Abstract:
An engine of a variable stroke type may include a camshaft that a first cam and a second cam which may be adjacent to each other may be formed on the camshaft, a valve that may be disposed to be moved by the first cam or the second cam, and a tappet that may be engaged to the valve and disposed between the first and second cam and the valve to make the first cam move the valve or to make the second cam move the valve, wherein the second cam has a rotational phase difference with the first cam in a rotating direction of the camshaft.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to Korean Patent Application No. 10-2013-0122237 filed on Oct. 14, 2013, the entire contents of which is incorporated herein for all purposes by this reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention is related to an engine of a variable stroke type that varies a cylinder from 4 to 2 stroke of a cylinder in accordance with a driving condition in such a way that fuel consumption is reduced and output is increased. 
         [0004]    2. Description of Related Art 
         [0005]    Generally, many arts have been introduced so as to enhance engine performance and reduce fuel consumption. One of them is a cylinder deactivation (CDA) art that operates all cylinders in a high load condition and deactivates a cylinder in a low load condition. 
         [0006]    Further, there is an art that varies an opening timing, a closing timing, a opening duration time, and a closing duration time of an intake valve and an exhaust valve that opens an intake port and an exhaust port so as to improve engine performance and reduce fuel consumption. 
         [0007]    Meanwhile, researches for variably controlling a stroke of an engine from 4 to 2 stroke has been being performed so as to increase performance in a high load condition and reduce fuel consumption in a low load condition for a middle size vehicle and a large size vehicle. 
         [0008]    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 
       [0009]    Various aspects of the present invention are directed to providing an engine of a variable stroke type that variably controls a stroke of an engine having advantages of reducing fuel consumption in a low load condition and simultaneously increasing performance in a high load condition. 
         [0010]    In an aspect of the present invention, an engine of a variable stroke type, may include a camshaft that a first cam and a second cam which are adjacent to each other are formed on the camshaft, a valve that is disposed to be moved by the first cam or the second cam, and a tappet that is engaged to the valve and disposed between the first and second cam and the valve to make the first cam move the valve or to make the second cam move the valve, wherein the second cam may have a rotational phase difference with the first cam in a rotating direction of the camshaft. 
         [0011]    The number of the first cam is one in one rotational area of the camshaft, and the number of the second cam is two in one rotational area of the camshaft. 
         [0012]    Two second cams may have a phase difference of 180 degrees. 
         [0013]    The valve is an intake valve. 
         [0014]    The tappet may include an inner tappet corresponding to the first cam, an outer tappet corresponding to the second cam, a middle tappet that is disposed between the inner tappet and the outer tappet to press the valve, and a latching pin that is moved by a hydraulic pressure supplied to an end thereof to latch the middle tappet with the outer tappet or to latch the middle tappet with the inner tappet. 
         [0015]    A first lost spring that elastically biases the inner tappet toward the camshaft from the middle tappet, and a second lost spring that elastically biases the outer tappet toward the camshaft from the middle tappet. 
         [0016]    The engine of the variable stroke type may further include a latching spring that is disposed inside the middle tappet to elastically bias the latching pin toward the outer tappet in such a way that the middle tappet is selectively latched with the outer tappet. 
         [0017]    The hydraulic pressure is supplied to the end of the latching pin in such a way that the latching pin is pushed from a side of the outer tappet to a side of the middle tappet. 
         [0018]    The number of the first cam is one in one rotational area of the camshaft and the number of the second cam is one in one rotational area of the camshaft. 
         [0019]    The first cam may have a phase difference of 180 degrees with the second cam. 
         [0020]    The valve is an exhaust valve. 
         [0021]    The tappet may include an inner tappet that is disposed to push the valve corresponding to the first cam, an outer tappet corresponding to the second tappet, and a latching pin that is operated by a hydraulic pressure supplied to an end of the latching pin so as to latch the inner tappet with the outer tappet. 
