Patent Publication Number: US-11643992-B2

Title: Plastic molded article

Description:
BACKGROUND 
     1. Field 
     The present disclosure relates to a plastic molded article that includes a base having a main surface, a first tubular portion protruding from the main surface, and a second tubular portion protruding from the main surface and having an inner diameter smaller than that of the first tubular portion. The base, the first tubular portion, and the second tubular portion are integrally molded of plastic. 
     2. Description of Related Art 
     One example of such plastic molded articles is a cylinder head cover for an internal combustion engine (for example, refer to Japanese Laid-Open Patent Publication No. 2014-122601). The cylinder head cover disclosed in the publication includes a plug cylinder, into which an insertion portion of an ignition coil is inserted, and a receiving portion, in which a nut is embedded by insert molding. The plug cylinder and the receiving portion are integrally molded of plastic. A bolt for fixing the ignition coil to the cylinder head cover is threaded into the nut. 
     When such a plastic cylinder head cover is molded, molding shrinkage occurs. In the case of the cylinder head cover of the above-described publication, the plug cylinder and the receiving portion shrink toward the respective central axes. The inner diameter of the plug cylinder is larger than the inner diameter of the receiving portion. Accordingly, the receiving portion is pulled toward the plug cylinder due to the molding shrinkage of the plug cylinder. This may displace the receiving portion, that is, the nut, from the proper position. As a result, after the insertion portion of the ignition coil is inserted into the plug cylinder, it may be impossible to thread the bolt into the nut in the receiving portion. 
     The above-described drawbacks are not limited to plastic cylinder head covers, but may also be found in any plastic molded article that includes a base having a main surface, a first tubular portion protruding from the main surface, and a second tubular portion protruding from the main surface and having an inner diameter smaller than that of the first cylinder, and in which the base, the first tubular portion, and the second tubular portion are integrally molded of plastic. 
     SUMMARY 
     Accordingly, it is an objective of the present disclosure to provide a plastic molded article that improves dimensional accuracy in a favorable manner. 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
     In a general aspect, a plastic molded article includes a base having a main surface, a first tubular portion protruding from the main surface, a second tubular portion, and a pair of ribs. The second tubular portion protrudes from the main surface and has an inner diameter smaller than that of the first tubular portion. The ribs protrude from the main surface and connect an outer circumferential surface of the first tubular portion and an outer circumferential surface of the second tubular portion to each other. The base, the first tubular portion, the second tubular portion, and the ribs are integrally molded of plastic. The ribs are located on opposite sides of an imaginary plane that includes a central axis of the first tubular portion and a central axis of the second tubular portion. 
     Other features and aspects will be apparent from the following detailed description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a plan view of a plastic molded article according to one embodiment, illustrating a cylinder head cover for an internal combustion engine. 
         FIG.  2    is a bottom view of the embodiment, mainly illustrating a first tubular portion, a second tubular portion, and ribs. 
         FIG.  3    is a cross-sectional view taken along line  3 - 3  of  FIG.  1   . 
         FIG.  4    is a cross-sectional view taken along line  4 - 4  of  FIG.  3   ; 
     
    
    
     Throughout the drawings and the detailed description, the same reference numerals refer to the same elements. The drawings may not be to scale, and the relative size, proportions, and depiction of elements in the drawings may be exaggerated for clarity, illustration, and convenience. 
     DETAILED DESCRIPTION 
     This description provides a comprehensive understanding of the methods, apparatuses, and/or systems described. Modifications and equivalents of the methods, apparatuses, and/or systems described are apparent to one of ordinary skill in the art. Sequences of operations are exemplary, and may be changed as apparent to one of ordinary skill in the art, with the exception of operations necessarily occurring in a certain order. Descriptions of functions and constructions that are well known to one of ordinary skill in the art may be omitted. 
     Exemplary embodiments may have different forms, and are not limited to the examples described. However, the examples described are thorough and complete, and convey the full scope of the disclosure to one of ordinary skill in the art. 
