Abstract:
An engine includes a case member, a guide member disposed so as to make contact with an endless transmission belt, one end section of the guide member being swingably supported on the case member and the other end section of the guide member a free end, and a chain tensioner for pressing the free end of the guide member to apply tension to the endless transmission belt. The chain tensioner includes an accommodating concave section disposed in the case member, wherein an outer side of the accommodating concave section in a direction parallel to the axis of rotation of the drive shaft has an opening section, and also includes an elastic member being accommodated in the accommodating concave section to press the guide member and a lid member covering the opening section of the accommodating concave section in the direction of the axis of rotation of the drive shaft.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an engine mounted on a vehicle, such as a utility vehicle. 
     2. Description of the Prior Art 
     In engines mounted on various vehicles, such as a utility vehicle, a mechanism is provided in which an endless transmission belt, such as a chain, is stretched between a drive sprocket for a crankshaft journaled on a crankcase and a driven sprocket secured to driven shafts, such as a camshaft and a pump drive shaft, journaled on the crankcase, and the power of the crankshaft is transmitted to the driven shafts, such as the camshaft and the pump drive shaft. 
       FIG. 7  shows an outline of a winding power transmission unit  200  in which a conventional chain  206  is used. In  FIG. 7 , the chain  206  is stretched between a drive sprocket  202  secured to a crankshaft and a driven sprocket  204  secured to a pump shaft. When the drive sprocket  202  is rotated counterclockwise as shown in the figure, the upper section  206   a  of the chain  206  is stretched and becomes a tension side, and the lower section  206   b  is released and becomes a loose side. 
     The winding power transmission unit  200  shown in  FIG. 7  is equipped with a chain guide  208  for applying tension to the lower section  206   b  (loose side) of the chain  206 . One end section  208   a  of the chain guide  208  is swingably supported on the wall section  211  of the crankcase  210  in the vicinity of the lower section of the driven sprocket  204 , and the other end section  208   b  of the chain guide  208  becomes a free end. The chain guide  208  extends along the lower section  206   b  on the loose side. Furthermore, a chain tensioner  220  is disposed below the other end section  208   b  of the chain guide  208 , and the pressing piece  224  of the chain tensioner  220  presses the other end section  208   b  of the chain guide  208  toward the lower section  206   b  of the chain  206 . 
     The chain tensioner  220  shown in  FIG. 7  is equipped with a nearly cylindrical housing  222 , the pressing piece  224  slidably loaded inside the housing  222 , and a coil spring  226  for biasing the pressing piece  224  toward the lower section  206   b  of the chain  206 . The housing  222  of the chain tensioner  220  shown in  FIG. 7  has a flange section  232 , has a male screw section  234  above the flange section  232  and has a hexagon bolt-shaped head section  228  below the flange section  232 . Furthermore, in the wall section  211  of the crankcase  210 , a female screw hole  214  screw-engaged with the male screw section  234  of the flange section  232  is formed. The chain tensioner  220  shown in  FIG. 7  is screwed to the wall section  211  of the crankcase  210  via an O-ring  230  disposed between the flange section  232  of the housing  222  and the wall section  211  of the crankcase  210 . 
     The chain tensioner  220  according to the conventional technology shown in  FIG. 7  is equipped with a plurality of components, such as the pressing piece  224 , and requires the O-ring  230  for allowing the chain tensioner  220  to be installed in the wall section  211  of the crankcase  210  in a hermetically sealed state, whereby the number of components is large and the cost is raised. Furthermore, it is necessary to form a machined seat for allowing the chain tensioner  220  to be screwed to the wall section  211  of the crankcase  210  while ensuring hermetic sealing inside the crankcase  210 . In other words, it is necessary to form the male screw section  234  of the flange section, to form the female screw hole  214  in the wall section  211  of the crankcase  210  and to form a flat section for allowing the O-ring  230  to perform sealing. Hence, there are problems, such as cost increase due to increase in processing man-hour and high susceptibility to design restrictions. 
     In addition, a guide mechanism in which a plurality of guide units for guiding the traveling of a ring-shaped belt stretched between at least two rotation shafts while applying tension to the ring-shaped belt are connected mutually in a swingable state is disclosed as another conventional example in Japanese Patent Application Laid-open Publication No. 2002-89636. 
