Abstract:
A variable valve lift apparatus includes a high cam and a low cam fixed side by side to a camshaft, an outer body pressed by the rotation of the high cam, and has a crossbar formed at the bottom of the front end, an inner body, of which the front end protrudes further than the outer body, the lower front end is provided with a valve member, the upper rear end is hinged to a lost motion hinge shaft coaxially with the rear end of the outer body, and the lower rear end is pivotally connected to a hinge member, and a latching portion inserted into the inner body and selectively connected to the crossbar of the outer body to move the inner body dependent on movement of the front end of the outer body, wherein the lost motion hinge shaft is disposed in the same direction as a hinge point between the inner body and the hinge member with respect to the camshaft. Dynamic characteristics can be obtained by reducing the moment of inertia of the variable valve lift apparatus, and the dynamic characteristics can be further improved by inserting the latching portion into the inner body so as to be closer to the camshaft.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2010-0103359 filed Oct. 22, 2010, the entire contents of which application is incorporated herein for all purposes by this reference. 
     BACKGROUND OF INVENTION 
     1. Field of Invention 
     The present invention relates to a variable valve lift apparatus, and more particularly, to a variable valve lift apparatus in which a latching portion connecting an inner body and an outer body is disposed adjacent to a cam, and a lost motion hinge shaft and a hinge point of the variable valve lift apparatus are disposed in the same direction relative to a camshaft. 
     2. Description of Related Art 
     In general, an internal combustion engine generates power by taking in fuel and air and burning it in a combustion 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 exhaust gas is expelled from the combustion chamber while the exhaust valves are open. 
     An optimal operation of the intake and exhaust valves depends on the 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. In order to achieve such an optimal valve operation depending on the rotation speed of the engine, research has been undertaken for a variable valve lift (VVL) apparatus that includes a plurality of cams for driving the valves, or varies the lift of the valves depending on the number of rotations of the engine. 
     In a conventional variable valve lift apparatus, as shown in  FIG. 10 , a lost motion hinge shaft  40  connecting an outer body  10  and one side of an inner body  20  and a hinge shaft  60  of the variable valve lift apparatus are formed at the left and right of a camshaft. 
       FIG. 11   a  is a longitudinal cross-sectional view of the conventional variable valve lift apparatus in a latching operation, and  FIG. 11   b  is a longitudinal cross-sectional view of the conventional variable lift apparatus in an unlatching operation. Conventionally, as shown in  FIGS. 11   a  and  11   b , the outer body  10  and the other side of the inner body  20  are connected by a latching mechanism  30  inserted into the outer body  10 . Moreover, in an unlatching operation, the inner body  20  creates lost motion by a lost motion spring  50 . 
     As the latching mechanism  30  is inserted into the outer body  10  as described above, the latching mechanism  30  becomes distant from the camshaft to thereby deteriorate the dynamic characteristics of the variable valve lift apparatus due to the moment of inertia. Also, a valve member is positioned under the lost motion spring  50 , and such an apparatus has to press the valve member, thereby making the actual manufacture of the apparatus difficult. 
     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 
     Various aspects of the present invention provide for a variable valve lift apparatus having the advantage of obtaining dynamic characteristics by reducing the moment of inertia of the variable valve lift apparatus, in which a latching portion is inserted into an inner body and positioned midway between a valve member and a hinge member, and a lost motion hinge point and the hinge member are positioned in the same direction relative to a camshaft. 
     Various aspects of the present invention provide for a variable valve lift apparatus including a high cam and a low cam fixed side by side so as to be eccentric to a camshaft, an outer body which is pressed by the rotation of the high cam, and has a crossbar formed at the bottom of the front end, an inner body, of which the front end protrudes further than the outer body, the lower front end is provided with a valve member, the upper rear end is hinged to a lost motion hinge shaft coaxially with the rear end of the outer body, and the lower rear end is pivotally connected to a hinge member, and a latching portion which is inserted into the inner body and selectively connected to the crossbar of the outer body to make the movement of the inner body to be dependent on the movement of the front end of the outer body, wherein the lost motion hinge shaft is disposed in the same direction as a hinge point between the inner body and the hinge member with respect to the camshaft. 
     Moreover, the latching portion according to various aspects of the present invention may include a hollow cylindrical latching pin, and a return spring which is inserted into the latching pin and selectively moves the latching pin by being selectively compressed or released by supply of oil. 
     Furthermore, the latching portion according to various aspects of the present invention may further include a return spring support pin which is positioned at the end of the return spring, and inserted and fixed into the inner body to restrict the movement of the latching pin. 