     A plastic molded article according to one embodiment will now be described with reference to  FIGS.  1  to  4   . In the present embodiment, the plastic molded article of the present disclosure is a cylinder head cover  10  configured to be attached to the cylinder head of an in-line four cylinder internal combustion engine. 
     As shown in  FIG.  1   , the cylinder head cover  10  includes a top wall  11 , which is rectangular in a plan view, and a peripheral wall  12 , which is provided at the periphery of the top wall  11 . The top wall  11  and the peripheral wall  12  are integrally molded of plastic. The top wall  11  corresponds to the base according to the present disclosure. The peripheral wall  12  includes attachment portions  13  at the outer peripheral edge. The attachment portions  13  receive bolts for attaching the cylinder head cover  10  to a cylinder head (not shown). 
     The top wall  11  includes a back face  11   a , which corresponds to the main surface of the base according to the present disclosure (refer to  FIGS.  2  and  3   ). 
     As shown in  FIGS.  2  and  3   , the top wall  11  includes first tubular portions  20  and second tubular portions  30 , which are cylindrical and protrude from the back face  11   a.    
     The present embodiment includes four first tubular portions  20  and four second tubular portions  30 . 
     Each first tubular portion  20  defines an insertion hole  21 , into which an insertion portion  62  of an ignition coil  60  is inserted. 
     The inner diameter of the second tubular portions  30  is smaller than the inner diameter of the first tubular portions  20 . The protruding amount of each second tubular portion  30  from the back face  11   a  of the top wall  11  is greater than the protruding amount of each first tubular portion  20  from the back face  11   a.    
     Each second tubular portion  30  includes a nut  70 , which is embedded by insert molding. Each second tubular portion  30  defines a fastening hole  31 . A bolt  71  for fixing a case  61  of the corresponding ignition coil  60  to the cylinder head cover  10  is fastened to each fastening hole  31 . 
     Each bolt  71  corresponds to the fastening member according to the present disclosure. 
     &lt;First Ribs  40 &gt; 
     The cylinder head cover  10  includes four pairs of first ribs  40 , which protrude from the back face  11   a  of the top wall  11  as shown in  FIGS.  2  to  4   . For the illustrative purposes, the following describes one of the four pairs of first ribs  40  and the related structures. The pair of first ribs  40  connects an outer circumferential surface  22  of the first tubular portion  20  to an outer circumferential surface  32  of the second tubular portion  30 . 
     As shown in  FIGS.  2  to  4   , the two first ribs  40  are located on the opposite sides of an imaginary plane L, which includes a central axis C 1  of the first tubular portion  20  and a central axis C 2  of the second tubular portion  30 . 
     As shown in  FIG.  2   , the two first ribs  40  extend arcuately at positions outward of a pair of external common tangents T of the outer circumferential surface  22  of the first tubular portion  20  and the outer circumferential surface  32  of the second tubular portion  30 . Outer surfaces  41  of the pair of first ribs  40 , a part  23  of the outer circumferential surface  22  of the first tubular portion  20 , and a part  33  of the outer circumferential surface  32  of the second tubular portion  30  form an annular shape. That is, the two first ribs  40  have a symmetrical shape with respect to the imaginary plane L, which includes the central axis C 1  of the first tubular portion  20  and the central axis C 2  of the second tubular portion  30 . 
     As shown in  FIG.  3   , the protruding amount of each first rib  40  from the back face  11   a  of the top wall  11  increases from the first tubular portion  20  toward the second tubular portion  30 . 
     &lt;Second Rib  50 &gt; 
     The cylinder head cover  10  includes four second ribs  50 , which protrude from the back face  11   a  of the top wall  11  as shown in  FIGS.  2  to  4   . For the illustrative purposes, the following describes one of the four second ribs  50  and the related structures. The second rib  50  is located between the two first ribs  40  and connects the outer circumferential surface  22  of the first tubular portion  20  and the outer circumferential surface  32  of the second tubular portion  30  to each other. 
     As shown in  FIGS.  2  and  4   , the second rib  50  extends along the imaginary plane L. More specifically, the second rib  50  is disposed on the imaginary plane L. 
