Patent Publication Number: US-2012032476-A1

Title: Roof device for vehicle

Description:
TECHNICAL FIELD 
     The present invention relates to a roof device for a vehicle. 
     BACKGROUND ART 
     A conventionally known roof device for a vehicle is described in, for example, Patent Document 1. The roof device for a vehicle includes: a pair of guide rails extending in directions along the front and back of the vehicle on both sides in the widthwise direction of the vehicle; a front housing connecting the front ends of the guide rails to each other; and a pair of operation mechanisms supporting a movable panel guided along the guide rails. Additionally, a toothed belt, which is three-dimensionally deformable, is connected to each operation mechanism. A drive gear rotated and driven by a drive source is provided in the middle of the front housing. The toothed belt engages with the drive gear. This toothed belt is movably accommodated in a guide portion (casing pipe) molded in a substantially quadrangular shape corresponding to the outer shape of the toothed belt and locked in the front housing. Therefore, when the toothed belt is moved by rotating and driving the drive gear in order to transmit drive force to an operation mechanism, the movement of the toothed belt is guided by the guide portion and the guide rails, thus transmitting drive force to the operation mechanism. 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: Japanese Laid-Open Patent Publication 
       
    
     SUMMARY OF THE INVENTION 
     Problems that the Invention is to Solve 
     According to Patent Document 1, a step is likely to form due to installation error, for example, at the boundary between the guide portion and the guide rails. If a step is present, the teeth of the toothed belt contacts the step during the movement of the toothed belt, which can produce noise. 
     Accordingly, it is an objective of the present invention to provide a roof device for a vehicle, which reduces noise and the like resulting from contact between a toothed belt and a guide section. 
     Means for Solving the Problems 
     In order to achieve the foregoing object, a roof device for a vehicle is provided according to the present invention. 
     A roof device for a vehicle includes a movable panel, a pair of guide rails, operation mechanisms, a drive gear, toothed belts, drive-side guide sections, rail-side guide sections, sliding sections, and a fitting section. The movable panel is capable of opening and closing an opening provided in the vehicle. The guide rails are located on both sides of the opening in a widthwise direction of the vehicle, and are adapted to extend in a direction along the front and back of the vehicle. The operation mechanisms are guided by the corresponding guide rails and support the movable panel. The drive gear is rotated and driven by a drive source. The toothed belt engages with the drive gear and is connected to the corresponding operation mechanism. The toothed belt has a plurality of rack teeth arranged in a longitudinal direction of the toothed belt. The drive-side guide section extends between the drive gear and each guide rail so as to surround the corresponding toothed belt and guides movement of the toothed belt. The rail-side guide section is formed in each guide rail, and extends toward the operation mechanism so as to surround the toothed belt, and guides movement of the toothed belt. The sliding section is formed integrally with each toothed belt. A fitting section is formed in at least each drive-side guide section or each rail-side guide section and slidably fits on the corresponding sliding section. The fitting section restricts movement of the rack teeth of each toothed belt toward the corresponding opposite face of the drive-side guide section or rail-side guide section. 
     According to the configuration, in the toothed belt, the sliding section fits in the fitting section so as to be slidable. This restricts the rack teeth from movement toward the opposite face of the drive-side guide section or rail-side guide section in which the fitting section is formed. This ensures a required clearance between the rack teeth and the opposite face. Therefore, when the toothed belt enters one of the drive-side guide section and the rail-side guide section from the other, the opposite face and the rack teeth are prevented from contacting each other at the edge end of the drive-side guide section or rail-side guide section. Hence, noise thus resulting can be reduced. 
     In this case, “to surround the toothed belt” does not means that the drive-side guide section has to be formed so as to cover the toothed belt all around. However, it means that, for example, an opening may be formed in part of a groove. 
     Preferably, the fitting section may include a drive-side fitting section formed in each drive-side guide section and a rail-side fitting section formed in the rail-side guide section. 
     According to the configuration, the rack teeth of the toothed belt are restricted from movement toward the opposite faces of the drive-side guide section and rail-side guide section respectively. Thus, a required clearance can be ensured between the rack teeth and the opposite faces of the drive-side guide section and rail-side guide section respectively. Accordingly, even if a step forms between the opposite faces at the boundary between the drive-side guide section and the rail-side guide section due to, for example, variations in manufacture or assembly error, the step is absorbed in the range of the clearance. Accordingly, contact of the rack teeth during the movement of the toothed belt, and hence emission of resulting noise is thus prevented. 
