Abstract:
An actuator is provided for operating a valve in an engine. The actuator includes a casing forming an actuation chamber for holding a working fluid and having a first cylinder portion with a first opening and a second cylinder portion with a second opening. A first plunger is held slidably at least partially within the first cylinder portion and exposed through the first opening, and a second plunger is held slidably at least partially within the second cylinder portion and exposed through the second opening. The first plunger is reciprocally movable by action of a rotating cam to displace working fluid within the actuation chamber. The second plunger reciprocally movable by pressure exerted on the second plunger by the working fluid and arranged to exert force on a valve. The casing can also include a valve opening control comprising a third opening in the casing and a control piston slidably fit within the third opening to adjust the movement of the second plunger in reaction to movement of the first plunger, or for opening exhaust valves for engine braking.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates generally to cylinder heads in internal combustion engines. More particularly, this invention relates to cylinder heads having mechanisms to open intake and exhaust valves. 
       BACKGROUND OF THE INVENTION 
       [0002]    Most internal combustion engines have actuated valves that selectively open and close to provide combustion air and remove exhaust gases from each cylinder. Internal combustion engines usually convert chemical energy from a petroleum-based fuel such as gasoline or diesel into mechanical energy. Diesel engines usually compress air in the cylinder and then inject fuel into the cylinder for the compressed air to ignite. The ignited fuel generates rapidly expanding gases that actuate a piston. Each piston usually is connected to a crankshaft or similar device for converting the reciprocating motion of the piston into rotational motion. The rotational motion from the crankshaft may be used to propel a vehicle, operate a pump or an electrical generator, or perform other work. The vehicle may be a truck, an automobile, a boat, or the like. 
         [0003]    Many diesel engines have intake and exhaust valves near a fuel injector on the top of each cylinder. Each intake and exhaust valve usually has a valve element disposed in a passageway formed by a cylinder head. The passageway connects to the cylinder through an opening in a valve seat formed by the cylinder head. In intake valves, intake air flows through the intake passageway into the cylinder. In exhaust valves, exhaust gases flow out of the cylinder into the exhaust passageway. The valve element usually has a stem connected to a head. A spring typically is disposed on the stem. The spring biases the head into a closed position against the valve seat. Such a configuration is described for example in U.S. Pat. No. 7,347,172. 
         [0004]    Diesel engines usually have an actuating mechanism connected to the stem of each valve. The actuating mechanism selectively presses against the stem, overcomes the biasing force of the spring, and thus moves the head into an open position away from the valve seat. The actuating mechanism may be a push rod, a rocker arm, a cam on a camshaft, a hydraulically actuated drive pin, a combination thereof, or the like. 
         [0005]    Typically, the valves connect to rocker arms, which rotate on a pivot ball to open and close the valves. Typically, there is a separate rocker arm for each valve. Push rods operate the rocker arms and extend through the engine cylinder head to connect to a camshaft, via tappets. As the camshaft rotates, the push rods actuate the rocker arms to open and close the valves. The camshaft is designed to open and close the valves in conjunction with the cycling of the piston in the cylinder. Such a configuration is disclosed in U.S. Pat. No. 6,484,683. Some engines use a cam-in-head design which relocates the cam shaft up into the head and eliminates the push rods in favor of valve lifters that ride on cams along the cam shaft. 
         [0006]    In addition to valve opening mechanisms which operate the intake and exhaust valves for normal engine operation, an additional selectively controlled exhaust valve opening mechanism can be incorporated into the engine to facilitate engine braking, particularly for turbocharged diesel engines. Such a system is described for example in U.S. Pat. No. 6,779,506. 
       SUMMARY OF THE INVENTION 
       [0007]    According to exemplary embodiments of the invention, an actuator is provided for operating a valve in an engine. The actuator includes a casing forming an actuation chamber for holding a working fluid and having a first cylinder portion with a first opening and a second cylinder portion with a second opening. A first plunger is held slidably at least partially within the first cylinder portion and exposed through the first opening, and a second plunger is held slidably at least partially within the second cylinder portion and exposed through the second opening. The first plunger is reciprocally movable by action of a rotating cam to displace working fluid within the actuation chamber. The second plunger reciprocally movable by pressure exerted on the second plunger by the working fluid and arranged to exert force on a valve. 
