# Patent

## Title
Multiple variable valve lift apparatus

## Abstract

A multiple variable valve lift apparatus may include a camshaft rotating by drive of an engine, at least two cam portions slidably disposed on the camshaft and rotatable together with the camshaft, and forming a high cam and a low cam, a valve opening/closing unit operated by one of the high or low cams, at least two operating unit movable along the camshaft to move the at least two cam portions along the camshaft, a control portion selectively moving the operating unit along the camshaft, a pin disposed at the control portion, and a guide rail formed in a groove shape on an exterior circumference of the operating unit such that the pin is insert therein and guiding relative movement of the pin according to rotation of the camshaft and the operating unit such that the operating unit is moved along an axial direction of the camshaft by the pin.

## Background
CROSS-REFERENCE TO RELATED APPLICATION
The present application claims priority to Korean Patent Application No. 10-2013-0101696 filed on Aug. 27, 2013, 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 multiple variable valve lift apparatus. More particularly, the present invention relates to a multiple variable valve lift apparatus to mitigate impact generated during changing valve lift.
2. Description of Related Art
Generally, an internal combustion engine receives fuel and air into a combustion chamber and generates power by combusting the fuel and the air. Herein, an intake valve is operated by drive of a camshaft, and air flows into the combustion chamber during when the intake valve is open. In addition, an exhaust valve is operated by drive of a camshaft, and air is exhausted from the combustion chamber while the exhaust valve is open.
Meanwhile, optimal operations of the intake valve or the exhaust valve are determined according to rotation speed of the engine. That is, lift and open/close timing of the valves are properly controlled according to rotation speed of the engine. A plurality of cams may be disposed at a camshaft such that a valve is operated by various lift for realizing suitable valve operation according to rotation speed of an engine.
In case that the plurality of cams are provided so as to drive the valve by various lift, the valve lift is changed as a cam portion forming a high cam and a low cam is moved along an axial direction of the camshaft such that a high cam or a low cam is selected according to situation. For example, a guide rail is formed at the cam portion or an operating unit moving the cam portion along an axial direction of the camshaft, and a pin is selectively inserted into the guide rail, and the valve lift can be changed according to the cam portion or the operating unit is moved along an axial direction of the camshaft by relative movement of the pin with the rotation of the camshaft.
At this time, impact may be generated at the moment that the pin to be guided by the guide rail is inserted into or contacted to the guide rail. Further, the impact generates noise and aggravates stability of changing valve lift.
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 multiple variable valve lift apparatus having advantages of preventing impact generated during changing valve lift.
In an aspect of the present invention, a multiple variable valve lift apparatus, may include a camshaft rotating by drive of an engine, at least two cam portions disposed on an exterior circumference of the camshaft to be slidably movable along an axial direction of the camshaft and to be rotated together with the camshaft, and forming a high cam and a low cam, a valve opening/closing unit operated by one of the high cam or the low cam formed at the cam portions, at least two operating units slidably disposed to move along the axial direction on an exterior circumference of the camshaft so as to move the at least two cam portions along the axial direction of the camshaft, a control portion selectively moving the operating unit along the axial direction of the camshaft, a pin disposed at the control portion, and a guide rail formed in a groove shape on an exterior circumference of the operating unit such that the pin is inserted therein and guiding relative movement of the pin according to rotation of the camshaft and the operating unit such that the operating unit is moved along the axial direction of the camshaft by the pin, wherein the operating unit is moved as the pin of the control portion is inserted into the guide rail of the operating unit, and the guide rail is formed in a shape combined a straight line with a curved line along the exterior circumference of the operating unit for preventing impact generated by contacting with the pin.
The guide rail may include an escaping section starting contact with the pin, a moving section guiding that the operating unit is moved along the axial direction of the camshaft by the contacted pin, and an escaping section formed to escape the contacted pin, wherein the width of the pin is formed to be shorter than the width of the guide rail, and a gap is formed between the pin inserted into the guide rail and a side surface of the guide rail.
The moving section may include a gap reducing section formed in a gradually curved surface and adapted that a phase thereof is changed as the width of the gap along an axial direction from a starting point to a predetermined point of the moving section, a contact maintaining section formed that the phase thereof is equally maintained along an axial direction from an ending point of the gap reducing section to a predetermined point of the moving section, and a pin moving section formed from an ending point of the contact maintaining section to an ending point of the moving section, and guiding relative movement of the pin with the operating unit along the axial direction of the camshaft such that the operating unit is moved by the pin.
In case that a shape of the moving section is represented by a graph having a horizontal axis indicating rotated angles of the camshaft and the operating unit and a vertical axis indicating phases of the moving section in the axial direction of the camshaft, the gap reducing section is formed in a curved line having a shape that slope of the graph is gradually decreased.
The contact maintaining section is formed in a straight line such that slope of the graph is 0.
The pin moving section may include an accelerating section extended from the ending point of the contact maintaining section, and a decelerating section extended from an ending point of the accelerating section to the ending point of the moving section, wherein the accelerating section is formed in a curved line such that slope of the graph is gradually increased, and wherein the decelerating section is formed in a curved line such that slope of the graph is gradually decreased.
Slope of the graph is converged to 0 over finishing the decelerating section.
The escaping section of the guide rail is formed such that a depth of the groove is gradually reduced from a point meeting with the moving section toward the extending direction.
