Abstract:
A slide type continuous variable valve lift (CVVL) device includes a swing arm rotating to press a valve; a cam lobe; a roller transmitting a driving force of the cam lobe to the swing arm; and a guide guiding the roller to move along a predetermined path. The CVVL device generally can minimize the number of places where sliding friction between respective parts may occur to minimize power loss and enable more precise operation control, reduce the number of parts to enhance the overall robustness of the device, and advance the time of maximum valve opening to improve the fuel efficiency of an engine.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims the priority to Korean Patent Application No. 10-2008-0071695 filed Jul. 23, 2008, the entire contents of which application is incorporated herein for all purposes by this reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a slide type continuous variable valve lift device. 
         [0004]    2. Description of Related Art 
         [0005]    As for an engine, a camshaft is rotated by a rotating force transmitted from a crank shaft, and an intake valve and an exhaust valve are reciprocated up and down with regular timing by cams of the camshaft. Thereby, intake air is supplied to a combustion chamber, and combustion gas is exhausted. In this process, a fuel-air mixture is compressed and exploded to generate power. 
         [0006]    At this time, a device that can continuously vary the lift distance of a valve according to an operating speed of the engine is called a continuous variable valve lift (CVVL) device. 
         [0007]    Hereinafter, a conventional CVVL device will be described in detail with reference to the attached drawings. 
         [0008]      FIG. 1  is a schematic view illustrating the configuration of a conventional CVVL device. 
         [0009]    The conventional CVVL device illustrated in  FIG. 1  includes a swing arm  30 , a cam lobe  40 , a frame  50 , a rocker arm  60  and a shaft coupler  70 . The swing arm  30  is connected to a suction valve  10  and a hydraulic tappet  20  at respective opposite ends thereof, and has a swing arm roller  32  in the middle portion thereof. The cam lobe  40  is provided above the swing arm  30 , and the frame  50  is provided to rotate coaxially with the cam lobe  40 . The frame  50  has a cam follower  52  protruding out from one portion thereof, wherein a rounded surface  54  is formed in the inner surface of the cam follower  52 . The rocker arm  60  is hinged to one portion of the swing arm  30  by a coupler  62 , and is provided with a sliding block  66  on the upper end thereof which slides along the rounded surface  54  of the frame  50 . The shaft coupler  70  is configured to rotate the frame  50 . 
         [0010]    A rocker roller  64  is provided on the upper portion of the rocker arm  60 , in contact with the outer circumference of the cam lobe  40 , and the rocker arm  60  is configured to rotate around the coupler  62  in response to the rotation of the cam lobe  40 . 
         [0011]    With the above-described configuration, when the cam lobe  40  rotates counterclockwise at the position shown in  FIG. 1  so that the tip of the protrusion of the cam lobe  40  comes into contact with the rocker roller  64 , the rocker arm  60  rotates clockwise around the coupler  62 . 
         [0012]    In this case, the center of curvature of the rounded surface  54  is located above the center of rotation of the frame  50 . Thus, when the sliding block  66  provided in the upper end of the rocker arm  60  is pulled to the right, the frame  50  rotates in a clockwise direction. As a result, the sliding block  66  comes into contact with the upper portion of the rounded surface  54 . 
         [0013]    A drive cam  56  is formed in a portion of the frame  50 , which comes into contact with the swing arm roller  32 . When the frame  50  rotates clockwise at the position shown in  FIG. 1 , the swing arm  30  is pressed downwards by the drive cam  56  so as to rotate counterclockwise around the end portion connected to the hydraulic tappet  20 . Then, the suction valve  10  is moved downwards thereby opening a channel to feed fuel into a cylinder. 
         [0014]    Further, when the shaft coupler  70  rotates counterclockwise from the position shown in  FIG. 1  thereby causing the frame  50  to rotate clockwise. The sliding block  66  also comes into contact with an upper portion of the rounded surface  54 , which is higher than the position shown in  FIG. 1 . Further, the drive cam  56  is closer to the swing arm  32  than in the position shown in  FIG. 1 . When the cam lobe  40  rotates from this position to further rotate the frame  50  in a clockwise direction, the drive cam  56  further rotates the swing arm  30  to further increase the lift distance of the suction valve  10 . 