         [0022]    The engine of the variable stroke type may further include a lost spring that elastically biases the outer tappet from the inner tappet toward the camshaft. 
         [0023]    The engine of the variable stroke type may further include a latching spring that is disposed inside the outer tappet elastically biases the latching pin toward the inner tappet in such a way that the inner tappet is latched with the outer tappet. 
         [0024]    A hydraulic pressure is supplied to the end of the latching pin to push the latching pin from a side of the inner tappet to a side of the outer tappet. 
         [0025]    In accordance with the present invention for realizing the object, a first intake cam is formed on an intake camshaft so as to realize 4 stroke cycle, two second intake cams having a phase difference of 180 degrees are formed so as to realize 2 stroke cycle, and an intake valve is lifted by the intake variable tappet corresponding to the first intake cam and the second intake cam in such a way that an engine variably realizes 4 stroke cycle or 2 stroke cycle depending on a driving condition. 
         [0026]    Further, a first exhaust cam is formed on an exhaust camshaft for 4 stroke cycle, a second exhaust cam is formed thereon for 2 stroke cycle, and an exhaust valve is lifted by an exhaust variable tappet corresponding to the first exhaust cam and the second exhaust cam in such a way that an engine variably realizes 4 stroke or 2 stroke. 
         [0027]    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 
         [0028]      FIG. 1  is a schematic perspective view of a valve lift device that is disposed on a normal cylinder of an engine of a variable stroke type according to an exemplary embodiment of the present invention. 
           [0029]      FIG. 2  is a schematic perspective view of a valve lift device that is disposed on a variable cylinder of an engine of a variable stroke type according to an exemplary embodiment of the present invention. 
           [0030]      FIG. 3  is a cross-sectional view of a tappet that is applied to a valve lift device of a normal cylinder of an engine of a variable stroke type according to an exemplary embodiment of the present invention. 
           [0031]      FIG. 4  is a cross-sectional view of a tappet that is applied to a valve lift device of a variable cylinder of an engine of a variable stroke type according to an exemplary embodiment of the present invention. 
           [0032]      FIG. 5  is a table showing a driving mode of an engine of a variable stroke type according to an exemplary embodiment of the present invention. 
       
    
    
       [0033]    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. 
         [0034]    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 
       [0035]    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. 
         [0036]    An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
         [0037]      FIG. 1  is a schematic perspective view of a valve lift device that is disposed on a normal cylinder of an engine of a variable stroke type according to an exemplary embodiment of the present invention. 
         [0038]    Referring to  FIG. 1 , a valve lift device includes an intake valve  100 , an intake tappet  110 , an intake camshaft  120 , an intake cam  130 , an exhaust valve  102 , an exhaust tappet  112 , an exhaust camshaft  122 , and an exhaust cam  132 . 
         [0039]    And, the intake tappet  110  and the exhaust tappet  112  don&#39;t have a lost motion function, the intake cam  130  lifts the intake valve  100  through the intake tappet  110 , and the exhaust cam  132  lifts the exhaust valve  102  through the exhaust tappet  112 . 
         [0040]      FIG. 2  is a schematic perspective view of a valve lift device that is disposed on a variable cylinder of an engine of a variable stroke type according to an exemplary embodiment of the present invention. 
         [0041]    Referring to  FIG. 2 , a valve lift device includes an intake valve  100 , an intake variable tappet  200 , an intake camshaft  120 , a first intake cam  210 , a second intake cam  220 , an exhaust valve  102 , an exhaust variable tappet  202 , an exhaust camshaft  122 , a first exhaust cam  212 , and a second exhaust cam  222 . 
         [0042]    The first intake cam  210  and the second intake cam  220  are formed on the intake camshaft  120 , and the first intake cam  210  has a phase that is different from the second intake cam  220 . 
