Patent Publication Number: US-9890669-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 and the benefit of Korean Patent Application No. 10-2015-0129217 filed on Sep. 11, 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 directly 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. 
     A continuously variable valve lift apparatus according to an exemplary embodiment of the present invention may include a camshaft, a cam portion of which a cam is formed thereto and the camshaft is inserted into therein, a slider housing of which the cam portion is rotatably inserted therein, of which a position with respect to the camshaft is movable and of which a guide slot is formed thereto, a control portion selectively changing the position of the slider housing, a guide shaft disposed parallel to the camshaft and inserted into the guide slot for guiding movement of the slider housing, an output portion rotatable around a pivot shaft and of which a valve shoe is formed thereto and a valve unit configured to be driven by the valve shoe. 
     The continuously variable valve lift apparatus may further include an inner bracket rotatably disposed within the slider housing, and wherein the inner bracket may transmit rotation of the camshaft to the cam portion. 
     A camshaft hole may be formed to the camshaft, a cam portion hole may be formed to the cam portion and a pin hole may be formed to the inner bracket, and wherein the continuously variable valve lift apparatus may further include a pin slider rotatably disposed within the pin hole and of which a slider hole is formed thereto and a connecting pin connected to the camshaft hole and slidably inserted into the cam portion hole and the slider hole. 
     The continuously variable valve lift apparatus may further include a bearing inserted between the inner bracket and the slider housing. 
     The valve shoe may be formed as a pair and the valve unit may be disposed as a pair and each valve unit may include a swing arm roller contacting each valve shoe. 
     The continuously variable valve lift apparatus may further include an output roller mounted between the valve shoes and contacting to the cam. 
     An engine according to an exemplary embodiment of the present invention may include a camshaft, a cam portion of which a cam is formed thereto and the camshaft is inserted into therein, a slider housing of which the cam portion is rotatably inserted therein, of which a position with respect to the camshaft is movable and of which a guide slot is formed thereto, a control portion selectively changing the position of the slider housing, a guide shaft disposed parallel to the camshaft and inserted into the guide slot for guiding movement of the slider housing, an output portion rotatable around a pivot shaft and of which a valve shoe is formed thereto and a valve unit configured to be driven by the valve shoe. 
     The engine may further include an inner bracket rotatably disposed within the slider housing, and wherein the inner bracket may transmit rotation of the camshaft to the cam portion. 
     A camshaft hole may be formed to the camshaft, a cam portion hole may be formed to the cam portion and a pin hole may be formed to the inner bracket, and wherein the continuously variable valve lift apparatus may further include a pin slider rotatably disposed within the pin hole and of which a slider hole is formed thereto and a connecting pin connected to the camshaft hole and slidably inserted into the cam portion hole and the slider hole. 
     The engine may further include a bearing inserted between the inner bracket and the slider housing. 
     The valve shoe may be formed as a pair and the valve unit may be disposed as a pair and each valve unit may include a swing arm roller contacting each valve shoe. 
     The engine may further include an output roller mounted between the valve shoes and contacting to the cam. 
     The control portion may include an eccentric shaft rotatably connected to the slider housing and a motor selectively rotating the eccentric shaft. 
     As described above, a continuous variable valve lift apparatus according to an exemplary embodiment 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 an exemplary embodiment 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 an exemplary embodiment 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 an exemplary embodiment 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. 
     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 a continuous variable valve lift apparatus according to an exemplary embodiment of the present invention. 
         FIG. 2  is an exploded perspective view of a continuous variable valve lift apparatus according to an exemplary embodiment of the present invention. 
         FIG. 3  is a cross-sectional view along line III-III of  FIG. 1  describing a continuously variable valve lift apparatus according to an exemplary embodiment of the present invention operated in low lift mode. 
         FIG. 4  is a cross-sectional view along line IV-IV of  FIG. 1  describing a continuously variable valve lift apparatus according to an exemplary embodiment of the present invention operated in low lift mode. 
         FIG. 5  is a cross-sectional view along line V-V of  FIG. 1  describing a continuously variable valve lift apparatus according to an exemplary embodiment of the present invention operated in high lift mode. 
         FIG. 6  is a cross-sectional view along line VI-VI of  FIG. 1  describing a continuously variable valve lift apparatus according to an exemplary embodiment of the present invention operated in high lift mode. 
         FIG. 7  is a graph of a valve profile of a continuous variable valve lift apparatus according to an exemplary embodiment of the present invention. 
         FIG. 8  is a graph of pressure volume diagram of an engine. 
     
    
    
     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. 
     In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. 
     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. 
     In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. 
     As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention 
     A part irrelevant to the description will be omitted to clearly describe the present invention, and the same or similar elements will be designated by the same reference numerals throughout the specification. 
     In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. 
     Throughout the specification and the claims, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. 
     An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a perspective view of a continuous variable valve lift apparatus according to an exemplary embodiment of the present invention and  FIG. 2  is an exploded perspective view of a continuous variable valve lift apparatus according to an exemplary embodiment of the present invention. 
       FIG. 3  is a cross-sectional view along line III-III of  FIG. 1  describing a continuously variable valve lift apparatus according to an exemplary embodiment of the present invention operated in low lift mode and  FIG. 4  is a cross-sectional view along line IV-IV of  FIG. 1  describing a continuously variable valve lift apparatus according to an exemplary embodiment of the present invention operated in low lift mode. 
