Patent Publication Number: US-9890670-B2

Title: Continuous variable valve lift apparatus and engine provided with the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Korean Patent Application No. 10-2015-0133340 filed Sep. 21, 2015, the entire contents of which is incorporated herein for all purposes by this reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a continuous variable valve lift apparatus and an engine provided with the same. More particularly, the present invention relates to a continuous variable valve lift apparatus an engine provided with the same which may vary valve lift according to operation conditions of an engine with a simple construction. 
     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. 
     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. In order to achieve such optimal valve operation depending on the rotation speed of the engine, various researches, such as designing of a plurality of cams and a continuous variable valve lift (CVVL) that can change valve lift according to engine speed, have been undertaken. 
     Also, in order to achieve such an optimal valve operation depending on the rotation speed of the engine, research has been undertaken on a continuously variable valve timing (CVVT) apparatus that enables different valve timing operations depending on the engine speed. The general CVVT may change valve timing with a fixed valve opening duration. 
     However, the general CVVL and CVVT are complicated in construction and are expensive in manufacturing cost. 
     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 
     Various aspects of the present invention are directed to providing a continuous variable valve lift apparatus and an engine provided with the same which may vary valve lift according to operation conditions of an engine, with a simple construction. 
     According to various aspects of the present invention, a continuously variable valve lift apparatus may include a camshaft, a cam portion on which a cam is formed and into which the camshaft is inserted, a slider housing into which the cam portion is rotatably inserted and of which a position is rotatable around a pivot shaft, a control portion engaged with the slider housing and configured to selectively rotate the slider housing around the pivot shaft, an output portion rotatable around the pivot shaft, contacting the cam and onto which a valve shoe is formed, and a valve device contacting the valve shoe and driven by rotation of the cam. 
     A slider gear may be formed to the slider housing, and the control portion may include a gear lifter onto which a control gear engaged with the slider gear is formed. 
     A center of tooth of the slider gear is the pivot shaft. 
     The continuously variable valve lift apparatus may further include a connecting pin connected to the camshaft, and a spiral bearing mounted to the cam portion and into which the connecting pin is inserted. 
     The spiral bearing may include an outer wheel connected to a driving hole formed to the cam portion, and an inner wheel rotatably connected to the outer wheel and in which the connecting pin is slidably disposed. 
     The continuously variable valve lift apparatus may further include a bearing disposed between the cam portion and the slider housing. 
     The output portion may include an output roller contacting the cam. 
     The continuously variable valve lift apparatus may further include a spring bracket connected to the slider housing, and a torsion spring connected to the spring bracket for the output portion to contact the cam. 
     The valve device may be a swing arm comprising a swing arm roller contacting the valve shoe and a valve. 
     The slider housing may be disposed as a pair, and the cam portion may include a center portion formed to a center thereof, and two rotation portions formed on both sides of the cam portion and rotatably disposed within each slider housing of the pair, and cams of the cam as a pair may be formed between the center portion and each rotation portion. 
     The continuously variable valve lift apparatus may further include a connecting pin connected to the camshaft, and a spiral bearing mounted to the center portion and into which the connecting pin is inserted. 
     The continuously variable valve lift apparatus may further include a spring bracket connected to each slider housing, and a torsion spring connected to the spring bracket for each output portion to contact each cam. 
     The output portion may be disposed as a pair and each output portion of the pair contacts each the cam, and the valve device may be a swing arm disposed as a pair and include a swing arm roller contacting the valve shoe and a valve. 
     According to various aspects of the present invention, an engine may include a camshaft, a cam portion on which a cam is formed and into which the camshaft is inserted, a slider housing into which the cam portion is rotatably inserted, of which a position is rotatable around a pivot shaft and on which a slider gear is formed, a control portion including a gear lifter on which a control gear engaged with the slider housing is formed, the control portion configured to selectively rotate the slider housing around the pivot shaft, an output portion rotatable around the pivot shaft, contacting the cam and on which a valve shoe is formed, and a valve device contacting the valve shoe and configured to be driven by rotation of the cam. 
