Abstract:
A cover structure for an internal combustion engine covers and protects a coolant pipe of a cooling system component on an internal combustion engine, even when the internal combustion engine only has a short distance provided between a crankshaft and an output shaft. The cover structure includes an outer cover disposed outside an inner cover, thereby defining a space between the first and outer covers. Coolant conduits, which are in fluid communication with a cooling system component, are constructed and arranged to pass through the space between the first and outer covers.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present invention claims priority under 35 USC § 119 based on Japanese patent application No. 2006-230952, filed on Aug. 28, 2006. The subject matter of this priority document is incorporated by reference herein. 
   BACKGROUND OF THE INVENTION 
   1. Technical Field of the Invention 
   The present invention relates to a cover structure of an internal combustion engine. More particularly, the present invention relates to a cover structure for a coolant pipe of a cooling device of an internal combustion engine, which is mounted on a motorcycle. 
   2. Background Art 
   In the field of cover structures for internal combustion engines, there is known a cover structure in which a water pump and a protective cover, which covers and protects a coolant pipe in communication with a cooling system of the internal combustion engine, are integrally mounted on a sprocket wheel cover, which covers a drive sprocket wheel connected to an output shaft of the internal combustion engine, for example, in Japanese patent document JP-UM-B-7-55291. 
   Further, in order to decrease the size of an internal combustion engine, there is known an internal combustion engine in which a distance between a crankshaft and an output shaft is shortened. In such an internal combustion engine, a drive sprocket wheel, which is connected to the output shaft, and a coolant pipe of a cooling device are overlapped in the width direction of the vehicle. However, with such an internal combustion engine, it is difficult to cover and protect the coolant pipe using the protective cover described above in patent document 1. 
   The present invention has been made in view of the above situation, and an object of the present invention is to provide a cover for an internal combustion engine which can cover and protect a coolant pipe of a cooling device of an internal combustion engine even when the internal combustion engine is an internal combustion engine which has a short distance between a crankshaft and an output shaft. 
   SUMMARY OF THE INVENTION 
   To achieve the above-mentioned object, according to a first aspect of the invention, a cover structure of an internal combustion engine is provided, which includes: an inner cover arranged to cover a portion of a drive force transmission mechanism, which is connected to an output shaft of an internal combustion engine, and a cooling device for cooling the internal combustion engine; an outer cover arranged outside the inner cover; and a coolant pipe of the cooling device which passes through a space defined between the inner cover and the outer cover. 
   In a second aspect of the invention, the throttle management apparatus for an internal combustion engine according to the first aspect of the invention is further characterized in that the outer cover is mounted on the internal combustion engine by insertion and fitting the outer cover into fitting openings formed in the inner cover and the internal combustion engine. 
   In a third aspect of the invention, the throttle management apparatus for an internal combustion engine according to the first aspect of the invention is further characterized in that a lower portion of the outer cover is provided with a guide portion which guides a hose having one end portion thereof exposed to the outside air and an opening which is communicated with the guide portion. 
   According to the first aspect of the invention, the outer cover is arranged outside the inner cover, and the coolant pipe of the cooling device passes through the space defined between the inner cover and the outer cover. Therefore, even when the internal combustion engine is an internal combustion engine which has a short distance between a crankshaft and an output shaft, it is possible to cover and protect the coolant pipe of the cooling device of the internal combustion engine. Further, the coolant pipe is protectively covered by the outer cover, thereby enhancing the appearance of the internal combustion engine. Still further, the radiation sounds from the internal combustion engine can be reduced due to the first and outer covers thereby enhancing the tranquility of the internal combustion engine. 
   According to the second aspect of the invention, it is possible to mount the outer cover on the internal combustion engine by inserting and fitting the outer cover into fitting openings formed in the inner cover and the internal combustion engine, thereby easing the assembly of the outer cover. 
