Patent Publication Number: US-8973540-B2

Title: Variable valve system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Korean Patent Application No. 10-2011-0100040 filed in the Korean Intellectual Property Office on Sep. 30, 2011, 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 valve system. More particularly, the present invention relates to a variable valve system having a device that can supply high pressure oil. 
     2. Description of Related Art 
     Generally, an automotive engine includes a combustion chamber in which fuel burns to generate power. The combustion chamber is provided with an intake valve for supplying a gas mixture containing the fuel and an exhaust valve for expelling burned gas. The intake and exhaust valves open and close the combustion chamber by a valve lift apparatus connected to a crankshaft. Also, in opening/closing the combustion chamber, a variable valve system is used to effectively control opening/closing timing of the valve. That is, the variable valve system varies valve opening/closing timing depending on the operation conditions of an engine to output appropriate power, to improve intake and exhaust efficiency, and to improve fuel consumption efficiency. 
     When the movement of the valve is controlled by hydraulic pressure in the variable valve system, if high pressure oil is not stably supplied at the right time, a movement difference of the valves between cylinders can occur. Also, if the pressure of the oil is not maintained at a predetermined level, the valve movement is not accurately controlled. Further, when oil leaks, a temporary operation failure of the variable valve system can be generated. 
     The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
     BRIEF SUMMARY 
     Various aspects of the present invention are directed to providing a variable valve system having advantages of accurately controlling a movement of a valve to be able to supply high pressure oil. 
     In an aspect of the present invention, a variable valve system may include a variable valve apparatus that controls opening/closing timing of an exhaust valve and an intake valve of an engine, and an oil supply device that supplies the variable valve apparatus with a pressured oil, wherein the exhaust valve and the intake valve are opened/closed by rotation of a camshaft, and the oil supply device engaged with the camshaft is operated by the rotation of the camshaft. 
     The oil supply device may include an oil compression cylinder that receives oil from a hydraulic pump and uses the oil to generate the pressured oil, a rocker arm that engages the camshaft with the oil compression cylinder such that the oil compression cylinder generates the pressured oil through the rotation of the camshaft, and an oil storage pipe that stores the pressured oil that is received from the oil compression cylinder. 
     One end of the rocker arm may have a roller and the other end thereof may have a piston press rod. 
     The roller may have a rotation axis that is parallel to a rotation axis of the camshaft and contacts a cam that is formed on the camshaft to lift/depress the one end of the rocker arm according to the rotation of the camshaft. 
     When the one end of the rocker arm is moved up/down, the other end thereof is moved up/down with respect to a rocker arm rotation axis of the rocker arm. 
     A length direction of the piston press rod coincides with an up/down direction of the other end of the rocker arm. 
     The piston press rod is fixed on the other end of the rocker arm by an engagement means. 
     The engagement means is a nut and a screw that are formed on the piston press rod. 
     A socket housing the piston press rod is formed at an upper end of the oil compression cylinder, and a first oil pipe and a second oil pipe fixed to the first oil pipe are formed in the oil compression cylinder. 
     The first oil pipe is diverged to be connected to the hydraulic pump that is disposed outside the oil compression cylinder, and the second oil pipe is diverged to be connected to the oil storage pipe that is disposed outside the oil compression cylinder. 
     A first valve is disposed between the first oil pipe and the hydraulic pump. 
     The first valve is a mono-directional check valve such that the oil moves from the hydraulic pump to the first oil pipe. 
     The socket, the first oil pipe, and the second oil pipe are sequentially disposed along the length direction of the oil compression cylinder. 
     An interior diameter of the second oil pipe is smaller than that of the first oil pipe. 
     A second valve is disposed between the first oil pipe and the second oil pipe. 
     The second valve is a mono-directional check valve such that the pressured oil moves from the first oil pipe to the second oil pipe. 
     A piston connected to the piston push rod is slidably disposed in the first oil pipe, and the piston is moved up/down by the up/down movement of the piston press rod. 
     The oil supply device may have a return means that returns the piston to an original position from a pressed position when the piston press rod moves in a down direction. 
     The piston press rod and the piston are integrally formed. 
     The socket and the first oil pipe are integrally formed. 
     The first oil pipe and the second oil pipe are integrally formed. 
     The socket, the first oil pipe, and the second oil pipe are integrally formed. 
     As described above, in an exemplary embodiment of the present invention, an oil supply device is operated by a rocker arm that contacts a camshaft of a variable valve system to be operated, and therefore high pressure oil can be supplied at the correct time. 
     Also, an oil storage pipe can maintain a predetermined level of oil pressure. Accordingly, the movement of a valve is accurately controlled and a valve movement difference between cylinders can be minimized. 
     In addition, a hydraulic pump does not need to supply high pressure oil and therefore the size of the hydraulic pump can be reduced. Accordingly, the overall weight of the vehicle can be reduced. 
     Further, when oil leaks, high pressure oil can be quickly supplied. Therefore, a temporary failure of a variable valve system can be prevented. 