     Preferably, the end of the drive-side guide section connected to the corresponding rail-side guide section may have an inclined part that gradually increases the clearance between the opposite face and the rack teeth as the inclined part approaches the rail-side guide section. 
     According to the configuration, the clearance between the opposite face and the rack teeth gradually increases toward the edge end of the drive-side guide section by virtue of the inclined part, and this clearance is defined maximum at this edge end. This makes it possible to more reliably prevent contact between the opposite face and the rack teeth at the edge end when the toothed belt enters the drive-side guide section from the rail-side guide section. Therefore, the toothed belt can smoothly be drawn into the drive-side guide section along the inclined part. 
     Preferably, the sliding sections are formed on both sides of each toothed belt in a widthwise direction of the toothed belt and extend in the longitudinal direction of the toothed belt. The fitting section may include a first fitting section and second fitting section arranged so as to face the corresponding sliding sections of each toothed belt. 
     According to the configuration, the sliding sections formed on both sides of the toothed belt in the widthwise direction of the toothed belt fit in the first and second fitting sections. Accordingly, unconstrained by the shape of the opposite face of the drive-side guide section or rail side guide to the rack teeth, the belt can move more stably. Especially, this configuration is applied in the configuration described in claim  3 . This also yields the advantage that movement of the toothed belt can be guided by the drive-side guide section regardless of the provision of the inclined part. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view of a sun roof device according to one embodiment of the present invention; 
         FIG. 2  is an enlarged view of a surrounded part indicated by the reference number  2  in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken along the line  3 - 3  of  FIG. 2 ; 
         FIG. 4  is a cross-sectional view taken along the line  4 - 4  of  FIG. 2 ; 
         FIG. 5  is a cross-sectional view taken along the line  5 - 5  of  FIG. 1 ; 
         FIG. 6  is a perspective view of a belt according to the present embodiment; 
         FIG. 7  is a cross-sectional view taken along the line  7 - 7  of  FIG. 1 ; 
         FIG. 8  is a cross-sectional view taken along the line  8 - 8  of  FIG. 7 ; 
         FIG. 9  is a cross-sectional view of a belt and guide groove according to a modified embodiment of the present invention; and 
         FIG. 10  is a cross-sectional view of a belt and guide groove according to another modified embodiment of the present invention. 
     
    
    
     BEST MODES FOR CARRYING OUT THE INVENTION 
     One embodiment according to the present invention will hereinafter be described with reference to  FIGS. 1 to 8 . 
     As shown in  FIG. 1 , a sunroof device  10  is installed in a substantially quadrangular opening  12  formed in a roof  11  of a vehicle. The opening  12  has left and right edges extending in the above-mentioned direction of the vehicle (i.e., in directions along the front and back of the roof  11 ) on the left and right sides of the vehicle. The sunroof device  10  includes a right guide rail  13   a  and a left guide rail  13   b  fixed to the roof  11  so as to extend along the left and right edges of the opening  12 . The guide rails  13   a  and  13   b  are formed, for example, by extrusion-molding aluminum alloy. 
     An operation mechanism  14  is supported by each of the guide rails  13   a  and  13   b  so as to be movable along the guide rails  13   a  and  13   b . A movable panel  15  made of glass extends between the operation mechanisms  14  so as to be able to close the opening  12 . The movable panel  15  is supported and fixed by the operation mechanisms  14 . While moving along the guide rails  13   a  and  13   b , the pair of operation mechanisms  14  moves the movable panel  15  by virtue of the shape of the guide rails  13   a  and  13   b  and also tilt it upward and downward. The opening  12  is opened or closed, for example, by this movement of the movable panel  15 . Specifically, when the opening  12  is opened or closed, the operation mechanisms  14  controls the position of the movable panel  15  in conjunction with the guide rails  13   a  and  13   b.    
     The sunroof device  10  includes a front housing  21  made of resin, which extends along the width of the vehicle so as to connect the front ends of the guide rails  13   a  and  13   b . In the middle of the front housing  21  in the widthwise direction of the vehicle is an electric motor  22  serving as a drive source. A drive gear  23  formed by a spur gear, which is rotated and driven by the electric motor  22 , is supported by the front housing  21  so as to be rotatable around a rotation shaft that extends in the direction of the height of the vehicle. 