         [0015]    In other words, the conventional CVVL device shown in  FIG. 1  can adjust the lift distance of the suction valve  10  by changing the angle of rotation of the frame  50  before the rocker arm  60  is rotated by the rotation of the cam lobe  40 . 
         [0016]    However, in the conventional CVVL device described as above, when the swing arm rotates following the rotation of the cam lobe, sliding friction may occurs in at least five places including the contacts between the cam lobe and the frame, between the cam lobe and the rocker roller, between the sliding block and the rounded surface, between the drive cam and the swing arm roller and between the swing arm roller and the swing arm. A large amount of power is lost by friction, and thus precise operation control becomes difficult. 
         [0017]    Other problems include increasing the number of springs, which apply an elastic force to respective parts in order to constantly maintain the coupling positions of the respective parts, and increasing loss of friction of the respective parts 
         [0018]    Furthermore, the friction loss of the respective parts is increased greatly due to the increased number of springs, which apply an elastic force to respective parts to constantly maintain the coupling positions of the respective parts. 
         [0019]    Moreover, since the conventional CVVL device is made up of a large number of parts, it is difficult to fabricate the device, manufacturing costs are increased, and the overall robustness of the device becomes lower. 
         [0020]    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 
       [0021]    Various embodiments of the present invention provide a slide type continuous variable valve lift (CVVL) device that may minimize the number of places where sliding friction between respective parts may occur so as to minimize power loss and enable more precise operation control as well as reduce the number of parts so as to enhance the overall robustness of the device. 
         [0022]    In various aspects of the present invention, the slide type CVVL device may include a swing arm rotating to press a valve, a cam lobe, a roller transmitting a driving force of the cam lobe to the swing arm, and/or a guide guiding the roller to move along a predetermined guide path. 
         [0023]    The guide may selectively guide the roller to move along both a first path and a second path or only the second path. The roller may intermittently presses the swing arm on the first path but the roller may not press the swing arm on the second path. The cam lobe may be placed above the swing arm. The guide may include a first guide surface extending away from an upper surface of the swing arm to define the first path thereon and a second guide surface extending from a distal end of the first guide surface to the cam lobe to define the second path thereon. The roller may be configured to move in contact with the first guide surface or the second guide surface. The guide may be constructed in such a manner that the first guide surface or the second guide surface comes into contact with the roller according to a rotation angle of the guide. 
         [0024]    The guide may be configured to select a path of the roller based on a rotation angle of the guide. 
         [0025]    The slide type continuous variable valve lift device may further include a guide control member along which the guide guides the roller. The guide control member may comprise an eccentric cam which rotates the guide. 
         [0026]    The guide may be configured to rotate around a rotating shaft which is placed on a predetermined point lower than an upper surface of the swing arm. 
         [0027]    The roller may include a substantially cylindrical cam lobe contact and substantially cylindrical swing arm contacts. The swing arm contacts may have a diameter smaller than that of the cylindrical cam lobe contact. The cylindrical swing arm contacts may be provided on opposite ends of the cam lobe contact, respectively. The swing arm may have a through hole, which allows the camp lobe contact to move thereinto. The swing arm may be configured to receive the camp lobe contact. 
         [0028]    Various aspects of the present invention are directed to a slide type continuous variable valve lift device may including a swing arm pivotally coupled to a rotating shaft to press a valve, a cam lobe displaced above the swing arm and opposite the rotating shaft of the swing arm, a roller displaced between the swing arm and the cam robe and transmitting a driving force of the cam lobe to the swing arm, a guide coupling the roller and the swing arm and guiding the roller to move along a predetermined path so as to change a distance between the roller and the valve, and/or a guide control member regulating operation of the guide. 
         [0029]    The guide control member may control the guide to selectively move the rotation center of the roller to follow both a first path and a second path of the predetermined path or only the second path of the predetermined path. The roller may intermittently presses the swing arm on the first path but does not press the swing arm on the second path. 
