Abstract:
An apparatus for controlling valve displacement of an internal combustion engine comprises a rocker arm having a first arm portion and a second arm portion, said rocker arm being pivotable about a pivot interposed between said first and second arm portions. The apparatus further comprises an actuation arrangement adapted to actuate said first arm portion of said rocker arm and a valve arrangement adapted to be actuated by said second arm portion of said rocker arm. A damper arrangement is pivotably connected to said first arm portion and adapted for damping movement of said rocker arm around said pivot.

Description:
CROSS-REFERENCE 
     The present application claims priority to European patent application No. 07021291.5, filed 31 Oct. 2007, which is incorporated herein by reference as if fully set forth herein, and is the national stage of PCT/EP2008/009183, filed Oct. 30, 2008. 
     TECHNICAL FIELD 
     The present disclosure relates to an apparatus for controlling valve displacement of an internal combustion engine and, more particularly, to an apparatus for adjusting or delaying the closing of inlet valves of an internal combustion engine, in particular diesel and gasoline engines. 
     BACKGROUND 
     In order to reduce NOx emissions from diesel and gasoline engines, it is known to use the “Miller process” to cool or reduce the combustion temperature. According to this process, a cooling effect is achieved by closing the intake valves very early. The subsequent expansion of the volume of gas in the combustion chamber lowers the temperature of the fresh gas mixture and the cylinder filling loss of the charged engine is compensated by an increased charging pressure generated by a turbocharger. 
     For transient engine conditions, in which the loaded engine must generate increased power/torque within a short time, shutting-off the Miller process is very helpful. This can be achieved by displacing the inlet cam profile by rotating the cam shaft relative to the crankshaft or by displacing the cam on the cam shaft or by modifying the coupling of the cam/valve. In all cases, a valve-opening overlap and thus evacuation of the cylinders is reduced by displacing the cam profile. 
     In EP 1 477 638 A1A, a device for variably controlling the opening and/or closing of inlet and/or exhaust valves of an internal combustion engine of the above-mentioned type is disclosed. This known device is adapted to delay the closing of inlet valves of an internal combustion engine, and includes a damping device integrated in a guide rod for guiding a valve actuation bridge during its up and down motion. Hence, the damping device is an integrated part of the valve actuation bridge. More particularly, in this known device, an annular recess is disposed between a guide rod of a piston and a cylinder sleeve. The annular recess is in fluid communication with an axial bore axially extending within the guide rod via a transverse bore. One end of a tap bore opens or discharges into the axial bore of the guide rod. The other end of the tap bore is in fluid communication with valve units via oil-supply lines. More particularly, the tap bore is connectable with a lubricating oil-supply port as a function of the valve position of the gas exchange valves either via a first oil-supply line controlled by a valve unit, which includes a passage and shutoff valve, or via a second oil-supply line controlled by a second valve unit, which includes a one-way valve and a throttle. Thus, controlling of the gas exchange valves as a function of the closed position and/or the opened position can be achieved by means of the valve units having the correspondingly-designed valves. 
     When the gas exchange valves are closed, lubricating oil contained in the annular recess can be supplied into a further valve unit via the axial bore and the tap bore, as well as via an oil-supply line. In addition, when the valve is closed, the lubricating oil can be supplied into the valve unit having the throttle so that the intake valves will assume a delayed position. In contrast, when the gas exchange valves are in a delayed position, the free or terminal end of the rocker arm that is opposite of the valve actuation bridge is pivoted about the rotational axis towards the rocker arm by means of a telescoping member, which is spring-biased and guided in the push-rod, without any play or clearance therebetween. 
     However, the device disclosed in EP 1 477 638 A1 requires construction space between the two inlet and/or exhaust valves and its associated springs. Furthermore, due to the integration of the damping device in the guide rod of the valve actuation bridge, the known device requires a guide rod. 
