erected at the left side, in the drawing, of the top surface of the case  114 , and a circular concave portion  118  is formed around the support shaft portion  116 . The rotation shaft  104 A of the stand  104  is inserted inside the support shaft portion  116 , and the case  114  is axially supported by the rotation shaft  104  so as to be rotatable. In addition, the gear plate  112 , which applies anti-drive force to the electrically powered housing unit  106  and the mirror main body  110 , is held so as to be fixed at the top end side of the support shaft portion  116 .  
         [0009]     In the electrically powered housing unit  106  having the above-described structure, the load of the electrically powered housing unit  106  and the mirror main body  110  must be supported by the support shaft portion  116  of the case  114 . However, the strength of the support shaft portion  116  of the case  114  may be insufficient. Thus, external forces such as vehicle vibrations act on the door mirror device  100  and, as indicated by the arrow in  FIG. 21 , the mirror main body  110  vibrates in a substantially longitudinal direction of the vehicle, about a center in the vicinity of the support shaft portion  116  (the vicinity of the base of the stand  104 ). In order to limit this type of vibration, increasing the rigidity of the support shaft portion  116  has been considered. In order to do this, the plate thickness of the case  116  and/or the bottom portion  114 A of the case  114  can be increased, thereby reinforcing the case  114 . However, if this is done, there is the possibility that problems will be caused such as the generation of shrinkage and warping on a surface of the mirror. Also, it may be necessary to increase the number of cycles in the production process, leading to increased production costs.  
         [0000]     Prior Art 2  
         [0010]     Door mirror devices are usually equipped with a housing mechanism, and the housing mechanism includes a stand which is fixed to the vehicle side. The stand is provided so as to be integral with a support shaft.  
         [0011]     The housing mechanism is equipped with a case member, and the case member is supported by the support shaft so as to be rotatable. The case member is connected to a mirror for viewing the rear of the vehicle and the case member always swings together with the mirror.  
         [0012]     A motor base is fixed to an inner portion of the case member and a motor is fixed to the upper side of the motor base by screws. A motor output shaft passes through the motor base, and a worm gear is press-inserted onto the motor output shaft through the lower side of the motor base. As a result, the worm gear is swung by the motor being driven.  
         [0013]     A helical gear meshes with the worm gear and the helical gear is rotated by the rotation of the worm gear. Thus, a rotational force is applied to the support shaft and the case member is rotated by anti-rotational force. The mirror can thus be housed or swung out for viewing.  
         [0014]     However, with this type of door mirror device, the worm gear is press-inserted onto the motor output shaft, and is not movable in an axial direction with respect to the motor output shaft. As a result, there is a problem that the motor output shaft receives a sliding force from the worm gear, and this reduces the life span of the motor.  
         [0015]     In order to solve this problem, door mirror devices are provided in which the motor output shaft and the worm gear are separate, and the worm gear is not rotatable with respect to the motor output shaft, but is movable in the axial direction thereof.  
         [0016]     However, in this type of device, there is a tendency for the worm gear to displace in a perpendicular direction with respect to the motor output shaft. As a result, the sound of the operation between the worm gear and the helical gear becomes very loud and in some cases the worm gear may skid.  
         [0000]     Prior Art 3  
         [0017]     Further, in the door mirror device described above, the stand has a pair of stand concavities which are provided on a circle having the support shaft at the center thereof. The respective end portions of the stand concavities project upwards and face each other.  
         [0018]     A gear plate is rotatably disposed around the support shaft which rotatably supports the case member, and a rotational force is applied to the gear plate by the motor being driven. The upper surface of the gear plate is provided with insertion convexities, which project upwards.  
         [0019]     A clutch plate is disposed around the support shaft above the gear plate, and the clutch plate is not rotatable with respect to the support shaft. Insertion concavities are provided at a lower surface of the clutch plate, and end portions of the insertion concavities project downwards. The insertion convexities of the gear plate are inserted into these insertion concavities and as a result, the clutch plate meshes with the gear plate.  
         [0020]     A compression coil spring is penetrated by the support shaft above the clutch plate, and push nuts are fixed on top of the compression coil spring. The compression coil spring is anchored by the push nuts, and the compression coil spring urges the clutch plate.  
         [0021]     A pair of case convexities, formed on a circle having the support shaft at the center thereof, are provided at a lower portion of the case member. Each of the case convexities projects downwards, and they face each other.  
         [0022]     When a rotational force is applied to the gear plate by the motor being driven, the clutch plate blocks the rotation of the gear plate. As a result, the case member is rotated by anti-rotational force exerted at the gear plate, and the mirror swings in a housing direction or in a viewing direction. Also, when the end portions of the case convexities engage with the end portions of the stand concavities, the case member is anchored, and the mirror can be stopped at the housed position or at the position for viewing.  
         [0023]     On the other hand, if an external force exceeding a predetermined value acts on the case member, the urging force of the compression coil spring is resisted and the insertion convexities are disengaged from the insertion concavities. By the gear plate and the case member swinging with respect to the clutch plate, impact of the force can be ameliorated and damage to the gear plate is prevented.  
         [0024]     However, in this type of door mirror device, end portions of all of the case convexities, the stand concavities, the insertion convexities and the insertion concavities are inclined surfaces having an upper area and lower area which are co-planar with each other. As a result, when the end portions of the case convexities engage with the end portion of the stand concavities, if the case convexities and the stand concavities undulate, they are connected linearly. Also, when the insertion convexities are inserted into the insertion concavities, or when insertion convexities and insertion concavities are disengaged, if the end portion of the insertion convexities and the end portion of the insertion concavities undulate, the insertion convexities and the insertion concavities are connected linearly. As a result, the case convexities, the stand concavities, the insertion convexities and the insertion concavities become worn and the durability of the mirror device is poor.  