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 schematic diagram of a multiple variable valve lift apparatus according to an exemplary embodiment of the present invention.
FIG. 2 is a developed diagram of operating units and an interlock unit according to an exemplary embodiment of the present invention.
FIG. 3 is a cross-sectional view of an operating unit and an interlock unit according to an exemplary embodiment of the present invention.
FIG. 4 is a drawing showing a pin inserted into a guide rail according to an exemplary embodiment of the present invention.
FIG. 5 is a graph representing a shape of a guide rail according to an exemplary embodiment of the present invention by an inclination with reference to rotated angles.



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 schematic diagram of a multiple variable valve lift apparatus according to an exemplary embodiment of the present invention.
As shown in FIG. 1, a multiple variable valve lift apparatus 1 according to an exemplary embodiment of the present invention includes a camshaft 100, cam portions 40 and 60, a solenoid 10, an operating unit 30 and 50, an interlock unit 70, and a pin operating unit 20. Herein, the operating unit 30 and 50 and interlock unit 70 compose an operating portion which operates for changing valve lift, and the solenoid 10 and the pin operating unit 20 compose a control portion which controls the operation of the operating unit 30 and 50 and interlock unit 70.
The camshaft 100 is a shaft which is rotated by rotation of a crankshaft of an engine. The camshaft 100 is well-known to a person of ordinary skill in the art such that a detailed description thereof will be omitted.
The cam portion 40 and 60 is a portion that a cam 41, 42, 48, 49, 61, 62, 68, and 69 for operating an intake valve or an exhaust valve of an engine is formed, and is formed in a hollow cylinder shape having uniform thickness. In addition, the camshaft 100 is inserted into the hollow of the cam portion 40 and 60. Thus, an entire shape of the cam portion 40 and 60 and the camshaft 100 is to be a shape that the cam portion 40 and 60 is protruded from an exterior circumference of the camshaft 100. Herein, the hollow of the cam portion 40 and 60 is formed in a circle shape corresponding to an external circumference of the camshaft 100. That is, an interior circumference of the cam portion 40 and 60 is contacted to an exterior circumference of the camshaft 100. Furthermore, an interior circumference of the cam portion 40 and 60 is slid on an exterior circumference of the camshaft 100 such that the cam portion 40 and 60 is moved along an axial direction of the camshaft 100. Meanwhile, the cam portion 40 and 60 is disposed to rotate together with the camshaft 100. The composition that the cam portion 40 and 60 is movable along an axial direction of the camshaft 100, and the cam portion 40 and 60 and the camshaft 10 are coupled with each other such that the cam portion 40 and 60 and the camshaft 100 are rotated together can be realized by types such as the spline according to design of a person of ordinary skill in the art.
The cam portion 40 and 60 includes two cam portions 40 and 60 which are a first cam portion 40 and a second cam portion 60. Herein, the first cam portion 40 is adapted to operate a valve disposed at one cylinder, and the second cam portion 60 is adapted to operate a valve disposed at another cylinder. Further, the first cam portion 40 can be provided for two valves disposed at one cylinder, and the second cam portion 60 can be provided for two valves disposed another cylinder.
In FIG. 1, a multiple variable valve lift apparatus 1 which is adapted to operate a valve at two cylinders of a multi-cylinder engine having at least two cylinders is shown. Herein, the valve is the intake valve or the exhaust valve.
The first cam portion 40 includes a first low cam 41, a first high cam 42, a second low cam 48, a second high cam 49, and a first connecting portion 45.
The first low cam 41, the first high cam 42, the second low cam 48, and the second high cam 49 may be formed in a general cam shape that an exterior circumference of a cut-plane is formed in an oval shape such that one end thereof is relatively further protruded to compare with the other end thereof. Typically, the one end of the cam is called “cam lobe”, and the other end of the cam is called “cam base”.
The cam base is a base circle of a cam, a part of an external circumference of the cam, which is formed in an arc shape having uniform radius. In addition, the cam lobe is a part of an external circumference of the cam 41, 42, 48, and 49 which pushes the valve opening/closing unit 5 from when opening of the valve is started to when closing of the valve is ended by rotation of the cam 41, 42, 48, and 49. Herein, the valve opening/closing unit 5 is a device that one end thereof is rolling-contacted with the cams 41, 42, 48, and 49 so as to be operated to open/close the valves by the rotation of the cams 41, 42, 48, and 49. The valve opening/closing unit 5 is well-known to a person of an ordinary skill in the art such that a detailed description thereof will be omitted.
The first low cam 41 and the first high cam 42 are formed to be close with each other, and the second low cam 48 and the second high cam 49 are formed to be close with each other. In addition, the first low cam 41 and the first high cam 42 are paired with each other so as to operate one valve, and the second low cam 48 and the second high cam 49 are paired with each other so as to operate the other valve.
The first connecting portion 45 connects the pair of the first low cam 41 and the first high cam 42 with the pair of the second low cam 48 and the second high cam 49. That is, the first connecting portion 45 is disposed between the pair of the first low cam 41 and the first high cam 42 and the pair of the second low cam 48 and the second high cam 49, and the first cam portion 40 is integrally molded.