     U.S. Pat. No. 3,520,287 discloses an exhaust valve control for an engine braking system which also includes an arrangement having a guide rod slidably mounted on a valve actuation bridge. The valve actuation bridge and the guide rod together define a hydraulic chamber that expands when the valve bride advances to open the exhaust valves and contracts when the valve actuation bridge retracts to permit the two exhaust valves to be closed by the exhaust valve springs. Again, a damping device is integrated into the guide rod and is part of the valve actuation bridge. Hence, like the above arrangement, a construction space between the two valves is necessary and this known assembly requires a guide rod. 
     U.S. Pat. No. 6,905,155 discloses an apparatus for limiting the travel of a slave piston in a slave piston cylinder in a compression release engine retarder. The apparatus is connected to a hydraulic circuit and an internal passageway is defined in the slave piston head. The internal passageway comprises a vertical bore, a horizontal bore and an annular channel which together define a path for bleeding off the pressure at the top of the slave piston when the annular channel and an aperture in the slave piston cylinder are aligned. By bleeding off the hydraulic pressure at top of the slave piston, the motion of the slave piston is restricted to a desired stroke. The apparatus includes a locking adjustable foot on the slave piston stem which provides a means for adjusting the lash. Here, the known arrangement for actuating at least one engine valve requires a minimum space above the valve actuation bridge and the rocker arm. 
     US 2005/0121008 A1 discloses a method and apparatus for controlling a temperature in a combustion cylinder in an internal combustion engine. A rocker arm is located to move about a pivot. A push-rod provides a mechanical force against the rocker arm. An electro-hydraulic assist actuator may include a plunger assembly for providing a hydraulic force used to vary the open duration of an intake valve. In particular, the electro-hydraulic assist actuator may be used to hold the intake valve open for a period of time longer than a cam is designed to do. The plunger assembly may be located at the same side of the rocker arm as the push rod. In addition, the plunger assembly is designed to provide a mechanical force during a first rotating direction of the rocker arm. A reverse rotating direction of the rocker arm has no impact on the plunger assembly. Consequently, the known plunger assembly may be relatively slow and the reaction time could be relatively long. 
     US 2003/0221644 A1 shows a similar engine valve actuation system including a fluid actuator configured to selectively prevent an intake valve from moving in a first position. 
     Other arrangements are known from, e.g., DE 102 39 750 A1, US 2005/0121637, US 2004/0065285 A1, WO 2004/005677 A1, WO 87/07677. 
     The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of prior devices and methods for controlling valves and, more particularly, of apparatus for adjusting or delaying the closing of inlet valves of an internal combustion engine. 
     SUMMARY OF THE DISCLOSURE 
     According to a first exemplary aspect of the present teachings, an apparatus for controlling valve displacement of an internal combustion engine comprises a rocker arm having a first arm portion and a second arm portion, said rocker arm being pivotable about a pivot interposed between said first and second arm portions. Said apparatus further comprises an actuation arrangement adapted to actuate said first arm portion of said rocker arm and a valve arrangement adapted to be actuated by said second arm portion of said rocker arm. A damper arrangement may be pivotably connected to said first arm portion and adapted for damping movement of said rocker arm around said pivot. 
     In a further exemplary embodiment of the disclosed apparatus said rocker arm may be pivotable about the pivot in a first rotating direction and a second rotating direction which is reverse to the first rotating direction. Said damper arrangement may be hydraulically operated by means of a hydraulic fluid and pivotably connected to said first arm portion so that movement in said first rotating direction of said rocker arm around said pivot is damped and during movement in said second rotating direction of said rocker arm said hydraulic fluid is sucked. The suction of the hydraulic fluid may be caused by the movement in said second rotating direction of said rocker arm and the pivotable or articulated or hinged connection of the damper arrangement to the rocker arm. 
     A further exemplary embodiment may comprise a push-rod adapted to be reciprocated, e.g. by a valve cam and a rotational drive, a rocker arm pivotable about a rotational axis, a valve actuation bridge and a damper arrangement adapted to damp the pivoting motion of the rocker arm during movement of valves, preferably during a closing of one or more of the engine valves. In this exemplary embodiment a first arm portion of the rocker arm extends from the rotational axis to a first free end of the rocker arm and a second arm portion of the rocker arm extends from the rotational axis to a second free end of the rocker arm opposite the first free end. The first arm portion of the rocker arm may be driven by the push-rod. The valve actuation bridge may be driven by the second arm portion of the rocker arm and may connect to respective valve shafts of the valves. The damping device acts on the first arm portion of the rocker arm driven by the push-rod. The valves may comprise one or more inlet valves and/or one ore more outlet valves. In one exemplary embodiment of the present teaching the damper arrangement causes a delay of the closing of inlet valves. 