         [0008]    According to an exemplary embodiment, the casing has an inverted U-shape with the first and second openings located within legs of the inverted U-shape. 
         [0009]    The casing can also include a valve opening control comprising a third opening in the casing and a control piston slidably fit within the third opening. The control piston is operable by the control to selectively displace working fluid to adjust the movement of the second plunger in reaction to movement of the first plunger. This capability can allow for variable valve lift (opening) control to improve combustion, or to open exhaust valves for engine braking. 
         [0010]    The valve opening control comprises a control operator, connected to the control piston and operable by the valve opening control to position the control piston within the third opening. 
         [0011]    The exemplary embodiments for operating an engine valve provides: 
         [0012]    a means for holding a working fluid; 
         [0013]    a first plunger means movable into and out of the means for holding the working fluid; 
         [0014]    a second plunger means movable into and out of the means for holding the working fluid, the second plunger means for exerting a force on a valve to open the valve; wherein 
         [0015]    the first plunger means selectively movable into the means for holding the working fluid to exert pressure on the second plunger means to move the second plunger means out of the means for holding the working fluid. 
         [0016]    The embodiments can also provide a third plunger means selectively movable into the means for holding the working fluid, the third plunger means for selectively displacing working fluid within the means for holding to adjust movement of the second plunger means. 
         [0017]    The third plunger means can adjust the displacement of the second plunger means in response to the movement of the first plunger means. 
         [0018]    The working fluid for the exemplary embodiments can be an oil or a gas, such as air. 
         [0019]    Numerous other advantages and features of the present invention will be become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a top perspective view of a prior art rocker carrier with rocker arm assemblies mounted thereon; 
           [0021]      FIG. 2  is a schematic sectional view of a rocker device according to a first exemplary embodiment of the invention; and 
           [0022]      FIG. 3  is a schematic sectional view of a rocker device according to a second exemplary embodiment of the invention. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0023]    While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
         [0024]      FIG. 1  shows a perspective view of a prior art rocker carrier  1100  as described more completely in U.S. Pat. No. 6,484,683, herein incorporated by reference. The rocker carrier  1100  is adapted to preferably be used on one side or bank of a V-8 type engine. 
         [0025]      FIG. 1  shows a plurality of rocker arm assemblies  1205 ,  1210  and  1217  mounted on the rocker arm pedestals and attached by hold down bolts  1236 ,  1237  and  1241 . The rocker arm assemblies  1205 ,  1210  and  1217  have rocker arms  1207 ,  1209 ,  1211 ,  1219  that will actuate valve bridges (not shown) when actuated by push rods (not shown) at appropriate times.  FIG. 1  shows that two types of rocker arm assemblies  1205 ,  1210  and  1217  are preferably used with the rocker carrier  1100 , though other appropriate configuration may be used as well. 
         [0026]    There is shown three dual rocker arm assemblies  1210  which cooperatively support a dual fulcrum plate  1212 . The dual fulcrum plates  1212  will each hold an intake and exhaust rocker arm  1209  and  1211 . In a preferred embodiment, the intake and exhaust rocker arms  1209  and  1211  on the dual fulcrum plates  1212  will operate valves on different engine cylinders. During intake, when the dual rocker arm assemblies  1210  operate, the intake rocker arms  1211  will appropriately actuate corresponding intake valves (not shown) via an intake valve bridge (not shown). During exhaust, when the dual rocker arm assemblies  1210  operate, the exhaust rocker arms  1209  will appropriately actuate corresponding exhaust valves (not shown) via an exhaust valve bridge (not shown). 
         [0027]    There is also shown a first and second end rocker arm assembly  1205  and  1215  in the rocker carrier  1100  which are adjacent to the first 15 and second 20 end walls which have a first and second end fulcrum plate  1203  and  1217 . The first end fulcrum plate  1203  will preferably hold an intake rocker arm  1207 . During intake, when the first end rocker arm assembly  1205  operates, the intake rocker arm  1207  will appropriately actuate corresponding intake valves (not shown) via an intake valve bridge (not shown). The second end fulcrum plate  1217  will preferably hold an exhaust rocker arm  1219 . During exhaust, when second end rocker arm assembly  1215  operates, the exhaust rocker arm  1219  will appropriately actuate corresponding exhaust valves (not shown) via an exhaust valve bridge (not shown). 