         [0025]     Since two sets of the case convexities and stand concavities are arranged on the same circle, whose center is the support shaft, when the end portions of the case convexities are engaged with the end portions of the stand concavities, the pressure which both the case convexities and the stand concavities receive is large and thus durability is poor. Also, when the end portions of the case convexities are engaged with the end portions of the stand concavities, the case member may rattle on the stand and as a result the mirror also tends to rattle.  
       SUMMARY OF THE INVENTION  
       [0026]     An object of the present invention is to provide a door mirror device in which vibration generated at a mirror main body portion can be effectively controlled without increasing plate thickness of a support shaft portion.  
         [0027]     Another object of the present invention is to provide a mirror device for a vehicle in which the life span of a motor is extended and slipping of a worm gear in a perpendicular direction of a shaft is controlled.  
         [0028]     Yet another object of the invention is to provide a mirror device for a vehicle, in which durability of case convexities and stand concavities is improved.  
         [0029]     According to one aspect of the present invention, there is provided a folding-type mirror device for a vehicle, the mirror device including: a support shaft including a base portion; a case installed on the support shaft, the case including a support portion disposed around an outer periphery of the base portion of the support shaft, a bottom portion from which the support portion projects, and at least one reinforcing rib integrally connecting an outer surface of the support portion with the bottom portion; and a mirror unit attached to the case and swingable around the support shaft, by rotation of the support portion around the support shaft, for positioning at positions including a viewing position and a folded position.  
         [0030]     According to another aspect of the invention, there is provided an electrically powered folding mirror device for a vehicle, the mirror device including: a support shaft including a base portion; a case installed on the support shaft, the case including a fitting portion disposed around an outer periphery of the base portion of the support shaft; a mirror unit attached to the case and swingable around the support shaft, by rotation of the fitting portion around the support shaft, for positioning at positions including a viewing position and a folded position; a motor base attached inside the case; an electric motor mounted to the motor base and including a motor output shaft which penetrates the motor base; and a transmission mechanism provided inside the case, operationally connected to the motor output shaft, and including a worm gear connected with the motor output shaft so as to be moveable in an axial direction of the motor output shaft but not rotatable relative to the motor output shaft, the transmission mechanism acting to swing the case and mirror unit when the motor is operated.  
         [0031]     According to still another aspect of the invention, there is provided a folding mirror device for a vehicle, the mirror device including: a stand; a support shaft extending from the stand and including a base portion; a case installed on the support shaft, the case including a fitting portion disposed around an outer periphery of the base portion of the support shaft; a mirror unit attached to the case, and swingable around the support shaft, by rotation of the fitting portion around the support shaft, for positioning at positions including a viewing position and a folded position; and a positioning mechanism at an interface of the stand and the case, the positioning mechanism including a plurality of convexities formed at the case and a plurality of concavities formed at the stand, the convexities being insertable into the concavities, and each convexity and each concavity including one end portion and another end portion,  
         [0032]     wherein the one end portions of the convexities are surface-contactingly engageable with the one end portions of the concavities for holding the case and the mirror unit at one of the viewing position and the folded position, and the another end portions of the convexities are surface-contactingly engageable with the another end portions of the concavities for holding the case and the mirror unit at the other of the viewing position and the folded position.  
         [0033]     According to still another aspect of the invention, there is provided a folding mirror device for a vehicle, the mirror device including: a stand which is mountable to a vehicle body; a support shaft projecting from the stand and including a base portion; a case installed on the support shaft, the case including a fitting portion disposed around an outer periphery of the base portion of the support shaft; a mirror unit attached to the case, and swingable around the support shaft, by rotation of the fitting portion around the support shaft, for positioning at positions including a viewing position and a folded position; an electric motor disposed in the case and including a motor output shaft; and a transmission mechanism provided inside the case and operationally connected to the motor output shaft for acting to swing the mirror and case unit when the motor is operated, the transmission mechanism including a gear plate rotatably mounted to the support shaft and including a clutch plate fixed to the support shaft, the clutch plate being capable of blocking relative rotation of the support shaft and the gear plate and capable of allowing relative rotation of the support shaft and the gear plate, wherein one of the gear plate and the clutch plate includes insertion convexities and the other includes insertion concavities into which the insertion convexities are surface-contactingly fittable for the blocking of relative rotation.  
         [0034]     The foregoing and other objects, features and advantages of the present invention will be apparent from the following description of preferred embodiments of the invention, as illustrated in the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0035]      FIG. 1  is a longitudinal sectional view taken along line  1 - 1  of  FIG. 4 , of an electrically powered housing unit of an electrically powered housable-type door mirror device according to a first embodiment of the present invention.  
         [0036]      FIG. 2  is a cross sectional view taken along line  2 - 2  of  FIG. 3 , of the electrically powered housing unit according to the first embodiment of the present invention.  
         [0037]      FIG. 3  is a front view of the electrically powered housing unit according to the first embodiment of the present invention.  
         [0038]      FIG. 4  is a plan view of the electrically powered housing unit according to the first embodiment of the present invention.  
         [0039]      FIG. 5  is a front view outlining overall structure of the door mirror device according to the first embodiment of the present invention.  
         [0040]      FIG. 6  is a front sectional view of a housing mechanism of a door mirror device according to a second embodiment of the present invention.  
         [0041]      FIG. 7  is a front view of the housing mechanism according to the second embodiment of the present invention.  
         [0042]      FIG. 8  is a plan view taken along line  8 - 8  of  FIG. 6 , of the housing mechanism according to the second embodiment of the present invention.  
