Patent Publication Number: US-9422046-B2

Title: Boat propulsion device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2013-248486, filed on Nov. 29, 2013. The entire disclosure of Japanese Patent Application No. 2013-248486 is hereby incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a boat propulsion device. 
     2. Description of the Related Art 
     A boat propulsion device has been well-known as being equipped with a resin cowling assembly composed of a top cowling and a bottom cowling, and a coupling mechanism for coupling the top cowling and the bottom cowling (see Japan Laid-open Patent Application Publication No. JP-A-H06-40392). The coupling mechanism includes a cam driven portion and a cam block. The cam driven portion is attached to the top cowling, whereas the cam block is attached to the bottom cowling. The bottom cowling includes an attachment block disposed on the inner surface thereof. The attachment block supports the cam block (therefore, the attachment block will be hereinafter referred to as “a support portion”). The support portion is composed of a plurality of plate-shaped members. The plate-shaped members are uniformly formed with a small thickness in order to entirely form a joint section of the support portion to be joined to the bottom cowling with a small thickness. Thus, it is possible to prevent dents attributed to molding shrinkage of the support portion from being produced in the bottom cowling by thinly forming the joint section joined to the bottom cowling. 
     However, when the support portion is entirely formed with a small thickness, a drawback is created in that the strength of the support portion itself is inevitably degraded. 
     SUMMARY OF THE INVENTION 
     Preferred embodiments of the present invention have been conceived in view of the situation described above. A preferred embodiment of the present invention provides a boat propulsion device that reliably achieves the strength required for a support portion configured to support a coupling mechanism of a cowling and to prevent dents attributed to molding shrinkage. 
     A boat propulsion device according to a preferred embodiment includes an engine including a crankshaft extending in an up-and-down direction and a cowling accommodating the engine. The cowling includes a first cowling portion made of resin, a second cowling, and a coupling mechanism configured to couple the first cowling portion to the second cowling portion. The coupling mechanism includes a first lock portion and a second lock portion. The first lock portion is attached to the first cowling portion. The second lock portion is attached to the second cowling portion and locks with the first lock portion. The first cowling portion includes a cowling main body and a support portion. The support portion preferably has a plate shape. The support portion is erected on an inner surface of the cowling main body. The support portion supports the first lock portion. The support portion includes a small thickness section and a large thickness section. The small thickness section is connected with the inner surface. The large thickness section includes an attachment surface to which the first lock portion is attached. The large thickness section is continuous with the small thickness section. A thickness of the large thickness section is greater than a thickness of the small thickness section in a direction perpendicular or substantially perpendicular to the attachment surface. 
     According to preferred embodiments of the present invention disclosed herein, it is possible to provide a boat propulsion device that reliably achieves the strength required for a support portion configured to support a coupling mechanism of a cowling and to prevent dents attributed to molding shrinkage. 
     The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a boat propulsion device according to a preferred embodiment of the present invention. 
         FIG. 2  is a perspective view of a support structure of a first coupling mechanism. 
         FIG. 3  is a side view of the support structure of the first coupling mechanism. 
         FIG. 4  is a perspective view of a support portion of a top cowling portion and the periphery thereof. 
         FIG. 5  is a cross-sectional view of  FIG. 4  taken along a line  5 - 5 . 
         FIG. 6  is a cross-sectional view of  FIG. 4  taken along a line  6 - 6 . 
         FIG. 7  is a plan view of the top cowling portion as seen from bottom. 
         FIG. 8A  is a diagram for explaining a method of forming a weld portion. 
         FIG. 8B  is a diagram for explaining a method of forming a weld portion. 
         FIG. 8C  is a diagram for explaining a method of forming a weld portion. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the attached drawings, explanation will be hereinafter made for a boat propulsion device according to preferred embodiments of the present invention.  FIG. 1  is a side view of a boat propulsion device  1  according to a preferred embodiment. The boat propulsion device  1  is preferably an outboard motor. The boat propulsion device  1  includes a cowling  2 , a casing  3 , a bracket  4 , and an engine unit  5 . 
