Abstract:
A variable compression ratio device that includes a piston, a piston pin, and a connecting rod of which one end is connected to the piston by the piston pin, may include an eccentric ring rotatably coupled in a ring at the one end of the connecting rod, wherein the inner circumference thereof rotatably contacts with the outer circumference of the piston pin, an operating pin that longitudinally reciprocates in the piston pin, variable sliders that selectively contact one of both ends of the operating pin under a cylinder to push the one of both ends to the opposite side, and a guide plate that slidably supports the variable sliders, wherein, one end of a variable shaft selectively rotating is connected to the variable slider and a sliding direction of the variable slider is controlled by the rotation of the variable shaft.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to Korean Patent Application No. 10-2009-0118735 filed in the Korean Intellectual Property Office on Dec. 2, 2009, 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 relates to a variable compression ratio device. More particularly, the present invention relates to variable compression ratio device that varies the compression ratio of gas mixture in a combustion chamber in accordance with the driving conditions. 
         [0004]    2. Description of Related Art 
         [0005]    In general, thermal efficiency of a heat engine increases with the increase of a compression ratio, while thermal efficiency of a spark ignition engine increases when ignition timing is advanced to a predetermined level. However, the spark ignition engine makes abnormal combustion when the ignition timing is advanced at a high compression ratio and the engine may be damaged, such that the advanced angle of ignition timing is limited and the output may be reduced. 
         [0006]    A variable compression ratio device is a device that varies the compression ratio of gas mixture, in accordance with operation conditions. With the variable compression ratio device, it is possible to improve fuel efficiency by increasing the compression ratio of gas mixture under a low-load condition of an engine, and prevent knocking and improve engine output by reducing the compression ratio of gas mixture under a high-load condition of the engine. 
         [0007]    In order to achieve the variable compression ratio, there has been known a method of forming an oil chamber inside an eccentric ring disposed in a small end of a connecting rod and eccentrically rotating the eccentric ring by using hydraulic pressure generated by supplying oil into the oil chamber; however, in a variable compression ratio device according to the related art, it is required to increase pressure to maintain the position of the eccentric ring in the oil chamber when explosion pressure is applied, because the distance from the eccentric ring to the center of the oil chamber, such that the compression ratio is not maintained. 
         [0008]    Further, it may be required to considerably increase oil pressure for varying the compression ratio. 
         [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 OF THE INVENTION 
       [0010]    Various aspects of the present invention are directed to provide a variable compression ratio device having advantages of having an improved structure to vary the compression ratio inside a cylinder. 
         [0011]    In an aspect of the present invention, the variable compression ratio device that includes a piston, a piston pin mounted to the piston, a crankshaft, and a connecting rod of which one end is connected to the piston by the piston pin and of which the other end is rotatably coupled to the crankshaft, may include an eccentric ring rotatably coupled in a ring at the one end of the connecting rod, wherein the inner circumference thereof rotatably contacts with the outer circumference of the piston pin and the center of the inner circumference thereof is biased from the center of the outer circumference thereof, an operating pin that longitudinally reciprocates in the piston pin, variable sliders that selectively contact one of both ends of the operating pin under a cylinder to push the one of both ends to the opposite side, and a guide plate that slidably supports the variable sliders such that the variable sliders vertically reciprocate with respect to the movement direction of the operating pin, wherein, one end of a variable shaft selectively rotating is connected to the variable slider and a sliding direction of the variable slider is controlled by the rotation of the variable shaft. 
         [0012]    A mounting groove may be formed on the outer circumference of the eccentric ring and oil holes are formed at both lateral ends of the mounting groove in a circumferential direction. 
         [0013]    A mounting protrusion may be couple to the mounting groove and forms oil chambers in the one end of the connecting rod in a forward and rearward direction of the mounting protrusion wherein the oil chambers are covered by a mounting cover to seal the mounting protrusion. 
         [0014]    An oil supply channel may be formed in the connecting rod to supply oil to the oil holes, wherein an oil inlet hole is formed in the eccentric ring to receive oil from the oil supply channel of the oil connecting rod. 