         [0043]      FIG. 9  is a sectional plan view taken along line  9 - 9  of  FIG. 6 , of the housing mechanism of the door mirror device according to the second embodiment of the present invention.  
         [0044]      FIG. 10  is a plan view of a stand of a door mirror device according to a third embodiment of the present invention.  
         [0045]      FIG. 11  is a perspective view of an end portion of a stand concavity of the door mirror device according to the third embodiment of the present invention.  
         [0046]      FIG. 12  is a front view of the housing mechanism according to the third embodiment of the present invention.  
         [0047]      FIG. 13  is a front sectional view of the housing mechanism according to the third embodiment of the present invention.  
         [0048]      FIG. 14  is a side sectional view taken along line  14 - 14  of  FIG. 12 , of the housing mechanism according to the third embodiment of the present invention.  
         [0049]      FIG. 15  is a plan sectional view of taken along line  15 - 15  of  FIG. 12 , of the housing mechanism according to the third embodiment of the present invention.  
         [0050]      FIG. 16  is a plan view of a gear plate according to the third embodiment of the present invention.  
         [0051]      FIG. 17  is a back view of a cam plate according to the third embodiment of the present invention.  
         [0052]      FIG. 18  is a front view outlining overall structure of an electrically powered housable-type door mirror of the prior art.  
         [0053]      FIG. 19  is a cross sectional view corresponding to  FIG. 2 , of a case to be assembled to an electrically powered housing unit of the prior art.  
         [0054]      FIG. 20  is a cross sectional view taken along line  20 - 20  of the case and the like of  FIG. 19 .  
         [0055]      FIG. 21  is a schematic side view for describing problems of a door mirror device of the prior art. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     First Embodiment  
       [0056]     An electrically powered housable-type door mirror device  10  according to a first embodiment of the present invention will be described with reference to FIGS.  1  to  5 .  
         [0057]      FIG. 5  outlines the electrically powered housable-type door mirror device  10  according to this first embodiment in an assembled state. The door mirror device  10  is fixed at a predetermined position to a side of a vehicle body. The door mirror device  10  is comprised of a door stay  12  which is a “door mirror base portion” and extends in a substantially lateral direction of the vehicle, an electrically powered housing unit  14  which swings between a housed position and a position for viewing and is axially supported by a rotation shaft  52 B (described hereinafter), which rotation shaft  52 B is erected from an extending portion  12 A of the stay  12 , and a mirror main body portion  16  which swings integrally with the electrically powered housing unit  14 .  
         [0058]     The mirror main body  16  includes: a frame  18  which has a substantially tabular rectangle shape and is formed of a vertically disposed seat surface for mounting; a visor rim  20  which is disposed at a rear surface side of the frame  18  and is fixed to the frame  18  by screws or the like; a visor cover  22  which is disposed at a front surface side of frame  18  and is fixed to frame  18  covered with the visor rim  20  with engaging claws or the like; and a mirror  24  which is disposed at a rear portion of the visor rim  20  and held to the frame  18  such that the angle of a mirror surface is adjustable.  
         [0059]     In addition, the electrically powered housing unit  14  is fixed to the frame  18 . This can also be regarded as mirror main body  16  being connected to the electrically powered housing unit  14  via the frame  18 , thus forming one unit. Also, by the electrically powered housing unit  14  being axially supported by the rotation shaft  52 B of a stand  52  which is described hereinafter, when the electrically powered housing unit  14  swings around the rotation shaft  52 B, the mirror main body  16  swings along with the electrically powered housing unit  14 .  
         [0060]     Reference will be made to FIGS.  1  to  4  in the following description.  
         [0061]     The electrically powered housing unit  14  includes: a case  26  which forms the exterior at a lower portion of the unit and whose upper end is open; a gear cover  28  which forms the exterior at an upper portion of the unit, and whose lower end is open; a motor base  30  which is disposed between the case  26  and the gear cover  28  and horizontally divides the space in the unit. Due to strength requirements, the thicknesses of the members are such that the case  26  is the thickest and the gear cover  28  is the thinnest. In addition, the gear cover  28  covering the case  26  is removably attached by a claw fitting.  
         [0062]     The frame  18 , which is vertically disposed inside the mirror main body portion  16 , is fixed at three points on the case  26 . Two (upper and lower) points are on an outer side of the case  26 , and one point is at the lower end of an inner side of the case  26 . (A first attachment point  32  is set on the outer side of the case  26  so as to be apart from a drive motor  38  (described later), and a second attachment point  34  and third attachment point  36  are set within a transverse direction dimension of the case  26 .)  
         [0063]     The driving motor  38 , which is a drive source, is disposed at a side portion of the outer side of the motor base  30 . A worm gear  42  is fixed co-axially to an output shaft  40  of the driving motor  38 , and a helical gear  44  meshes with the worm gear  42 . The helical gear  44  is fixed to a worm gear shaft  46  and a worm gear  48  is fixed co-axially to the worm gear shaft  46 .  
         [0064]     A portion towards the inner side of a bottom wall portion  26 A of the case  26  is formed integrally with a cylindrical support shaft portion  50 . The stand  52  is inserted from the lower side into the support shaft portion  50 . The stand  52  is formed of a disc-shaped base portion  52 A and the cylindrical rotation shaft  52 B, which is erected from an axial center of the base portion  52 A. The outer diameter of the base portion  52 A is larger than the outer diameter of the support shaft portion  50  of the case  26 , and is disposed in a state of projecting from a lower surface side of the bottom wall portion  26 A of the case  26 . The electrically powered housing unit  14  is assembled by the base portion  52 A being fixed to an extending portion  12 A of the mirror stay  12 . The mirror stay  12  holds the rotation shaft  52 B such that the axial direction thereof is substantially in a vertical direction of the vehicle.  
