Abstract:
A control method using a continuous variable valve duration apparatus may use a continuous variable valve duration apparatus including a wheel being mounted on a camshaft and having a wheel key to control duration of an intake valve of an engine, a cam device having a cam and a cam key, being adapted that the camshaft is inserted thereinto, and being disposed to can vary relative phase of the cam with respect to the camshaft, an inner bracket being connected with the wheel key and the cam key, a slider housing being adapted that the inner bracket is rotatably inserted thereinto and being disposed to can move vertically with respect to the engine, a controller varying a position of the slider housing to adjust rotation center of the inner bracket, and guide device guiding motion of the sliding housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to and the benefit of Korean Patent Application No. 10-2015-0096817 filed on Jul. 7, 2015, the entire contents of which is incorporated herein for all purposes by this reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    Field of the Invention 
         [0003]    The present invention relates to a control method using a continuous variable valve duration apparatus. More particularly, the present invention relates to a control method using a continuous variable valve duration apparatus which can change opening duration of a valve with a simple configuration in accordance with operational states of an engine. 
         [0004]    Description of Related Art 
         [0005]    Generally, internal combustion engines generate power by receiving and burning air and fuel in a combustion chamber. An intake valve is operated by a camshaft, and air is charged into the combustion chamber while the intake valve is open. An exhaust valve is also operated by the camshaft, and air is discharged from the combustion chamber while the exhaust valve is open. 
         [0006]    Optimal operation of the intake valve/exhaust valve, however, depends on the RPM of the engine. That is, an appropriate time for lifting or opening/closing the valves depends on the RPM of the engine. In order to implement an appropriate valve operation in accordance with the RPM of the engine, as described above, a CVVL (Continuously Variable Valve Lift) apparatus that has a plurality of shapes of cams operating valves or operates valves at different lifts in accordance with the RPM of an engine has been studied. 
         [0007]    A CVVT (Continuous Variable Valve Timing) technique has been developed to adjust the opening duration of a valve, in which the timing of opening/closing a valve are simultaneously changed with the valve duration being fixed. 
         [0008]    However, the CVVL or the CVVT has a problem in that the configuration is complicated and the manufacturing cost is high. Meanwhile, there is a limit in preventing knocking of an engine using the CVVT. 
         [0009]    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 
       [0010]    Various aspects of the present invention are directed to providing a control method using a continuous variable valve duration apparatus having advantages of being able to adjust duration of a valve lift in accordance with the operational states of an engine. 
         [0011]    A control method using a continuous variable valve duration apparatus according to an exemplary embodiment of the present invention may use a continuous variable valve duration apparatus which includes a wheel being mounted on a camshaft and having a wheel key so as to control duration of an intake valve of an engine, a cam device having a cam and a cam key, being adapted that the camshaft is inserted thereinto, and being disposed so as to can vary relative phase of the cam with respect to the camshaft, an inner bracket being connected with the wheel key and the cam key, a slider housing being adapted that the inner bracket is rotatably inserted thereinto and being disposed so as to can move vertically with respect to the engine, a controller varying a position of the slider housing so as to adjust rotation center of the inner bracket, and guide device guiding motion of the sliding housing. The control method may include: calculating and learning a target effective compression ratio of the engine to prevent knocking by the controller when knocking of engine is occurred; mapping an effective compression ratio of the engine in accordance with duration of the intake valve by the controller; setting a target valve duration for realizing the target effective compression ratio by the controller; and controlling duration of the intake valve according to the set target valve duration by the controller. 
         [0012]    The setting of the target valve duration may be performed on the basis of a map about relation between duration of the intake valve and an effective compression ratio of the engine. 
         [0013]    The learning of the target effective compression ratio may be performed through experiments and the value of the learned target effective compression ratio may be stored to the controller. 
         [0014]    The mapping of relation between the duration of the intake valve and the effective compression ratio of the engine may be performed through experiments and the mapped map about relation between the duration of the valve and the effective compression ratio of the engine may be stored to the controller. 
         [0015]    The control method may be ended when the engine enters a normal operation state where knocking is not expected. 
         [0016]    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 
         [0017]      FIG. 1  is a perspective view an engine equipped with a continuous variable valve duration apparatus according to an exemplary embodiment of the present invention. 
           [0018]      FIG. 2  is an exploded perspective view of the continuous variable valve duration apparatus according to an exemplary embodiment of the present invention. 
           [0019]      FIG. 3  and  FIG. 4  are partial exploded perspective views of the continuous variable valve duration apparatus according to an exemplary embodiment of the present invention. 
           [0020]      FIG. 5  is a view illustrating the operation of the continuous variable valve duration apparatus according to an exemplary embodiment of the present invention. 
