Abstract:
A variable compression ratio apparatus may include an external piston, a piston pin mounted in the external piston and a connecting rod, including an internal piston including a slot and sliding in an interior circumference of the external piston, wherein the piston pin passes through the internal piston and the external piston, a latching pin passing through the piston pin and selectively sliding therein, variable sliders disposed to selectively contact one of both ends of the latching pin, at both sides thereof to push the one of the both ends to the opposite side, and a support plate slidably supporting the variable sliders such that the variable sliders reciprocate perpendicular to length direction of the latching pin, wherein one end of a connecting arm selectively rotating may be connected to the variable slider and a sliding direction of the variable sliders may be controlled by rotation of the connecting arm.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Korean Patent Application No. 10-2010-0067412 filed in the Korean Intellectual Property Office on Jul. 13, 2010, the entire contents of which is incorporated herein for all purposes by this reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a variable compression ratio apparatus. More particularly, the present invention relates to a variable compression ratio apparatus that changes compression ratio of gas mixture in a combustion chamber in accordance with operational conditions of an engine. 
     2. Description of Related Art 
     In general, thermal efficiency of heat engines increases when compression ratio is high and when igniting timing increases to a predetermined level in spark ignition engines. However, the spark ignition engines have a limit in increasing the ignition timing because the engines may be damaged by abnormal combustion when the ignition timing is increased at high compression ratio, which necessarily reduce the output power. 
     A variable compression ratio (VCR) apparatus is an apparatus that changes compression ratio of gas mixture in accordance with operational conditions of the engine. According to the compression ratio apparatus, fuel efficiency is improved by increasing the compression ratio of gas mixture under the low load condition of the engine, and knocking is prevented and the engine output is improved by reducing the compression ratio of the gas mixture under the high load condition of the engine. 
     In order to achieve the variable compression ratio, an oil chamber is formed inside a bias ring disposed in a small portion of a connecting rod and the bias ring is eccentrically rotated by hydraulic pressure generated by supplying oil into the oil chamber, which has been proposed; however, the variable compression ratio apparatus according to the related art has a problem that the distance from the bias ring to the center of the oil chamber is small, such that pressure for maintaining the position of the bias ring in the oil chamber is largely increased when explosion pressure is applied, and it is difficult to maintain the compression ratio. 
     Further, there is a problem requiring excessive oil pressure, which is needed to change the compression ratio. 
     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 
     Various aspects of the present invention are directed to provide a variable compression ratio apparatus having advantages of having an improved structure to efficiently change compression ratio in a cylinder. 
     In an aspect of the present invention, the variable compression ratio apparatus including an external piston, a piston pin mounted in the external piston, a crankshaft, and a connecting rod pivotally connecting the external piston with the crankshaft, may include an internal piston including a slot and sliding up or down in close contact to an interior circumference of the external piston, wherein the piston pin passes through the slot of the internal piston and the external piston, a latching pin passing through the piston pin and selectively sliding therein, variable sliders disposed to selectively contact one of both ends of the latching pin, at both sides thereof to push the one of the both ends to the opposite side, and a support plate slidably supporting the variable sliders such that the variable sliders reciprocate in perpendicular direction to the length direction of the latching pin, wherein one end of a connecting arm selectively rotating may be connected to the variable slider and a sliding direction of the variable sliders may be controlled by rotation of the connecting arm. 
     An oil chamber may be formed between the inside of the external piston and the top of the internal piston so as to selectively store oil therein to generate hydraulic pressure, wherein an oil supply channel may be formed in the connecting rod to supply oil to the oil chamber. 
     A control channel may be formed in the latching pin to receive oil from the oil supply channel formed in the connecting rod and oil in the control channel may be selectively supplied into the oil chamber by reciprocation of the latching pin. 
     Protrusions may be formed on an inner side of the variable sliders to correspond to the both ends of the latching pin, and the protrusions do not face each other in movement direction therebetween. 