         [0065]     An upper end portion of the motor base  30  is anchored to a distal end portion of the rotation shaft  52 B of the stand  52 , and an upper end portion of the gear cover  28  is anchored to the upper end portion of the motor base  30 . Simply stated, the upper end portion of the rotation shaft  52 B of the stand  52 , the upper end portion of the motor base  30 , and the upper end portion of the gear cover  28 , form an anchoring structure.  
         [0066]     Further, an axial direction middle portion of the rotation shaft  52 B of the stand  52  is cut away at two positions opposing each other in the radial direction thereof, and thus the axial direction middle portion of the rotation shaft  52 B is formed in a substantially oval shape (athletics track shape) in plan view. Note that this cut-away portion will be referred to as “cutaway portion  54 ” hereinafter.  
         [0067]     A substantially disc-shaped gear plate  56  is disposed, so as to be rotatable, around the rotation shaft  52 B of the stand  52 . The aforementioned worm gear  48  meshes with an outer peripheral portion of the gear plate  56 , and driving force of the driving motor  38  is transmitted thereby. Further, engagement portions whose cross sections have a trapezoid shape or the like, are formed so as to be connected in a peripheral direction on an upper surface of the gear plate  56 . A clutch plate  58  formed in a substantial disc shape is disposed on the upper surface of the gear plate  56 . Cover engagement portions whose sections have a trapezoid shape or the like and which can engage with the engagement portions of the gear plate  56  are consecutively formed in the peripheral direction on a lower surface of the clutch plate  58 , and these cover engagement portions mesh by concave and convex portions fitting together.  
         [0068]     In addition, substantially ring-shaped push nuts  60  are fixed at a vicinity of the upper end portion of the rotation shaft  52 B of the stand  52 , and a compression coil spring  62 , which can more broadly be thought of as an urging means, is wound between these push nuts  60  and the upper surface of the clutch plate  58 . Thus, the compression coil spring  62  always urges the clutch plate  58  toward the gear plate  56 .  
         [0069]     Further, a shaft insertion hole  64  which has a substantially oval shape (athletics track shape) and which matches the tabular sectional shape of the rotation shaft  52 B is formed at an axial center portion of the clutch plate  58 . The cutaway portion  54  of the rotation shaft  52 B corresponds to the shaft insertion hole  64 , and as a result, the clutch plate  58  cannot rotate with respect to the rotation shaft  52 B.  
         [0070]     Slip washers  66  are disposed between a lower surface of the gear plate  56  and an upper end portion of the support shaft portion  50  of the case  26 , and also between the lower end portion of the support shaft portion  50  and the upper surface of the base portion  52 A of the stand  52 . These slip washers  66  reduce frictional resistance when the electrically powered housing unit swings.  
         [0071]     As illustrated in  FIGS. 1 and 2 , ring-form concave portions  68 , which are “wall portions” are formed at the outer periphery side of the cylindrical support shaft portion  50  which is formed in the case  26 . An outer peripheral surface  50 A of the support shaft portion  50  and an inner peripheral surface  68 A of the concave portions  68  are disposed so as to face each other. A plurality of ribs  70  are formed radially from the outer peripheral surface  50 A of the support shaft portion  50 . Inner ends of these ribs  70  are connected with the outer peripheral surface  50 A of the support shaft portion  50 , outer ends are connected to the inner peripheral surface  68 A of the concave portions  68 , and lower ends are connected to a bottom surface  68 B of the concave portions  68 .  
         [0072]     Next, the operation and effects of the first embodiment will be described.  
         [0073]     First, movement of the door mirror device  10  at a time of housing will be outlined.  
         [0074]     When the driving motor  38  drives, the output shaft  40  rotates about its axis. As a result, the worm gear  42  which is fixed to the output shaft  40  rotates at the same rate, and causes the helical gear  44  to rotate a lower rate. When the helical gear  44  rotates, the worm gear shaft  46  to which the helical gear  44  is fixed rotates about the axis of the helical gear  44 . As a result, the worm gear  48  which is fixed to the worm gear shaft  46  rotates at the same speed. In this manner, the driving force of the driving motor  38  is transmitted to the gear plate  56  which meshes with the worm gear  48 . However, the clutch plate  58  is frictionally engaged with the gear plate  56  by the urging force of the compression coil spring  62 . As a result, the clutch plate  58  blocks the rotation of the gear plate  56 , and thus an anti-drive force which acts on the gear plate  56  acts on the electrically powered housing unit  14 . The entire electrically powered housing unit  14  swings via the case  26  about the rotational axis  52 B of the stand  52  causing the mirror main body portion  16  to be housed.  
         [0075]     If the mirror main portion  16  receives an external force such that an external force exceeding a predetermined value acts on the case  26 , the gear plate  56  and the clutch plate  58  which were frictionally engaged become disengaged, and rotation of the gear plate  56  with respect to the clutch plate  58  is allowed. Thus, the gear plate  56  rotates along with the case  26 , which prevents the gear plate  56  from being damaged.  
         [0076]     The cylindrical support shaft portion  50  which is supported with the rotation shaft  52 B of the stand  52  is formed in the case  26  which forms the exterior of the electrically powered housing unit  14 . The load of the electrically powered housing unit  14  and the mirror main body  16  is exerted on the support shaft portion  50 . However, in the present embodiment of the present invention, since the reinforcement ribs  70  are provided radially on the outer periphery of the support shaft portion  50 , the rigidity of the support shaft portion  50  can be sufficiently enhanced without increasing the plate thickness of the support shaft portion  50  or the like. Correspondingly, according to the present embodiment, vibration of the mirror main body  16  in a substantially longitudinal direction of the vehicle, around a center at the vicinity of the support shaft portion  50  is efficiently restrained and further, can be prevented. Also, according to the present embodiment, since it is not necessary to increase the thickness of the support shaft portion  50  and the bottom portions of the concave portions  68  of the case  26  and the like, problems such as shrinkage and warping on the surface of the case  26  and the necessity of increasing the number of steps in the production of case  26  are not caused.  
