Patent Publication Number: US-7210434-B2

Title: Hydraulic cam for variable timing/displacement valve train

Description:
BACKGROUND 
   1. Field 
   The present disclosure generally relates to engine valve control systems, and particularly to valve control systems using variable valve timing and variable displacement. 
   2. Related Art 
   The optimum times for opening and closing the inlet and exhaust valves in an engine vary, inter alia, with engine speed. In any engine having fixed angles for opening and closing of valves during all engine operating conditions, valve timing is an important design consideration. In many cases, valve timing detracts from engine efficiencies in all but a limited range of operating conditions. For this reason, it has been previously proposed to dynamically vary valve timing during engine operation in order to accommodate different operating conditions. 
   Hydraulic camshafts are used to regulate valves in an engine combustion chamber. Valve regulation includes both valve timing and valve displacement inside the engine combustion chamber. Valve timing controls both the opening time and the closing time for valves. Valve displacement comprises the distance (lift) that a valve opens and the duration for which the valve is open. 
   The conventional camshaft-actuated valve gear train is a compromise solution as far as engine efficiency and performance is concerned. For example, at relatively low speeds and loads, the engine valves typically open more than is needed, while at relatively higher engine speeds, the valves typically do not open enough to allow the flow quantity of air-fuel mixture necessary to achieve optimum engine performance. At relatively low speeds, if the amount of valve opening could be reduced, such that the poppet valve could serve as a flow “throttle”, engine pumping losses could be reduced. A poppet valve is an intake or exhaust valve, operated by springs and cams that plugs and unplugs an opening by axial motion. 
   In some engines, variation of valve timing has been proposed as a means for regulating engine output power. For example, if the inlet valve is allowed to remain open for part of a compression stroke, the volumetric efficiency of an engine can be reduced. Such an engine requires an increased control range over the phase of the hydraulic camshaft. Furthermore, the control needs to be continuous over the full adjustment range. 
   It has been observed that improvements to engine efficiency can be achieved by varying the timing of the opening and closing of the valves as a function of engine speed, and also as a function of engine load. One known mechanism used to vary the timing of the opening and closing of the engine valves is a variable cam phase change device. The variable cam phase change device is used to vary the angular position of the camshaft, relative to the angular position of the crankshaft. 
   Various proposals have been suggested for mechanisms used to adjust the camshaft phase angle relative to the crankshaft. However, the suggested mechanisms typically are very complex because of the need to withstand considerable torque fluctuations experienced by a camshaft during normal operation. The camshaft phase angle adjustment mechanism must also supply force sufficient to rotate the camshaft against the resistance provided by the compressed valve springs. 
   Electro-mechanical valve-actuated systems have been proposed that vary either valve timing or valve displacement. However, it is desirable to simultaneously control both valve timing and valve displacement in a hydraulic valve-actuated system. The present teachings disclose a hydraulic system that varies both valve timing and valve displacement in an engine. 
   SUMMARY 
   An improved hydraulic variable valve train apparatus is disclosed. The apparatus is adapted for use in an engine having a combustion chamber, a hydraulic camshaft rotating in timed relationship with a combustion sequence occurring in the combustion chamber, wherein the hydraulic camshaft rotates along a circumferential axis of rotation of the hydraulic camshaft. In one embodiment, the improved hydraulic variable valve train comprises a first graduated cavity disposed on a first portion of a hydraulic camshaft lobe and a second graduated cavity disposed on a second portion of the hydraulic camshaft lobe, wherein the hydraulic camshaft lobe concentrically rotates with the circumferential axis of rotation of the hydraulic camshaft. The improved apparatus has at least one valve operatively coupled to the hydraulic camshaft lobe and a hydraulic circuit adapted to actuate the valve in the engine. The hydraulic circuit comprises a hydraulic fluid source operatively coupled to the hydraulic camshaft lobe via a first inlet portion disposed at a first inlet port on the hydraulic camshaft and a second inlet portion disposed at a second inlet port on the hydraulic camshaft. The hydraulic circuit further comprises a first control port operatively connected to a first control port side of the hydraulic camshaft lobe and a second control port operatively connected to a second control port side of the hydraulic camshaft lobe, a first exhaust port operatively connected to a first exhaust port side of the hydraulic camshaft lobe and a second exhaust port operatively connected to a second exhaust port side of the hydraulic camshaft lobe. 
