Patent Publication Number: US-8967103-B2

Title: Variable valve timing arrangement

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to an internal combustion engine, and more particularly relates to a variable valve timing arrangement for the internal combustion engine. 
     BACKGROUND 
     Various developments have been made in the control and design of an internal combustion engine to improve fuel efficiency while meeting ever stricter emission requirements. Improvements in valve timing arrangements have been made to control timing as well as a degree of opening of the intake and exhaust valves. As the internal combustion engine are required to operate at a range of speeds and loading conditions, the variable valve timing arrangement may allow the flow of gases into and from the engine to be tailored based on the operating conditions. 
     PCT Publication Number 2006/092312 discloses a variable mechanical valve control of an internal combustion engine including a bottom camshaft for adjusting a valve stroke and an opening and closing time, said valve control enabling an extremely compact transmission gear to be achieved between a push rod drive and the inlet and outlet valves, to reduce the number of components required for the transmission gear and to obtain a mechanical valve train that is completely variable, with a bottom camshaft. To achieve this, an intermediate lever is connected to a valve push rod by means of a shaft, in such a way that a slide gate roller, which is rotatably mounted on the shaft, is displaced by the camshaft in a slide gate. According to the invention, a first contact surface on the intermediate lever is supported in a reinforced manner by means of a spring on an eccentric shaft, or on a second contact surface and a lever is displaced using a working curve, said lever opening and/or closing the two-way gas valves. Elements are also provided, in particular on a lifter that is located on the push rod for the additional adjustment of the phase position of the valve elevations of the two-way gas valves with simultaneous play-free adjustment of the valve stroke and the invention is also equipped with elements for the additional independently controllable valve stroke opening and closing for each camshaft rotation. 
     SUMMARY 
     In one aspect, a variable valve timing arrangement for an engine system is disclosed. The timing arrangement includes a cam lobe, a cam follower, a pushrod, a pushrod rotation mechanism, and a cam follower adjustment mechanism. The cam follower is configured to follow the cam lobe, the pushrod is operably connected with the cam follower. The pushrod rotation mechanism is configured to selectively rotate the pushrod. The cam follower adjustment mechanism is configured to reposition the cam follower based on the rotation of the pushrod. 
     In another aspect, a method of varying valve timing in the engine system is disclosed. The method includes determining the engine operating parameter, and selectively actuating the pushrod rotation mechanism to rotate the pushrod based on the engine operating parameter. The method further includes repositioning the cam follower by the cam follower adjustment mechanism based on the rotation of the pushrod. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an exemplary schematic view of an engine system. 
         FIG. 2  illustrates an exemplary variable valve timing arrangement for the engine system of  FIG. 1  with a cam follower in normal position. 
         FIG. 3  illustrates the variable valve timing arrangement of  FIG. 2  with the cam follower in advanced position. 
         FIG. 4  illustrates the variable valve timing arrangement of  FIG. 2  with the cam follower in retarded position. 
         FIG. 5  illustrates an exemplary flowchart of a method for varying valve timing in the engine system. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Generally, corresponding reference numbers will be used throughout the drawings to refer to the same or corresponding parts. 
       FIG. 1  illustrates a schematic view of an exemplary engine system  100 , in which various embodiments of the present disclosure may be implemented. The engine system  100  includes a reciprocating internal combustion engine  102 . In one embodiment, the engine  102  may be a diesel engine. In alternative embodiments, the engine  102  may be a gasoline engine or any other reciprocating internal combustion engine as known in the art. The engine  102  may include an engine block  104  in which a plurality of cylinder assemblies  106  are disposed within. Although a plurality of cylinder assemblies  106  are shown in  FIG. 1 , other embodiments of the engine  102  may include only one cylinder assembly  106 . The cylinder assemblies  106  of the engine  102  may be disposed in any configuration, such as but not limited to, in-line engine configuration, V-engine configuration, U-engine configuration, or W-configuration. 
     The cylinder assembly  106  includes a combustion chamber  108 . The cylinder assembly  106  may include one or more overhead valves such as intake valves  110 , to control air flow into the combustion chamber  108 . A hollow runner or intake manifold  112  may be formed in or attached to the engine block  104  such that it extends over or proximate to each of the cylinder assemblies  106 . The intake manifold  112  may communicate with an intake line  114  that directs air to the engine  102 . Fluid communication between the intake manifold  112  and the cylinder assemblies  106  may be established by a plurality of intake runners  116  extending from the intake manifold  112 . In the illustrated embodiment, the intake valves  110  open and close to selectively introduce the intake air from the intake manifold  112  into the combustion chamber  108 . 