         [0015]    The piston pin may include an oil input hole to fluid-communicate with the oil inlet hole of the eccentric ring to receive the oil from the oil supply channel of the connecting rod and includes oil supply holes, wherein a control channel is formed in the operating pin and fluid-communicates with the oil inlet hole of the piston pin and selectively fluid-communicates with the one of the oil supply holes of the piston pin to supply the oil to one of the oil chambers in accordance with longitudinal movement of the operating pin, and wherein the operating pin further includes oil discharge channels formed in a longitudinal direction at both end portions thereof, and wherein the oil disposed in the other of the chambers are discharged through the oil supply hole not engaged with the control channel by fluid-connecting one of the oil discharge channel in the operating pin. 
         [0016]    The ring of the connecting rod may include circulation grooves formed along the inner circumference of the ring and wherein the circulation grooves are connected to the oil holes of the eccentric ring. 
         [0017]    A protrusion may be formed on the inner surface of the variable sliders to correspond to both ends of the operating pin, and disposed not to correspond to each other in the same moving direction. 
         [0018]    The variable shaft and the variable sliders may be connected by operating arms, wherein shaft rings are formed on the outer circumference of the variable shaft to integrally rotate, the variable shaft and the operating arms are connected by first hinge portions formed at the shaft rings, the operating arms are connected with the variable sliders by second hinge portions, and as the variable shaft selectively rotates in one direction, the operating arms allow the variable sliders to reciprocate straight through the first hinge portions and the second hinge portions. 
         [0019]    A guide rail may be formed on one side of the guide plate to guide the variable sliders to reciprocate forward and rearward and a fixing block is formed under the guide rail to fix the guide plate. 
         [0020]    The variable shaft may be driven by a vacuum actuator individually provided. 
         [0021]    According to a variable compression ratio device having the above configuration of the present invention, it is possible to reduce the number of parts and simplify the configuration, because it does not use oil pressure or an electric motor to rotate an eccentric ring. 
         [0022]    Further, since the distance from the center of the eccentric ring to the oil chambers is large, it is possible to achieve large torque even from small force. 
         [0023]    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 of the Invention, which together serve to explain certain principles of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1  is a perspective view of an exemplary variable compression ratio device according to the present invention. 
           [0025]      FIG. 2  is an exploded perspective view of an exemplary variable compression ratio device according to the present invention. 
           [0026]      FIG. 3  is an exploded perspective view showing the driving part of an exemplary variable compression ratio device according to the present invention. 
           [0027]      FIG. 4  is a perspective view showing a slider of an exemplary variable compression ratio device according to the present invention. 
           [0028]      FIG. 5  is a perspective view showing a piston pin of an exemplary variable compression ratio device according to the present invention. 
           [0029]      FIG. 6  is an exploded perspective view of  FIG. 5 . 
           [0030]      FIG. 7  is a view showing the operation of a piston pin of an exemplary variable compression ratio device according to the present invention. 
           [0031]      FIG. 8  is a cross-sectional view showing when an exemplary variable compression ratio device according to the present invention is applied to the small end of a connecting rode. 
           [0032]      FIG. 9  is a perspective view showing the structure of  FIG. 8 . 
           [0033]      FIG. 10  is an exploded perspective view of  FIG. 9 . 
           [0034]      FIG. 11  is a perspective view schematically showing the inside of an eccentric ring that is applied to an exemplary variable compression ratio device according to the present invention. 
           [0035]      FIG. 12  is a view showing the operation of a variable shaft according to a compression ratio of an exemplary variable compression ratio device of the present invention. 
           [0036]      FIG. 13  is a view showing the operation of a variable slide according to a compression ratio of an exemplary variable compression ratio device of the present invention. 
           [0037]      FIG. 14  is a view showing the inside of a connecting rod that operates in accordance with a compression ratio of an exemplary variable compression ratio device according to the present invention. 
           [0038]      FIG. 15  is a view showing changes in height according to the compression ratio of a piston applied to an exemplary variable compression ratio device according to the present invention. 
       
    
    
       [0039]    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. 
         [0040]    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 OF THE INVENTION 
       [0041]    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 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. 
         [0042]    An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
         [0043]      FIG. 1  is a perspective view of a variable compression ratio device according to an exemplary embodiment of the present invention. 
         [0044]      FIG. 2  is an exploded perspective view of a variable compression ratio device according to an exemplary embodiment of the present invention. 
         [0045]      FIG. 3  is an exploded perspective view showing the driving part of a variable compression ratio device according to an exemplary embodiment of the present invention. 
         [0046]      FIG. 4  is a perspective view showing a slider of a variable compression ratio device according to an exemplary embodiment of the present invention. 
