Abstract:
A component fitting structure includes a component fitting hole ( 25 ) formed across mated faces between a cylinder head ( 4 ) and chain cover ( 24 ), and a collar ( 26 ) fitted in the component fitting hole through a liquid gasket, a tensioner unit  21   a  being engaged with the collar. Because the component fitting portion extends across the mated faces the members themselves can be made smaller in size. Further, since the collar can be attached in advance to one of these members before they are mated together, the fitting portion of the component can be easily observed visually. Further, the component can be removed without separating the two members from each other.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a component fitting structure, and more particularly to a structure for fitting the component such as a tensioner unit for automatically adjusting tension of a chain which is wound around a crank sprocket and a cam sprocket to an end of an engine at a side of a crank pulley. 
     2. Description of the Related Art 
     As the structures of the type, there have been known such a structure that the tensioner unit is fitted to an end face of a cylinder block or a cylinder head that is a first member at a side of the chain, and then, an end face of the engine in a direction of a crankshaft including a fitting portion of the tensioner unit is covered with a chain cover that is a second member, Such a structure also have been known that the fitting portion of the tensioner unit is provided on an extended portion of a side wall of the cylinder block or the cylinder head and covered with a removable cover. 
     The former of the above described conventional structures has a drawback that it is likely to deteriorate in assembly, conservaton and maintenance, since the chain cover grows larger in order to cover the tensioner unit and further the entire chain cover must be removed to get access to the tensioner unit. The latter structure has also a drawback that the face of the cylinder block or the cylinder head to be mated with the chain cover expands in a direction of the crankshaft, and accordingly, upsizing of the engine is inevitable. 
     SUMMARY OF THE INVENTION 
     The invention has been made in order to solve the above described problems of the conventional art. It is an object of the invention to provide a component fitting structure in which the chain cover or a belt cover and the cylinder block or the cylinder head can be minimized without deteriorating in assembling workability and maintainability. 
     In order to attain such an object, there is provided according to the invention, a component fitting structure which comprises a component fitting hole ( 25 ) formed across mated a mated faces between a first member (e.g. a cylinder head  4  in an embodiment or a cylinder block) and a second member (e.g. a chain cover  24  in the embodiment or a belt cover) and a collar ( 26 ) fitted in the component fitting hole through a liquid gasket, the component to be fitted (e.g. a tensioner unit  21   a  in the embodiment) being engaged with the collar. 
     According to the invention, because the component fitting portion can be provided across the mated faces between the first member and the second member, the members themselves can be made smaller in size as compared with the case where the component is fitted to either one of the members. Moreover, because the collar can be attached in advance to one of these members before the first and the second members are mated together, the fitting portion of the component can be easily observed visually. Further, the component can be removed without separating the two members from each other. 
     According to a second aspect of the invention, the component fitting hole comprises a semicircular recess formed in the first member and a semicircular recess formed in the second member. 
     According to a third aspect of the invention, the component to be fitted is engaged with an inner peripheral face of the collar through an O-ring. 
     According to a fourth aspect of the invention, the collar is provided with a locating pin at a position on an outer peripheral face thereof, the locating pin being fitted in a corresponding hole formed in a bottom face of the recess of the fitting hole. 
     According to a fifth aspect of the invention, the locating pin is integrally formed with the collar. 
     According to a sixth aspect of the invention, the mated faces are displaced from a plane passing a center of the component to toward either of the first member and the second member. 
     According to a seventh aspect of the invention, the mated faces are in alignment with the center of the component to be fitted. 
     According to an eighth aspect of the invention, there is provided a component fitting structure which comprises a component fitting hole formed across mated contact between a first member and a second member, and a collar fitted in the component fitting hole through a liquid gasket, the component to be fitted being engaged with the collar, the component fitting hole comprising a semicircular recess formed in the first member and a semicircular recess formed in the second member, and the component to be fitted being engaged with an inner peripheral face of the collar through an O-ring. 
     According to a ninth aspect of the invention, there is provided a component fitting structure which comprises a component fitting hole formed in a cylinder head or a cylinder block as a first member and a chain cover or a belt cover as a second member across mated mated faces therebetween, and a collar fitted in the component fitting hole through a liquid gasket, a tensioner unit as the component to be fitted being engaged with the collar. 
     According to a tenth aspect of the invention, the component fitting hole comprises a semicircular recess formed in the cylinder head or the cylinder block and a semicircular recess formed in the chain cover or the belt cover. 