     According to another exemplary aspect of the present teachings, a method of controlling at least one combustion chamber valve associated with a rocker arm may comprise rotating said rocker arm about a pivot interposed between first and second arm portions for actuating at least one combustion chamber valve and damping the rotation of said rocker arm with a damper arrangement jointly connected to said first portion of said rocker arm. According to a further exemplary embodiment of the disclosed method, the method may further comprise rotating said rocker arm about said pivot in a first rotating direction and simultaneously applying a force to said first arm portion of said rocker arm so that movement of said rocker arm around said pivot in said first pivoting direction is damped. Rotating the rocker arm about said pivot in a second rotating direction which is reverse to said first rotating direction may cause sucking said hydraulic fluid. 
     According to another exemplary aspect of the present teachings, a method of controlling at least one combustion chamber valve associated with a rocker arm may comprise rotating said rocker arm about a pivot interposed between first and second arm portions for actuating at least one combustion chamber valve and damping rotation of said rocker arm with a damper arrangement connected to said first portion of said rocker arm. 
     According to another exemplary aspect of the present teachings, an internal combustion engine comprises an apparatus for controlling valve displacement of said internal combustion engine. Said apparatus includes a rocker arm, said rocker arm being pivotable about a pivot interposed between first and second arm portions. Furthermore, an actuation arrangement for applying a force to said first arm portion of said rocker arm and a valve arrangement actuated by said second arm portion of said rocker arm are comprised. Finally, a damper arrangement is pivotably connected to said first arm portion and damps a movement of said rocker arm around said pivot. 
     As utilized herein, the terms “damping unit” and “damper arrangement” or similar terms used throughout the description are intended to cover any kind of apparatus/device that imparts a resistive decelerating force to the reciprocating movement of any kind of valves. 
     Representative, but not limiting, examples of suitable damper arrangements in accordance with the present teachings may include hydraulic and pneumatic cylinders, such as e.g. utilized for shock absorbing applications. In some embodiments, a spring or other resilient elastic materials or devices may be suitably utilized, particularly, if the elastic return force can be changed in operation. 
     Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings. 
     It is to be understood that forgoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an exemplary embodiment of the disclosure and, together with the description, serve to explain the principles of the disclosure. In the drawings, 
         FIG. 1  is a schematic illustration of a first preferred exemplary device for variably controlling the closing of inlet and/or exhaust valves of an internal combustion engine; 
         FIG. 2  is a schematic diagram of the hydraulic system connected to a damping unit as part of the exemplary device for variably controlling the closing of inlet and/or exhaust valves shown in  FIG. 1 ; 
         FIG. 3  is a perspective view of a second exemplary device for variably controlling the closing of inlet and/or exhaust valves of an internal combustion engine; 
         FIG. 4  is a side view of the device of  FIG. 3 ; 
         FIG. 5  is a sectional view of the device of  FIGS. 3 and 4 ; 
         FIG. 6  is a perspective view of a part of the device shown in  FIGS. 3-5 ; 
         FIG. 7  is a sectional view of the device of  FIG. 6 ; and 
         FIG. 8  is a sectional view along line VIII-VIII of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the exemplary embodiments of the present teachings, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. 
     Referring to  FIG. 1 , an exemplary device  100  for variably controlling the opening and/or closing of inlet and/or exhaust valves  180  of an internal combustion engine (not shown), for example, a four-stroke diesel engine, is provided. The valve control device  100  may include a rocker arm  110  that may be rotatable about a rotational axis  115 . The rocker arm  110  has a first arm portion  111  extending from the rotational axis  115  to a first free end  112  of the rocker arm  110 , and a second arm portion  113  extending from the rotational axis  115  to a second free end  114  of the rocker arm  110 . The second free end  114  is opposite the first free end  112  of the rocker arm  110 . 
