Abstract:
A power transmission system cover for an engine has a cover portion, formed of a single piece material and adapted to be attached to a sidewall of the engine, covering at least a part of a power transmission system which transmits a rotating force of a crankshaft to a camshaft. The cover portion is integrally provided with a passage forming portion defining a flow-passage in which a fluid element to be supplied to the engine flows, and an engine mount bracket located near the passage forming portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application incorporates by references the subject matter of Application No. 2003-193149 filed in Japan on Jul. 7, 2003 and Application No. 2003-203728 filed in Japan on Jul. 30, 2003, on which a priority claim is based under U.S.C § 119(a). 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a cover for a power transmission system that transmits a rotational force of a crankshaft of an engine to a camshaft. 
   2. Description of the Related Art 
   An engine has a bracket with which it is mounted in the body of an automobile. One such bracket is described in Jpn. UM Appln. KOKAI Publication No. 3-11923 (p. 5, 2–16; p. 6, 12–p. 7, 6; FIGS. 3 and 4). This bracket is fixed to a cylinder block with bolts. In attaching the bracket to the cylinder block, the bracket must be prevented from interfering with a belt for driving accessories, intake and exhaust pipes, a cooling water passage, etc., which are arranged around the cylinder block. To avoid the interference between the cooling water passage and the bracket, the passage is formed in the bracket. 
   In the engine constructed in this manner, however, the cooling water passage is passed through the bracket. In order to secure necessary strength for the bracket, therefore, the bracket must be large-sized. Since a joint (engaging hole, connector, etc.) for the connection of the cooling water passage requires machining, moreover, the shape of the bracket is intricate. Further, the cooling water passage is connected after the bracket is attached to the cylinder block, so that the flexibility of engine assembling means lowers. Thus, assembly work for the engine is complicated. 
   SUMMARY OF THE INVENTION 
   The present invention provides a power transmission system cover for engine, which is formed integrally with an engine mount bracket and has a sufficient stiffness for a basal part of the bracket. 
   A power transmission system cover for an engine according to this invention has a cover portion, a passage forming portion, and an engine mount bracket. The cover portion is located on a sidewall of an engine. The cover portion covers at least a part of a power transmission system which transmits a rotational force of a crankshaft to a camshaft. The passage forming portion projects from the cover portion and defines a flow-passage in which a fluid element to be supplied to the engine flows. The engine mount bracket is formed integrally with the cover portion and located near the passage forming portion. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The nature of this invention, as well as other objects and advantages thereof, will be explained in the following with reference to the accompanying drawing, in which like reference characters designate the same or similar parts throughout the figures and wherein: 
       FIG. 1  is a perspective view showing a power transmission system cover for engine according to an embodiment of the invention; 
       FIG. 2  is a perspective view of a lower chain case shown in  FIG. 1 , taken from another angle; 
       FIG. 3  is a front view of the lower chain case shown in  FIG. 1 ; 
       FIG. 4  is a sectional view of the lower chain case taken along line F 4 —F 4  of  FIG. 3 ; 
       FIG. 5  is a sectional view of the lower chain case taken along line F 5 —F 5  of  FIG. 3 ; 
       FIG. 6  is a sectional view of the lower chain case taken along line F 6 —F 6  of  FIG. 3 ; and 
       FIG. 7  is a sectional view of the lower chain case taken along line F 7 —F 7  of  FIG. 3 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A power transmission system cover for engine according to an embodiment of this invention will now be described with reference to  FIGS. 1 to 7 .  FIG. 1  typically shows a reciprocating engine  1  of an automobile. The engine  1  has an engine block  2 , a cylinder head cover  3 , a chain case  4 , and an oil pan  5 . 
   The engine block  2  includes a cylinder block  21  and a cylinder head  22 . The cylinder block  21  has a crankshaft  23 . The cylinder head  22  is mounted on the cylinder block  21 . The cylinder head  22  has a pair of camshafts  24 . The camshafts  24  are located parallel to the crankshaft  23  on the intake and exhaust sides, individually. As shown in  FIGS. 2 and 4 , a cooling water inlet  22   b  through which cooling water flows into the cylinder head  22  opens at a front wall  22   a  of the head. 