         [0077]     In addition, according to the present embodiment, since the ribs  70  are formed radially from the cylindrical support shaft portion  50 , the ribs  70  can be uniformly, or substantially uniformly, reinforced. As a result, a merit of the present embodiment is that stress concentration caused by unevenness in the reinforcement is unlikely.  
         [0078]     In the present embodiment, the ribs  70  extend from the outer peripheral surface  50 A of the support shaft portion  50  outward in the radial direction and are connected to the bottom surface  68 B of the concave portions  68 . Since the outer peripheral surface  50 A of the support shaft portion  50  and the inner peripheral surface  68 A of the concave portions  68  are provided so as to be connected, the rigidity of the support shaft portion  50  is effectively enhanced. As a result, the load which acts on the support shaft portion  50  is smoothly transmitted to the bottom wall portion  26 A of the case  26 , via the ribs  70 . In other words, the load is supported by the entire case  26 .  
         [0079]     In addition, according to the present embodiment, since the ribs  70  are plurally provided on the periphery of the support shaft portion  50  of the case  26  and the rigidity of the periphery of the support shaft portion  50  is enhanced, it is possible for the third attachment point  36  for fixing the case  26  to the frame  18  to be set within the width direction dimension of the case  26 . In other words, in the present embodiment, the third attachment point  36  is set in the vicinity of the support shaft portion  50 , and within a range that has been reinforced by the ribs  70 . Incidentally, in the case of the structure of the prior art, as shown in  FIGS. 18 and 20 , a third attachment point  120  is set at a position which extends in a radial direction beyond the inner side of the case  114 . Consequently, the width direction dimension of the case  26  in the present embodiment may be made shorter than in the prior art. Therefore, the electrically powered housing unit  14  can be made more compact in the width direction. Consequently, the electrically powered housing unit  14  can be used with a smaller mirror.  
         [0080]     Although the ribs  70  for reinforcement are formed radially on the periphery of the support shaft portion  50  in the present embodiment, the ribs are not necessarily provided radially. For example, the ribs may be provided in cross shapes around the support shaft portion, or just one pair of ribs may be provided.  
         [0081]     Also, in the present embodiment, the outer end portions of the reinforcing ribs  70  are connected to the inner peripheral surface  68 A of the concave portions  68 , but the outer end portions of the ribs do not necessarily have to be connected to the inner peripheral surface of the concave portions. Even in a case without such connection, a reinforcing effect can be expected to some extent.  
         [0082]     Further, the present invention may be applied to a manual housing-type door mirror (besides the electrically powered housable-type).  
       Second Embodiment  
       [0083]     A door mirror device  210  according to a second embodiment of the present invention will be described with reference to FIGS.  6  to  9 .  
         [0084]     The mirror device  210  includes a housing mechanism  212  and the housing mechanism  212  is provided with a stand  214 . The stand  214  is fixed to a stay (not shown), which is fixed to a vehicle door or the like. A cylindrical support shaft  216  is provided integrally with the stand  214  so as to be erect, and the support shaft  216  is fixed via the stand  214  to a side of the vehicle body. A gear plate  218  is disposed around the support shaft  216 , and rotation of the gear plate  218  with respect to the support shaft  216  is blocked.  
         [0085]     The housing mechanism  212  includes a case  220  and a cover  221  which covers an upper opening portion of the case  220 . The support shaft  216  is inserted through the case  220  and thus the case  220  is rotatably supported by the support shaft  216 . The case  220  is connected to a mirror (not shown) for viewing the rear direction of the vehicle via a frame and a mirror surface-adjusting mechanism, and the case  220  (and the cover  221 ) rotates integrally with the mirror.  
         [0086]     The case  220  is provided with a horizontal surface portion  222  at a side opposite to a vehicle side (at the side indicated by arrow A in  FIG. 6 ), at a substantially central portion in a vertical direction. A substantially cylinder-shaped fitting hole (fitting portion)  224  and a substantially cylinder-shaped blocking hole (blocking means)  226  are formed at the horizontal surface  222 , and the fitting hole  224  and the blocking hole  226  are in communication.  
         [0087]     A substantially plate-shaped motor base  228  is mounted so as to be fixed inside the case  220 . The motor base  228  is fixed at both end portions thereof in a longitudinal direction of the vehicle, with a predetermined number of screws  230  (2 in the present embodiment) to the horizontal surface portion  222  within the case  220 . A substantially cylindrical-shaped standing cylinder  232  is erected at a vehicle inner side upper surface of the motor base  228 , and the support shaft  216  is disposed inside the standing cylinder  232 .  
         [0088]     An elliptical cylinder-shaped fitting cylinder  234  is provided so as to be erect on a vehicle outer side upper surface of the motor base  228 , and a motor  236  is mounted onto the motor base  228  by the motor  236  being fitted into the fitting cylinder  234 . In addition, an output shaft  236 A of the motor  236  is inserted through the motor base  228  and disposed at a lower side of the motor base  228 .  
         [0089]     A substantially cylindrical, hollow control portion  238  is provided on the vehicle outer side lower surface of the motor base  228 . The output shaft  236 A of the motor  236  is inserted through the center of the inner portion of the control portion  238 . The outer periphery of the control portion  238  fits into the fitting hole  224 . A substantially cylindrical-shaped blocking projection (blocking means)  240  is also provided at the vehicle outer side lower surface of the motor base  228 . The blocking projection  240  is formed integrally with the control portion  238 . The blocking projection  240  fits into the blocking hole  226 , to block rotation of the motor base  228  with respect to the case  220 .  