Meanwhile, the cam lobes of the first and second high cams 42 and 49 may be further protruded from an exterior circumference of the camshaft 100 to compare with the cam lobes of the first and second low cams 41 and 48. Thus, the first and second high cams 42 and 49 realize high lift of the valve, and the first and second low cams 41 and 48 realize low lift of the valve. That is to say, the high lift of the valve is realized when the valve opening/closing unit 5 is connected to rolling-contact with the high cams 42 and 49, and the low lift of the valve realized when the valve opening/closing unit 5 is connected to rolling-contact with the low cams 41 and 48. Furthermore, the first and second high cams 42 and 49 or the first and second low cams 41 and 48 for operating the valve are selected according to the first cam portion 40 moves along an axial direction of the camshaft 100.
The second cam portion 60 includes a third low cam 61, a third high cam 62, a fourth low cam 68, a fourth high cam 69, and a second connecting portion 65.
Herein, the descriptions regarding the third low cam 61, the third high cam 62, the fourth low cam 68, the fourth high cam 69, and the second connecting portion 65 are respectively corresponded to the descriptions regarding the first low cam 41, the first high cam 42, the second low cam 48, the second high cam 49, and the first connecting portion 45, and thus will be omitted.
The solenoid 10 is provided so as to transform the rotation motion of the camshaft 100 to the rectilinear motion of the first cam portion 40 or the second cam portion 60. That is, the first cam portion 40 or the second cam portion 60 is rectilinearly moved along an axial direction of the camshaft 100 according to the rotation motion of the camshaft 100 if the solenoid 10 is operated. Herein, the solenoid 10 operated to on or off by an electrical control the solenoid 10 is well-known to a person of an ordinary skill in the art such that a detailed description thereof will be omitted.
The operating unit 30 and 50 is formed in a cylinder shape having a hollow like to the first and second cam portions 40 and 60, and the camshaft 100 is inserted into the hollow of the operating unit 30 and 50 such that the operating unit 30 and 50 is disposed on an exterior circumference of the camshaft 100. In addition, the hollow of the operating unit 30 and 50 may be formed that an internal circumference of the operating unit 30 and 50 is corresponded with an external circumference of the camshaft 100. Further, an external circumference of the operating unit 30 and 50 is formed in a circle shape having uniform radius. Furthermore, an interior circumference of the operating unit 30 and 50 is slid on an exterior circumference of the camshaft 100 such that the operating unit 30 and 50 is moved along an axial direction of the camshaft 100, and the operating unit 30 and 50 is adapted to rotate together with the camshaft 100.
The solenoid 10 includes a low lift solenoid 12 and a high lift solenoid 14, and the operating unit 30 and 50 includes a low lift operating unit 30 and a high lift operating unit 50.
The low lift operating unit 30 is integrally formed with the first cam portion 40 or is adapted to move together with the first cam portion 40. In addition, the low lift operating unit 30 rotating together with the camshaft 100 is moved in one direction along an axial direction of the camshaft 100 according to the operation of the low lift solenoid 12. Thus, the low lift of the valve is realized. While it is shown that the low lift operating unit 30 is disposed at one end of the first low cam 41 in FIG. 1, it is not limited thereto in the disclosed embodiment.
For better comprehension and convenience of description, a forward direction will be defined a word as the one direction that the low lift operating unit 30 is moved for realizing the low lift of the valve.
The high lift operating unit 50 is integrally formed with the second cam portion 60 or adapted to move together with the second cam portion 60. In addition, the high lift operating unit 50 rotating together with the camshaft 100 is moved in the other direction along an axial direction of the camshaft 100 according to the operation of the high lift solenoid 14. Thus, the high lift of the valve is realized. While it is shown that the high lift operating unit 50 is disposed at one end of the third high cam 62 in FIG. 1, it is not limited thereto in the disclosed embodiment.
For better comprehension and convenience of description, a reverse direction will be defined a word as the other direction that the high lift operating unit 50 is moved for realizing the high lift of the valve.
The interlock unit 70 is formed in a cylinder shape having a hollow like to the operating units 30 and 50 and the first and second cam portions 40 and 60, and the camshaft 100 is inserted into the hollow of the interlock unit 70 such that the interlock unit 70 is disposed on an exterior circumference of the camshaft 100. In addition, the hollow of the interlock unit 70 may be formed that an internal circumference of the interlock unit 70 is corresponded with an external circumference of the camshaft 100. Further, an external circumference of the interlock unit 70 is formed in a circle shape having uniform radius. Furthermore, an interior circumference of the interlock unit 70 is slid on an exterior circumference of the camshaft 100 such that the interlock unit 70 is moved along an axial direction of the camshaft 100, and the interlock unit 70 is adapted to rotate together with the camshaft 100.
The interlock unit 70 is disposed between the integrally formed first cam portion 40 and the integrally formed second cam portion 60. In addition, the interlock unit 70 performs a function that the first cam portion 40 and the second cam portion 60 are interlocked with each other.
The interlock unit 70 is operated to move in the forward direction if the low lift operating unit 30 moves in the forward direction. In addition, the integrally formed second cam portion 60 is pushed by the interlock unit 70 according to the interlock unit 70 is moved in the forward direction. Thus, the second cam portion 60 is moved in the forward direction.
The interlock unit 70 is operated to move in the reverse direction if the high lift operating unit 50 moves in the reverse direction. In addition, the integrally formed first cam portion 40 is pushed by the interlock unit 70 according to the interlock unit 70 is moved in the reverse direction. Thus, the first cam portion 40 is moved in the reverse direction.