     The cowling  2  accommodates the engine unit  5 . The cowling  2  includes a top cowling portion  21  preferably made of resin, a bottom cowling portion  22  preferably made of metal, a first coupling mechanism  23 , and a second coupling mechanism  24 . The top cowling portion  21  is disposed on the bottom cowling portion  22 . The top cowling portion  21  covers the top side and the lateral sides of the engine unit  5 . For example, thermoplastic resin is preferably used as the resin material of which the top cowling portion  21  is made. The bottom cowling portion  22  covers the bottom side of the engine unit  5 . A first recess  22   a  is provided in the rear end portion of the bottom cowling portion  22 , whereas a second recess  22   b  is provided in the front end portion of the bottom cowling portion  22 . For example, aluminum alloy or the like is preferably used as the metal material of which the bottom cowling portion  22  is made. 
     The first coupling mechanism  23  couples the rear end portion of the top cowling portion  21  and that of the bottom cowling portion  22 . The first coupling mechanism  23  includes a first lock lever  23   a . The first lock lever  23   a  is turnably attached to the bottom cowling portion  22 . When the first lock lever  23   a  is pushed into the first recess  22   a , the first coupling mechanism  23  is configured to couple the top cowling portion  21  and the bottom cowling portion  22 . By contrast, when the first lock lever  23   a  is pulled out of the first recess  22   a , coupling by the first coupling mechanism  23  is released. On the other hand, the second coupling mechanism  24  couples the front end portion of the top cowling portion  21  and that of the bottom cowling portion  22 . The second coupling mechanism  24  includes a second lock lever  24   a . The second lock lever  24   a  is turnably attached to the bottom cowling portion  22 . When the second lock lever  24   a  is pushed into the second recess  22   b , the second coupling mechanism  24  is configured to couple the top cowling portion  21  and the bottom cowling portion  22 . By contrast, when the second lock lever  24   a  is pulled out of the second recess  22   b , coupling by the second coupling mechanism  24  is released. It should be noted that explanation will be made below for the internal structures of the coupling mechanisms  23  and  24 . 
     The casing  3  is disposed under the cowling  2 . The boat propulsion device  1  is attached to a vessel body through the bracket  4 . The engine unit  5  is disposed within the cowling  2 . The engine unit  5  includes an engine  51 . A drive shaft  11  is disposed within the casing  3 . The drive shaft  11  extends within the casing  3  in the up-and-down direction. The drive shaft  11  is fixed to a crankshaft  51   a  extending within the engine  51  in the up-and-down direction. A propeller  12  is disposed in the lower portion of the casing  3 . The propeller  12  is disposed under the engine  51 . The propeller  12  includes a propeller boss  13 . A propeller shaft  14  is disposed inside the propeller boss  13 . The propeller shaft  14  is disposed along a back-and-forth direction. The propeller shaft  14  is coupled to the lower portion of the driveshaft  11  through a bevel gear  15 . 
     In the boat propulsion device  1 , a driving force generated by the engine  51  is transmitted to the propeller  12  through the drive shaft  11  and the propeller shaft  14 . The propeller  12  is thus configured to be forwardly or reversely rotated. As a result, this rotation generates thrust to forwardly or backwardly propel the vessel body to which the boat propulsion device  1  is attached. 
       FIG. 2  is a perspective view of a support structure of the first coupling mechanism  23 .  FIG. 3  is a side view of the support structure of the first coupling mechanism  23 . The support structure of the first coupling mechanism  23  and that of the second coupling mechanism  24  are preferably structurally identical to each other. Therefore, explanation will be hereinafter mainly made of the support structure of the first coupling mechanism  23 . 
     The top cowling portion  21  includes a top cowling main body  101 , a support portion  102 , a plurality of rib portions  103 , a first base portion  104 , a reinforcement portion  105 , a first side plate portion  106 , a first convex portion  107  and a rib portion  108 , a second base portion  109 , a second side plate portion  110 , and a second convex portion  111  and a rib portion  112 . 