     In addition, the valve control device  100  may include an actuation arrangement. This actuation arrangement may comprise a push-rod  120 . A free end  128  of the push-rod  120  may be in contact with the free end  112  of the rocker arm  110 . The push-rod  120  may be driven by any arrangement. In one exemplary embodiment the push-rod  120  may be driven by a valve cam (not shown) and a rotational drive (not shown). However, since such a drive device for of the push-rod  120  is well known, a detailed explanation of this kind of drive device is omitted. 
     As shown in  FIG. 1 , a valve actuation bridge  160  may be in contact with the second free end  114  of the rocker arm  110 . The valve actuation bridge  160  may have a guide rod  170  for guiding the valve actuation bridge  160  during up-and-down reciprocating motion for opening and/or closing the inlet and/or exhaust valves  180 . The valve actuation bridge might be omitted if e.g. only one valve is to be actuated. 
     The exhaust valves  180  may include valve discs  190  and valve shafts  185 . In one exemplary embodiment the valve shafts  185  are coupled with the valve actuation bridge  160 . A helical spring  165  may be arranged on each valve shaft  185  for urging the valve discs  190  towards respective valve seats  191  (see e.g.  FIG. 5 ). 
     Furthermore, the valve control device  100  may include a damper arrangement or damping unit  130  for applying a damping force to the first rocker arm portion  111  of the rocker arm  110  during pivoting of the rocker arm  110  in a first pivoting direction shown by arrow  210 . By pivoting of the rocker arm  110  in the first pivoting direction of the arrow  210 , the valves  180  may be forced towards their respective valve seats  191  (see  FIG. 5 ) and therefore in the direction for closing the valves  180 . The arrow  215  illustrates a second pivoting direction of the rocker arm  110  about the rotational axis  115  for opening the valves  180 , i.e. the valve discs  190  move away from their respective valve seats  191 . The damping unit  130  may include a piston  145  having a piston-rod  150 . In one exemplary embodiment the piston  145  is slidably supported in a housing  146 . The piston  145 , in combination with the housing  146 , may define a fluid chamber  140  which is in fluid communication via an oil-supply line  305  with a hydraulic system  300  schematically shown in  FIG. 2 . 
     In  FIGS. 2 and 3 , one exemplary embodiment the hydraulic system  300  is schematically shown. This hydraulic system  300  may be in fluid communication with the damping unit  130  of  FIG. 1 . The hydraulic system  300  may include a control valve or shut-off valve  310 , an throttle  315  and a check valve  320 . This elements  310 ,  315  and  320  may be arranged in parallel by fluid supply lines  305 ,  330 . In one exemplary embodiment the fluid supply lines  305 ,  330  may be adapted to supply oil and the throttle  315  may be adapted to be adjustable. As was already mentioned above, the supply line  305  may end in the fluid chamber  140  of the damper arrangement  130 . The supply line  305  may also connect with the shut-off valve  310 . In one exemplary embodiment the shut-off valve  310  may comprise a solenoid valve. It may be in fluid communication via the supply line  330  with a supply system  350  of the internal combustion engine. In one exemplary embodiment the supply system  350  may comprise a lubricating oil system. 
     The throttle  315  may connect with the supply line  305  and the oil-supply lines  330  and  340 . The check valve  320  may also connect with the supply lines  305 ,  330  and may be arranged parallel to the throttle  315 . Hence, the fluid, e.g. oil, can flow into a collecting reservoir  335  via a bleed line (also denotes as “blood-line”). The bleed line may be connected to the supply lines  330 ,  340 . Finally, the supply lines  305 ,  330  and, hence, the valve  310 , the throttle  315  and the check valve  320  are connected via the oil line  340  with e.g. the engine lubrication oil system  350  as is schematically illustrated. In  FIG. 3  an lubricating oil inlet and outlet port  340  are shown. 
     Referring now to  FIGS. 3-8 , an exemplary embodiment of a valve control device  100  is explained in more details. 