         [0043]    More specifically, the first intake cam  210  is formed in a middle portion, the second intake cam  220  is formed at both sides of the first intake cam  210 , the second intake cam  220  is formed at both sides with a phase difference of 180 degrees, and the first intake cam  210  has a phase difference of 90 degrees from the a second intake cam  220 . 
         [0044]    And, the first intake cam  210  lifts the intake valve  100  through the intake variable tappet  200 , or the second intake cam  220  lifts the intake valve  100  through the intake variable tappet  200 . 
         [0045]    More specifically, a cylinder performs 4 stroke cycle while the intake valve  100  is operated by the first intake cam  210 , and a cylinder performs 2 stroke cycle while the intake valve  100  is operated by the second intake cam  220 . 
         [0046]    Also, the first exhaust cam  212  and the second exhaust cam  222  are formed on the exhaust camshaft  122 , and the first exhaust cam  212  and the second exhaust cam  222  have different phase. 
         [0047]    More specifically, the first exhaust cam  212  is formed at a middle portion, the second exhaust cam  222  is formed at both sides of the first exhaust cam  212 , and the first exhaust cam  212  has a phase difference of  180  degrees from the a second exhaust cam  222 . 
         [0048]    And, the first exhaust cam  212  lifts the exhaust valve  102  through the exhaust variable tappet  202  or the second exhaust cam  222  lifts the exhaust valve  102  through the exhaust variable tappet. 
         [0049]    More specifically, while the exhaust valve  102  is operated by the first exhaust cam  212 , a cylinder performs 4 stroke cycle, and when the exhaust valve  102  is operated by the second exhaust cam  222 , a cylinder performs 2 stroke cycle. 
         [0050]      FIG. 3  is a cross-sectional view of a tappet that is applied to a valve lift device of a normal cylinder of an engine of a variable stroke type according to an exemplary embodiment of the present invention. 
         [0051]    Referring to  FIG. 3 , an exhaust variable tappet  202  includes an inner tappet  300 , a latching pin  310 , a pin cap  320 , a latching spring  330 , a hydraulic chamber  340 , an outer tappet  350 , and a lost spring  360 . 
         [0052]    An inner tappet  300  is disposed on a middle portion corresponding to the first exhaust cam  212 , and an outer tappet  350  is disposed on an outer side of the inner tappet  300  corresponding to the second exhaust cam  222 . 
         [0053]    The inner tappet  300  is disposed to press the exhaust valve  102 , a latching pin  310  and a latching spring  330  are disposed in a hydraulic chamber  340  that is formed inside the outer tappet  350 , and the hydraulic chamber  340  is sealed by the pin cap  320 . 
         [0054]    Here, the latching spring  330  elastically supports the latching pin  310  in such a way that the outer tappet  350  is latched with the inner tappet  300 . Meanwhile, in a case in which hydraulic pressure is supplied to the hydraulic chamber  340 , the latching pin  310  compresses the latching spring  330  in such a way that the latching of the inner tappet  300  and the outer tappet  360  is released. 
         [0055]    If the latching of the inner tappet  300  and the outer tappet  360  is released, the outer tappet  360  performs a lost motion through the lost spring  360 . 
         [0056]      FIG. 4  is a cross-sectional view of a tappet that is applied to a valve lift device of a variable cylinder of an engine of a variable stroke type according to an exemplary embodiment of the present invention. 
         [0057]    Referring to  FIG. 4 , an intake variable tappet  200  includes an inner tappet  410 , a middle tappet  420 , an outer tappet  430 , a latching pin  440 , a stopper  450 , a hydraulic chamber  460 , a first lost spring  470 , a second lost spring  480 , and a latching spring  400 . 
         [0058]    A latching spring  400  is disposed inside the inner tappet  410 , and the latching pin  440  is disposed at both sides of the latching spring  400 . If the hydraulic pressure is not supplied, the latching pin  440  is moved backward to latch the outer tappet  430  with the middle tappet  420 , and if the hydraulic pressure is supplied, the latching pin  440  is moved forward to latch the middle tappet  420  with the inner tappet  410 . 