   An improved hydraulic fluid cam apparatus adapted for use in an engine is also disclosed. The improved hydraulic fluid cam apparatus comprises a first cavity having a first predetermined shape disposed on a hydraulic camshaft lobe, wherein the first predetermined shape has a first width on a first portion of the hydraulic camshaft lobe and a second width, narrower than the first width, on a second portion of the hydraulic camshaft lobe. 
   In another embodiment, an improved variable valve train apparatus; adapted for use in an internal combustion engine having a combustion chamber is disclosed. In this embodiment, the improved variable valve train includes a hydraulic camshaft; rotating in timed relationship with a combustion sequence occurring in the engine combustion chamber, wherein the hydraulic camshaft rotates along a circumferential axis of rotation of the hydraulic camshaft. The apparatus comprises at least a first cavity disposed on a first portion of a hydraulic camshaft lobe, wherein the hydraulic camshaft lobe rotates concentrically with the circumferential axis of rotation of the hydraulic camshaft and has at least one valve operatively coupled to the hydraulic camshaft lobe. 
   In another embodiment, a valve actuation apparatus, adapted for use in a hydraulic fluid cam, is disclosed. The apparatus comprises a hydraulic camshaft lobe having at least a first main cavity having a depth and a width associated therewith. The apparatus further comprises at least one additional cavity having a variable width and a variable depth associated therewith, and at least one additional cavity actuation mechanism associated with the at least one additional cavity, adapted to vary the width and further adapted to vary the depth of the at least one additional cavity. 
   In another embodiment, a valve actuation means, operatively coupled to a hydraulic camshaft lobe for varying poppet valve timing while simultaneously varying poppet valve displacement in a combustion chamber of an engine, is disclosed. The valve actuation means comprises a sliding cavity means operatively connected to the hydraulic camshaft lobe and a sliding cavity actuation means operatively coupled to the sliding cavity means. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the present invention will be more readily understood by reference to the following figures, in which like reference numbers and designations indicate like elements. 
       FIG. 1A  illustrates a cross-sectional view of an improved variable valve train apparatus, in an exhaust position. 
       FIG. 1B  illustrates a cross-sectional view of an improved variable valve train apparatus, in an inlet position. 
       FIGS. 1C–1H  illustrates sectional views, at a reduced scale, illustrating various positions of the variable valve train apparatus during engine operation. 
       FIG. 1I  shows a cross-sectional view of the variable valve train apparatus, illustrating a cam phasing angle θ. 
       FIG. 2  illustrates a relationship between valve displacement and cam angle, showing valve actuation, corresponding to  FIG. 1I . 
     FIG.  3 Ai illustrates a front view of an improved hydraulic fluid cam apparatus in a maximum displacement position. 
     FIG.  3 Aii illustrates a side view of the improved hydraulic fluid cam apparatus of FIG.  3 Ai. 
     FIG.  3 Aiii illustrates a valve displacement diagram corresponding to FIG.  3 Ai and FIG.  3 Aii. 
     FIG.  3 Bi illustrates a front view of the improved hydraulic fluid cam apparatus in a graduated position. 
     FIG.  3 Bii illustrates a side view of the improved hydraulic fluid cam apparatus of FIG.  3 Bi. 
     FIG.  3 Biii illustrates a valve displacement diagram corresponding to FIG.  3 Bi and FIG.  3 Bii. 
     FIG.  3 Ci illustrates a front view of the improved hydraulic fluid cam apparatus in a non-actuated position. 
     FIG.  3 Cii illustrates a side view of the improved hydraulic fluid cam apparatus of FIG.  3 Ci. 
     FIG.  3 Ciii illustrates a valve displacement diagram corresponding to FIG.  2 Ci and FIG.  3 Cii. 
       FIG. 4A  illustrates an alternate embodiment of the present disclosure, in a maximum displacement position. 
       FIG. 4B  illustrates an alternate embodiment of the present disclosure, in a graduated position. 
       FIG. 4C  illustrates an alternate embodiment of the present disclosure, in a non-actuated position. 
       FIG. 5A  illustrates a front view of a hydraulic camshaft lobe having main and additional cavities. 
       FIG. 5B  illustrates a side view of the hydraulic camshaft lobe having main and additional cavities, corresponding to  FIG. 5A . 
