Abstract:
An automatic door opening and closing apparatus includes: a movable portion that has a rectilinear rack that is moved reciprocally by a pinion, and a supporting portion that rotatably supports a planetary gear; a fixed rack that meshes with the planetary gear; and an arm that is mounted so as to be rotatable around a pin that is at a distance in a radial direction from a center of rotation of the planetary gear, and that is interposed between the pin and a tailgate. An automatic door opening and closing apparatus is provided that reduces dampening in the driving force that is caused by friction and improves the degree of design freedom.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     Priority is claimed on Japanese Patent Application No. 2004-252522, filed Aug. 31, 2004, the contents of which are incorporated herein by reference.  
         [0003]     The present invention relates to an automatic opening and closing apparatus for a door of a vehicle such as, for example, an automobile.  
         [0004]     2. Description of Related Art  
         [0005]     Conventionally, an automatic door opening and closing apparatus that opens and closes a tailgate of a vehicle such as an automobile using electric power is known. Among these automatic door opening and closing apparatuses are those whose apparatus body is fixed to a roof panel and is covered by lining or the like so as to be separate from the vehicle interior, and a tailgate is connected to an arm member that extends out from the apparatus body. However, in some cases, when the tailgate is open, the hole into which the arm member is inserted is particularly noticeable, so that there is a deterioration in the quality of the external appearance. Because of this, an apparatus has been proposed (see, for example, Japanese Patent Application Unexamined Publication No. 2002-174072) in which the hole is kept at the minimum possible size, and the arm member, which is formed in an arc shape centering on a hinge center of the tailgate, is provided so as to be able to slide inside a housing that has the same arc shape.  
         [0006]     However, in the above described automatic door opening and closing apparatus, because a housing is provided that guides an arm member that has an arc-shaped trajectory, the problem arises that the driving force is dampened by friction between the arm member and the housing.  
         [0007]     Moreover, because the number of components is increased as a result of the housing being provided, the problem arises that the number of assembly steps increases leading to increased costs.  
         [0008]     Furthermore, if the trajectory of the arm member is altered, it is necessary to alter the design of both the arm member and the housing, so that the problem arises that the degree of design freedom is deteriorated.  
         [0009]     Therefore, the present invention provides an automatic door opening and closing apparatus that reduces any dampening in the driving force that is caused by friction and also improves the degree of design freedom.  
       SUMMARY OF THE INVENTION  
       [0010]     In order to solve the above described problems, according to the present invention, there is provided an automatic door (for example, the tailgate  4  of the embodiment) opening and closing apparatus comprising: a movable portion (for example, the movable portion  28  of the embodiment) having a sliding portion (for example, the rectilinear rack  29  of the embodiment) that is moved reciprocally by a driving device (for example, the pinion  23  of the embodiment), and having a supporting portion (for example, the supporting portion  18  of the embodiment) that rotatably supports a gear member (for example, the planetary gear  16  of the embodiment); a fixed portion (for example, the fixed rack  12  of the embodiment) that meshes with the gear member; and an arm member (for example, the arm member  9  of the embodiment) that is mounted so as to be rotatable around a connecting point (for example, the pin  21  of the embodiment) that is at a distance in a radial direction from a center of rotation of the gear member, and that is interposed between the connecting point and a door.  
         [0011]     With this structure, when the sliding portion moves reciprocally the connecting point of the gear member is displaced so as to describe an arc-shaped trajectory, and the arm member can be provided with an arc-shaped displacement.  
         [0012]     Moreover, by, for example, changing the radius of the gear member, it is possible to easily change the distance between the center of rotation of the gear member and the connecting point. It is thus possible to freely change the arc-shaped trajectory of the arm member.  
         [0013]     Furthermore, by using a gear member, it is possible to set a short transmission path for the driving force to the arm member. Therefore, a reduction in the size of the apparatus body can be achieved.  
         [0014]     Preferably, in the above automatic door opening and closing apparatus, the sliding portion and the supporting portion are formed as a single body.  
         [0015]     With this structure, the structure of the movable portion can be simplified and the rigidity thereof can be secured.  
         [0016]     Preferably, in the above automatic door opening and closing apparatus, the movable portion moves reciprocally while being guided by a slide supporting portion (for example, the horizontal portion  13  of the embodiment) of the fixed portion that meshes with the gear member.  
         [0017]     With this structure, by making the fixed portion that meshes with the gear member also function as the slide guiding member for the movable portion, it is possible to decrease the number of component parts.  
