Abstract:
A structure of removably mounting a tower connecting bar between top surfaces of right and left strut towers by bolts and nuts. The tower connecting bar has a pipe and annular circular plates attached to opposite ends of the pipe. The circular plates are mounted to the top surfaces of the towers by the bolts and nuts. Upper ends of suspension struts are fastened to the top surfaces of the towers by bolts and nuts. The circular plates have through holes for allowing the strut-mounting nuts to escape when the towers and circular plates are mated together. The through holes provide access to loosen the strut-mounting nuts.

Description:
This application claims the foreign priority of Japanese Application Serial No. JP 2004-227099, filed on Aug. 3, 2004, and is incorporated by reference into this application. 
   FIELD OF THE INVENTION 
   The present invention relates to a tower connecting bar structure in which the upper ends of right and left suspension struts are connected to mounting portions on the vehicle body side. 
   BACKGROUND OF THE INVENTION 
   A structure in which the ends of a rod are mounted to right and left body portions, respectively, in an automobile engine compartment is proposed in Japanese Utility Model Laid-Open Publication No. HEI-4-9267, for example. A structure in which top surfaces of right and left suspension towers are connected by a rod is proposed in Japanese Utility Model Laid-Open Publication No. SHO-62-100270, for example. 
   A performance rod mounting structure proposed in HEI-4-9267 will be described with reference to  FIG. 12 ; a performance rod mounting structure proposed in SHO-62-100270 will be described with reference to  FIG. 13 . 
   A performance rod  101  shown in  FIG. 12  is mounted in an engine compartment E. A first end  102  of the rod  101  is supported by a body portion  103  via a horizontal bolt  104 . A second end  105  is supported by a body portion  107  via a vertical bolt  106 . When the vertical bolt  106  is pulled out of a bracket  108 , the rod  101  becomes rotatable about the horizontal bolt  104  as shown by arrow R. This provides enough space in the engine compartment E for maintenance of parts disposed in the engine compartment E. 
   A performance rod  131  shown in  FIG. 13  is connected to right and left suspension towers  133  (only one shown) of a vehicle  132 . An end of the performance rod  131  is welded to a plate or sheet bracket  135  abutting a top surface  134  of the suspension tower  133 . The plate bracket  135  has a through hole  136  and three mounting holes. The plate bracket  135  is fastened to the top surface  134  together with a suspension damper D. This prevents the top surface  134  of the suspension tower  133  from being deformed when it is subjected to vibration forces from the suspension damper D. 
   However, since the first and second ends  102  and  105  of the performance rod  101  shown in  FIG. 12  are mounted in positions apart from upper ends  111 ,  111  of a suspension, loads applied from the suspension are hardly transmitted to the performance rod  101  via the body portions  103  and  107 . Thus, the performance rod  101  cannot efficiently receive the loads. 
   The performance rod  131  shown in  FIG. 13  effectively supports a load applied to the suspension damper D. However, when nuts are loosened to remove the performance rod  131  for inspection and maintenance, the suspension damper D is also disengaged from the suspension tower  133 , resulting in time-consuming inspection and maintenance. On the other hand, when the suspension damper D is disengaged, the performance rod  131  is also disengaged, resulting in time-consuming inspection and maintenance. 
   Further, since the plate bracket  135  is placed on the top surface  134  of the suspension tower  133  and fastened together as shown in  FIG. 13 , factors affecting axial forces (e.g., contact conditions such as an area size and a clearance size) are increased and are likely to increase variations in axial force. Furthermore, when a load acts on the plate bracket  135 , a connection portion  137  to the performance rod  131  is likely to deform. 
   There is thus demand for a tower connecting bar structure which efficiently receive loads from suspension struts, reduces variations in axial force when upper ends of the suspension struts are fastened, and saves time in mounting and removing. 
   SUMMARY OF THE INVENTION 
   According to the present invention, there is provided a tower connecting bar structure for connecting right and left strut towers on which bolts and nuts for suspension fastening are exposed, which comprises: a tower connecting bar comprising a pair of right and left doughnut-shaped circular plates, and a pipe which connects the circular plates; the circular plates including a plurality of bolt holes formed to be used for fastening the circular plates to the strut towers, and a plurality of nut accommodating or escaping holes formed greater in diameter than the outside diameter of the nuts. 