   According to the third aspect of the present invention, the lower portion of the outer cover is provided with a guide portion, for supportively guiding a hose having an end portion exposed to the environment outside the cover, and an opening which is in communication with the guide portion. With such an arrangement, it is unnecessary to additionally fix the hose using a clamp or the like, thus reducing the number of parts required. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of an internal combustion engine incorporating a cover structure according to a selected illustrative embodiment of the present invention. 
       FIG. 2  is a side view of the internal combustion engine of  FIG. 1 , with an outer cover removed from the internal combustion engine. 
       FIG. 3  is a side view of an inner cover which is a component of the engine of  FIG. 2 . 
       FIG. 4  is a cross-sectional view of the inner cover, taken along a line indicated by an arrow A-A in  FIG. 3 . 
       FIG. 5  is a side view of an outer cover which is a component of the engine of  FIG. 1 . 
       FIG. 6  is an end view of the outer cover, from a vantage point indicated by the arrow B in  FIG. 5 . 
       FIG. 7  is another side view of the outer cover, from a vantage point indicated by the arrow C in  FIG. 6 , and opposite to the vantage point of  FIG. 5 . 
   

   DETAILED DESCRIPTION 
   A selected illustrative embodiment of the invention will now be described in some detail, with reference to the drawings. Note that, in the following, the drawings are viewed in the same direction as numerals. It should be understood that only structures considered necessary for clarifying the present invention are described herein. Other conventional structures, and those of ancillary and auxiliary components of the system, are assumed to be known and understood by those skilled in the art. 
   First, as shown in  FIG. 1 , an internal combustion engine  10  includes a crankcase  11  which incorporates a transmission (not shown), a cylinder block  12  which is integrally formed on an upper front portion of the crankcase  11 , a cylinder head  13  which is fixed to an upper end portion of the cylinder block  12 , and a cylinder head cover  14  which closes an opening formed in an upper end portion of the cylinder head  13 . The engine  10  also includes a generator G operatively attached to the crankcase  11 , a generator cover  15  which closes an opening formed in a left-side surface of the crankcase  11 , a cooling device  20  for cooling the internal combustion engine  10 , and a crankshaft  11   a . The generator G is operated in a known manner via rotation of the crankshaft  11   a.    
   On the left-side surface of the crankcase  11 , an output shaft  16  of the transmission (not shown) is mounted so as to projecting from the crankcase  11 , and a drive sprocket wheel  17 , which is part of the drive force transmission mechanism, is connected to the output shaft  16 . Further, a drive chain  17   a , which is also part of the drive force transmission mechanism, is wound around the drive sprocket wheel  17 . 
   The cooling device  20  includes: a water pump  21  arranged below the drive sprocket wheel  17  of the crankcase  11 , an oil cooler  22  arranged on a front end surface of the crankcase  11 , a thermostat valve  23  arranged on an upper end portion of the crankcase  11 , a water jacket (not shown) formed in the inside of the cylinder block  12  and the cylinder head  13 , and a radiator (not shown) arranged in front of the internal combustion engine  10 . The water pump  21 , the oil cooler  22 , the thermostat valve  23 , the water jacket (not shown), and the radiator (not shown) are in communication with each other by way of respective coolant pipes  24 ,  25 ,  26 ,  27 . The coolant pipes  24 ,  25 ,  26  and  27  may be made from rubber, reinforced elastomeric tubing, or similar material. 
   In the internal combustion engine  10  of the depicted embodiment, the water pump  21  of the cooling device  20  is arranged below the drive sprocket wheel  17 , thereby shortening the distance between the crankshaft  11   a  and the output shaft  16  as compared to a conventional internal combustion engine. 
