Patent Publication Number: US-8113156-B2

Title: Energy recovery system for an added motion system

Description:
RELATED APPLICATION 
     This application is a continuation application of U.S. Ser. No. 11/758,757 filed on Jun. 6, 2007, which claims priority to U.S. Provisional Patent Application No. 60/817,768 filed on Jun. 30, 2006. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to a system that provides a delayed closing movement of an engine valve of an internal combustion engine, including a system that recovers energy stored in an engine valve spring during the delayed closing movement of an engine valve. 
     BACKGROUND 
     It is known in the art that a cam system, which may include, for example, a cam shaft and rocker arm, can be used to open and close the valves of an internal combustion (IC) engine. It is also known in the art that the timing of valve closure during an IC engine&#39;s induction stroke may be varied to, among other things, optimize engine performance. 
     During the initial movement of an engine valve, a cam system typically compresses an engine valve spring, and, accordingly, stores energy in the compressed spring that may be utilized during the closing stroke to provide torsional power back to the cam system. As such, the torque fed back to the cam system can reduce power demands on the engine associated with the operation of the cam system. 
     In some systems, the closing of an engine valve can be delayed for a period of time, by, for example, a hydraulic force actuator that counteracts the closing force of an associated engine valve spring. Systems that exhibit such a delayed closing movement of the engine valve are commonly referred to as “added motion” systems. 
     During the closing movement of a valve in an added motion system, fluid associated with a hydraulic force actuator may be utilized to close/seat the engine valve and, as such, bypasses the energy stored in the valve spring that would otherwise have been fed back as torsional power to a cam system. Accordingly, the energy stored in the engine valve spring is dissipated into (i.e., “lost”) in the hydraulic fluid system associated with the hydraulic force actuator. More specifically, when the hydraulic force actuator is opened, the energy is dissipated into the hydraulic fluid system by way of the spring force, which causes an increased flow of fluid at a higher velocity toward a reservoir of the hydraulic fluid system. In some circumstances, the energy stored in the engine valve spring is dissipated by heat that is created from friction as the fluid flows, with the increased velocity, through fluid flow orifices of the hydraulic fluid system. Accordingly, a net loss of power resulting from “lost” energy of the valve spring may place higher power demands on the IC engine for operating the cam system. 
     Accordingly, it would be desirable to prevent a loss of/recover energy from the engine valve spring during a delayed “added motion” closing movement. For example, energy recovered from the valve spring during a closing movement in an added motion system could be returned to the cam operating system and used to reduce power demands placed on the engine for operating the cam system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the disclosure will now be described, by way of example, with reference to the accompanying exemplary drawings, wherein: 
         FIG. 1  is a hydraulic schematic for operating one or more added motion valve systems according to an embodiment of the present invention; 
         FIG. 2  is a diagram of an added motion valve system according to an embodiment of the present invention; 
         FIG. 3  is a table generally illustrating valve lift profiles for embodiments of an added motion valve system. 
         FIG. 4  is a chart illustrating power consumption (i.e. power demands) vs. engine speeds for various ratios of fluid pressure over pressure provided by an engine valve spring; 
         FIG. 5  is a hydraulic schematic for operating one or more added motion valve systems according to an embodiment of the present invention; 
         FIG. 6  is a chart that illustrates a response time for an amount of fluid pressure boost in a pressure rail for the hydraulic schematic for operating one or more added motion valve systems according to  FIGS. 1 and 5 ; 
         FIG. 7  is a plot of fluid pressure in a pressure rail for an activated hydraulic circuit; and 
         FIG. 8  is a sampling of the plot of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     A hydraulic circuit  10  according to an embodiment of the present invention is shown in  FIG. 1 . The hydraulic circuit  10 , which may be employed in connection with an internal combustion (IC) engine, includes a plurality of valves  25 - 25   k  and actuating mechanisms  50 - 50   k . Embodiments of a valve  25 , an actuating mechanism  50 , and a representative view of a cam system  75  are generally shown in cross-section in  FIG. 2 . The valve  25 , actuating mechanism  50 , and cam system  75  may also be collectively referred to as an added motion valve system (generally identified as  100 ). 