     The slider housing may be disposed as a pair and each slider housing of the pair is rotatable around the pivot shaft, two rotation portions rotatably disposed within each slider housing may be formed on both sides of the cam portion, the cam may be formed to the cam portion as a pair and a center portion may be formed between the cams, the output portion may be disposed as a pair and contact each cam, and the valve device may be a swing arm disposed as a pair and include a swing arm roller contacting to the valve shoe and a valve. 
     The engine may further include a spring bracket connected to the slider housings, and a torsion spring connected to the spring bracket for each output portion to be contacted with each cam. 
     The engine may further include a connecting pin connected to the camshaft, and a spiral bearing mounted to the center portion and into which the connecting pin is inserted, in which the spiral bearing may include an outer wheel connected to a driving hole formed to the center portion, and an inner wheel rotatably connected to the outer wheel and in which the connecting pin is slidably disposed. 
     The engine may further include a bearing disposed between the cam portion and the slider housing. 
     As described above, a continuous variable valve lift apparatus according to various embodiments of the present invention may vary valve lift according to operation conditions of an engine, with a simple construction. 
     The continuous variable valve lift apparatus according to various embodiments of the present invention may reduce duration in minimum valve lift comparing to general continuous variable valve lift apparatuses. 
     The continuous variable valve lift apparatus according to various embodiments of the present invention may advance closing timing of an intake valve so that may reduce pumping loss and enhance fuel economy. 
     The continuous variable valve lift apparatus according to various embodiments of the present invention may be reduced in size and thus the entire height of a valve train may be reduced. 
     Since the continuous variable valve lift apparatus may be applied to an existing engine without excessive modification, thus productivity may be enhance and production cost may be reduced. 
     It is understood that the term “vehicle” or “vehicular” or other similar terms as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuel derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example, both gasoline-powered and electric-powered vehicles. 
     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 continuous variable valve lift apparatus according to the present invention. 
         FIG. 2  is an exploded perspective view of the exemplary continuous variable valve lift apparatus according to the present invention. 
         FIG. 3  is a drawing showing a slider housing applied to the exemplary continuous variable valve lift apparatus according to the present invention. 
         FIG. 4  is a cross-sectional view of a spiral bearing provided to the exemplary continuous variable valve lift apparatus according to the present invention. 
         FIG. 5  is a front view of the exemplary continuous variable valve lift apparatus according to the present invention operated in a high lift mode. 
         FIG. 6  is a cross-sectional view along line-of  FIG. 1  showing operations in the high lift mode of the exemplary continuous variable valve lift apparatus according to the present invention. 
         FIG. 7  is a front view of the exemplary continuous variable valve lift apparatus according to the present invention operated in a low lift mode. 
         FIG. 8  is a cross-sectional view along line-of  FIG. 1  showing operations in the low lift mode of the exemplary continuous variable valve lift apparatus according to the present invention. 
         FIG. 9  is a graph of a valve profile of the exemplary continuous variable valve lift apparatus according to the present invention. 
         FIG. 10  is a graph of pressure volume diagram of an engine provided with the exemplary continuous variable valve lift apparatus according to the present invention. 
     
    
    
     It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. 
     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 the 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 perspective view of a continuous variable valve lift apparatus according to various embodiments of the present invention and  FIG. 2  is an exploded perspective view of a continuous variable valve lift apparatus according to various embodiments of the present invention. 
       FIG. 3  is a drawing showing a slider housing applied to a continuous variable valve lift apparatus according to various embodiments of the present invention and  FIG. 4  is a cross-sectional view of a spiral bearing provided to a continuous variable valve lift apparatus according to various embodiments of the present invention. 
     Referring to  FIG. 1  to  FIG. 4 , an engine  1  according to various embodiments of the present invention includes a cylinder head  10  and a continuous variable valve lift apparatus mounted to the cylinder head  10 . 
