Abstract:
The present invention is directed to an apparatus for operating at least one intake valve and at least one exhaust valve in an engine cylinder. The apparatus includes an exhaust valve operating assembly for operating the at least one exhaust valve of the engine cylinder, wherein the exhaust valve operating assembly is capable of producing an exhaust gas recirculation event. The apparatus also includes an intake valve operating assembly for operating the at least one intake valve of the engine cylinder. The apparatus further includes an exhaust modifying assembly for modifying the operation of the exhaust valve operating assembly during a predetermined engine operating condition and an intake modifying assembly for modifying the operation of the intake valve operating assembly during a predetermined engine operating condition.

Description:
CROSS REFERENCE TO RELATED PATENT APPLICATION 
     This application relates to and claims priority on provisional application serial No. 60/129,253, filed Apr. 14, 1999. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to the control of exhaust and intake valves during positive power and engine braking. In particular, the present invention is directed to an assembly to modify the valve lift and timing of the exhaust valve and/or intake valve during positive power and different operating conditions during positive power. 
     BACKGROUND OF THE INVENTION 
     It has been published that an exhaust event with an internal hot exhaust gas recirculation (“EGR”) event is beneficial in controlling emissions by directing a small amount of the exhaust gas back into the valve cylinder to mix with intake air. The combined intake and exhaust gas with the depleted oxygen helps create a lower burn temperature, which helps reduce the generation of nitrogen oxides. There are, however, certain positive power conditions during which the EGR event does not add any benefit. These conditions include a light load and low engine rpm. The EGR event also does not provide any benefit during engine braking where the EGR event reduces braking power. Therefore, it is desirable to have the EGR event to be selectable, on as desired during positive power and off during braking. 
     OBJECTS OF THE INVENTION 
     It is an object of the present invention to provide a device for an engine that can change the intake valve lift of an intake valve. 
     It is another object of the present invention to provide a device for an engine that can change the timing of the intake valve. 
     It is another object of the present invention to provide a device for an engine that can change the timing of the intake valve to improve emission and fuel economy. 
     It is another object of the present invention to provide a device for an engine that can advance or retard the timing of the intake valve to improve emission and fuel economy. 
     It is another object of the present invention to provide a device for an overhead cam diesel engine that can change the intake valve lift of the intake valve. 
     It is another object of the present invention to provide a device for an overhead cam diesel engine that can change the timing of the intake valve. 
     It is an object of the present invention to provide a device for an engine that can change the exhaust valve lift of an exhaust valve. 
     It is another object of the present invention to provide a device for an engine that can change the timing of the exhaust valve. 
     It is another object of the present invention to provide a device for an engine that can change the timing of the exhaust valve to improve emission and fuel economy. 
     It is another object of the present invention to provide a device for an engine that can advance or retard the timing of the exhaust valve to improve emission and fuel economy. 
     It is another object of the present invention to provide a device for an overhead cam diesel engine that can change the exhaust valve lift of the exhaust valve. 
     It is another object of the present invention to provide a device for an overhead cam diesel engine that can change the timing of the exhaust valve. 
     It is another object of the present invention to provide a device for an engine that permits the exhaust valve to operate with an EGR event when desired. 
     It is another object of the present invention to provide a device for an engine that permits an EGR event during selected operating conditions during positive power. 
     It is another object of the present invention to provide a device for an engine that does not permit an EGR event during engine braking. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an apparatus for operating at least one intake valve and at least one exhaust valve in an engine cylinder. The apparatus according to an embodiment of the present invention includes an exhaust valve operating assembly for operating the at least one exhaust valve of the engine cylinder, wherein the exhaust valve operating assembly is capable of producing an exhaust gas recirculation event. The apparatus further includes an intake valve operating assembly for operating the at least one intake valve of the engine cylinder, and exhaust modifying assembly for modifying the operation of the exhaust valve operating assembly during a predetermined engine operating condition. 
     In accordance with the present invention, the exhaust modifying assembly modifies the timing of the at least one exhaust valve during the predetermined engine operating condition. The predetermined engine operating condition is at least one of a first positive power operating condition, a second positive power operating condition and an engine braking condition. 
     In accordance with the present invention, the exhaust modifying assembly also modifies the lift of the at least one exhaust valve during the predetermined engine operating condition. The predetermined engine operating condition is at least one of a first positive power operating condition, a second positive power operating condition and an engine braking condition. 