     Cam system  75  may include a camshaft  77 , rocker arm  79 , and rocker arm roller  81 . The actuating mechanism  50  may include, among other things, a valve body  52  having a bore  54 , a piston  56 , an engine valve  58 , and a valve spring  60 . If desired, valve  25  may include a solenoid valve that permits or impedes the flow or movement of fluid  11  (i.e., fluid under pressure) from a pressure rail  12  to, for example, an upper portion  62  of the bore  54  associated with the actuating mechanism  50 . The upper portion  62  of the bore  54  may also define and be referred to as an actuator fluid volume. As illustrated, fluid  11  may also be communicated from the valve  25  (prior to intake of the engine valve  58 ) to a subsequent valve  25   a - 25   k  in the hydraulic circuit  10  (of  FIG. 1 ). 
     Referring to  FIG. 1 , fluid  11  (e.g., a fluid under atmospheric pressure) is drawn from a sump  14  by a pump  16  and is pumped or otherwise introduced and permitted passage into pressure rail  12  of the hydraulic circuit  10 . The pump  16  may be, for example, an engine pump. As shown in the illustrated embodiment, the fluid  11  may be drawn by the pump  16  to the pressure rail  12  by flowing through a valve, such as a one-way directional flow check valve  18 . 
     An accumulator  20  is included with or in communication with the pressure rail  12  to help influence or control the pressure dynamics associated with the fluid  11  within the pressure rail  12 . The pressure dynamics of the fluid  11  in the pressure rail  12  are affected by, among other things, the pulsing of the fluid  11  in the rail  12  associated with, for example, the moving or exchange of fluid  11  from one actuator (e.g., first valve  25 ) into another actuator (e.g., second valve  25   a ). Accordingly, the accumulator  20  may act as a compliant reservoir that stores fluid  11  that is exited from the valve  25  to valve  25   a  so as to reduce or damp out pulsed-wave dynamics of the fluid  11  being pulled in and pushed out of the pressure rail  12  prior to the fluid  11  being drawn into one of the valves  25 - 25   k  connected to the pressure rail  12 . 
     With reference to  FIGS. 2 and 3 , as rotation of the camshaft  77  causes reciprocating movement of a rocker arm  79  and piston  56 , a valve lift standard curve on the exhaust stroke of the engine valve  58  is shown generally designated as  200  and a valve lift standard curve on the intake stroke of the engine valve  58  is shown generally designated as  300   a . However, for example, when the valve  25  permits fluid  11  to enter the bore  54  during the intake stroke of the engine valve  58  at, for instance, a moment of full engine valve lift, the intake stroke of the engine valve  58  may be delayed or locked. Such delay or lock provides an “added motion” movement to the engine valve  58 . An added motion valve lift intake curve of the engine valve  58  is represented generally as  300   b  and, for a general comparison, a locked or delayed full valve lift is illustrated generally as  302 . Although the added motion movement of the engine valve  58  is illustrated as being part of an intake curve, it will be appreciated that the invention is not limited to the intake stroke of an intake engine valve  58 , and, for example, the added motion movement of the engine valve  58  may also be applied to the exhaust stoke of an engine exhaust valve  58 . 
     During the closing movement of the engine valve  58 , which is represented generally as segment  304  on curve  300   b , energy stored in the valve spring  60  that is commonly “lost” may be recovered by storing an increased fluid pressure in the pressure rail  12  that is approximately equal to, but less than an engine valve spring seating/closing pressure. Accordingly, the energy stored in the valve spring  60  may be returned through the inclusion of increased pressure in the rail  12  rather than being dissipated as increased fluid velocity or heat arising from fluid friction as associated fluid evacuation from conventional added motion systems. Thus, at approximately an end  306  of the added-motion full valve lift  302 , the fluid  11  in the actuator fluid volume  62  may be evacuated through the valve  25  and reintroduced into the pressure rail  12 , which, at this instance, may increase the pressure of the fluid  11  in the pressure rail  12 . As seen in  FIG. 8 , pressure waves  802  generated by the reintroduction of fluid into the pressure rail  12  will cause a low pressure in the pressure rail  12  at the check valve  18 , which will then cause fluid to be drawn in and assist in the increasing of pressurization of the pressure rail  12 . 
