Abstract:
A variable valve lift apparatus may include a rocker arm coupled with a rocker arm shaft, a valve bridge disposed to be pressed by one end portion of the rocker arm, the valve bridge including a piston insertion hole and at least one pin insertion hole connecting to the piston insertion hole, a valve disposed to be pressed by the valve bridge, and a variable lift unit disposed in the valve bridge and variably controlling an amount that the rocker arm presses the valve bridge. The variable lift unit includes a variable piston of which the lower portion is inserted into the piston insertion hole, and a check pin disposed in the pin insertion hole to be selectively inserted into the pin groove formed on a side surface of the variable piston according to the hydraulic pressure supplied to the piston oil passage formed in the variable piston.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority of Korean Patent Application Number 10-2012-0147818 filed Dec. 17, 2012, the entire contents of which application is incorporated herein for all purposes by this reference. 
       BACKGROUND OF INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The present invention relates to a valve lift device. More particularly, the present invention relates to a variable valve lift apparatus that variably controls a lift amount of a valve opening/closing an intake port or an exhaust port of an internal combustion engine in multi steps. 
         [0004]    2. Description of Related Art 
         [0005]    An internal combustion engine generates power by burning fuel in a combustion chamber in an air media that is drawn into the chamber. Intake valves are operated by a camshaft in order to take in 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. 
         [0006]    An optimal operation of the intake valves and the exhaust valves depends on a rotation speed of the engine. That is, optimal opening/closing timing of the valves or an optimal lift depends on the rotation speed of the engine. 
         [0007]    In order to achieve such an optimal valve operation depending on the rotation speed of the engine, research has been undertaken on a variable valve lift (VVL) apparatus that enables different valve lifts depending on the engine speed. 
         [0008]    Meanwhile, a rocker arm is disposed on a rocker arm shaft, a cam that is disposed at one side of the rocker arm is used to lift a valve that is disposed at the other side of the rocker arm, a structure/method variably controlling the lift amount of the valve has been researched, and particularly a variable valve lift apparatus that has a simple structure and is easily assembled has been being researched. 
         [0009]    The information disclosed in this Background 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. 
       SUMMARY OF INVENTION 
       [0010]    The present disclosure has been made in an effort to provide a valve lift apparatus having advantages of reducing fuel consumption and noise/vibration by variably operating a valve in a high lift or a low lift through a simple structure. 
         [0011]    A variable valve lift apparatus according to various aspects of the present disclosure may include a rocker arm coupled with a rocker arm shaft, a valve bridge disposed to be pressed by one end portion of the rocker arm, wherein the valve bridge includes a piston insertion hole that is open upward and at least one pin insertion hole that connects to the piston insertion hole in a lengthwise direction of the valve bridge, a valve disposed to be pressed by the valve bridge, and a variable lift unit disposed in the valve bridge and variably controlling an amount that the rocker arm presses the valve bridge. The variable lift unit may include a variable piston of which the lower portion is inserted into the piston insertion hole, wherein a pin groove is formed on a side surface of the variable piston corresponding to the pin insertion hole, and a piston oil passage that is connected to the pin groove is formed in the variable piston to selectively receive a hydraulic pressure from the rocker arm, and a check pin disposed in the pin insertion hole to be selectively inserted into the pin groove of the variable piston according to the hydraulic pressure that is supplied to the piston oil passage. 
         [0012]    The variable valve lift apparatus may further include a pin elastic member that elastically supports the check pin such that a front end portion of the check pin is inserted into the pin groove and a return elastic member that elastically supports the variable pin upward. 
         [0013]    Hydraulic pressure may be selectively supplied to the piston oil passage through a shaft oil passage that is formed substantially along an interior central portion of the rocker arm shaft and a shaft variable oil passage that is formed in the rocker arm. 
         [0014]    The variable valve lift apparatus may further include a press bolt that is engaged with one end portion of the rocker arm and a lower end portion thereof faces an upper end portion of the variable piston and a bolt cap that is engaged with a lower end portion of the press bolt to press the upper end portion of the variable piston, wherein a bolt oil passage and a cap oil passage are formed in the press bolt and the cap, respectively, to connect the shaft variable oil passage with the piston oil passage. 
         [0015]    The pin insertion hole may have an inlet that is open to an outside of the valve bridge and a hole cap closes the inlet and supports the pin elastic member. 
         [0016]    A guide groove may be formed at a side surface of the variable piston, and a guide pin of which a front end portion may be inserted into the guide groove to guide a movement of the variable piston along the guide groove, wherein the guide pin may be fixed in the valve bridge. 
         [0017]    An exhaust hole may be formed such that a space that the return elastic member is disposed is connected to the outside. 
         [0018]    The at least one pin insertion hole may include two pin insertion holes, each disposed at one side of the piston insertion hole in a lengthwise direction of the valve bridge. 