     The top cowling main body  101  preferably has a cup shape. The top cowling main body  101  includes an inner surface  101 R. The support portion  102  is erected on the inner surface  101 R. The support portion  102  preferably has a plate shape. The support portion  102  is disposed along the horizontal or substantially horizontal direction. The support portion  102  includes an attachment surface  102 S and an opposite surface  102 T. The attachment surface  102 S and the opposite surface  102 T are respectively principal surfaces of the plate-shaped support portion  102 . The opposite surface  102 T is disposed on the opposite side of the attachment surface  102 S. The attachment surface  102 S is the bottom surface of the support portion  102 , whereas the opposite surface  102 T is the top surface of the support portion  102 . The plurality of rib portions  103  are erected on the inner surface  101 R. The rib portions  103  are connected to the opposite surface  102 T of the support portion  102 . The rib portions  103  preferably have a triangular plate shape, for example. The rib portions  103  are disposed along the up-and-down direction. The rib portions  103  prevent the support portion  102  from being deflected up and down. 
     The first base portion  104  is erected on the inner surface  101 R. The first base portion  104  is connected to the support portion  102  through the reinforcement portion  105  and the first side plate portion  106 . The first base portion  104  preferably has a box shape, for example. The reinforcement portion  105  is erected on the inner surface  101 R. The reinforcement portion  105  preferably has a plate shape. The reinforcement portion  105  is disposed along the horizontal or substantially horizontal direction so as to be continuous with the support portion  102 . A plurality of rib portions  105   a  are connected to the reinforcement portion  105 . The rib portions  105   a  are erected on the inner surface  101 R. The rib portions  105   a  are connected to the bottom surface of the reinforcement portion  105 . The rib portions  105   a  preferably have a triangular plate shape, for example. The rib portions  105   a  are disposed along the up-and-down direction. The rib portions  105   a  prevent the reinforcement portion  105  from being deflected up and down, while further preventing the support portion  102  from being deflected up and down. The first side plate portion  106  is erected on the inner surface  101 R. The first side plate portion  106  preferably has a plate shape. The first side plate portion  106  is disposed along the up-and-down direction so as to be continuous with the reinforcement portion  105  and the first base portion  104 . 
     The first convex portion  107  is attached to the first base portion  104 . The first convex portion  107  is disposed so as to downwardly protrude from the bottom surface of the first base portion  104 . The first convex portion  107  is preferably made of an elastic member (e.g., rubber). The rib portion  108  is erected on the inner surface  101 R. The rib portion  108  is connected to the top surface of the first base portion  104 . The rib portion  108  preferably has a triangular plate shape, for example. In a direction perpendicular to the inner surface  101 R, the height of the rib portion  108  is gradually reduced with an increasing distance from the first base portion  104 . In other words, the height of the upper end of the rib portion  108  is lower than that of the lower end of the rib portion  108  in the direction perpendicular to the inner surface  101 R. 
     The second base portion  109  is erected on the inner surface  101 R. The second base portion  109  is connected to the support portion  102  through the second side plate portion  110 . The second base portion  109  preferably has a box shape, for example. The second side plate portion  110  is erected on the inner surface  101 R. The second side plate portion  110  preferably has a plate shape. The second side plate portion is disposed along the up-and-down direction so as to be continuous with the support portion  102  and the second base portion  109 . 
     The second convex portion  111  is attached to the second base portion  109 . The second convex portion  111  is disposed so as to downwardly protrude from the bottom surface of the second base portion  109 . The second convex portion  111  is preferably made of an elastic member (e.g., rubber). The rib portion  112  is erected on the inner surface  101 R. The rib portion  112  is connected to the top surface of the second base portion  109 . The rib portion  112  preferably has a triangular plate shape, for example. In a direction perpendicular to the inner surface  101 R, the height of the rib portion  112  is gradually reduced with an increasing distance away from the second base portion  109 . In other words, the height of the upper end of the rib portion  108  is lower than that of the lower end of the rib portion  108  in the direction perpendicular to the inner surface  101 R. 