     Referring to  FIG. 1 , to ensure energy recovery from the engine valve spring  60 , it may be desirable to decreased pressure of fluid  11  in the pressure rail  12 , and, this pressure reduction may be accomplished, for example, by including a dump valve  22  that is connected to the pressure rail  12 . In the embodiment, dump valve  22  is connected (in parallel to check valve  18 ) to the pump  16  and pressure rail  12 . When the valve  25  evacuates the fluid  11  into the pressure rail  12 , the dump valve  22  controls the increased fluid pressure in the pressure rail  12  at an appropriate level and can, even momentarily, decrease the pressure in the pressure rail  12  at an appropriate level so that the fluid  11  can be drawn from the valve  25  into the pressure rail  12 , and/or, into a subsequent valve  25   a - 25   k.    
     Thus, the combination of the check valve  18  and dump valve  22  minimizes energy losses associated with the valve spring  60  during the closing movement of the engine valve  58 . Accordingly, a higher pressure provided by the check valve  18  and the control of decreased fluid pressure in the pressure rail  12  by the dump valve  22  can allow the engine valve spring  60  to cooperatively operate with cam system  75  so that higher power demands need not be placed on an IC engine during the closing movement  304  of the engine valve  58  in the added motion system  100 . 
     As seen in  FIG. 4 , for example, a chart illustrating power consumption (i.e. power demands) vs. engine speed is shown generally at  400  according to an embodiment. The units on the left side (i.e. y-axis) of the chart  400  is a “unit of power,” which may be, for example, horsepower, watts, or the like. The units of power displayed on the left side of the chart  400  may depend on the engine being utilized, such as, for example, a 2-, 10-, 12-, or 550-liter engine. The units on bottom (i.e. x-axis) of the chart  400  is engine speed in rotations per minute (RPM). The plots  402   a - 402   e  on the chart  400  represent a power consumption for an added motion valve system  100 . Additionally, each plot  402   a - 402   e  is differentiated from one another in view of a ratio of fluid pressure in the supply rail  12  over an equivalent engine valve spring pre-load pressure (i.e. the fluid pressure in the pressure rail  12  applied to the actuator piston area  62  can not generate a greater force than a pre-load force applied by the engine valve spring  60 ) when the added motion intake curve  300   b  is applied. The plot  404 , however, generally represents a power consumption for an added motion valve system  100  when the added motion intake curve  300   b  is not applied (i.e., movement of the engine valve  58  generally follows the valve lift standard intake curve  300   a ). It should be noted, however, that if the fluid pressure in the pressure rail  12  generates a force that exceeds the force provided by the engine valve spring pre-load, the fluid pressure in the pressure rail  12  would otherwise undesirably control the seating/closing of the engine valve  58 . Therefore, it is preferable to maintain a fluid pressure in the pressure rail  12  that does not generate a force that is greater than the force provided by the engine valve spring  60 . The fluid pressure in the pressure rail can be controlled by any number of pressure control techniques well known to those skilled in the art including the use of dump valves, such as dump valve  22 . 
     As illustrated, the plots  402   a - 402   e , may represent, respectively, for example, a fluid pressure in the pressure rail  12  that generates 5%, 15%, 40%, 70%, and 95% of the force provided by the engine valve spring pre-load. Thus, when the fluid pressure in the pressure rail  12  is 5% of the pressure provided by the engine valve spring pre-load at 750 RPM, the power consumption by the engine is approximately 1.75 units. As the fluid pressure in the pressure rail  12  is increased to 95% of the pressure provided by the engine valve spring pre-load at 750 RPM, the power consumption by the engine is approximately 0.5 units, which is much closer to the regular, “no added motion” plot  404  where power consumption by the engine at 750 RPM is approximately 0.15 units. 
     Accordingly, it is preferable to operate the hydraulic circuit  10  at the plot  402   e  where the ratio of fluid pressure in the pressure rail  12  generates in the range of 95% or greater (but less than 100%) of the forces provided by the valve spring pre-load. 