     According to an eleventh aspect of the invention, the tensioner unit is engaged with an inner peripheral face of the collar through an O-ring. 
     According to a twelfth aspect of the invention, the collar is provided with allocating pin at a position on an outer peripheral face thereof, the locating pin being fitted in a corresponding hole formed in a bottom face of the recess of the fitting hole. 
     According to a thirteenth aspect of the invention, the locating pin is integrally formed with the collar. 
     According to a fourteenth aspect of the invention, the mated faces are in alignment with a center of the tensioner unit. 
     According to a fifteenth aspect of the invention, the mated faces are slightly displaced from a plane passing the center of the tensioner unit toward the cylinder head or the cylinder block. 
     According to a sixteenth aspect of the invention, the component fitting hole comprises a semicircular recess formed in the cylinder head or the cylinder block and a semicircular recess formed in the chain cover or the belt cover, and an inner peripheral face of the semicircular recess in the chain cover or the belt cover is tangentially extended from a straight line which is parallel to the mated faces. 
     According to a seventeenth aspect of the invention, fitting bolts of the tensioner unit are fastened at two points in the cylinder head or the cylinder block. 
     According to an eighteenth aspect of the invention, the cylinder head or the cylinder block is provided with bolting holes along a straight line which is perpendicular to the mated faces and passes the center of the tensioner unit. 
     According to a nineteenth aspect of the invention, the chain cover is provided with an access hole in order to remove a lock pin for locking an operation of a plunger of the tensioner unit, and a boss including the access hole and a boss around the fitting hole are connected by a rib. 
     According to a twentieth aspect of the invention, the tensioner unit is fitted to an exterior of a bank of a V-type engine and a single bolting hole is provided in the cylinder head or the cylinder block. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view of a V-type engine at a side of a crank pulley to which the present invention is applied; 
     FIG. 2 is an enlarged side view showing an essential part of the invention; 
     FIG. 3 is a view partly in section taken along a line III—III in FIG. 2; 
     FIG. 4 is an enlarged side view showing a modified embodiment of the invention; 
     FIG. 5 is an enlarged side view showing another modified embodiment of the invention; and 
     FIG. 6 is an exploded perspective view of an essential part showing an area around an access hole for removing a lock pin. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now, preferred embodiments according to the invention will be described in detail by way of examples referring to the attached drawings. 
     FIG. 1 is an elevational view of a four cycle V-type eight cylinder engine at a side of a crank pulley to which the present invention is applied. 
     The engine E comprises an upper block  1  having a pair of cylinder banks, a lower block  2  mated to a lower face of the upper block  1 , an oil pan  3  attached to a lower face of the lower block  2 , and cylinder heads  4  respectively attached to upper faces of the two cylinder banks of the upper block  1 . The two cylinder banks provide a bank angle of 90 degree between them. Above each of the cylinder heads  4  is provided two camshafts  5 . These camshafts  5  are covered with respective head covers  6  which are attached to upper faces of the cylinder heads  4 . 
     A crankshaft  7  is supported by a main bearing on mated faces between the upper block  1  and the lower block  2  in the same manner as in the conventional engine. 
     A compressor  8  of an air conditioner is mounted on the upper block  1  at right hand of the crankshaft  7  in FIG. 1, and an alternator  9  is mounted on the lower block  2  at left hand of the crankshaft  7  in FIG.  1 . These compressor  8  and the alternator  9  are synchronously connected to the crankshaft  7  by a belt-pulley mechanism which is not shown in the drawing. 
     At an inner position in an axial direction of the above described crank pulley, the crankshaft  7  is provided with a crank sprocket  10  and at a further inner axial position, with a drive pinion  11 . 
     The drive pinion  11  synchronously meshes with two driven pinions  12  which are provided at symmetrical positions with respect to a vertical plane bisecting the provided angle between the banks and passing a center of the crankshaft. These two driven pinions  12  are integrally provided with small sprockets  13  respectively. Each of silent chains  15  for driving the camshafts is wound around each of these small sprockets  13  and cam sprockets  14  provided on the two camshafts  5  of each of the cylinder banks as shown in FIG.  1 . Thus, the rotation of the crankshaft  7  is transmitted to the two each of the camshafts  5  of both the banks. 