     The protruding amount of the second rib  50  from the back face  11   a  of the top wall  11  increases from the first tubular portion  20  toward the second tubular portion  30 . 
     An operation of the present embodiment will now be described. 
     When molding shrinkage occurs, the force pulling the second tubular portion  30  toward the first tubular portion  20  is dispersed by the pair of first ribs  40  and the second rib  50 . The second tubular portion  30  is therefore prevented from being pulled toward the first tubular portion  20 . Particularly, the two first ribs  40  are located on the opposite sides of the imaginary plane L, which includes the central axis C 1  of the first tubular portion  20  and the central axis C 2  of the second tubular portion  30 . Thus, the second tubular portion  30  is prevented from collapsing toward one of the two first ribs  40  also from collapsing toward the other first rib  40 . 
     The present embodiment has the following advantages. 
     (1) The cylinder head cover  10  includes the pairs of first ribs  40 . Each pair of first ribs  40  protrudes from the back face  11   a  and connects the outer circumferential surface  22  of the corresponding first tubular portion  20  and the outer circumferential surface  32  of the corresponding second tubular portion  30  to each other. The two first ribs  40  are located on the opposite sides of the imaginary plane L, which includes the central axis C 1  of the first tubular portion  20  and the central axis C 2  of the second tubular portion  30 . 
     This configuration operates in the above described manner and thus improves the dimensional accuracy of the cylinder head cover  10 . 
     Also, the above-described configuration reduces the increase in the size of the cylinder head cover  10  as compared to a case in which ribs are disposed to extend radially from the outer circumferential surface  32  of the second tubular portion  30 . 
     This improves the dimensional accuracy in a favorable manner. 
     (2) The protruding amount of the first ribs  40  from the back face  11   a  increases from the first tubular portion  20  toward the second tubular portion  30 . 
     A section of each first rib  40  that is close to the first tubular portion  20  receives a pulling force toward the first tubular portion  20  due to the molding shrinkage of the first tubular portion  20 . On the other hand, a section of each first rib  40  that is close to the second tubular portion  30  receives a pulling force toward the second tubular portion  30  due to the molding shrinkage of the second tubular portion  30 . 
     In the above-described configuration, the protruding amount of each first rib  40  from the back face  11   a  increases toward the second tubular portion  30 . Thus, the protruding amount of the section of each first rib  40  that is close to the second tubular portion  30  is greater than the protruding amount of the section close to the first tubular portion  20 . This increases the pulling force toward the second tubular portion  30  effectively in the first rib  40 . Accordingly, the second tubular portion  30  is prevented from being pulled toward the first tubular portion  20  due to molding shrinkage more effectively. 
     (3) The two first ribs  40  have a symmetrical shape with respect to the imaginary plane L, which includes the central axis C 1  of the first tubular portion  20  and the central axis C 2  of the second tubular portion  30 . 
     This configuration prevents the second tubular portion  30  from collapsing toward one of the two first ribs  40 , and prevents the second tubular portion  30  from collapsing toward the other first rib  40  effectively. This further improves the dimensional accuracy of the cylinder head cover  10 . 
     (4) The two first ribs  40  extend arcuately at positions outward of the pair of external common tangents T of the outer circumferential surface  22  of the first tubular portion  20  and the outer circumferential surface  32  of the second tubular portion  30 . 
     This configuration disperses the pulling force that acts on the pair of first ribs  40  due to molding shrinkage in a favorable manner. Accordingly, the second tubular portion  30  is prevented from being pulled toward the first tubular portion  20  due to molding shrinkage effectively. 
     In the above-described configuration, the outer surfaces  41  of the pair of first ribs  40 , the part  23  of the outer circumferential surface  22  of the first tubular portion  20 , and the part  33  of the outer circumferential surface  32  of the second tubular portion  30  form an annular shape. This increases the stiffness of the entire cylinder head cover  10 . 