         [0047]      FIG. 5  is a perspective view showing a piston pin of a variable compression ratio device according to an exemplary embodiment of the present invention. 
         [0048]      FIG. 6  is an exploded perspective view of  FIG. 5 . 
         [0049]      FIG. 7  is a view showing the operation of a piston pin of a variable compression ratio device according to an exemplary embodiment of the present invention. 
         [0050]      FIG. 8  is a cross-sectional view showing when a variable compression ratio device according to an exemplary embodiment of the present invention is applied to the small end of a connecting rod. 
         [0051]      FIG. 9  is a perspective view showing the structure of  FIG. 8 . 
         [0052]      FIG. 10  is an exploded perspective view of  FIG. 9 . 
         [0053]      FIG. 11  is a perspective view schematically showing the inside of an eccentric ring that is applied to a variable compression ratio device according to an exemplary embodiment of the present invention. 
         [0054]      FIG. 12  is a view showing the operation of a variable shaft according to a compression ratio of a variable compression ratio device of an exemplary embodiment of the present invention. 
         [0055]      FIG. 13  is a view showing the operation of a variable slide according to a compression ratio of a variable compression ratio device of an exemplary embodiment of the present invention. 
         [0056]      FIG. 14  is a view showing the inside of a connecting rod that operates in accordance with a compression ratio of a variable compression ratio device according to an exemplary embodiment of the present invention. 
         [0057]      FIG. 15  is a view showing changes in height according to the compression ratio of a piston applied to a variable compression ratio device according to an exemplary embodiment of the present invention. 
         [0058]    Referring to  FIG. 1  and  FIG. 2 , a variable compression ratio device according to an exemplary embodiment of the present invention includes a variable shaft  100 , a piston  200 , a connecting rod  300  having a control channel  425  therein, an eccentric ring  400 , a piston pin  410 , an operating pin  420 , operating arms  500 , and variable sliders  510 . 
         [0059]    The variable shaft  100  is selectively rotated in one direction by an actuator  600  individually provided outside a cylinder block. 
         [0060]    The actuator  600  may be any one as long as it can drive the variable shaft  100 , such as a vacuum actuator. 
         [0061]    In this configuration, the piston  200  mounted in the cylinder block reciprocates along the inner wall of the cylinder  150  such that a crankshaft  10  disposed thereunder rotates, and is connected to the upper end (hereafter, referred to as a small end) of the connecting rod  300 . 
         [0062]    Further, the eccentric ring  400  is disposed to rotate in contact with the inner circumference of a ring  320  in the small end  310 . 
         [0063]    Further, the piston pin  410  is inserted in the eccentric ring  400 . 
         [0064]    That is, the inner circumference of the eccentric ring  400  is in contact with outer circumference of the piston pin  410  and the outer circumference of the eccentric ring  400  is in contact with the inner circumference of the small end  310 . 
         [0065]    The eccentric ring  400  for changing the compression ratio of the engine is disposed coaxially with the piston pin  410  and the outer circumference of the eccentric ring  400  is biased from the center of the small end  310 . 
         [0066]    Further, as shown in  FIG. 11 , a mounting groove  401  is formed on the outer circumference of the eccentric ring  400 . 
         [0067]    Although, in the present exemplary embodiment, the shape of the mounting groove  401  is a quadrangle with rounded edges, any shape is possible as long as it can firmly retain the mounting protrusion  406 , which is described later. 
         [0068]    The mounting protrusion  406  protrudes outward from the mounting groove  401  at a predetermined height, when fitted in the mounting groove  401 . 
         [0069]    Further, oil holes  450  are formed on a bottom portion of the mounting groove  401  at both lateral sides of the mounting groove  401  in a circumferential direction thereof. 
         [0070]    Oil circulation grooves  404  and  405  are formed in inner circumference of the eccentric ring  400  and the oil holes  450  are fluid-connected to the oil circulation grooves  404  and  405  respectively to selectively communicate with the oil supply channel  301  of the connecting rod  300 , which is described below. 
         [0071]    In the oil circulation grooves  404  and  405 , oil is supplied through the oil circulation groove  404  and discharged through the other oil circulation groove  405 , and vice versa. 
         [0072]    Further, as shown in  FIGS. 9 and 10 , a cover  407  is provided to seal the outer side of the mounting protrusion  406 . 