     As shown in  FIGS. 3 to 5 , the device  100  includes the push-rod  120  having a connecting part  122 , a telescoping device  124  for gap-compensating and a hollow rod member  126  closed by a cap  128 . Referring to  FIG. 5 , further details of the telescoping member  124  of the push-rod  120  will now be explained. In one exemplary embodiment, a rod part of the push-rod  120  is integral with the rod member  126  of the push-rod  120 . The outer diameter of the rod part may be greater than the outer diameter of the rod member  126  for accommodating a cylindrical sleeve  125 , which receives a helical spring  127  and a cap  123 . The spring  127  may rest on a ring-shaped projection  121  of the cylindrical sleeve  125 . On the opposite side of the helical spring  127 , the helical spring  127  urges against the cap  123 . The outer end of the cap  123  may be hemispherical. Due to the telescoping device  124 , any gap or play occurring during pivoting of the rocker arm  110  may be compensated. 
     As shown in  FIG. 3 , in one exemplary embodiment two valve bridges  160  are pivotably arranged above a cylinder head  101  having an air inlet  102  and a connecting flange  103  for mounting the cylinder head  101  at an engine housing (not shown). For illustration purposes, only one push-rod  120  is shown. However, the second rocker arm  110  may be, like the first rocker arm  110 , adapted to be driven by a push-rod  120 . The second rocker arm  110  acts on a further valve actuation bridge (not shown) which contacts a pair of outlet valves (not shown). The second rocker arm  110  may also preferably include a damping device  130  like the first rocker arm  110  as shown in  FIG. 3 . 
     The first rocker arm  110  may be pivotably arranged about an axis  115  and its free end  114  may contact the valve actuation bridge  160 . As can be seen in  FIGS. 3 and 4  and, in particular in  FIG. 5 , in one exemplary embodiment two inlet valves  180  are adapted to rest on the respective seat  191  in the cylinder head  101 . Each valve shaft  185  may be biased upwards by a valve spring  165 . The arrangement of the valves  180  and their respective contacts with the valve actuation bridge  160  is basically known and therefore, a detailed explanation thereof is omitted. 
     The damping unit  130  shown in  FIGS. 3-8  includes in one exemplary embodiment a guiding sleeve  146  sealingly arranged in the piston housing  143 . The piston-rod  150  may extend through the guiding sleeve  146  and may be adapted to reciprocate within the guiding sleeve  146 . A seal  151  arranged in the inner circumference of the guiding sleeve  146  may contact the outer surface of the piston-rod  150  such that an oil-leakage is prevented. As shown for example in  FIG. 6 , a joint  410  may be provided on the end  152  of the piston-rod  150 . At this joint  410 , a forked lever  400  may be rotatably connected to the piston-rod end  152 . The forked lever  400  may have two fork parts  411 . A bearing member  117  of the rocker arm  110  may be arranged between the two spaced apart fork parts  411 . At this point, a joint connection  405  may be provided between the rocker arm  110  and fork parts  411 . Due to this arrangement, the reciprocating motion of the piston-rod  150  may be transferred to the rocker arm  110  such that the rocker arm  110  rotates about the rotational axis  115 . 
     A more detailed illustration of the assembly of the damping unit  130  and the rocker arm  110  is provided in  FIGS. 6-8 . As shown, in one exemplary embodiment the piston housing  143  includes the guiding sleeve  146 . The end of the piston-rod  150  may extend through the guiding sleeve  146 . The forked lever  400  may be rotatably connected to the end of the piston-rod  152  as well as to the first arm portion  111  of the rocker arm  110 . In  FIGS. 6 and 8 , the contacting members  116  of the two rocker arms  110  are shown, which contacting members  116  may contact the push-rod  120  (see  FIGS. 1 ,  3  and  4 ). The second free end  114  of the second arm portion  113  may have a contacting member  161 , which in one exemplary embodiment is part of the rocker arm  110  or of the valve actuation bridge  160 . 
     INDUSTRIAL APPLICABILITY 
     Referring to  FIGS. 1 and 2 , an exemplary embodiment of a method for operating the exemplary embodiment of an apparatus  100  for variable controlling at least one engine valve  180  shown e.g. in  FIGS. 3-8  will now be explained. 
