Patent Publication Number: US-9850789-B2

Title: Continuous variable valve duration 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. 10-2015-0135844 filed on Sep. 24, 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 duration apparatus and an engine provided with the same. More particularly, the present invention relates to a continuous variable valve duration apparatus an engine provided with the same which may vary opening duration of a valve 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 duration apparatus and an engine provided with the same which may vary opening duration of a valve according to operation conditions of an engine, with a simple construction. 
     A continuous variable valve duration apparatus an exemplary embodiment of the present invention may include a camshaft, a first and second cam portions of a cam is formed thereto respectively, of which the camshaft is inserted thereto and of which relative phase angles with respect to the camshaft are variable, a first and second inner brackets transmitting rotation of the camshaft to the first and second cam portions respectively, a first and second slider housings of which the first and second inner brackets are rotatably inserted thereto and of which relative position with respect to the camshaft are variable, a cam cap rotatably supporting the first and second cam portions respectively and of which each slider housing is slidably mounted thereto, a control shaft disposed parallel to the camshaft and engaged with the first and second slider housings for selectively moving the first and second slider housings and a control portion selectively rotating the control shaft for changing positions of the inner brackets. 
     A cam key may be formed to the first and second cam portions respectively and a first sliding hole may be formed to the first and second inner brackets respectively and wherein the continuous variable valve duration apparatus may further include a cam key pin of which a cam key slot where the cam key is slidably inserted therein is formed thereto and the cam key pin rotatably inserted into the each first sliding hole. 
     A second sliding hole may be formed to the first and second inner brackets respectively, and wherein the continuous variable valve duration apparatus may further include a plurality of camshaft pin connected to the camshaft and a slider pin of which a camshaft pin slot where the camshaft pin is slidably inserted therein is formed thereto and the slider pin rotatably inserted into the each second sliding hole. 
     A shaft hole where the control shaft is inserted into may be formed to the cam cap. 
     The continuous variable valve duration apparatus may further include a shaft bearing inserted into the shaft hole and rotatably supporting the control shaft. 
     A guide slot may be formed to the cam cap, a guide shaft inserted into the guide slot and of which a rack gear is formed thereto may be protruded from the slider housing and a pinion gear may be formed to the control shaft and engaged with the rack gear and wherein the positions of the slider housings may be changed according to rotation of the control shaft. 
     The continuous variable valve duration apparatus may further include a bushing inserted into the guide slot for reducing frictional force of the movement of the guide shaft. 
     The continuous variable valve duration apparatus may further include a stopper disposed to the cam cap for limiting the movement of the slider housing. 
     The continuous variable valve duration apparatus may further include a slider housing bearing disposed between the slider housing and the first and second inner brackets respectively. 
     The cam may be formed as a pair, a cam cap connecting portion may be formed between the two cams of the cam portions and the cam cap may rotatably support the cam cap connecting portion. 
     The control portion may include a worm wheel connected to the control shaft, a worm gear engaged with the worm wheel and a control motor selectively rotating the worm gear. 
     The continuous variable valve duration apparatus may further include a partition disposed within the first and second slider housings respectively for preventing from interrupting of the rotations of the inner brackets. 
     An engine an exemplary embodiment of the present invention may include a camshaft, two first and second cam portions of a cam is formed thereto respectively, of which the camshaft is inserted thereto, of which relative phase angles with respect to the camshaft are variable and a cam key is formed thereto respectively, a plurality of camshaft pin connected to the camshaft, a first and second inner brackets transmitting rotation of the camshaft pins to the cam keys respectively, a first and second slider housings of which the first and second inner brackets are rotatably inserted thereto and of which relative position with respect to the camshaft are variable, cam caps rotatably supporting the first and second cam portions together with a cylinder head and of which the slider housings are slidably mounted thereto respectively, a control shaft disposed parallel to the camshaft and engaged with the first and second slider housings for selectively moving the first and second slider housings and a control portion selectively rotating the control shaft for changing positions of the inner brackets. 