     The bottom cowling portion  22  includes a bottom cowling main body  201 , a first boss portion  202 , a second boss portion  203 , and a tubular portion  204 . The bottom cowling main body  201  preferably has a cup shape. The bottom cowling main body  201  includes an inner surface  201 R. The first boss portion  202  is erected on the inner surface  201 R. The first boss portion  202  includes a concave portion  202   a  recessed from the upper end surface thereof. The first convex portion  107  is preferably press-fitted, for example, to the concave portion  202   a . Accordingly, the first convex portion  107  is fixed to the first boss portion  202 . The second boss portion  203  is erected on the inner surface  201 R. The second boss portion  203  includes a concave portion  203   a  recessed from the upper end surface thereof. The second convex portion  111  is inserted into the concave portion  203   a . Accordingly, the second convex portion  111  is fixed to the second boss portion  203 . The tubular portion  204  is erected on the inner surface  201 R. The tubular portion  204  is disposed between the first boss portion  202  and the second boss portion  203 . 
     The first coupling mechanism  23  includes a first lock portion  150  and a second lock portion  250 . The first lock portion  150  is attached to the top cowling portion  21 . The second lock portion  250  is attached to the bottom cowling portion  22 . The first lock portion  150  is locked to the second lock portion  250 . 
     The first lock portion  150  includes a sheet metal portion  151 , a rotary portion  152 , a contact plate  153 , and a pair of bolts  154 . The sheet metal portion  151  is attached to the support portion  102  of the top cowling portion  21 . The upper end of the sheet metal portion  151  contacts the attachment surface  102 S of the support portion  102 . The sheet metal portion  151  is disposed along the inner surface  101 R of the top cowling main body  101 . The rotary portion  152  is rotatably attached to the sheet metal portion  151 . The axis of the rotary portion  152  extends in the horizontal or substantially horizontal direction. The contact plate  153  is attached to the support portion  102  of the top cowling portion  21 . The contact plate  153  preferably has a plate shape. The contact plate  153  is contacted to the opposite surface  102 T of the support portion  102 . The pair of bolts  154  secure the sheet metal portion  151  and the contact plate  153  together to the support portion  102 . 
     The second lock portion  250  includes a movable plate  251 , a shaft portion  252 , and an urging portion  253 . The movable plate  251  is disposed on the tubular portion  204  of the bottom cowling portion  22 . The movable plate  251  is supported by the shaft portion  252  so as to be rotatable along a horizontal plane. The shaft portion  252  is inserted through the tubular portion  204 . The lower end of the shaft portion  252  is fixed to the first lock lever  23   a  (see  FIG. 1 ). The shaft portion  252  is thus turned together with the first lock lever  23   a . When the first lock lever  23   a  is turned so as to be pushed into the first recess  22   a  (see  FIG. 1 ), the movable plate  251  is moved on the rotary portion  152  while being pressed onto the rotary portion  152 . The urging portion  253  urges the movable plate  251  so as to prevent the movable plate  251  from being unlocked from the rotary portion  152 . Thus, the first lock portion  150  is locked to the second lock portion  250 . 
       FIG. 4  is a perspective view of the support portion  102  of the top cowling portion  21  and the periphery thereof.  FIG. 4  illustrates a condition in which the first lock portion  150  and the second convex portion  111  are detached.  FIG. 5  is a cross-sectional view of  FIG. 4  taken along a line  5 - 5 .  FIG. 6  is a cross-sectional view of  FIG. 4  taken along a line  6 - 6 . 
     As illustrated in  FIG. 4 , the support portion  102  includes a small thickness section  102   a  and a large thickness section  102   b . The small thickness section  102   a  is erected on the inner surface  101 R of the top cowling main body  101 . In other words, the small thickness section  102   a  is directly connected with the inner surface  101 R. The small thickness section  102   a  preferably has a thin plate shape. The large thickness section  102   b  is continuous with the small thickness section  102   a . The large thickness section  102   b  is preferably integral with the small thickness section  102   a . The large thickness section  102   b  directly supports the sheet metal portion  151  of the first lock portion  150 . In other words, the large thickness section  102   b  defines the attachment surface  102 S to which the sheet metal portion  151  contacts. The large thickness section  102   b  includes a pair of insertion-through holes  102   d  through which the pair of bolts  154  are inserted. The large thickness section  102   b  includes a plurality of ribs  102   c . The ribs  102   c  are erected on the inner surface  101 R. The ribs  102   c  are directly connected with the inner surface  101 R. 