         [0030]    The guide may include a rotating shaft, a first guide surface extending away substantially in a radial direction from the rotating shaft of the guide to define the first path and a second guide surface extending from a distal end of the first guide surface toward the cam lobe substantially in a circumferential direction to define the second path. 
         [0031]    The guide may be configured to select a path of the roller along the predetermined path based on a rotation angle with respect to the rotating shaft of the guide. 
         [0032]    The rotating shaft of the guide may be placed or positioned lower than an upper surface of the swing arm. The swing arm may comprise a receiving portion formed at a lower surface thereof to retain the rotating shaft of the guide. 
         [0033]    The guide control member may comprise an eccentric cam engaged with the guide and configured to regulate a rotation angle of the guide. 
         [0034]    The slide type continuous variable valve lift device may further comprise an elastic member configured to press the roller toward the cam lobe and press the guide toward the guide control member at the same time. 
         [0035]    According to various embodiments of the present invention, the CVVL device can reduce the number of places where sliding friction between respective parts may occur to minimize power loss and enable more precise operation control, reduce the number of parts so as to enhance the overall robustness of the device, and advance the time of maximum valve opening so as to improve the fuel efficiency of an engine. 
         [0036]    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 
         [0037]      FIG. 1  is a side elevational view illustrating a continuous variable valve lift (CVVL) device of the related art. 
           [0038]      FIG. 2  is a perspective view illustrating an exemplary slide type CVVL device according to the present invention. 
           [0039]      FIG. 3  is a side elevational view illustrating the slide type CVVL device of  FIG. 2 . 
           [0040]      FIG. 4  is a perspective view illustrating a swing arm of the device of  FIG. 2 . 
           [0041]      FIG. 5  is a perspective view illustrating a roller of the device of  FIG. 2 . 
           [0042]      FIG. 6  is a perspective view illustrating a guide of the device of  FIG. 2 . 
           [0043]      FIGS. 7 and 8  are perspective views illustrating an exemplary operation of a low lift of a slide type CVVL device similar to that of  FIG. 2 . 
           [0044]      FIGS. 9 and 10  are perspective views illustrating an exemplary operation of a low lift of a slide type CVVL device similar to that of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0045]    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. 
         [0046]      FIG. 2  is a perspective view illustrating a slide type CVVL device of the present invention.  FIG. 3  is a side elevational view illustrating the slide type CVVL device of the present invention.  FIGS. 4-6  are perspective views illustrating a swing arm, a roller and a guide of the slide type CVVL device of the present invention. 
         [0047]    As shown in  FIGS. 2-6 , the slide type CVVL device of the present invention includes a swing arm  100 , a cam lobe  200 , a roller  300  and a guide  400 . The swing arm  100  is connected to a suction valve  10  and a hydraulic tappet  20  at respective opposite ends thereof. The swing arm has a rotating shaft  120  formed in a portion thereof connected to the hydraulic tappet  20 . 
         [0048]    The swing arm  100  is configured to rotate around the rotating shaft  120  so as to press the suction valve  10 . The cam lobe  200  is positioned above the swing arm  100  (e.g. as shown in the upper left part of  FIG. 3 ) to translate or convert the rotation of a camshaft into linear motion. The roller  300  continues to be in contact with the outer circumference of the cam lobe  200 . By moving toward the swing arm  100  by the rotation of the cam lobe  200 , the roller also presses the swing arm  100 . The guide  400  guides the movement of the roller  300 . Thus, the roller may transmit movement of the cam lobe to the swing arm. The roller may also translate the movement of the cam lobe to movement of the swing arm in a different direction. Herein, the cam lobe  200  and an eccentric cam  500  are not shown in  FIG. 2 , but a frame  700  is removed from the view of  FIG. 3  to more clearly show the internal construction of the slide type CVVL device of the present invention. 
         [0049]    In various embodiments, the slide type CVVL device includes a spring  600  which elastically presses the roller  300  against the cam lobe  200  so the roller  300  can continue to be in constant contact with the cam lobe  200 . 