     The guide mechanism disclosed in Japanese Patent Application Laid-open Publication No. 2002-89636 requires a connection structure for connecting the plurality of guide units. Hence, there are problems that the overall structure of the guide mechanism becomes large and it becomes difficult to securely obtain sufficient installation space for the guide mechanism and that the installation of the guide mechanism is complicated. 
     SUMMARY OF THE INVENTION 
     Accordingly, the technical problem to be solved by the present invention is to provide an engine equipped with a chain tensioner having a small number of components, being capable of reducing cost and having a simple mounting structure. 
     MEANS FOR SOLVING PROBLEM 
     For the purpose of solving the above-mentioned technical problem, the present invention provides an engine equipped with a drive rotation member secured to a drive shaft journaled on a case member; a driven rotation member secured to a driven shaft journaled on the case member; an endless transmission belt wound between the drive rotation member and the driven rotation member; a guide member disposed so as to make contact with the endless transmission belt, one end section of which is swingably supported on the case member and the other end section of which is a free end; and a chain tensioner for pressing the free end of the guide member to apply tension to the endless transmission belt, wherein the chain tensioner has an accommodating concave section disposed in the case member and having an opening section on the outside in the direction of the drive shaft; an elastic member passing through the opening section and being accommodated in the accommodating concave section to press the guide member toward the endless transmission belt; and a lid member for covering the opening section of the accommodating concave section. 
     With the above-mentioned configuration, since the elastic member directly presses the guide member, the number of components and the processing man-hour relating to the pressing structure can be reduced. More specifically, since the O-ring and the screw-locking machined seat required to install the chain tensioner in a hermetically sealed state in the conventional technology can be eliminated, the cost can be reduced, and the design freedom relating to the arrangement of the chain tensioner is improved. 
     It is preferable that the above-mentioned engine has the following configuration. In other words, in the engine, the elastic member is a coil spring, and the guide member has a protruding section formed on the face on the side of the chain tensioner and engaged with the inside space of the coil spring. 
     With the above-mentioned configuration, the coil spring accommodated in the accommodating concave section can be prevented from being detached and displaced. 
     In the engine, the protruding section has a tapered shape. 
     Although the protruding section can be formed into, for example, a cylindrical shape having ridge lines extending in parallel, with the above-mentioned configuration, the coil spring can be bent and deformed in response to the swinging of the guide member more significantly. 
     In the engine, when the elastic member is accommodated in the accommodating concave section, the clearances in the movement direction of the endless transmission belt are determined so as to be wider than the clearances in a direction approximately orthogonal to the movement direction of the endless transmission belt. 
     With the above-mentioned configuration, since the coil spring can be bent and deformed significantly in the movement direction of the endless transmission belt, the coil spring can provide an appropriate tension to the endless transmission belt being traveling. 
     In the engine, the lid member is secured to the case member. 
     Although the function of the lid member can be included in the cover member for covering the case member, with the above-mentioned configuration, the opening section of the accommodating concave section can be covered securely. 
     In the engine, the cover member has a structure of holding the joint section of an oil pipe in the direction of the drive shaft. 
     With the above-mentioned configuration, since the lid member serves to cover the opening section of the accommodating concave section and to hold the joint section of the oil pipe, the number of components can be reduced. 
     In the engine, the driven shaft is a pump driving shaft for driving an oil pump and/or a cooling water pump. 
     Although the driven shaft may be a cam driving shaft, a cam driving intermediate shaft, etc., with the above-mentioned configuration, the accommodating concave section and the opening section can be formed easily, and excellent installation performance can be provided for the elastic member and the lid member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a left side view showing a utility vehicle equipped with an engine according to an embodiment of the present invention; 
         FIG. 2  is a partially cutaway enlarged left side view of the engine shown in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken on line of  FIG. 2 ; 
         FIG. 4  is an enlarged perspective view illustrating a pump driving chain mechanism in the engine shown in  FIG. 2 ; 
         FIG. 5  is a schematic cross-sectional view taken on line V-V of  FIG. 4 ; 
         FIG. 6  is a partially cutaway cross-sectional view taken on line VI-VI of  FIG. 4 ; and 
         FIG. 7  is a partially cutaway enlarged left side view of the engine according to the conventional example. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An engine  20  according to an embodiment of the present invention will be described below in detail referring to  FIGS. 1 to 5 . 