           [0021]      FIG. 6  is a graph showing a valve profile of the continuous variable valve duration apparatus according to an exemplary embodiment of the present invention. 
           [0022]      FIG. 7  is a flowchart illustrating a control method using the continuous variable valve duration apparatus according to an exemplary embodiment of the present invention. 
       
    
    
       [0023]    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. 
         [0024]    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 
       [0025]    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. 
         [0026]    In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. 
         [0027]    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 
         [0028]    Like reference numerals are given to like components throughout the specification. 
         [0029]    Throughout the specification, 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 
         [0030]    An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
         [0031]      FIG. 1  is a perspective view an engine equipped with a continuous variable valve duration apparatus according to an exemplary embodiment of the present invention,  FIG. 2  is an exploded perspective view of the continuous variable valve duration apparatus according to an exemplary embodiment of the present invention, and  FIG. 3  and  FIG. 4  are partial exploded perspective views of the continuous variable valve duration apparatus according to an exemplary embodiment of the present invention. 
         [0032]    Referring to  FIG. 1  to  FIG. 4 , an engine according to an exemplary embodiment of the present invention includes an engine block  1 , a cylinder head  10  mounted on the engine block  1 , and a continuous variable valve duration apparatus that is mounted on the cylinder head  10 . 
         [0033]    Referring to  FIG. 1  to  FIG. 4 , according to an exemplary embodiment of the present invention, the continuous variable valve duration apparatus includes: a camshaft  30 , a plurality of wheels  60  mounted on the camshaft  30 , each having a wheel key  62 , and corresponding to cylinders, respectively, a plurality of cam devices  70  having cams  71  and  72  and a cam key  74 , in which the camshaft  30  is inserted, that have variable relative phases of the cams  71  and  72  with respect to the camshaft  30 , and correspond to the cylinders, respectively, a plurality of inner brackets  80  that are connected to the wheel keys  62  and the cam keys  74 , a plurality of slider housings  90  in which the inner brackets  80  are rotatably inserted and that can move vertically with respect to the engine, a controller  100  that adjusts the positions of the rotational centers of the inner brackets  80  by changing the positions of the slider housings  90 , and a guide device  110  that guides the slider housings  90 , according to an exemplary embodiment of the present invention includes an engine block  1 , a cylinder head  10  mounted on the engine block  1 , and a continuous variable valve duration apparatus that is mounted on the cylinder head  10 . 
         [0034]    The camshaft  30  may be an intake camshaft or an exhaust camshaft. 
         [0035]    Although two cams  71  and  72  are provided in the drawings, the present invention is not limited thereto. 
         [0036]    The cams  71  and  72  open/close a valve  200 . 
         [0037]    Fastening holes  33  are formed at the camshaft  30 , and the wheels  60  can be combined with the camshaft  30  by connecting pins  64 . Coupling springs  66  are mounted on the wheels  60 , so they can prevent separation of the connecting pins  64 . 
         [0038]    The continuous variable valve duration apparatus further includes first pins  82  having a sliding key slot  81  in which the wheel key  62  is slidably inserted and second pins  84  having a sliding key slot  83  in which the cam key  74  is slidably inserted, and the inner bracket  80  has first and second pin holes  86  and  88  in which the first pin  82  and the second pin  84  are inserted, respectively. 
         [0039]    The first and second pins  82  and  84  have the shape of a cylinder and are rotatably inserted in the first and second pin holes  86  and  88 . 
         [0040]    Accordingly, since the first and second pins  82  and  84  and the first and second sliding pin holes  86  and  88  are formed in the shape of a cylinder, abrasion resistance can be improved. 
         [0041]    Further, productivity can be secured by the simple shape of the first and second pins  82  and  84  and the first and second sliding pin holes  86  and  88 . 
         [0042]    The sliding key slots  81  and  83  of the first and second pins  82  and  84  are formed in opposite directions, and the wheel key  62  and the cam key  74  can be inserted therein. 
         [0043]    The first and second pin holes  86  and  88  may be partially open in order to not interfere with movement of the wheel key  62  and the cam key  72 . 
         [0044]    A needle bearing  92  may be disposed between the slider housing  90  and the inner bracket  80 , so the slider housing  90  and the inner bracket  80  can easily rotate relative to each other and rigidity can be secured. 
         [0045]    Control teeth  94  is formed on a side of each of the slider housings  90 , and the controller  100  includes a control shaft  102  that is parallel with the camshaft  30  and has control gears  104  engaged with the control teeth  94 , and a motor  108  that selectively rotates the control shaft  102 . 