         [0050]    The guide  400  is configured to selectively guide the movement of the roller  300  in such a manner that the roller  300  can move along both a first path and a second path of the guide path predetermined by the guide. Alternatively, the guide may select the roller to move along only one of the first path and second path of the guide. The roller  300  intermittently presses the swing arm  100  on the first path, whereas the roller  300  does not press the swing arm  100  on the second path. The guide  400  has a first guide surface  410  extending away from the upper surface of the swing arm  100  (in the first path direction) and a second guide surface  420  extending from the distal end of the first guide surface  410  toward the cam lobe  200  (in the second path direction). Accordingly, in various embodiments, the path is predetermined by the shape and configuration of the first and second guide surfaces. Further, the guide may be configured to guide the roller  300  along both the first and second paths or to guide the roller along only one portion of the first and second paths. Thus, the guide determines whether the predetermined path of the roller includes the first path. 
         [0051]    Further, the roller  300  is configured to be pushed by the cam lobe  200  in response to the rotation of the cam lobe  200  thereby moving into contact with the first or second guide surfaces  410  and  420  respectively. 
         [0052]    Consequently, the roller  300  presses the swing arm  100  to rotate when moving downwards along the first guide surface  410  but not when moving sideways along the second guide surface  420 . The roller  300  does not start to press the swing arm  100  as the cam lobe  200  rotates from the position shown in  FIG. 3 . Rather, the roller  300  will not press the swing arm  100  when moving along the second guide surface  420  or until starting to move downwards along the first guide surface  410 . 
         [0053]    The guide  400  is configured to be rotated around a rotating shaft  430  by the eccentric cam  500  which is placed (on the right part of  FIG. 3 ) opposite the cam lobe  200 . The spring  600  is constructed not only to press the roller  300  toward the cam lobe  200  but also to press the guide  400  toward the eccentric cam  500  so the guide  400  can continue to be in constant contact with the eccentric cam  500 . 
         [0054]    In the position shown in  FIG. 3 , the guide  400  is rotated in a direction moving away from the cam lobe  200  (to the right in  FIG. 3 ) so the roller  300  comes into contact with the second guide surface  420 . When the eccentric cam  500  rotates clockwise from the position shown in  FIG. 3 , the guide  400  rotates in a direction toward the cam lobe  200  (to the left in  FIG. 3 ) so the roller  300  comes into contact with the first guide surface  410 . That is, the first guide surface  410  or the second guide surface  420  of the guide  400  comes into contact with the roller  300  based on the angle of rotation of the guide  400 . 
         [0055]    While the present invention has been described with respect to the eccentric cam  500  as a part for rotating the guide  400  to change the path of the roller  300 , as would be understood by one skilled in the art from the foregoing, the eccentric cam  500  can be replaced by any means capable of rotating or moving the guide  400  so that the path of the roller  300  can be changed. 
         [0056]    The slide type CVVL device of the present invention can further include the frame  700  to which the rotating shaft  120  and the rotating shaft  430  are rotatably coupled. With the frame  700  additionally provided, the relative distance between the rotating shaft  120  and the guide  400  is kept substantially constant even if the rotating shaft  120  is pushed upwards by operation of the hydraulic tappet  20 . In this manner, contact positions of respective parts are kept constant thereby making it possible to more precisely adjust or modify the timing to open. Likewise, the distance to lift the suction valve may also be precisely adjusted. Here, since the spring  600  is wound on a support shaft  610  whose position is fixed, arc holes  710  may be formed in portions of the frame  700  through which the support shaft  610  extends. The center of curvature of the respective arc hole  710  is the same as or positioned at substantially the same point as the center of the rotating shaft  430 . 
         [0057]    In addition, the rotating shaft  430  of the guide  400 , if located at a higher position than the upper surface of the swing arm  100 , may interfere with the roller  300  which is moving downwards. In various embodiments, the rotating shaft  430  of the guide  400  is generally located at a lower point than the upper surface of the swing arm  100  during operation. 
         [0058]    The roller  300  is a part that continues to be in constant contact with the cam lobe  200  and the guide surfaces  410  and  420  and comes into contact with the swing arm  100  to press the swing arm  100 . As shown in  FIG. 5 , the roller  300  includes a cylindrical cam lobe contact  310 . The cylindrical swing arm contacts  320  may have a diameter smaller than that of the cam lobe contact  310 . The swing arm contacts  320  may be provided at opposite ends of the cam lobe contact  310 , respectively. Also, the cylindrical guide surface contacts  330  may have a diameter smaller than that of the swing arm contacts  320 . The guide surface contacts  330  may be provided at outer ends of the swing arm contacts  320  respectively. 