The pin operating unit 20 is provided for moving the interlock unit 70 along an axial direction of the camshaft 100. In addition, the pin operating unit 20 includes a housing 21, a hinge unit 22, a first pin 24, a second pin 25, and a pin fixing unit 27.
The housing 21 is a body of the pin operating unit 20 that the hinge unit 22, the first pin 24, the second pin 25, and the pin fixing unit 27 are mounted thereat.
The hinge unit 22 is adapted to perform hinge motion around a hinge shaft 23 mounted to the housing 21.
The first pin 24 and second pin 25 may be formed in a bar shape which is extended along one direction.
The first pin 24 is pushed by the hinge unit 22 according to the hinge motion of the hinge unit 22 such that the first pin 24 moves toward a direction to be protruded from the housing 21. In addition, the hinge unit 22 is pushed by the first pin 24 according to the first pin 24 is to be positioned at its original position such that the hinge unit 22 performs the opposite hinge motion. Further, the second pin 24 is pushed by the hinge unit 22 according to the hinge unit 22 performs the opposite hinge motion such that the second pin 25 moves toward a direction to be protruded from the housing 21. That is, the pin operating unit 20 is operated to interlock the first and second pins 24 and 25 with each other such that if when one of the first pin 24 and the second pin 25 is to be positioned at original position to be not protruded from the housing 21, the other of the first pin 24 and the second pin 25 is to be protruded from the housing 21.
The pin fixing unit 27 is provided for fixing the pin positioned at original position of the first and second pin 24 and 25. A hooking groove 29 is formed at the first and second pin 24 and 25 for hooking the pin fixing unit 27 on the state that the first pin 24 or second pin 25 is positioned at original position, and the pin fixing unit 27 performs reciprocating motion between the first pin 24 and the second pin 25 such that a part of the pin fixing unit 27 is seated at the hooking groove 29 for fixing the pin positioned at original position of the first pin 24 and the second pin 25.
The pin fixing unit 27 is operated by a spring 28. In addition, the pin fixing unit 27 is seated at the hooking groove 29 formed at the one of the first and second pins 24 and 25 by relatively small force generated by pushing of the spring 28 and is escaped from the hooking groove 29 by relatively strong force generated by operation of the first and second pins 24 and 25. The hooking groove 29 and the part of pin fixing unit 27 contacted with the hooking groove 29 may be formed in a gradually curved surface such that the operation is easily performed.
FIG. 2 is a developed diagram of operating units and an interlock unit according to an exemplary embodiment of the present invention.
As shown in FIG. 2, the low lift operating unit 30, the high lift operating unit 50, and the interlock unit 70 include the guide rail 32, 52, and 72.
The guide rail 72 of the interlock unit 70 is formed to be contacted with the first pin 24 or the second pin 25 protruded from the housing 21 by the operation of the pin fixing unit 27 and guide motion of the interlock unit 70. That is, when the camshaft 100 rotates on the state that the first pin 24 or second pin 25 is inserted into the guide rail 72 of the interlock unit 70, the interlock unit 70 is moved along an axial direction of the camshaft 100 according to the guide rail 72 guides relative movement of the first pin 24 or second pin 25 with the rotation of the interlock unit 70 that the first pin 24 or second pin 25 is moved along an exterior circumference of the interlock unit 70.
The low lift solenoid 12 includes a connecting pin 16 protruded by a bar shape, and the connecting pin 16 is contacted with the guide rail 32 of the low lift operating unit 30 according the operation of the low lift solenoid 12. In addition, the guide rail 32 of the low lift operating unit 30 is formed to contact with the connecting pin 16 and guide the motion of the low lift operating unit 30. That is, when the camshaft 100 rotates on the state that the connecting pin 16 is inserted into the guide rail 32 of the low lift operating unit 30, the low lift operating unit 30 is moved in the forward direction along an axial direction of the camshaft 100 according to the guide rail 32 guides relative movement of the connecting pin 16 with the rotation of the low lift operating unit 30 that the connecting pin 16 is moved along an exterior circumference of the low lift operating unit 30.
The high lift solenoid 14 includes a connecting pin 18 protruded by a bar shape, and the connecting pin 18 is contacted with the guide rail 52 of the high lift operating unit 50 according to the operation of the high lift solenoid 14. In addition, the guide rail 52 of the high lift operating unit 50 is formed to contact with the connecting pin 18 and guide the motion of the high lift operating unit 50. That is, when the camshaft 100 rotates on the state that the connecting pin 18 is inserted into the guide rail 52 of the high lift operating unit 50, the high lift operating unit 50 is moved in the reverse direction along an axial direction of the camshaft 100 according to the guide rail 52 guides relative movement of the connecting pin 18 with the rotation of the high lift operating unit 50 that the connecting pin 18 is moved along an exterior circumference of the high lift operating unit 50.
The guide rails 32, 52, and 72 may be formed in a groove shape recessed from the exterior circumferences of the operating units 30 and 50 and the interlock unit 70. In addition, the groove shape guide rails 32, 52, and 72 are longitudinally formed along a circumferential direction of the operating units 30 and 50 and the interlock unit 70.
The guide rails 32, 52, and 72 respectively include an engaging section 34, 54, and 74, a moving section 36, 56, and 76, and an escaping section 38, 58, and 78.