         [0028]      FIG. 2  illustrates a first exemplary embodiment valve actuation system  100  of the invention for use within an engine. The valve actuation system would replace the rocker arm assemblies shown in  FIG. 1 . According to this embodiment, a cam  106  formed on a camshaft  110  is driven in rotation in the direction “R” by a crankshaft (not shown) of the engine. The camshaft is driven in a known way by a chain or belt or gears. Spaced from the cam  106  is a valve assembly  112 . 
         [0029]    Although only one cam  106  and one valve actuation system  100  is shown, it should be understood that in practice plural cams  106  would be formed on the camshaft  110  and the cams would operate plural valve actuation systems  100 , one for each valve, both intake and exhaust. 
         [0030]    The valve assembly  112  includes a valve element  118  disposed in a cylinder head  120  of the engine. The valve assembly  112  may be an intake valve, an exhaust valve, or the like. The cylinder head  120  forms a passageway  122  that extends to a cylinder through a valve opening  124  defined by a valve seat  126 . The valve element  118  includes a valve stem  128  connected to a valve head  130 . A biasing device  132  is disposed on the valve stem  128 . The biasing device  132  applies a biasing force to hold the valve head  130  against the valve seat  126 —a closed position. The biasing device  132  may be a hydraulic spring, a mechanical spring, or the like. 
         [0031]    The actuation system  100  may include a casing  134  that is fixedly mounted to the cylinder head  120 . The casing  134  has a confined internal passage  138  having a first opening  140  into a first cylinder portion  141  and having a first inside diameter “D 1 ” and a second opening  142  into a second cylinder portion  143  and having a second inside diameter “D 2 .” A first plunger or lifter  150  is sealingly fit within the cylinder portion  141  and rides on the cam  106  either directly as shown or by way of an interposed push rod (not shown) between the lifter  150  and the cam  106 . When a lobe  106   a  of the cam extends upward, the lifter is driven upward into the cylinder portion  141 . A second plunger or pin  144  is sealingly disposed in internal passage  138 , within the cylinder portion  143 . The pin  144  engages the valve stem  128  outside of the cylinder portion  143 . The engagement can be a connection or merely an abutment or contact at an interface  156 . 
         [0032]    To open the valve assembly  112 , the cam rotates and the lobe  106   a  drives the lifter  150  into the cylinder  141 , shown in dotted line as an upward position  150   a , by a distance X 1 . The passage  138  is filled with a substantially non-compressible working fluid  152 , such as engine oil, another hydraulic fluid, or the like. It is also possible that the working fluid is a gas, such as pressurized air. A pressure is generated within the working fluid by upward movement of the lifter  150  and the resistance of the biasing device  132 . The pressure is sufficient to drive the pin  144  down, by a distance X 2  to press the valve stem  128  down, overcoming the force of the biasing device  132 , to move the valve head  130  off of (below) the seat  126 . 
         [0033]    To close the valve, after the lobe  106   a  rotates beyond the lifter  150 , the lifter is lowered and the pin  144  is forced upward by force from the biasing device  132  via the valve stem. 
         [0034]    The relationship of movement of the pin  144  with the movement of the piston  256  and the lifter  150  can be expressed as follows: 
         [0000]        X   2 =( D   i   /D   2 ) 2   X   1          where X 2  is the distance the pin travels, and   X 1  is the distance the lifter travels.
 
If the pin  144  has a smaller diameter than the lifter, the pin will travel a greater distance for a given distance of movement of the lifter.
         
         [0037]      FIG. 3  illustrates a second exemplary embodiment of the invention, a valve actuation device  200 . Items that are identically numbered as in the first embodiment are configured substantially the same. The device  200  may include a casing  234  that is fixedly mounted to the cylinder head  120 . The casing  234  has a confined internal passage  238  having the first opening  140  into the first cylinder portion  141  and having the first inside diameter “D 1 ” and the second opening  142  into the second cylinder portion  143  and having the second inside diameter “D 2 .” When a lobe  106   a  of the cam extends upward, the lifter is driven upward into the cylinder  141 . The pin  144  engages the valve stem  128  outside of the cylinder portion  143 . 