       FIG. 5C  illustrates a valve displacement diagram corresponding to the hydraulic camshaft lobe of  FIG. 5A  and  FIG. 5B . 
       FIG. 5D  illustrates a side view of a cam lobe having a main cavity and an additional cavity with a sliding block. 
       FIG. 5E  illustrates a valve displacement diagram corresponding to the camshaft lobe of  FIG. 5D . 
       FIG. 5F  illustrates a side view of another embodiment of a cam lobe having a main cavity and an additional cavity with a sliding block. 
       FIG. 5G  illustrates a valve displacement diagram corresponding to the camshaft lobe of  FIG. 5F . 
   

   DETAILED DESCRIPTION 
   The present disclosure provides for variable valve timing and variable valve displacement control, either separately or simultaneously, in a hydraulic fluid cam. In one embodiment, at least one cavity is disposed on a cam lobe to actuate a valve. In another embodiment, a plurality of cavities are disposed on a cam lobe for valve actuation. In one embodiment, a plurality of main cavities are disposed on a first portion of a cam lobe and at least one additional cavity is disposed on a second portion of the cam lobe. This embodiment includes a sliding apparatus adapted to vary a width and a depth of the additional cavity. 
   The variable valve actuation apparatus of the present disclosure is not limited to any particular configuration or arrangement of the cylinder head. Nor is the variable valve activation apparatus limited to any particular style or configuration of rocker arm assembly. Further, the disclosed variable valve activation apparatus is not limited to a valve gear train which includes a rocker arm assembly. Although some embodiments are described in terms of an internal combustion engine, such exemplary embodiments should not limit the engine types that may be used with the present disclosed valve activation apparatus. 
   Referring now to  FIGS. 1A–1J , an improved hydraulic variable valve train apparatus is disclosed. The improved hydraulic variable valve train apparatus is generally adapted to provide both variable valve displacement and variable valve timing in a hydraulically actuated system. 
   Referring now to  FIG. 1A , one embodiment of an improved variable valve train apparatus, having a valve  140  shown in a closed position, is illustrated. A cross-section of a hydraulic camshaft lobe  108  of the exemplary hydraulic variable valve train is illustrated in  FIG. 1A .  FIG. 1A  shows the hydraulic camshaft lobe  108  in an “exhaust” position. The hydraulic camshaft lobe  108  is used in the combustion chamber (not shown) of an engine. The hydraulic camshaft lobe  108  typically rotates concentrically about a circumferential axis of rotation  160 . In one embodiment, the hydraulic camshaft lobe  108  includes a first graduated cavity  110  disposed on a first portion of the hydraulic camshaft lobe  108 . Similarly, on a second portion of the hydraulic camshaft lobe  108  is included a second graduated cavity  112 . As described in more detail below, the cavities  110  and  112  are “graduated” in the sense that the contour of the cavities  110  and  112  have a continuous slope of changing depth from a first width (having a first depth) to a second width (having a second depth), wherein the first width differs from the second width, and wherein the first depth also differs from the second depth. The variations in both depth and height vary along an axis that is perpendicular with respect to the page of  FIGS. 1A–1I . Hence,  FIGS. 1A–1I  illustrates cross-sectional views of a portion of the graduated cavities  110  and  112 . In this embodiment, at least one valve  140  protrudes into the combustion chamber on the poppet end of the valve  140 , and is operatively coupled to the hydraulic camshaft lobe  108  via a valve stem  141  end of the valve  140 . 
   As described above,  FIG. 1A  illustrates the hydraulic camshaft lobe  108  in an “exhaust” position. Hydraulic camshaft lobe  108  is said to be in the exhaust position because the relative positioning of the first and second graduated cavities  110  and  112  create an operative connection between the control port  104  and the exhaust port  106 . Similarly, the exhaust position of the hydraulic camshaft lobe  108  also creates an operative fluid communication or coupling between the control port  116  and the exhaust port  118 . Hence, in the exhaust position, the hydraulic camshaft lobe  108  creates a fluid coupling or communication that allows for the evacuation of exhaust gases from the combustion chamber, via the control ports  104  and  116 , through the graduated cavities  110  and  112 , and into the exhaust ports  106  and  118  respectively. 
