Patent Publication Number: US-9404398-B2

Title: Continuously variable valve timing device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority of Korean Patent Application Number 10-2013-0137066 filed on Nov. 12, 2013, the entire contents of which application are incorporated herein for all purposes by this reference. 
     BACKGROUND 
     (a) Field of Invention 
     The present invention relates to a continuously variable valve timing device, and more particularly, to a continuously variable valve timing device that maintains internal pressure of an electric variable valve timing mechanism cover partitioned by a seal ring, at atmospheric pressure to preserve function and durability of the seal ring, and prevent malfunction of an electricity driven motor. 
     (b) Description of Related Art 
     In general, an internal combustion engine is an apparatus that generates power by suctioning air and fuel from the exterior of a vehicle, and combusting fuel in a combustion chamber, and has an intake valve configured to suction air and fuel into the combustion chamber, and an exhaust valve configured to discharge explosion gas combusted in the combustion chamber, and the intake and exhaust valves are opened and closed in conjunction with rotation of a camshaft. 
     Optimum opening and closing timing of the intake and exhaust valves may be varied based on an engine revolution per minute (RPM), an engine load, and the like. Therefore, a technology, which properly controls valve timing based on a driving state of the engine by having a displacement within a set range without definitely setting the rotation of the camshaft based on rotation of a crankshaft, has been developed, and this technology is referred to as a variable valve timing (VVT) device. In addition, the continuously variable valve timing (CVVT) device is a type of variable valve timing device, and has a configuration that may control valve timing with an arbitrary value within a predetermined displacement. 
     The continuously variable valve timing device includes a cam sprocket connected to the camshaft to rotate the camshaft, an electric variable valve timing mechanism connected with the cam sprocket and driven by a motor, a chain cover configured to protect the cam sprocket and a chain system from foreign substances, an electric variable valve timing mechanism cover configured to protect the electric variable valve timing mechanism from foreign substances, a seal ring mounted between the electric variable valve timing mechanism and the electric variable valve timing mechanism cover, and partitions an internal space of the electric variable valve timing mechanism cover to block oil from flowing toward a brush of a connector installed on a slip ring of the electric variable valve timing mechanism and the electric variable valve timing mechanism cover, and a rubber plug mounted in a mounting aperture formed within the electric variable valve timing mechanism cover to prevent an inflow of foreign substances such as moisture and dust. 
     However, in the aforementioned continuously variable valve timing device in the related art, pressure in the internal space of the electric variable valve timing mechanism cover may be varied due to a variation in temperature of the engine and due to an oil seal structure that seals a contact portion of a rotating body, a seal line of the seal ring may be damaged when pressure increases due to the variation in pressure, durability such as an increase in frictional force of the oil seal may occur pressure is reduced, oil may flow from the engine side through a gap in the damaged seal ring, and as a result, a malfunction may occur on the motor that drives the electric variable valve timing mechanism. 
     The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY 
     The present invention provides a continuously variable valve timing device configured to maintain pressure in an internal space of an electric variable valve timing mechanism cover at atmospheric pressure using a pressure maintaining device, to preserve a function and durability of a seal ring, thereby continuously preventing oil from leaking to the internal space of the electric variable valve timing mechanism cover. 
     An exemplary embodiment of the present invention provides a continuously variable valve timing device that may include: a cam sprocket connected with a camshaft having a plurality of cams to rotate the camshaft; an electric variable valve timing mechanism connected with the cam sprocket, and driven by an electric motor; a chain cover configured to protect the cam sprocket and a chain system from foreign substances; an electric variable valve timing mechanism cover configured to protect the electric variable valve timing mechanism from foreign substances; and a seal ring that partitions an internal space between the electric variable valve timing mechanism and the electric variable valve timing mechanism cover. 
     The continuously variable valve timing device may include: a pressure maintaining device mounted within the electric variable valve timing mechanism cover to maintain pressure formed within the internal space of the electric variable valve timing mechanism cover at atmospheric pressure. 
     In addition, the pressure maintaining device may include: a plug mounted within a mounting aperture formed within the electric variable valve timing mechanism cover, and may have a circulation aperture formed at a substantial center of the plug to allow gas to flow in and out, and an installation space formed at an inner side of the plug; a film member may be mounted within the installation space of the plug to allow gas to pass therethrough; and a support member may be fitted into the installation space of the plug to support the film member, and may have an aperture formed at a substantial center thereof. 
     In addition, the plug may include: a circular body portion having a circulation aperture formed at a substantial center thereof; and an insertion portion extended inward along an outer circumferential surface of the body portion to be fitted into an inner circumferential surface of the mounting aperture within the electric variable valve timing mechanism cover, and may form the installation space. The insertion portion may have a fitting groove formed around an outer circumferential surface of the insertion portion to be fitted into the inner circumferential surface of the mounting aperture. Further, the film member may be made of a material such as polytetrafluoroethylene that allows gas to pass therethrough. 