         [0090]     A worm gear  242  is mounted to the output shaft  236 A of the motor  236 . A lower portion of the worm gear  242  is rotatably supported by a lower wall of the case  220 . By the worm gear  242  being simply inserted onto the output shaft  236 A of the motor  236 , the worm gear  42  is rendered unable to rotate relative to the output shaft  236 A of the motor  236 , but movable in an axial direction relative to output shaft  236 A of the motor  236 . In addition, the worm gear  242  substantially fits into the control portion  238  of the motor base  228  and can abut therein. Perpendicular direction movement of the worm gear  242  with respect to the output shaft  236 A of the motor  236  is thereby restrained.  
         [0091]     Similarly to the worm gear  242 , a helical gear  244  is supported by the inner portion of the case  220 , and the helical gear  244  meshes with the worm gear  242 . The helical gear  244  is integrally provided with a shaft worm gear  246 , and the shaft worm gear  246  meshes with the gear plate  218 .  
         [0092]     Thus, when the motor  236  is driven, rotational force is transmitted to the worm gear  242 , the helical gear  244  and the shaft worm gear  246 , and this rotational force is exerted on the gear plate  218  of the support shaft  216 . As a result, due to anti-rotational force, the shaft worm gear  24  swings around the gear plate  218  and causes the case  220  to swing, and the mirror thereby swings, to be housed or brought to a position for viewing.  
         [0093]     The following is a description of the effects of the second embodiment.  
         [0094]     When the motor  236  is driven, the worm gear  242 , the helical gear  244  and the shaft worm gear  246  are rotated, and thus the case  220  swings due to anti-rotational force which is exerted on the gear plate  218  of the support shaft  216 . As a result, the mirror swings together with the case  220  and is housed or swung to a position for viewing.  
         [0095]     Since the worm gear  242  is mounted such that it cannot rotate relative to the output shaft  236 A of the motor  236 , but can move in an axial direction relative to the output shaft  236 A of the motor  236 , the output shaft  236 A of the motor  236  does not experience translational force from the worm gear  242 . Thus, the life span of the motor  236  can be lengthened.  
         [0096]     Further, since the output shaft  236 A of the motor  236  does not receive sliding force from the worm gear  242 , the motor  236  can be mounted to the motor base  228  simply by fitting the motor  236  into the fitting cylinder  234  of the motor base  228 . Thus, screws for fixing the motor to the motor base as in the prior art are unnecessary, and, since the number of parts is decreased, ease of assembly is improved.  
         [0097]     Further, the control portion  238  which is integrally provided with the motor base  228  can abut the worm gear  242 , and thus movement of the worm gear  242  in a perpendicular direction with respect to the output shaft  236 A of the motor  236  is limited. As a result, slipping of the worm gear  242  in a direction perpendicular to the shaft is prevented. Also, operational noise of the worm gear  242  and the helical gear  244  can be reduced, and skidding of the worm gear  242  can be reduced.  
         [0098]     In addition, since the control portion  238  of the motor base  228  is fitted into the fitting hole  224  of the case  220 , the control portion  238  can be favorably positioned relative to the case  220 . As a result, positioning of the worm gear  242  in the control portion  238  is also favorable and control of slipping of the worm gear  242  in a perpendicular direction with respect to the shaft is ensured.  
         [0099]     Further, since the blocking projection  240  of the motor base  228  is fitted into the blocking hole  226  of the case  220 , rotation of the motor base  228  with respect to the case  220  is blocked. As a result, the control portion  238  is always favorably positioned in the case  220 , and thus the worm gear  242  and the control portion  238  are always favorably positioned so that control of slipping of the worm gear  242  in the direction perpendicular to the shaft is further ensured.  
         [0100]     In the second embodiment, the blocking projection  240  of the motor base  228  is fitted into the blocking hole  226  of the case  220  as a blocking means. However, in place of this, the blocking means may be formed such that the outer periphery of the fitting hole of the case member and the outer periphery of the control portion of the motor base have shapes other than a round shape, and rotation of the motor base with respect to the case member is thus blocked by the periphery of the fitting hole of the case member and the outer periphery of the control portion of the motor base fitting together.  
         [0101]     Also, the present invention may be applied to a fender mirror device for a vehicle.  
       Third Embodiment  
       [0102]     Lastly, a door mirror device for a vehicle according to a third embodiment of the present invention will be described with reference to FIGS.  10  to  17 .  
         [0103]     A door mirror device  310  includes a housing mechanism  312 . A stand  314  is provided to the housing mechanism  312 . The stand  314  is fixed to a mirror stay (not shown) which is fixed to a vehicle door. The stand  314  is provided integrally with a cylindrical support shaft  316  so as to be erect. The support shaft  316  is fixed by the stand  314  to a side of the vehicle body.  
         [0104]     As shown in detail in  FIG. 10 , on the stand  314 , there are a plurality of different circles (2 in the present embodiment). A plurality of stand concavities  318  (2 for each circle and thus a total of 4 in the present embodiment) are provided around a center which is at the support shaft  316 . Both end portions of each stand concavity  318  project to the upper side (referred to as the case  322  side hereinafter), and, as shown in detail in  FIG. 11 , are formed as a concave screw surface (C), which corresponds to an upper surface of a portion of an imaginary helical body having a central axis (B) at the support shaft  316 , to which portion a concave curvature is applied. In the present embodiment, the four stand concavities  318  are disposed in a peripheral direction of the support shaft  316  so as to alternate between the outside circle and the inside circle and at angles substantially at a 90° degree range with respect to the support shaft  316 . Also, the two stand concavities  318  on each circle face each other, and stand convexities  320  which project upward are provided between the respective concavities  318  of each same circle.  
