Patent Publication Number: US-9835058-B2

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

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2015-0088630, filed on Jun. 22, 2015, which is incorporated herein by reference in its entirety. 
     FIELD 
     The present disclosure relates to a continuous variable valve lift apparatus and an engine provided with the same. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior 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. 
     Desired 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 desired 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 a desired 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 above information disclosed in this Background section is only for enhancement of understanding of the present disclosure and it may contain information that is not already known to a person of ordinary skill in the art. 
     SUMMARY 
     The present disclosure provides a continuous variable valve lift apparatus, and an engine provided with the apparatus may vary valve lift according to operation conditions of an engine, with a simple construction. 
     A continuously variable valve lift apparatus according to an embodiment of the present disclosure 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 and of which a position with respect to the camshaft is movable, a control portion selectively changing the position 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 a connecting pin connected with the camshaft and a spiral bearing mounted to the cam portion and of which the connecting pin is inserted therein. 
     The continuously variable valve lift apparatus may further include a bearing interposed between the cam portion and the slider housing. 
     The output portion may include an output roller contacting the cam. 
     A ball screw housing may be formed to the slider housing, and wherein the control portion may include a ball screw engaged with the ball screw housing and a control motor driving the ball screw. 
     The valve unit may include a swing arm roller contacting the valve shoe and a valve. 
     A rail may be formed to the slider housing for guiding movement of the slider housing. 
     The cam may be formed to both side of the cam portion the output portion may be configured as a pair to contact to each cam and the valve unit may be configured as a pair and each valve unit includes a swing arm roller contacting to each valve shoe of each output portion and a valve. 
     An engine according to an embodiment of the present disclosure 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 and of which a position with respect to the camshaft is movable on a cylinder head, a control portion selectively changing the position of the slider housing, an output portion rotatable around a pivot shaft connected to the cylinder head 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 a connecting pin connected with the camshaft and a spiral bearing mounted to the cam portion and of which the connecting pin is inserted therein. 
     The engine may further include a bearing interposed between the cam portion and the slider housing. 
     The output portion may include an output roller contacting the cam. 
     A ball screw housing may be formed to the slider housing, and wherein the control portion may include a ball screw engaged with the ball screw housing and a control motor driving the ball screw. 
     The valve unit may include a swing arm roller contacting the valve shoe and a valve. 
     A rail may be formed to the slider housing for guiding movement of the slider housing. 
     The cam may be formed to both side of the cam portion, the output portion may be configured as a pair to contact to each cam and the valve unit may be configured as a pair and each valve unit include a swing arm roller contacting to each valve shoe of each output portion and a valve. 
     As described above, a continuous variable valve lift apparatus according to an embodiment of the present disclosure may vary valve lift according to operation conditions of an engine, with a simple construction. 
     The continuous variable valve lift apparatus according to an embodiment of the present disclosure may reduce duration in minimum valve lift comparing to general continuous variable valve lift apparatuses. 
     The continuous variable valve lift apparatus according to an embodiment of the present disclosure 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 embodiment of the present disclosure 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. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a continuous variable valve lift apparatus; 
         FIG. 2  is an exploded perspective view of a continuous variable valve lift apparatus; 
         FIG. 3  is a cross-sectional view of a spiral bearing provided to a continuous variable valve lift apparatus; 
         FIG. 4  and  FIG. 5  are drawings showing operations in a low lift mode of a continuous variable valve lift apparatus; 
         FIG. 6  and  FIG. 7  are drawings showing operations in a high lift mode of a continuous variable valve lift apparatus; 
         FIG. 8  and  FIG. 9  are drawings showing mechanical motions of cams of a continuous variable valve lift apparatus; 
         FIG. 10  is a graph of a valve profile of a continuous variable valve lift apparatus; and 
         FIG. 11  is a graph of pressure volume diagram of an engine. 
     
    
    
     The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
     
       
         
           
               
             
               
                   
               
               
                 &lt;Description of symbols&gt; 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 1: engine 
                 10: cylinder head 
               
               
                   
                 30: camshaft 
                 32: connecting pin 
               
               
                   
                 40: cam portion 
                 42: cam 
               
               
                   
                 44: driving surface 
                 46: driving hole 
               
               
                   
                 50: output portion 
                 52: pivot shaft 
               
               
                   
                 54: valve shoe 
                 56: output roller 
               
               
                   
                 60: slider housing 
                 62: bearing 
               
               
                   
                 64: ball screw housing 
                 66: rail 
               
               
                   
                 80: spiral bearing 
                 82: inner wheel 
               
               
                   
                 84: outer wheel 
                 100: control portion 
               
               
                   
                 102; ball screw 
                 104: control motor 
               
               
                   
                 200: valve unit 
                 202: swing arm roller 
               
            
           
           
               
               
            
               
                   
                 204: valve 
               
               
                   
                   
               
            
           
         
       