     The control portion may include a worm wheel connected to the control shaft, a worm gear engaged with the worm wheel and a control motor selectively rotating the worm gear. 
     A first and second sliding holes may be formed to the first and second inner brackets respectively, and wherein the continuous variable valve duration apparatus may further include a cam key pin of which a cam key slot where the cam key is slidably inserted therein is formed thereto and the cam key pin rotatably inserted into the each first sliding hole and a slider pin of which a camshaft pin slot where the camshaft pin is slidably inserted therein is formed thereto and the slider pin rotatably inserted into the each second sliding hole. 
     The engine may further include a slider housing bearing disposed between the slider housing and the first and second inner brackets respectively. 
     The cam may be formed as a pair, a cam cap connecting portion may be formed between the two cams of the cam portions and wherein cam cap connecting portion may be rotatably disposed between the cam cap and the cylinder housing. 
     A guide slot may be formed to the cam cap and a shaft hole where the control shaft is inserted into may be formed to the cam cap, and wherein the engine may further include a shaft bearing inserted into the shaft hole and rotatably supporting the control shaft. 
     A guide slot may be formed to the cam cap, a guide shaft inserted into the guide slot and of which a rack gear is formed thereto may be protruded from the slider housing and a pinion gear may be formed to the control shaft and engaged with the rack gear and wherein the positions of the slider housings may be changed according to rotation of the control shaft. 
     A guide surface may be formed to the first and second slider housings and a guider may be formed to the cylinder head for contacting the guide surface and guiding movements of the first and second slider housings. 
     As described above, a continuous variable valve duration apparatus according to an exemplary embodiment of the present invention may vary an opening duration of a valve according to operation conditions of an engine, with a simple construction. 
     The continuous variable valve duration 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 duration 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 an engine provided with a continuous variable valve duration apparatus according to an exemplary embodiment of the present invention. 
         FIG. 2  is a perspective view of a continuous variable valve duration apparatus according to an exemplary embodiment of the present invention. 
         FIG. 3  and  FIG. 4  are exploded perspective views of a continuous variable valve duration apparatus according to an exemplary embodiment of the present invention. 
         FIG. 5  is a cross-sectional view along line V-V of  FIG. 1 . 
         FIG. 6  is a cross-sectional view along line VI-VI of  FIG. 1 . 
         FIG. 7  and  FIG. 8  are drawings showing mechanical motions of cams of a continuous variable valve duration apparatus according to an exemplary embodiment of the present invention. 
         FIG. 9  and  FIG. 10  are graphs of a valve profile of a continuous variable valve duration apparatus according to an exemplary embodiment of 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. 
     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 an engine provided with a continuous variable valve duration apparatus according to an exemplary embodiment of the present invention and  FIG. 2  is a perspective view of a continuous variable valve duration apparatus according to an exemplary embodiment of the present invention. 
       FIG. 3  and  FIG. 4  are exploded perspective views of a continuous variable valve duration apparatus according to an exemplary embodiment of the present invention and  FIG. 5  is a cross-sectional view along line V-V of  FIG. 1 . 
     Referring to  FIG. 1  to  FIG. 6 , an engine  10  according to an exemplary embodiment of the present invention includes a cylinder head  10  and a continuous variable valve duration apparatus mounted to the cylinder head  10 . 
     The continuous variable valve duration apparatus includes a camshaft  30 , a first and second cam portions  70   a  and  70   b  of which a cam  71  and  72  is formed thereto respectively, of which the camshaft  30  is inserted thereto and of which relative phase angles with respect to the camshaft  30  are variable, a first and second inner brackets  80  and  81  transmitting rotation of the camshaft  30  to the first and second cam portions  70   a  and  70   b  respectively, a first and second slider housings  90   a  and  90   b  of which the first and second inner brackets  80   a  and  80   b  are rotatably inserted thereto and of which relative position with respect to the camshaft  30  are variable, a cam cap  40  rotatably supporting the first and second cam portions  70   a  and  70   b  respectively and of which each slider housing  90   a  and  90   b  is slidably mounted thereto, a control shaft  95  disposed parallel to the camshaft  30  and engaged with the first and second slider housings  90   a  and  90   b  for selectively moving the first and second slider housings  90   a  and  90   b  and a control portion  100  selectively rotating the control shaft  95  for changing positions of the inner brackets  80   a  and  80   b.    