         [0073]    That is, when the mounting protrusion  406  is fitted in the mounting groove  401  and the mounting protrusion  406  is firmly covered with the mounting cover  407 , a space is defined between the outer circumference of the eccentric ring  400  and the mounting cover  407  and divided into both sides by the mounting protrusion  406  to function as oil chambers  408  and  409 . 
         [0074]    With this configuration, as oil is selectively supplied through the oil holes  450 , hydraulic pressure is selectively applied in the oil chambers  408  and  409 . 
         [0075]    That is, the oil chambers  408  and  409  are separated to both sides by the mounting protrusion  406 , such that as hydraulic pressure is selectively applied to the oil chambers  408  and  409  with the mounting protrusion  406  therebetween, the mounting protrusion  406  and the eccentric ring  400  make relative motion. 
         [0076]    Further, as shown in  FIGS. 5 to 7 , an oil supply channel  301  is formed in the connecting rod  300  to supply oil to the oil chambers  408  and  409 . 
         [0077]    For this purpose, the eccentric ring  400  includes an oil inlet hole  455  formed between the oil circulation grooves  404  and  405  to the outer circumference thereof to receive the oil from the oil supply channel  301 . 
         [0078]    The piston pin  410  includes an oil input hole  470  and two oil supply holes  480 , wherein the oil input hole  470  is fluid-connected with the oil inlet hole  455  of the eccentric ring  400  and the two oil supply holes  480  are fluid-connected to the oil circulation grooves  404  and  405  of the eccentric ring  400  respectively. 
         [0079]    The operating pin  420  is mounted to reciprocate along the wall inside the piston pin  410 . 
         [0080]    For this structure, it is possible to more firmly combine the pins, by inserting the operating pin  420  into the piston pin  410 , and then using a snap ring  412  and a stopper  411  fitted to both ends of the piston pin  410 . 
         [0081]    Further, an elastic member  423  and a ball  424  may be disposed in the outer surface of the operating pin  420  to improve operability of the operating pin  420 . The ball  424  is elastically supported by the elastic member  423  and locked in a groove formed in the outer circumference of the piston pin  410  to correspond to the ball  424 , such that it is possible to stably maintain a low compression ratio or a high compression ratio while the operating pin  420  slides. 
         [0082]    In this configuration, the control channel  425  is formed in the operating pin  420 . Furthermore, the operating pin  420  includes two oil discharge channels  490  and the control channel  425  is formed between the two oil discharge channels  490 . 
         [0083]    In this configuration, as the operating pin  420  reciprocate left and right, oil supplied to the oil input hole  470  of the piston pin  41  from the oil channel  301  is selectively supplied through one of the oil supply holes  480  to one of the oil chambers  408  and  409  separated by the mounting protrusion  406 . 
         [0084]    One of two oil discharge channels  490  of the operating pin  420  is selectively connected to one of the oil supply holes  480  of the operating pin  420  such that the other of the oil chambers  408  and  409  separated by the mounting protrusion  406  is discharged through the other of the oil supply holes  480  connected to the one of the two oil discharge channels  490  in accordance with the movement direction of the operating pin  420 . 
         [0085]    Meanwhile, as shown in  FIG. 3 , the variable shaft  100  is rotated about an axis by the actuator  600  individually provided. The actuator  600  may be a vacuum actuator, as described above. 
         [0086]    In this configuration, at least two shaft rings  110  may be attached to the outer circumference of the variable shaft  100  to be fixed to the cylinder block. The shaft ring  110  may be fixed to the cylinder block by specific fasteners, such as a bolt. 
         [0087]    Further, two operating arm  500  are attached to the outer circumference of the variable shaft  100 . 
         [0088]    First hinge portions  501  are formed at ends of the operating arms  500  to be combined with the first hinge portions  501  formed at the outer circumference of the variable shaft  100 , while second hinge portions  502  are formed at the other ends and hinged to the variable sliders  510 , which are described below. 
         [0089]    The first and second hinge portions  501  and  502  connect the pair of operating arms  500  with the pair of variable sliders  510  such that they integrally rotate, when the variable shaft  100  rotates in one direction. 
         [0090]    That is, the variable shaft  100  and the operating arms  500  are hinge-connected by the first hinge portions  501  and the operating arms  500  and the variable sliders  510  are hinge-connected by the second hinge portions  502  formed at the other ends of the operating arms  500 . 
