Abstract:
A variable valve lift apparatus including an inner tappet, an outer tappet surrounding and slidably contacting the inner tappet, and a latching pin slidably inserted into the inner tappet so as to implement a high lift and a low lift by selectively joining the inner tappet and the outer tappet may include a stopper partially inserted into the outer tappet and spaced apart from the latching pin in a movement direction of the latching pin so as to limit movement of the latching pin, and forming a latching pin joining groove in the outer tappet to selectively receive the latching pin, wherein the stopper partially projects to the outside of the outer tappet and is slidably engaged to a cylinder head groove formed to a cylinder head bore to prevent the variable valve lift apparatus from being rotated.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to Korean Patent Application No. 10-2010-0095559 filed in the Korean Intellectual Property Office on Sep. 30, 2010, the entire contents of which is incorporated herein for all purposes by this reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a variable valve lift apparatus, and more particularly, to a variable valve lift apparatus with a stopper that is inserted into an outer tappet to limit movement of a latching pin and projects to the outside of the outer tappet and slides in a cylinder head groove to prevent the variable valve lift apparatus from being rotated. 
         [0004]    2. Description of Related Art 
         [0005]    In general, an internal combustion engine receives fuel and air in a combustion chamber and combusts the fuel and air to form power. An intake valve is actuated by driving a cam shaft at the time of suctioning air and air is suctioned into the combustion chamber while the intake valve is opened. Further, an exhaust valve is actuated by driving the cam shaft and air is discharged from the combustion chamber while the exhaust valve is opened. 
         [0006]    However, an optimal operation of the intake valve/exhaust valve depends on a rotational velocity of an engine. That is, an appropriate lift or valve opening/closing time depends on the rotational velocity of the engine. As such, in order to implement the appropriate valve operation depending on the rotational velocity of the engine, a variable valve lift (VVL) apparatus in which a cam driving the valve is designed to have a plurality of shapes or the valve is implemented to operate in different lifts depending on the number of rotations of the engine has been researched. 
         [0007]      FIG. 9  is a cross-sectional view of a variable tappet in a high lift mode of a known variable valve lift apparatus and  FIG. 10  is a cross-sectional view of a variable tappet in a low lift mode of a known variable valve lift apparatus. 
         [0008]    First, in the high lift mode, oil pressure is supplied to a hydraulic chamber  240  formed in an outer tappet  100  and a plunger  350  pushes a latching pin  310  by the supplied oil pressure. Therefore, as shown in  FIG. 9 , the latching pin  310  is inserted into a latching pin joining groove  340  and an inner tappet  200  and the outer tappet  100  are joined to each other. 
         [0009]    In this case, a high cam  12  is joined to a cam shaft  10 , such that the high cam  12  presses the outer tappet  100  by rotation of the cam shaft  10 , and as a result, the outer tappet  100  and the inner tappet  200  integrally move up and down. That is, high lift is executed by rotational movement of the high cam  12 . 
         [0010]    On the contrary, in the low lift mode, the oil pressure of the hydraulic chamber  240  formed in the outer tappet  100  is released and the latching pin  310  moves with being separated from the latching pin joining groove  340  by a restoring force of a return spring  330 , as shown in  FIG. 10 . The inner tappet  200  and the outer tappet  100  are separated from each other by the movement of the latching pin  310  and independently move. In this case, a latching pin supporting pin  320  supports the return spring  330  and is inserted into the inner tappet  200 . 
         [0011]    The valve is opened and closed by the inner tappet  200  that reciprocates by rotation of a low cam  14  joined to the cam shaft  10  and the outer tappet  100  merely moves up and down by a lost motion spring  500  (see  FIG. 4 ) depending on the rotation of the high cam  12  and has no influence on the opening and closing of the valve. 
         [0012]    However, if the cams  12  and  14  and surfaces of the tappets  100  and  200  of the variable valve lift apparatus do not coincide with each other, respectively, the variable tappets  100  and  200  rotate, and as a result, the engine is damaged. 
         [0013]    Further, since a working fluid can be supplied only when positions of a supply hole of the working fluid actuating the variable valve lift apparatus and a working fluid supplying hole of a bore of a cylinder head coincide with each other, an additional rotation preventing device for preventing rotation of the entire variable valve lift apparatus is required. 
         [0014]    The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
       BRIEF SUMMARY 
       [0015]    Various aspects of the present invention are directed to providing a variable valve lift apparatus with a stopper capable of limiting movement of a latching pin while allowing cams and tappet surfaces of the variable valve lift apparatus to coincide with each other by preventing the variable valve lift apparatus from being rotated. 