     The upper block  1  and the lower block  2  are divided at a horizontal plane passing the center of the crankshaft. At vertically symmetrical positions with respect to the dividing plane are pivotally supported two balance shafts  16   a ,  16   b  whose axes extend in parallel to the crankshaft  7 . 
     The balance shaft  16   b , which is supported at a side of the lower block  2 , is fitted a balance shaft sprocket  17 . By winding a silent chain  19  around the balance shaft sprocket  17 , the crank sprocket  10 , and a pump sprocket  18  which is fixed to an oil pump (not shown) attached to a lower face of the lower block  2 , the lower balance shaft  16   b  and the oil pump are driven to rotate synchronously with the crankshaft  7 . 
     The two balance shafts  16   a ,  16   b  are adapted to rotate in reverse directions with respect to each other at a same rotation speed by a mesh between gears  20   a ,  20   b  which have the same teeth number and are fitted to axially inner positions of the balance shaft sprocket  17 . 
     Tensioner units  21   a ,  21   b ,  21   c  automatically adjust a driving force by a hydraulic plunger. Tensioner shoes  22   a ,  22   b ,  22   c  apply pressing forces from the tensioner units to the silent chain  19 . Tensioner units  21   a ,  21   b ,  21   c , tensioner shoes  22   a ,  22   b ,  22   c  and vibration preventing chain guides  23   a ,  23   b ,  23   c  are respectively provided on the silent chains  15  which are wound around the camshafts  5  and the cam sprockets  14  of both the cylinder banks and on the silent chain  19  which is wound around the balance shaft sprocket  17  and the pump sprocket  18 . 
     The whole chain-sprocket mechanism is covered with the chain cover which will be described later. 
     Now, the structures for fitting the tensioner units  21   a ,  21   b  on both the cylinder banks will be described. Because the two tensioner units  21   a ,  21   b  are of the same structure, only the tensioner unit  21   a  of the right hand bank will be described here. 
     As shown in FIGS. 2 and 3, the tensioner unit  21   a  is fitted in a tensioner unit fitting hole  25  comprising two cooperating semicircular recesses  25   a ,  25   b . The tensioner unit fitting hole  25  is formed across mated faces between the cylinder head  4  as a first member and a chain cover  24  as a second member. More particularly, an annular collar  26  is fitted in the fitting hole  25  which serves as a component fitting hole through a liquid gasket (not shown). The tensioner unit  21   a  which is the component to be fitted is adapted to be fitted to an inner peripheral face of this collar  26  through an O-ring  27 . FIG. 2 is shown in a state where the tensioner unit  21   a  is removed. 
     Even though accuracy of perfect roundness of the fitting hole  25  has been lost due to an error in assembling the chain cover  24  to the cylinder head  4 , this arrangement will completely eliminate such fears that the O-ring may be broken and a sealing property may be lost, because the O-ring  27  is abutted against the inner peripheral face of the collar  26 . 
     Steps of fitting the tensioner unit  21   a  start with fitting of the collar  26  to the semicircular recess  25   b  at the side of the cylinder head  4  prior to fitting the chain cover  24 . On this occasion, the liquid gasket is first applied to an inner peripheral face of the recess  25   b  or an outer peripheral face of the collar  26 . Then, a locating pin  28  projectingly formed at a position of the outer peripheral face of the collar  26  is fitted in a corresponding hole  29  in a bottom face of the recess  25   b . Next, the tensioner unit  21   a  is inserted into the collar  26  and fixed by two fitting bolts B 1 , B 2  screwed into the cylinder head  4 . By thus providing the two fitting bolts at the side of the cylinder head  4 , an adequate fitting rigidity can be obtained in a state before mounting the chain cover  24 . Therefore, the connected part between the tensioner unit  21   a  and the tensioner shoe  22   a  can be easily observed visually, and at the same time, the assembling workability of the connected part can be improved. 
     Integrally forming the locating pin  28  with the collar  26  will contribute to reduction of number of the components. 
     Finally, the chain cover  24  is fitted to an inner peripheral face of the semicircular recess  25   a  at the side of the chain cover  24  or the outer peripheral face of the collar  26  after applying the liquid gasket thereto. Then, a fitting bolt B 3  of the tensioner unit  21   a  is screwed into the chain cover  24 . 
     By thus interposing the collar  26  in the fitting hole  25  formed at the mated faces between the cylinder head  4  and the chain cover  24 , the tensioner unit  21   a  can be liquid-tightly assembled to the mated faces between the cylinder head  4  and the chain cover  24  while being independent from an assembling accuracy of the chain cover  24  relative to the cylinder head  4 . 