   Further, in the depicted embodiment, as shown in  FIG. 1  and  FIG. 2 , the coolant pipes  24 ,  25  of the cooling device  20  are protectively covered by a cover structure  30 . The cover structure  30  includes a sprocket wheel cover  31  fixed to a left-side surface of the crankcase  11 . The sprocket wheel cover  31  is also referred to as an inner cover  31  herein, and is arranged to cover the drive sprocket wheel  17 . The cover structure  30  also includes a coolant pipe cover  32 , which is also referred to herein as an outer cover  32 . The outer cover  32  is mounted on the outer surfaces of the inner cover  31  and the generator cover  15 , and which is arranged outside the inner cover  31 . 
   The outer cover  32  and the inner cover  31  cooperate to define a predetermined distance therebetween. This predetermined distance between the inner cover  31  and the outer cover  32  allows for the coolant pipes  24 ,  25  of the cooling device  20  to vertically pass through the space defined between the inner cover  31  and the outer cover  32 . By passing the coolant pipes  24 ,  25  through the space defined by the inner cover  31  and the outer cover  32 , the coolant pipes  24 ,  25  are protectively covered by the outer cover  32 . 
   As shown in  FIG. 3  and  FIG. 4 , the inner cover  31  is formed as a generally plate-shaped member having a modified substantially trapezoidal shape, as viewed from a side view. A pair of fixing members  33 , each having a respective bolt insertion hole  33   a  formed therein, are integrally cast on upper and lower edge portions, respectively, of the inner cover  31 . The inner cover  31  is fixed to the crankcase  11  by fastening the fixing members  33 ,  33  to the left-side surface of the crankcase  11  using fasteners, for example bolts (see  FIG. 2 ). 
   Two fitting projections  34  are formed on an outer surface of the inner cover  31 . Mounting holes  34   a  are formed in outer end surfaces of the fitting projections  34 . Rubber or elastomeric grommets  35 , having fitting holes  35   a  therein to receive projections  37  of the outer cover  32  (described below), are inserted into the fitting projections  34 . Reinforcing ribs  36  are also cast in to the inner cover  31 , to increase the strength and rigidity thereof. 
   As shown in  FIG. 2 , a plate-like mounting stay  15   a  is formed on a rear portion of the generator cover  15 , and the mounting stay  15   a  has a mounting hole formed therein. A rubber or elastomeric grommet  35 , having a fitting hole  35   a  therein, is inserted into the mounting hole of the mounting stay  15   a , and is provided to engagingly receive a projection  37  of the coolant pipe  32  (described later). 
   As shown in  FIG. 5  to  FIG. 7 , the outer cover  32  is formed as a generally plate-shaped member having a substantially trapezoidal shape as viewed from a side view, and the projections  37  (which are inserted into the fitting holes  35   a ) are formed on an inner surface of the outer cover  32 , at positions corresponding to the fitting holes  35   a  formed in the grommets  35  of the inner cover  31  and the generator cover  15 . The outer cover  32  is mounted on the inner cover  31  and the generator cover  15  by respectively inserting and fitting the projections  37  into the fitting holes  35   a  formed in the grommets  35  of the inner cover  31  and the generator cover  15 . The outer cover  32  is formed into an approximately L-shape, when viewed in a plan view, for forming a space defined between the inner cover  31  and the outer cover  32 . The space defined between the inner cover  31  and the coolant pipe cover allows the coolant pipes  24 ,  25  to pass through the defined space. A front edge of the outer cover  32  is formed into an arcuate shape along an outer peripheral surface of the generator cover  15 . 
   On a lower end portion of the outer cover  32 , an inclined portion  32   a  is inwardly and downwardly inclined is formed. The inclined portion  32   a  is provided with a guide portion  38 , which guides a large-diameter breather hose  18  (a hose having one end portion thereof exposed to the outside air) and a small-diameter breather hose  19  (a hose having one end thereof exposed to the outside air), and an opening  39 . The opening  29  is in communication with the guide portion  38 . The guide portion  38  arranges the large-diameter breather hose  18  above the opening  39  and arranges the small-diameter hose  19  below the opening  39  in parallel (see  FIG. 1 ). Examples of different uses for the breather hoses  18 ,  19  include a breather hose which discharges a blowby gas inside of the internal combustion engine  10 , a breather hose which discharges fuel vapor inside of a fuel tank (not shown in the drawing), and a breather hose in a reserve tank of the cooling device  20 . 