   As described above, the tower connecting bar in this invention comprises the pair of right and left doughnut-shaped circular plates and the pipe which connects the circular plates, and the circular plates are formed with the nut accommodating holes having a diameter greater than the outside diameter of the suspension-fastening nuts as well as the bolt holes used for fastening the circular plates to the strut towers. There is an advantage that the bolt holes for fastening the circular plates can thus be used for directly mounting the tower connecting bar to the strut towers to allow it to efficiently receive loads from suspension struts. When the circular plates are mounted to the strut towers, the suspension-fastening nuts are accommodated in the nut accommodating holes. There is an advantage that the surface pressures of the suspension—fastening nuts can be directly applied to the strut towers, reducing variations in axial force when the upper ends of the suspension struts are fastened. 
   The circular plates are formed with the nut accommodating holes as well as the bolt holes used for fastening the circular plates to the strut towers. Therefore, when the circular-plate-mounting nuts are loosened to remove the tower connecting bar for inspection and maintenance, for example, the suspension struts are not disengaged from the strut towers. This saves time in mounting and removing the tower connecting bar. 
   The bolt holes formed in one of the right and left circular plates are circular holes, and the bolt holes formed in the other circular plate are transversely elongated holes. The elongated holes can absorb pitch variations between the right-hand and left-hand bolts used for fastening the circular plates, preventing interference between the circular-plate bolts and the bolt holes. 
   Substantially triangular reinforcing brackets are placed on connection portions between the pipe and the circular plates, and the reinforcing brackets are formed with tool holes through which to pass a nut fastening tool. The reinforcing brackets can thus increase the strength (section modulus) of the connection portions between the pipe and the circular plates to efficiently receive forces from the suspension struts of a suspension. 
   The pipe is provided with branch pipes attached to its middle. The branch pipes have distal ends mountable to a cowl below a windshield. When forces from the suspension struts are applied to the strut towers, the branch pipes can transmit the forces to the cowl, increasing the strength of the tower connecting bar, and resultantly increasing the strengths of the strut towers. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A preferred embodiment of the present invention will be described in detail below, by way of example only, with reference to the accompanying drawings, in which: 
       FIG. 1  is a schematic plan view of a tower connecting bar structure according to the present invention; 
       FIG. 2  is a perspective view illustrating the connection between a right bracket and a pipe, as viewed in the direction of arrow  2  of  FIG. 1 ; 
       FIG. 3  is a perspective view illustrating the connection between a left bracket and a pipe, as viewed in the direction of arrow  3  of  FIG. 1 ; 
       FIG. 4  is a perspective view illustrating the connection between a connection portion of the right bracket and the pipe, as viewed in the direction of arrow  4  of  FIG. 3 ; 
       FIG. 5  is a cross-sectional view taken along line  5 - 5  of  FIG. 3   
       FIG. 6  is a view taken in the direction of arrow  6  of  FIG. 3 ; 
       FIG. 7  is a cross-sectional view taken along line  7 - 7  of  FIG. 3   
       FIG. 8  is a plan view of a tower connecting bar according to the present invention, mounted to right and left strut towers; 
       FIG. 9  is a perspective view illustrating mounting of the left bracket to the strut tower; 
       FIG. 10  is a diagram illustrating how loads applied to the right and left suspension struts are transmitted through branch pipes to a cowl; 
       FIG. 11  is a diagram illustrating how a load applied to the suspension strut is transmitted to the tower connecting bar; 
       FIG. 12  is a diagram of a related-art performance rod mounting structure; and 
       FIG. 13  is a diagram of another related-art performance rod mounting structure. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   In the description of an embodiment with reference to the drawings, “front,” “rear,” “right,” “left,” “above” and “below” shown in the drawings are directions seen from a driver. 
   A tower connecting bar  11  shown in  FIG. 1  includes a pipe  13  extending transversely of a vehicle  12 , annular brackets  14  and  15  fixed to opposite ends of the pipe  13 , and branch pipes  17  attached to the middle  16  of the pipe  13 . 
   The branch pipes  17  include a pair of right and left pipe bodies  21 ,  21  attached symmetrically with respect to the middle  16  of the pipe  13 . The right and left pipe bodies  21 ,  21  have distal ends  22 ,  22  formed with a plurality of holes  25  for mounting to a cowl  24  below a windshield. 
   The bracket  14  has a doughnut-shaped circular plate  26  to which a substantially triangular reinforcing bracket  27  is attached. Reference numerals  28 ,  28  denote connection portions between the pipe  13  and the circular plates  26 . 