     Formed in the front housing  21  are four guide grooves, which are first to fourth guide grooves  21   a  to  21   d  of substantially U-shaped cross section. The first to fourth guide grooves  21   a  to  21   d  correspond to drive-side guide sections. 
     As shown in  FIG. 1 , the first guide groove  21   a  extends from the drive gear  23  toward a first side (the left side of the vehicle; downward in  FIG. 1 ) in the widthwise direction of the vehicle. In addition, this first guide groove  21   a  is curved at the first end (left end) of the front housing  21  toward the back of the vehicle and further extends to a point where the guide groove  21   a  is in contact with the front end of the left guide rail  13   b . In addition, the second guide groove  21   b  extends from the drive gear  23  to the second end (the right end) of the front housing  21 , that is, toward a second side (the right side of the vehicle; upward in  FIG. 1 ) in the widthwise direction of the vehicle. Furthermore, on the inside of the second guide groove  21   b  (i.e., on the back of the vehicle), the third guide groove  21   c  extends from the drive gear  23  toward the second side (downward in  FIG. 1 ) in the widthwise direction of the vehicle. In addition, the third guide groove  21   c  is curved at the second end (at the right end) of the front housing  21  toward the back of the vehicle and further extends to a point where the guide groove  21   c  is in contact with the front end of the right guide rail  13   a . On the inside of the first guide groove  21   a  (i.e., on the back of the vehicle), the fourth guide groove  21   d  extends from the drive gear  23  to the first side (i.e., upward in  FIG. 1 ) in the widthwise direction of the vehicle. In addition, the fourth guide groove  21   d  is folded in a substantially U-shape at the point where the groove  21   d  abuts on the guide groove  21   a . The total length of the first and second guide grooves  21   a  and  21   b  is substantially equal to the total length of the third and fourth guide grooves  21   c  and  21   d . Additionally, a rail-side guide groove  16 , which serves as a rail-side guide section, is formed in the right guide rail  13   a . This guide groove  16  extends in directions along the front and back of the vehicle so as to be continuous with the end of the third guide groove  21   c  that faces the guide rail  13   a . Another rail-side guide groove  16 , which serves as a rail-side guide section, is formed in the left guide rail  13   b . This guide groove  16  extends in the directions of the front and back of the vehicle so as to be continuous with the first guide groove  21   a  that faces the guide rail  13   b.    
     A first belt  24  made of, for example, resin or rubber, is accommodated in each of the first and second guide grooves  21   a  and  21   b  so as to be movable. Similarly, a second belt  25  identical in shape and material to the first belt  24  is accommodated in each of the third and fourth guide grooves  21   c  and  21   d  so as to be movable. 
     The rack teeth  26  (refer to  FIG. 2 ) of the first belt  24  engage with the drive gear  23  at the front of the drive gear  23  between the first and second guide grooves  21   a  and  21   b . The rack teeth  26  of the second belt  25  engage with the drive gear  23  at the back of the drive gear  23  between the third and fourth guide grooves  21   c  and  21   d . Each of the teeth of the drive gear  23  has the shape of a substantially truncated cone the diameter of which gradually decreases towards a higher position in the vehicle. That is, each tooth of the drive gear  23  is formed such that the diameter of its top is smaller than that of its base. 
     The first and second belts  24  and  25  are provided in the corresponding guide grooves,  21   a  to  21   d , such that the rack teeth  26  of the belt  24  and the rack teeth  26  of the belt  25  face each other. The first belt  24  is formed such that its first end entering the left guide rail  13   b  is connected to the left operation mechanism  14  whereas its second end is free within the second guide groove  21   b . As for the second belt  25 , its first end entering the right guide rail  13   a  is connected to the right operation mechanism  14  whereas its second end is free within the fourth guide groove  21   d.    
     The movement of the first belt  24  is guided by the first and second guide grooves  21   a  and  21   b . In this case, the movement of the part of the first belt  24  extending from the end of the first guide groove  21   a  and connected to the operation mechanism  14  is guided by the rail-side guide groove  16  of the left guide rail  13   b . On the other hand, the movement of the second belt  25  is guided by the third and fourth guide grooves  21   c  and  21   d . In this case, the movement of the part of the second belt  25  extending from the end of the third guide groove  21   c  and connected to the operation mechanism  14  is guided by the rail-side guide groove  16  of the right guide rail  13   a . Accordingly, the belts  24  and  25  are able to transmit drive force from the electric motor  22  to the corresponding operation mechanisms  14 . 