     The rotary shaft and the variable slider may be connected by the connecting arm, wherein an adaptor integrally rotating with the rotary shaft may be mounted on an external circumferential surface of the rotary shaft, the rotary shaft and the connecting arm may be connected by a first hinge portion of the adaptor, and the connecting arm may be connected with the variable slider by a second hinge portion, such that as the rotary shaft selectively rotates in one direction, the connecting arm reciprocates straight by means of the first hinge portion and the second hinge portion. 
     A guide rail that guides the variable sliders reciprocating forward/backward may be formed on one side of a fixing block wherein the fixing block fixes the support plate and slidably supports the variable sliders. 
     The rotary shaft may be operated by a separate vacuum actuator. 
     An oil supply line may be formed on one side in the internal piston and an oil discharge line may be formed on the other side thereof, wherein an oil discharge hole may be formed through the other side of the internal piston to communicate with an oil chamber through the oil discharge line. 
     An oil supply hole may be formed through the one side of the internal piston to selectively communicate with a control channel of the latching pin, wherein a first check valve may be disposed in the oil supply line to selectively connect the control channel of the latching pin to the oil chamber and a second check valves may be disposed in the oil discharge line to selectively discharge the oil from the oil chamber to the outside, wherein a sliding pin may be disposed in the oil supply line to slide therein to open the oil supply line such that the control channel fluid-communicates with the oil chamber, when oil may be supplied to a side of the sliding pin. 
     An elastic member may be disposed at one end of the sliding pin to elastically support the end such that the oil supply line may be closed by the elastic member, when oil may be not supplied to the side of the sliding pin. 
     Locking protrusions formed to the sliding pin protrude from an external circumferential surface thereof in perpendicular direction to a motion direction of the sliding pin and integrally moves by a motion of the sliding pin, wherein an operational groove may be formed on the external circumferential surface of the internal piston and the locking protrusions protrude through operational holes formed through the operational groove. 
     A plurality of support protrusions may be formed downwards on the operation grooves in the internal piston and an operational ring having protrusions corresponding to the support protrusions on the interior circumference thereof may be inserted in the operation grooves, wherein the locking protrusions of the sliding pin and the protrusions of the operational ring may be engaged such that, as the sliding pin reciprocates, the operational ring selectively rotates in both directions by the protrusions of the sliding pin and the protrusions of the operational ring may be selectively engaged with the support protrusions in accordance with reciprocating direction of the operational ring. 
     According to the exemplary embodiment of the present invention, since hydraulic pressure may be selectively released or supplied through the oil chamber formed between the external piston and the internal piston, such that it may be possible to achieve a stable and efficient variable compression ratio. 
     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 
         FIG. 1  is a perspective view showing a variable compression ratio apparatus according to an exemplary embodiment of the present invention. 
         FIG. 2  is a perspective view showing a driving part of the variable compression ratio apparatus according to an exemplary embodiment of the present invention. 
         FIG. 3  is an exploded perspective view of  FIG. 2 . 
         FIG. 4  is an exploded perspective view showing an operation unit of the variable compression ratio apparatus according to an exemplary embodiment of the present invention. 
         FIG. 5  is a cross-sectional view showing a connecting rod used in the variable compression ratio apparatus according to an exemplary embodiment of the present invention. 
         FIG. 6  is a perspective view showing a piston pin used in the variable compression ratio apparatus according to an exemplary embodiment of the present invention. 
         FIG. 7  is a cross-sectional view showing when a latching pin has moved to one side from the combination position shown in  FIG. 6 . 
         FIG. 8  is a cross-sectional view when the latching pin has moved to the other side from the combination position shown in  FIG. 6 . 
         FIG. 9  is a view when the operation unit of the variable compression ratio apparatus according to an exemplary embodiment of the present invention operates at a high compression ratio and a low compression ratio. 
         FIG. 10  is a cross-sectional view when the operation unit of  FIG. 9  is at a high compression ratio and a low compression ratio. 