     
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
     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 disclosure 
     A part irrelevant to the description will be omitted to clearly describe the present disclosure, 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. 
     Referring to  FIG. 1  to  FIG. 3 , an engine  1  according to an embodiment of the present disclosure includes a cylinder head  10  and a continuous variable valve lift apparatus mounted to the cylinder head  10 . 
     A continuously variable valve lift apparatus according to an embodiment of the present disclosure includes a camshaft  30 , a cam portion  40  on which a cam  42  is formed and to which the camshaft  30  is inserted, a slider housing  60  to which the cam portion  40  is rotatably inserted and a position of which is movable, a control portion  100  selectively changing the position of the slider housing  60 , an output portion  50  rotatable around a pivot shaft  52 , the output portion  50  having a valve shoe  54  formed thereto, and a valve unit  200  configured to be driven by the valve shoe  54 . 
     The pivot shaft  52  is rotatably mounted to the cylinder head  10 , and the cylinder head  10  includes a cam carrier. 
     A rail  66  is formed on the slider housing  60  and the slider housing  60  is movable on the cylinder head  10 . 
     As shown in  FIG. 1  and  FIG. 2 , the cam  42  may be formed on both sides of the cam portion  40 , the output portion  50  may be configured as a pair to contact each of cams  42  and the valve unit  200  is configured as a pair and each valve unit  200  may be configured as a pair and two valve unit  200  may contact the output portion  50  respectively so as to be driven. 
     A connecting pin  32  is connected to the camshaft  30  and a spiral bearing  80  to which the connecting pin  32  is inserted is mounted to the cam portion  40 . 
     The spiral bearing  80  may include an outer wheel  84  connected to driving hole  46  of the cam portion  40  and an inner wheel  82  rotatably connected to the outer wheel  84 . The connecting pin  32  is slidable in the inner wheel  82 . 
     A bearing  62  is interposed between the cam portion  40  and a driving surface  44  of the slider housing  60 . 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 output portion  50  includes an output roller  56  contacting the cam  42  and changes a rotary motion of the cam  42  to a swing motion around the pivot shaft  52 . 
     A ball screw housing  64  is formed on the slider housing  60 , the control portion  100  includes a ball screw  102  engaged with the ball screw housing  64 , and a control motor  104  drives the ball screw  102 . The position of the slider housing  60  may be changed according to the operation of the control motor  104 . 
     The valve unit  200  may be a swing arm including a swing arm roller  202  contacting the valve shoe  54  and a valve  204 . 
       FIG. 4  and  FIG. 5  are drawings showing operations in a low lift mode of a continuous variable valve lift apparatus according to an embodiment of the present disclosure, and  FIG. 6  and  FIG. 7  are drawings showing operations in a high lift mode of a continuous variable valve lift apparatus. 
       FIG. 8  and  FIG. 9  are drawings showing mechanical motions of cams of a continuous variable valve lift apparatus, and  FIG. 10  is a graph of a valve profile of a continuous variable valve lift apparatus. 
     Referring to  FIG. 1  to  FIG. 10 , operations of the continuously variable valve lift apparatus according to an embodiment of the present disclosure will be described. 
     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 in  FIG. 4  and  FIG. 5 , for example, in low lift mode the slider housing  60  moves to the right direction according to the operation of the control portion  100 . 
     Since the camshaft  30  is connected to the connecting pin  32  and the connecting pin  32  is connected to the spiral bearing  80 , thus 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 slider housing  60  moves to right direction, 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  as well as a contacting position of the cam  42  and the output roller  56  are changed. 
     That is, as shown in  FIG. 8 , while a rotation center X of the cam shaft  30  is constant, however a rotation center of the cam  42  is changed to the right direction at Y 1 . Thus the contacting position of the cam  42  and the output roller  56  and the contacting position of the valve shoe  54  and the swing arm roller  202  are changed. 
     As shown in  FIG. 4  and  FIG. 5 , for example, in high lift mode the slider housing  60  moves to the right direction according to the operation of the control portion  100 . 
     As shown in  FIG. 6  and  FIG. 7 , for example, in high lift mode the slider housing  60  moves to the left direction according to the operation of the control portion  100 . 
     Since the slider housing  60  moves to left direction, 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  as well as the contacting position of the cam  42  and the output roller  56  are changed. 
     That is, as shown in  FIG. 9 , while the rotation center X of the cam shaft  30  is constant, however the rotation center of the cam  42  is changed to the right direction at Y 2 . Thus the contacting position of the cam  42  and the output roller  56  and the contacting position of the valve shoe  54  and the swing arm roller  202  are changed. 
     As shown in  FIG. 10 , 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. 10 , however it is not limited thereto. The relative position of the slider housing  60  may perform various valve profile. 
     As shown in  FIG. 10 , 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 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 . 
     So that the continuous variable valve lift apparatus according to an embodiment of the present disclosure may reduce pumping loss and enhance fuel economy. 
       FIG. 11  is a graph of pressure volume diagram of an engine. 
     As shown in  FIG. 11 , 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 the present disclosure 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. 
     While this present disclosure has been described in connection with what is presently considered to be practical embodiments, it is to be understood that the present disclosure is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.