     Incidentally, the length of each of the belts  24  and  25  and the position of their engagement with the drive gear  23  are adjusted such that when the electric motor  22  is driven, the operation mechanisms  14  move forward and backward within the corresponding guide rails,  13   a  and  13   b , in synchronization with each other. For example, if the drive gear  23  is rotated counterclockwise in  FIG. 1 , the first belt  24  and second belt  25  enter the left and right guide rails  13   a  and  13   b  respectively from the front housing  21 . Accordingly, the operation mechanisms  14  synchronously move backward along the corresponding guide rails  13   a  and  13   b . Therefore, the movable panel  15  opens the opening  12  while keeping the widthwise direction of the vehicle horizontal. At this time, the free end of each of the belts  24  and  25  moves toward the drive gear  23 . On the other hand, when the drive gear  23  is rotated clockwise in  FIG. 1  by driving the electric motor  22 , the belts  24  and  25  move from the corresponding guide rails  13   a  and  13   b  to the front housing  21 . Accordingly, the operation mechanisms  14  synchronously move forward along the corresponding guide rails  13   a  and  13   b . Therefore, the movable panel  15  closes the opening  12  while keeping the widthwise direction of the vehicle horizontal. At the time, the free end of each of the belts  24  and  25  move apart the drive gear  23 . 
     Referring to  FIGS. 2 to 6 , a belt guide holding structure formed in each of the first to fourth guide grooves  21   a  to  21   d  will now be described in detail below.  FIG. 2  is an enlarged view of a surrounded part indicated by the reference number  2  in  FIG. 1 .  FIG. 3  is a cross-sectional view taken along the line  3 - 3  of  FIG. 2 .  FIG. 4  is a cross-sectional view taken along the line  4 - 4  of  FIG. 2 .  FIG. 5  is a cross-sectional view taken along the line  5 - 5  of  FIG. 1 . 
     As shown in  FIG. 1 , the front housing  21  has a flat bottom wall  31 , which extends over substantially the entire outside shape in a plan view. In addition, as shown in  FIG. 2 , the front housing  21  integrally has first and second parallel flat sidewalls  32  and  33 , which extend from the bottom wall  31  in the direction of the height of the vehicle. The first sidewall  32  has a face  32   a  opposite the second sidewall  32 . This opposite face  32   a  faces the rack teeth  26  of the first belt  24  accommodated in the first guide groove  21   a . The first belt  24  has a rear face  28  opposite the rack teeth  26 . This rear face  28  faces the second sidewall  33 . 
     As shown in  FIG. 3 , at the position the first guide groove  21   a , the bottom wall  31  has a drive-side fitting section  31   a  of substantially quadrangular cross-section open in an upward direction. This fitting section  31   a  extends over substantially the entire length of the bottom wall  31  in the same direction as the first guide groove  21   a.    
     As shown in  FIGS. 2 and 4 , flat pressing sections  35  are formed integrally with the first sidewall  32  so as to project from the upper end of the sidewall  32  toward the second sidewall  33 . The pressing sections  35  are provided at intervals along the length of the first guide groove  21   a . In the pressing section  35 , formed on the internal face facing the first belt  24  is a drive-side fitting section  35   a  of substantially quadrangular cross-section open in a downward direction. The pressing sections  35  suppress upward displacement of the first belt  24  from the first guide groove  21   a  during movement. Each of the parts of the bottom wall  31  facing the pressing sections  35 , has a through hole  36  that is open in the direction of the height of the vehicle; however, each of these parts is not provided with a drive-side fitting section  31   a . The fitting sections  31   a  and  35   a  correspond to first and second fitting sections respectively. In addition, the holding structure, including the drive-side fitting sections  35   a  and  31   a  and pressing sections  35 , which is provided for the first guide groove  21   a  described above is identical in configuration to the other second to fourth guide grooves  21   b  to  21   d . Therefore, explanation thereof is omitted. 