   The hydraulic circuit  100  is adapted to actuate the valve  140  into open and closed positions.  FIG. 1A  illustrates the valve  140  in a closed position. When there is no hydraulic force exerted on the actuator interface  144 , a spring  142  exerts a force on the valve stem  141 , which functions to push a piston  143 , within an actuator  120 , away from a valve guide  145 , thereby moving the valve  140  into the closed position. A mating surface  146  is a valve seat. In one embodiment, the mating surface  146  is an intake port, functioning (in  FIG. 1A ) to seal off (prevent) fuel flow into the combustion chamber. In another embodiment, the mating surface  146  is an exhaust port, functioning (in  FIG. 1A ) to seal the combustion chamber, thereby preventing any gaseous fluids from escaping the combustion chamber. A plurality of arrows  103  in  FIG. 1A  illustrate a direction of fluid flow toward the control ports  104  and  116  when the valve  140  is in the closed position. 
   Referring now to  FIG. 1B , an embodiment of an improved hydraulic variable valve train apparatus having a valve  140  is shown in an open position. In this embodiment, the hydraulic camshaft lobe  108  has moved from the exhaust position (as shown in  FIG. 1A ) to an “inlet” position, as denoted by the rotation of the circumferential axis of rotation  160 . The first and second graduated cavities  110  and  112  remain stationary with respect to the hydraulic camshaft lobe  108  throughout the rotation of the axis of rotation  160 , as the cavities  110  and  112  rotate concentrically with camshaft lobe  108 . Hence, as the camshaft lobe  108  rotates from the exhaust position (of  FIG. 1A ) to the inlet position (of  FIG. 1B ), the previously described fluid communication or coupling between the control port  104  and the exhaust port  106  is disconnected. Similarly, when the camshaft lobe  108  rotates from the exhaust position to the inlet position, the above described fluid connectivity between the control port  116  and the exhaust port  118  is also disconnected. 
   As shown in  FIG. 1B , the poppet valve  140  is in an open position, with respect to the mating surface  146 . In one embodiment, the mating surface  146  is an intake port, functioning (in  FIG. 1B ) to pass (allow) fuel flowing into the combustion chamber. In another embodiment, the mating surface  146  is an exhaust port, functioning (in  FIG. 1B ) to provide an opening to the combustion chamber, thereby allowing any gaseous fluids within the combustion chamber to escape from the combustion chamber. 
   As shown in  FIG. 1B , when the camshaft lobe  108  is rotated into the inlet position, the inlet portion  102  is in fluid communication with the control ports  104  and  116 . That is, when the camshaft lobe  108  is rotated into the inlet position, the inlet portion  102   a  is in fluid connectivity with the control port  116  via the graduated cavity  112 . Similarly, in the inlet position, the inlet portion  102   b  is in fluid connectivity with the control port  104  via the graduated cavity  110 . 
   When the inlet portions  102   a  and  102   b  fluidly connect with the control ports  116  and  104 , respectively, hydraulic fluid provided by a hydraulic fluid source  114  create a hydraulic force (as shown by the arrows  103  in  FIG. 1B ) in the direction of the actuator interface  144 . Hydraulic force is applied to the actuator interface  144  when hydraulic fluid is allowed to flow from the hydraulic fluid source  114  through the inlet portion  102   a  to the control port  116  via the graduated cavity  112 . Similarly, hydraulic force is applied to the actuator interface  144  when hydraulic fluid is allowed to flow from the hydraulic fluid source  114 , through the inlet portion  102   b , to the control port  104  via the graduated cavity  110 . 
   In one embodiment of the disclosed variable valve train apparatus, the hydraulic fluid source  114  comprises a hydraulic fluid pump. In another embodiment, the hydraulic fluid source  114  comprises a hydraulic fluid reservoir. In some embodiments, the hydraulic fluid comprises oil. However, it will be appreciated by those skilled in the valve arts that literally any convenient hydraulic fluid may be used to practice the present teachings. 
   In one embodiment of the present variable valve train apparatus, valve timing and displacement can be varied as hydraulic camshaft lobe  108  moves along a longitudinal axis of the camshaft. Referring to  FIGS. 1A–1I , the longitudinal axis of the camshaft is perpendicular (vertical) with respect to the page of  FIGS. 1A–1I . As the hydraulic camshaft lobe  108  moves along the longitudinal axis of the camshaft, the graduated cavities  110  and  112  vary in both depth and width. This action, in turn, simultaneously varies the valve timing and valve displacement within the hydraulic fluid cam. Valve timing determines when the valve is opened and closed. Valve displacement determines the amount of valve lift and the duration of the valve lift. In one embodiment, valve timing alone is varied as the hydraulic camshaft lobe  108  moves along the longitudinal axis. In another embodiment, valve displacement alone is varied as the hydraulic camshaft lobe  108  moves along the longitudinal axis. 
