Abstract:
A hydraulic pressure variable valve lift apparatus may include a housing that a piston chamber that one side thereof is opened is formed, a valve operating piston that is slidably disposed in the piston chamber and one end thereof is connected to a valve for opening/closing a port, and an EHV hydraulic pump that is configured to supply the piston chamber with oil, wherein a first oil passage is formed between the EHV hydraulic pump and the piston chamber on as to supply a side surface of the piston chamber with oil, and an orifice hole is formed from a piston side surface of the valve operating piston to a piston upper end surface. Accordingly, the valve lift amount can be varied according to the operating condition of the engine, a hydraulic pressure variable valve lift apparatus reduces an impact at a moment when the valve is closed by having a valve lift formed a ramp profile and does not require accurate process of multi orifice and thereby decreases a production cost.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2010-0112299 filed Nov. 11, 2010, 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 apparatus. More particularly, the present invention relates to a hydraulic pressure variable valve lift apparatus that varies lift mount of a valve for opening/closing a port of an internal combustion engine. 
         [0004]    2. Description of Related Art 
         [0005]    An internal combustion engine takes fuel/air into a combustion chamber and combusts them to generate power. An intake valve is opened by a cam shaft to suck in the air and the air is supplied into the combustion chamber while the intake valve is opened. 
         [0006]    Also, an exhaust valve is lifted by a camshaft and the combustion gas is exhausted from the combustion chamber while the exhaust valve is opened. 
         [0007]    An optimal operation of the intake valves and the exhaust valves depends on a rotation speed of the engine. That is, an optimum lift or optimum opening/closing timing of the valves depends on the rotation speed of the engine. Researches has been undertaken on a variable valve lift (VVL) apparatus that enables different valve lifts depending on the engine speed so as to achieve such an optimal valve operation depending on the rotation speed of the engine. 
         [0008]    Meanwhile, since a CVVL that is broadly used includes a link, an eccentric cam, a control shaft, and so on and the number of components is large, the inertial weight and the accumulated tolerance become larger and there is a drawback in developing moving characteristics of the CVVL system. 
         [0009]    Also, since the valve of the cylinder is simultaneously controlled by the same camshaft, the free valve movement is restricted. 
         [0010]    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 
       [0011]    Various aspects of the present invention provide for a hydraulic pressure variable valve lift apparatus having advantages of that is able to adjust a valve lift amount according to the operating condition of an engine and reducing an impact at the moment when the valve is closed such that a valve lift forms a lamp profile 
         [0012]    A hydraulic pressure variable valve lift apparatus, according to various aspects of the present invention may include a housing that a piston chamber that one side thereof is opened is formed, a valve operating piston that is slidably disposed in the piston chamber and one end thereof is connected to a valve for opening/closing a port, and an EHV hydraulic pump that is configured to supply the piston chamber with oil, wherein a first oil passage is formed between the EHV hydraulic pump and the piston chamber so as to supply a side surface of the piston chamber with oil, and an orifice hole is formed from a piston side surface of the valve operating piston to a piston upper end surface. 
         [0013]    One side of the first oil passage may be connected to a hydraulic pressure line and a first check valve is disposed at the main oil passage so as to prevent the oil from being flown backward. 
         [0014]    A second oil passage that is diverged from the first oil passage and may be connected to the piston chamber is formed and a second check valve is disposed at the second oil passage so as to prevent the oil from being flown backward. The second oil passage may be connected to a chamber upper end surface of the piston chamber. 
         [0015]    The second oil passage may be connected to the other side of the piston chamber corresponding to the first oil passage. 
         [0016]    The first oil passage may be connected to a side surface of the piston chamber with at least L 1  from a chamber upper end surface of the piston chamber, the second oil passage is connected to a side surface of the piston chamber with at least L 2  from a chamber upper end surface of the piston chamber, and the length of the L 1  is longer than that of the L 2 . 
         [0017]    The second check valve may include a check ball for preventing back flowing and a check valve orifice is formed in the check ball such that small amount of oil flows backward or forward. 
         [0018]    An orifice check valve may be disposed at the orifice hole such that the oil flux that is supplied to the piston chamber through the orifice hole is limited and the supplied oil is prevented from being flown backward. 
         [0019]    The orifice check valve may include a check ball for preventing back flowing and a check valve orifice is formed in the check ball such that small amount of oil flows backwards or forward. 