     The continuously variable valve lift apparatus according to various embodiments of the present invention includes a camshaft  30 , a cam portion  40  of which a cam  42  is formed thereto and the camshaft  30  is inserted into therein, a slider housing  60  of which the cam portion  40  is rotatably inserted therein and of which a position is rotatable around a pivot shaft  52 , a control portion  100  engaged with the slider housing  60  and selectively rotating the slider housing  60  around the pivot shaft  52 , an output portion  50  rotatable around the pivot shaft  52 , contacting to the cam  42  and of which a valve shoe  54  is formed thereto and a valve device  200  contacting to the valve shoe  54  and driven by rotation of the cam  54 . 
     In the detailed description and claims, the cylinder head  10  is interpreted as including a cam carrier. 
     A slider gear  64  is formed to the slider housing  60 , and the control portion  100  includes a gear lifter  104  of which a control gear  102  engaged with the slider gear  64  is formed thereto. 
     A rotation hole  61  is formed to the slider housing  60  and the pivot shaft  52  is inserted thereto. 
     Referring to  FIG. 3 , a center of tooth of the slider gear  64  is the pivot shaft  54 . That is, when a control motor or an actuator rotates the gear lifter  104  according to operation state of the engine, the slider housing  60  engaged with the control gear  102  through the slider gear  64  which rotates around the pivot shaft  52 . 
     A connecting pin  32  is connected to the camshaft  30  and a spiral bearing  80  is mounted to the cam portion  40  and the connecting pin  32  is inserted into the spiral bearing  80 . 
     A center portion  48  is formed to a center of the cam portion  40  and the spiral bearing  80  include an outer wheel  84  connected to a driving hole  46  formed to the center portion  48  and an inner wheel  82  rotatably connected to the outer wheel  84  and of which the connecting pin  32  is slidably disposed therein. 
     The output portion  50  includes an output roller  56  contacting to the cam  42 . 
     A spring bracket  66  is connected to the slider housing  60  and a torsion spring  68  is connected to the spring bracket  66  through bolts  67  for the output portion  50  to be contacted with the cam  42 . 
     The valve device  200  may be a swing arm including a swing arm roller  202  contacting to the valve shoe  54  and a valve  204 . 
     A bearing  62  is disposed between the cam portion  40  and the slider housing  62 . Thus, rotation of the cam portion  40  may be easily performed. In the drawings, the bearing  62  is depicted as a needle bearing, however it is not limited thereto. On the contrary, various bearings such as a ball bearing, a roller bearing and so on may be applied thereto. 
     The slider housing  60  is disposed as a pair and the cam portion  40  includes a center portion  48  formed to a center thereof and two rotation portions  44  formed both sides of the cam portion  40  and rotatably disposed within each slider housing  60 . And the cam  42  as a pair is formed between the center portion  48  and each rotation portion  44 . 
     The output portion  50  may be disposed as a pair contacting to each cam  42  and the valve device  200  may be two swing arms. 
       FIG. 5  is a front view of a continuous variable valve lift apparatus according to various embodiments of the present invention operated in high lift mode and  FIG. 6  is a cross-sectional view along line-of  FIG. 1  showing operations in a high lift mode of a continuous variable valve lift apparatus according to various embodiments of the present invention. 
       FIG. 7  is a front view of a continuous variable valve lift apparatus according to various embodiments of the present invention operated in low lift mode and  FIG. 8  is a cross-sectional view along line-of  FIG. 1  showing operations in a low lift mode of a continuous variable valve lift apparatus according to various embodiments of the present invention. 
     Hereinafter, referring to  FIG. 1  to  FIG. 8 , operations of the continuously variable valve lift apparatus according to various embodiments of the present invention will be described. 
     When the rotation centers of the camshaft  30  and the cam portion  40  are coincident, the valve  204  realizes a predetermined valve lift profile. 
