Abstract:
A variable valve lift apparatus may include a camshaft in which a cam is formed co-axially thereon; a variable shaft in which a groove is formed in an exterior circumference at a portion thereof, wherein the variable shaft is disposed in parallel with the camshaft; a variable guide, one end surface of which contacts the cam and the other end surface of which is inserted inside the groove of the variable shaft; a lever through which the variable shaft is rotatably inserted and on which the variable guide is slidably mounted; and a valve that is selectively lifted by the lever, wherein the variable guide selectively is inserted into the groove of the variable shaft to vary lift amount of the valve in accordance with rotation of the variable shaft.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Korean Patent Application Number 10-2007-0131659 filed Dec. 14, 2007, the entire contents of which application is incorporated herein for all purposes by this reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a variable valve lift apparatus, and more particularly to a variable valve lift apparatus for varying the lift amount of a valve. 
     2. Description of Related Art 
     A general cam that is mounted on an engine cannot vary the lift amount of a valve and cannot optimize fuel consumption and power. 
     Recently, experiments that change the lift amount, the opening timing, and the opening period of intake/exhaust valves have been carried at a good pace in order to improve output and efficiency of an engine. 
     Among them, there is a continuously variable valve lift apparatus (CVVL). 
     The continuously variable valve lift apparatus varies the lift amount of the intake/exhaust valves in accordance with driving conditions of the engine. 
     Accordingly, intake flux can be maximized in high speed/load conditions of driving in which high power is demanded, and simultaneously the intake flux can be minimized in low speed/load conditions of driving in which it is necessary to reduce exhaust gas and fuel consumption. 
     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 OF THE INVENTION 
     Various aspects of the present invention are directed to provide a variable valve lift apparatus having advantages of adequately varying the lift amount. 
     In an aspect of the present invention, a variable valve lift apparatus may include a camshaft in which a cam is formed co-axially thereon, a variable shaft in which a groove is formed in an exterior circumference at a portion thereof, wherein the variable shaft is disposed in parallel with the camshaft, a variable guide, one end surface of which contacts the cam and the other end surface of which is inserted inside the groove of the variable shaft, a lever through which the variable shaft is rotatably inserted and on which the variable guide is slidably mounted, and/or a valve that is selectively lifted by the lever, wherein the variable guide selectively is inserted into the groove of the variable shaft to vary lift amount of the valve in accordance with rotation of the variable shaft. 
     A spring may elastically support the lever and the camshaft. 
     The variable valve lift may further include a supporting member that is rotatably mounted on the camshaft, wherein the spring couples the supporting member and the lever. The camshaft may be inserted into the supporting member. 
     The variable valve lift apparatus may further include a swing arm of which one side is pivotally supported by a supporting portion and the other side is moved by the lever, wherein the valve is moved by the swing arm. 
     A lift control member may be formed at the groove and is configured to extend outwards from rotation center of the variable shaft in a rotating direction of the variable shaft. The lift control member may have a spiral structure configured to be continuously shorter or longer according to the rotation of the variable shaft so that the lift amount of the valve can be continuously varied. 
     In another aspect of the present invention, a variable valve lift apparatus may include a camshaft including a cam co-axially formed therein, a variable shaft disposed in parallel with the camshaft and including a first groove formed at an exterior circumference thereof and a lift control member formed in the first groove, a lever including an output cam and a second groove, wherein the variable shaft is rotatably inserted through the lever, a variable guide including a contact profile and a lift profile, wherein the contact profile contacts the cam and one end portion of the variable guide is slidably inserted into the second groove of the lever and mounted to the first groove of the variable shaft through the second groove, and/or a valve that is selectively lifted by the output cam of the lever and thus lift amount of the valve is varied in accordance with rotation of the variable shaft. 
     An elastic member may support the lever and the camshaft. The elastic member may be a spring. 
     The variable valve lift apparatus may further include a supporting member that is rotatably mounted on the camshaft, wherein the elastic member couples the supporting member and the lever. The camshaft may be rotatably inserted into the supporting member. 
     The variable valve lift apparatus may include a swing arm of which one side is pivotally supported by a supporting portion and the other side is moved by the lever, wherein the valve is moved by the swing arm. The swing arm may include a protruding portion slidably contacting the output cam of the lever. 
     The lift control member may be formed at the first groove and is configured to extend outwards from rotation center of the variable shaft in a rotating direction of the variable shaft. The lift control member may have a spiral structure configured to be continuously shorter or longer according to the rotation of the variable shaft so that the lift amount of the valve can be continuously varied. 
     The lift profile may have a semi-circular shape. 
     The contact profile may have a convex shape facing the cam wherein upper portion of the contact profile is narrower than lower portion thereof. 
     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 of the Invention, which together serve to explain certain principles of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial perspective view of an exemplary variable valve lift apparatus according to the present invention. 
         FIG. 2A  is a side view of an exemplary first condition according to the present invention. 
         FIG. 2B  is a side view of an exemplary second condition according to the present invention. 
         FIG. 3A  is a partial detailed view of  FIG. 2B . 
         FIG. 3B  is a partial detailed view of  FIG. 2A . 
         FIG. 4  is an exploded perspective view of an exemplary variable valve lift apparatus according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     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 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 partial perspective view of a variable valve lift apparatus according to various embodiments of the present invention. 
     Referring to  FIG. 1 , a variable valve lift apparatus includes a valve  100 , a swing arm  105 , a supporting portion  110 , a variable shaft  115 , a lever  120 , a variable guide  125 , a spring  130 , a supporting member  135 , and a camshaft  140 . 