     The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an engine cylinder head having a variable valve system according to an exemplary embodiment of the present invention. 
         FIG. 2  is a perspective view of an oil supply device according to an exemplary embodiment of the present invention. 
         FIGS. 3  ( a ) and ( b ) are schematic diagrams of an oil supply device that is operated by the rotation of a camshaft according to an exemplary embodiment of the present invention. 
         FIG. 4  is a block diagram showing a connection relationship of constituent elements and an oil supply route according to an exemplary embodiment of the present invention. 
     
    
    
     It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. 
     In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
     An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a perspective view of an engine cylinder head having a variable valve system according to an exemplary embodiment of the present invention. 
     As shown in  FIG. 1 , a variable valve system  10  is disposed in an engine compartment  60  and includes a variable valve apparatus  40 , a camshaft  50 , an oil supply device  20 , and a solenoid valve  30 . 
     The variable valve apparatus  40  controls opening/closing timing of an exhaust valve and an intake valve of an engine to be operated by hydraulic pressure. 
     The camshaft  50  is connected to the exhaust valve and the intake valve through a connecting member. The exhaust valve and the intake valve are opened/closed by the camshaft  50 . The structure of the camshaft and the connecting member that close/open the exhaust valve and the intake valve is known to a person of ordinary skill in the art, and therefore a detailed description thereof will be omitted. 
     The oil supply device  20  supplies the variable valve apparatus  40  with high pressure oil. Also, the oil supply device  20  is operated by the rotation of the camshaft  50 . 
     The solenoid valve  30  is disposed between the variable valve apparatus  40  and the oil supply device  20  to selectively open/close a high pressure oil passage that connects the oil supply device  20  with the variable valve apparatus  40 . 
     Hereinafter, with reference to  FIG. 2  and  FIG. 3 , formation and operation of the oil supply device  20  will be described. 
       FIG. 2  is a perspective view of an oil supply device according to an exemplary embodiment of the present invention. 
     As shown in  FIG. 2 , the oil supply device  20  includes an oil compression cylinder  22 , a rocker arm  24 , and an oil storage pipe  28 . 
     The oil compression cylinder  22  transforms oil that is received from the hydraulic pump  70  to high pressure oil. 
     The rocker arm  24  connects the camshaft  50  with the oil compression cylinder  22  such that high pressure oil is formed by the rotation of the camshaft  50  in the oil compression cylinder  22 . Also, the rocker arm  24  includes two ends, a roller  26  is rotatably disposed at one end of the rocker arm  24 , and a piston press rod  210  is fixed on the other end of the rocker arm  24  by an engagement means  212 . Further, the rocker arm  24  is rotatably connected to a rocker arm rotation axis  25 . Here, the rocker arm rotation axis  25  and the rotation axis of the roller  26  are parallel. 
     The rotation axis of roller  26  is parallel to the rotation axis of the camshaft  50 . A cam  52  is formed to the camshaft  50 , and the roller  26  is disposed to contact the cam  52  of the camshaft  50 . Further, the cam  52  can have an oval shape in which one part of a circle protrudes. Accordingly, the roller  26  is moved along a profile of the cam  52  by the rotation of the camshaft  50  and the rocker arm  24  is moved based on the rocker arm rotation axis  25 . Accordingly, the other end of the rocker arm  24  is moved up/down. In this process, the roller  26  is rotatably disposed, and therefore the movement of the rocker arm  24  is smoothly rotated. 
     The length direction of the piston press rod  210  is disposed to be almost parallel to the up/down movement direction of the other end of the rocker arm  24 . As described above, the piston press rod  210  is fixed on the other end of the rocker arm  24  by the engagement means  212 . Here, the engagement means  212  is a nut and a screw that can be formed at an upper end portion of the piston press rod  210  such that the screw is engaged with the nut. Accordingly, the piston press rod  210  is engaged with the rocker arm  24  by the engagement of the engagement means  212  with the piston press rod  210 . The engagement means  212  is not limited to a nut and a screw, and a method for engaging the piston press rod  210  with the rocker arm  24  can be variously changed by a person of ordinary skill in the art. 
     The oil storage pipe  28  stores high pressure oil that is supplied from the oil compression cylinder  22 . Also, the oil storage pipe  28  is connected to the solenoid valve  30  to transfer the high pressure oil that is transferred from the oil compression cylinder  22  to the solenoid valve  30 . As described above, the solenoid valve  30  selectively supplies the variable valve apparatus  40  with the high pressure oil. 
       FIGS. 3  ( a ) and ( b ) are schematic diagrams of an oil supply device that is operated by the rotation of a camshaft according to an exemplary embodiment of the present invention. Also, ( a ) of  FIG. 3  shows the cam  52  not lifting one end of the rocker arm  24 , and ( b )  FIG. 3  shows that cam  52  lifting one end of the rocker arm  24 . 