     The exhaust valve operating assembly may include an exhaust rocker arm assembly pivotably mounted on a rocker shaft. The exhaust modifying assembly may include a hydraulic assembly in communication with the rocker shaft for controlling the operation of the at least one exhaust valve. The exhaust modifying assembly may further include a lash adjuster assembly on the exhaust rocker arm. The exhaust modifying assembly may further include a releasable assembly for releasably engaging a slot within the rocker shaft during the predetermined engine operating condition, wherein the releasable assembly controls the rotation of the exhaust rocker arm to modify at least one of the lift and timing of the at least one exhaust valve. The releasable assembly inhibits the operation of the lash adjuster assembly when the releasable assembly is located within the slot. Furthermore, the releasable assembly inhibits the exhaust gas recirculation event when the releasable assembly is received within the slot. 
     The apparatus according to another embodiment of thee present invention includes an exhaust valve operating assembly for operating the at least one exhaust valve of the engine cylinder, an intake valve operating assembly for operating the at least one intake valve of thee engine cylinder, and an intake modifying assembly for modifying the operation of the intake valve operating assembly during a predetermined engine operating condition. 
     In accordance with the present invention, the intake modifying assembly may modify the timing of the at least one intake valve during the predetermined engine operating condition. The predetermined engine operating condition is at least one of a first positive power operating condition, a second positive power operating condition and an engine braking condition. 
     In accordance with the present invention, the intake modifying assembly may further modify the lift of the at least one intake valve during the predetermined engine operating condition. The predetermined engine operating condition is at least one of a first positive power operating condition, a second positive power operating condition and an engine braking condition. 
     The intake valve operating assembly may include an intake rocker arm assembly pivotably mounted on a rocker shaft. The intake modifying assembly may include a hydraulic assembly in communication with the rocker shaft for controlling the operation of the at least one intake valve. The intake modifying assembly may further include a lash adjuster assembly on the intake rocker arm. The intake modifying assembly further includes a releasable assembly for releasably engaging a slot within the rocker shaft during the predetermined engine operating condition, wherein the releasable assembly controls the rotation of the intake rocker arm to modify at least one of the lift and timing of the at least one intake valve. The releasable assembly inhibits the operation of the lash adjuster assembly when the releasable assembly is located within the slot. 
     The present invention also is directed to an apparatus for operating at least one intake valve and at least one exhaust valve in an engine cylinder. The apparatus may include an exhaust valve operating assembly for operating the at least one exhaust valve of the engine cylinder, wherein the exhaust valve operating assembly is capable of producing an exhaust gas recirculation event. The apparatus also includes an intake valve operating assembly for operating the at least one intake valve of the engine cylinder. The apparatus may further include an exhaust modifying assembly for modifying the operation of the exhaust valve operating assembly during a predetermined engine operating condition and an intake modifying assembly for modifying the operation of the intake valve operating assembly during a predetermined engine operating condition. 
     The exhaust modifying assembly may modify the timing and lift of the at least one exhaust valve during the predetermined engine operating condition. The predetermined engine operating condition is at least one of a first positive power operating condition, a second positive power operating condition and an engine braking condition. 
     The intake modifying assembly may modify the timing and lift of the at least one intake valve during the predetermined engine operating condition. The predetermined engine operating condition is at least one of a first positive power operating condition, a second positive power operating condition and an engine braking condition. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated herein by reference, and which constitute a part of this specification, illustrate certain embodiments of the invention and, together with the detailed description, serve to explain the principles of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described in connection with the following figures in which like reference numbers refer to like elements and wherein: 
     FIG. 1 is a graph depicting exhaust and intake valve lift during various engine operating conditions during positive power and engine brakings; 
     FIG. 2 is a top view of the arrangement of the rocker arm assemblies and the intake and exhaust valve assemblies in accordance with the present invention; 
     FIG. 3 is a schematic view of the exhaust rocker arm in accordance with the present invention; 
     FIG. 4 is a partial schematic view of the exhaust rocker arm of FIG. 3 with control valve in a position to preclude an EGR event; 
     FIG. 5 is a partial exploded view of the exhaust rocker arm of FIG. 3 depicting the control valve positioned within a slot in the common rocker shaft during engine braking and a first positive power operating condition; 
     FIG. 6 is a partial exploded view of the exhaust rocker arm of FIG. 3 depicting the control valve positioned outside the slot in the common rocker shaft during a second positive power operating condition; 
     FIG. 7 is a schematic view depicting the exhaust, intake and braking valve assemblies in connection with the common rocker shaft; 
     FIG. 8 is a schematic view of the intake rocker arm in accordance with the present invention; 
     FIG. 9 is another schematic view of the intake rocker arm in accordance with the present invention; and 
     FIG. 10 is a schematic view of the braking rocker arm in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to a preferred embodiment of the present invention, an example of which is illustrated in the accompanying drawings. FIG. 2 illustrates a top view of the present invention in an overhead cam diesel engine. An intake rocker arm  30 , an exhaust rocker arm  40  and a braking rocker arm  20  are pivotably mounted on and spaced along a rocker shaft  50 . The intake rocker arm  30  is adapted to engage an intake valve crosshead  300  for at least one intake valve to operate the at least one intake valve. The exhaust rocker arm  40  is adapted to engage an exhaust valve crosshead  400  for at least one exhaust valve to operate the at least one exhaust valve during predetermined operating conditions. The braking rocker arm  20  is also adapted to engage the crosshead  400  to operate the at least one exhaust valve during an engine braking operation. 