         [0059]    In a condition in which hydraulic pressure is not supplied, the stopper  450  prevents the backward movement of the latching pin  440  in such a way the latching condition of the middle tappet  420  and the outer tappet  430  is maintained. 
         [0060]    As shown, a central portion of the middle tappet  420  is opened upward, the first lost spring  470  is disposed therein, and the first lost spring  470  elastically supports the inner tappet  410  upward. 
         [0061]    In a condition in which the latching pin  440  latches the middle tappet  420  with the outer tappet  430 , the inner tappet  410  performs a lost motion through the first lost spring  470 . And, in a condition in which the latching pin  440  latches the inner tappet  410  with the middle tappet  420 , the outer tappet  430  performs a lost motion through the second lost spring  480 . 
         [0062]      FIG. 5  is a table showing a driving mode of an engine of a variable stroke type according to an exemplary embodiment of the present invention. 
         [0063]    Referring to  FIG. 5 , an engine includes 4 stroke normal cylinder and variable stroke cylinder (VSC, 2 stroke &lt;-&gt;4 stroke). 
         [0064]    And, in a first mode, hydraulic pressure is supplied to the intake variable tappet  200  and the exhaust variable tappet  202  that are mounted in the variable stroke cylinder, and in a second mode, hydraulic pressure is not supplied to the intake variable tappet  200  and the exhaust variable tappet  202  that are mounted on the variable stroke cylinder. 
         [0065]    Accordingly, in the first mode, the latching pin  440  of an intake variable tappet  200  of the variable stroke cylinder latches the inner tappet  410  and the middle tappet  420  through the hydraulic pressure and the outer tappet  430  performs a lost motion by a second intake cam  220 . And, the inner tappet  410  and the middle tappet  420  operate the intake valve  100  through the first intake cam  210 . 
         [0066]    In the first mode, the latching pin  440  of the exhaust variable tappet  202  of the variable stroke cylinder release the latching condition of the inner tappet  300  and the outer tappet  350  through hydraulic pressure, and the outer tappet  350  performs a lost motion through a second exhaust cam  222 . And, the first exhaust cam  212  performs the exhaust valve  102  through the inner tappet  300 . 
         [0067]    Further, in the second mode, the latching pin  440  of the intake variable tappet  200  of the variable stroke cylinder latches the middle tappet  420  with the outer tappet  430  through hydraulic pressure not supplied, and the inner tappet  410  performs a lost motion through a first intake cam  210 . And, the second intake cam  220  operates the intake valve  100  through the outer tappet  430  and the middle tappet  420 . 
         [0068]    In the second mode, the latching pin  330  of the exhaust variable tappet  202  of the variable stroke cylinder latches the inner tappet  300  and the outer tappet  350  through hydraulic pressure not supplied. And, the exhaust valve  102  is operated by the first exhaust cam  212  and the second exhaust cam  222 . 
         [0069]    As described above, a first intake cam  210  is formed on an intake camshaft  120  so as to realize 4 stroke cycle, two second intake cams  220  having a phase difference of 180 degrees are formed so as to realize 2 stroke cycle, and an intake valve  100  is lifted by the intake variable tappet  200  corresponding to the first intake cam  210  and the second intake cam  220  in such a way that an engine variably realizes 4 stroke cycle or 2 stroke cycle depending on a driving condition. 
         [0070]    Also, a first exhaust cam  212  is formed on an exhaust camshaft  122  for 4 stroke cycle, a second exhaust cam  222  is formed thereon for 2 stroke cycle, and an exhaust valve  102  is lifted by an exhaust variable tappet  202  corresponding to the first exhaust cam  212  and the second exhaust cam  222  in such a way that an engine variably realizes 4 stroke or 2 stroke. 
         [0071]    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. 
         [0072]    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. 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 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.