   In the present embodiment, the rotation axis of the crankshaft  23  extends along a longitudinal (front-back) direction of the engine. The side on which the chain case  4  is attached to the engine block  2  is the front side, which defines the transverse (left-right) direction. The vertical direction is the direction in which the cylinder block  21  and the cylinder head  22  are put on each other. The upper side is the side on which the cylinder head  22  is situated with respect to the cylinder block  21 . 
   On the other hand, the engine  1  is provided with a power transmission system  25 . The power transmission system  25  links the crankshaft  23 , which projects forward from the cylinder block  21 , to the camshafts  24 , which project forward from the cylinder head  22 . The power transmission system  25  has a crankshaft timing sprocket  25   a , camshaft timing sprockets  25   b , and a timing chain  25   c.    
   As shown in  FIG. 1 , the crankshaft timing sprocket  25   a  is fixedly fitted on the front end of the crankshaft  23 . The camshaft timing sprockets  25   b  are fixedly fitted on the respective front ends of camshafts  24 , individually. The timing chain  25   c  is passed around and between the timing sprockets  25   a  and  25   b . The timing chain  25   c  transmits a turning force of the crankshaft  23  to the camshafts  24 . The cylinder head cover  3  is mounted on the cylinder head  22 . 
   The chain case  4  is attached to the respective front walls of the engine block  2  and the cylinder head cover  3  and covers the power transmission system  25 . The chain case  4  is composed of a lower chain case  41  and an upper chain case  42 , for example. The lower chain case  41  covers a front wall  2   a  of the engine block  2 . The upper chain case  42  covers a front wall  3   a  of the cylinder head cover  3 . The lower chain case  41  is an example of a power transmission system cover for engine according to the present invention. 
   The lower chain case  41  has a lower front wall  43 , lower left-hand wall  44 , lower right-hand wall  45 , and a water pump mounting portion  34 . The lower front wall  43  is located in the direction across the rotation axis of the crankshaft  23 . The lower left- and right-hand walls  44  and  45  extend toward the engine block  2  from the left- and right-hand side edge portions, respectively, of the lower front wall  43  until they engage the front wall  2   a . The lower front wall  43 , lower left-hand wall  44 , and lower right-hand wall  45  form a cover portion according to the present invention. 
   As shown in  FIG. 2 , the water pump mounting portion  34  projects outward from the lower left-hand wall  44  lest it overlap the cylinder block  21 , along a line perpendicular to the axis of crankshaft  23 . 
   As shown in  FIGS. 3 and 5 , a plurality of bolt holes X are formed in the left-hand edge of the lower front wall  43  of the lower chain case  41 , ranging along the lower left-hand wall  44 . Likewise, bolt holes X are formed in the right-hand edge of the lower front wall  43 , ranging along the lower right-hand wall  45 . 
   As shown in  FIG. 1 , the upper chain case  42  has an upper front wall  42   a , upper left-hand wall  42   b , upper right-hand wall  42   c , and top wall  42   d . The upper chain case  42 , like the lower chain case  41 , is provided with a plurality of bolt holes on the left- and right-hand side edges of the upper front wall  42   a.    
   The lower and upper chain cases  41  and  42  are fastened to the engine block  2  and the cylinder head cover  3  with mounting bolts W, as shown in  FIG. 5 . The oil pan  5  is mounted covering both the respective lower surfaces of the lower chain case  41  and the cylinder block  21 , as shown in  FIG. 1 . 
   The lower chain case  41  is provided with a water pump  6 , cooling water passage  7 , projecting portions  8 , and engine mount bracket  9 . The water pump  6  is a centrifugal pump, which is provided on the side of the cylinder block  21 . The rotation axis of the water pump  6  is located in the water pump mounting portion  34  so that it is situated on the left of or outside a left-hand sidewall  35  of the cylinder block  21 . 
   A pulley coupling shaft  10  is in engagement with the front end of the crankshaft  23 . A crank pulley  11  is fixedly fitted on the front end of the pulley coupling shaft  10 . The rotational force of the crankshaft  23  is transmitted to a pump pulley  61  of the water pump  6  by a belt  12 . The crank pulley  11  may be designed to drive an alternator, air compressor, power steering pump, etc. (not shown), along with the water pump  6 , by means of the belt  12 . 