     The rocker arms  20 ,  30  and  40  are spaced along a common rocker shaft  50  having at least two passages formed therein. The rocker shaft  50  has a passage  51  through which a supply of controlled engine oil or other suitable hydraulic fluid flows therethrough to exhaust rocker arm  40  on demand. A valve assembly  510  controls the flow of engine oil to the exhaust rocker arm  40 . The valve assembly  510  is preferably a solenoid valve. It, however, is contemplated by the inventors of the present invention that other suitable valves may be substituted and are considered to be within the scope of the present invention. The valve assembly  510  may be located on one of the rocker shaft  50 , the engine or the exhaust rocker arm  40 . 
     The rocker shaft  50  has a passage  52  through which a supply of controlled engine oil or other suitable hydraulic fluid flows therethrough to the intake rocker arm  30 . A valve assembly  520  controls the flow of engine oil to the intake rocker arm  30 . The valve assembly  520  is preferably a solenoid valve. It, however, is contemplated by the inventors of the present invention that other suitable valves may be substituted and are considered to be within the scope of the present invention. The valve assembly  520  may be located on one of the rocker shaft  50 , the engine or the intake rocker arm  30 . 
     The rocker shaft  50  has a passage  53  through which a supply of controlled engine oil or other suitable hydraulic fluid flows therethrough to braking rocker arm  20  on demand. A valve assembly  530  controls the flow of engine oil to the braking rocker arm  20 . The valve assembly  530  is preferably a solenoid valve. It, however, is contemplated by the inventors of the present invention that other suitable valves may be substituted and are considered to be within the scope of the present invention. The valve assembly  530  may be located on one of the rocker shaft  50 , the engine or the braking rocker arm  20 . 
     The rocker shaft  50  has a passage  54  through which a supply of engine oil or other suitable hydraulic fluid flows therethrough to lubricate the rocker arms  20 ,  30  and  40  to enable smooth pivotable movement of the rocker arms  20 ,  30  and  40  about common rocker shaft  50 . 
     The rocker arms  20 ,  30  and  40  correspond to a cam shaft  10  having three spaced cam lobes  12 ,  13 , and  14 . Exhaust cam lobe  14  corresponds to the exhaust rocker arm  40 . An EGR bump  11  also corresponds to the exhaust rocker arm  40 . Intake cam lobe  13  corresponds to an intake rocker arm  30 . Brake cam lobe  12  corresponds to a brake rocker arm  20 . 
     The exhaust rocker arm  40 , as shown in FIG. 3, is rotatably mounted on the common rocker shaft  50 . A first end of the exhaust rocker arm  40  includes an exhaust cam lobe follower  41 . The exhaust cam lobe follower  41  preferably includes a roller follower that is adapted to contact the exhaust cam lobe  14  and the EGR bump  11 . A second end of the exhaust rocker arm  40  has a lash adjuster  42 . The lash adjuster  42  is adjacent to a crosshead  400 . The lash adjuster  42  is described in detail below. The crosshead  400  is preferably a bridge device that is capable of opening two exhaust valves simultaneously. The exhaust rocker arm  40  also includes a control valve  43 . The control valve  43  is in communication with a fluid passageway  44  that extends through the exhaust rocker arm  40  to the lash adjuster  42 . The control valve  43  is also in communication with a fluid passageway  511  in common rocker shaft  50  that extends between the control valve  43  and supply passage  51  of the common rocker shaft  50 . The fluid passageway  511  terminates at a control slot  512 . The control valve  43  is capable of being received within the control slot  512 . 