       FIG. 1  is a left side view showing a utility vehicle  1  shown as an example of a vehicle. This utility vehicle  1  is used for leisure and hunting in fields and mountains, for travel on golf courses, for maintenance of golf courses and for other purposes. The front, rear, left and right referred to in this specification are based on the front, rear, left and right of the vehicle. 
     In  FIG. 1 , the utility vehicle  1  is equipped with a vehicle body  2  supported by a pair of left and right front wheels  3  and a pair of left and right rear wheels  4 . A cabin frame (ROPS)  6  enclosing a cabin (riding space)  5  is provided in the intermediate section of the vehicle body  2  in the front-rear direction. On the rear side of the cabin frame (ROPS)  6 , a luggage carrier  7  is provided. The cabin frame  6  is generally referred to as ROPS, which is an abbreviation for rollover protective structure. 
     A front seat  8  securely installed in the front section inside the cabin  5  usually extends in the left-right direction to the vicinities of both the left and right ends of the cabin  5 . Hence, two people can sit side by side; the driver can sit in one of seating areas (for example, the left side), and a passenger can sit in the other seating area. Under the front seat  8 , an engine box  11  for accommodating the engine  20  is disposed. Like the front seat  8 , a rear seat  9  disposed in the rear section inside the cabin  5  extends in the left-right direction to the vicinities of both the left and right ends of the cabin  5 . Hence, two passengers can sit side by side. 
     The engine  20  is a two-cylinder overhead camshaft V-type engine and is equipped with a forward-leaning front cylinder  21 , a backward-leaning rear cylinder  22  and a crankcase  23  serving as a case member. An exhaust pipe  13  connected to the front lower face of the front cylinder  21  is bent leftward and extends backward. An exhaust pipe  14  connected to the rear upper face of the rear cylinder  22  extends nearly directly backward and downward, then slightly extends forward, further extends to the rear side of the vehicle body, and merges with the exhaust pipe  13 . Both the exhaust pipes  13  and  14  are connected to one exhaust muffler  15  disposed at the rear end section of the vehicle. The output of the engine  20  is transmitted to the rear wheels  4  or all the wheels  3  and  4  via a drive shaft, a chain, etc., not shown, to drive and rotate the rear wheels  4  or all the wheels  3  and  4 , thereby providing propulsion power to the utility vehicle  1 . 
       FIG. 2  is a partially cutaway enlarged left side view of the engine  20  shown in  FIG. 1 . The front cylinder  21  and the rear cylinder  22  are each constructed by sequentially fastening a cylinder  47 , a cylinder head  48  and a cylinder head cover  49  to the crankcase  23 , and valve-driving camshafts  51  and  52  are each provided in each of the cylinder heads  48 . A crankshaft  38  serving as a drive shaft and a cam driving intermediate shaft  53  serving as a driven shaft and disposed above the crankshaft  38  and on a V-bank center line E are respectively journaled on the crankcase  23 . The cam driving intermediate shaft  53  is connected to the crankshaft  38  via a cam driving intermediate chain mechanism  55 . The camshaft  51  of the front cylinder  21  is connected to the cam driving intermediate shaft  53  via a cam driving chain mechanism (not shown) at a speed reduction ratio of 1:2. The camshaft  52  of the rear cylinder  22  is connected to the cam driving intermediate shaft  53  via a cam driving chain mechanism  57  at a speed reduction ratio of 1:2. 
     The cam driving intermediate chain mechanism  55  is accommodated in a generator chamber  60  (shown in  FIG. 3 ) formed on the left side of the crankcase  23  and is formed of a drive sprocket  61  (overlapped with a drive sprocket  70  described later and thus invisible in  FIG. 2 ) secured to the crankshaft  38 ; an intermediate sprocket  62  secured to the left end of the cam driving intermediate shaft  53 ; and a cam driving intermediate chain  63  serving as an endless transmission belt and wound between both the sprockets  61  and  62 . With this configuration, the power is transmitted from the crankshaft  38  to the cam driving intermediate shaft  53  at a speed reduction ratio of 1:1. A chain guide  65  is disposed on the tension side (front side) of the cam driving intermediate chain  63 , and a guide shoe  66  is disposed on the loose side (rear side) thereof. A tensioner (not shown) is provided for the guide shoe  66 . 