   Referring now to  FIGS. 1C–1H , a rotational operational sequence of the improved hydraulic camshaft lobe  108  is illustrated.  FIG. 1C  illustrates an exhaust position, wherein the control port  116  is fluidly coupled to the exhaust port  118  via the operation of the graduated cavity  112 . Similarly, control port  104  is in fluid communication with the exhaust port  106  via the graduated cavity  110 .  FIG. 1D  illustrates a subsequent position in the rotation of the hydraulic camshaft lobe  108 , wherein the control ports  104  and  116  are no longer in fluid communication with the exhaust ports  106  and  118 , respectively.  FIG. 1E  illustrates a subsequent position in the rotation of the hydraulic camshaft lobe  108 , wherein the inlet portions  102   a  and  102   b  are fluidly coupled with the graduated cavities  110  and  112 , respectively.  FIG. 1F  illustrates a subsequent position in the rotation of the hydraulic camshaft lobe  108 , also known as an “inlet” position, wherein the inlet portion  102   a  becomes fluidly coupled to the control port  116  via the graduated cavity  110 . Similarly, the inlet portion  102   b  is fluidly coupled to the control port  104  via the graduated cavity  112 .  FIG. 1G  shows a subsequent position in the rotation of the hydraulic camshaft lobe  108 , also known as the “exhaust” position, which is similar to the position shown in  FIG. 1C .  FIG. 1H  shows a subsequent position in the rotation of the hydraulic camshaft lobe  108 , which is similar to the position of  FIG. 1D . 
   Referring now to  FIG. 1I , a cam phasing embodiment of the present improved hydraulic variable valve train apparatus is shown.  FIG. 1I  illustrates a cross-sectional view of an improved camshaft lobe  108  having a first cavity  110  and a second cavity  112 . 
   In some applications it may be desirable to vary cam timing, while simultaneously holding cam displacement a constant. In these applications, the camshaft can be phased to activate the opening and closing of the valve  140  at different desired times, while not varying the displacement (valve lift and duration) of the valve  140 . In accordance with one embodiment of the present apparatus, such cam phasing is accomplished by shifting an initial rotational angle of the cam lobe  108  by an initial angle θ  122 . In one embodiment, this initial rotational angle is shifted relative to corresponding crankshaft timing. 
     FIG. 2  shows a graph  230  of valve displacement as a function of rotational cam angle. In one embodiment, the cam angle  226  is shifted by an initial rotational angle θ  222 , which shifts the valve opening and closing time by θ degrees. As shown in  FIG. 2 , the cam angle graph  226  is shifted by θ degrees to cam angle graph  228 . 
   Referring now to FIGS.  3 Ai,  3 Aii,  3 Aiii,  3 Bi,  3 Bii,  3 Biii,  3 Ci,  3 Cii, and  3 Ciii an improved hydraulic fluid cam apparatus is described. In this embodiment of the present disclosure, at least one valve (not shown) is operatively coupled to a camshaft lobe  300 , such that the valve is actuated by a hydraulic circuit that is operatively coupled to the camshaft lobe  300  via a port  306 . The fluid cam apparatus is itself mounted upon another portion of an engine system, allowing cam lobes to “slide” laterally (similar to a piston), either by mechanical, and/or electrical (e.g., solenoid), and/or other hydraulic system. 