     The cylinder assembly  106  further includes one or more exhaust valves  118  to direct exhaust gases out of the combustion chamber  108  after a combustion event. An exhaust manifold  120  communicating with an exhaust line  122  may be disposed in or proximate to the engine block  104  such that it extends over or proximate to each of the cylinder assemblies  106 . The exhaust manifold  120  may receive exhaust gasses by selective opening and closing of the one or more exhaust valves  118  associated with each cylinder assembly  106 . The exhaust manifold  120  may communicate with the cylinder assemblies  106  through exhaust runners  124  extending from the exhaust manifold  120 . 
     As shown in the illustrated embodiment, the intake valves  110  and the exhaust valves  118  are provided in an overhead position of the cylinder assemblies  106  and are selectively actuated by a camshaft  126  disposed within the engine block  104 . In alternative embodiments, at least one of the intake valves  110  or the exhaust valves  118  may be placed at the overhead position and other intake and/or exhaust valves  110 ,  118  may be disposed in the engine block  104  such as at a sidewall of the cylinder assemblies  106  or other positions as known in the art. 
     The engine system  100  includes a fuel system  128  configured to supply fuel to the engine  102  during operation. In the illustrated embodiment, the fuel system  128  includes a fuel reservoir  130  that can accommodate a hydrocarbon-based fuel such as diesel, gasoline etc. A fuel line  132  directs the fuel from the fuel reservoir  130  into the cylinder assemblies  106 . To pressurize the fuel and force it through the fuel line  132 , a fuel pump  134  may be disposed in the fuel line  132 . An optional fuel conditioner  136  may also be disposed in the fuel line  132  to filter the fuel or otherwise condition the fuel by, for example, introducing additives to the fuel, heating the fuel, removing water, and the like. 
     To introduce the fuel into the cylinder assemblies  106 , the fuel line  132  may be in fluid communication with one or more fuel injectors  138  that are associated with each of the cylinder assemblies  106 . While the illustrated embodiment depicts the fuel line  132  terminating at the fuel injectors  138 , the fuel line  132  may establish a fuel loop that continuously circulates fuel through the plurality of fuel injectors  138  and, optionally, delivers unused fuel back to the fuel reservoir  130 . Alternatively, the fuel line  132  may include a fuel collector volume or rail (not shown), which supplies pressurized fuel to the fuel injectors  138 . The fuel injectors  138  may be electrically actuated devices that selectively introduce a measured or predetermined quantity of fuel into each cylinder assemblies  106 . In alternative embodiments, the engine system  100  may include other fuel systems  128  as known in the art. 
     To coordinate and control the various systems and components associated with the engine system  100 , the engine system  100  includes an electronic or computerized control unit, module, or controller  140 . The controller  140  may be adapted to monitor various operating parameters and to responsively regulate various variables and functions affecting operations of the engine system  100 . The controller  140  may include a microprocessor, an application specific integrated circuit (ASIC), or other appropriate circuitry, and may have memory or other data storage capabilities. The controller  140  may perform operations, include functions, steps, routines, data tables, data maps, charts, and the like, saved in, and executable from, read only memory, or another electronically accessible storage medium, to control the engine system  100 . Although in  FIG. 1 , the controller  140  is illustrated as a single, discrete unit, in other embodiments, the controller  140  and its functions may be distributed among a plurality of distinct and separate components. The single unit or multiple component controller  140  may be located on-board the engine  102 , a machine powered by the engine  102 , and/or in a remote location. 
     The controller  140  may include means for determining various engine operating parameters, based at least in part, on signals received from one or more engine operating parameter sensors associated with the engine system  100 . The engine operating parameter sensors may be configured to generate engine operating parameter signals indicative of a particular engine operating parameter. In an embodiment, the controller may determine engine speed and cylinder pressure using a speed sensor  142  and one or more cylinder pressure sensors  144 . The speed sensor  142  and the cylinder pressure sensors  144  may be operatively connected to the controller  140  via a first communication link  146  and a second communication link  148 , respectively. Alternatively, the engine operating parameters may include, but are not limited to, loading conditions, power output, engine temperature, fuel mass flow rate, air mass flow rate, and the like. In one embodiment, the controller  140  is configured to generate a desired valve timing signal indicative of a desired valve timing to control a variable valve timing arrangement  150  via a third communication link  151  as a function of the engine operating parameters, which is further explained in relation to  FIGS. 2 to 4 . 