     (5) The cylinder head cover  10  includes the second ribs  50 , each of which protrudes from the back face  11   a  between the corresponding two first ribs  40 . The second rib  50  connects the outer circumferential surface  22  of the first tubular portion  20  and the outer circumferential surface  32  of the second tubular portion  30  to each other. The second rib  50  is disposed on the imaginary plane L. 
     This configuration prevents the second tubular portion  30  from being pulled toward the first tubular portion  20  due to molding shrinkage more effectively. Particularly, since the second rib  50  is disposed on the imaginary plane L, the second tubular portion  30  is prevented from being pulled toward the first tubular portion  20  in a favorable manner. This further improves the dimensional accuracy of the cylinder head cover  10 . 
     Also, since the second rib  50  is disposed between the two first ribs  40  in the above-described configuration, the second rib  50  does not increase the size of the cylinder head cover  10 . 
     (6) Each second tubular portion  30  defines a fastening hole  31 , to which the corresponding bolt  71  is fastened. 
     This improves the dimensional accuracy of the cylinder head cover  10 , so that the bolt  71  is easily and properly fastened to the second tubular portion  30 . 
     &lt;Modifications&gt; 
     The present embodiment may be modified as follows. The present embodiment and the following modifications can be combined as long as the combined modifications remain technically consistent with each other. 
     The number of the first tubular portions  20  and the number of the second tubular portions  30  are not limited to four. The number of the first tubular portions  20  and the number of the second tubular portions  30  can be changed in accordance with the number of cylinders of the internal combustion engine in which the cylinder head cover  10  is employed. 
     In place of the bolt  71 , which fixes the ignition coil  60 , a bolt that fixes a sensor mounted on the internal combustion engine may be fastened to the fastening hole  31  defined by the second tubular portion  30 . 
     The second tubular portion  30  is not limited to a portion that defines a fastening hole to which a bolt is fastened, but may be a portion that defines a passage through which fluid flows. 
     The first tubular portion  20  is not limited to a portion that defines the insertion hole  21 , into which the insertion portion  62  of the ignition coil  60  is inserted, as in the above-described embodiment, but may be a portion that defines an insertion hole into which another component is inserted. Also, the first tubular portion  20  does not necessarily need to define an insertion hole, into which a component is inserted, but may define a passage through which fluid flows. 
     The second rib  50  is not limited to be disposed along the imaginary plane L as in the above-described embodiment, but may intersect the imaginary plane L. Also, the protruding amount of the second rib  50  from the back face  11   a  of the top wall  11  may be changed. For example, the protruding amount may be constant between the first tubular portion  20  and the second tubular portion  30 . 
     The second rib  50  may be omitted. 
     The shapes of the pair of first ribs  40  are not limited to the ones in the above-described embodiment, but may be shapes that extend along the external common tangents T and located on the external common tangents T. Also, the two first ribs  40  may be asymmetric with respect to the imaginary plane L. Also, the protruding amount of the first ribs  40  from the back face  11   a  of the top wall  11  may be changed. For example, the protruding amount may be constant between the first tubular portion  20  and the second tubular portion  30 . 
     The plastic molded article is not limited to a cylinder head cover as in the above-described embodiment. That is, the present disclosure can be applied to any plastic molded article that includes a base, a first tubular portion, and a second tubular portion, and in which the base has a main surface, the first tubular portion protrudes from the main surface, the second tubular portion has an inner diameter smaller than that of the first tubular portion, and the base, the first tubular portion, and the second tubular portion are integrally molded of plastic. 
     Various changes in form and details may be made to the examples above without departing from the spirit and scope of the claims and their equivalents. The examples are for the sake of description only, and not for purposes of limitation. Descriptions of features in each example are to be considered as being applicable to similar features or aspects in other examples. Suitable results may be achieved if sequences are performed in a different order, and/or if components in a described system, architecture, device, or circuit are combined differently, and/or replaced or supplemented by other components or their equivalents. The scope of the disclosure is not defined by the detailed description, but by the claims and their equivalents. All variations within the scope of the claims and their equivalents are included in the disclosure.