         [0105]     Further, the housing mechanism  312  includes a substantially box-shaped case  322  and a case cover  321  which covers the case  322 . The support shaft  316  is inserted through the case  322 , and the case  322  is rotatably supported by the support shaft  316 . The case  322  is connected to a mirror for viewing the rear direction of the vehicle (not shown) via a frame and a mirror surface adjusting mechanism, and the case  322  rotates integrally with the mirror about the support shaft  316 .  
         [0106]     A substantially ring-shaped detent plate  324  is integrally fixed to a bottom surface of a bottom wall of the case  322 . The detent plate  324  has different circles (2 in the present embodiment). A plurality of case convexities  326  (2 on each circle and thus a total of 4 in the present embodiment), are provided on the different circles, around a center which is at the support shaft  316 . Each case convexity  326  projects to the lower side (to the stand  314  side), and both end portions of each case convexity  326  are formed as convex screw surfaces with the support shaft  316  as the central axis thereof. In the present embodiment, the case convexities  326  are disposed in a circumferential direction around the support shaft  316  with angles with respect to the axis of the circle having a predetermined range, and alternating between the outside circle and the inside circle. Also, the two case convexities  326  on each circle face each other. In addition, case concavities  328  which project upwards are provided between the two case convexities  326  on each circle. Engagement is possible when one end portion of each of each case convexity  326  fits into one end portion of the corresponding stand concavity portion  318 , and when the other end portion of each case convexity portion  326  fits into the other end portion of the corresponding stand concavity  318 .  
         [0107]     A motor  330  is housed and fixed at an inner portion of the case  322 . A worm gear  332  is mounted on the drive shaft  330 A of the motor  330 , and a helical gear  334  meshes with the worm gear  332 . The helical gear  334  is integrally provided with a shaft worm gear  336 , and the helical gear  334  and the shaft worm gear  336  always rotate together.  
         [0108]     A substantially cylindrical gear plate  338  through which the support shaft  316  is inserted so as to be rotatable is provided at the inner portion of the case  322 . Peripheral teeth  338 A are formed on the peripheral surface of the gear plate  338 , and the gear plate  338  meshes with the shaft worm gear  336  at the peripheral teeth  338 A. Thus, when the motor  330  is driven, a rotational force is applied to the gear plate  338  via the worm gear  332 , the helical gear  334  and the shaft worm gear  336 .  
         [0109]     As shown in detail in  FIG. 16 , a predetermined number (4 in the present embodiment) of insertion concavities  340  are formed on the upper surface of the gear plate  338 , and the insertion concavities  340  are disposed so as to have equal intervals between them in a circumferential direction thereof. Both end portions of each of the insertion concavities  340  project to the upper side (referred to as a clutch plate  342  side hereinafter), and are formed as concave screw surfaces with the support shaft  316  at a helix central axis.  
         [0110]     The substantially cylindrical clutch plate  342  is disposed above the gear plate  338 . The clutch plate  342  is disposed around the support shaft  316  such that it cannot rotate relatively thereto. As shown in  FIG. 17 , a predetermined number (4 in the present embodiment) of insertion convexities  344  are formed on the lower surface of the clutch plate  342 , and the insertion convexities  344  are disposed so as to have equal intervals between them in a circumferential direction thereof. Each of the insertion convexities  344  projects to the lower side (referred to as the gear plate  338  side hereinafter), and both end portions of each insertion convexity  344  are formed as a convex screw surface with the support shaft  316  at a helix central axis. Each of the insertion convexities  344  is inserted when both end portions thereof are fitted into one of the insertion concavities  340 , and the clutch plate  342  is thereby engaged with the gear plate  338 .  
         [0111]     A compression coil spring  346  is disposed above the clutch plate  342 , and the compression coil spring  346  is disposed around the support shaft  316 . Push nuts  348 , which are fixed to support shaft  316 , are disposed above the compression spring coil  346 . Thus, the compression spring coil  346  is anchored by the push nuts  348 , and the gear plate  338  is urged (pressed down).  
         [0112]     In addition, the frame, a holding member and the housing mechanism  312  are housed in a door mirror visor (not shown), and the door mirror visor is fixed to a frame.  
         [0113]     When a rotational force is applied to the gear plate  338  by the motor  330  being driven, the clutch plate  342  blocks the rotation of the gear plate  338 . As a result, the case  322  is caused to swing by the anti-rotational force that is applied to the gear plate  338 , in a direction for housing or in a direction in which the case is brought out for viewing. Also, the other end portion of each case convexity  326  engages with the other end portion of each stand concavity  318 , and causes the case  322  to be anchored and the mirror is stopped at the housed position, or one end portion of each case convexity  326  engages with one end portion of each stand concavity  318 , to thereby cause the case  322  to be anchored and the mirror is stopped at the position at which it is brought out for viewing.  
         [0114]     Further, when the door mirror visor receives an external force, and an external force exceeding a predetermined value acts on the case  322 , the urging force of the compression coil spring  346  is resisted, the insertion convexities  344  and the insertion concavities  340  are disengaged, the clutch plate  342  and the gear plate  338  are disengaged, and the gear plate  338  rotates together with the case  322 , with respect to the clutch plate  342 .  
         [0115]     The following is a description of the operation of the third embodiment.  
         [0116]     In the door mirror device  310 , the insertion convexities of the gear plate  338  are inserted into the insertion concavities  340  of the clutch plate  342  in a state in which the urging force of the compression coil spring  346  is being exerted, and thus the gear plate  342  is engaged with the gear plate  338 .  