     As discussed above, the lash adjuster  42  is located on one end of the exhaust rocker arm  40 . The lash adjuster  42  includes a screw assembly  421  that permits manual adjustment of the lash. A desired lash may be set by rotating the screw assembly  421 . A spring assembly  422  surrounds the screw assembly  421 , as shown in FIG.  3 . One end of the spring assembly  422  contacts an end of the screw assembly  421 . An opposite end contacts a lash piston assembly  423 , as shown in FIG. 3. A portion of the screw assembly  421  and the spring assembly  422  are received within a cavity within the piston assembly  423 . A free end of the piston assembly  423  includes a pin  424  for contacting the crosshead  400 . When the passageway  44  is filled with hydraulic fluid, hydraulic fluid then fills the cavity in the piston assembly  423 . The piston assembly  423  moves downward against the bias of the spring assembly  422  such that the pin  424  contacts the crosshead  400 . It, however, is contemplated by the inventor of the present invention that other suitable lash adjusters including, but not limited to, electronically operated lash adjusters and mechanically operated adjusters may be substituted for the above described hydraulic lash adjuster. These variations and modifications are considered to be within the scope of the present invention. 
     The intake rocker arm  30 , as shown in FIGS. 8 and 9, is rotatably mounted on the common rocker shaft  50 . A first end of the intake rocker arm  30  includes an intake cam lobe follower  31 . The intake cam lobe follower  31  is adapted to contact the intake cam lobe  13 . A second end of the intake rocker arm  30  has a lash adjuster  32 . The lash adjuster  32  has the same design as the lash adjuster  41  described above in connection with the exhaust rocker arm  40 . The lash adjuster  32  is adjacent to a crosshead  300 . The lash adjuster  32  is described in detail below. The crosshead  300  is also preferably a bridge device that is capable of opening two intake valves simultaneously. The intake rocker arm  30  also includes a control valve  33 . The control valve  33  is in communication with a fluid passageway  34  that extends through the intake rocker arm  30  to the lash adjuster  32 . The control valve  33  has the same construction as the control valve  43  described above in connection with the exhaust rocker arm  40 . The control valve  33  is also in communication with a fluid passageway  521  that extends between the control valve  33  and supply passage  52  of the common rocker shaft  50 . The fluid passageway  521  terminates at a control slot  522 . The control slot  522  is not shown in the embodiment of FIG.  9 . The control valve  33  is capable of being received within the control slot  522 . 
     The lash adjuster  32  has a similar construction to the lash adjuster  42 , discussed above. The lash adjuster  32  includes a screw assembly  321  that permits manual adjustment of the lash. A screw assembly  322  surrounds the screw assembly  321 . One end of the screw assembly  322  contacts an end of the screw assembly  321 . An opposite end contacts a lash piston assembly  323 . A portion of the screw assembly  321  and the spring assembly  322  are received within a cavity within the piston assembly  323 . A free of the piston assembly  323  includes a pin  324  for contacting the crosshead  300 . When the passageway  34  is filled with hydraulic fluid hydraulic fluid then fills the cavity in the piston assembly  323 . The piston assembly  323  moves downward against the bias of the spring assembly  322  such that the pin  324  contacts the crosshead  300 . It, however, is contemplated by the inventor of the present invention that other suitable lash adjusters including, but not limited to, electronically operated lash adjusters and mechanically operated adjusters may be substituted for the above described hydraulic lash adjuster. These variations and modifications are considered to be within the scope of the present invention. 
     The braking rocker arm  20 , as shown in FIG. 10, is rotatably mounted on the common rocker shaft  50 . The structure of the braking rocker arm  20  is similar to that disclosed in U.S. patent application Ser. No. 09/165,291, entitled “Improved Rocker Brake Assembly With Hydraulic Lock,” the disclosure of which is incorporated herein by reference. A first end of the brake rocker arm  20  includes a brake cam lobe follower  21 . The brake cam lobe follower  21  preferably includes a roller follower that is in contact with the brake cam lobe  12 . A second end of the brake rocker arm  20  has an actuator piston  22 . The actuator piston  22  is spaced from the crosshead  400  of thee exhaust rocker arm  40 . When activated, the brake rocker arm  20  and the actuator piston  22  contact the crosshead  400  to open the at least one exhaust valve. The brake rocker arm  20  also includes a control valve  23 . The valve  23  is in communication with a fluid passageway  24  that extends through the braking rocker arm  20  to the actuator piston  22 . The valve  24  is also in communication with a fluid passageway  531  that extends between the valve  24  and passage  53  of the common rocker shaft  50 . 
     OPERATION DURING POSITIVE POWER 
     In accordance with the present invention, there are at least two engine operating conditions during the positive power engine operating mode. The first operating condition during positive power occurs during light loads and low engine rpm, essentially when an EGR event does not provide any benefit. The second operating condition during positive power occurs when an EGR event is beneficial. 