     As shown in ( a ) and ( b ) of  FIG. 3 , a socket  220  is disposed at an upper end of the oil compression cylinder  22  to house the piston press rod  210 , and a first oil pipe  224  and a second oil pipe  226  are formed inside the oil compression cylinder  22 . The socket  220 , the first oil pipe  224 , and the second oil pipe  226  are sequentially connected along the length direction of the oil compression cylinder  22 . Further, the interior diameter of the second oil pipe  226  is smaller than that of the first oil pipe  224 . 
     The socket  220  has a cup shape in which the lower side thereof is opened to house the piston press rod  210 . The socket  220  can be integrally formed with the first oil pipe  224 . Further, the first oil pipe  224  and the second oil pipe  226  can be integrally formed. That is, the socket  220 , the first oil pipe  224 , and the second oil pipe  226  can be integrally formed or each can be formed separately. 
     A piston  222  that can perform a reciprocal motion along the length direction of the first oil pipe  224  can be disposed in the first oil pipe  224 . Also, the piston  222  can subordinately perform a reciprocal motion according to up/down movement of the piston press rod  210  that is disposed in the socket  220 . Further, the piston  222  and piston press rod  210  can be integrally formed. 
     The first oil pipe  224  is diverged inside the oil compression cylinder  22  to be connected to a hydraulic pump  70  that is disposed outside the oil compression cylinder  22 . Accordingly, the oil compression cylinder  22  receives oil from the hydraulic pump  70 . A first valve  310  is disposed between the diverged first oil pipe  224  and the hydraulic pump  70 . The first valve  310  can be a mono-directional check valve such that oil is supplied from the hydraulic pump  70  to the first oil pipe  224 . 
     As shown in ( a ) of  FIG. 3 , if the cam  52  does not lift one end of the rocker arm  24 , the piston press rod  210  does not press the piston  222  downward. Accordingly, oil of the first oil pipe  224  that is received from the hydraulic pump  70  is not compressed by the piston  222 . 
     As shown in ( b ) of  FIG. 3 , if the cam  52  lifts one end of the rocker arm  24 , the rocker arm  24  is rotated based on the rocker arm rotation axis  25 . In this process, the other end of the rocker arm  24  is moved downward. That is, the piston press rod  210  that is disposed at the other end of the rocker arm  24  presses the piston  222  downward. Accordingly, the piston  222  compresses the oil inside the first oil pipe  224  to supply the second oil pipe  226  with the compressed oil. 
     As described above, because the interior diameter of the second oil pipe  226  is shorter than that of the first oil pipe  224 , the pressure of the oil is increased while the oil flows into the second oil pipe  226 . A second valve  320  is disposed between the first oil pipe  224  and the second oil pipe  226 . The second valve  320  can be a mono-directional check valve such that the oil flows from the first oil pipe  224  to the second oil pipe  226 . 
     Meanwhile, the cam  52  lifts one end of the rocker arm  24  and then causes one end of the rocker arm  24  to descend through the rotation of the camshaft  50 , and the rocker arm  24  rotates clockwise or anticlockwise based on the rocker arm rotation axis  25 . A return means can be disposed inside or outside the first oil pipe  224  so as to return the rocker arm  24 . 
     The second oil pipe  226  is diverged inside the oil compression cylinder  22  to be connected to the oil storage pipe  28  that is disposed in the oil compression cylinder  22 . Accordingly, the high pressure oil is transferred from the oil compression cylinder  22  to the oil storage pipe  28 . 
     The high pressure oil that is transferred to the oil storage pipe  28  is stored in the oil storage pipe  28  to be supplied to the variable valve apparatus  40  by selectively opening the solenoid valve  30 . 
       FIG. 4  is a block diagram showing a connection relationship of constituent elements and an oil supply route according to an exemplary embodiment of the present invention. 
     As shown in  FIG. 4 , in a variable valve system according to an exemplary embodiment of the present invention, oil sequentially circulates through the hydraulic pump  70 , the oil supply device  20 , the oil storage pipe  28 , the solenoid valve  30 , and the variable valve apparatus  40 . 
     The oil supply route and the relationship of the constituent elements are described with reference to  FIG. 1 ,  FIG. 2 , and  FIG. 3 , and the oil supply route is shown in  FIG. 4  so as to offer better understanding of the variable valve system  10  having the oil supply device  20  that generates high pressure oil to efficiently operate the variable valve apparatus  40 . 
     As described above, because the operation of the intake valve and exhaust valve of the engine and the operation of the oil supply device  20  are performed by one camshaft  50  in an exemplary embodiment of the present invention, high pressure oil can be supplied at the correct time. Also, the pressure of the oil can be maintained higher than a predetermined value by the oil storage pipe  28 . Accordingly, the movement of the valve is accurately controlled and the movement difference between cylinders can be minimized. Further, even if oil leaks, high pressure oil is instantly supplied to the variable valve apparatus  40 , and therefore the operation failure of the variable valve system can be prevented. Also, the hydraulic pump  70  does not need to generate high pressure oil and therefore the capacity of the hydraulic pump  70  can be reduced. Accordingly, the overall weight of the vehicle can be reduced. 
     For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “inner” and “outer” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
     The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.