         [0059]    The swing arm  100  is formed with a through hole  110  into which the cam lobe contact  310  can be inserted so the swing arm  100  is not pressed downwards by the cam lobe contact  310 . 
         [0060]    With this construction in which part of the lower portion of the cam lobe contact  310  can be inserted into the through hole  110 , the roller  300  can stably press the swing arm  100  without being separated from the swing arm  100  even if for example an external force or vibration is applied. 
         [0061]      FIGS. 7 and 8  are perspective views illustrating operation of a low lift of the slide type CVVL device according to various embodiments of the present invention. 
         [0062]    When the cam lobe  200  rotates clockwise from the position shown in  FIG. 3 , as shown in  FIG. 7 , the tip of the protrusion of the cam lobe  200  approaches the roller  300  and thus the roller  300  is pushed to the right along the second guide surface  420  toward the first guide surface  410 . While the roller  300  moves along the second guide surface  420 , the swing arm  100  is not pressed and thus does not open the suction valve  10 . 
         [0063]    When the cam lobe  200  further rotates clockwise from the position shown in  FIG. 7 , the roller  300  further moves downwards along the first guide surface  410 , thereby pressing the swing arm  100  as shown in  FIG. 8 . The swing arm  100 , when pressed downwards as described above, rotates counterclockwise around the rotating shaft  120  to open the suction valve  10 . 
         [0064]    That is, the operation shown in  FIGS. 7 and 8  is a low lift operation in which the suction valve  10  is not opened as soon as the tip of the protrusion of the cam lobe  200  contacts the roller  300 . Instead, it is opened only after a predetermined time from the time of contact. 
         [0065]      FIGS. 9 and 10  are perspective views illustrating an example of the operation of a high lift of the slide type CVVL device according to various embodiments of the present invention. 
         [0066]    When the eccentric cam  500  rotates clockwise from the position shown in  FIG. 3 , the guide  400  is pushed by the eccentric cam  500  to rotate counterclockwise around the rotating shaft  430 . As shown in  FIG. 9 , the first guide surface  410  comes into contact with the roller  300 . 
         [0067]    In this position where the roller  300  is in contact with the first guide surface  410 , the roller  300  moves downwards as soon as the cam lobe  200  rotates. Thus, the suction valve  10  is opened more quickly than the case shown in  FIGS. 7 and 8 . When the tip of the protrusion of the cam lobe  200  is in contact with the roller  300 , the swing arm  100  rotates more and thus the suction valve  10  is opened more than in the case shown in  FIG. 8 . 
         [0068]    That is, the operation shown in  FIGS. 9 and 10  is a high lift operation in which the suction valve  10  is opened as soon as the tip of the protrusion of the cam lobe  200  comes into contact with the roller  300 . 
         [0069]    As described above, the slide type CVVL device of the present invention can continuously vary the lift distance of the suction valve  10  using a smaller number of parts than the conventional CVVL device shown in  FIG. 1 . 
         [0070]    Accordingly, the slide type CVVL device of the present invention leads to a simpler construction and causes to reduce the number of places where parts are pressed and abraded against each other thereby improving the overall strength of the device. 
         [0071]    Furthermore, the low lift state shown in  FIG. 8  is advanced compared to the high lift state shown in  FIG. 10 . In the low lift state shown in  FIG. 8 , the roller  300  is located opposite to the direction of rotation of the cam lobe  200 . Thus the time to open the suction valve to a greatest or maximum amount is advanced. The slide type CVVL device of the present invention can improve the fuel efficiency of an engine by advancing the time of maximum valve opening within about 20 degrees in the transition from the high lift state to the low lift state. 
         [0072]    For convenience in explanation and accurate definition in the appended claims, the terms “upper” or “lower”, “front” or “rear”, “inside” or “outside”, and etc. are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
         [0073]    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.