   Although the tower connecting bar  11  herein includes the branch pipes  17  and the reinforcing brackets  27 , it is possible to eliminate the branch pipes  17  and the reinforcing brackets  27 . That is, the tower connecting bar  11  may consist of the pair of right and left doughnut-shaped circular plates  26  and the pipe  13  connecting the circular plates  26 . 
   The right bracket  15  has main components similar to the bracket  14 . 
     FIG. 2  shows the right bracket  15  of the tower connecting bar  11 . 
   The bracket  15  has the doughnut-shaped circular plate  26  to which the reinforcing bracket  27  is attached, as already described. 
   The right circular plate  26  includes a fitting portion  32  conformed to an outer surface  31  of the pipe  13 , into which the pipe  13  is fitted, and a fastening plate portion  33  formed continuously with the fitting portion  32 . 
   The fastening plate portion  33  has in its center a strut hole  36  in which an upper end  35  (see  FIG. 8 ) of a suspension strut  34  (see  FIG. 10 ) is disposed, three bolt holes  37  and three nut accommodating or escaping holes  41  formed around the periphery of the strut hole  36 , and ribs  42  and  43  formed at the inner and outer peripheries of the fastening plate portion  33 . 
   The bolt holes  37  are transversely elongated. 
   The diameter Dh of the nut accommodating holes  41  is greater than the outside diameter Dn (see  FIG. 9 ) of suspension-fastening nuts  44  (see  FIG. 9 ) (Dh&gt;Dn). 
   The reinforcing bracket  27  includes a first reinforcing portion  45  conformed to the outer surface  31  of the pipe  13  and fitted to the fitting portion  32  of the circular plate  26 , and a second reinforcing portion  46  formed continuously with the first reinforcing portion  45 . The second reinforcing portion  46  includes a rib  47  formed at a circular arc portion at its distal middle portion, ribs  48  formed at its opposite sides, and ribs  49 ,  49  formed at its distal end portions on both sides of the circular arc portion. 
   The second reinforcing portion  46  of the reinforcing bracket  27  is formed with tool holes  51  and  52  through which to pass a nut fastening tool (not shown). 
     FIG. 3  shows the left bracket  14  shown in  FIG. 1 . 
   The bracket  14  includes, as already described, the doughnut-shaped circular plate  26  and the reinforcing bracket  27  attached to the circular plate  26 . 
   The left circular plate  26  includes a fitting portion  32  conformed to the outer surface  31  of the pipe  13  and fitted onto the pipe  13 , and a fastening plate portion  33  formed continuously with the fitting portion  32 . 
   The fastening plate portion  33  includes in its center a strut hole  36  in which an upper end  35  (see  FIG. 8 ) of a suspension strut  34  (see  FIG. 10 ) is disposed, three bolt holes  53  and three nut accommodating holes  41  formed around the periphery of the strut hole  36 , and ribs  42  and  43  formed at the inner and outer peripheries of the fastening plate portion  33 . 
   The bolt holes  53  are circular holes with the diameter set at Dk. 
   The reinforcing bracket  27  includes a first reinforcing portion  45  conformed to the outer surface  31  of the pipe  13  and fitted to the fitting portion  32  of the circular plate  26 , and a second reinforcing portion  46  formed continuously with the first reinforcing portion  45 . The second reinforcing portion  46  includes a rib  47  formed at a circular arc portion at its distal middle portion, ribs  48  formed at its opposite sides, and ribs  49 ,  49  formed at its distal end portions on both sides of the circular arc portion. 
   The second reinforcing portion  46  of the reinforcing bracket  27  is formed with tool holes  51  and  52  through which to pass a nut fastening tool (not shown). 
   The tower connecting bar  11  is a combination of the pipe  13 , the doughnut-shaped circular plates  26  and the reinforcing brackets  27  which are integrated by welding. The doughnut-shaped circular plates  26  are attached to the outer surface  31  of the pipe  13  at welds (such as beads)  54 ,  54  (see  FIG. 4 ). The reinforcing brackets  27  are attached to the outer surface  31  of the pipe  13  at welds  55 ,  55 . The reinforcing brackets  27  are also attached to the doughnut-shaped circular plates  26  at welds  56 ,  57  and  58 . 
   Specifically, each reinforcing bracket  27  includes at the first reinforcing portion  45  grooves  61 ,  61  formed in the direction of the central axis  62  of the pipe  13 . A weld (such as a bead)  55  is applied to each beveled portion  61  for weld length Lw 1  to increase the strength of the weld  55 . The strength is especially increased against a load generally orthogonal to the central axis  62  (in the direction of arrow f 1 ), resulting in an increased strength of the reinforcing bracket  27 . 