     The engine includes a plurality of cylinders  211 ,  212 ,  213  and  214 , and the cam portions  70   a  and  70   b  are disposed corresponding to the each cylinder  211 ,  212 ,  213  and  214  respectively. 
     In the drawing, 4 cylinders are formed to the engine, but it is not limited thereto. 
     The camshaft  30  may be an intake camshaft or an exhaust camshaft. 
     In the drawing, the cam  71  and  72 , for driving valves  200 , is formed as a pair, but it is not limited thereto. 
     To the cam portions  70   a  and  70   b , a cam cap connecting portion  76  for engaged with the cam cap  40  is formed between the first and the second cams  71  and  72 . The cylinder head  10  and the cam cap  40  are connected with each other and the cam cap connecting portion  76  is rotatably disposed between the cam cap  40  and the cylinder head  10 . 
     The cam  71  and  72  rotate and open the valve  200 . 
     A cam key  74  is formed to the first and second cam portions  70   a  and  70   b  respectively and a first sliding hole  86  and a second sliding hole  88  are formed to the first and second inner brackets  80  and  81  respectively. 
     A cam key pin  82  of which a cam key slot  83  where the cam key  74  is slidably inserted therein is formed thereto and the cam key pin  82  is rotatably inserted into the each first sliding hole  86 . 
     Camshaft holes  32  are formed to the camshaft  30  and a plurality of camshaft pin  60  is inserted into the camshaft hole  32  to be connected to the camshaft  30 . And a slider pin  84  of which a camshaft pin slot  85  where the camshaft pin  60  is slidably inserted therein is formed thereto and the slider pin  84  is rotatably inserted into the each second sliding hole  88 . 
     A slider housing bearing  92  is disposed between the slider housing  90   a  and  90   b  and the inner bracket  80  and  81  respectively. Thus, rotations of the inner brackets  80  and  81  may be easily performed. In the drawings, the slider housing bearing  92  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. 
     A shaft hole  42  where the control shaft  95  is inserted into is formed to the cam cap  40  and a shaft bearing  44  is inserted into the shaft hole  42  and rotatably supporting the control shaft  30 . 
     A guide slot  46  is formed to the cam cap  40  and a guide shaft  93  inserted into the guide slot  46  and of which a rack gear  94  is formed thereto is protruded from the slider housings  90   a  and  90   b.    
     A pinion gear  96  is formed to the control shaft  95  and engaged with the rack gear  94  and the positions of the slider housings  90   a  and  90   b  are changed according to rotation of the control shaft  95 . 
     A bushing  48  is inserted into the guide slot  46  for reducing frictional force of the movement of the guide shaft  30 . 
     A stopper  50  is disposed to the cam cap  40  for limiting the movement of the slider housings  90   a  and  90   b.    
     The control portion  100  includes a worm wheel  102  connected to the control shaft  95 , a worm gear  104  engaged with the worm wheel  102  and a control motor  106  selectively rotating the worm gear  104 . 
     The first inner bracket  80  disposed within the first slider housing  90   a  may include two inner bracket elements  80   a  and  80   b  and each inner bracket element  80   a  and  80   b  may rotate independently. 
     The second inner bracket  81  disposed within the second slider housing  90   b  may include two inner bracket elements  81   a  and  81   b  and each inner bracket element  81   a  and  81   b  may rotate independently. 
     A partition  91  is disposed within the first and second slider housings  90   a  and  90   b  respectively for preventing from interrupting of the rotations of the inner brackets  80  and  81 . 
     Thus, interrupting of the rotations of inner bracket element  80   a ,  80   b ,  81   a  and  81   b  may be prevented. 
     A guide surface  98  is formed to the first and second slider housings  90   a  and  90   b  and a guider  12  is formed to the cylinder head  10  for contacting the guide surface  98  and guiding movements of the first and second slider housings  90   a  and  90   b.    