     The exemplary embodiment of the present invention may be configured to maintain pressure within the internal space of the electric variable valve timing mechanism cover at atmospheric pressure using the pressure maintaining device to maintain a function of the seal ring and preserve durability of the seal ring, and prevent oil from flowing toward the contact portion of the brush of the connector, which may be installed on the slip ring of the electric variable valve timing mechanism and the electric variable valve timing mechanism cover, using the seal ring durability of which may be maintained, thereby improving operational reliability of the electric variable valve timing mechanism. In addition, pressure within the internal space of the electric variable valve timing mechanism cover may be maintained using the pressure maintaining device, and foreign substances such as moisture and dust may be blocked from flowing into the system, thereby preventing malfunction of the electric variable valve timing mechanism. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exemplary partially cut-away view of a continuously variable valve timing device according to an exemplary embodiment of the present invention; 
         FIG. 2  is an exemplary detailed view of a pressure maintaining device applied to the continuously variable valve timing device according to the exemplary embodiment of the present invention; and 
         FIG. 3  is an exemplary partially cut-away view of the pressure maintaining device applied to the continuously variable valve timing device according to the exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTIONS 
     It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about.” 
     Hereinafter, an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. The size and thickness of each component illustrated in the drawings are arbitrarily shown for understanding and ease of description, but the present invention is not limited thereto. Thicknesses of several portions and regions are exaggerated for clarity. In addition, a part irrelevant to the description will be omitted to clearly describe the exemplary embodiment of the present invention. 
       FIG. 1  is an exemplary partially cut-away perspective view of a continuously variable valve timing device according to an exemplary embodiment of the present invention. Referring to  FIG. 1 , a continuously variable valve timing device  1  according to an exemplary embodiment of the present invention may include a cam sprocket  3 , an electric variable valve timing mechanism  5 , a chain cover  7 , an electric variable valve timing mechanism cover  9 , and a seal ring  15 . 
     The cam sprocket  3  may be connected to a camshaft (not illustrated), which may have a plurality of cams (not illustrated), to rotate the camshaft, and the electric variable valve timing mechanism  5  may be connected with the cam sprocket  3 . The chain cover  7  may be configured to protect the cam sprocket  3  from foreign substances such as moisture and dust. The electric variable valve timing mechanism cover  9  may be configured to protect the electric variable valve timing mechanism  5  from foreign substances such as moisture and dust. The seal ring  15  may be mounted between an outer circumferential surface of the electric variable valve timing mechanism  5  and an inner circumferential surface of the electric variable valve timing mechanism cover  9  to prevent oil from flowing toward a contact portion of a brush  10  of a connector installed on a slip ring  6  of the electric variable valve timing mechanism  5  and the electric variable valve timing mechanism cover  9 , and may partition an internal space  13  between an inner surface of the electric variable valve timing mechanism cover  9  and the electric variable valve timing mechanism  5 . 
     The continuously variable valve timing device  1  may be configured to maintain pressure formed within the internal space  13  of the electric variable valve timing mechanism cover  9  at about atmospheric pressure to maintain a function of the seal ring  15  and preserve durability of the seal ring  15 , and may be configured to prevent oil from flowing toward the contact portion of the brush  10  of the connector installed on the slip ring  6  of the electric variable valve timing mechanism  5  and the electric variable valve timing mechanism cover  9 , using the seal ring  15 , thereby improving operational reliability of the electric variable valve timing mechanism  5  that is driven by electricity. 
       FIG. 2  is an exemplary detailed view of a pressure maintaining device applied to the continuously variable valve timing device according to the exemplary embodiment of the present invention, and  FIG. 3  is an exemplary partially cut-away perspective view of the pressure maintaining device applied to the continuously variable valve timing device according to the exemplary embodiment of the present invention. 
     Referring to  FIGS. 2 and 3 , the continuously variable valve timing device  1  according to the exemplary embodiment of the present invention may further include a pressure maintaining device  20 . The pressure maintaining device  20  may be mounted within the electric variable valve timing mechanism cover  9  to maintain pressure formed within the internal space  13  of the electric variable valve timing mechanism cover  9  at about atmospheric pressure. The pressure maintaining device  20  may include a plug  30 , a film member  40 , and a support member  50 . 
     The plug  30  may be mounted within a mounting aperture  11  formed within the electric variable valve timing mechanism cover  9 , and may include a circulation aperture  31  formed at about a center of the plug  30  to allow gas such as air to flow in and out of the system, and an installation space  32  formed at an inner side of the plug  30 , and the plug  30  may be made of rubber. In particular, the plug  30  may include a body portion  33  and an insertion portion  34 . The circulation aperture  31  may be formed at about a center of the body portion  33 , and the body portion  33  may have a substantially circular shape. 