     As shown in  FIG. 5 , the rail-side guide groove  16  of the left guide rail  13   b  extends in the directions of the front and back of the vehicle (i.e., in the direction orthogonal to the sheet of the drawing). The rail-side guide groove  16  is adjacent to a rail  40 , which guides movement of the operation mechanism  14 , in the widthwise direction of the vehicle. The cross-sectional shape of the rail-side guide groove  16  is substantially identical to the cross-sectional shape of the guide groove  21   a  described above (refer to  FIG. 3 ). Specifically, the left guide rail  13   b  includes: a bottom wall  41  adjacent to the rail  40  and extending in the directions of the front and back of the vehicle (i.e., in the direction orthogonal to the sheet of  FIG. 5 ); a sidewall  42  separated from the rail  40  in the widthwise direction of the vehicle and extending in the direction of the height of the vehicle from the edge of the bottom wall  41 ; and a lid wall  43  extending from the upper end of the sidewall  42  in the widthwise direction of the vehicle so as to be parallel to the bottom wall  41 . In addition, the left guide rails  13   b  include a pair of holding walls  44   a  and  44   b  extending from the bottom wall  41  and lid wall  43  respectively in the direction of the height of the vehicle so as to be parallel to each other at the edge adjacent to the rail  40 . The sidewall  42  has a face  42   a  opposite the holding walls  44   a  and  44   b . This opposite face  42   a  faces the rack teeth  26  of the first belt  24  accommodated in the rail-side guide groove  16 . The rail-side guide grooves  16  are defined by these internal wall faces at the bottom wall  41  and the like, so as to have a substantially U-shaped cross-section. The rail-side guide groove  16  is open toward the rail  40  in the widthwise direction of the vehicle. In addition, the bottom wall  41  and lid wall  43  have rail-side fitting sections  20   a  and  20   b  respectively on their internal walls facing each other. The openings of the rail-side fitting sections  20   a  and  20   b  face each other. In  FIG. 5 , the right guide rail  13   a  is symmetrical with the left guide rail  13   b , and is identical in configuration to the left guide rail  13   b . Therefore, explanation thereof is omitted. 
     Each of the belts  24  and  25  are accommodated in the corresponding guide grooves  21   a  to  21   d  and rail-side guide grooves  16  so as to be movable in such a manner that parts of the belts  24  and  25  along their lengths are surrounded by those corresponding grooves (refer to  FIGS. 2 to 5 ). As shown in  FIG. 6 , each of the belts  24  and  25  includes a belt section  27  and a plurality of rack teeth  26  arranged at fixed intervals along the length of the belt section  27 . In addition, each of the belts  24  and  25  has a pair of sliding sections  29  of substantially quadrangular cross-section such that the sliding sections  29  project from the belt section  27  on both sides in the widthwise direction of the belt section  27 . The sliding sections  29  fit in the drive-side fitting sections  31   a  and  35   b , which are formed in the first to fourth guide grooves  21   a  to  21   d  so as to be slidable. Therefore, since the sliding sections  29  fit in the drive-side fitting sections  31   a  and  35   a  of the corresponding guide grooves  21   a  to  21   d , each of the belts  24  and  25  move along the guide grooves  21   a  to  21   d  while movement (i.e., displacement) is restricted in the direction in which the first and second sidewalls  32  and  33  face each other (in particular, in the direction in which the rack teeth  26  approach the opposite face  32   a  of the first sidewall  32 ). 
     Similarly, the sliding sections  29  respectively fit in the rail-side fitting sections  20   a  and  20   b  formed in the rail-side guide grooves  16  so as to be slidable. Therefore, since the sliding sections  29  fit in the rail-side fitting sections  20   a  and  20   b  of the corresponding rail-side guide grooves  16 , each of the belt  24  and  25  move along the rail-side guide grooves  16  while movement (i.e., displacement) is restricted in the direction where the sidewall  42  faces hold the walls  44   a  and  44   b  (in particular, in the direction in which the rack teeth  26  approach the opposite face  42   a  of the sidewall  42 ). A plurality of metal wires W (in this embodiment, two) are embedded in each of the belt  24  and  25  so as to extend along a length of each of the belt  24  and  25 . Accordingly, the belts  24  and  25  have required strength while ensuring deformable flexibility. 
     Referring to  FIGS. 7 and 8 , a transfer structure will next be described for the first belt  24  at the boundary between the first guide groove  21   a  and the rail-side guide groove  16  of the left guide rail  13   b .  FIG. 7  is a cross-sectional view taken along the line  7 - 7  of  FIG. 1 .  FIG. 8  is a cross-sectional view taken along the line  8 - 8  of  FIG. 7 . 