         [0019]    The variable valve lift apparatus may further include a rocker arm elastic member that elastically supports the rocker arm such that one end portion of the rocker arm presses the valve bridge, wherein the rocker arm elastic member is a plate spring or a type of a plate spring, and one end thereof is fixed on the rocker arm shaft and the other end thereof elastically supports one end portion of the rocker arm shaft toward the valve bridge. 
         [0020]    The pin elastic member and the return elastic member may be coil springs or types of coil springs. 
         [0021]    As described above, a variable valve lift apparatus according to various aspects of the present disclosure forms a variable lift unit in a valve bridge to make overall structure simple, and hydraulic pressure is selectively supplied to a variable lift unit that is configured in a valve bridge through a rocker arm shaft and a rocker arm to be able to operate a valve in a high lift or a low lift mode. 
         [0022]    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 
         [0023]      FIG. 1  is a side view of an exemplary variable valve lift apparatus according to the present disclosure. 
           [0024]      FIG. 2  is a cross-sectional side view of an exemplary variable valve lift apparatus according to the present disclosure. 
           [0025]      FIG. 3A  is a perspective view of an exemplary variable valve lift apparatus according to the present disclosure. 
           [0026]      FIG. 3B  is a partial exploded perspective view of an exemplary variable valve lift apparatus according to the present disclosure. 
           [0027]      FIG. 4  is a partial cross-sectional view along A-A line of  FIG. 3A . 
           [0028]      FIG. 5  is a partial cross-sectional view along B-B line of  FIG. 3A . 
           [0029]      FIG. 6  is a partial cross-sectional view showing an operating procedure of an exemplary variable valve lift apparatus according to the present disclosure. 
           [0030]      FIG. 7  is a graph showing an effectiveness of an exemplary variable valve lift apparatus according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    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. 
         [0032]      FIG. 1  is a side view of an exemplary variable valve lift apparatus according to the present disclosure. Referring to  FIG. 1 , a variable valve lift apparatus includes a rocker arm shaft  100 , a rocker arm  120 , a roller  110 , a solenoid valve  180 , a rocker arm elastic member  130 , a press bolt  140 , a bolt cap  255 , a variable piston  200 , a valve bridge  150 , a valve spring  165 , and a first and second valves  160  and  170 . 
         [0033]    The rocker arm shaft  100  penetrates substantially across a central portion of the rocker arm  120 , and a press bolt  140  penetrates one end portion of the rocker arm  120  in a lower direction to be fixed thereon. 
         [0034]    The bolt cap  255  is fixed on a lower end portion of the press bolt  140 , and a lower end portion of the bolt cap  255  contacts an upper portion of the variable piston  200 . The variable piston  200  is inserted into an upper portion of the valve bridge  150 . 
         [0035]    Further, both sides of the lower portion of the valve bridge  150  are supported by the first and second valves  160  and  170 , and the valve spring  165  elastically supports the first and second valves  160  and  170  in an upper direction. 
         [0036]    One side of the rocker arm elastic member  130  is fixed on the rocker arm shaft  100  and the other side thereof elastically supports one end portion of the rocker arm  120  in a lower direction. 
         [0037]    The solenoid valve  180  selectively supplies a rocker arm main passage  102  or a shaft variable passage  104  that is formed in the rocker arm shaft  100  with hydraulic pressure, and the roller  110  contacts an output cam (non-illustrated) to rotate the rocker arm  120  on the rocker arm shaft  100 . 
         [0038]      FIG. 2  is a cross-sectional side view of an exemplary variable valve lift apparatus according to the present disclosure. Referring to  FIG. 2 , a rocker arm passage  246  that is connected to the shaft variable passage  104  is formed in the rocker arm  120 , and a bolt passage  250  that is connected to the rocker arm passage  246  is formed in the press bolt  140 . Further, a cap passage  257  that is connected to the bolt passage  250  is formed in the bolt cap  255 . 
         [0039]    A variable lift unit according to various embodiments of the present disclosure includes a variable piston  200 , a check pin  210 , a pin elastic member  220 , a hole cap  230 , and a return elastic member  240 . 
         [0040]      FIG. 3A  is a perspective view of an exemplary variable valve lift apparatus according to the present disclosure. Referring to  FIG. 3A , the variable piston  200  is inserted into a central portion of the upper portion of the valve bridge  150 , and an upper end portion of the variable piston  200  protrudes in an upper direction. 
         [0041]    A guide pin  320  is fixed on a side surface of the valve bridge  150 , and a hole cap  230  is fixed at an end portion of a length direction of the valve bridge  150 . 
         [0042]      FIG. 3B  is a partial exploded perspective view of an exemplary variable valve lift apparatus according to the present disclosure. Referring to  FIG. 3B , a guide groove  310  that the front end portion of the guide pin  320  is inserted therein is formed at one side surface of the variable piston  200 . A pin groove  330  is formed at the other side surface of the variable piston  200 . 
         [0043]      FIG. 4  is a partial cross-sectional view along A-A line of  FIG. 3A . Referring to  FIG. 4 , a piston insertion hole  410  that is opened toward an upper portion is formed on the valve bridge  150 , and the variable piston  200  is moved from an upper side to a lower side to be inserted into the piston insertion hole  410 . 
