Abstract:
An engine cylinder head cover and assembly method thereof is disclosed to constantly maintain the arrangement of a cylinder head cover in relation to a cylinder head by a simple operation, whereby locking bolts for fastening the cylinder head cover onto the cylinder head can be quickly and effectively assembled, thereby improving ease of assembly of the engine.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority of Korean Application Nos. 2002-58170, filed on Sep. 25, 2002, and 2003-51388, filed Jul. 25, 2003, the disclosures of which are incorporated fully herein by reference. 
   FIELD OF THE INVENTION 
   The present invention relates to an engine cylinder head cover and an assembly method thereof and, more particularly, to a technique for facilitating the assembly of the engine cylinder head cover. 
   BACKGROUND OF THE INVENTION 
   A cylinder head cover generally made of a plastic material, in comparison with a metallic cylinder head, is fastened onto a cylinder head by using a plurality of locking bolts. 
   The plastic cylinder head cover is advantageous both in reducing weight of the engine and in improving ease of manufacture of the cylinder head cover. However, there is a drawback in that rigidity of holes for coupling the locking bolts is inadequate and the processing accuracy is relatively low. 
   Accordingly, in order to attain a sufficient rigidity for holes formed at the plastic cylinder head cover, bushings made of steel are inserted into the cylinder head cover to be fastened with the locking bolts. 
   SUMMARY OF THE INVENTION 
   Embodiments of the present invention maintain a constant arrangement of a cylinder head cover in relation to a cylinder head by a simple operation. The present invention also provides a fast and effective assembling operation of locking bolts for installing a cylinder head cover on a cylinder head, thereby facilitating the assembly of an engine. 
   In accordance with one embodiment of the present invention, an engine cylinder head cover comprises a round bushing whose inner circular diameter closely attaches to the shank of the locking bolts, and a long hollow bushing having an oval-shaped pipe hole. The inner flat edge of the oval-shaped pipe hole closely attaches to the shank of the locking bolts, wherein the length of the inner flat edge of the oval-shaped pipe hole is longer than the shank&#39;s diameter of the locking bolts. 
   In accordance with another embodiment of the present invention, an engine cylinder head cover comprises two or more long hollow bushings, each having an oval-shaped pipe hole whose inner flat edge closely attaches to the shank of the locking bolts, wherein the length of the flat edge of the oval-shaped pipe hole is longer than the outer diameter of the shank of the locking bolts. 
   According to the present invention, there is also provided an assembly method of an engine cylinder head cover. A round bushing is initially assembled for provisionally inserting locking bolts into the cylinder head via a round bushing. The round bushing, which has an inner diameter for tight insertion of the shank of the locking bolts, is disposed at the cylinder head cover. Next, a long hollow bushing is assembled for provisionally fastening the locking bolts into the cylinder head via the long hollow bushing. The flat edge of the oval-shaped pipe hole then closely attaches to the shank of the locking bolts, wherein the length of the inner flat edge of the oval-shaped pipe hole is longer than the shank&#39;s diameter of the locking bolts. The locking bolts are then fastened at a fully tightening torque, wherein some of the locking bolts are assembled at the cylinder head via a plurality of assembling bushings, which are placed at the cylinder head cover and has larger inner diameters than that of the shank of the locking bolts, while other locking bolts are provisionally assembled at the cylinder head via the round bushing and the long hollow bushing. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For fuller understanding of the nature and objects of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings in which: 
       FIG. 1  is a plan view illustrating a cylinder head cover of an engine according to a first embodiment of the present invention; 
       FIG. 2  is an outer view illustrating a long hollow bushing of  FIG. 1 ; 
       FIG. 3  illustrates a second embodiment of the present invention; and 
       FIG. 4  is a flowchart describing an assembly method of an engine cylinder head cover according to an embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
   As illustrated in  FIG. 1 , a cylinder head cover  1  includes a round bushing  3 , a long hollow bushing  5 , and assembling bushings  7 . The round bushing  3  is formed at a central portion of the cylinder head cover  1  and has an inner diameter for tight insertion of the shank of locking bolts  9 . 