   As shown in  FIG. 4 , the water pump  6  has an impeller  101 , pump chamber  50 , pump shaft  100 , and bearing  51 . The impeller  101  applies centrifugal force to the cooling water to pressurize it. The Impeller  101  is housed in the pump chamber  50 . The pump shaft  100  serves as rotation axis for the impeller  101 . The bearing  51  supports the central part of the shaft  100 . 
   The pump chamber  50  is formed in the water pump mounting portion  34  of the lower chain case  41 . It communicates with an inlet port  53 . The inlet port  53  opens rearward behind the mounting portion  34  in the direction along the pump shaft  100 . The pump chamber  50  has a discharge port  55  that opens in the radial direction of a circle around the shaft  100 . The cooling water is discharged from the discharge port  55 . 
   The cooling water passage  7  extends from the discharge port  55  in the tangential direction of the downstream side of the rotation of the impeller  101 . In the present embodiment, the discharge port  55  is situated on the downstream side of the rotation of the impeller  101 , with respect to a line connecting the respective centers of the pump shaft  100  and the cooling water inlet  22   b . The bearing  51  is fitted in a bearing housing  59 . The bearing housing  59  is formed at an end portion of a passage forming member  73  on the side of the water pump mounting portion  34 . 
   The impeller  101  is fixed on one end of the pump shaft  100  that extends from the bearing  51  toward the pump chamber  50 . The pump pulley  61  is mounted on the other end of the pump shaft  100  that projects forward from the bearing housing  59 . A seal member  60  is provided between the pump chamber  50  and the bearing housing  59 . The seal member  60  prevents the cooling water in the chamber  50  from leaking out into the housing  59 . 
   A cooling water inlet passage  62  is connected to the inlet port  53 . The cooling water inlet passage  62  extends along axis of the crankshaft  23 . The cooling water inlet passage  62  is a pipe member, for example. The inlet passage  62  guides the cooling water into the water pump  6 . Thus, the pump shaft  100  is located outside the left-hand sidewall  35  of the cylinder block  21 . Likewise, the passage  62  is located outside the left-hand sidewall  35  of the cylinder block  21 , as shown in  FIG. 2 . 
   The cooling water passage  7  extends along the lower front wall  43  from the discharge port  55  of the water pump  6  to the cooling water inlet  22   b , and the cooling water flows through the passage  7 . In the present embodiment, the engine  1  is subjected to cylinder head pre-cooling. 
   As shown in  FIG. 4 , the cooling water passage  7  is formed on the region from pump chamber  50  to the cooling water inlet  22   b . The cooling water passage  7  is composed of first and second components  64  and  65 . The first component  64  is formed on the lower front wall  43  of the lower chain case  41 . The second component  65  is formed on the side of the passage forming member  73 . The passage forming member  73  is attached to the lower front wall  43  so as to cover the first component  64 , thereby forming the passage forming portion according to the present invention. 
   As shown in  FIG. 6 , the first component  64  is in the form of a groove that opens forward, extending from the pump chamber  50  to a position corresponding to the cooling water inlet  22   b . As shown in  FIG. 4 , the depth of the groove of the first component  64  is gradually reduced, along a direction T in which the cooling water from the discharge port  55  of the pump chamber  50  flows, to the position where the groove overlaps the front part of the engine block  2 . 
   The second component  65  is in the form of a groove that opens rearward. The depth of the groove of the second component  65  gradually increased, along the direction T in which the cooling water from the discharge port  55  of the pump chamber  50  flows, to the position where the groove overlaps the front part of the engine block  2 . 
   In the present embodiment, as shown in  FIG. 4 , the first and second components  64  and  65  are formed so that the flow sectional area of the cooling water passage  7  is fixed. That part of the passage  7  which is situated ahead of the engine block  2  extends parallel to the front wall  2   a  of the block  2  and reaches the passage outlet  71 . 
   Thus, the second component  65  bulges forward. In the position ahead of the engine block  2 , the flow sectional area of the cooling water passage  7  is wider on the side of the second component  65  than on the side of the first component  64 . Thus, the second component  65  on the side of the passage forming member  73  forms the major part of the cooling water passage  7 . 
   As shown in  FIG. 3 , the passage forming member  73  has a flange  73   a  that extends along the lower front wall  43 . The flange  73   a  has bolt holes Y. In  FIG. 7 , a rear end U of the some bolt holes Y are situated ahead of an edge portion  74  of the passage outlet  71  that reaches the cylinder head  22 . 