         [0020]    The first oil passage may be connected to a hydraulic pressure release line, includes an oil control valve is disposed at the hydraulic pressure release line so as to open/close the hydraulic pressure release line, and an accumulator that is disposed at a downstream side of the oil control valve in the hydraulic pressure release line and temporally stores the hydraulic pressure that is released. 
         [0021]    The accumulator may include an accumulator piston that is slidably disposed in the accumulator chamber that is formed in one side of the hydraulic pressure release line and an accumulator spring that elastically supports the accumulator piston. 
         [0022]    As stated above, a hydraulic pressure variable valve lift apparatus according to various aspects of the present invention have the valve lift amount be varied according to the operating condition of the engine. 
         [0023]    A hydraulic pressure variable valve lift apparatus according to various aspects of the present invention reduces an impact at a moment when the valve is closed by having a valve lift formed a ramp profile. 
         [0024]    A hydraulic pressure variable valve lift apparatus according to various aspects of the present invention does not require accurate process of multi orifice and thereby decreases a production cost. 
         [0025]    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 
         [0026]      FIG. 1  is a cross-sectional view of an exemplary hydraulic pressure variable valve lift apparatus according to the present invention. 
           [0027]      FIG. 2A  to  FIG. 2E  are showing operating conditions of an exemplary hydraulic pressure variable valve lift apparatus according to the present invention. 
           [0028]      FIG. 3  is a partial cross-sectional view of an exemplary hydraulic pressure variable valve lift apparatus according to the present invention. 
           [0029]      FIG. 4  is a partial cross-sectional view of another exemplary hydraulic pressure variable valve lift apparatus according to the present invention. 
           [0030]      FIG. 5  is a partial cross-sectional view of another exemplary hydraulic pressure variable valve lift apparatus according to the present invention. 
       
    
    
     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]    Referring to  FIG. 1 , a hydraulic pressure variable valve lift apparatus includes housing. 
         [0033]    A piston chamber  135 , which is opened in a lower side, is formed, in the housing  120 , a valve operating piston  130  is disposed in the piston chamber  135 , a hydraulic pressure gap adjuster  110  (e.g., HLA: hydraulic lash adjuster) is disposed at a lower side of the valve operating piston  130 , and the hydraulic pressure gap adjuster  110  is connected to a valve  100 . 
         [0034]    The valve  100  moves up and down together with the hydraulic pressure gap adjuster  110  and the valve operating piston  130 . 
         [0035]    An EHV hydraulic pump  155  is prepared on the housing  120  and the EHV hydraulic pump  155  includes an EHV piston  155 A and a camshaft  155   b.    
         [0036]    The EHV is an abbreviation of Electro Hydraulic Valve. 
         [0037]    A pump chamber  158  is formed in the housing, which is spaced apart from the piston chamber  135  to be opened to a side of the housing, the EHV piston  155 A is inserted into the pump chamber  158 , and the camshaft  155   b  is disposed corresponding to an outside end portion of the EHV piston  155 A. 
         [0038]    Further, a return spring  157  returns the EHV piston  155 A that is inserted into the pump chamber  158  in a central direction of the camshaft  155   b.    
         [0039]    Accordingly, as the camshaft  155   b  rotates, the cam have the EVH piston  155 A be inserted into the pump chamber  158  and oil pressure of the pump chamber is increased. 
         [0040]    The first oil passage  160  connects the pump chamber  158  with the piston chamber  135 . Particularly, the first oil passage  160  is connected to a side surface corresponding to a piston side surface  196  of the valve operating piston  130 . 
         [0041]    An orifice hole  125  which connects the piston side surface  196  with the piston upper end surface  194  is formed in an incline in the valve operating piston  130 . In this condition, oil is charged between a piston upper end surface  194  of the valve operating piston  130  and a chamber upper end surface  192  the piston chamber  135  through the orifice hole  125 . 
         [0042]    As shown in drawings, in a case that the valve operating piston  130  is positioned in an upper portion of the piston chamber  135 , the orifice hole  125  is connected to the first oil passage  160 . 
         [0043]    A main oil passage  140  is formed in the housing  120  and the main oil passage  140  joins a middle portion of the first oil passage  160 . 