         [0016]    A variable valve lift apparatus including an inner tappet, an outer tappet surrounding and slidably contacting the inner tappet, and a latching pin slidably inserted into the inner tappet so as to implement a high lift and a low lift by selectively joining the inner tappet and the outer tappet, may include a stopper partially inserted into the outer tappet and spaced apart from the latching pin in a movement direction of the latching pin so as to limit movement of the latching pin, and forming a latching pin joining groove in the outer tappet to selectively receive the latching pin, wherein the stopper partially projects to the outside of the outer tappet and may be slidably engaged to a cylinder head groove formed to a cylinder head bore to prevent the variable valve lift apparatus from being rotated. 
         [0017]    The stopper may include an insertion portion having substantially the same diameter as the latching pin and being inserted into the outer tappet to limit the movement of the latching pin, and a projection portion projecting from the insertion portion to the outside of the outer tappet and having a shape to be slidably inserted into the cylinder head groove in order to prevent the variable valve lift apparatus from being rotated. 
         [0018]    The projection portion may have a semi-spherical shape which may be slidable while contacting the cylinder head groove. 
         [0019]    The projection portion may have a semi-cylindrical shape formed in a movement direction of the outer tappet and slides while contacting the cylinder head groove. 
         [0020]    A through-hole may be formed in the stopper and fluid-connected to the latching pin joining groove to smoothly discharge oil pressure supplied to actuate the latching pin. 
         [0021]    The insertion portion may have a cylindrical shape having the same radius as the latching pin. 
         [0022]    According to the exemplary embodiments of the present invention, it is possible to prevent an engine from being damaged by internally limiting a movement distance of a latching pin and externally preventing a variable valve lift apparatus from being rotated, make supply of a working fluid smooth, and save a manufacturing cost because an additional rotation preventing device does not need to be processed in a tappet skirt part. 
         [0023]    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 
         [0024]      FIG. 1  is a longitudinal cross-sectional view of a variable tappet according to an exemplary embodiment of the present invention. 
           [0025]      FIG. 2  is a plan view of a variable tappet according to an exemplary embodiment of the present invention. 
           [0026]      FIG. 3  is a perspective view of a state in which inner and outer tappets are partially cut according to an exemplary embodiment of the present invention. 
           [0027]      FIG. 4  show a use state diagram before and after a variable valve lift apparatus according to an exemplary embodiment of the present invention is joined to a cylinder head and an enlarged diagram of a principal part. 
           [0028]      FIG. 5  is a perspective view of a variable tappet according to various exemplary embodiments of the present invention. 
           [0029]      FIG. 6A to 6D  are a perspective view, a plan view, a side view, and a front view of a stopper according to various exemplary embodiments of the present invention. 
           [0030]      FIG. 7  is a perspective view of a variable tappet according to various exemplary embodiments of the present invention. 
           [0031]      FIGS. 8A to 8D  are a perspective view, a plan view, a side view, and a front view of a variable tappet according to various exemplary embodiments of the present invention. 
           [0032]      FIG. 9  is a cross-sectional view of a variable tappet in a high lift mode of a known variable valve lift apparatus. 
           [0033]      FIG. 10  is a cross-sectional view of a variable tappet in a low lift mode of a known variable valve lift apparatus. 
       
    
    
       [0034]    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. 
         [0035]    In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. 
       DETAILED DESCRIPTION 
       [0036]    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. 
         [0037]    The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. 
         [0038]      FIG. 1  is a longitudinal cross-sectional view of a variable tappet of a state in which a stopper is joined to the variable tappet according to an exemplary embodiment of the present invention and  FIG. 2  is a plan view of a variable tappet according to an exemplary embodiment of the present invention. 
         [0039]      FIG. 3  is a perspective view of a state in which inner and outer tappets are partially cut according to an exemplary embodiment of the present invention,  FIG. 4  is a use state diagram before and after a variable valve lift apparatus according to an exemplary embodiment of the present invention is joined to a cylinder head,  FIG. 5  is a perspective view of a variable tappet according to a first exemplary embodiment of the present invention, and  FIG. 6A to 6D  are a perspective view, a plan view, a side view, and a front view of a stopper according to a first exemplary embodiment of the present invention. 
         [0040]    First, referring to  FIGS. 1 to 6A  to  6 D, a stopper  400  that is provided to be spaced apart from a latching pin  310  at one upper side of an outer tappet  100  in a movement direction of the latching pin  310  is provided in the outer tappet  100 . In the above description, the latching pin  310  may be partially a hollow body and have a cylindrical shape. A latching pin supporting pin  320  limiting movement of the latching pin  310  while penetrating the latching pin  310  is joined to an inner tappet  200 . A return spring  330  that restores the latching pin  310  to an original state when oil pressure is released, while contacting the latching pin supporting pin  320 , is inserted into the latching pin  310 . 