     The cam driving chain mechanism  57  for the rear cylinder  22  is formed of a cam sprocket  79  secured to the camshaft  52  of the rear cylinder  22  and serving as a driven shaft; an intermediate sprocket  80  secured to the cam driving intermediate shaft  53  and serving as a drive shaft, and overlapped with the intermediate sprocket  62  and thus invisible in  FIG. 2 ; and a rear cylinder cam chain  81  wound between both the sprockets  79  and  80  and serving as an endless transmission belt. Furthermore, the power is transmitted from the cam driving intermediate shaft  53  to the camshaft  52  of the rear cylinder  22  at a speed reduction ratio of 1:2. The front upper side of the rear cylinder cam chain  81  is its tension side and the rear lower side thereof is its loose side. A chain guide  83  is provided on the tension side. A guide shoe  84  rotatable around a fulcrum, not shown, and an automatic tensioner  85  for biasing the guide shoe  84  toward the chain are disposed on the loose side. The automatic tensioner  85  is a ratchet-type automatic tensioner formed of, for example, a rack, a ratchet pawl, a spring, etc. The automatic tensioner  85  is inserted into the rear lower wall of the cylinder  47  of the rear cylinder  22  from the rear lower side and secured with bolts or the like. 
     On the right side of the engine  20 , the cam driving chain mechanism (not shown in  FIG. 2 ) for the front cylinder  21  is also configured so as to be substantially similar to the above-mentioned cam driving chain mechanism  57  for the rear cylinder  22 . 
     A pump driving chain mechanism  30  is formed of a drive sprocket  70  disposed on the left side of the drive sprocket  61  and secured to the crankshaft  38 ; a pump driving sprocket  69  secured to a pump driving shaft  68 ; and a pump driving chain  71  wound between both the sprockets  69  and  70  and serving as an endless transmission belt, whereby the power is transmitted from the crankshaft  38  serving as a drive shaft to the pump driving shaft  68  serving as a driven shaft at a speed reduction ratio of approximately 1:8. The upper section  71   a  (shown in  FIG. 4 ) of the pump driving chain  71  is its tension side, and the lower section  71   b  (shown in  FIG. 4 ) thereof is its loose side. On the loose side, a guide member  74  rotatable around a fulcrum  74   a  and a chain tensioner  75  for biasing the guide member  74  toward the chain are disposed. The chain tensioner  75  is constructed by inserting a coil spring  31  into an accommodating concave section  33  provided in the left wall  23   a  of the crankcase  23 , by covering the opening section  33   a  (not shown in  FIG. 2  but shown in  FIG. 4 ) of the accommodating concave section  33  with a lid member  35  and by securing the lid member  35  with a bolt  37  as described later in detail. 
       FIG. 3  is a cross-sectional view taken on line of  FIG. 2  and shows the inside of the space enclosed by the crankcase  23  and a generator cover  42 . In  FIG. 3 , the cylinder center line C 1  of the front cylinder  21  is positioned on the left side of the cylinder center line C 2  of the rear cylinder  22 . The intermediate sprocket  80  is provided at the left end section of the cam driving intermediate shaft  53  serving as a drive shaft. In addition, as shown in  FIG. 2 , the rear cylinder cam chain  81  passes through a chain tunnel (not shown) and is wound around the cam sprocket  79 , thereby driving the camshaft  52  (driven shaft) of the rear cylinder  22 . 
     The cam driving intermediate chain mechanism  55  is disposed on the further left side of the intermediate sprocket  80  and at the left end section of the cam driving intermediate shaft  53 . In the cam driving intermediate chain mechanism  55 , the cam driving intermediate chain  63  is wound between the drive sprocket  61  of the crankshaft  38  serving as a drive shaft and the intermediate sprocket  62  of the cam driving intermediate shaft  53  serving as a driven shaft, and the cam driving intermediate chain  63  drives the cam driving intermediate shaft  53 . 