     As shown in  FIG. 5 , for example, an engine with a first, second, third and fourth cylinders  211 ,  212 ,  213  and  214  may be provided with two first and second cam portions  70   a  and  70   b , two inner brackets  80  and  81 , two slider housings  90   a  and  90   b  and one control motor  106  and perform changing duration of each cam  71  and  72 . Thus, the continuously variable valve duration apparatus according to an exemplary embodiment of the present invention may reduce numbers of elements, thus durability may be improved and operation stability may be obtained. 
       FIG. 7  and  FIG. 8  are drawings showing mechanical motions of cams of a continuous variable valve duration apparatus according to an exemplary embodiment of the present invention. 
     As shown in  FIG. 1  to  FIG. 6 , according to engine operation states, an ECU (engine control unit or electric control unit) transmits control signals to the control motor  106  of the control portion  100  to change the relative position of the first and second slider housings  900  and  90   b  upward or downward. 
     When the slider housings  90   a  and  90   b  and the inner brackets  80  and  81  moves according to operation of the control motor  106 , rotation centers of the inner brackets  80  and  81  with respect to the camshaft  30  are changed. 
     As shown in  FIG. 7 , while the phase angle of the camshaft  30  is constantly changed when the relative rotation center of the cams  71  and  72  with respect to the rotation center of the camshaft  30  is changed downward, the rotation speed of the cams  71  and  72  is relatively faster than rotation speed of the camshaft  30  from phase a to phase b and from phase b to phase c, then the rotation speed of the cams  71  and  72  is relatively slower than rotation speed of the camshaft  30  from phase c to phase d and from phase d to phase a. That is, the valve duration is changed. 
     As shown in  FIG. 8 , while the phase angle of the camshaft  30  is constantly changed when the relative rotation center of the cams  71  and  72  with respect to the rotation center of the camshaft  30  is changed upward, the rotation speed of the cams  71  and  72  is relatively slower than rotation speed of the camshaft  30  from phase a to phase b and from phase b to phase c, then the rotation speed of the cams  71  and  72  is relatively faster than rotation speed of the camshaft  30  from phase c to phase d and from phase d to phase a. That is, the valve duration is changed. 
     While the camshaft pin  60  is rotated together with the camshaft  30 , the camshaft pin  60  is slidable within the camshaft pin slot  85 , the slider pin  84  is rotatably inserted into the second sliding hole  88 , the cam key pin  82  is rotatably inserted into the first sliding hole  82 , and the cam key  74  is slidable within the cam key slot  83 . Thus the relative rotation speed of the cams  71  and  72  with respect to the rotation speed of the camshaft  30  is changed. 
       FIG. 9  and  FIG. 10  are graphs of a valve profile of a continuous variable valve duration apparatus according to an exemplary embodiment of the present invention. 
     As shown in  FIG. 9  and  FIG. 10 , although maximum lift of the valve  200  is constant, however rotation speed of the cam  71  and  72  with respect to the rotation speed of the camshaft  30  is changed according to relative positions of the slider housings  90   a  and  90   b  so that closing and opening time of the valve  200  is changed. That is, duration of the valve  200  is changed. 
     According to adjusting mounting angle of the valve  200 , forming the guide surface  98  and the guider  12  and so on, valve duration may be enlarged by advancing opening timing and retarding closing timing of the valve  200  as shown in  FIG. 9 . Or, valve duration may be shortened by retarding opening timing and advancing closing timing of the valve  200 . 
     Also, as shown in  FIG. 10 , opening timing of the valve  200  may be constant and closing timing of the valve  200  may be retarded or advanced as requested. 
     Also, closing timing of the valve  200  may be constant and opening timing of the valve  200  may be retarded or advanced as requested. 
     As described above, the continuous variable valve duration apparatus according to an exemplary embodiment of the present invention may perform various valve duration according to adjusting mounting angle of the valve  200 , forming the guide surface  98  and the guider  12  and so on. 
     The continuous variable valve duration 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 duration 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”, “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.