Abstract:
A variable valve lift apparatus that changes a lift of a valve in an engine may include an outer body selectively pivoting based on rotation of a cam, having a first end configured to be connected with a valve and a second end mounted with a pivot shaft, and having an internal space formed in the outer body, an inner body pivoting based on rotation of the cam, disposed in the internal space of the outer body, and having a first end rotatably connected to the first end of the outer body, a connecting shaft disposed through the first end of the outer body and the first end of the inner body and connecting the outer body and the inner body to each other, and a lost motion spring having a portion fixed to the outer body and another portion fixed to the inner body.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Korean Patent Application No. 10-2014-0158773 filed Nov. 14, 2014, the entire contents of which is incorporated herein for all purposes by this reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a variable valve lift apparatus. More particularly, the present invention relates to a three-point supported variable valve lift apparatus that is supported on two valves and one hydraulic lash adjuster. 
     Description of Related Art 
     In general, internal combustion engines generate power by receiving and burning air and fuel in a combustion chamber. When an intake valve is operated by a camshaft, air is drawn into the combustion chamber with the intake valve open. Further, when an exhaust valve is operated by the camshaft, air is discharged from the combustion chamber with the exhaust valve open. 
     The optimum operation of the intake valve or the exhaust valve depends on the RPM of the engine. That is, appropriate timing for lifting or opening/closing the valves is controlled on the basis of the RPM of the engine. In order to appropriately operate valves in accordance with the RPM of an engine, as described above, a VVL (Variable Valve Lift) apparatus that operates valves at different lifts in accordance with the RPM of an engine has been studied. As an example of the variable valve lift apparatus, there is an apparatus that includes a plurality of cams on a camshaft for operating valves at different lifts, and is operated such that the cams for operating the valves are selected in accordance with circumstances. 
     However, when a plurality of cams is provided on a camshaft, a configuration for switching the cams to operate an intake valve or an exhaust valve is complicated and there may be interference between components. On the other hand, when a plurality of cams is independently operated to prevent interference between components, components for operating the cams are additionally required, so the manufacturing cost may be increased. 
     The above information disclosed in this Background section is only 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. 
     BRIEF SUMMARY 
     Various aspects of the present invention are directed to providing a variable valve lift apparatus having advantages of being able to change valve lifts with one cam, capable of deactivating a cylinder by changing a valve lift, and a variable valve lift apparatus that more efficiently uses a space and has improved dynamic characteristics, even changing lifts of two valves. 
     According to various aspects of the present invention, a variable valve lift apparatus that changes a lift of a valve in an engine may include an outer body selectively pivoting based on rotation of a cam, having a first end configured to be connected with a valve and a second end mounted with a pivot shaft, and having an internal space formed in the outer body, an inner body pivoting based on rotation of the cam, disposed in the internal space of the outer body, and having a first end rotatably connected to the first end of the outer body, a connecting shaft disposed through the first end of the outer body and the first end of the inner body and connecting the outer body and the inner body to each other, and a lost motion spring having a portion fixed to the outer body and another portion fixed to the inner body, in which the inner body may be configured to pivot with the outer body on a pivot shaft of the outer body while being selectively fixed to the outer body, or configured to pivot on the connecting shaft while being selectively detached from the outer body, and the lost motion spring returns the inner body that has pivoted on the connecting shaft relative to the outer body. 
     The variable valve lift apparatus may further include a roller that is disposed in an internal space of the inner body, is rotatably connected to the inner body, and is in rolling contact with the cam so that the inner body pivots with rotation of the cam. 
     A stopper of the inner body that protrudes to be locked to the second end of the outer body when the inner body is returned by the lost motion spring after pivoting may be formed at a second end of the inner body. 
     A portion of the lost motion spring may extend without interference with the inner body and may be fixed to the first end of the outer body. 
     Valve contact portions that protrude to both sides in a width direction of the outer body and are configured to come in contact with a valve may be formed at the first end of the outer body. 
     A hydraulic lash adjuster may be disposed at the second end of the outer body, and the outer body may be configured to be supported at three points by two valves being in contact with the valve contact portions at both sides and the hydraulic lash adjuster. 