     Referring to  FIG. 1  to  FIG. 4 , an engine  1  according to an exemplary embodiment 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 an exemplary embodiment 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, of which a position with respect to the camshaft  30  is movable and of which a guide slot  64  is formed thereto, a control portion  100  selectively changing the position of the slider housing  60 , a guide shaft  66  disposed parallel to the camshaft  30  and inserted into the guide slot  64  for guiding movement of the slider housing  60 , an output portion  50  rotatable around a pivot shaft  52  and of which a valve shoe  54  is formed thereto and a valve unit  200  configured to be driven by the valve shoe  54 . 
     A mounting bracket  90  is connected to the cylinder head  10 , a bracket hole  91  is formed to the mounting bracket  90  and the pivot shaft  52  is inserted into the bracket hole  91 . In the detailed description and claims, the cylinder head  10  is interpreted as including a cam carrier. 
     A shaft hole  58  is formed to the output portion  50  and the pivot shaft  52  is inserted into the shaft hole  58 . 
     An inner bracket  70  is rotatably inserted into the slider housing  60  and the inner bracket  70  transmits rotation of the camshaft  30  to the cam portion  40 . 
     A camshaft hole  32  is formed to the camshaft  30 , a cam portion hole  44  is formed to the cam portion  40  and a pin hole  72  is formed to the inner bracket  70 . 
     A pin slider  80  of which a slider hole  82  is formed thereto is rotatably disposed within the pin hole  72 . And a connecting pin  32  is connected to the camshaft hole  32  and is slidably inserted into the cam portion hole  44  and the slider hole  82 . 
     A bearing  62  is interposed between the inner bracket  70  and the slider housing  60 . Thus, rotation of the inner bracket  70  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 valve shoe  54  may be formed as a pair and the valve unit  200  may be disposed as a pair and each valve unit  200  includes a swing arm roller  202  contacting each valve shoe  54 . 
     Roller holes  57  are formed to the output portion  50  and an output roller  56  contacting the cam  42  is mounted between the valve shoes  54  through the roller holes  57 . 
     The control portion  100  includes an eccentric shaft  102  rotatably connected to the slider housing  60  and a control motor  104  or an actuator selectively rotates the eccentric shaft  102  for changing the position of the slider housing  60 . 
     A connecting cap  92  may be connected to the slider housing  60  and the eccentric shaft  102  may be rotatably disposed between the slider housing  60  and the connecting cap  92 . 
       FIG. 5  is a cross-sectional view along line V-V of  FIG. 1  describing a continuously variable valve lift apparatus according to an exemplary embodiment of the present invention operated in high lift mode,  FIG. 6  is a cross-sectional view along line VI-VI of  FIG. 1  describing a continuously variable valve lift apparatus according to an exemplary embodiment of the present invention operated in high lift mode and  FIG. 7  is a graph of a valve profile of a continuous variable valve lift apparatus according to an exemplary embodiment of the present invention. 
     Hereinafter, referring to  FIG. 1  to  FIG. 7 , operations of the continuously variable valve lift apparatus according to an exemplary embodiment of the present invention will be described. 
     When rotation centers of the camshaft  30  and the slider housing  60  are coincident, the valve  204  realizes a predetermined valve lift profile. 
     According to engine operation states, the ECU transmits control signals to the motor  104  of the control portion  100  to change the relative position of the slider housing  60 . 
     As shown  FIG. 4  and in  FIG. 5 , for example, in low lift mode the slider housing  60  moves to the down direction according to the operation of the control portion  100 . Thus, the rotation center of the slider housing  60  with respect to the rotation center X of the camshaft  30  is changed to Y 1 . 
     Since the connecting pin  34  is slidable within the cam portion hole  44  and the slider hole  82  and the pin slider  80  is rotatable within the pin hole  72 , the rotation of the camshaft  30  is transmitted to the cam portion  40  through the connecting pin  34 . 
     The camshaft  30  rotates around the center X and the cam  42  rotates around the changed rotation center Y 1 . 
     Since the relative rotation of the cam  42  is changed, the output portion  50  relatively rotates in a counterclockwise direction around the pivot shaft  52 . 
     Since the output portion  50  relatively rotates in a counterclockwise direction around the pivot shaft  52 , a contacting position of the valve shoe  54  and the swing arm roller  202  are changed to the left direction. 
     As shown in  FIG. 5  and  FIG. 6 , for example, in high lift mode the slider housing  60  moves to the upward direction according to the operation of the control portion  100 . Thus, rotation center Y 2  of the slider housing  60  relatively moves upward with respect to the rotation center X of the camshaft  30 . 
     Since the connecting pin  34  is slidable within the cam portion hole  44  and the slider hole  82  and the pin slider  80  is rotatable within the pin hole  72 , the rotation of the camshaft  30  is transmitted to the cam portion  40  through the connecting pin  34 . 
     The camshaft  30  rotates around the center X and the cam  42  rotates around the changed rotation center Y 2 . 
     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 a clockwise direction around the pivot shaft  52 , the contacting position of the valve shoe  54  and the swing arm roller  202  are changed to the right direction. 
     In the exemplary embodiment of the present invention, according to the relative position of the slider housing  60  with respect to the camshaft  30 , the rotation center Y 1  and Y 2  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. 
     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 are shown in  FIG. 7 , however it is not limited thereto. The relative position of the slider housing  60  may perform various valve profile. 
     As shown in  FIG. 7 , 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 an exemplary embodiment 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 . 
       FIG. 8  is a graph of pressure volume diagram of an engine. 
     As shown in  FIG. 8 , 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 an exemplary embodiment 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. 
     In the exemplary embodiment of the present invention, since valve lifts of two cams may be controlled using one cam and one slider housing, thus total numbers of elements may be reduced. 
     For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “inner” and “outer” 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.