     In addition, the latching portion according to the various aspects of the present invention is positioned midway between the hinge member connected to the lower rear end of the inner body and the valve member. 
     Various aspects of the present invention provide for a variable valve lift apparatus including a high cam and a low cam fixed side by side to a camshaft, an outer body which is pressed by the rotation of the low cam, and of which the front end is provided with a valve member, the upper rear end is hinged to a lost motion hinge shaft, and the lower rear end is pivotally connected to a hinge member, an inner body which is inserted into the outer body, and of which the rear end is hinged to the lost motion hinge shaft coaxially with the outer body, and a latching portion which is inserted into the inner body and selectively moved into the outer body to selectively connect the outer body and the inner body, wherein the lost motion hinge shaft is disposed in the same direction as a hinge point between the outer body and the hinge member with respect to the camshaft. 
     Moreover, the latching portion according to various aspects of the present invention may include a hollow cylindrical latching pin formed perpendicular to the lost motion hinge shaft, and a return spring which is inserted into the latching pin and selectively moves the latching pin by being selectively compressed or released by supply of oil. 
     Furthermore, the latching portion according to various aspects of the present invention may further include a return spring support pin which is positioned at the end of the return spring, and inserted and fixed into the inner body to restrict the movement of the latching pin. 
     In addition, the latching portion according to various aspects of the present invention is positioned midway between the hinge member connected to the lower rear end of the inner body and the valve member. 
     According to the above-described variable valve lift apparatus, dynamic characteristics can be obtained by reducing the moment of inertia of the variable valve lift apparatus, and the dynamic characteristics can be further improved by inserting the latching portion into the inner body so as to be closer to the camshaft. 
     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 
         FIG. 1  is a perspective view of an exemplary variable valve lift apparatus according to the present invention. 
         FIG. 2  is a longitudinal cross-sectional view of  FIG. 1 . 
         FIG. 3  is an enlarged view of exemplary parts of the variable valve lift apparatus of  FIG. 1 . 
         FIG. 4  is a longitudinal cross-sectional view of  FIG. 3 . 
         FIG. 5  is a perspective view of an exemplary latching portion according to the present invention. 
         FIG. 6   a  is a cross-sectional view of the latching portion of  FIG. 5  and an outer body in an unlatching operation according to the present invention. 
         FIG. 6   b  is a cross-sectional view of the latching portion of  FIG. 5  and the outer body in a latching operation according to the present invention. 
         FIG. 7  is a side cross-sectional view of another exemplary variable valve lift apparatus according to the present invention. 
         FIG. 8  is a top plan view of the variable valve lift apparatus of  FIG. 7 . 
         FIG. 9  is a cross-sectional view of the cam and camshaft of  FIG. 7 . 
         FIG. 10  is a perspective view of a conventional variable valve lift apparatus. 
         FIG. 11   a  is a longitudinal cross-sectional view of the conventional variable valve lift apparatus in the latching operation. 
         FIG. 11   b  is a longitudinal cross-sectional view of the conventional variable valve lift apparatus in the unlatching operation. 
     
    
    
     DETAILED DESCRIPTION 
     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. 
     In the variable valve lift apparatus of the present invention, rotating high and low cams having different cam profiles and arranged side by side on an outer side of a cylinder are respectively in rolling contact with the outer body or the inner body, and the outer body and the inner body are connected coaxially with the lost motion hinge shaft. 
     With reference to  FIGS. 1 to 4 , in the variable valve lift apparatus according to various embodiments of the present invention, an outer body  100  is pressed by a high cam  170 , and an inner body  200  is pressed by a low cam  160 . The outer body  100  and the inner body  200  are rotatable coaxially with the lost motion hinge shaft  110 . Since a valve member  400  is disposed at the front end of the inner body  200 , the valve member  400  is pressed by rotation of the inner body  200 . The lower rear end of the inner body  200  is hinged to a hinge member  150 . A valve stem end  420  is formed at the upper end of the valve member  400 , and a valve spring seat  410  is formed at an intermediate portion thereof. As the valve spring  430  is positioned between the valve stem end  420  and the valve spring seat  410 , the valve member  400  ascends and descends by the valve spring  430 . Moreover, the outer body  100  has a U-shaped crossbar  180  which is formed below the inner body  200  to support the inner body  200 . In a latching operation, as a latching portion  300  inserted into the inner body  200  protrudes outwardly, the outer body  100  is fit between the inner body  200  and the latching portion  300 , thus causing the movement of the inner body  200  to be dependent on the movement of the outer body  100 . Therefore, the inner body  200  can ascend and descend as the outer body  100  ascends and descends. 