     In  FIG. 2 , the pump driving chain mechanism  30  is disposed on the further left side of the drive sprocket  61  and close to a generator  40 . In the pump driving chain mechanism  30 , the pump driving chain  71  is wound between the drive sprocket  70  of the crankshaft  38  serving as a drive shaft and the pump driving sprocket  69  of the pump driving shaft  68  serving as a driven shaft, and the pump driving chain  71  drives the pump driving shaft  68 . 
     The generator cover  42  is fastened to the left wall  23   a  of the crankcase  23  with a plurality of bolts (not shown), and the generator cover  42  hermetically seals the generator chamber  60 . The generator  40  is accommodated in the generator chamber  60  provided on the left side of the crankshaft  38  rotatably supported on the crankcase  23 . The rotor  41  of the generator  40  is secured to the left end section of the crankshaft  38  with a screw member  39 , and the stator coil  43  of the generator  40  is secured to the right inside face of the generator cover  42  with screw members  44 . 
     In  FIG. 3 , a pump unit  25  driven by the pump driving shaft  68  is disposed below the generator  40 . The pump unit  25  is equipped with a cooling water pump  26  for transferring cooling water to the engine  20  and an oil pump  27  for transferring lubricating oil to the engine  20 , etc. The cooling water pump  26  is, for example, a centrifugal pump. Furthermore, the oil pump  27  is, for example, a trochoid pump. The pump driving shaft  68  is journaled on the crankcase  23  in nearly parallel with the crankshaft  38 . At the left end section of the pump driving shaft  68 , the cooling water pump  26  is fastened to the outside face of the generator cover  42  with a plurality of bolts  28 . In addition, at the right end section of the pump driving shaft  68 , the oil pump  27  is fastened to the left wall  23   a  of the crankcase  23  with a plurality of bolts  29 . 
     On the pump driving shaft  68 , the pump driving sprocket  69  is secured to the position between the cooling water pump  26  and the oil pump  27 . In the above-mentioned configuration, the power of the engine  20 , i.e., the rotation of the crankshaft  38 , is transmitted to the pump driving shaft  68  via the drive sprocket  70  of the crankshaft  38 , the pump driving chain  71  and the pump driving sprocket  69 , thereby integrally rotating the cooling water pump  26  and the oil pump  27 . The cooling water pump  26  or the oil pump  27  may serve as the pump unit  25  that is driven by the pump driving shaft  68 . The oil discharged from the oil pump  27  is supplied to the rotating sections, the sliding sections, etc. of the engine  20  via a primary oil filter  92  shown in  FIG. 3  and a secondary oil filter  58  and a water-cooling oil cooler  59  shown in  FIG. 2  and then returned to an oil pan (not shown) provided below the crankcase  23 . The cooling water delivered from the cooling water pump  26  also passes through the water-cooling oil cooler  59  to cool the water-cooling oil cooler  59 . 
     Next, the pump driving chain mechanism  30  will be described below in detail referring to  FIGS. 4 to 6 . 
       FIG. 4  is an enlarged perspective view illustrating the pump driving chain mechanism  30  in the engine  20  shown in  FIG. 2 , and the drive sprocket  70  secured to the crankshaft  38  shown in  FIG. 2  is not shown in  FIG. 4 . Furthermore,  FIG. 5  is a schematic cross-sectional view taken on line V-V of  FIG. 4 , and  FIG. 6  is a partially cutaway cross-sectional view taken on line VI-VI of  FIG. 4 . 
     The crankshaft  38  (not shown in  FIG. 4  but shown in  FIG. 2 ) and the pump driving shaft  68  are designed to rotate counterclockwise. The upper section  71   a  of the pump driving chain  71  is its tension side going to the crankshaft  38 , and the lower section  71   b  of the pump driving chain  71  is its loose side going to the pump driving shaft  68 . 
     The pump driving chain mechanism  30  is formed of the drive sprocket  70  of the crankshaft  38 , the pump driving sprocket  69  of the pump driving shaft  68 , and the pump driving chain  71  wound between both the sprockets  69  and  70  as described above. 