The engaging sections 34, 54, and 74 are the section to be started contacting with the connecting pins 16 and 18 and the first and second pins 24 and 25. In addition, the engaging sections 34, 54, and 74 are respectively extended in vertical to an axial direction of the camshaft 100 along external circumferences of the low lift operating unit 30, the high lift operating unit 50, and the interlock unit 70.
The moving sections 36, 56, and 76 are the section which are formed to guide motions of the low lift operating unit 30, the high lift operating unit 50, and the interlock unit 70 along an axial direction of the camshaft 100 by the connecting pins 16 and 18 and the first and second pins 24 and 25 which are contacted in the engaging section 34, 54, and 74. In addition, the moving sections 36, 56, and 76 are formed in a shape sloping by a set slope with reference to an axial direction of the camshaft 100, and are respectively extended from the engaging sections 34, 54, and 74 along external circumferences of the low lift operating unit 30, the high lift operating unit 50 and the interlock unit 70.
The escaping section 38, 58, and 78 are formed such that the connecting pins 16 and 18 and the first and second pins 24 and 25 are escaped from the guide rails 32, 52, and 72. That is, the escaping sections 38, 58, and 78 are the section to be finished contacting with the connecting pins 16 and 18 and the first and second 24 and 25. In addition, the escaping sections 38, 58, and 78 are respectively extended from the moving sections 36, 56, and 76 in vertical to an axial direction of the camshaft 100 along external circumferences of the low lift operating unit 30, the high lift operating unit 50, and the interlock unit 70.
In FIG. 2, it is shown that the reference lines are determined with reference to 0 degree line, 180 degrees line, and 360 degrees line in external circumferences of the low lift operating unit 30, the high lift operating unit 50, and the interlock unit 70, and developed diagrams of the external circumferences of the low lift operating unit 30, the high lift operating unit 50 and the interlock unit 70 are shown such that the shapes of the guide rails 32, 52, and 72 formed from 0 degree line to 360 degrees line are respectively represented on visible one face. In addition, the predetermined 0 degree line, 180 degrees line, and 360 degrees line are represented by imaginary lines. Herein, 0 degree line and 360 degrees line are a same line in the not developed the low lift operating unit 30, the high lift operating unit 50 and the interlock unit 70. Meanwhile, the engaging sections 34, 54, and 74 are illustrated as one point chain lines, and the moving sections 36, 56, and 76 are illustrated as two point chain lines, and the escaping sections 38, 58, and 78 are illustrated as dotted lines.
The engaging section 34 of the low lift operating unit 30 is extended from 0 degree line to 180 degrees line. In addition, the moving section 36 of the low lift operating unit 30 meets with the engaging section 34 on 180 degrees line, and is extended to slope toward the reverse direction from 180 degrees line to 360 degrees line. Further, the escaping section 38 of the low lift operating unit 30 meets with the moving section 36 on 0 degree line (same to 360 degrees line), and is extended from 0 degree line to 180 degrees line. Herein, it is for moving the low lift operating unit 30 in the forward direction by the rotation of the camshaft 100 that the moving section 36 is sloped toward the reverse direction.
The engaging section 54 of the high lift operating unit 50 extends from 180 degrees line to 360 degrees line. In addition, the moving section 56 of the high lift operating unit 50 meets with the engaging section 54 on 0 degree line (same to 360 degrees line), and extended to slope toward the forward direction from 0 degree line to 180 degrees line. Further, the escaping section 58 of the high lift operating unit 50 meets with the moving section 56 on 180 degrees line, and is extended from 180 degrees line to 360 degrees line. Herein, it is for moving the high lift operating unit 50 in the reverse direction by the rotation of the camshaft 100 that the moving section 56 is sloped toward the forward direction.
The engaging section 74 of the interlock unit 70 is formed at the center of the axial direction in the external circumference of the interlock unit 70. In addition, the moving section 76 of the interlock unit 70 includes one moving section 76a formed at a side of the reverse direction and the other moving section 76b formed at a side of the forward direction with reference to the engaging section 74. Herein, it is for selectively moving the interlock unit 70 toward the forward direction or the reverse direction by the rotation of the camshaft 100 that the moving sections 76 of the interlock unit 70 are two in number. Further, the escaping sections 78 of the interlock unit 70 are formed as two in number according to the moving section 76 of the interlock unit 70 are formed as two in number.
The engaging section 74 of the interlock unit 70 is extended from 0 degree line to 180 degrees line along the center of the axial direction on the external circumference of the interlock unit 70. In addition, the one moving section 76a of the interlock unit 70 is branched from the engaging section 74 on 180 degrees line, and is extended to slope toward the reverse direction from 180 degrees line to 360 degrees line (same to 0 degree line), and is further extended to slope toward the reverse direction from 0 degree line (same to 360 degrees line) to 180 degrees line. Further, one escaping section 78a of the interlock unit 70 meets with the one moving section 76a on 180 degrees line, and is extended from 180 degrees line to 360 degrees line.
Meanwhile, the other moving section 76b of the interlock unit 70 is branched from the engaging section 74 on 0 degree line (same to 360 degrees line), and is extended to slope toward the forward direction from 0 degree line to 360 degrees line. In addition, the other escaping section 78b of the interlock unit 70 meets with the other moving section 76b on 0 degree line (same to 360 degrees line), and is extended from 0 degree line to 180 degrees line.