     The outer body and the connecting shaft may be integrally formed, and a portion of the lost motion spring may be fixed to the outer body by being fixed to the connecting shaft. 
     The lost motion spring may be disposed so as to be wound around the connecting shaft. 
     The inner body further may include a stopper, inner connecting holes, roller holes, and a latching pin hole. 
     It is understood that the term “vehicle” or “vehicular” or other similar terms 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., fuel 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 methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view of an exemplary variable valve lift apparatus according to the present invention. 
         FIG. 2  is a rear view of the exemplary variable valve lift apparatus according to the present invention. 
         FIG. 3  is a perspective view showing an outer body coupling hole of the exemplary variable valve lift apparatus according to the present invention. 
         FIG. 4  is a perspective view of an inner body of the exemplary variable valve lift apparatus according to the present invention. 
     
    
    
     It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
       FIG. 1  is a top plan view of a variable valve lift apparatus according to various embodiments of the present invention, and  FIG. 2  is a rear view of the variable valve lift apparatus according to various embodiments of the present invention. 
     As shown in  FIG. 1  and  FIG. 2 , a variable valve lifting apparatus according to various embodiments of the present invention includes an outer body  10 , an inner body  20 , a roller  30 , a connecting shaft  40 , and a lost motion spring  50 . 
     The outer body  10  pivots by selectively receiving torque of a camshaft to open/close a valve. A cam is formed or disposed on the camshaft to convert the rotation of the camshaft into the pivot of the outer body  10 . The valve is an intake valve or an exhaust valve. A space  12  is formed through the outer body  10  perpendicularly to the outer body  10 . That is, the outer body  10  has a predetermined length to pivot and has predetermined width and thickness such that the internal space  12  of the outer body  10  is defined. 
     The valve is connected to a first end of the outer body  10  and a pivot shaft is disposed at a second end of the outer body  10 . The internal space  12  of the outer body  10  is open at the first end, so the outer body  10  can generally have a U-shape. 
     In the following description, first ends and second ends of the components disposed on or coupled to the outer body  10  mean portions in the same directions as the first end and the second end of the outer body  10 . 
     The inner body  20  is disposed in the internal space  12  of the outer body  10 . A first end of the inner body  20  is rotatably coupled to the first end of the outer body  10 . Further, it pivots by receiving torque of the camshaft to selectively open/close a valve. A space is formed through the inner body  20 , perpendicular to the inner body  20 . That is, the inner body  20  has a predetermined length to pivot and has predetermined width and thickness such that the internal space  24  of the inner body  20  is defined. 
     The roller  30  is disposed in the internal space  24  of the inner body  20 . The roller  30  is rotatably coupled to the inner body  20 . The roller  30  is in rolling contact with the cam to convert the rotation of the camshaft into the pivot of the outer body  10  or the inner body  20 . 
     The connecting shaft  40  connects the first end of the outer body  10  with the first end of the inner body  20  such that they can rotate. That is, the inner body  20  can rotate about the connecting shaft  40  relative to the outer body  10 . The first end of the outer body  10  connected with the inner body  20  by the connecting shaft  40  is referred to as an outer connecting portion  14 , and the first end of the inner body  20  connected with the outer body  10  by the connecting shaft is referred to as an inner connecting portion  22 . 
     Valve contact portions  16  protruding from the outer connecting portion  14  are formed at the first end of the outer body  10 . The valve contact portions  16  push the valve with the pivot of the outer body  10  in contact with the valve or a valve door for opening/closing the valve. 
     The outer connecting portions  14  are formed at both sides of the internal space  12  in the width direction of the outer body  10  and the valve contact portions  16  protrude from the outer connecting portions  14  at both sides to close two valves, respectively. A seat where a hydraulic lash adjuster (HLA) is seated is formed at the second end of the outer connecting portion  14 . That is, the variable valve lift apparatus according to various embodiments of the present invention is three-point supported variable valve lift apparatus supported by two valves and one hydraulic lash adjuster. The hydraulic lash adjuster, a device that supplies hydraulic pressure to operate a variable valve lift apparatus and allows a valve lifter to move in close contact with a cam, is well known to those skilled in the art, so the detailed description is not provided. 