         FIG. 11  is a cross-sectional view showing a sliding pin at a high compression ratio and a low compression ratio. 
         FIG. 12  is a perspective view showing a piston used in the variable compression ratio apparatus according to an exemplary embodiment of the present invention. 
         FIG. 13  is a cross-sectional view showing the front and rear sides of the piston used in the variable compression ratio apparatus according to an exemplary embodiment of the present invention. 
         FIG. 14  is a horizontal cross-sectional view showing the piston used in the variable compression ratio apparatus according to an exemplary embodiment of the present invention. 
         FIG. 15  is a front view of  FIG. 14 . 
         FIG. 16  is a perspective view showing a variable slider used in the variable compression ratio 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 OF THE INVENTION 
     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. 
     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 showing a variable compression ratio apparatus according to an exemplary embodiment of the present invention. 
       FIG. 2  is a perspective view showing a driving part of the variable compression ratio apparatus according to an exemplary embodiment of the present invention. 
       FIG. 3  is an exploded perspective view of  FIG. 2 . 
       FIG. 4  is an exploded perspective view showing an operation unit of the variable compression ratio apparatus according to an exemplary embodiment of the present invention. 
       FIG. 5  is a cross-sectional view showing a connecting rod used in the variable compression ratio apparatus according to an exemplary embodiment of the present invention. 
       FIG. 6  is a perspective view showing a piston pin used in the variable compression ratio apparatus according to an exemplary embodiment of the present invention. 
       FIG. 7  is a cross-sectional view showing when a latching pin has moved to one side from the combination position shown in  FIG. 6 . 
       FIG. 8  is a cross-sectional view when the latching pin has moved to the other side from the combination position shown in  FIG. 6 . 
       FIG. 9  is a view when the operation unit of the variable compression ratio apparatus according to an exemplary embodiment of the present invention operates at a high compression ratio and a low compression ratio. 
       FIG. 10  is a cross-sectional view when the operation unit of  FIG. 9  is at a high compression ratio and a low compression ratio. 
       FIG. 11  is a sliding pin at a high compression ratio and a low compression ratio. 
       FIG. 12  is a perspective view showing a piston used in the variable compression ratio apparatus according to an exemplary embodiment of the present invention. 
       FIG. 13  is a cross-sectional view showing the front and rear sides of the piston used in the variable compression ratio apparatus according to an exemplary embodiment of the present invention. 
       FIG. 14  is a horizontal cross-sectional view showing the piston used in the variable compression ratio apparatus according to an exemplary embodiment of the present invention. 
       FIG. 15  is a front view of  FIG. 14 . 
       FIG. 16  is a perspective view showing a variable slider used in the variable compression ratio apparatus according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 1  to  FIG. 4 , a variable compression ratio apparatus according to the exemplary embodiment of the present invention includes a driving part P composed of a rotary shaft  100 , a connecting arm  110 , and a variable slider  120 , and an operation unit F composed of an external piton  200  reciprocating by means of explosion of fuel in a cylinder of an engine and an internal piston  210  sliding in the external piston  200 , wherein the internal piston  210  includes a slot  150  and the piston pin  230  passes through the slot  150 . The slot  150  is larger than the diameter of a piston pin  230  to allow a sliding motion of the internal piston  210  in the external piston  200 . 
     The rotary shaft  100  is selectively rotated in both directions by an actuator  300  separately disposed outside a cylinder block (not provided with reference numeral). 
     The actuator  300  may be any device that can operate the rotary shaft  100 , such as a vacuum actuator. 
     In this configuration, the external piston  200  mounted in the cylinder block is disposed to reciprocate along the inner wall of the cylinder and operated by a crankshaft  400  operating with the external piston  200 , and the external piston  200  and the connecting rod  220  are connected by the piston pin  230  at the upper end of the connecting rod  220 . 
     Further, a latching pin  240  vertically reciprocating in the piston pin  230  is provided. 