     The insertion portion  34  may be extended inward along an outer circumferential surface of the body portion  33  to be fitted into an inner circumferential surface of the mounting aperture  11  of the electric variable valve timing mechanism cover  9 , and may form the installation space  32 . The insertion portion  34  may include a fitting groove  35  formed around an outer circumferential surface of the insertion portion  34 , to be fitted into the inner circumferential surface of the mounting aperture  11 . In addition, to prevent the support member  50  from being pulled out, the insertion portion  34  may include a catching projection  36  formed at a tip (e.g., an end) of the installation space  32 . The plug  30 , which is described above, may be mounted within the mounting aperture  11  formed in the electric variable valve timing mechanism cover  9  to block foreign substances such as moisture and dust from flowing into the electric variable valve timing mechanism cover  9 , thereby preventing the motor, which drives the electric variable valve timing mechanism  5 , from malfunctioning. 
     In the exemplary embodiment of the present invention, the film member  40  may be mounted within the installation space  32  of the plug  30  to allow gas such as air to pass through the film member  40 . In other words, the film member  40  may be configured to maintain pressure formed within the internal space  13  of the electric variable valve timing mechanism cover  9  at about atmospheric pressure to preserve durability of the seal ring  15 , and prevent oil in the engine from flowing to the outer circumferential surface of the electric variable valve timing mechanism  5  using the seal ring  15 , thereby improving operational reliability of the electric variable valve timing mechanism  5 . 
     The film member  40  may be made of a material such as polytetrafluoroethylene that allows gas to pass therethrough. In particular, the polytetrafluoroethylene (PTFE) is non-flammable fluororesin which belongs to organic polymer materials that are formed by large molecules made by chemically combining a plurality of small molecules (monomers) in chain conformation or in a network structure, and the polytetrafluoroethylene is resistant to heat, and has an extremely low friction coefficient, and excellent chemical resistance. In addition, the polytetrafluoroethylene is resistant against many chemicals, has a smooth surface, and maintains physical properties within a wide temperature range (e.g., about −270 to 250° C.). Owing to the aforementioned properties, the polytetrafluoroethylene may be used as a protective film for gaskets, bearings, inner walls of containers and pipes, components of valves and pumps used in a corrosive environment, cooking utensils, saw blades, and other products. Since the aforementioned polytetrafluoroethylene is a publicly known technology that is widely known to those skilled in the art, a more detailed description thereof will be omitted below. 
     The support member  50  may be fitted into the installation space  32  of the plug  30  to support the film member  40 , and an aperture  51  may be formed at a substantially center portion of the support member  50 . Particularly, the aperture  51  may have a larger diameter than the circulation aperture  31 . In other words, as illustrated in  FIG. 3 , in the continuously variable valve timing device  1  according to the exemplary embodiment of the present invention, the pressure maintaining device  20  may be mounted within the mounting aperture  11  of the electric variable valve timing mechanism cover  9  to repeatedly circulate air outside the electric variable valve timing mechanism cover  9  and air inside the electric variable valve timing mechanism cover  9  through the circulation aperture  31  of the plug  30 , the film member  40 , and the aperture  51  of the support member  50 , and maintain pressure formed in the internal space  13  of the electric variable valve timing mechanism cover  9  at about atmospheric pressure, such that a sealing function and durability of the seal ring  15  may be preserved, and oil in the engine may be prevented from flowing toward the contact portion of the brush  10  of the connector installed on the slip ring  6  of the electric variable valve timing mechanism  5  and the electric variable valve timing mechanism cover  9 , using the seal ring  15 , thereby improving operational reliability of the motor that drives the electric variable valve timing mechanism  5 . 
     Therefore, the continuously variable valve timing device  1  according to the exemplary embodiment of the present invention may be configured to maintain pressure within the internal space  13  of the electric variable valve timing mechanism cover  9  at about atmospheric pressure using the pressure maintaining device  20  to preserve a function and durability of the seal ring  15 , and prevent oil in the engine from flowing toward the contact portion of the brush  10  of the connector installed on the slip ring  6  of the electric variable valve timing mechanism  5  and the electric variable valve timing mechanism cover  9 , using the seal ring  15 , thereby improving operational reliability of the motor that drives the electric variable valve timing mechanism  5 . In addition, pressure within the internal space  13  of the electric variable valve timing mechanism cover  9  may be maintained using the pressure maintaining device  20 , and foreign substances such as moisture and dust may be blocked from flowing in, thereby preventing malfunction of the electric variable valve timing mechanism  5 . 
     While this invention has been described in connection with what is presently considered to be exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 
     DESCRIPTION OF SYMBOLS 
     
         
         
           
               1  . . . Continuously variable valve timing device 
               3  . . . Cam sprocket 
               5  . . . Electric variable valve timing mechanism 
               6  . . . Slip ring 
               7  . . . Chain cover 
               9  . . . Electric variable valve timing mechanism cover 
               10  . . . Brush 
               11  . . . Mounting aperture 
               13  . . . Internal space 
               15  . . . Seal ring 
               20  . . . Pressure maintaining device 
               30  . . . Plug 
               31  . . . Circulation aperture 
               32  . . . Installation space 
               33  . . . Body portion 
               34  . . . Insertion portion 
               35  . . . Fitting groove 
               36  . . . Catching projection 
               40  . . . Film member 
               50  . . . Support member 
               51  . . . Aperture