     As shown in  FIG. 7 , formed in the rear end portion (i.e., the connection portion) of the first guide groove  21   a  connected to the left guide rail  13   b  is a lid  34 , which covers the first belt  24  all around, together with the sidewalls  32  and  33  and the bottom wall  31 . Formed in the lid  34  is a drive-side fitting section  34   a , to which the upper sliding section  29  fits so as to be slidable. The drive-side fitting section  34   a  is identical in shape to the above-mentioned drive-side fitting section  35   a  provided for the pressing section  35 . The drive-side fitting section  34   a  restricts the first belt  24  from moving (i.e., being displaced) together with the drive-side fitting section  31   a  in vertical or horizontal directions, in particular, in the direction in which the first and second sidewalls  32  and  33  face (i.e., in particular, in the direction where the rack teeth  26  approach the opposite face  32   a  of the first sidewall  32 ). Needless to say, these drive-side fitting sections  31   a  and  34   a  are connected to the rail-side fitting sections  20   a  and  20   b  of the left guide rail  13   b  in the directions of the front and back of the vehicle. Therefore, the first belt  24  guided by the first guide groove  21   a  and the rail-side guide groove  16  of the left guide rail  13   b  is securely transferred between the front housing  21  and the guide rail  13   b.    
     Additionally, as shown in  FIG. 8 , formed in the rear end portion (connection portion) of the first guide groove  21   a  is an inclined part  37 , which curves away from the first belt  24  as the inclined part  37  approaches the left guide rail  13   b  in the direction of the thickness of the first belt  24 . That is, clearance L between the rack teeth  26  of the first belt  24  and the opposite face  32   a  of the first sidewall  32  and clearance S between the rear face  28  of the first belt  24  and the internal face of the second sidewall  33  gradually increase as the inclined part  37  approaches the end of the left guide rail  13   b . The inclined part  37  is formed integrally with the first guide groove  21   a  so as to be line-symmetrical with respect to the axis of the first belt  24  in the direction in which the belt  24  extends. Incidentally, the drive-side fitting sections  31   a  and  34   a  are disposed so as to correspond to the end of the first guide groove  21   a  defining the maximum clearances L and S. Accordingly, the above-described movement (i.e., displacement) of the first belt  24  is restricted. In addition, the end of the first guide groove  21   a  and the end of the left guide rail  13   b  face each other with a slight gap  39  between them. 
     In order to smoothly transfer the first belt  24  between the first groove  21   a  and the rail-side guide groove  16  of the left guide rail  13   b , the first guide groove  21   a  and the rail-side fitting sections  20   a  and  20   b  of the left guide rail  13   b  need to be accurately aligned with the directions of the front and back of the vehicle. However, the front housing  21  is made of resin, making it difficult to ensure precision in shape. Therefore, when the first guide groove  21   a  is connected with the rail-side guide groove  16 , a step is highly likely to be formed between the opposite faces  42   a  and  32   a  due to assembly error or variations in manufacture therebetween. Such a problem occurs even in the same materials. Due to this step between the opposite faces  42   a  and  32   a , the first belt  24  may move (i.e., be displaced) in the direction of its thickness near the gap  39  between the first guide groove  21   a  and the rail-side guide groove  16 . However, even in such a case, a clearance L is ensured between the first belt  24  and the opposite face  32   a , thus preventing the rack teeth  26  of the first belt  24  from contacting the opposite face  32   a . Accordingly, noise can be reduced. The transfer structure described above is identical to that between the third guide groove  21   c  and the rail side guide groove  16  of the right guide rail  13   a . Therefore, explanation thereof is omitted. 