     Further, a space is defined between the external piston  200  and the internal piston  210 . 
     That is, the internal piston  210  is disposed to vertically reciprocate in close contact to the inner circumference of the external piston  200  and an oil chamber  212  temporarily storing oil and generating pressure is formed in the space that is defined when the internal piston  210  moves down. 
     Referring to  FIG. 5 , a separate oil supply channel  221  may be formed in the connecting rod  220  to supply oil into the oil chamber  212  through a control channel  242  of the latching pin  240 . 
     That is, the oil supplied through the oil supply channel  221  selectively communicates with the oil chamber  212  by selectively opening the control channel  241  of the latching pin  240 , in accordance with reciprocation of the latching pin  240 , as explained hereinafter. 
     That is, as shown in  FIG. 7  and  FIG. 8 , the control channel  241  is formed in the latching pin  240 , communicates with the oil supply channel  221  and selectively communicates with the oil chamber  212  in accordance with left-right reciprocation of the latching pin  240 , such that the oil flows into the oil chamber  212 . 
     The latching pin  240  includes check valves  215  and  315  and inner surface of the piston pin  230  includes locking grooves  255  such that check valves  215  and  315  are selectively open by being alternatively engaged into the locking grooves  255  in accordance with left-right reciprocation of the latching pin  240 . 
     In  FIG. 7 , the check valve  215  is configured to control an oil flow of oil supply line  213  such that when the latching pin  240  moves in the left direction, a ball of the check valve  215  is locked to the locking groove  255  and thus the oil supply line  213  opens to supply oil to the oil chamber  212  through oil supply hole  228  formed in the internal piston  210 . 
     In contrast, in  FIG. 8 , the check valve  315  is configured to control an oil flow of oil discharge line  214  such that when the latching pin  240  moves in the right direction, a ball of the check valve  315  is locked to the locking groove  255  and thus the oil discharge line  214  opens to discharge oil from the oil chamber  212  through oil discharge hole  227  formed in the internal piston  210 . 
     In this operation, the rotary shaft  100  is rotated about the axis by the separate actuator  300 . The actuator  300  may be a vacuum actuator, as described above. 
     Referring to  FIG. 2  and  FIG. 3 , two adaptors  101  may be attached to the outer circumferential surface of the rotary shaft  100 . 
     The pair of adaptors  101  connects a pair of connecting arms  110  with a pair of variable sliders  120  to integrally operate in accordance with rotation of the rotary shaft  100 . 
     A first hinge portion  102  is formed at one end of each of the adaptors  101 . 
     The adaptor  101  and the rotary shaft  100  are connected by the first hinge portion  102 , and the connecting arm  110  and the variable slider  120  are connected by a second hinge portion  103  formed at the other ends of the connecting arms  110 . 
     That is, as the rotary shaft  100  is rotated by the actuator  300 , the connecting arm  110  rotated by the first hinge portion  102  of the adaptor  101  reciprocates straight. 
     Therefore, the variable slider  120  hinged to the second hinge portion  103  of the connecting arm  110  also reciprocates straight. 
     In this configuration, the variable slider  120  has a support plate  122  with a guide rail, which assists straight motion, on the outer side. 
     Further, as shown in  FIG. 16 , protrusions  123  are formed on the opposite inner sides of the variable slider  120 . 
     The protrusions  123  is disposed to correspond to both ends of the latching pin  240 . 
     Further, both protrusions  123  are positioned without overlapping each other in the front-rear direction. 
     That is, when both variable sliders  120  are on the same vertical line, opposite to each other, the protrusions  123  are not positioned on the same vertical line, such that as the variable sliders  120  selectively moves forward and backward, the protrusion  123  of any one of the variable sliders  120  presses any one end  242  of the latching pin  240 . 
     The support plate  122  may have a plate shape that is wide such that ensure a movement distance while guiding the variable slider  120  moving straight along the guide rail. 