         [0044]    A first check valve  150  is disposed in the middle of the main oil passage  140  and the first check valve  150  prevents the oil of the first oil passage from being flown backward through the main oil passage  140 . 
         [0045]    The main oil passage  140  is connected to other oil line and supplements the first oil passage  160  with oil through the first check valve  150 . 
         [0046]    Further, a HLA oil passage  145  is diverged from the main oil line  140  downstream side of the first check valve  150  and supplies the hydraulic pressure gap adjuster  110  with oil. 
         [0047]    A hydraulic pressure release line  199  is connected to the first oil passage  160  and an oil control valve  170  and an accumulator  180  are sequentially disposed on the hydraulic pressure release line  199 . 
         [0048]    If the oil control valve  170  is opened, hydraulic pressure is released to the accumulator  180  through the oil control valve  170  of the hydraulic pressure release line  199 . 
         [0049]    The accumulator  180  includes an accumulator piston  184  that is disposed in an accumulator chamber  182  and an accumulator spring  186  that elastically supports the accumulator piston  184 . 
         [0050]    If the oil control valve  170  is opened, the accumulator piston  184  moves left side that the accumulator chamber  182  is disposed by the hydraulic pressure and the accumulator spring  186  is compressed absorbing the hydraulic pressure. 
         [0051]    In various embodiments, the first check valve  150  has the oil flown in one direction and sustains the flux at less than a predetermined value. 
         [0052]    If the camshaft  155   b  rotates to push the EHV piston  155 A, oil of the pump chamber  158  is supplied to the first oil passage  160  and oil is supplied to the piston chamber  135  through the orifice hole  125 . 
         [0053]    Accordingly, the valve operating piston  130 , the hydraulic pressure gap adjuster  110 , and the valve  100  start to move downward. In this moment, because the oil amount that is supplied through the orifice hole  125  is small, the piston chamber  135  slowly moves in the early stage of the process. 
         [0054]    However if the valve operating piston  130  further moves downward, the first oil passage  160  is direct connected to the piston chamber  135  not through the orifice hole  125 . 
         [0055]    Accordingly, the oil amount that is supplied to the piston chamber is increased such that the valve operating piston  130  can quickly move. 
         [0056]    In other words, the valve  100  is slowly opened at an early stage of the lift period and the valve  100  is quickly opened at a middle stage of the lift. 
         [0057]    Further, in a closing period that the oil control valve  170  is opened such that the valve  100  moves upward, the valve  100  is slowly closed to reduce noise and vibration and mechanical friction and abrasion. 
         [0058]      FIG. 2A  shows a early stage of an opening period of the valve  100 , wherein oil is supplied to the first oil passage  160  and oil is supplied to the piston chamber  135  through the orifice hole  125 . 
         [0059]    Because a diameter of the orifice hole  125  is short, the oil amount that is supplied to the piston chamber  135  is small. Accordingly, the valve  100  is slowly opened forming a ramp. 
         [0060]      FIG. 2B  shows a middle stage of the opening period of the valve  100 , wherein oil is supplied to the first oil passage  160  and the oil of the first oil passage  160  is direct supplied to the piston chamber  135 , compared to the early stage that the oil is supplied through the orifice hole  125 . 
         [0061]    In this case, the valve operating piston  130  closes a part of the first oil passage  160 . 
         [0062]    Referring to  FIG. 2B , the first oil passage is connected to a side surface of the piston chamber  135 , wherein the first oil passage  160  is connected to a point that has a L 1  distance from the chamber upper end surface  192 . 
         [0063]      FIG. 2C  shows a high lift stage of the valve  100 , wherein the oil is supplied to the first oil passage  160  and the oil of the first oil passage  160  is direct supplied to the piston chamber  135 , compared with the early stage that the oil is supplied through the second check valve  185  and the orifice hole  125 . 
         [0064]    In this case, since the valve operating piston  130  does not close the first oil passage  160 , the amount that is supplied to the piston chamber  135  is increased. 
         [0065]      FIG. 2D  shows a closing stage of the valve  100 , as the oil control valve  170  is being opened, hydraulic pressure is released through the hydraulic pressure release line  199 . 
         [0066]    The oil starts to be released from the piston chamber  135  to the first oil passage  160 . 