     When the inner body  20  is fixed to the outer body  10 , the inner body  20  and the outer body  10  pivot together on the pivot shaft of the outer body  10  by rotation of the cam being in rolling contact with the roller  30 . When the inner body  20  is unfixed from the outer body  10 , only the inner body  20  pivots on the connecting shaft  40  by rotation of the cam being in rolling contact with the roller  30 . Selectively fixing and unfixing the inner body to the outer body  10 , for example, with a latching pin, are well known to those skilled in the art, so the detailed description is not provided. 
     The lost motion spring  50  returns the inner body  20  that has pivoted relative to the outer body  10  by pivoting when the inner body  20  is unfixed from the outer body  10   
     The lost motion spring  50  is wound around the connecting shaft  40 . 
     An outer fixing portion  52  fixed to the outer body  10  and an inner fixing portion  54  fixed to the inner body  20  are formed on the lost motion spring  50 . The outer fixing portion  52  may be fixed to the outer connecting portion  14  of the outer body  10 , extending in the width direction of the outer body  10  in order to avoid interference with the inner body  20 . 
     Since the lost motion spring  50  is wound around the connecting shaft  40 , it can be easily fixed to the inner body and there is no need for a specific component for connecting the lost motion spring  50  to the outer body  10  or the inner body  20 . For example, when the lost motion spring  50  is wound around the pivot shaft of the outer body  10  and a portion of the lost motion spring  50  is connected to the inner body  20  through the rotational shaft of the roller  30 , the length of the rotational shaft of the roller  30  may be increased and a specific component may be required to wind the lost motion spring  50  around the pivot shaft of the outer body  10 . 
       FIG. 3  is a perspective view showing an outer body coupling hole according to various embodiments of the present invention. 
     As shown in  FIG. 1  to  FIG. 3 , the connecting shaft  40  is disposed through the outer connecting portions  14  of the outer body  10 . That is, outer connecting holes  18  are formed at the outer connecting portions  14  of the outer body  10  to receive the connecting shaft  40 . Since the valve contact portions  16  protrude from the outer connecting portions  14  to both lateral sides of the outer body  10 , the entire width of the outer body  10  except for the valve contact portions  16  and the length of the connecting shaft  40  may be decreased. 
       FIG. 4  is a perspective view of the inner body according to various embodiments of the present invention. 
     As shown in  FIG. 4 , the inner body  20  further has a stopper  26 , inner connecting holes  28 , roller holes  25 , and a latching pin hole  29 . 
     The stopper  26  protrudes from the second end of the inner body  20 , and it locks the second end of the inner body  20  to the second end of the outer body  10  when the inner body  20  is returned by the lost motion spring  50 . Accordingly, the inner body  20  can be stably returned by the lost motion spring  50 . 
     The inner connecting holes  28  are formed so that the connecting shaft  40  passing through the inner connecting portions  22  is inserted therein, and the roller holes  25  are formed so that the rotational shaft of the roller  30  is inserted therein. That is, the inner connecting holes  28  and the roller holes  25  are formed in the width direction of the inner body  20 . 
     The latching pin hole  29  is formed so that a fixing member, which selectively fixes the inner body  20  to the outer body  10 , such as a latching pin, is inserted therein. As the fixing member is inserted into the latching pin  29  by hydraulic pressure from the hydraulic lash adjuster, the inner body  20  can be fixed to the outer body  10 . 
     Meanwhile, it is possible to precisely optimize a tolerance between the fixing member and the latching pin hole  29  by machining the outer body  10  and the inner body  20  on the basis of the stopper  26 . 
     As described above, according to various embodiments of the present invention, two valve lifts are changed by the roller  30  moving in rolling contact with one cam, such that a loss of power due to friction on the cam can be minimized. Further, since only the inner body  20  pivots with the roller  30  being in rolling contact with the cam, a cylinder can be deactivated. Further, since the lost motion spring  50  is disposed at the valve contact portions  16 , the length of the connecting shaft  40  can be reduced and the entire size of the variable valve lift apparatus decreases, so the weight and manufacturing cost can be reduced and the dynamic characteristics can be improved. 
     For convenience in explanation and accurate definition in the appended claims, the terms “upper” or “lower”, “inner” or “outer” and etc. are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
     The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.