     The latching portion  300  is inserted into the inner body  200 . Upon selective supply of oil, the latching portion  300  moves and latches the outer body  100  and the inner body  200 . In the latching operation, the front lower end of the outer body  100  presses the latching portion  300  and thereby simultaneously presses the inner body  200  into which the latching portion  300  is inserted. This is illustrated in  FIG. 4 . 
     The latching portion  300  is positioned midway between the valve member  400  and the hinge member  150 , and in various embodiments, directly below a camshaft. To this end, the latching portion  300  has to be inserted into the inner body  200 . This is to reduce the moment of inertia by shortening the distance from the lost motion hinge shaft  110  to the camshaft. 
     On the other hand, in an unlatching operation, the latching is released as the latching portion  300  returns to the original state. The outer body  100  create lost motion in the unlatching operation, which is performed by a lost motion spring  120  connected to the lost motion hinge shaft  110 . 
     The latching portion  300  includes a hollow cylindrical latching pin  330 , a return spring  320  inserted into the latching pin  300  and selectively compressed or released by supply of oil, a return spring support pin  310  restricting the movement of the latching pin  330  along with the return spring  310 , and a stopper  370  stopping the supply of oil and making contact with the return spring  320 . 
       FIG. 5  is a perspective view of the latching portion  300 . While the return spring support pin  310  is inserted and fixed into the inner body  200 , the latching pin  330  moves left and right relative to the return spring support pin  310 . 
     Turning now to  FIGS. 7 to 9 ,  FIG. 7  is a cross-sectional view of a variable valve lift apparatus according to various embodiments of the present invention, in which, unlike some embodiments described above, the front end of the outer body  500  is in contact with the valve member  400 , and the rear end of the outer body  500  is hinged to the hinge member  150 . Moreover, unlike some embodiments described above, the low cam  520  is in contact with the inner body  600 , and the high cam  510  is in contact with the outer body  500 .  FIG. 9  shows a connection relationship among the camshaft  524 , low cam  520 , and high cam  510  of the variable valve lift apparatus according to various embodiments of the present invention. 
     Except as mentioned above, the various embodiments are similar to those described above. For example, in the apparatus shown in  FIG. 7 , too, the latching portion  300  is inserted into the inner body  600 , and the latching portion  300  includes a latching pin  330 , a return spring  320 , a return spring support pin  310 , and a stopper  370 . 
     As in the above-described embodiments, the latching portion  300  is positioned midway between the valve member  400  and the hinge member  150 , and in various embodiments, positioned directly below the camshaft. To this end, the latching portion  300  has to be inserted into the inner body  600 . This is to reduce the moment of inertia by shortening the distance from the lost motion hinge shaft  550  to the camshaft. 
     Now, an operating process of the latching portion  300 , a part common to illustrated exemplary embodiments of the present invention, will be described in more detail. 
       FIG. 6   b  illustrates a connection relationship between the latching portion  300  and the outer body  100  in the latching operation according to various embodiments. When the oil in the oil chamber  360  is introduced into the latching pin  330  via an oil supply passage  350 , a hydraulic pressure is generated to push the latching pin  330 . At this time, the latching pin  330  compresses the return spring  320  against the return spring support pin  310 . 
     That is, the return spring support pin  310  is not moved, while the latching pin  330  is moved in the direction of the arrow in  FIG. 6   b . As such, the latching pin  330  is moved to a latching portion connecting groove  530  (see  FIG. 8 ), and the outer body  100  presses the latching pin  330  when a driving cam is operated. Thus, the inner body  200  with the latching pin  330  inserted therein also descends. By doing so, a latching mode, i.e., high lift, is performed. 
     On the other hand, in the unlatching operation, the oil in the latching pin  330  is discharged, as shown in  FIG. 6   a . Thus, the compressed return spring  320  is released. Following the release of the return spring  320 , the latching pin  330  returns to the original state. As a result, the latching pin  330  is inserted into the inner body  200 , and thus the inner body  200  is not affected at all even if the outer body  100  descends. That is, the outer body  100  creates lost motion. By doing so, low lift is achieved. 
     In the exemplary embodiment illustrated in  FIG. 7 , too, in the latching and unlatching modes, the inner body  600  is selectively latched to the outer body  500  by the movement of the latching portion  300  inserted into the inner body  600 . 