   In the cover structure  30  of the internal combustion engine  10  having the above-mentioned formation, by inserting the projections  37  of the outer cover  32  into the fitting holes  35   a  formed in the grommets  35  of the inner cover  31  and the generator cover  15 , the outer cover  32  is mounted on the inner cover  31  and the generator cover  15 , and is arranged outside the inner cover  31 . Accordingly, a space is formed between the inner cover  31  and the outer cover  32 . By allowing the coolant pipes  24 ,  25  to pass through the space, the coolant pipes  24 ,  25  are protectively covered by the outer cover  32 . Further, the rubber or elastomeric grommets  35  are arranged between the inner cover  31  and the outer cover  32  and between the generator cover  15  and the outer cover  32  and hence, vibrations of the respective covers  15 ,  31 ,  32  can be reduced. 
   As explained above, according to the cover structure  30  of the internal combustion engine  10  of the depicted embodiment, the outer cover  32  is arranged outside the inner cover  31 , and the coolant pipes  24 ,  25  of the cooling device  20  are made to pass through the space defined between the inner cover  31  and the outer cover  32 . According to such an arrangement, even when the internal combustion engine  10  is an internal combustion engine in which the distance between the crankshaft  11   a  and the output shaft  16  is shortened, it is possible to cover and protect the coolant pipes  24 ,  25  of the cooling device  20  of the internal combustion engine  10 . Further, the coolant pipes  24 ,  25  are protectively covered by the coolant pipe cover, thereby enhancing the appearance of the internal combustion engine  10 . Still further, by using two different covers, e.g. the outer cover  32  and the inner cover  31 , it is possible to reduce radiation sounds of the internal combustion engine  10  thereby enhancing the tranquility of the internal combustion engine  10 . Moreover, by arranging the coolant pipes  24 ,  25  outside of the drive sprocket wheel  17 , the radiation sounds of the internal combustion engine  10  can be further reduced. 
   Further, according to the cover structure  30  of the internal combustion engine  10  of the depicted embodiment, the outer cover  32  is mounted on the inner cover  31  and the internal combustion engine  10  by inserting the outer cover  32  into the fitting holes  35   a  formed in the inner cover  31  thereby making it easier to assemble the cover structure  30 . Additionally, since the outer cover  32  is mounted on the inner cover  31  such that the outer cover  32  is astride to the inner cover  31 , the cooling pipe cover  32  is more firmly mounted on the inner cover  31 . Also, by the depicted embodiment, a load which is applied to the inner cover  31  can be reduced thereby reducing the weight of the inner cover  31  while ensuring the rigidity of the inner cover  31 . 
   According to the cover structure  30  of the internal combustion engine  10  of the depicted embodiment, the lower end portion of the outer cover  32  is provided with the guide portion  38 , which guides the hoses  18 ,  19 , each having one end portion exposed to the outside air, and the opening  39 , which is in communication with the guide portion  38 , it is unnecessary to additionally fix the hoses  18 ,  19  using a clamp or the like thereby reducing the number of parts. Further, the opening  39  is formed in the inclined portion  32   a  of the outer cover  32  and thereby making the opening  39  inconspicuous from the outside. Still further, the guide portion  38  allows the large-diameter hose  18  to be arranged above the opening  39  and the small-diameter hose  19  to be arranged below the opening  39  thereby preventing the small-diameter hose  19  from being exposed to the outside when viewed in a side view and enhancing appearance of the internal combustion engine  10 . 
   While a working example of the present invention has been described above, the present invention is not limited to the working example described above, but various design alterations may be carried out without departing from the present invention as set forth in the claims.