   FIG.  3 Ai illustrates an improved hydraulic fluid cam  300  shown in a maximum position with respect to valve timing and displacement. A first camshaft lobe position  302   a  illustrates the maximum position of the hydraulic fluid cam  300 , in the sense that the port  306  is disposed at a position of maximum width and depth of a first cavity  304  having a first predetermined shape. In some embodiments, the port  306  comprises a control port, an exhaust port, and/or an inlet portion, depending upon the angle of rotation of the camshaft lobe position  302   a . In this embodiment, as shown in FIGS.  3 Ai,  3 Aii and  3 Aiii, the first predetermined shape has a first width, disposed at a first portion of the camshaft lobe position  302   a , which is laterally wider across the camshaft lobe position  302   a  of the cavity  304  than at a second width, disposed at a second portion of camshaft lobe position  302   a . In this embodiment, a wider width corresponds to earlier valve opening and later valve closing timing. As shown in FIGS.  3 Ai,  3 Aii and  3 Aiii, when the port  306  is positioned on the first width, wherein the cavity  304  is widest (and hence the port  306  has its longest contact with the cavity  304 ), an earlier valve opening time and a later valve closing time results. In contrast, when the port  306  is positioned in either a “graduated” position  302   b  (shown in FIG.  3 Bi) or a non-actuated position  302   c  (shown in FIG.  3 Ci), as described more fully below, a delayed (or NO) valve opening time and earlier (or NO) valve closing time results. 
   Similarly, when in camshaft lobe position  302   a , the cavity  304  proximate the port  306  also has an increased depth as compared to other positions of the camshaft lobe. That is, at such a first portion of the camshaft  300 , the cavity  304  has a maximum depth relative to other portions of the cavity  304 . At a first depth, wherein the cavity  304  is widest (and wherein the port  306  has its deepest contact with the cavity  304 ), a maximum displacement (lift) of the valve results. In contrast, when the port  306  is positioned in either a “graduated” camshaft lobe position  302   b  (see FIGS.  3 Bi,  3 Bii) or a non-actuated camshaft lobe position  302   c  (see FIGS.  3 Ci and  3 Cii), displacement (lift) of the valve is decreased. 
   FIG.  3 Aii is a side view of the improved hydraulic fluid cam apparatus of FIG.  3 Ai in camshaft lobe maximum position  302   a.    
   FIG.  3 Aiii is a maximum displacement graph  308  of valve displacement versus cam angle, corresponding to the first cavity  304  of cam lobe position  302   a  of FIG.  3 Ai and FIG.  3 Aii. The maximum displacement graph  308  illustrates a maximum displacement curve  310  having a horizontal portion corresponding to constant maximum displacement of a valve operatively coupled to the camshaft when at camshaft lobe position  302   a . The horizontal portion of the maximum displacement curve  310  corresponds to the greatest distance a valve will open in a combustion chamber. The maximum valve displacement illustrated in FIG.  3 Aiii corresponds directly to the positioning of the port  306  over the first portion of cavity  304  (as shown in FIGS.  3 Ai and  3 Aii), which portion has the maximum depth and maximum width of the cavity  304 . 
   FIGS.  3 Bi,  3 Bii, and  3 Biii, illustrate an improved hydraulic fluid cam  300  shown in a “graduated” position  302   b  with respect to valve timing and displacement. FIG.  3 Bi is identical to FIG.  3 Ai in every respect, with the exception that the port  306  is shown in a different placement relative to the cavity  304 . This difference in placement of the port  306  is achieved by moving the hydraulic fluid cam  300  from a first cam lobe position (“maximum” position)  302   a  (as in FIG.  3 Ai) to a second cam lobe position (“graduated” position)  302   b  (as in FIG.  3 Bi) along a longitudinal axis of the camshaft. 
   Referring now to FIG.  3 Biii, a variable “graduated” displacement graph  328  of valve displacement versus cam angle, corresponding to the first cavity  304  of the cam lobe position  302   b  shown in FIGS.  3 Bi and  3 Bii, is shown. The “graduated” displacement graph  328  illustrates a variable displacement curve  330 , having a rounded portion as a valve lift displacement, corresponding to a variable valve cam angle and lift. 
   Referring now to FIGS.  3 Ci,  3 Cii,  3 Ciii, an improved hydraulic fluid cam  300  is shown in a “non-actuated” position  302   c  with respect to valve timing and displacement. 
   FIG.  3 Ci is a front view of an improved hydraulic fluid cam  300  apparatus shown in a non-actuated position  302   c . As shown in FIG.  3 Ci, the cam  300  is not activated because the port  306  is not in operative connection with the cavity  304 . When positioned as shown in FIGS.  3 Ci and  3 Cii, no valves are actuated. 
   FIG.  3 Ciii shows a non-actuated displacement graph  348 , corresponding to the cam lobe position  302   c  of FIGS.  3 Ci and  3 Cii. The displacement graph  348  has no plotted points to describe valve actuation, because port  306  is not in contact with cavity  304 , resulting in no valve actuation. 