     In the foregoing configuration, when the drive gear  23  is rotated by driving the electric motor  22 , the first belt  24  and the second belt  25  move along the first to fourth guide grooves  21   a  to  21   d  (accurately, drive-side fitting section  31   a  and the like). Accordingly, the first belt  24  is restricted from moving in the direction of its thickness. Especially, the rack teeth  26  are prevented from contacting the first sidewall  32 . As described above, each of the guide grooves  21   a  to  21   d  is provided with the pressing sections  35 , disposed at intervals, and the lids  34 . The upper sliding sections  29  of the belts  24  and  25  are fitted in the drive-side fitting sections  35   a  and  34   a  of the pressing section and the lid portion  34  respectively. Thus, upward movement of the belts  24  and  25  relative to the corresponding guide grooves  21   a  to  21   d  is prevented. In addition, as described above, even if the belts  24  and  25  are moved in their respective thickness directions due to steps between the first and third guide grooves  21   a  and  21   c  and the rail-side guide groove  16  due to assembly error or suchlike, the clearance L is ensured between each of the belt  24  and  25 , and the first sidewall  32 . Accordingly, each of the belts  24  and  25 , and especially the rack teeth  26  are prevented from contacting the first sidewall  32 . This makes it possible to reduce vibration, noise, and the like during movement of the belts  24  and  25 . 
     The present embodiment has the advantages described below. 
     (1) A pair of sliding sections  29  of each of the belts  24  and  25  fit in corresponding drive-side fitting sections  31   a ,  35   a , and  34   a  or rail-side fitting sections  20   a  and  20   b  so as to be slidable. This restricts movement of the rack teeth  26  of each of the belt  24  and  25  toward the opposite face  42   a  of the guide groove  16  and the opposite face  32   a  of each of guide grooves  21   a  to  21   d . This makes it possible always to ensure that there is a clearance between the rack teeth  26  and the opposite faces  42   a  and  32   a  during movement of each of the belt  24  and  25 . Therefore, even if a step (e.g., a mold joints) is formed between the opposite faces  42   a  and  32   a  during the molding of, for example, sidewalls  42  and  32 , or if a notch is formed in the opposite faces  42   a  and  32   a , rack teeth  26  are prevented from contacting these steps or the like during movement of the belts  24  and  25 . In addition, when the belts  24  and  25  enter the corresponding rail-side guide grooves  16  from the corresponding first to fourth guide grooves  21   a  to  21   d , or when the belts  24  and  25  enter the corresponding first to fourth guide grooves  21   a  to  21   d  from the corresponding rail-side guide grooves  16 , each of the sidewall  42  and  32  and the rack teeth  26  are prevented from contacting each other at the end of the corresponding rail-side guide grooves  16  or at each of the first to fourth guide grooves  21   a  to  21   d . Hence, noise and vibration thus resulting can be reduced. 
     (2) In the belts  24  and  25 , movement of the rack teeth  26  toward the opposite face  42   a  in the groove  16  and the opposite face  32   a  in each of  21   a  to  21   d  is restricted. Thus, the required clearance can be ensured between the rack teeth  26  and the opposite face  42   a  of each guide groove  16  and the opposite face  32   a  of each of the guide grooves  21   a  to  21   d . Accordingly, even if a step forms between the opposite faces  42   a  and  32   a  at the boundary between each of the first to fourth guide grooves  21   a  to  21   d  and the corresponding rail-side guide grooves  16  due to, for example, variations in manufacture or assembly error, the step is absorbed in the range of the clearance. This makes it possible to prevent the rack teeth  26  from contacting each other during movement of each of the belts  24  and  25 . Hence noise and vibration due to the contact can be reduced. 
     (3) The inclined part  37  extends such that the clearance L between the opposite face  32   a  and the rack teeth  26  gradually increases toward the ends of the first and third guide grooves  21   a  and  21   c . Therefore, when the belts  24  and  25  enter the first guide groove  21   a  or the third guide groove  21   c  respectively from the corresponding rail-side guide groove  16 , contact between the sidewall  32  and rack teeth  26  at these ends is more reliably prevented. In addition, even if assembly error between the first guide groove  21   a  and rail-side guide groove  16  or variations in manufacture occur, the clearance L prevents contact between the sidewall  32  and the rack teeth  26 , thus facilitating precision of management of the alignment of the first guide groove  21   a  and the rail-side guide groove  16  to each other. 
     (4) In each of the belts  24  and  25 , the pair of sliding sections  29  formed on both sides of the belt in the widthwise direction of the belt fit in the drive-side fitting sections  31   a  and  35   a  or in the rail-side fitting sections  20   a  and  20   b . This enables the belts  24  and  25 , unconstrained by the shapes of the opposite faces  42   a  and  32   a  of the first to fourth guide grooves  21   a  to  21   d  or rail-side guide grooves  16  to the rack teeth  26 , to move more stably. In particular, in the area where the inclined part  37  is formed, as in other areas, movement of the belts  24  and  25  can be guided by virtue of the drive-side fitting sections  31   a  and  35   a.    