Herein, the one moving section 76a sloped toward the reverse direction guides the motion of the interlock unit 70 such that the interlock unit 70 is moved toward the forward direction by the rotation of the camshaft 100, and the other moving section 76b sloped toward the forward direction guides the motion of the interlock unit 70 such that the interlock unit 70 is moved toward the reverse direction by the rotation of the camshaft 100.
FIG. 3 is a cross-sectional view of an operating unit and an interlock unit according to an exemplary embodiment of the present invention.
As shown in FIG. 3, the escaping sections 38, 58, and 78 of the guide rail 32, 52, and 72 are adapted that the depth of the groove recessed from the exterior circumferences of the operating unit 30 and 50 and the interlock unit 70 is to be becoming gradually shorter from the points respectively meeting with the moving sections 36, 56, and 76 toward the extending direction. That is, the depth of the groove is to be becoming gradually shorter until the surfaces of the escaping sections 38, 58, and 78 contacted with the connecting pin 16 and 18 and the first and second pins 24 and 25 are reached to the exterior circumferences of the operating unit 30 and 50 and the interlock unit 70. Therefore, the connecting pin 16 and 18 and the first and second pins 24 and 25 are smoothly escaped from the guide rails 32, 52, and 72.
Meanwhile, the cam portions 40 and 60 disposed at the each cylinder may be adapted that the timing for operating the valve is different to each other, and the angles for forming the cams 41, 42, 48, 49, 61, 62, 68, and 69 are respectively different. Therefore, the successive motions toward the forward direction of the first cam portion 40, the interlock unit 70 and the second cam portion 60 are started according to the connecting pin 16 of low lift solenoid 12 is inserted into the guide rail 32 of the low lift operating unit 30 with reference to the valve timing of the cylinder which at the first cam portion 40 is disposed.
As described above, the first cam portion 40, the interlock unit 70, and the second cam portion 60 are sequentially moved in the forward direction. The successive motion is for minimizing interference between the cam portion 40 and 60 and the valve according to the change of the valve lift is performed by on the state that the cam base is contacted with the valve.
The low lift operating unit 30 and the first cam portion 40 is integrally moved toward the forward direction when the connecting pin 16 is moved along the guide rail 32 by the rotation of the low lift operating unit 30. In addition, the first cam portion 40 moves in the forward direction and pushes the interlock unit 70 as a set distance toward the forward direction. Herein, the set distance that the interlock unit 70 is pushed is a distance to engage the first pin 24 of the pin operating unit 20 from the engaging section 74 of the guide rail 72 to the one moving section 76a. 
If the first pin 24 is moved along the one moving section 76a of the guide rail 72 by the rotation of the interlock unit 70 after the first pin 24 is engaged to the one moving section 76a, the interlock unit 70 is moved toward the forward direction.
The interlock unit 70 is contacted with the second cam portion 60 by the motion of the interlock unit 70 toward the forward direction after engaging the first pin 24 to the one moving section 76a, and pushes the second cam portion 60 toward the forward direction such that the second cam portion 60 is moved in the forward direction.
Meanwhile, at least one of gap between the first cam portion 40 and the interlock unit 70 and between the second cam portion 60 and the interlock unit 70 is to be always disposed apart from each other. The disposing apart is for sequentially moving the first cam portion 40, the interlock unit 70, and the second cam portion 60 according to the interlock unit 70 is moved between the first cam portion 40 and the second cam portion 60. In addition, the timings for changing the valve lifts of the cylinder which at the first cam portion 40 is disposed and the cylinder which at the second cam portion 60 is disposed are determined according to the disposing apart and the shape of the guide rails 32, 52, and 72. Further, the distance, that the interlock unit 70 moves along an axial direction, determined by the shape of the guide rail 72 is longer than the distance, that the low lift operating unit 30 moves along an axial direction, determined by the shape of the guide rail 32.
The successive motions toward the reverse direction of the second cam portion 60, the interlock unit 70, and the first cam portion 40 are started according to the connecting pin 18 of the high lift solenoid 14 is inserted into the guide rail 52 of the high lift operating unit 50 with reference to the valve timing of the cylinder which at the second cam portion 60 is disposed, on the contrary to the successive motions toward the forward direction of the first cam portion 40, the interlock unit 70, and the second cam portion 60.
As described above, the second cam portion 60, the interlock unit 70, and the first cam portion 40 are sequentially moved in the reverse direction. The successive motion is for minimizing interference between the cam portion 40 and 60 and the valve according to the change of the valve lift is performed by on the state that the cam base is contacted with the valve.
The high lift operating unit 50 and the second cam portion 60 is integrally moved toward the reverse direction when the connecting pin 18 is moved along the guide rail 52 by the rotation of the high lift operating unit 50. In addition, the second cam portion 60 moves in the reverse direction and pushes the interlock unit 70 as a set distance toward the reverse direction. Herein, the set distance that the interlock unit 70 is pushed is a distance to engage the second pin 25 of the pin operating unit 20 from the engaging section 74 of the guide rail 72 to the other moving section 76b. 
If the second pin 25 is moved along the other moving section 76b of the guide rail 72 by the rotation of the interlock unit 70 after the second pin 25 is engaged to the other moving section 76b, the interlock unit 70 is moved toward the reverse direction.
The interlock unit 70 is contacted with the first cam portion 40 by the motion of the interlock unit 70 toward the reverse direction after engaging the second pin 25 to the other moving section 76b, and pushes the first cam portion 40 toward the reverse direction such that the first cam portion 40 is moved in the reverse direction.