     Further, a fixing block  124  is formed at the lower portion of the support plate  122  to slidably support the variable slider  120  and to fix the support plate  122 . 
     The fixing block  124  is provided to firmly fix the variable slider  120  and the support plate  122  in the cylinder block, using a connecting member. 
     The fixing block  124  includes a guide rail  144  such that the variable slider  120  slides thereon. 
     Referring to  FIG. 9  to  FIG. 12 , oil flow at a high compression ratio and a low compression ratio in the variable compression ratio apparatus according to the exemplary embodiment of the present invention can be seen. 
       FIG. 10A  and  FIG. 12  A show a low compression ratio, where the oil discharge line  214  formed in the internal piston  210  is opened by the check valve  315  and the oil supply line  213  is closed by the check valve  214  by right motion of the latching pin  240 . 
     That is, since the check valve  315  in the oil discharge line  214  of the internal piston  210  is opened and the check valve  215  in the oil supply line  213  is closed, the oil in the oil chamber  212  is discharged through a discharge hole  232  formed through one side of the internal piston  210 . 
     In an exemplary embodiment of the present invention, a sliding pin  216  is slidably disposed in the oil supply line  213  and elastically biased by an elastic member  225 . Accordingly, in the low compression ratio, the sliding pin  216  in the oil supply line  213  is moved in the left direction by the elastic member  225  since hydraulic pressure is not supplied in the oil supply line  213 . 
     Simultaneously, the hydraulic pressure generated in the oil chamber  212  is removed, such that the external piston  200  moves down. 
       FIG. 10B  and  FIG. 11B  show a high compression ratio, where the oil supply line  213  formed in the internal piston  210  is open by the latching pin  240 . 
     That is, while the oil is supplied from the oil supply line  213  of the internal piston  210 , the oil discharge line  214  at the other side is closed by the check valve  315 , such that hydraulic pressure is generated in the oil chamber  212 . 
     In an exemplary embodiment of the present invention, a sliding pin  216  is slidably disposed in the oil supply line  213  and elastically biased by an elastic member  225 . Accordingly, in the high compression ratio, the sliding pin  216  in the oil supply line  213  is moved in the right direction while hydraulic pressure is supplied in the oil supply line  213  as shown in  FIG. 11B . 
     Further, as shown in  FIG. 14  and  FIG. 15 , an operational protrusion  217  formed to the sliding pin  216  protrudes vertically outward with the motion direction of the sliding pin from the external circumferential surface, surrounding the external circumferential surface of the sliding pin  216 . 
     Further, an operational groove  218  is formed on the external circumferential surface of the internal piston  210 . 
     The operational groove  218  has an operational hole  219  formed radially outward through the groove. 
     In this configuration, the operational protrusion  217  protrudes outside the internal piston  210  through the operational hole  219  and operates with a plurality of locking protrusions  223  formed on the inner circumference of an operational ring  222 , which is described below. 
     The operational ring  222  is fitted on the external circumferential surface of the internal piston  210 . 
     Since the operational ring  222  has a ring shape and has the locking protrusions  223  substantially symmetric at both sides, on the interior circumference, as described above. 
     The locking protrusions  223  selectively rotate in both directions by engaging with each other in accordance with reciprocation of the operational protrusion  217  of the sliding pin  216 . 
     In this configuration, a support protrusion  224  protruding downward is formed above the operational groove  218 . 
     That is, as shown in  FIG. 16 , as the operational ring  222  is rotated by the operational protrusion  217  of the sliding pin  216 , the locking protrusions  223  of the operational ring  222  are selectively supported by the support protrusions  224  of the operational groove  218 , or engaged with each other in the up-down direction. Therefore, the height changes by the distance ‘d’, such that the compression ratio changes. 
     According to the variable compression ratio apparatus according to the exemplary embodiment of the present invention, it is possible to stably carry combustion load at a high compression ratio in comparison to the structures of the related art, such that is it possible to stably achieve a compression ratio. 
     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.