   Referring now to  FIG. 4A , an embodiment of the fluid cam  469  of the present teachings is illustrated in a maximum displacement position. In this embodiment, a first cavity  470  has a first predetermined shape, having a first width and a second width associated therewith, and is disposed in a first position as illustrated. A second cavity  472  has a second predetermined shape, having a first width and a second width associated therewith, and is disposed in a second position, as illustrated.  FIG. 4A  also shows a first port  474 , disposed in the first cavity  470 , and a second port  476 , disposed in the second cavity  472 , in a maximum valve displacement position on fluid cam  469 . 
   Referring now to  FIG. 4B , a fluid cam  469  is shown in a “graduated” position. The illustrated position is “graduated” in the sense that a depth and a width of the cavities  470  and  472  vary from the maximum position (as shown in  FIG. 4A ), toward a non-actuated position (as shown in  FIG. 4C ). As the fluid cam  469  is moved along a longitudinal axis (horizontally from left to right in the  FIGS. 4A–4C ), the fluid cam  469  moves from the maximum displacement position of  FIG. 4A  and into the graduated position of  FIG. 4B . In this graduated position, the ports  474  and  476  have moved from the maximum displacement position of  FIG. 4A  into a position of graduated (i.e., variable) valve actuation. In the graduated position, the ports  474  and  476  contact the cavities  470  and  472 , respectively, resulting in varying valve timings and varying valve displacement. In other words, the farther the ports  474  and  476  are positioned away from the maximum displacement position shown in  FIG. 4A , the shorter the valve opening and closing periods become (i.e., variable valve timing) and the smaller the valve lift and duration become (i.e., displacement). However, as the ports  474 ,  476  approach closer and closer to the maximum displacement position shown in  FIG. 4A , the valve opening and closing periods increase, and the valve lift and duration increases. 
   Referring now to  FIG. 4C , a fluid cam  469  is shown in a non-actuated position. In this non-actuated position, the ports  474  and  476  are no longer in contact with their respective cavities  470  and  472 . In this position, the valves are not actuated. 
   In some embodiments of the fluid cams shown in  FIGS. 4A–4C , valve timing (cam phasing) is varied, while valve displacement is held constant. In other embodiments, valve timing is held constant, while valve displacement is varied. 
   Referring now to  FIGS. 5A and 5B , an improved variable valve train apparatus is described.  FIG. 5A  shows a front view of a variable timing/variable depth cam lobe  500 .  FIG. 5B  shows a side view of the variable timing/variable depth cam lobe  500  of  FIG. 5A . Main cavities  508 , and  514  are substantially similar to the cavities described above with reference to  FIGS. 1A–1I , FIGS.  3 Ai– 3 Cii, and  FIGS. 4A–4C . Additional cavities  506 ,  510 ,  512 , and  516  function to provide additional actuation to vary valve timing and/or valve displacement. That is, when it is desired to have additional valve timing control (e.g., modulating valve stroke), the cam lobe  500  may optionally be shifted so that a valve will contact the cam lobe  500  at one of the main cavities  508  or  514 , and the valve will also contact additional cavities  506 ,  516 , or  510 ,  512 . Similar to the main cavities  508  and  514 , the additional cavities  506 ,  516 ,  510 , and  512  have varying depths and widths, customizable by a designer to conform to specific engine design requirements. 
   As an engine changes a number of revolution per minute (“RPM”),it is desireable to change either the value timing or valve displacement, as such changes can dramatically improve engine horsepower and also conserve fuel. The cam lobe  500  is laterally actuated via hydraulic and/or electromechanical force, as will be appreciated by those of ordinary skill in the art. As the cam lobe  500  is laterally actuated, under either electromechanical or hydraulic force to vary a depth of at least one cavity  506 ,  510 ,  512 , and  516  and/or vary a width of at least one cavity  506 ,  510 ,  512 , and  516 . Such variation of depth and width can be independently or simultaneously varied by selectively sliding the cavities  506 ,  510 ,  512 , and  516 , as will be described in more detail below with reference to  FIG. 5D and 5F . 
   Referring now to  FIG. 5C , a valve displacement versus cam angle graph  540  is shown. Peak  542  corresponds to a maximum valve displacement (lift), as shown in a flat, horizontal portion of peak  542 . An exemplary displacement  544  is shown in  FIG. 5C , indicating that the additional cavities  506 ,  510 ,  512 , and  516  have been employed to actuate variable valve timing and/or displacement. 