     As illustrated in  FIG. 5 , the thickness (Tb) of the large thickness section  102   b  is greater than the thickness (Ta) of the small thickness section  102   a  in a direction perpendicular to the attachment surface  102 S (hereinafter referred to as “a vertical direction”). Thus, in the support portion  102 , a section to be joined to the top cowling main body  101  is thin, whereas a section that supports the first lock portion  150  is thick. The thickness Ta of the small thickness section  102   a  is preferably arbitrarily set as long as the small thickness section  102   a  can support the large thickness section  102   b  while dents attributed to molding shrinkage is unlikely to be produced in the top cowling main body  101 . The thickness Tb of the large thickness section  102   b  is preferably arbitrarily set as long as the large thickness section  102   b  supports the first lock portion  150 . 
     As illustrated in  FIG. 6 , the ribs  102   c  are integral with the top cowling main body  101 , the small thickness section  102   a , and the large thickness section  102   b , respectively. The ribs  102   c  are provided on the opposite side of the rib portions  103  through the small thickness section  102   a . However, the arrangement of the ribs  102   c  is preferably arbitrarily designed. In the vertical direction, the thickness Tb of the large thickness section  102   b  is approximately equal to the sum of the thickness Ta of the small thickness section  102   a  and the thickness (Tc) of the respective ribs  102   c . It should be noted that the thickness Tc of the respective ribs  102   c  is preferably arbitrarily set. Further, the ribs  102   c  may protrude or be recessed from the large thickness section  102   b.    
     It should be noted that, as illustrated in  FIG. 4 , the top cowling portion  21  includes a pair of rib portions  113 . The rib portions  113  are erected on the inner surface  101 R. The rib portions  113  are preferably integral with the top cowling main body  101 . The rib portions  113  are disposed between the top cowling main body  101  and the sheet metal portion  151  (see  FIG. 2 ). The rib portions  113  are preferably spaced away from the sheet metal portion  151 . In other words, a clearance is provided between the rib portions  113  and the sheet metal portion  151 . When locking the first lock portion  150  to the second lock portion  250 , the sheet metal portion  151  contacts the rib portions  113  when the support portion  102  is downwardly deflected. 
     On the other hand, similarly to the support portion  102 , the second base portion  109  includes a small thickness section  109   a , a large thickness section  109   b , and ribs  109   c  as illustrated in  FIG. 4 . The small thickness section  109   a , the large thickness section  109   b , and the ribs  109   c  are preferably structurally similar to the small thickness section  102   a , the large thickness section  102   b , and the ribs  102   c  of the support portion  102 . 
     Explanation will be hereinafter made for an air duct configured to introduce intake air to be supplied to the engine  51 . 
       FIG. 7  is a plan view of the top cowling portion  21  as seen from the bottom. The top cowling portion  21  includes an air duct portion  114 . An air duct is arranged between the air duct portion  114  and the inner surface  101 R. External air is introduced to the engine  51  through the air duct arranged between the top cowling main body  101  and the air duct portion  114 . 
     The air duct portion  114  is connected to the top cowling main body  101  at first to third screwed portions  115   a  to  115   c  and first to fourth welded portions  116   a  to  116   d . The air duct portion  114  is screwed to the top cowling main body  101  at the first to third screwed portions  115   a  to  115   c . On the other hand, the air duct portion  114  is welded (so-called, heat-staked) to the top cowling main body  101  at the first to fourth welded portions  116   a  to  116   d.    
       FIGS. 8A to 8C  are diagrams for explaining a method of forming each of the first to fourth welded portions  116   a  to  116   d.    