         [0046]    The guide device  110  includes a guide bar  112  guiding the slider housings  90  and guide brackets  114  fixing the guide bar  112 , and a guide slot  96  in which the guide bar  112  is inserted is formed in the slider housings  90 . 
         [0047]      FIG. 5  is a view illustrating the operation of the continuous variable valve duration apparatus according to an exemplary embodiment of the present invention, and  FIG. 6  is a graph showing a valve profile of the continuous variable valve duration apparatus according to an exemplary embodiment of the present invention. 
         [0048]    Hereinafter, the operation of the continuous variable valve duration apparatus according to an exemplary embodiment of the present invention is described with reference to  FIG. 1  to  FIG. 6 . 
         [0049]    In accordance with the operational states of an engine, the motor  108  of the controller  100  operates and changes the relative positions of the slider housings  90 . 
         [0050]    The first and second pin holes  86  and  88  For example, in (a) of  FIG. 5 , as the motor  108  operates, the control shaft  102  rotates, so when the position of the slider housing  90  changes upward, the rotational center of the inner bracket  80  moves by ΔH 1 , as in (b) of  FIG. 5 , or when the position of the slider housing  90  changes downward, the rotational center of the inner bracket  80  moves by ΔH 2 , as in (c) of  FIG. 5  may be partially open in order to not interfere with movement of the wheel key  62  and the cam key  72 . 
         [0051]    As the position of the rotational center of the inner bracket  80  changes, the rotational acceleration of the cam device  70  changes and valve duration changes accordingly. 
         [0052]    As shown in  FIG. 6 , the maximum lift of the valve  200  is constant, and as the position of the slider housing  90  changes, the relative rotational speed of the cams  71  and  72  to the camshaft  30  changes, the timing for opening/closing the valve  200  change, and accordingly, the duration of the valve  200  changes. In order to control an effective compression ratio of an engine, it may be possible to adjust duration to change the timing of closing an intake valve while maintaining an MBT (Minimum spark advance for Best Torque) where the maximum torque is obtained. The duration is controlled by the motor  108 , and accordingly, responsiveness can be secured. 
         [0053]      FIG. 7  is a flowchart illustrating a control method using the continuous variable valve duration apparatus according to an exemplary embodiment of the present invention. 
         [0054]    As illustrated in  FIG. 7 , a control method using the continuous variable valve duration apparatus according to an exemplary embodiment of the present invention is a method for preventing knocking of an engine by controlling an effective compression ratio of the engine. 
         [0055]    When knocking of an engine is occurred at a step S  100 , an electronic control unit (ECU) calculates and learns a target effective compression ratio to can prevent knocking of the engine at a step S 110 . Herein, the ECU may be a controller  100  as a common system mounted on vehicles to generally control electronic devices in the vehicles and is well known to those skilled in the art, so the detailed description is not provided. 
         [0056]    Meanwhile, the learning of the target effective compression ratio is performed through experiments by a person of an ordinary skill in the art before a vehicle is manufactured, and a value of the learned target effective compression ratio may be stored to the controller  100 . 
         [0057]    If the target effective compression ratio, which is required for preventing knocking according to states of the engine, is calculated at the step S 110 , the controller  100  maps an effective compression ratio in accordance with a valve duration at a step S 120 . In addition, the controller  100  sets a target valve duration for realizing the learned target effective compression ratio according to the mapped relation between the valve duration and the effective compression ratio at a step S 130 . 
         [0058]    Meanwhile, the mapping of relation between the duration of the valve  200  and the effective compression ratio is performed through experiments by a person of an ordinary skill in the art before a vehicle is manufactured, and the mapped map about relation between the duration of the valve  200  and the effective compression ratio may be stored to the controller  100 . 
         [0059]    If the target valve duration is set at the step S 130 , the controller  100  controls duration of the valve  200  according to the set target valve duration at a step S 140 . At this time, the controlling of the valve  200  duration is performed as the controller  100  controls the motor  108 . Herein, the valve  200 , that the duration is controlled, may be an intake valve. In addition, the engine is driven without knocking though states of the engine is rapidly changed as the valve  200  duration is controlled. Furthermore, when the engine enters a normal operation state where knocking is not expected, a control method using a continuous variable valve duration apparatus according to an exemplary embodiment of the present invention is ended at a step S 150 . Meanwhile, the controller  100  determines the normal operation state of the engine by receiving information about an operation state of the engine. 
         [0060]    According to a control method using a continuous variable valve duration apparatus according to an exemplary embodiment of the present invention, an effective compression ratio of an engine can be controlled as duration of a valve lift is controlled by using a continuous variable valve duration apparatus which can adjust duration of the valve lift with a simple configuration in accordance with operational states of an engine. 
         [0061]    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. 
         [0062]    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.