         [0041]    Referring to  FIGS. 4 and 5 , the stopper  400  includes an insertion portion  410  having the same shape as the latching pin  310  to limit horizontal movement of the latching pin  310  and a projection portion  420  having a similar shape to a plan cross section of a groove  110  to slide while projecting to the outside of the outer tappet  100  and contacting an inner circumference of the groove  110  of a cylinder head. The insertion portion  410  may be a cylindrical shape having the same radius as the latching pin  310 . 
         [0042]    An exemplary embodiment of the present invention will hereinafter be described in more detail with reference to the accompanying drawings. 
         [0043]    In the variable valve lift apparatus, an auxiliary latching pin  370  pushes the latching pin  310  by oil pressure supplied at the time when the oil pressure is supplied through a hydraulic chamber  360  and the latching pin  310  in the inner tappet  200  moves to one inner side of the outer tappet  100 , such that the inner tappet  200  and the outer tappet  100  are joined to each other. In this case, a distance in which the latching pin  310  can move is limited to a movement limiting distance A. 
         [0044]    As such, the latching pin  310  selectively joins the outer tappet  100  and the inner tappet  200  while moving in a horizontal direction in order to control a valve lift, thereby implementing a high lift or a low lift. In this case, when the supplied oil pressure is excessively large, the latching pin  310  may move excessively. In order to prevent the excessive movement of the latching pin  310 , the latching pin  310  should move only within the movement limiting distance A in which the latching pin  310  can move. In the exemplary embodiment of the present invention, the stopper  400  serves to such a function. Further, the projection portion  420  that projects to the outside of the outer tappet  100  is engaged in the groove  110 , and as a result, the variable valve lift apparatus may move up and down without rotating. Therefore, since surfaces of the inner and outer tappets  100  and  200  coincide with a high cam  12  and a low cam  12  in a rotational direction, it is possible to prevent an engine from being damaged. 
         [0045]      FIG. 4  shows a use state diagram showing a state in which the stopper  400  according to the exemplary embodiment of the present invention is positioned in a cylinder head groove with being partially exposed to the outer tappet  100  and an enlarged diagram of a principal part. A left side of  FIG. 5  shows a state in which a tappet is inserted into a bore of a known cylinder head and a right side of  FIG. 5  shows a state in which the stopper  400  according to the exemplary embodiment of the present invention is inserted into the cylinder head groove  110 . Further, the enlarged diagram of the principal part shows a state in which the stopper  400  is engaged in the cylinder head groove  110 . 
         [0046]    The projection portion  420  of the stopper  400  should have a structure to slide on an inner circumference of the cylinder head groove in order to prevent the variable valve lift apparatus from being rotated. That is, when a plan cross section of the inner circumference of the cylinder head groove  110  has a semi-spherical shape, a plan cross section of the projection portion  420  should also have the semi-spherical shape. 
         [0047]    Therefore, in the first exemplary embodiment of the present invention, as shown in  FIG. 6B , the plan cross section of the projection portion  420  may have the semi-spherical shape. Further, since the projection portion  420  should slide on the inner circumference of the cylinder head groove  110 , the projection portion  420  may have a semi-cylindrical shape that is long in a vertical direction which is a movement direction, as shown in  FIGS. 5 and 6 . In addition, a through-hole  430  is formed at the center of the stopper  400  by passing through the insertion portion  410  and the projection portion  420 . The formation of the through-hole  430  is to easily discharge the oil pressure after actuating the latching pin  310  to the outside. 
         [0048]    A second exemplary embodiment is shown in  FIGS. 7 and 8A  to  8 D. According to the second exemplary embodiment, a projection portion  460  may have a semi-spherical shape. In this case, an insertion portion  450  has a cylindrical shape as shown in  FIG. 7 , and since the insertion portion  450  has a through-hole  470  formed at the center thereof as described in the first exemplary embodiment, the insertion portion  450  has a structure to easily discharge preused oil pressure. When the stopper  400  is manufactured as described in the second exemplary embodiment, the stopper  400  can be more easily manufactured than the stopper  400  in the first exemplary embodiment. 
         [0049]    As described above, it is possible to limit excessive horizontal movement of the latching pin  310  by the insertion portions  410  and  450  having the cylindrical shape, which are inserted into the outer tappet  100  and prevent the variable valve lift apparatus from being rotated by the projection portions  420  and  460  that project to the outside of the outer tappet  100 . It is possible to make supply of a working fluid smooth by allowing positions of a working fluid supplying hole and a supplying hole on a surface of a cylinder head bore  120  to coincide with each other as the variable valve lift apparatus is prevented from being rotated. Further, rotation surfaces of the high cam  12  and the low cam  14  of the variable valve lift apparatus coincide with the surfaces of the outer tappet  100  and the inner tappet  200 , respectively, thereby preventing the engine from being damaged. 
         [0050]    For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “inner” and “outer” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
         [0051]    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.