     According to engine operation states, the (Engine Control Unit or Electronic Control Unit) ECU transmits control signals to the control portion  100  to change the relative position of the slider housing  60 . As shown  FIG. 6  and in  FIG. 6 , for example, in high lift mode requiring high power, the slider housing  60  rotates in a clockwise direction around the pivot shaft  52  according to the operation of the control portion  100 . 
     Then the rotation centers of the camshaft  30  and the cam portion  40  are not coincident, the rotation of the camshaft  30  is transmitted to the cam portion  40  through the connecting pin  32  and the spiral bearing  80 . 
     Since the relative rotation of the cam  42  is changed, the output portion  50  relatively rotates in a clockwise direction around the pivot shaft  52 . 
     Since the output portion  50  relatively rotates in the clockwise direction around the pivot shaft  52 , the contacting position of the valve shoe  54  to the swing arm roller  202  are changed to the right direction. 
     As shown  FIG. 7  and in  FIG. 8 , for example, in low lift mode requiring low power, the slider housing  60  rotates in an anticlockwise direction around the pivot shaft  52  according to the operation of the control portion  100 . 
     Then the rotation centers of the camshaft  30  and the cam portion  40  are not coincident, the rotation of the camshaft  30  is transmitted to the cam portion  40  through the connecting pin  32  and the spiral bearing  80 . 
     Since the relative rotation of the cam  42  is changed, the output portion  50  relatively rotates in an anticlockwise direction around the pivot shaft  52 . 
     Since the output portion  50  relatively rotates in the counterclockwise direction around the pivot shaft  52 , the contacting position of the valve shoe  54  to the swing arm roller  202  are changed to the left direction. 
     In various embodiments of the present invention, according to the relative position of the slider housing  60  with respect to the camshaft  30 , the rotation center of the cam  42  is changed and thus a contacting position of the output roller  56  and the cam  42  is changed. Thus, when the operation mode of the continuously variable valve lift apparatus is changed to the low lift mode, valve closing timing may be advanced. 
     Also, since the contacting position of the swing arm roller  202  and the valve shoe  54  is changed, the valve lift is adjusted. 
       FIG. 9  is a graph of a valve profile of a continuous variable valve lift apparatus according to various embodiments of the present invention. 
     A high lift profile A or a low lift profile B of the valve  204  may be performed according to the relative rotation center of the cam  42  with respect to the camshaft  30 , relative positions of the camshaft  30  and the output roller  56  and the contacting position of the valve shoe  54  and the swing arm roller  202 . 
     While only the high lift profile A and the low lift profile B are shown in  FIG. 9 , however it is not limited thereto. The relative position of the slider housing  60  may perform various valve profiles. 
     As shown in  FIG. 9 , comparing to a valve duration C of a general continuously variable valve lift apparatus in the low lift mode, a valve duration D of the continuously variable valve lift apparatus according to various embodiments of the present invention may be reduced. 
     And valve closing time may be advanced comparing to valve closing time of the general continuously variable valve lift apparatus in the low lift mode due to contacting position change of the cam  42  and the output roller  56 . Thus, pumping lose may be reduced and enhancement of fuel consumption may be realized. 
       FIG. 10  is a graph of pressure volume diagram of an engine provided with the continuous variable valve lift apparatus. 
     As shown in  FIG. 10 , an engine provided with a continuous variable valve lift apparatus may reduce pumping loss F comparing to pumping loss E of an engine without a continuous variable valve lift apparatus. 
     However, the continuously variable valve lift apparatus may reduce valve duration and advance valve closing time so that may reduce pumping loss G and may enhance fuel economy. 
     The continuous variable valve lift apparatus according to various embodiments of the present invention may be reduced in size and thus the entire height of a valve train may be reduced. 
     Since the continuous variable valve lift apparatus may be applied to an existing engine without excessive modification, thus productivity may be enhance and production cost may be reduced. 
     For convenience in explanation and accurate definition in the appended claims, the terms “upper” or “lower”, “inner” or “outer” 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.