         [0018]     Preferably, in the above automatic door opening and closing apparatus, one of the movable portion and the slide supporting portion has a T-shaped cross section and engages with the other of the movable portion and the slide supporting portion.  
         [0019]     With this structure, because the positions of two directions that are orthogonal to the slide direction of the movable portion, for example, if this apparatus is used in a tailgate, the up-down and left-right directions of the vehicle, are fixed, the sliding of the movable portion can be stabilized. 
     
    
     BRIEF DESCRIPTION THE DRAWINGS  
       [0020]      FIG. 1  is a side view showing a rear portion of a vehicle that is equipped with the power tailgate of an embodiment of this invention, and shows a state in which the tailgate is fully closed.  
         [0021]      FIG. 2  is a side view showing a rear portion of a vehicle that is equipped with the power tailgate of an embodiment of this invention, and shows a state in which the tailgate is fully open.  
         [0022]      FIG. 3  is a typical view showing the power tailgate apparatus of an embodiment of this invention.  
         [0023]      FIG. 4  is a cross-sectional view taken along a line A-A in  FIG. 3  of an embodiment of this invention.  
         [0024]      FIG. 5  is a typical view showing another aspect of an embodiment of this invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]     An embodiment of this invention will now be described together with the drawings. Note that a case is described in which this embodiment is applied to the tailgate of an automobile and, particularly, of a station wagon.  
         [0026]     As is shown in  FIGS. 1 and 2 , a rear aperture portion  2  is formed in a rear portion of a vehicle body  1 . A tailgate (i.e., a door)  4  is provided at a top edge of the rear aperture portion  2  so as to be able to open and close freely via a hinge  3 . A gas spring  5  is connected to the tailgate  4 , and the gravitational balance is adjusted by the urging force of the gas spring  5  when the tailgate is being opened or closed. Here, the tailgate  4  swings around a hinge center of a hinge  3  whose axis runs in the vehicle transverse direction between the fully closed state shown in  FIG. 1  and the fully open state shown in  FIG. 2 .  
         [0027]     As is shown in FIGS.  1  to  3 , a roof side rail  7 , which is a frame member, is provided on both sides on a roof panel  6  of the vehicle body  1 . An apparatus body  8  of the power tailgate apparatus is provided inside the roof side rail  7 . An arm (i.e., an arm member)  9  is attached to the apparatus body  8 , and a distal end of this arm  9  is rotatably attached to a top portion on the vehicle interior side of the tailgate  4 . In addition, a lining  10  is provided that covers the roof panel  6  and the roof side rail  7  from the vehicle interior side, and an aperture portion  11  into which the arm  9  is inserted is formed in the lining  10  on the tailgate  4  side thereof.  
         [0028]     As is shown in typical view in  FIGS. 3 and 4 , a rod-shaped fixed rack (i.e., a fixed portion)  12  is provided on the apparatus body  8 . This rack  12  is formed having a T-shaped cross section that is formed by a horizontal portion (i.e., a slide support portion)  13  and a vertical portion  14 , and is fixed to the roof side rail  7  while being aligned in the vehicle longitudinal direction. Moreover, teeth  15  are formed on a bottom surface of the vertical portion  14  of the fixed rack  12 , and a planetary gear (i.e., a gear member)  16  is positioned below the fixed rack  12 . The planetary gear  16  is a disc-shaped gear that has a rotation shaft  17  that extends in the vehicle transverse direction. The rotation shaft  17  is provided so as to be supported by a bearing  19  of a supporting portion  18  that is described below. The teeth  15  of the fixed rack  12  mesh together with teeth  20  of the planetary gear  16 .  
         [0029]     A pin (i.e., a linking portion)  21  that extends in the vehicle transverse direction is formed on a left side (i.e., the side facing towards a person viewing  FIG. 3 ) of the planetary gear  16  in substantially a center portion between the rotation shaft  17  of the planetary gear  16  and an outer circumference of the planetary gear  16 .  
         [0030]     One end of the arm  9  that is formed so as to bend gently upwards is rotatably supported by the hinge pin  21 . The other end of this arm  9  is rotatably supported via a bracket  22  at a surface of the tailgate  4  (shown in typical view in  FIG. 3 ) that is on the vehicle interior side. Namely, because the pin  21  is provided extending in the vehicle transverse direction, displacement in the left-right direction of the arm  9  is restricted, and the arm  9  is able to travel along a stable trajectory. Here, in a state in which the planetary gear  16  is in an intermediate position along this movement stroke, the pin  21  is positioned on an extended line that joins an input shaft  24  of a pinion (i.e., a drive device)  23  that is described below and the rotation shaft  17  of the planetary gear  16 . This position is the lowest point of displacement of the pin  21 . Note that the pin  21  may also be formed on the right side surface of the planetary gear  16 .  