   The edge portion  74  of the passage outlet  71  is provided with a through hole V that communicates with the bolt holes Y and reaches the engine block  2 . Thus, the passage forming member  73  is fixed to the lower front wall  43  and the cylinder head  22  with mounting bolts W. 
   The location of the bolt holes Y is not limited to the positions ahead of the edge portion  74  of the passage outlet  71 . For example, the bolt holes Y may be located ahead of positions corresponding to stems that extend from the lower front wall  43  to the engine block  2 . The stems do not interfere the power transmission system  25 . In this case, the stems are provided with the through hole V. 
   As shown in  FIGS. 1 ,  3  and  5 , the projecting portions  8  are formed on the parts of the lower front wall  43 . The projecting portions  8  face the camshaft timing sprockets  25   b . The projecting portion  8  bulge forward. The sprockets  25   b  are housed inside the projecting portions  8 , individually. 
   As shown in  FIGS. 1 and 3 , the engine mount bracket  9  is formed in a region M on the front face of the lower front wall  43 . The region M is situated near and surrounded by the cooling water passage  7 , projecting portions  8 , and bolt holes X and Y. The engine mount bracket  9  is formed integrally with the lower front wall  43 . The bracket  9  is a solid structure that is formed integrally with the lower front wall  43  by sand casting, for example. A part of the bracket  9  bites one of the projecting portions  8 . 
   The engine mount bracket  9  extends obliquely downward toward the lower left-hand wall  44  along the lower front wall  43 . As shown in  FIGS. 1 and 6 , the bracket  9  extends forward and downward to a position P from the upper-left part of the wall  43 . Further, the bracket  9  forwardly extends substantially at perpendicular angles to wall  43  from the position P. The engine mount bracket  9  has a plurality of tapped holes Z. For better view of the bolt holes X and Y, the mounting bolts W are not shown in  FIG. 3 . 
   In the engine  1  constructed in this manner, the engine mount bracket  9  is formed near the cooling water passage  7 . The cooling water passage  7  bulges forward. More specifically, the sectional area of a basal part B (including a region near a boundary portion C between the lower front wall  43  and the bracket  9 ) of the bracket  9  that serves for the stiffness of the bracket is larger than that of the wall  43 . Thus, the passage  7  functions as a reinforcement rib, so that the stiffness of the basal part B of the engine mount bracket  9  is improved. Thus, the stiffness of the basal part of the engine mount bracket secured sufficient. 
   If the lower chain case  41  is formed by sand casting, for example, a separate reinforcement rib need not be provided to secure the stiffness of the basal part B of the engine mount bracket  9 . Therefore, the shape of a casting die for the lower chain case  41  is so simple that casting faults are lessened. Accordingly, the lower chain case  41  can be manufactured with improved efficiency and reduced in weight. Thus, the weight of the engine  1  can be reduced. Since the engine mount bracket  9  is not provided with the cooling water passage  7  inside, moreover, its shape can be simplified. In other words, the shape of the lower chain case  41  can be simplified. 
   The cooling water passage  7  is formed extending along the lower front wall  43  from the side of the cylinder block  21  to the side of the cylinder head  22 . Thus, the passage  7 , which has the effect of a reinforcement rib, is located covering a wide range over the chain case  4 , so that the stiffness of the case  4  is improved. Besides, the stiffness of the basal part B of the engine mount bracket  9  is improved further. In this case, the passage  7  has a flow sectional area large enough to allow the cooling water discharged from the water pump  6  to flow through it. This sectional area is larger than the flow sectional area of an oil passage  14 , which will be mentioned later. It is more effective, therefore, to form the bracket  9  near the cooling water passage  7 . 
   A part of the engine mount bracket  9  bites the projecting portion  8 . Since the projecting portion  8  bulges forward, the sectional area that serves for the stiffness of the basal part B of the bracket  9  is large. More specifically, the projecting portion  8  functions as a reinforcement rib, so that the basal part B of the bracket  9  is further improved in stiffness. Furthermore, the projecting portion  8  functions also as a reinforcement rib for the bracket  9 . Thus, the stiffness of the bracket  9  is improved additionally. 