Meanwhile, the distance, that the interlock unit 70 moves along an axial direction, determined by the shape of the guide rail 72 is longer than the distance, that the high lift operating unit 50 moves along an axial direction, determined by the shape of the guide rail 52.
The multiple variable valve lift apparatus 1 may be applied to an in-line four or more than four cylinder engine for operating valves respectively disposed at cylinders by equal to or more than four according to constituent elements such as the first, second, and third cam portions 40, 60, and 80 and the interlock unit 70 are further disposed thereat by the same type.
The multiple variable valve lift apparatus 1 applied to an in-line four or more than four cylinder engine is operated by only the two solenoids 12 and 14 too. In addition, the operation of the multiple variable valve lift apparatus 1 is started by the motion along axial direction of the one cam portion, and is performed according to the interlock units 70 and the cam portions are sequentially and alternately moved toward one direction.
According to an exemplary embodiment of the present invention described referring to FIG. 1 to FIG. 3, the composition can be simple and the operations can be simultaneously efficient by the pin operating unit 20 and the interlock unit 70 moving along axial direction of the camshaft 100 by the operation of the pin operating unit 20. In addition, interference between constituent elements can prevented as the cam portions 40, 60, and 80 disposed at each cylinder are operated step by step by the interlock unit 70. Furthermore, spatial utility can be improved and cost can be simultaneously reduced as a number of the solenoids 10 are to be minimized.
Hereinafter, a shape of a guide rail according to an exemplary embodiment of the present invention will be described in detail referring to FIG. 2, FIG. 4, and FIG. 5.
FIG. 4 is a drawing showing a pin inserted into a guide rail according to an exemplary embodiment of the present invention, and FIG. 5 is a graph representing a shape of a guide rail according to an exemplary embodiment of the present invention by an inclination with reference to rotated angles.
It is not limited that a shape of a guide rail according to an exemplary embodiment of the present invention is applied to the multiple variable valve lift apparatus 1, and the shape of the guide rail can be applied to the all multiple variable valve lift apparatus that the guide rail 32, 52, and 72 having the moving section 36, 56, and 76 is formed thereat so as to guide a pin 16, 18, 24, and 25.
As shown in FIG. 2 and FIG. 4, the width of the pin 16, 18, 24, and 25 is formed to be shorter than the width of the guide rail 32, 52, and 72 such that the pin 16, 18, 24, and 25 is easily inserted into the engaging section 34, 54, and 74. Therefore, a set gap is formed between the pin 16, 18, 24, and 25 inserted into the engaging section 34, 54, and 74 of the guide rail 32, 52, and 72 and the side surface of the guide rail 32, 52, and 72. In addition, the pin 16, 18, 24, and 25 is engaged to the moving section 36, 56, and 76, and the pin 16, 18, 24, and 25 is contacted with the side surface of the moving section 36, 56, and 76 according to the camshaft 100 rotates on the state that the pin 16, 18, 24, and 25 is disposed apart from the side surface of the engaging section 34, 54, and 74. Further, impact may occur at the moment that the pin 16, 18, 24, and 25 and the moving section 36, 56, and 76 are contacted with each other.
In FIG. 5, the moving section 36 of the guide rail 32 formed at the low lift operating unit 30 so as to prevent the generation of the impact is shown by a graph. Herein, the horizontal axis of the graph indicates rotated angles of the camshaft 100 and the operating unit 30, and the vertical axis of the graph indicates phases of the moving section 36 in an axial direction of the camshaft 100. In addition, the phase the moving section 36 in an axial direction of the camshaft 100 is may be a phase with reference with the central line or the side surface of the moving section 36.
Even though the moving section 36 of the low lift operating unit 30 is representatively described in description referring to FIG. 5, the shape of the moving section 36 can be applied to the moving sections 56 and 76 of the other constituent elements changing the valve lift.
As shown in FIG. 5, the moving section 36 includes a gap reducing section 36a, a contact maintaining section 36b, an accelerating section 36c, and a decelerating section 36d. 
The gap reducing section 36a, the contact maintaining section 36b, the accelerating section 36c, and the decelerating section 36d are sequentially formed along 180 degrees forming the moving section 36.
The gap reducing section 36a is formed in a gradually curved surface, and is adapted that the phase thereof is changed as the width of the gap along an axial direction from the starting point of the moving section 36 that the ending point of the engaging section 34 and the moving section 36 meet with each other to a predetermined point of the moving section 36. In addition, the curved surface of the gap reducing section 36a is formed in a deceleration graph, that a slope is gradually decreased, in the graph representing the shape of the moving section 36 by the inclination with reference to the rotated angles.
The contact maintaining section 36b is adapted that the phase thereof is equally maintained along an axial direction from the ending point of the gap reducing section 36a to a predetermined point of the moving section 36. That is, the contact maintaining section 36b is formed in a constant velocity graph, that a slope is 0, in the graph representing the shape of the moving section 36 by the inclination with reference to the rotated angles. Therefore, the connecting pin 16 is contacted with the side surface of the moving section 36 on a point which is the ending point of the gap reducing section 36a and is simultaneously the contact maintaining section 36b, and is slid along the contact maintaining section 36b on the state of contacting with the side surface of the moving section 36 so as to engage to the moving section 36 of the guide rail 32 without the impact.