   The long hollow bushing  5  is formed with an oval-shaped pipe hole  11  whose inner flat edge tightly fits the shank of the locking bolts  9 , wherein the length of the flat edge is longer than the shank&#39;s diameter of the locking bolts  9 . The oval-shaped pipe hole  11 , of which its inner flat edge is parallel to the longitudinal direction of the cylinder head cover  1 , is formed at an outer portion of the cylinder head cover  1  in the longitudinal direction. 
   The oval-shaped pipe hole  11  of the long hollow bushing  5  is formed for absorbing any deformation or manufacturing defects of the cylinder head cover  1  in relation to the cylinder head. 
   When the inner flat edge of the oval-shaped pipe hole  11  according to the embodiment of the present invention is installed parallel to the longitudinal direction of the cylinder head cover  1 , the deformation and manufacturing defects generated in the plastic cylinder head cover  1  can be easily absorbed via the oval-shaped pipe hole  11 . Thus, the locking bolts  9  are simply fastened into the bolt holes of the cylinder head through the oval-shaped pipe hole  11 . 
   A plurality of assembling bushings  7  are formed at the cylinder head cover  1  for installing the long hollow bushing  5 , round bushing  3  and cylinder head cover  1  onto the cylinder head. 
   Each of the assembling bushings  7  is formed with a hole, which has a diameter larger than that of the shank of the locking bolts  9  but smaller than that of the head of the locking bolts  9 , for absorbing any manufacturing defects of the cylinder head cover  1  and the cylinder head. 
   The holes of the assembling bushings  7  have a relatively larger diameter than that of the shank of the locking bolts  9 , thereby allowing the locking bolts  9  to properly fit into the bolt holes of the cylinder head even in case of possible manufacturing defects of the cylinder head cover  1 . The hole is preferably formed with a size that can absorb any manufacturing defects and to have enough area for contacting with the head of the locking bolts  9 . 
   With reference to  FIG. 4 , the assembly method of the engine cylinder head cover  1  is described below. 
   According to an assembly method as shown in  FIG. 4 , a round bushing is provisionally assembled for forming the locking bolts  9  onto the cylinder head via the round bushing  3 . The round bushing  3  is installed at the cylinder head cover  1  and has an inner circular diameter for closely attaching to the shank of the locking bolts  9  (see S 1 ). Next, a long hollow bushing is provisionally assembled for forming the locking bolts at the cylinder head via the long hollow bushing  5  having an oval-shaped pipe hole  11 , which is placed at the cylinder head cover  1  and whose inner flat edge closely attaches to the shank of the locking bolts  9 , wherein the length of the flat edge is longer than the shank diameter of the locking bolts  9  (see S 2 ). Finally, locking bolts are assembled for fastening the locking bolts  9  at a fully tightening torque. Some of the locking bolts  9  are assembled at the cylinder head via a plurality of assembling bushings  7 , which are placed at the cylinder head cover  1 . Each assembling bushing  7  has a larger inner diameter than the shank&#39;s diameter of the locking bolts  9 , while the other locking bolts  9  are provisionally assembled at the cylinder head via the round bushing  3  and the long hollow bushing  5  (see S 3 ). 
   The round bushing provisional assembly step S 1  and the long hollow bushing provisional assembly step S 2  according to the present invention are manually performed. An operator, therefore, can permanently fix the location and arrangement of the cylinder head cover  1  in relation to the cylinder head via the round bushing provisional assembly step S 1  and the long hollow bushing provisional assembly step S 2 . Alternatively, the round bushing provisional assembly step S 1  and the long hollow bushing provisional assembly step S 2  may be executed by an automatic mechanism. 
   The round bushing provisional assembly step S 1  is completed by provisionally assembling the locking bolts  9  onto the cylinder head via the round bushing  3  disposed at a central part of the cylinder head cover  1 . The long hollow bushing provisional assembly step S 2  is completed by provisionally assembling the locking bolts  9  on the cylinder head via a long hollow bushing  5  having an oval-shaped pipe hole  11  at one edge of the cylinder head cover  1  in the longitudinal direction, wherein the inner flat edge of the oval-shaped pipe hole  11  is parallel with the longitudinal direction of the cylinder head cover  1 . 