         [0031]     The supporting portion  18  is formed by a shoulder portion  25  that is located above the fixed rack  12 , and extended portions  26  and  26  that each extend downwards from both the left and right side edges of the shoulder portion  25 . The bearing  19  that supports the rotation shaft  17  of the planetary gear  16  (described above) is formed in a bottom portion of each extended portion  26 . Furthermore, engaging portions  27  and  27  are provided facing each other at an inner side of top portions of the extended portions  26 . The horizontal portion  13  of the fixed rack  12  is housed in a space that is formed by the engaging portions  27  and the shoulder portion  25 . The horizontal portion  13  consequently performs the function of a rail so that the supporting portion  18  is able to slide freely in the vehicle longitudinal direction. In addition, the vertical portion  14  is located extending downwards between the respective engaging portions  27  and  27 . Namely, displacement of the supporting portion  18  in the up-down and left-right directions is restricted while sliding thereof in the vehicle longitudinal direction is allowed.  
         [0032]     A rectilinear rack (i.e., a slide portion)  29  that together with the supporting portion  18  constitutes a movable portion  28  is formed integrally with a top portion of the supporting portion  18 . The rectilinear rack  29  is formed in a rod shape, and is positioned so as to be aligned with the fixed rack  12 . Teeth  30  are formed on a top surface of the rectilinear rack  29 , and the pinion  23  is placed above these teeth. The pinion  23  is formed in a columnar shape that extends in the vehicle transverse direction, and teeth  31  are formed on a circumference of the pinion  23 . The teeth  30  of the rectilinear rack  29  and the teeth  31  of the pinion  23  mesh together. Note that it is also possible to provide the rectilinear rack  29  and the supporting portion  18  as separate components and to fix the rectilinear rack  29  to the supporting portion  18 .  
         [0033]     One end of the input shaft  24  that runs in the vehicle transverse direction is fixed to the pinion  23 . An electric motor  32  is connected to the other end of the input shaft  24  and the electric motor  32  is fixed to the roof side rail  7 . Namely, because the input shaft  24  of the pinion  23  is fixed via the electric motor  32  to the roof side rail  7 , when the pinion  23  is rotated by the electric motor  32 , only the rectilinear rack  29  slides in the longitudinal direction along the fixed rack  12  and there is no change in the position of the pinion  23 . What is known as a rack and pinion is formed by the pinion  23  and the rectilinear rack  29 .  
         [0034]     Namely, if the pinion  23  is rotated by switching on the electric motor  32  in order to change the tailgate  4  from a fully closed state to a fully open state, the rectilinear rack  29  and the supporting portion  18  that had hitherto been positioned on the vehicle forward side slide to the vehicle rearward side. In the same way, the planetary gear  16  that is supported by the supporting portion  18  also rolls along the fixed rack  12  from the vehicle forward side so as to move to the vehicle rearward side. At this time, because the trajectory of the pin  21  is the same as that of a so-called cycloid, which is the track of a point on the circumference of a circle as the circle rolls along a straight line, one end of the arm  9  that is supported by the pin  21  is displaced while describing a downward-facing convex arc (indicated by the chain line in  FIG. 3 ).  
         [0035]     In addition, as the one end of the arm  9  is displaced while tracing an arc, the other end of the arm  9  pushes up the tailgate  4  while describing an arc that is centered on the hinge center of the hinge  3 . Accordingly, the tailgate  4  swings from a fully closed position to a fully open position.  
         [0036]     On the other hand, when the tailgate  4  is swung from a fully open state to a fully closed state, by rotating the pinion  23  in reverse using the electric motor  32 , the rectilinear rack  29  slides from the vehicle rearward side to the vehicle forward side. In addition, conversely from when the tailgate  4  is swung from a fully closed position to a fully open position, the one end of the arm  9  is displaced from the vehicle rearward side to the vehicle forward side while describing an arc, so that the other end of the arm  9  pulls the tailgate  4  to the vehicle interior side and the tailgate  4  is swung from a fully open position to a fully closed position.  