     The guide member  74  makes pressure contact with the lower section  71   b  (loose side) of the pump driving chain  71 . The guide member  74  extends from its front end section  74   b  to its rear end section  74   c  along the lower section  71   b  of the pump driving chain  71 . The front end section  74   b  of the guide member  74  is pivoted by a pivot bolt  74   e  so as to be rotatable around the fulcrum  74   a  at the left wall  23   a  in the vicinity of the lower section of the drive sprocket  70  (not shown in  FIG. 4  but shown in  FIGS. 2 and 3 ) of the crankshaft  38 . The rear end section  74   c  of the guide member  74  is positioned in the vicinity of the lower section of the pump driving sprocket  69 . The guide member  74  ranging from its front end section  74   b  to its rear end section  74   c  is equipped with a guide  74   d  for guiding the lower section  71   b  of the pump driving chain  71 . The rear end section  74   c  of the guide member  74  is bent downward so as to be away from the lower section  71   b  of the pump driving chain  71 . 
     The upper end section of the coil spring (elastic member)  31  accommodated in the accommodating concave section  33  makes pressure contact with a pressing seat  74   f  formed on the lower face of the rear end section  74   c  of the guide member  74 . The pressing seat  74   f  is equipped with a protruding section  74   g  (shown in  FIG. 5 ) protruding in a direction nearly orthogonal to the seating face of the pressing seat  74   f  and engaging with the upper inside space of the coil spring  31 . By virtue of the engagement between the protruding section  74   g  and the upper inside space of the coil spring  31 , the coil spring  31  accommodated in the accommodating concave section  33  can be prevented from being detached and displaced inadvertently. Although the protruding section  74   g  (shown in  FIGS. 5 and 6 ) may have a cylindrical shape, it is preferable that the lower end of the protruding section  74   g  should have a tapered shape. The lower end of the protruding section  74   g  has a tapered shape, such as a cone shape or a truncated cone shape (shown in  FIG. 6 ), for example. By virtue of the tapered shape of the lower end of the protruding section  74   g , the coil spring  31  can be bent and deformed in response to the swinging of the guide member  74  more significantly. The protruding amount of the protruding section  74   g  is determined so that the protruding section  74   g  is engaged with the upper inside space of the coil spring  31  and so that the coil spring  31  is not detached inadvertently from the accommodating concave section  33 . 
     The chain tensioner  75  is equipped with the accommodating concave section  33 , the coil spring (elastic member)  31 , and the lid member  35 . The accommodating concave section  33  is formed in the left wall  23   a  located close to the pump driving sprocket  69 . An opening section (not shown in  FIG. 4 ) through which the upper section of the coil spring  31  protrudes toward the lower section  71   b  of the pump driving chain  71  is provided in the upper section of the accommodating concave section  33 . The opening section  33   a  is provided on the side face of the accommodating concave section  33  on the side opposite to the generator cover  42  (not shown in  FIG. 4  but shown in  FIG. 3 ). The opening section  33   a  receives the lower section of the coil spring  31  so that the coil spring  31  is loaded in an inside direction nearly parallel with the crankshaft  38  (not shown in  FIG. 4  but shown in  FIG. 2 ) and the pump driving shaft  68 . The accommodating concave section  33  has a rectangular shape in cross-section as shown in  FIG. 5 . Furthermore, the coil spring  31  has a ring shape in cross-section as shown in  FIG. 5 . Moreover, when the coil spring  31  sits on the accommodating concave section  33  while the protruding section  74   g  is engaged with the upper inside space of the coil spring  31 , the clearances around the coil spring  31  accommodated in the accommodating concave section  33  are determined so that clearances  33   b  in the movement direction of the lower section  71   b  of the pump driving chain  71  become wider than clearances  33   c  in a direction approximately orthogonal to the movement direction of the lower section  71   b  of the pump driving chain  71 . 