     As illustrated in  FIG. 8A , plate-shaped fixing portions  117  are erected on the inner surface  101 R of the top cowling main body  101 . The thickness of the respective fixing portions  117  is preferably arbitrarily set as long as a dents attributed to molding shrinkage is unlikely to be produced in the top cowling main body  101 . Each fixing portion  117  includes a lower section  117   a  and an upper section  117   b . The lower section  117   a  is directly connected with the inner surface  101 R. The upper section  117   b  is disposed on the lower section  117   a . The upper section  117   b  is tapered such that the width thereof is gradually reduced with an increasing distance away from the inner surface  101 R. Each fixing portion  117  is supported by a pair of rib portions  118  from both sides thereof. The rib portions  118  preferably have a plate shape and are erected on the inner surface  101 R. The rib portions  118  are connected to the lower section  117   a  of the fixing portion  117 . The thickness of the respective rib portions  118  is preferably arbitrarily set as long as dents attributed to molding shrinkage are unlikely to be produced in the top cowling main body  101 . The air duct portion  114  includes insertion holes  114   a  in which the fixing portions  117  are respectively inserted. 
     Firstly, as illustrated in  FIG. 8B , the upper section  117   b  of each fixing portion  117  is inserted into the corresponding insertion hole  114   a  of the air duct portion  114 . The upper section  117   b  is herein tapered, and therefore, the upper section  117   b  is easily inserted into the insertion hole  114   a.    
     Next, as illustrated in  FIG. 8C , each fixing portion  117  is welded to the corresponding insertion hole  114   a  by melting the upper section  117   b  by heat. Accordingly, the air duct portion  114  is fixed to the respective fixing portions  117 . The first to fourth welded portions  116   a  to  116   d  preferably are respectively formed by the method described above. 
     The boat propulsion device  1  according to the present preferred embodiment preferably includes the following features. 
     The top cowling portion  21  (an exemplary first cowling portion) includes the top cowling main body  101  (an exemplary cowling main body) and the support portion  102 . The support portion  102  is erected on the inner surface  101 R of the top cowling main body  101 , and supports the first lock portion  150 . The support portion  102  includes the small thickness section  102   a  and the large thickness section  102   b . The small thickness section  102   a  is connected with the inner surface  101 R. The large thickness section  102   b  is continuous with the small thickness section  102   a . The large thickness section  102   b  includes the attachment surface  102 S to which the first lock portion  150  is attached. The thickness Tb of the large thickness section  102   b  is greater than the thickness Ta of the small thickness section  102   a  in the direction perpendicular to the attachment surface  102 S. Thus, in the support portion  102 , a section to be joined to the top cowling main body  101  is thin. It is thus possible to prevent dents attributed to molding shrinkage from being produced in the top cowling main body  101 . On the other hand, in the support portion  102 , a section configured to support the first lock portion  150  is thick. It is thus possible to enhance the strength of the large thickness section  102   b  configured to support the first lock portion  150 . 
     The large thickness section  102   b  includes the ribs  102   c  (exemplary first ribs) connected with the inner surface  101 R. Therefore, it is possible to enhance the strength of the small thickness section  102   a  configured to support the large thickness section  102   b.    
     The top cowling portion  21  includes the rib portions  113  (exemplary second ribs). The rib portions  113  are erected on the inner surface  101 R, while being disposed between the top cowling main body  101  and the sheet metal portion  151 . Therefore, when locking the first lock portion  150  to the second lock portion  250 , the sheet metal portion  151  contacts the pair of rib portions  113  when the support portion  102  is downwardly deflected. Deflection of the support portion  102  is thus reduced. Thus, the sheet metal portion  151  and the rotary portion  152  of the first lock portion  150  are prevented from moving with respect to the movable plate  251 . As a result, the first lock portion  150  is reliably locked to the second lock portion  250 . 
     The top cowling portion  21  includes the first base portion  104 , the reinforcement portion  105 , and the first convex portion  107 . The first convex portion  107  is preferably press-fitted to the first boss portion  202  of the bottom cowling portion  22  (an exemplary second cowling portion). The first convex portion  107  is attached to the first base portion  104 . The reinforcement portion  105  is coupled to the support portion  102  and the first base portion  104 . Therefore, the support portion  102  is securely supported by the reinforcement portion  105 . Deflection of the support portion  102  is thus reduced when locking the first lock portion  150  to the second lock portion  250 . Thus, the sheet metal portion  151  and the rotary portion  152  of the first lock portion  150  are prevented from moving with respect to the movable plate  251 . As a result, the first lock portion  150  is reliably locked to the second lock portion  250 . 