     Referring now to  FIGS. 2 ,  3 , and  4  an embodiment of the variable valve timing arrangement  150  is illustrated with the engine system  100  of  FIG. 1 . The variable valve timing arrangement  150  is operatively connected to the intake and/or the exhaust valves  110 ,  118  of the engine  102  and is configured to vary timing for the opening and closing of the valves  110 ,  118 . The camshaft  126  may be disposed substantially beside and slightly above a crankshaft  154  in the engine  102 , as shown in  FIGS. 2-4 . The camshaft  126  may be driven by the crankshaft  154  via a transmission means  156 , such as, but not limited to gears, or belts. The variable valve timing arrangement  150  may include a cam follower  152  configured to follow one or more cam lobes  158  disposed along a length of the camshaft  126 . As the camshaft  126  rotates, the cam lobes  158  may cause the intake and the exhaust valves  110 ,  118  to move up and down in a desired manner for the respective cylinder assemblies  106 . The movement of the intake and the exhaust valves  110 ,  118  may seal and unseal ports leading into the combustion chamber  108 . In an alternative embodiment, such as a two stroke engine  102 , the cam lobes  158  may be disposed integrally on the crankshaft  154  of the engine  102 . 
     The cam follower  152  may be a roller-type follower. Alternative embodiments of the cam follower  152  may include, but are not limited to, a flat follower, a point/knife follower, or an offset follower. The rotary motion of the camshaft  126  may be converted to a reciprocating motion of the cam follower  152  via the cam lobes  158 . In the illustrated embodiment, the cam follower  152  is rotatably supported at a distal end of a tappet  160 . 
     A pushrod  162  may be operatively connected with the cam follower  152 . The pushrod  162  may be rotatably mounted at a proximal end of the tappet  160 . The pushrod  162  may be connected to a rocker arm  164 . The pushrod  162  may be linked to the tappet  160  by way of a first joint  166 , such as, a ball-and-socket, a swivel, or a turn-and-slide joint. The pushrod  162  may be linked to the rocker arm  164  by way of a second joint  168 , such as a ball-and-socket, a swivel, or a turn-and-slide joint. As illustrated, the intake valve  110  may be actuated by the rocker arm  164 , which is articulated with the tappet  160  and the pushrod  162 , to push at the intake valve  110 . It will apparent to a person having ordinary skill in the art that, a substantially similar valve actuation mechanism may also be provided for the exhaust valve  118 . 
     The variable valve timing arrangement  150  may include a pushrod rotation mechanism  170  configured to selectively rotate the pushrod  162  based on the desired valve timing signal received from the controller  140 . The pushrod rotation mechanism  170  may include a rotating means  172  driven by a motor  174 . The rotating means  172  may be a set of gears, such as, but not limited to, a set of bevel gears. The rotating means  172  may include a first bevel gear  176  operatively connected to an output shaft  178  of the motor  174 . The first bevel gear  176  is drivably connected to a second bevel gear  180  disposed on the pushrod  162  and configured to rotate the pushrod  162 . In alternative embodiments, the rotating means  172  may include other embodiments, such as, but not limited to, a belt or a chain. 
     The variable valve timing arrangement  150  may include a cam follower adjustment mechanism  182 , as illustrated in a magnified view, the cam follower adjustment mechanism  182  may be configured to reposition the cam follower  152  based on the rotation of the pushrod  162 . The cam follower adjustment mechanism  182  may include a block  184 , slidably disposed on the pushrod  162 . The block  184  may be fastened on the pushrod  162  via threads  186 . The threads  186  on the pushrod  162  may allow the block  184  to slide up or down along the pushrod  162  based on the rotation of the pushrod  162 . The sliding movement of the block  184  may control the position of the cam follower  152  attached to the tappet  160  via a linkage arm  188 . The linkage arm  188  may be pivotally connected to the block  184  at a first pivot point  190 . The linkage arm  188  may pivotally connected to the tappet  160  at a second pivot point  192 . The block  184  may be slidably keyed into the engine block  104  to prevent rotation of the block  184  along with the pushrod  162 . 
       FIG. 2  illustrates an exemplary embodiment of the engine system  100  with the cam follower  152  in a normal position for actuation of the intake or the exhaust valves  110 ,  118 .  FIG. 2  illustrates the same exemplary embodiment of the engine system  100  with the cam follower  152  in an advanced position for advancing the opening of the intake or the exhaust valves  110 ,  118 .  FIG. 3  illustrates the same exemplary embodiment of the engine system  100  with the cam follower  152  in a retarded position for delaying the opening of the intake or the exhaust valves  110 ,  118 . The linkage arm  188  associated with the block  184  and the tappet  160  may selectively reposition the cam follower  152  based on rotation of the push rod  162 . 
     Referring to  FIG. 3 , the first bevel gear  176  and the second bevel gear  180  may rotate the push rod  162  a first direction (shown by arrow) via the output shaft  178  of the motor  174 . During the rotation of the push rod  162  in the first direction, the threads  186  on the pushrod  162  may allow the block  184  to slide down along the pushrod  162 . The downward sliding movement of the block  184  along the pushrod  162  may position the cam follower  152  in the advanced position from the normal position via the linkage arm  188 . 
     Referring to  FIG. 4 , the first bevel gear  176  and the second bevel gear  180  may rotate the push rod  162  in a second direction (shown by arrow) via the output shaft  178  of the motor  174 . During the rotation of the push rod  162  in the second direction, the threads  186  on the pushrod  162  may allow the block  184  to slide up along the pushrod  162 . The upward sliding movement of the block  184  on the pushrod  162  may position the cam follower  152  in the retarded position from the normal position via the linkage arm  188 . Further, the rotation and the direction of rotation of the motor  174  may be controlled based on the desired valve timing signal received from the controller  140 . Accordingly, the cam follower  152  may selectively advance, retard the opening and closing of the intake or the exhaust valves  110 ,  118  based on the desired valve timing signal. 
     Industrial Applicability 
     Varying valve timing of an engine  102  in response to or as a function of engine operating conditions and/or parameters may enable the engine  102  to operate more efficiently and/or produce less of some gaseous emissions. The variable valve timing arrangement may be used in applications such as motor vehicles, machines, locomotives or marine engines, and in stationary applications such as electrical power generators, small mechanical engines such as lawn mowers, all terrain vehicles (ATVs), generators, etc. 
       FIG. 5  illustrates a flowchart of a method  500  for varying valve timing in an engine system  100 . At step  502  of the method  500 , the controller  140  may determine one or more engine operating parameters using the one or more engine operating parameter sensors such as the speed sensor  142 , and the cylinder pressure sensors  144 . The controller  140  may determine the desired valve timing as a function of the engine operating parameter and actuate the pushrod rotation mechanism  170 , at step  504 . The controller  140  may apply stored information about cam lobes  158  profiles along with the engine operating parameters to determine the desired valve timing. 
     At step  506 , the motor  174  may include a means receiving the desired timing signal from the controller  140  and driving the rotating means  172  via the output shaft  178  to rotate the pushrod  162 . At step  508 , the cam follower adjustment mechanism  182  including the block  184  fastened on the pushrod  162  via the threads  186  may move along the pushrod  162  based on the rotation of the pushrod  162  and reposition the cam follower  152  via a linkage arm  188 . The repositioning of the cam follower  152  may selectively advance or retard opening and closing of one or more overhead intake or exhaust valves  110 ,  118 . 
     The cam follower  152  may be repositioned into the advanced position (as illustrated in  FIG. 3 ) or the retarded position (as illustrated in  FIG. 4 ) along the profile of the cam lobes  158  thus advancing or delaying the intake or the exhaust valves  110 ,  118  opening timing. The variable valve timing may increase efficiency of the engine  102  by optimizing air flow in the engine  102 . The increased efficiency is manifested as better fuel economy and/or more power for a given engine displacement. In an embodiment, the controller may determine the desired valve timing for the intake and exhaust valves  110 ,  118  to adjust a degree of overlap between the openings of the intake and exhaust valves  110 ,  118  to improve fuel economy based on the load and speed of the engine  102 . 
     From the foregoing it will be appreciated that, although specific embodiments have been described herein for purposes of illustration, various modifications or variations may be made without deviating from the spirit or scope of inventive features claimed herein. Other embodiments will be apparent to those skilled in the art from consideration of the specification and figures and practice of the arrangements disclosed herein. It is intended that the specification and disclosed examples be considered as exemplary only, with a true inventive scope and spirit being indicated by the following claims and their equivalents.