     Thus, in view of the plots  402   a - 402   e , as fluid pressure in the pressure rail  12  is increased, the hydraulic circuit  10  reduces the power needed to open the engine valve  58  by the camshaft  77  due to the torsional forces returned to the cam system  75  by the valve spring  60 . Since torsional forces can be provided by the valve spring  60  to the cam system  75 , power from the IC engine needed for driving the cam system  75  may be reduced when compared with such power losses associated with valve springs of conventional added motion systems. 
     Referring now to  FIG. 5 , a hydraulic circuit according to an embodiment of the present invention is shown generally at  500 . The hydraulic circuit  500 , which may be employed in connection with an internal combustion (IC) engine, includes a plurality of actuators  25 - 25   k  and actuating mechanisms  50 - 50   k . Embodiments of a valve  25 , an actuating mechanism  50 , and a representative view of a cam system  75  are generally shown in cross-section in  FIG. 2 . The valve  25 , actuating mechanism  50 , and cam system  75  may also be collectively referred to as an added motion valve system  100 . 
     The hydraulic circuit  500  is substantially similar to the hydraulic circuit  10  of  FIG. 1  with the exception that the hydraulic circuit  500  includes a plurality of one-way directional flow check valves which are shown generally at  518   a - 518   c . The check valve  518   a  is situated in a substantially similar location as the check valve  18  of  FIG. 1 . The check valves  518   b ,  518   c , are, however, shown branching off of the pressure rail  512  between actuating mechanisms  50   a ,  50   b  and  50   c ,  50   d , respectively. It will be appreciated that the invention is not limited to two additional check valves  518   b ,  518   c , and may, for example, include any desirable number of additional check valves, such as, for example, one or more check valves, that are positioned between any of the actuating mechanisms  50 - 50   k.    
     Referring to  FIG. 6 , a chart  600  illustrates a response time for an increase in the amount of fluid pressure in the pressure rail  12 ,  512  for the hydraulic circuits  10 ,  500 , respectively. The plot line  602   a  generally represents a fluid pressure increase response time for the hydraulic circuit  10  including one check valve  18  whereas the plot line  602   b  generally represents pressure boost response time for the hydraulic circuit  500  including three check valves  518   a - 518   c . As illustrated, a desired, increased fluid pressure in the pressure rail  512  may be achieved faster than a desired fluid pressure in the pressure rail  12  when one or more additional check valve  518   b ,  518   c  attached to the pressure rail  512 . In such circumstances, when the fluid pressure falls below the supply pressure, additional check valves  518   b ,  518   c  (i.e. check valves that supplement, for example, check valve  518   a ) may, accordingly, boost the increased fluid pressure in the pressure rail  512 . Accordingly, the additional check valves  518   b ,  518   c  allow the hydraulic circuit  500  to hasten the time for arriving at a mean fluid pressure in the pressure rail  512 . 
     Referring to  FIG. 7 , a plot of fluid pressure in the pressure rail  12 ,  512  for an activated hydraulic circuit  10 ,  500  is generally shown at  700 . The supply pressure of the fluid  11  to the rail  12 ,  512  may be on average, for example, 20-bar. Referring also to  FIG. 8 , a sampling of the plot  700  is generally shown at  800 . As shown in the sampling  800 , the fluid pressure in the pressure rail  12 ,  512  may, at times, be boosted above 20-bar due to the inclusion of check valves  18 ,  518   a - 518   c , and, at times, fall below the 20-bar supply pressure, which is shown generally at  802 . Accordingly, when the fluid pressure falls below the supply pressure, the check valves  18 ,  518   a - 518   c  may, accordingly, boost fluid pressure in the pressure rail  512  to allow the hydraulic circuit  10 ,  500  to quickly arrive at a mean fluid pressure in the pressure rail  512 . 
     The present invention has been particularly shown and described with reference to the foregoing embodiments, which are merely illustrative of the best mode or modes for carrying out the invention. It should be understood by those skilled in the art that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention without departing from the spirit and scope of the invention as defined in the following claims. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby. This description of the invention should be understood to include all novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements. Moreover, the foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application.