   Following the completion of the round bushing provisional assembly step S 1 , the cylinder head cover  1  in relation to the cylinder head can be maneuvered freely along the axial direction of the locking bolt of the round bushing provisionally assembled via the round bushing  3 . Then, when the long hollow bushing provisional assembly step S 2  is completed, the maneuverability of the cylinder head cover  1  is restricted along the axial direction, so that the disposition and arrangement of the cylinder head cover  1  in relation to the cylinder head can be constantly fixed. 
   Accordingly, in the following locking bolts assembly step S 3 , even if any vibration or impact is transmitted to the engine during the assembly, the locking bolts  9  can be easily fastened, thereby facilitating the assembly of the engine cylinder head cover. 
   The locking bolts assembly step S 3  according to the embodiment of the present invention is executed by an automatic bolt tightening device, which simultaneously couples a plurality of locking bolts  9 , greatly shortening the assembling time. However, the locking bolts assembly step S 3  can be also manually performed. 
   The locking bolts assembly step S 3 , as shown in  FIG. 4 , comprises a loosely-tightening step S 4  and an assembling completion step S 5 . In the loosely-tightening step S 4 , the locking bolts  9  are assembled via the loosely-tightening torque, which is larger than the provisional assembly tightening torque used for provisionally assembling the locking bolts  9  through the round bushing  3  and the long hollow bushing  5 , but smaller than the fully tightening torque. 
   On the other hand, in the assembly completion step S 5 , the locking bolts  9  are re-tightened as the fully tightening torque after executing the loosely-tightening step S 4 . 
   The provisional assembly tightening torque is a torque required for constantly maintaining the disposition and arrangement of the cylinder head cover  1  in relation to the cylinder head while the locking bolts  9  are coupled to the assembling bushings  7 . The value of the provisional assembly tightening torque is preferably smaller than the loosely-tightening torque. 
   The fully tightening torque, which is larger than the value of the loosely-tightening torque, is required for completely installing the cylinder head cover  1  onto the cylinder head. 
   The disposition and arrangement of the cylinder head cover  1  in relation to the cylinder head are constantly maintained by manually performing the round bushing provisional assembly step S 1  and the long hollow bushing provisional assembly step S 2 . Then, all locking bolts  9  necessary for the assembling operation of the cylinder head cover  1  through the loosely-tightening step S 4  and the assembling completion step S 5  using an automatic bolt tightening apparatus are coupled at the same time, allowing to rapidly and easily finish the assembling operation of the cylinder head cover  1 . 
   On the other hand,  FIG. 3  illustrates another embodiment of an engine cylinder head cover.  FIG. 3  discloses a cylinder head cover  30  having two or more long hollow bushings  33  each having an oval-shaped pipe hole  31 , whose inner flat edge closely adheres to the shank of the locking bolts  29 , wherein the length of the flat edge is longer than the outer diameter of the shank of the locking bolts  29 . 
   There are two long hollow bushings  33  disposed at the cylinder head cover  30 , wherein the flat edges of each oval-shape pipe hole  31  are perpendicularly installed each other. 
   In order to fasten the two long hollow bushings  33  and the cylinder head cover  30  onto the cylinder head, a plurality of assembling bushings  35  are formed at the cylinder head cover  30  for insertion of the locking bolts  29 . 
   The assembling bushings  35  are designed to absorb deformation and manufacturing defects of the cylinder head cover  30  in relation to the cylinder head by forming a hole having a diameter larger than that of the shank of the locking bolts  29  but smaller than that of the head, as described in the first embodiment. 
   The assembly method of the engine cylinder head cover  30  thus described can be applied in almost the same method as the first embodiment. The only difference is that, in the assembly method thus described, step S 1  is substituted with a step for provisionally assembling the locking bolts  29  using any one of two long hollow bushing  33 . The remaining steps can be initially applied to the assembly method thus described as in the first embodiment. 
   As apparent from the foregoing, there is an advantage in the engine cylinder head cover and assembly method thereof according to the present invention in that the disposition and arrangement of a cylinder head cover in relation to a cylinder head can be constantly maintained by a simplified assembly method. There is also another advantage in that the locking bolts for installing a cylinder head cover onto a cylinder head are assembled more quickly and effectively, thereby contributing to an improved assembly of an engine.