         [0038]    To open the valve assembly  112 , the cam rotates and the lobe  106   a  drives the lifter  150  into the cylinder  141 , shown in dotted line as the upward position  150   a , by the distance X 1 , which is the maximum stroke. The passage  238  is filled with the substantially non-compressible working fluid  152 , such as engine oil, another hydraulic fluid, or the like. A pressure is generated within the working fluid by upward movement of the lifter  150  and the resistance of the biasing device  132 . The pressure is sufficient to drive the pin  144  down a distance X 2  to press the valve stem  128  down, overcoming the force of the biasing device  132 , to move the valve head  130  off of the seat  126 . 
         [0039]    To close the valve, after the lobe  106   a  rotates beyond the lifter  150 , the lifter is lowered and the pin  144  is forced upward by force from the biasing device  132  via the valve stem. 
         [0040]    The second embodiment also includes a valve opening control  250 . The control includes an operator  254  that interacts with a displacement control plunger or piston  256 . The operator  254  can be connected to the piston  256  or merely abut or contact the piston. The operator can be moved or allowed to move by an electro-mechanical actuator or by selectably pressurized hydraulic fluid, such as described in U.S. Pat. No. 6,779,506, herein incorporated by reference. Alternatively, the operator can be controlled in movement by other pneumatic or electric motors or actuators. 
         [0041]    The displacement control piston  256  is sealingly and slidingly fit into a hole  260  and into a third cylinder portion  262  of the casing  234  that has an inside diameter “D 3 .” The displacement control piston can be used to increase or lessen the displacement X 2  of the pin  144  given a displacement X 1  of the lifter and thus the amount of opening of the valve, according to the amount of movement X 3  of the displacement control piston  256  within the third cylinder portion  262 . This controlled movement of the valve head caused by the movement of the control piston  256  is independent of, but adds to, or subtracts from, the controlled movement of the valve head controlled by movement of the lifter  150  alone. 
         [0042]    According to one mode of operation, the operator can be set in a default position. If the operator  254  allows the piston  256  to move up a preselected or controlled gap or amount, the distance X 3 , when the cam forces the lifter  150  upward by the distance X 1 , the resultant movement X 2  of the pin  144  is reduced. If the operator  254  moves the piston  256  downward a preselected or controlled amount X 3 , when the cam forces the lifter  150  upward by the distance X 1 , the resultant movement X 2  of the pin  144  is increased. This control using can be undertaken to improve combustion during certain operating modes 
         [0043]    According to another mode of operation, the operator  254  can move the control piston  256  inward (downward), the distance X 3 , to drive the pin  144  down to press the valve stem  128  down, overcoming the force of the biasing device  132 , to move the valve head  130  off of the seat  126 . 
         [0044]    According to this mode, the control  250  can be used to facilitate engine braking. Engine braking is described more completely in U.S. Pat. No. 6,779,506, herein incorporated by reference. The engine brake system takes advantage of the individual exhaust valve assemblies  112  at individual cylinders. By operating an internal mechanism of a turbocharger, such as turbocharger vanes, to create a certain restriction on the flow through the exhaust system, and at the same time, forcing exhaust valve assemblies  112  to be open to some extent, the kinetic energy of the moving motor vehicle operates the engine like a pump that forces contents of the engine cylinders through the created restriction. Such forced dissipation of the kinetic energy of the vehicle slows the vehicle. 
         [0045]    Each exhaust valve assembly  112  is forced open by a respective operator  254  of the engine brake system moving downward according to  FIG. 3 . When the exhaust valves are not being forced open by operators  254 , they operate at proper times during the engine cycle to allow products of combustion to exit cylinders and pass into exhaust system. 
         [0046]    The relationship of movement of the pin  144  with the movement of the piston  256  and the lifter  150  can be expressed as follows: 
         [0000]        X   2 =( D   i   /D   2 ) 2   X   1 −( D   3   /D   2 ) 2   X   3  
       where X 2  is the distance the pin travels,   X 1  is the distance the lifter travels, and   X 3  is the distance the piston travels.       
 
         [0050]    From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred.