Patent Publication Number: US-7905207-B2

Title: Variable valve lift apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Korean Patent Application No. 10-2008-0050296, filed on May 29, 2008, the entire contents of which are incorporated herein for all purposes by this reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an engine of a vehicle, and more particularly to a variable valve lift apparatus that continuously changes a lift amount of a valve. 
     2. Description of Related Art 
     An internal combustion engine generates power by burning fuel in a combustion chamber in an air media drawn into the chamber. Intake valves are operated by a camshaft in order to intake the air, and the air is drawn into the combustion chamber while the intake valves are open. 
     In addition, exhaust valves are operated by the camshaft, and a combustion gas is exhausted from the combustion chamber while the exhaust valves are open. 
     An optimal operation of the intake valves and the exhaust valves depends on a rotation speed of the engine. That is, an optimal lift or optimal opening/closing timing of the valves depends on the rotation speed of the engine. 
     For example, research has been undertaken for a variable valve lift (VVL) apparatus that enables different lifts depending on engine speed, and for a variable valve timing (VVT) apparatus that opens/closes the valves with different timing depending on the engine speed. 
     However, a rotating direction of a rocker arm and an amplification lever is different in the valve lift apparatus such that a profile characteristic of an output cam for operating a valve is poor. 
     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 minimizing friction and output loss and improving controllability and assemblability and to provide a variable valve lift apparatus having advantages of advancing the operating timing as the lift amount of the valve is reduced, and reducing fuel consumption. 
     In an aspect of the present invention, a variable valve lift apparatus, may include a camshaft including an input cam co-axially mounted thereon, a rocker arm shaft disposed in parallel with the camshaft with a predetermined distance therebetween, a shaft carrier, wherein the camshaft is rotatably coupled to first side of the shaft carrier and the rocker arm shaft is pivotally coupled to a second side thereof, a rocker arm that is pivotally coupled to the rocker arm shaft and includes a first roller disposed at one end portion of the rocker arm and contacting the input cam, a first link pivotally coupled to the other end portion of the rocker arm, an amplification lever pivotally coupled to one end portion of the first link, wherein one end portion of the amplification lever is coupled to the shaft carrier, a second link, one end portion of which is pivotally coupled to the other end of the amplification lever, an output cam, a first end portion of which is rotatably coupled to the camshaft and a second end portion of which is pivotally coupled to the other end portion of the second link, wherein a profile portion is formed at one side of an exterior circumference of the output cam, a variable driveshaft coupled to the rocker arm shaft and rotating the shaft carrier by a predetermined angle, and/or a valve that is moved by the profile portion of the output cam according to rotation of the output cam. 
     The profile portion may be formed at the output cam between the second end portion and a contact point that the output cam and a second roller of a swing arm contact each other. 
     The variable valve lift may further include an arm of which one side thereof is connected to the variable driveshaft and the other side thereof is connected to the rocker arm shaft. 
     The predetermined angle of the variable driveshaft may be regulated by a control member. 
     The camshaft and the rocker arm shaft may penetrate the shaft carrier to be mounted thereto. 
     The variable driveshaft may rotate the shaft carrier with respect to a rotation center of the cam shaft by the predetermined angle. The predetermined angle of the variable driveshaft may be regulated by a control member. An arm may be connected to the variable driveshaft and the other side thereof may be connected to the rocker arm shaft. 
     The cam shaft may penetrate substantially the middle portion of the output cam. 
     The variable valve lift apparatus may further include a swing arm that comes in contact with an outside surface of the profile portion of the output cam, wherein one side of the swing arm is pivotally supported by a hydraulic pressure valve gap adjustment member and the other side of the swing arm operates the valve. 
     The first end portion of the output cam may have a circular exterior circumference except the profile portion, which is substantially the same as the base circle of the input cam. 
     The first end portion of the output cam may have a circular exterior circumference except the profile portion, the circular exterior circumference having the same diameter as the input cam. 
     The variable valve lift apparatus may further include a return spring that is mounted on the rocker arm shaft to bias the first roller of the rocker arm to the input cam. 
     The rocker arm, the first link, the amplification lever, the second link, and the profile portion may be sequentially disposed in a clockwise direction or in an anti-clockwise direction. 
     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 side view of a variable valve lift apparatus according to an exemplary embodiment of the present invention. 
         FIG. 2  is a front view of a variable valve lift apparatus according to an exemplary embodiment of the present invention. 
         FIG. 3  is a perspective view of a variable valve lift apparatus according to an exemplary embodiment of the present invention. 
         FIG. 4  is a partial detailed view of a variable valve lift apparatus according to an exemplary embodiment of the present invention. 
         FIG. 5  is a side view showing a high lift condition of a variable valve lift apparatus according to an exemplary embodiment of the present invention. 
         FIG. 6  is a side view showing a low lift condition of a variable valve lift apparatus according to an exemplary embodiment of the present invention. 
         FIG. 7  is a graph showing a lift amount of a variable valve according to an exemplary embodiment of 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. 
     A variable valve apparatus is explained in the following according to various exemplary embodiments of the present invention, while referring to the accompanying drawings. 
       FIG. 1  is a side view of a variable valve lift apparatus according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 1 , the variable valve lift apparatus includes an input cam  100 , a shaft carrier  102 , a camshaft  104 , a first roller  105 , a rocker arm  110 , a rocker arm shaft  115 , a return spring  120 , a first link  125 , an amplification lever  130 , a second link  135 , an output cam  140 , a swing arm  145 , a second roller  150 , a valve gap adjustment member  155 , a valve  160 , and a valve spring  165 . 
     First, the torque of the camshaft  104  is transferred to the valve  160  through the input cam  100 , the first roller  105 , the rocker arm  110 , the first link  125 , the amplification lever  130 , the second link  135 , the output cam  140 , the second roller  150 , and the swing arm  145 , and the valve  160  is lifted in a length direction as a predetermined lift. 
     The shaft carrier  102  is mounted on the camshaft  104  and the rocker arm shaft  115  is disposed in the shaft carrier  102 . The camshaft  104  and the rocker arm shaft  115  are disposed in parallel with each other, and the rocker arm  110  is rotatably mounted on the rocker arm shaft  115 . 
     The first roller  105  is disposed in one end portion of the rocker arm  110  and the first link  125  is connected to the other end portion of the rocker arm  110 . The rocker arm  110  is biased in a clockwise direction by the return spring  120  that is mounted on a middle portion of the rocker arm shaft  115 . Accordingly, the first roller  105  contacts the input cam  100  by elastic restoring force of the return spring  120 . 
     One end of the amplification lever  130  is pivotally coupled to the shaft carrier  102  and the other end of the amplification lever  130  is rotatably connected to one end of the second link  135 . The middle portion of the amplification lever  130  is connected to the one end portion of the first link  125  by a hinge, wherein the other end portion of the first link  125  is rotatably coupled to the other end portion of the rocker arm  110 . 
     One end portion of the second link  135  is pivotally connected to the amplification lever  130  and the other portion of the second link  135  is pivotally connected to one end portion of the output cam  140  by a hinge. The output cam  140  is mounted on the camshaft  104 , wherein the camshaft  104  penetrates substantially the middle portion of the output cam  140 . 
     Referring to  FIG. 2  and  FIG. 3 , the structure in which the lift characteristic of the valve  160  is varied by a variable valve lift apparatus is explained in the following. 
       FIG. 2  is a front view of a variable valve lift apparatus according to an exemplary embodiment of the present invention, and  FIG. 3  is a perspective view of a variable valve lift apparatus according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 2  and  FIG. 3 , the input cam  100  is disposed substantially in the middle portion of the camshaft  104  and the rocker arm  110  is disposed in the rocker arm shaft  115  corresponding to the input cam  100 . 
     The first link  125 , the amplification lever  130 , the second link  135 , the output cam  140 , the second roller  150 , the swing arm  145 , and the valve  160  are disposed at both sides of the rocker arm shaft  115 . Also, the shaft carriers  102  are respectively disposed at both sides of the rocker arm  110 . 
     As shown, the camshaft  104  and the rocker arm shaft  115  are disposed in parallel with each other, and the camshaft  104  and the rocker arm shaft  115  penetrate the shaft carrier  102  to be assembled. Also, the camshaft  104  that is mounted on the shaft carrier  102  rotates. The camshaft  104  and the rocker arm shaft  115  rotate independently. 
     As shown in  FIG. 2  and  FIG. 3 , in various embodiments of the present invention, a variable driveshaft  200  may be disposed at the same axis as that of the camshaft  104 . The variable driveshaft  200  is disposed in a length direction of the camshaft  104  and an arm  205  is formed at an end portion of the variable driveshaft  200 . The arm  205  is extended from an exterior circumference of the variable driveshaft  200  and is connected to the rocker arm shaft  115  at the other end portion thereof. 
     One end portion of the rocker arm shaft  115  is inserted into the other end portion of the arm  205  and the rocker arm shaft  115  that is engaged with the arm  205  can rotate with respect to a rotation axis of the variable driveshaft  200 . 
     When the variable driveshaft  200  rotates in a clockwise direction by a control portion and a driving portion, the rocker arm shaft  115  and the shaft carrier  102  rotate in a clockwise direction based on the camshaft  104 . 
     Further, referring to  FIG. 1 , when the shaft carrier  102  rotates in an anti-clockwise direction by the variable driveshaft  200 , the rocker arm  110  and the first roller  105  rotate in an anti-clockwise direction. In addition, the output cam  140  rotates in an anti-clockwise direction on the camshaft  104  as explained later in detail. 
     In a state in which the camshaft  104  rotates in an anti-clockwise direction, when the shaft carrier  102  rotates in an anti-clockwise direction, the timing at which the rocker arm  110  moves is retarded. Also, in a state in which the camshaft  104  rotates in a clockwise direction, when the shaft carrier  102  rotates in a clockwise direction, the timing at which the rocker arm  110  moves is advanced. 