         [0117]     When the motor  330  is driven, and a rotational force is applied to the gear plate  338  via the worm gear  332 , the helical gear  334  and the shaft worm gear  336 , the clutch plate  342  blocks the rotation of the gear plate  338 , and thus the anti-rotational force which is applied to the gear plate  338  swings the case  322  in the direction for housing or in the direction for viewing.  
         [0118]     The other end portion of each case convexity  326  engages with the other end portion of each stand concavity  318  and causes the case  322  to be anchored, and the mirror is stopped at the housed position, or the one end portion of each case convexity  326  engages with the one end portion of each stand concavity  318  to thereby cause the case  322  to be anchored, and the mirror is stopped at the position at which it is swung out for viewing.  
         [0119]     Further, when an external force exceeding a predetermined value acts on the case  322 , the urging force of the compression coil spring  346  is resisted, the insertion convexities  344  and the insertion concavities  340  are disengaged, the gear plate  338  is allowed to swing with respect to the clutch plate  342 , and thus the gear plate  338  swings together with the case  322  to thereby avoid the impact of the force, and damage to the gear plate  338  is prevented.  
         [0120]     Both end portions of the case convexities  326  and both end portions of the stand concavities  318  are formed as screw surfaces with the support shaft  316  being the central axis, and one end portion of each case convexity  326  and one end portion of each stand concavity  318  fit together, and also the other end portion of each case convexity  326  and the other end portion of each stand concavity  318  fit together. As a result, when one end portion of each case convexity  326  and one end portion of each stand concavity  318  are engaged, or the other end portion of each case convexity  326  and the other end portion of each stand concavity  318  are engaged, the case convexities  326  and the stand concavities  318  are always in good surface contact with each other. Thus, improvement of the durability of the case convexities  326  and the stand concavities  318  can be ensured, since wear thereof is favorably controlled.  
         [0121]     Since 4 sets of the case convexities  326  and the stand concavities  318  are provided, when one end portion of each case convexity  326  and one end portion of each stand concavity  318  are engaged, or the other end portion of each case convexity  326  and the other end portion of each stand concavity  318  are engaged, the pressure that the case convexities  326  and the stand concavities  318  each receive is reduced and thus further improvement in the durability thereof can be ensured. In addition, in the state in which one end portion of each case convexity  326  and one end portion of each stand concavity  318  are engaged, or the other end portion of each case convexity  326  and the other end portion of each stand concavity  318  are engaged, rattling of the case  322  on the stand  314  is restrained, and thus rattling of the mirror is reduced.  
         [0122]     Further, since the case convexities  326  and the stand concavities  318  are provided on each of a plurality of different circles having the support shaft  316  as a center, when one end portion of each case convexity  326  and one end portion of each stand concavity  318  are engaged, or the other end portion of each case convexity  326  and the other end portion of each stand concavity  318  are engaged, the pressure that the case convexities  326  and the stand concavities  318  each receive is decreased even further, and thus, improvement of the durability of the case convexities  326  and the stand concavities  318  can be further ensured. It should be noted that, in the present embodiment, the case convexities  326  and the stand concavities  318  are approximately three times more durable than those of the prior art. In addition, in a state in which one end portion of each case convexity  326  and one end portion of each stand concavity  318  are engaged, or the other end portion of each case convexity  326  and the other end portion of each stand concavity  318  are engaged, rattling of the case  322  on the stand  314  is further restrained, and thus rattling of the mirror is further reduced.  
         [0123]     In addition, since both end portions of each insertion convexity  344  and both end portions of each insertion concavity  340  are formed as a convex screw surface with the support shaft  316  as the central axis, the insertion convexities  344  and insertion concavities  340  are engaged at both end portions thereof. As a result, when insertion convexities  344  and insertion concavities  340  are engaged or disengaged, or when the one end portions of the insertion convexities  344  and the one end portions of the insertion concavities  340  undulate, or when the other end portions of the insertion convexities  344  and the other end portions of the insertion concavities  340  undulate, the surfaces of the insertion convexities  344  and the insertion concavities  340  are always in favorable contact with each other. Thus, improvement of the durability of the insertion convexities  344  and the insertion concavities  340  can be ensured.  
         [0124]     In this third embodiment, 4 sets of the case convexities  326  and stand concavities  318  are provided. However, the number of sets of case convexities and stand concavities can be any number not less than three.  
         [0125]     In addition, the structure of this third embodiment is such that the end portions of the case convexities  326  are formed as convex screw surfaces, and the end portion of the stand concavities  318  is formed as concave screw surfaces. However, the structure may be such that the end portions of the case convexities are formed as concave screw surfaces, and the end portions of the stand concavities  318  are formed as convex screw surfaces.  
         [0126]     Further, in the present embodiment, end portions of the case convexities  326  and end portions of the stand concavities  318  are formed as screw surfaces with the support shaft  316  at the central axis. However end portions of the case convexities and end portions of the stand concavities may be formed as inclined surfaces having an upper area and a lower area along the radial direction of the support shaft.  
         [0127]     In addition, the structure of this third embodiment is such that the end portions of the insertion convexities  344  are formed as convex screw surfaces, and the end portions of the insertion concavities  340  are formed as concave screw surfaces. However, the structure may be such that the end portions of the insertion convexities  344  are formed as concave screw surfaces, and the end portions of the insertion concavities  340  are formed as convex screw surfaces.  
         [0128]     Further, in the present embodiment, the insertion concavities  340  are provided on the gear plate  338 , and insertion convexities  344  are provided on the clutch plate  342 . However, insertion convexities may be provided on the gear plate, and insertion concavities on the clutch plate.  
         [0129]     The present invention may also be applied to a fender mirror device for a vehicle.