     During normal operation, the push-rod  120  is actuated by a valve cam and a rotational drive (both not shown), thereby rotating the rocker arm  110  around the rotational axis  115 . During the upward movement of the push-rod  120 , the rocker arm  110  is urged to rotate around rotational axis  115  as indicated by arrow  215 . As a result, the valve actuation bridge  160 , which is vertically movably supported by the guide rod  170 , is being pivotably displaced or rotated against the biasing force of the valve springs  165  and the two intake valves  180  open in parallel, i.e. the valve discs  190  move away from the respective valve seats  191 , as shown in  FIG. 5 . Consequently, during the downward movement of the valve actuation bridge  160 , the piston-rod  150  of the damping unit  130  is urged to move upwards due to the joint connection with the first arm portion  111  of the rocker arm  110  via the forked lever  400 . At the same time, the volume of the fluid chamber  140  increases and pressurized motor lubricating oil fills this increasing volume in an unthrottled manner via the oil-supply line  305  and the shut-off/passage valve  310 , because the check valve  320  is opened in the filling direction and the shut-off/passage valve  310  is in the position shown in  FIG. 2 . As a result, the pivoting of the rocker arm  110  in the direction indicated by arrow  215  may not delayed. In particular, the positive connection, e.g., the pivot connection or hinge connection with the rocker arm  110  via, e.g., the lever  400  may generate a suction effect in the fluid chamber  140  for at least assisting the filling process of the fluid chamber  140  with fluid. Consequently, the filling process of the chamber with hydraulic fluid may be improved. In another exemplary embodiment the pivoting of the rocker arm  110  in the direction indicated by arrow  215  may be delayed with the aid of the damper arrangement  130 . 
     The biasing force of the valve springs  165  may cause the valves  180 , the valve actuation bridge  160 , the rocker arm  110 , the push-rod  120  to remain in series connection during this time. 
     The closing of the intake valves  180  may be initiated when the not-illustrated rotational drive and the push-rod  120  move downward in accordance with the further rotation of the not-illustrated cam profile. At this time, the valve actuation bridge  160  may be displaced upward by e.g. the biasing force of the valve springs  165 , whereby the volume in the fluid chamber  140  may be reduced and the lubricating oil located in the fluid chamber  140  is discharged to the lubricating oil-supply system  350  via the oil-supply lines  305  and  340  in an unthrottled throttle manner via the opened shut-off/passage valve  310 . On the other hand, when the shut-off/passage valve  310  is closed, i.e. in the shut-off position during the closing motion of the intake valves  180 , the discharge of the lubricating oil from the fluid chamber  140  no longer takes place in an unthrottled manner via the shut-off/passage valve  310 . Instead, the lubricating oil may be discharged via the throttle  315 . Consequently, the upward movement of the valve actuation bridge  160  may be hindered, damped or delayed because the cross section of the throttle  315  is restricted. As a result, in one embodiment the upward stroke of the valve actuation bridge  160  and, consequently, the closing of the intake valves  180  may be damped/delayed by e.g. reducing the throttle cross section of the throttle  315 . 
     Due to the arrangement and construction explained above and shown in the figures, in one exemplary embodiment a predetermined damping of the closing of the inlet and/or exhaust valves  180  can be achieved. Contrary to the known art, in which the delay device is integrated in the valve actuation bridge and the associated guide rod, the presently preferred embodiment maybe used for e.g. two and/or e.g. four valve cylinder heads with or without a guide-rod because in one exemplary embodiment the damper arrangement is disposed on the same side of the rocker arm  110  as the push-rod  120 . Therefore, in one exemplary embodiment the damper arrangement  130  may be installed independently of the structure and design of the valve actuation bridge. A further advantage may be that maintenance of the valve control devices  100  is easier than of prior art devices, because in one exemplary embodiment for example the damper arrangement may be replaced without substantial disassembly. 
     Although the preferred embodiments of this disclosure have been described herein, improvements and modifications may be incorporated without departing from the scope of the following claims.