     In a state in which the camshaft  104  rotates in a clockwise direction, when the shaft carrier  102  rotates in an anti-clockwise direction, the timing at which the rocker arm  110  moves is advanced. Also, in a state in which the camshaft  104  rotates in an anti-clockwise direction, when the shaft carrier  102  rotates in a clockwise direction, the timing at which the rocker arm  110  moves is retarded. 
     The camshaft  104  can rotate in a clockwise direction or in an anti-clockwise direction according to design specifications in various embodiments. Also, the valve gap adjustment member  155  actively supports one end of the swing arm  145  by hydraulic pressure to secure the movement of the valve  160 . 
     Referring to  FIG. 1 , the first roller  105 , the rocker arm  110 , the first link  125 , the amplification lever  130 , the second link  135 , and the output cam  140  are disposed in an anti-clockwise direction. 
       FIG. 4  is a partial detailed view of a variable valve lift apparatus according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 4 , the arrangement relationships of the second link  135 , the output cam  140 , and the second roller  150  are explained hereinafter. 
     One side of the output cam  140  is connected to the second link  135 , and the output cam  140  through which the camshaft  104  is inserted has a ring shape. Accordingly, the interior circumference of the output cam  140  slides with the exterior circumference of the camshaft  104 . 
     A connection portion (left side) that is connected to the second link  135  is formed at one side of the exterior circumference of the output cam  140 , and the other side of the exterior circumference of the output cam  140  contacts the second roller  150 . Also, the profile portion  400  protrudes at an exterior circumference of the output cam  140  between the connection portion and the second roller  150 . 
     The profile portion  400  substantially contacts the second roller  150  and moves the swing arm  145  and the valve  160 , and the thickness of the profile portion  400  gets wider from the second roller  150  to the connection portion. 
     The overall outline of the exterior circumference of the output cam  140  except the profile portion  400  and the connection portion has a circular shape corresponding to the base circle  405  of the input cam  100 . 
     One side of the exterior circumference of the output cam  140  has a path that is the same as that of the base circle of the input cam, so it is possible for the second roller  150  to be directly operated by the input cam. 
     That is, in  FIG. 2 , in a state in which a position of the camshaft  104  is not changed, the swing arm  145  and the valve  160  are positioned corresponding the input cam  100 , and then the second roller  150  and the swing arm  145  are directly operated by the input cam  100 . 
       FIG. 5  is a side view showing a high lift condition of a variable valve lift apparatus according to an exemplary embodiment of the present invention. 
     The valve  160  is not lifted by the output cam  140  in (a) of  FIG. 5 , and the valve  10  is lifted by the output cam  140  in (b) of  FIG. 5 . 
     As shown, a horizontal line  500  that passes through the center of the camshaft  104  has a cross angle θ with a slanted line  505  that passes from the center of the camshaft  104  to the center of the rocker arm shaft  115  (0°&lt;θ&lt;90°). 
     When the cross angle that the horizontal line  500  and the slanted line  505  form is θ in various embodiments, the valve  160  is lifted high. 
       FIG. 6  is a side view showing a low lift condition of a variable valve lift apparatus according to an exemplary embodiment of the present invention. 
     The valve  160  is not lifted in (a) of  FIG. 6 , and the valve  160  is lifted by the output cam  140  in (b) of  FIG. 6 . 
     As shown, the cross angle of a horizontal line  500  that passes through the camshaft  104  and a slanted line  505  that passes from the center of the camshaft  104  to the center of the rocker arm shaft  115  is θ′(0&lt;θ′&lt;θ&lt;90). 
     When the cross angle of the horizontal line  500  and the slanted line  505  is θ′, the valve  160  is lifted low in the illustrated exemplary embodiment. 
       FIG. 7  is a graph showing a lift amount of a variable valve  160  according to an exemplary embodiment of the present invention. 
     As shown, the horizontal axis shows a rotation angle of a crankshaft, and the vertical axis shows a lift amount of the valve. 
     As shown in  FIG. 7 , a variable valve lift as well as variable valve timing can be achieved in the variable valve lift apparatus according to various embodiments of the present invention. 
     In addition, referring to  FIGS. 5 and 6 , the opening timing of the valve  160  is advanced as the lift amount of the valve is reduced and the camshaft  104  rotates in a clockwise direction in the illustrated exemplary embodiment, and the opening timing of the valve  160  is retarded as the lift amount of the valve is increased and the camshaft  104  rotates in an anti-clockwise direction. 
     Further, according to the design specifications of the above constituent elements, the opening timing of the valve  160  is retarded as the lift amount of the valve is reduced and the camshaft  104  rotates in an anti-clockwise direction and the opening timing of the valve  160  is advanced as the lift amount of the valve is increased and the camshaft  104  rotates in a clockwise direction. 
     At the same time, according to various embodiments of the present invention, the mounting height of the variable valve lift apparatus is the same as that of the center of the camshaft such that assemblability and compatibility thereof can be improved. 
     For convenience in explanation and accurate definition in the appended claims, the terms “interior” and “exterior” 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.