     FIG. 4  shows the left bracket  14  viewed from the bottom. 
   The circular plate  26  includes grooves  63 ,  63  formed at the fitting portion  32  over length L 1  in the direction of the central axis  62  of the pipe  13 . As a result, welds (such as beads)  54  can be applied to the grooves  63 ,  63  for weld length Lw 2  to increase the strength of the welds  54 . The strength can be especially increased against a load generally orthogonal to the central axis  62  (in the direction of arrow f 2 ), resulting in an increased strength of the circular plate  26 . 
   The bracket  14  has the ribs  48  of the reinforcing bracket  27  attached to the rib  43  at the outer periphery of the doughnut-shaped circular plate  26  by a plurality of welds  56  of fillet welds, and thus can be welded in a constant weld position during welding, resulting in easy and time-saving welding. 
     FIG. 5  shows a cross section of the pipe  13 , a cross section of the fitting portion  32  of the circular plate  26 , and a cross section of the first reinforcing portion  45  of the reinforcing bracket  27 . 
   The pipe  13  has an elliptical cross-sectional shape. The pipe  13  is disposed with a short-diameter portion  64  formed with a short diameter oriented vertically. Thus, the height of the pipe  13  is low, ensuring a clearance between the pipe  13  and a hood (not shown). 
     FIG. 6  shows one end portion of the reinforcing bracket  27  shown in  FIG. 3 . 
   The reinforcing bracket  27  has the rib  49  at that end portion. The rib  49  has an abutting portion  66 . The abutting portion  66  abuts on the top surface of the fastening plate portion  33  of the circular plate  26 . 
   The abutting portion  66  of the reinforcing bracket  27  can distribute a load applied to the circular plate  26  in an upward direction (direction of arrow a 1 ), reducing the surface pressure on the rib  49 , and resultantly reinforcing the circular plate  26  more securely. 
     FIG. 7  shows a cross section of a part of the annular bracket  14  shown in  FIG. 3 . 
   The bracket  14  has a structure in which the ribs  47  and  48  formed at the edge of the second reinforcing portion  46  of the reinforcing bracket  27  are integrally joined to the ribs  42  and  43  formed at the inner and outer peripheries of the circular plate  26  at the welds  56  and  57 . This can increase the strength (section modulus) of the circular plate  26 . 
   As shown in  FIG. 8 , the tower connecting bar  11  is assembled by mounting the left and right brackets  14  and  15  by a plurality of bolts  74  and nuts  75  to top plate portions  73 ,  73  of the right and left strut towers  72 ,  72  provided on the vehicle body  71  side. 
   The upper ends  35 ,  35  of the right and left suspension struts  34 ,  34  are previously mounted to the top plate portions  73 ,  73  of the strut towers  72 ,  72  by a plurality of suspension-fastening bolts  76  (see  FIG. 9 ) and nuts  44  (see  FIG. 9 ). 
   Since the brackets  14  and  15  (circular plates  26 ) are thus mounted to the top plate portions  73 ,  73  of the strut towers  72 ,  72 , the top plate portions  73 ,  73  of the strut towers  72 ,  72  can be directly supported to efficiently receive loads F (see  FIG. 10 ) from the suspension struts  34 ,  34 . 
     FIG. 9  shows mounting of the tower connecting bar  11  to the strut tower  72 . 
   The upper end  35  of the suspension strut  34  is previously fastened to the top plate portion  73  of the strut tower  72  by the bolts  76  and nuts  44 . Thus, the circular plate  26  of the tower connecting bar  11  does not intervene between the nuts  44  and the top plate portion  73 , and the surface pressures of the nuts  44  can be applied only to the top plate portion  73 . 
   More specifically, the circular plate  26  is formed with the nut accommodating holes  41  of a diameter (diameter Dh) greater than the outside diameter Dn of the nuts  44 , in addition to the bolt holes  53  or the bolt holes  37  of elongated holes (see  FIG. 2 ) used for fastening the circular plate  26  to the strut tower  72 . Consequently, the circular plate  26  of the tower connecting bar  11  does not intervene between the nuts  44  and the top plate portion  73 , which can reduce variations in axial force applied to the bolts  76  for fastening the upper end  35  of the suspension strut  34  to the top plate portion  73 . 
   Next, the mounting procedure of the tower connecting bar  11  will be described. 