   Referring now to  FIGS. 5D–5G , sliding cavity action of the cam lobe  500  is illustrated.  FIG. 5D  illustrates a side view of a cam lobe  500  having a main cavity  514  and an additional cavity  510  and  512  with a sliding block  513  and  515 .  FIG. 5D  illustrates a main cavity  514  as providing primary valve actuation. When additional valve actuation is desired, at least one sliding block  513  and  515  may optionally be actuated from a first position to a second position. In the first position, the sliding blocks  513  and  515  do not provide additional valve actuation, as the main cavity  514  is providing all valve actuation as illustrated in the valve displacement diagram of  FIG. 5E .  FIG. 5E  illustrates a single valve displacement of the main cavity  514  in a first position. 
     FIG. 5F  illustrates a side view of another embodiment of a cam lobe  500  having a main cavity  514  and an additional cavity  510  and  512  with a sliding block  513  and  515 .  FIG. 5F  illustrates a second position of the cam lobe  500 , wherein additional cavities  510  and  512  actuate laterally (along the longitudinal axis of the camshaft) and function to provide additional valve actuation, as illustrated in  FIG. 5G .  FIG. 5G  illustrates a valve displacement diagram corresponding to the cam lobe  500  of  FIG. 5F . A first curve  517  comprises the main cavity  514  actuation plot, while a second curve  519  comprises a contribution to variable valve timing and/or displacement from additional cavities  510  and  512 . 
   In one embodiment, the width of at least one sliding cavity is varied, while maintaining the depth of the sliding cavities constant. By varying the widths of the sliding cavities while holding the cavity depths constant, valve timing is varied but valve displacement is held constant. 
   In yet another alternate embodiment of the improved variable train apparatus, both the depth and width of the sliding cavities  506 ,  510 ,  512 ,  513 ,  515 , and  516  can be selectively varied. Varying the width and depth of the sliding cavities correspondingly varies both the valve timing and displacement. Small variations in valve depth and timing can be made in order to accommodate varying engine demands, such as, for example, those brought about when a vehicle is driven uphill. 
   Referring again to  FIG. 5G , it is possible to obtain the second curve  519  without obtaining the first curve  517 . As described above with reference to  FIG. 5F , if the cam lobe  500  is positioned such that the main cavity  514  is not actuating a valve, then the first curve  517  is not present. In this configuration, it is possible to actuate the sliding blocks  513  and  515 , such that a valve will be modulated in depth and/or timing, by the sliding blocks  513  and  515 , thereby causing the second curve  519 , even in the absence of the first curve  517 . Additionally, although the present disclosure has described sliding blocks  513  and  515  partially overlapping the main cavities  514 , one variation is constructing a sliding block  513  and  515  that, will span the entire length of the main cavities  514 , thereby giving an engine designer more flexibility in the design process. 
   In one embodiment, a mechanical wedge, acting as a cavity actuation mechanism, actuates longitudinally along a longitudinal axis of the hydraulic camshaft lobe. The wedge has a leading portion and a trailing portion. The wedge slides inside at least one additional sliding cavity to vary either the width or the depth of the cavity. Actuated by either electromechanical or hydraulic force, the mechanical wedge controls the variable sliding action of the sliding cavities. 
   Cam phasing of valves can be accomplished in a manner of ways over an RPM range, using the present teachings. In one embodiment, the sliding cavities  513  and  515  are actuated via electromechanical or hydraulic force, and function to change the displacement and/or timing of the valves in the combustion chamber. 
   Each practical and novel combination of the elements and alternatives described hereinabove, and each practical combination of equivalents to such elements, is contemplated as an embodiment of the invention. Because many more element combinations are contemplated as embodiments of the invention than can reasonably be explicitly enumerated herein, the scope of the invention is properly defined by the appended claims rather than by the foregoing description. All variations coming within the meaning and range of equivalency of the various claim elements are embraced within the scope of the corresponding claim. Each claim set forth below is intended to encompass any apparatus or method that differs only insubstantially from the literal language of such claim, as long as such apparatus or method is not, in fact, an embodiment of the prior art. To this end, each described element in each claim should be construed as broadly as possible, and moreover should be understood to encompass any equivalent to such element insofar as possible without also encompassing the prior art. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising.”