The accelerating section 36c and the decelerating section 36d are formed for substantially moving the operating unit 30 by the pin 16. That is, the accelerating section 36c and the decelerating section 36d is a pin moving section 36c and 36d which substantially guides relative movement of the pin 16.
The accelerating section 36c is formed in a gradually curved surface, and is adapted that the phase thereof along an axial direction from the ending point of the contact maintaining section 36b to the predetermined point of the moving section 36. In addition, the curved surface of the accelerating section 36c is formed in an acceleration graph, that a slope is gradually increased, in the graph representing the shape of the moving section 36 by the inclination with reference to the rotated angles. Further, the connecting pin 16 is smoothly slid along the accelerating section 36c as the curved surface of the accelerating section 36c is formed in an acceleration graph.
The decelerating section 36d is formed in a gradually curved surface, and is adapted that the phase thereof is changed along an axial direction from the ending point of the accelerating section 36c to the predetermined point of the moving section 36. In addition, the curved surface of the decelerating section 36d is formed in a deceleration graph, that a slope is decreased, in the graph representing the shape of the moving section 36 by the inclination with reference to the rotated angles. Further, a slope becomes to 0 or to close 0 on a point that the decelerating section 36d is finished and the moving section 36 meets with the escaping section 38 in the graph representing the shape of the moving section 36 by the inclination with reference to the rotated angles. That is, the slope is converged to zero on the point that the decelerating section 36d is finished. Therefore, the connecting pin 16 is engaged to the escaping section 38 of the guide rail 32 without the impact.
While it is shown that the moving section 36 is formed along the 180 degrees rotated angle in FIG. 5, it is not limited thereto, and the shape having the gap reducing section 36a, contact maintaining section 36b, accelerating section 36c and decelerating section 36d can be applied to moving sections 36, 56, and 76 formed along a rotated angle which is larger than 180 degrees by the same type according to a design of a person of an ordinary skill in the art.
According to an exemplary embodiment of the present invention, noise can be minimized and stability of changing valve lift can be ensured as the impact is prevented when the guide rail 32, 52, and 72 contacts to the pin 16, 18, 24, and 25.
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.

## Claims

1. A multiple variable valve lift apparatus, comprising:
a camshaft rotating by drive of an engine;
at least two cam portions disposed on an exterior circumference of the camshaft to be slidably movable along an axial direction of the camshaft and to be rotated together with the camshaft, and forming a high cam and a low cam;
a valve opening/closing unit operated by one of the high cam or the low cam formed at the at least two cam portions;
at least two operating units slidably disposed to move along the axial direction on an exterior circumference of the camshaft so as to move the at least two cam portions along the axial direction of the camshaft;
a control portion selectively moving the at least two operating units along the axial direction of the camshaft;
a pin disposed at the control portion; and
a guide rail formed in a groove shape on an exterior circumference of the at least two operating units such that the pin is inserted therein and guiding relative movement of the pin according to rotation of the camshaft and the at least two operating units such that the at least two operating units are moved along the axial direction of the camshaft by the pin,
wherein the at least two operating units are moved as the pin of the control portion is inserted into the guide rail of the at least two operating units, and the guide rail is formed in a shape combined a straight line with a curved line along the exterior circumference of the at least two operating units for preventing impact generated by contacting with the pin,
wherein the guide rail comprising a moving section, and the moving section comprising:
a gap reducing section formed in a gradually curved surface and adapted that a phase thereof is changed as the width of the gap along an axial direction from a starting point to a predetermined point of the moving section;
a contact maintaining section formed that the phase thereof is equally maintained along an axial direction from an ending point of the gap reducing section to a predetermined point of the moving section; and
a pin moving section formed from an ending point of the contact maintaining section to an ending point of the moving section, and guiding relative movement of the pin with the at least two operating units along the axial direction of the camshaft such that the at least two operating units are moved by the pin.

2. The apparatus of claim 1, wherein the guide rail comprising:
an escaping section starting contact with the pin;
a moving section guiding that the at least two operating units are moved along the axial direction of the camshaft by the pin; and
an escaping section formed to escape the pin,
wherein the width of the pin is formed to be shorter than the width of the guide rail, and a gap is formed between the pin inserted into the guide rail and a side surface of the guide rail.

3. The apparatus of claim 2, wherein the escaping section of the guide rail is formed such that a depth of the groove is gradually reduced from a point meeting with the moving section toward an extending direction.

4. The apparatus of claim 1, wherein in case that a shape of the moving section is represented by a graph having a horizontal axis indicating rotated angles of the camshaft and the at least two operating units and a vertical axis indicating phases of the moving section in the axial direction of the camshaft,
the gap reducing section is formed in a curved line having a shape that slope of the graph is gradually decreased.

5. The apparatus of claim 4, wherein the contact maintaining section is formed in a straight line such that slope of the graph is 0.

6. The apparatus of claim 4, wherein the pin moving section includes:
an accelerating section extended from the ending point of the contact maintaining section; and
a decelerating section extended from an ending point of the accelerating section to the ending point of the moving section,
wherein the accelerating section is formed in a curved line such that slope of the graph is gradually increased, and
wherein the decelerating section is formed in a curved line such that slope of the graph is gradually decreased.

7. The apparatus of claim 6, wherein slope of the graph is converged to 0 over finishing the decelerating section.