   First, the suspension strut  34  is fastened to the top plate portion  73  of the strut tower  72 . Then, the three bolts  74  previously fixed by welding to the top plate portion  73  of the strut tower  72  are inserted through the three bolt holes  53  formed in the circular plate  26 , respectively, as shown by arrows a 2 , as well as the three nuts  44  being inserted through the three nut accommodating holes  41 , respectively, as shown by arrows a 3 . 
   Subsequently, the right three bolts  74  are inserted through the three bolt holes  37  of elongated holes (see  FIG. 2 ) formed in the right circular plate  26 , respectively, as shown by arrow a 4  (see  FIG. 2 ), as well as the three nuts  44  being inserted through the three nut accommodating holes  41 , respectively, as shown by arrows a 3 . 
   In this procedure, the use of the elongated holes  37  can absorb variations in pitch (e.g., pitch P 1  shown in  FIG. 8 ) between the bolts  74  welded to the top plate portions  73 . Subsequently, the right and left nuts  75  are screwed onto the bolts  74 , respectively, to fasten the right and left circular plates  26  to the top plate portions  73  of the right and left strut towers  72 . 
   As shown in  FIG. 9 , the circular plate  26  is formed with the nut accommodating holes  41  in addition to the bolt holes  53  or the bolt holes  37  of elongated holes (see  FIG. 2 ), and the top plate portion  73  of the strut tower  72  is formed with the bolts  74  for circular plate mounting. Therefore, when the right and left nuts  75  are loosened to remove the tower connecting bar  11  for inspection and maintenance, for example, the suspension struts  34  (see  FIG. 10 ) are not disengaged from the top plate portions  73  of the strut towers  72 . On the other hand, when the nuts  44  are loosened to remove the suspension struts  34 , the tower connecting bar  11  is not disengaged from the top plate portions  73  of the strut towers  72 . This saves time in mounting and removing the tower connecting bar  11 . 
   As shown in  FIG. 9 , the reinforcing bracket  27  is formed with the tool hole  51  through which to pass a nut fastening tool, so that the nut  75  on the circular plate  26  on which the reinforcing bracket  27  is placed can be rotated by the nut fastening tool. 
   Also, since the reinforcing bracket  27  is formed with the tool hole  52  through which to pass a nut fastening tool, the nut  44  for the suspension strut  34  (see  FIG. 10 ) can be loosened without loosening the nuts  75  for the tower connecting bar  11 . 
   This saves time in mounting and removing the tower connecting bar  11  or the suspension struts  34  (see  FIG. 10 ). 
   Finally, as shown in  FIG. 10 , the distal ends  22 ,  22  of the branch pipes  17  attached to the pipe  13  are fixed to the cowl  24  below the windshield by bolts  77 ,  77 . This completes the mounting of the tower connecting bar  11 . 
   As described above, since the pipe  13  is provided with the branch pipes  17  attached to the middle  16 , and the distal ends  22  of the branch pipes  17  are attached to the cowl  24  below the windshield, when loads F, F through the suspension struts  34 ,  34  are applied to the top plate portions  73 ,  73  of the strut towers  72 ,  72  of the vehicle body  71 , the branch pipes  17  transmit the forces to the cowl  24  as shown by arrows a 5 , a 5 , increasing the strength of the tower connecting bar  11 , and resultantly increasing the strengths of the strut towers  72 ,  72  of the vehicle body  71 . 
   As shown in  FIG. 11 , when the load F through the suspension strut  34  is applied to the top plate portion  73  of the strut tower  72  of the vehicle body  71 , the load is applied to the doughnut-shaped circular plate  26  of the bracket  14  as shown by arrows a 6 , and also transmitted from the circular plate  26  to the reinforcing bracket  27  as shown by arrows a 7 , a 7 , resulting in an increased strength of the bracket  14  (reduced stress). 
   Specifically, the tower connecting bar  11  has the substantially triangular reinforcing bracket  27  placed on the connection portion  28  between the pipe  13  and the circular plate  26  to increase the strength (section modulus) of the bracket  14  (circular plate  26 ) and to significantly reduce deflection produced in the connection portion  28  between the pipe  13  and the circular plate  26 , and thus can efficiently receive the load F from the suspension strut  34 . 
   The tower connecting bar structure of the present invention is applicable to three-wheeled vehicles as well as four-wheeled vehicles. 
   Obviously, various minor changes and modifications of the present invention are possible in the light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.