     In this embodiment, the mated faces between the cylinder head  4  and the chain cover  24  are slightly displaced toward the cylinder head  4  from a plane passing a center of the tensioner unit  21   a  by a length A as shown in FIG.  2 . For this reason, the inner peripheral face of the semicircular recess  25   a  at the side of the chain cover  24  is tangentially extended from a diametrical line D which is parallel to the mated faces, and the chain cover  24  can be fitted without problem after the collar  26  has been fitted to the cylinder head  4  in advance. This arrangement can make a dimension of the cylinder head  4  in an axial direction of the crankshaft as small as possible and contributes to a light weight of the engine as a whole. 
     The perfect roundness of the fitting hole  25  may be lost in the above described structure, but a gap created to such an extent will not present an obstacle to secure the liquid tightness by the liquid gasket. 
     Moreover, because the chain tensioner unit  21   a  is fitted to the cylinder head  4  by the collar  26 , it can be fixed and detached without removing the chain cover  24 , and the upkeeping and maintainability will be improved. Particularly, because the locating pin  28  serves to locate the collar  26 , workability of fitting and removing the tensioner unit  21   a  will be enhanced. 
     In case where the bolting holes  30  are formed in the cylinder head  4  along a straight line L which is perpendicular to the mated faces between the cylinder head  4  and the chain cover  24  and passes the center of the chain tensioner unit  21   a  as shown in FIG. 4, the tensioner unit  21   a  will be prevented from rotating to come out of the recess  25   b  in the cylinder head  4 , even though the tensioner unit  21   a  is temporarily fastened to the cylinder head  4  with a single bolt. Accordingly, the working steps of fitting the tensioner unit  21   a  to an exterior of a bank of the V-type engine which provides a downwardly facing diagonal face will be reduced in number. 
     Further, in case where the mated faces between the cylinder head  4  and the chain cover  24  are in alignment with the center of the tensioner unit  21   a  as shown in FIG. 5, both the recess  25   a  in the chain cover  24  and the recess  25   b  in the cylinder head  4  present perfect semicircles respectively. In this case, as the gap between the inner peripheral face of the fitting hole  25  and the outer peripheral face of the collar  26  will be constant along the entire circumference, the sealing property can be further enhanced. 
     In either of the embodiments as shown in FIGS. 2,  4  and  5 , the fixing part of the tensioner unit  21   a  is provided also at the side of the head cylinder  4  which has high rigidity, and therefore, an enhanced fitting rigidity can be obtained. 
     The chain cover  24  may be provided with an access hole  31  (usually closed with a plug) in order to remove a lock pin for retaining the plunger of the tensioner unit  21   a  so as not to operate during transportation as shown in FIG. 6, and a boss  32  including the access hole  31  and a boss  33  around the fitting hole  25  may be connected by a rib  34 . In this case, the access hole  31  and the fitting hole  25  can be connected by a short rib because they are positioned close to each other, and accordingly, the rigidity around this area can be enhanced while restraining an increase in weight to the least extent. 
     It is to be noted that the invention is not limited to the application to such the chain tensioner unit as described above, but may be applied, for example, to a fitting hole for a sensor which detects a rotation angle of a camshaft or a crankshaft, and an inspection hole which is provided in order to confirm a phase of a balance shaft and usually closed with a plug. Further, the invention is not necessarily applied to an engine, but similarly applied to any case wherein a component is fitted in a hole which is formed across mated faces of two members. 
     Note that although in the embodiment above the fitting structure among the cylinder head  4 , the chain cover  24  and the tensioner unit  21   a  are explained, the present invention may be applied to a fitting structure among a cylinder block, a belt cover attached to the cylinder block and a tensioner unit for a belt. At this time, the chain  15  may be replaced with the belt, and the chain cover  24  may be replaced with the belt cover. 
     According to the invention, the component such as the tensioner unit can be fitted in such a manner as interposed between the two members, for example, at the mated faces between the cylinder head or the cylinder block and the chain cover or the belt cover. Therefore, remarkable effects can be obtained in improving the fitting workability and the maintainability without damaging the sealing property and incurring upsizing. 
     While there has been described in connection with the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is aimed, therefore, to cover in the appended claim all such changes and modifications as fall within the true spirit and scope of the invention.