     (5) Each tooth of the drive gear  23  has the shape of a substantially truncated cone the diameter of which is smaller towards the top than towards the base. That is, the outside diameter of each tooth of the drive gear  23  gradually decreases towards the lower part from the higher part. Accordingly, each of the belts  24  and  25  can engage with the drive gear  23  such that the gap between them is always minimal. 
     The above embodiments may be modified as follows. 
     In the foregoing embodiment, the sliding sections  29  on both sides of the belt section  27  are in the direction of its width. However, the position and shape of the sliding sections  29  are not limited thereto. For example, as shown in  FIG. 9 , a sliding section  50  with a substantially T-shaped cross-section may be formed in the rear face  28  of the first belt  24  so as to extend along the length of the first belt  24 . In this case, a fitting groove  38  with a substantially T-shaped cross-section that fits on the sliding section  50  is formed in the first sidewall  32  along the path of each of the guide grooves  21   a  to  21   d . In addition, as shown in  FIG. 10 , a sliding section  51  with a substantially trapezoidal cross-section may be formed in the rear face  28  of the first belt  24  so as to extend along the length of the first belt  24 . In this case, a fitting groove  52  with a substantially trapezoidal cross-section that fits on the sliding section  29  is formed in the first sidewall  32  along the path of each of the guide grooves  21   a  to  21   d . This configuration enables the first belt  24  to be moved lengthways (i.e., in the direction of the sheet of the drawing of  FIGS. 9 and 10 ) while vertical or horizontal movement of the first belt  24  is restricted. For smooth transfer of the first belt  24  in the configuration in which a sliding section  29  is provided on the rear face  28  of the first belt  24  as described above, the inclined part  37  facing the rear face  28  of the first belt  24  should be omitted. 
     In the foregoing embodiment, the guide rails  13   a  and  13   b  are formed of aluminum, and the front housing  21  having the first to fourth guide grooves  21   a  and  21   d  is formed of resin. However, the materials for the guide rails  13   a  and  13   b  and the front housing  21  are not limited thereto. For example, all of them may be resin or metal. 
     In the foregoing embodiment, the inclined parts  37  are formed in the thickness directions of the belts  24  and  25 . However, each of these inclined parts  37  may be formed only at the point where at least each of the belt  24  and  25  faces the rack teeth  26 , and the inclined part  37  facing each rear face  28  may be omitted. 
     In the foregoing embodiment, a rib for reinforcing the guide grooves  21   a  to  21   d  and the like may be formed integrally on the front housing  21  (bottom wall  31 ). 
     The foregoing embodiment may adopt a front housing divided into two on both sides of the drive gear  23  in the widthwise direction of the vehicle. 
     In the foregoing embodiment, through holes  36  may be omitted. 
     In the foregoing embodiment, the belts  24  and  25  are held by the guide grooves  21   a  and  21   d . However, the embodiment is not limited thereto. A type in which each of the belts  24  and  25  is held in a casing pipe may also be applied in the present invention. Specifically, noise and the like, which may be caused by contact between the belts  24  and  25 , and the casing pipe, can be decreased by providing the inside of the casing pipe with fitting sections  31   a  and  35   a  or by providing the guide rails  13   a  and  13   b  with the inclined parts  37 . 
     DESCRIPTION OF THE REFERENCE NUMERALS 
     
         
           11  Roof 
           12  Opening 
           13   a  Right Guide Rail 
           13   b  Left Guide Rail 
           14  Operation Mechanism 
           15  Movable Panel 
           16  Rail-side Guide Groove 
           21  Front Housing (Housing) 
           20   a ,  20   b  Rail-side Fitting Section 
           21   a - 21   d  First to Fourth Guide Grooves (Guide Sections) 
           22  Electric Motor (Drive Source) 
           23  Drive Gear 
           24  First Belt 
           25  Second Belt 
           26  Rack Teeth 
           27  Rear Face 
           29 ,  50 ,  51  Slide portions 
           31  Bottom Wall 
           31   a ,  34   a ,  35   a  Drive-side Fitting Sections 
           32  First Sidewall 
           33  Second Sidewall 
           35  Pressing Section 
           35   a  Drive-Side Fitting Section 
           36  Through Hole