     A cam  145  is formed on the camshaft  140 , and a protruding portion  200  is formed in an upper portion of the swing arm  105 . 
     The camshaft  140  is configured to penetrate the supporting member  135 , and the spring  130  is mounted between the supporting member  135  and the lever  120 . 
     One end portion of the spring  130  is connected to the supporting member  135  and the other end portion of the spring  130  is connected to the lever  120 . The spring  130  draws the lever  120  in a direction of the camshaft  140 . 
     The variable guide  125  is mounted to the lever  120  and the variable shaft  115  is rotatably coupled to the lever  120 . 
     Accordingly, the cam  145  and the variable guide  125  contact each other by the spring  130 . In particular, the variable guide  125  includes a contact profile  127  and thus the cam  145  slidably contact the lift profile  127  of the variable guide  125  by the spring  130 . 
     The camshaft  140  and the variable shaft  115  are configured to be parallel to each other. 
     The variable shaft  115  penetrates a portion of the lever  120  to form a hole ( 400   FIG. 4 ). Also, the variable guide  125  is inserted into a groove ( 405 ,  FIG. 4 ) that is formed in one side of the lever  120  that faces the cam  145 . 
     The position of the variable guide  125  varies in accordance with the rotation of the variable shaft  115  so that the lift amount of the valve  100  varies according to the rotation of the variable shaft  115  as explained in detail hereinafter. 
       FIG. 2A  is a side view of a low lift mode according to various embodiments of the present invention, and  FIG. 2B  is a side view of a high lift mode according to various embodiments of the present invention. 
     Referring to  FIG. 2A  and  FIG. 2B , one portion of the variable guide  125  may be inserted into the lever  120  in a direction of the rotation center of the variable shaft  115  in  FIG. 2A . The variable guide  125  includes a lift profile  128  at the lower portion thereof and the lift profile  128  of the variable guide  125  is rotatably supported by the variable shaft  115 . 
     Meanwhile, the variable guide  125  may move from the rotation center of the variable shaft  115  in a radial direction along the groove  405  in  FIG. 2B . 
     In this configuration, the relative distance between a contact point A of the cam  145  and the variable guide  125  and a contact point B of the swing arm  105  and the output cam  205  in  FIG. 2A  is smaller than that in  FIG. 2A . 
     The lift amount of the valve  100  is small in  FIG. 2A  so as to accomplish the low lift mode and the lift amount of the valve  100  is large in  FIG. 2B  so as to accomplish the high lift mode. 
     The movement characteristics of the swing arm  105  vary in various embodiments by the rotation of the variable shaft  115  that modify the positions of contact points A and B as explained above. 
     According to position of the contact point A of the variable guide  125  and the cam  145 , the lever  120  may rotate in the clockwise or anti-clockwise direction. 
     For instance, as the variable guide  125  moves upwards in a radial direction from the rotation center of the variable shaft  115  according to rotation of the variable shaft  115 , the cam  145  pushes the lever  120  in the clockwise direction so that the relative distance between the contact point A and the contact point B is increased so as to achieve the high lift mode. 
     In contrast, as the variable guide  125  moves downwards in a radial direction according to rotation of the variable shaft  115 , the spring  130  rotates the lever  120  towards the cam  145  in the anti-clockwise direction so that the relative distance between the contact point A and the contact point B is reduced so as to achieve the low lift mode. 
     The contact profile  127  of the variable guide  125  that contacts the cam  145  has a convex shape toward the cam  145 . 
     In  FIG. 2A , an output cam  205  is formed at a lower portion of the lever  120  and one surface of the output cam  205  pushes the protruding portion  200  of the swing arm  105 . In a like manner, the one surface of the output cam  205  pushes the protruding portion  200  of the swing arm  105  in  FIG. 2B . 
     While one side of the swing arm  105  is pivotally fixed by the supporting portion  110 , the other side pushes and moves the valve  100  according to the movement of the lever  120 . 
       FIG. 3A  is a partial detailed view of  FIG. 2B , and  FIG. 3B  is a partial detailed view of  FIG. 2A . 
     As shown in  FIG. 3A  and  FIG. 3B , a groove ( 410 ,  FIG. 4 ) is formed in the variable shaft  115 . The groove ( 410 ,  FIG. 4 ) is formed in a rotating direction of the variable shaft  115 , and the lift control member  300  formed in the groove ( 410 ,  FIG. 4 ) is configured to extend outwards from the rotation center of the variable shaft  115  in a rotating direction of the variable shaft  115 . Accordingly, the depth of the lift control member  300  of the groove ( 410 ,  FIG. 4 ) becomes continuously greater in a rotating direction. 
     Accordingly, the variable guide  125  contacting the lift control member  300  continuously moves in a radial direction from the rotation center of the variable shaft  115  according to rotation of the variable shaft  115 . 
       FIG. 4  is an exploded perspective view of a variable valve lift apparatus according to various embodiments of the present invention. 
     Referring to  FIG. 4 , a hole  400  is formed in both sides of the lever  120 , and the variable shaft  115  is slidably inserted through the hole  400 . 
     A groove  405  that communicates with the hole  400  is formed in a frontward direction of the lever  120 , and the variable guide  125  is inserted in the groove  405 . 
     A groove  410  is formed in one side of the exterior surface of the variable shaft  115  and the variable guide  125  is mounted in the groove  410 . 
     The surface of the variable guide  125  that contacts the lift control member ( 300 ,  FIG. 3B ) of the groove  410  includes the lift profile  128  having a curved line shape in the groove  410  in the variable guide  125 . 
     For convenience in explanation and accurate definition in the appended claims, the terms “high”, “low”, “frontward”, “exterior”, and “inner” 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.