     An operating process of various embodiments will now be described with reference to the accompanying drawings. 
     As shown in  FIG. 1  and  FIG. 2 , the outer body  100  and the inner body  200  are hinged by the lost motion hinge shaft  110 . Thus, the outer body  100  and the front end of the inner body  200  rotate centering around the lost motion hinge shaft  110 . At this time, the inner body  200  controls the intake and exhaust device of a valve by pressing the valve member  400 . Moreover, the high cam  170  presses the outer body  100 , and the low cam  160  presses the inner body  200 . 
     As shown in  FIG. 6   b , in the latching of the outer body  100  and the inner body  200 , the latching pin  330  is exposed to the outside as the latching pin  330  compresses the return spring  320  by the hydraulic pressure generated when oil is supplied via the oil supply passage  350 . At this time, the return spring support pin  310  is fixed. In this state, if the outer body  100  descends, the outer body  100  presses the latching pin  330 . As a result, the inner body  100  with the latching pin  330  inserted therein descends too. In this way, high lift, which is the latching mode, is achieved. In this case, the low cam  160  and the inner body  200  are not in contact with each other. 
     On the other hand, the unlatching of the outer body  100  and the inner body  200  begins when the oil in the latching pin  330  is discharged. As the oil is discharged, the hydraulic pressure for compressing the return spring  320  is released, and therefore the return spring  320  is released. That is, the latching pin  330  returns to the original state, being supported on the return spring support pin  310 , by the restoring force of the return spring  320 . As a result, the latching pin  330  is inserted again into the inner body  200 , thereby unlatching the outer body  100  and the inner body  200 . In this way, low lift, which is the unlatching mode, is achieved. At this time, the outer body  100  creates lost motion, which is performed by the lost motion spring  120 . 
     With reference to  FIGS. 7-10 , an operating process of the illustrated exemplary embodiment of the present invention will be described below. It should be noted that the latching portion  300  of the illustrated exemplary embodiment is identical to those described above. 
     The difference between the illustrated exemplary embodiment and those described above is that the outer body  500  is adapted to press the valve member  400 . That is, in the above-described embodiments, the outer body  199 , which does not directly press the valve member  400 , creates lost motion since the inner body  200  presses the valve member  400 , whereas in the exemplary embodiment illustrated in  FIG. 7 , the inner body  600 , which is not in direct contact with the valve member  400 , creates lost motion. The lost motion created at this time is performed by the lost motion spring  540 . 
     Moreover, the low cam  520  presses the outer body  500 , and the high cam  510  presses the inner body  600 . 
     The operating process of the latching operation of the exemplary embodiment illustrated in  FIG. 7  will be discussed in more detail. As the latching pin  300  compresses the return spring  320  by the hydraulic pressure generated when oil is supplied to the latching pin  300  via the oil supply passage  550 , the latching pin  300  is inserted into the latching portion connecting groove  530  (see  FIG. 8 ). Thus, the outer body  500  and the inner body  600  are connected together. With the outer body  500  and the inner body  600  being connected together, the high cam  510  presses the inner body  600  while rotating. As a result, as shown in  FIG. 7 , when the outer body  500  rotates, it has the profile of an outer body  502  drawn in dotted line. In this way, the outer body  500  connected to the inner body  600  presses the valve member  400 , thereby achieving high lift. 
     In the unlatching operation of various embodiments, the return spring  320  is released as the oil is discharged via the oil supply passage  550 . By the releasing operation of the return spring  320 , the latching pin  330  returns to the original state. Thus, the outer body  500  and the inner body  600  are disconnected from each other. Therefore, the outer body  500  and the inner body  600  are independently operated, and the inner body  600  exerts no effect at all on the outer body  500  when the high cam  510  presses the inner body  600 . Thus, the inner body  600  creates lost motion. In this way, low lift is achieved. 
     As seen from above, when the outer body  100  and  500  and the inner body  200  and  600  are selectively connected together by the latching portion  300 , the lost motion hinge shaft  110  and a hinge point between the inner body  100  or outer body  500  and the hinge member  150  are disposed in the same direction relative to the camshaft. This reduces the moment of inertia, thus improving the dynamic characteristics. 
     In the present invention, the hinge point between the inner body  100  or outer body  500  and the hinge member  150  is referred to as the hinge point of the variable valve lift apparatus. 
     For convenience in explanation and accurate definition in the appended claims, the terms upper or lower, front or rear, and etc. 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.