         [0091]    That is, as the variable shaft  100  is rotated in one direction by the actuator  600 , the operating arms  500  rotated by the first hinge portions  501  are reciprocated straight. 
         [0092]    Therefore, the variable sliders  510  hinged-connected to the second hinge portions  502  of the operating arms  500  also reciprocate. 
         [0093]    In this configuration, a guide plate  520  having a guide rail  525  for straight motion on the outer surface of the variable sliders  510  is provided. 
         [0094]    That is, the guide rail  525  is a straight groove and a protrusion  512  fitted in the guide rail  525  is formed on one side of the variable slider  510 . 
         [0095]    Further, a protrusion  511  is formed on the opposite sides of the variable sliders  510 . 
         [0096]    The protrusions  511  are disposed to correspond to both ends  421  and  422  of the operating pin  420 . 
         [0097]    Further, the protrusions  511  are disposed not to correspond to each other in the front-rear direction. 
         [0098]    That is, as shown in  FIG. 4 , when the variable sliders  510  are positioned in one vertical line to face each other, the protrusions  511  are not positioned in the vertical line, such that as the variable sliders  510  are selective moves forward and rearward, the protrusion  511  of any one of the variable sliders  510  selectively presses the ends  421  and  422  of the operating pin  420 . 
         [0099]    The guide plate  520  may be a plate that can guide the variable sliders  510  moving straight through the guide rail  525  and have an area which can ensure the movement distance. 
         [0100]    Further, a fixing block  530  that fixes the variable slider  510  and the guide plate  520  is disposed under the guide plate  520 . 
         [0101]    The fixing block  530  is provided to firmly fix the guide plate  520  in the cylinder block, using connecting members. 
         [0102]    The operation of a variable compression ratio device having the above configuration according to an exemplary embodiment of the present invention is described hereafter. 
         [0103]    First, as shown in  FIG. 12A , as the variable shaft  100  is rotated by the actuator  600  in switching to a low compression ratio, for example, in one direction (clockwise in the present embodiment), the operating arms  500  and the variable sliders  510  move to the variable shaft  100 . 
         [0104]    Thereafter, as shown in  FIG. 13A , the protrusion  511  of any one of the variable sliders  510  presses one end  421  of the operating pin  420 . 
         [0105]    In this operation, the operating pin  420  slides to one side and the control channel  425  therein is opened, thereby controlling the path of the channel. 
         [0106]    That is, as shown in  FIG. 14A , the oil supplied through the oil supply channel  301  of the connecting rod  300  is supplied to the eccentric ring  400  selectively through the control channel  425  formed at one side in the operating pin  420 . 
         [0107]    Therefore, as shown in  FIG. 15A , the mounting protrusion  406  fixed to the eccentric ring  400  is rotated by hydraulic pressure generated in the oil chamber  408  at one side, and the eccentric ring  400  is rotated in one direction by the above rotation. 
         [0108]    Meanwhile, opposite to the switching into the low compression ratio, as shown in  FIG. 12B , in switching into a high compression ratio, as the variable shaft  100  is rotated in the opposite direction by the actuator  600 , the operating arms  500  and the variable sliders  510  move away from the variable shaft  100 . 
         [0109]    Thereafter, as shown in  FIG. 13B , the protrusion  511  of the other variable slider  510  presses one end  422  of the operating pin  420 . 
         [0110]    In this operation, the operating pin  420  move to the other side and the other control channel  423  therein is opened, thereby controlling the path of the channel. 
         [0111]    That is, as shown in  FIG. 14B , the oil supplied through the oil supply channel  301  of the connecting rod  300  is supplied to the eccentric ring  400  selectively through the other control channel  425  formed in the operating pin  420 . 
         [0112]    Therefore, as shown in  FIG. 15B , the mounting protrusion  406  fixed to the eccentric ring  400  is rotated by hydraulic pressure generated in the oil chamber  409  and the eccentric ring  400  is rotated in the opposite direction by the above operation. 
         [0113]    As described above, since the rotational direction of the eccentric ring  400  is selectively changed by the sliding direction of the piston pin  420 , a height difference ‘d’ shown in  FIG. 15  is generated, thereby varying the height of the piston  200 . 
         [0114]    Accordingly, it is possible to adjust the compression ratio inside the cylinder. 
         [0115]    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. 
         [0116]    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.