         [0044]    The pin insertion hole  420  that is connected to the piston insertion hole  410  is formed at both sides of the inside of the valve bridge  150  across the piston insertion hole  410 , and an inlet of the pin insertion hole  420  that is connected to an outside is closed by the hole cap  230 . 
         [0045]    A piston passage  300  is formed on the variable piston  200  from a central portion of an upper portion to a lower portion, and a pin groove  330  is formed at both sides of the variable piston  200  to correspond to the pin insertion hole  420 . 
         [0046]    A check pin  210  is inserted into the pin insertion hole  420 , and the pin elastic member  220  elastically supports the check pin  210  toward the pin groove  330 . Here, the hole cap  230  prevents that the pin elastic member  220  is separated from the valve bridge  150 . 
         [0047]    The piston passage  300  that is formed at a central portion of the variable piston  200  is connected to the pin groove  330 . And, a return elastic member  240  is disposed at a lower portion of the variable piston  200  in the piston insertion hole  410 , and the return elastic member  240  elastically supports the variable piston  200  in an upper direction. Further, an exhaust hole  400  that is connected to the piston insertion hole  410  is formed at a lower portion of the valve bridge  150 . 
         [0048]      FIG. 5  is a partial cross-sectional view along B-B line of  FIG. 3A . Referring to  FIG. 5 , the variable piston  200  is inserted into the piston insertion hole  410  of the valve bridge  150 , and the guide pin  320  is inserted into a side surface of the valve bridge  150 . The guide pin  320  is fixed on the valve bridge  150 , and the front end portion thereof is inserted into the guide groove  310  that is formed at a side surface of the variable piston  200 . 
         [0049]    The variable piston  200  is guided through a structure of the guide pin  320  and the guide groove  310 , and the guide pin  320  prevents that the variable piston  200  is separated from the valve bridge  150 . 
         [0050]      FIG. 6  is a partial cross-sectional view showing an operating procedure of an exemplary variable valve lift apparatus according to the present disclosure. In (a) of  FIG. 6 , a line hydraulic pressure is supplied through the shaft variable passage  104 , the rocker arm passage  246 , the bolt passage  250 , the cap passage  257 , and the piston passage  300  by the operation of the solenoid valve  180 , and the hydraulic pressure that is supplied to the piston passage  300  is transmitted to the pin groove  330 . 
         [0051]    The hydraulic pressure that is transmitted to the pin groove  330  pushes the check pin  210  that is inserted into the pin groove  330  toward the outside to separate the check pin  210  from the pin groove  330 . Accordingly, a state or stage like (b) of  FIG. 6  is achieved. 
         [0052]    In (b) of  FIG. 6 , if the rocker arm  120  pushes the variable piston  200 , the variable piston  200  is inserted into an inner side of the piston insertion hole  410  of the valve bridge  150 . And, while the variable piston  200  descends in a lower side, hydraulic pressure of the piston insertion hole  410  is exhausted to the outside through the exhaust hole  400 . 
         [0053]    If line hydraulic pressure is not supplied to the shaft variable passage  104  by the operation of the solenoid valve  180 , as shown in (d) of  FIG. 6 , the variable piston  200  is ascended by the return elastic member  240 . 
         [0054]    And, as shown in (e) of  FIG. 6 , the pin elastic member  220  pushes the check pin  210  such that the front end portion of the check pin  210  is inserted into the pin groove  330  of the variable piston  200 . Accordingly, although the rocker arm  120  pushes the variable piston  200 , the variable piston  200  is not inserted into the piston insertion hole  410 . 
         [0055]      FIG. 7  is a graph showing an effectiveness of an exemplary variable valve lift apparatus according to the present disclosure. Referring to  FIG. 7 , a horizontal axis denotes time, and a vertical axis denotes a lift amount of a valve. As shown in the drawings, if hydraulic pressure is supplied to the variable piston  200  by the operation of the solenoid valve  180 , the valve is operated in a lower lift mode, and if hydraulic pressure is not supplied to the variable piston  200  by the operation of the solenoid valve  180 , the valve is operated in a higher lift mode. 
         [0056]    In various embodiments of the present disclosure, a variable lift unit is configured in a valve bridge  150  such that the unit can be direct applied to a valve lift layout, hydraulic pressure is direct supplied through a rocker arm  120  such that the hydraulic control becomes quick and accurate, and a high lift and a low lift is realized by one cam. 
         [0057]    Further, a multi-step lift of a valve is realized by replacing a general valve bridge with new valve bridge, and therefore a development cost is reduced, standardization of components becomes easy, fuel consumption is reduced in a low load and a low RPM condition, and control responsiveness of engine can be improved. 
         [0058]    For convenience in explanation and accurate definition in the appended claims, the terms “upper” or “lower”, “front or rear”, “inside” or “outside”, and etc. are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
         [0059]    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.