     The lid member  35  for covering the opening section  33   a  of the accommodating concave section  33  in which the coil spring  31  is loaded is disposed in the vicinity of the accommodating concave section  33 . As shown in  FIG. 4 , the lid member  35  is equipped with a lid section  35   a  and a pressing section  35   b  and has a generally L-shaped bent shape. A bolt insertion hole  35   d  is formed at an intersection  35   c  at which the lid section  35   a  intersects with the pressing section  35   b . The lid member  35  is secured to the installation section  23   f  of the left wall  23   a  by screwing the bolt  37  (i.e. fastener  37 ) into the screw hole  23   h  (shown in  FIG. 6 ) of the installation section  23   f  formed in the left wall  23   a . The lid section  35   a  covers the opening section  33   a  of the accommodating concave section  33  so that the coil spring  31  being compressed does not come off from the opening section  33   a . The pressing section  35   b  has a step shape protruding in the inward direction of the drive shaft, thereby pressing the joint section  54   a  of an oil pipe  54  in the inward direction of the drive shaft. 
     The chain tensioner  75  is installed in the accommodating concave section  33  disposed in the left wall  23   a  of the crankcase  23  according to the following procedure. First, the protruding section  74   g  (shown in  FIGS. 5 and 6 ) protruding from the pressing seat  74   f  formed on the rear end section  74   c  of the guide member  74  is inserted into the upper inside space of the coil spring  31  being compressed, whereby the coil spring  31  being compressed is loaded into the accommodating concave section  33 . Since the upper section of the coil spring  31  being compressed is engaged with the protruding section  74   g  of the guide member  74  at this time, the coil spring  31  being compressed can be stably held in the accommodating concave section  33 , even if the opening section  33   a  of the accommodating concave section  33  is not covered with the lid section  35   a  of the lid member  35 . The lid member  35  is positioned so that the lid section  35   a  covers the opening section  33   a  of the accommodating concave section  33  and so that the pressing section  35   b  presses the joint section  54   a  of the oil pipe  54  in the inward direction of the drive shaft. Then, the lid member  35  is secured to the installation section  23   f  of the left wall  23   a  by screwing the bolt  37  into the screw hole  23   h  (shown in  FIG. 6 ) of the installation section  23   f  via the bolt insertion hole  35   d  of the lid member  35 . 
     The chain tensioner  75  biases the lower section  71   b  (loose side) of the pump driving chain  71  toward the upper section  71   a  (tension side) via the guide member  74 , thereby being capable of applying appropriate tension to the lower section  71   b  of the pump driving chain  71 . The coil spring  31  can be easily inserted into and removed from the accommodating concave section  33  by simply removing the generator cover  42  shown in  FIG. 3 . Furthermore, since the coil spring  31  directly presses the guide member  74 , the number of components and the processing man-hour relating to the chain tensioner  75  can be reduced. Moreover, since the chain tensioner  75  is accommodated in the crankcase  23 , the components and processes relating to the sealing structure for installing the chain tensioner  75  in a hermetically sealed state can be eliminated, and the cost can be reduced. Still further, since the sealing structure for installing the chain tensioner  75  in the hermetically sealed state is not required, the design freedom relating to the arrangement of the chain tensioner  75  is improved. 
     Although an embodiment according to the present invention has been described specifically, the scope of the present invention is not limited to the above-mentioned configuration. For example, the mechanism for transmitting the rotation of the crankshaft  38  to the pump driving shaft  68  is not limited to the chain mechanism formed of the pump driving chain  71  and the sprockets  69  and  70  but may be a belt-pulley mechanism formed of a belt and pulleys. Furthermore, the chain tensioner  75  is not limited to be applied to the pump driving chain mechanism  30  but may also be applied to the above-mentioned cam driving chain mechanisms for the front cylinder  21  and the rear cylinder  22  and to the above-mentioned cam driving intermediate chain mechanism  55 . Moreover, the inside face of the generator cover  42  for covering the left wall  23   a  of the crankcase  23  may be configured so as to have the function of the lid member  35  formed of the lid section  35   a  and the pressing section  35   b.    
     The luggage carrier  7  of the utility vehicle  1  can be configured according to the needs of the user so as to be extendable forward so that the widths or capacities of the space of the luggage carrier  7  and the space occupied by passengers can be used to the greatest extent. The engine  20  according to the present invention can also be applied to this type of utility vehicle  1 . 
     In addition, although an example in which the engine  20  according to the present invention is mounted on the utility vehicle  1  is described as a preferred embodiment, the engine  20  according to the present invention can also be applied to off-road four-wheel vehicles, motorcycles, etc.