         [0037]     As a result, according to the above described embodiment, because the pin  21  of the planetary gear  16  is displaced so as to describe an arc-shaped trajectory when the rectilinear rack  29  is moved reciprocally, so that it is possible to furnish the one end of the arm  9  with an arc-shaped displacement, the aperture portion  11  can be reduced to the minimum possible size so that the quality of the external appearance thereof can be improved. In addition, any dampening of the drive force that is caused by friction can be suppressed.  
         [0038]     Moreover, by changing the distance between the rotation shaft  17  of the planetary gear  16  and the pin  21 , it is possible to freely change the curvature of the arc described by the one end of the arm  9 , thereby enabling the degree of design freedom to be improved.  
         [0039]     Furthermore, while a simplification of the structure of the movable portion  28  that is made up of the rectilinear rack  29  and the supporting portion  18  is achieved, the rigidity thereof can also be secured. In addition, the size of the apparatus body  8  can be further reduced.  
         [0040]     Moreover, if the fixed rack  12  that meshes with the planetary gear  16  doubles as a slide guide member for the supporting portion  18 , the number of components can be decreased. As a result, the number of assembly steps can be decreased so that the load on an operator is lightened.  
         [0041]     Furthermore, because the position of the supporting portion  18  is fixed in the up-down and left-right directions, the supporting portion  18  can be made to slide in a stable fashion thereby improving the reliability of an opening or closing operation.  
         [0042]     Next, another aspect of the present embodiment will be described based on  FIG. 5 .  FIG. 5  shows a case in which the planetary gear shown in  FIG. 3  has been replaced with what is known as a sector gear.  
         [0043]     As is shown in  FIG. 5 , a sector gear  33  is a gear in which teeth are only formed on an outer circumferential portion of what is substantially a semicircle that, if, for example, the planetary gear  16  described in the above embodiment were to be rotated, is the portion that meshes with the teeth  20  of the fixed rack  12 . A rod portion  34  is formed on a rectilinear portion of the substantially semicircle protruding outwards from substantially a center of this rectilinear portion. The pin  21 , by which one end of the arm  9  is supported in the same way as in the above described planetary gear  16 , is formed in an end portion of this rod portion  34 . Note that the remainder of the structure of this sector gear  33  is the same as in the above described embodiment and a description thereof is consequently omitted.  
         [0044]     As a result, according to the above other aspect of the described embodiment, because the weight especially is reduced compared to when the planetary gear  16  is used by employing a structure that uses the sector gear  33 , an improvement in fuel consumption can be achieved.  
         [0045]     Moreover, the further advantage is achieved that the curvature of the above described arc can be easily changed simply by changing the length of the rod portion  34 .  
         [0046]     Note that the present invention is not limited to the above described embodiment and it may also be applied to doors other than tailgates such as side doors. Furthermore, it can also be used for doors other than those of vehicles and lids and the like provided that they swing open and closed.  
         [0047]     According to one embodiment of the present invention, when the slide portion is moved reciprocally, because the connecting point of the gear member is displaced so as to describe an arc-shaped trajectory and the arm member can be provided with an arc-shaped displacement, the effect is obtained that it is possible to suppress any dampening of the drive force that is caused by friction.  
         [0048]     Moreover, for example, because it is possible by changing the diameter of the gear member to easily change the distance between the center of rotation of the gear member and the connecting point, the arc-shaped trajectory of the arm member can be feely changed. Accordingly, the effect is obtained that the degree of design freedom is improved.  
         [0049]     Furthermore, because it is possible by using a gear member to set a short transmission path for the driving force to the arm member, a reduction in the size of the apparatus body can be achieved. Accordingly, the effect is obtained that it is possible to secure a wider space on the door inner side.  
         [0050]     According to another embodiment of the present invention, because the structure of the movable portion can be simplified and the rigidity thereof can be improved, the effect is obtained that a further reduction in the size of the apparatus becomes possible.  
         [0051]     According to still another embodiment of the present invention, because it is possible to decrease the number of component parts by making the fixed portion that meshes with the gear member also function as the slide guiding member for the movable portion, the effect is obtained that the number of assembly steps can be decreased and the load on an operator can be lightened.  
         [0052]     According yet another embodiment of the present invention, because the positions of two directions that are orthogonal to the slide direction of the movable portion, for example, if this apparatus is used in a tailgate, the up-down and left-right directions of the vehicle, are fixed, the sliding of the movable portion can be stabilized. Accordingly, the effect is obtained that the reliability of the apparatus can be improved.  
         [0053]     While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as limited by the foregoing description and is only limited by the scope of the appended claims.