         [0067]    In this case, since the valve operating piston  130  does not close the first oil passage  160 , the return amount that is returned from the piston chamber  135  to the first oil passage  160  is increased. 
         [0068]      FIG. 2E  shows a closing lamp stage of the valve, the hydraulic pressure of the oil is released through the orifice hole. 
         [0069]    In this case, since the valve operating piston  130  closes the first oil passage  160  and the oil is only returned through the orifice hole  125 , the amount that is returned from the piston chamber  135  through the first oil passage  160  is decreased. Accordingly, the valve  100  forms a lamp to be slowly closed. 
         [0070]    Referring to  FIG. 3 , the first oil passage  160  is connected to one side surface of the piston chamber  135  and the second oil passage  300  is diverged from the first oil passage  160  to be connected to the other side surface of the piston chamber  135 . 
         [0071]    The first oil passage  160  is connected to a point that has a L 1  distance from the chamber upper end surface  192  in the side surface of the piston chamber  135  and the second oil passage  300  is connected to a point that has a L 2  distance from the chamber upper end surface  192  in the other side surface of the piston chamber  135 . As shown, the length of L 1  is longer than that of L 2 . 
         [0072]    Accordingly, while the valve operating piston  130  is positioned at an upper side, small amount of oil is supplied to the piston chamber  135  through the orifice hole  125 , next middle amount of oil is supplied through the second oil passage  300 , and finally large amount of oil is supplied through the first oil passage  160  and the second oil passage  300 . 
         [0073]    Referring now to  FIG. 4 , which illustrates a partial cross-section of a hydraulic pressure variable valve lift apparatus similar to that described above, the differences of the illustrated apparatus are described and the overlapping descriptions are omitted. 
         [0074]    As shown in  FIG. 4 , the valve operating piston  130  is disposed to move up and down in the piston chamber  135  and the first oil passage  160  is connected to a side surface of the piston chamber  135 . 
         [0075]    An orifice hole  410  is formed from a side surface of the valve operating piston  130  to the piston upper end surface  194  and an orifice check valve  400  is disposed on the orifice hole  420 . 
         [0076]    The orifice check valve  400  restricts the flux of the oil that is supplied to the piston chamber  135  from the first oil passage through the orifice hole  420  and prevents the oil of the piston chamber  135  from being flown backward the first oil passage  160 . 
         [0077]    As shown in (a) of  FIG. 4 , a ball of the orifice check valve  400  is opened in a forward direction and oil is supplied to the piston chamber  135  through the first oil passage  160  and the orifice hole  420  such that the valve operating piston  130  moves downward. 
         [0078]    As shown in (b) of  FIG. 4 , a ball of the orifice check valve  400  is closed in a reverse direction and oil of the piston chamber  135  is exhausted to the first oil passage  160  through a ball orifice  410  that is formed in the ball of the orifice check valve  400  such that the valve operating piston  130  slowly moves upward. 
         [0079]    Referring now to  FIG. 5 , which illustrates a partial cross-section of a hydraulic pressure variable valve lift apparatus similar to that described above, the differences of the illustrated apparatus are described and the overlapping descriptions are omitted. 
         [0080]    As shown in  FIG. 5 , the valve operating piston  130  is disposed in the piston chamber  135  of the housing  120  to move up and down, the first oil passage  160  is connected to a side surface of the piston chamber  135 , and the second oil passage  500  is diverged from the first oil passage  160  to be connected to an upper end surface of the piston chamber  135 . 
         [0081]    The second check valve  510  is disposed on the second oil passage  500  to prevent the oil of the piston chamber  135  from being flown backward the first oil passage  160 . In this case, the check valve  510  does not completely cut off the reverse direction flow. 
         [0082]    As shown in detail (a) of  FIG. 5 , a ball of the second check valve  510  is opened in a forward direction and oil starts to be supplied to the piston chamber  135  through the second oil passage  500  such that the valve operating piston  130  starts to move downward. 
         [0083]    As shown in detail (b) of  FIG. 5 , a ball of the second check valve  510  is closed in a reverse direction and oil of the piston chamber  135  is exhausted to the first oil passage  160  through a ball orifice  520  that is formed in the ball of the second check valve  510  such that the valve operating piston  130  slowly moves upward. 
         [0084]    For convenience in explanation and accurate definition in the appended claims, the terms upper or lower, and etc. are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
         [0085]    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.