     The top cowling portion  21  includes the rib portion  108  (an exemplary third rib) extending from the first base portion  104  to the opposite side of the first convex portion  107 . The height of the rib portion  108  is gradually reduced with an increasing distance away from the first base portion  104 . Therefore, the first base portion  104  is more securely supported by the rib portion  108 , while it is possible to prevent a harness and electric components contained in the engine unit  5  from getting stuck with the rib portion  108 . 
     The top cowling portion  21  includes the fixing portions  117  to which the air duct portion  114  is fixed. The fixing portions  117  are erected on the inner surface  101 R, and preferably have a plate shape. Therefore, the fixing portions  117  are easily provided with a small thickness. It is thus possible to further prevent dents attributed to molding shrinkage from being produced in the top cowling main body  101 . 
     The fixing portions  117  are welded to the insertion holes  114   a  of the air duct portion  114 . Therefore, the air duct portion  114  is easily, conveniently and securely connected to the fixing portions  117 . 
     The top cowling portion  21  includes the rib portions  118  (exemplary fourth ribs) to be coupled to the fixing portions  117 . The rib portions  118  are erected on the inner surface  101 R, and preferably have a plate shape. Therefore, the rib portions  118  are provided with a small thickness. It is thus possible to further prevent dents attributed to molding shrinkage from being produced in the top cowling main body  101 . 
     Preferred embodiments of the present invention have been explained above. However, the present invention is not limited to the preferred embodiments described above. A variety of changes may be herein made without departing from the scope of the present invention. 
     In the preferred embodiments described above, the top cowling portion  21  is preferably made of resin, whereas the bottom cowling portion  22  is preferably made of metal. However, the material of the top cowling portion  21  and that of the bottom cowling portion  22  are not limited to the above. Any suitable material or materials may be used as long as at least either of the top cowling portion  21  and the bottom cowling portion  22  is made of resin. When the bottom cowling portion  22  is made of resin, it is required to define the support portion  102  in the bottom cowling portion  22  and attach the first lock portion  150  to the support portion  102  whereas it is required to attach the second lock portion  250  to the top cowling portion  21 . 
     In the preferred embodiments described above, the support portion  102  is preferably disposed along the horizontal or substantially horizontal direction. However, the support portion  102  may be slanted with respect to the horizontal direction. 
     In the preferred embodiments described above, a variety of ribs are preferably provided. However, these ribs may not be provided. 
     In the preferred embodiments described above, the term “locked” means a condition that a first member and a second member are interlocked or fixed with each other. Therefore, the shape of the first lock portion  150  and that of the second lock portion  250  are not limited to those illustrated in the drawings. The first lock portion  150  and the second lock portion  250  may be arbitrarily shaped as long as the first lock portion  150  may be locked to the second lock portion  250 . 
     In the preferred embodiments described above, the term “urged” means either a condition that a first member is pressed onto a second member or a condition that the first member is pulled toward the second member. Therefore, the shape of the urging portion  253  is not limited to that illustrated in the drawings. An arbitrary member may be used as the urging portion  253 , as long as such a member is configured to press or pull the movable plate  251  in order to prevent the movable plate  251  from being unlocked from the rotary portion  152 . 
     In the preferred embodiments described above, the term “contacted” means a condition that a first member directly makes contact with a second member. Therefore, the shape of the contact plate  153  is not limited to that illustrated in the drawings. The contact plate  153  may be arbitrarily shaped as long as it directly contacts the opposite surface  102 T of the support portion  102 . 
     In the preferred embodiments described above, the expression “erected” means a condition that a first member, having a plate or rod shape, is mounted and/or raised on the outer surface of a second member. Therefore, the shape of the small thickness section  102   a  is not limited to that illustrated in the drawings. The small thickness section  102   a  may be arbitrarily shaped as long as it is raised on the inner surface  101 R. 
     In the preferred embodiments described above, the term “rotated” means a condition that a first member is configured to freely move about a predetermined axis with respect to a second member. Therefore, the shape of the rotary portion  152  is not limited to that illustrated in the drawings. The rotary portion  152  may be arbitrarily shaped as long as it is configured to freely move about a predetermined axis with respect to the sheet metal portion  151 . 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.