   The engine mount bracket  9  is formed near the bolt holes X and Y. The bolt holes X and Y are formed within the thickness of the lower left-hand wall  44 , which extends to the engine block  2 , and the thickness of the edge portion  74 . Thus, the lower left-hand wall  44  and the edge portion  74  serve as reinforcement ribs, so that the stiffness of the basal part B of the bracket  9  is improved further. 
   The cooling water passage  7  is composed of the two components, the first component  64  on the lower front wall  43  of the lower chain case  41  and the second component  65  on the passage forming member  73 . With this arrangement, the lower chain case  41  can be divided into simple shapes. Thus, the lower front wall  43  and the passage forming member  73  can be fabricated with ease. 
   The shape of the casting die can be made particularly simple in the case where the lower chain case  41  and the passage forming member  73  are molded integrally with each other by casting. Therefore, casting faults are lessened, and the manufacturability is improved. Further, the dimensional accuracies of the case  41  and the member  73  are also improved. 
   The lower chain case  41  is provided with the water pump mounting portion  34 , and the pump shaft  100  of the water pump  6  is located in the mounting portion  34 . Therefore, the pump  6  can be situated rearward. Thus, the size of the engine  1  can be reduced with respect to the direction along the rotation axis of the crankshaft  23 . 
   The inlet port  53  of the water pump  6  opens rearward. Therefore, the cooling water inlet passage  62  that guides the cooling water into the inlet port  53  of the pump  6  need not extend in front of the engine block  2 . Thus, the engine size can be reduced with respect to the direction along the rotation axis of the crankshaft  23 . 
   The cooling water passage  7  is defined between the first component  64  on the lower chain case  41  and the second component  65  of the passage forming member  73 . The passage forming member  73  bulges forward. Accordingly, the effective sectional area of the lower front wall  43  of the case  41  that serves for the bending stiffness can be increased without thickening the lower front wall  43  of the case  41  or the passage forming member  73  or separately providing reinforcement ribs. Thus, the first and second components  64  and  65  that constitute the cooling water passage  7  function as reinforcing members, so that the stiffness of the lower chain case  41  can be enhanced. 
   The water pump  6  is located relatively close to the cylinder block  21 , and the cooling water inlet  22   b  is formed in the cylinder head  22 . Thus, the cooling water passage  7  is formed ranging from the cylinder block  21  side to the cylinder head  22  side. In consequence, the passage  7  can effectively serve as a reinforcing member for the lower chain case  41 . 
   The bearing housing  59  of the water pump  6  and the second component  65  are molded integrally with each other to form the passage forming member  73 . Therefore, the number of essential components of the lower chain case  41  is reduced, and leak paths of the cooling water lessen. 
   In the present embodiment, the water pump mounting portion  34  in which the water pump  6  is located projects on the left-hand side of the lower chain case  41  lest the inlet port  53  of the pump  6  overlap the engine block  2  in the longitudinal direction. Alternatively, however, the mounting portion  34  may be formed projecting in a position such that the inlet port  53  of the pump  6  never overlaps the engine block  2  in the longitudinal direction, e.g., on the right-hand side. 
   As shown in  FIG. 1 , the lower front wall  43  is provided with an oil filter  13  and the oil passage  14 . The filter  13  is attached to a filter bracket  13   a . The bracket  13   a  is integral with the lower chain case  41 . 
   The oil passage  14  is integral with the lower front wall  43 . Like the cooling water passage  7 , the oil passage  14  bulges forward. The passage  14  communicates with the oil filter  13  and the engine block  2  so that oil can flow from the filter  13  to the block  2 . 
   Since the cooling water passage  7  and the oil passage  14  serve as reinforcement ribs, as shown in  FIGS. 1 and 3 , a region N in which the passages  7  and  14  are located close to each other is highly stiff. Although the engine mount bracket  9  is formed in the region M according to the present embodiment, therefore, it may alternatively be formed in the region N. 
   In the present embodiment, the chain case  4  is composed of the upper and lower chain cases  42  and  41 , which are independent of each other. Alternatively, however, the chain cases  42  and  41  may be formed integrally with each other. 
   Although a chain drive system that uses a chain and sprockets is employed as the power transmission system that links the crankshaft to the camshafts, a belt drive system may be employed instead. The belt drive type uses a toothed belt and toothed pulleys in place of a chain and sprockets, respectively. Alternatively, a gear drive system may be employed. In the gear drive system, a crankshaft and camshafts are coupled by gears.