     The operation of thee exhaust rocker arm  40  during the first operating condition during positive power will now be described. During the first operating condition, the valve assembly  510  is closed. Hydraulic fluid does not flow from the passage  51  to the exhaust rocker arm  40 . The control valve  43  remains within the control slot  512 , as shown in FIGS. 4 and 5. The range of movement of thee rocker arm  40  is limited to the size of the control slot  512 . Hydraulic fluid is not provided to the lash adjuster  42 . The lash adjuster  42  does not extend which reduces exhaust valve lift and delays exhaust valve timing, as shown in FIG.  1  by line C. Furthermore, the lift associated with the EGR bump  11  is absorbed so no EGR event is produced. 
     The operation of the intake rocker arm  30  during the first operating condition during positive power will now be described. During the first operating condition, the valve assembly  520  is closed. Hydraulic fluid does not flow from the passage  52  to the intake rocker arm  30 . The control valve  33  remains within the control slot  522 , as shown in FIG.  8 . The range of movement of the rocker arm  30  is limited to the size of the control slot  522 . Hydraulic fluid is not provided to the lash adjuster  32 . The lash adjuster  32  does not extend which reduces intake valve lift and delays intake valve timing, as shown in FIG. 1 by line E. 
     The operation of thee braking rocker arm  20  during the first operating condition during positive power will now be described. During the first operating condition, the valve assembly  530  is closed. The control valve  23  remains seated within the recess  532  of the rocker shaft  50 . The braking rocker arm  20  is disabled. The brake cam lobe follower  21  does not contact the braking lobe  12 . 
     The operation of the exhaust rocker arm  40  during the second operating condition during positive power will now be described. During the second operating condition, the valve assembly  510  is open. Hydraulic fluid flows from the passage  51  in the common rocker shaft  50 . The presence of hydraulic fluid within fluid passageway  511  and control slot  512  causes the control valve  43  to be biased out of the control slot  512 , as shown in FIGS. 3 and 6. The range of movement of the rocker arm  40  is not limited. Furthermore, hydraulic fluid is provided to the lash adjuster  42 , which extends to contact crosshead  400 . All movement of the rocker arm  40  when contacting exhaust cam lobe  14  is transferred to the crosshead  400  through the lash adjuster  42 . As such, there is no reduction in exhaust valve lift, as shown by line B in FIG.  1 . Furthermore, there is no delay in exhaust valve timing, as shown in FIG. 1 by line B. 
     The operation of the intake rocker arm  30  during the second operating condition during positive power will now be described. During the second operating condition, the valve assembly  520  is open. Hydraulic fluid flows from the passage  52  in the common rocker shaft  50 . The presence of hydraulic fluid within fluid passageway  521  and control slot  522  causes the control valve  33  to be biased out of the control slot  522 . The range of movement of the intake rocker arm  30  is not limited. Hydraulic fluid is permitted to flow to lash adjuster  432 , which extends to contact crosshead  300 . All movement of the intake rocker arm  30  when contacting intake cam lobe  13  is transferred to the crosshead  300  through the lash adjuster  32 . As a result, there is no reduction in intake valve lift and no delay in intake valve timing, as shown in FIG. 1 by line D. 
     The operation of the braking rocker arm  20  during the second operating condition during positive power is the same as during the first operating condition. The braking rocker arm  20  is disabled. 
     It is contemplated by the inventor of the present invention that the valve assemblies  510  and  520  may be independently operated and adjusted to independently vary the timing and lift of the exhaust valves and the intake valves. 
     OPERATION DURING ENGINE BRAKING 
     The operation of the exhaust rocker arm  40  will now be described during an engine braking operation. During engine braking, the valve assembly  510  is closed. This permits the hydraulic fluid within the passageway  44  to drain from the rocker arm  40 , which causes the lash adjuster  42  to retract such that it is not in contact with crosshead  400 . Hydraulic fluid does not flow from the passage  51  to the exhaust rocker arm  40 . The control valve  43  returns to a position within the control slot  512 , as shown in FIGS. 3 and 6. The range of movement of the rocker arm  40  is then limited to the size of the control slot  512 . The lash adjuster  42  again reduces exhaust valve lift and delays exhaust valve timing, as shown in FIG. 1 by line C. Furthermore, the lift associated with the EGR bump  11  is absorbed so no EGR event is produced. The operation of the intake rocker arm  30  during the engine braking will now be described. The valve assembly  520  is closed. This permits the hydraulic fluid within the passageway  34  to drain from the intake rocker arm  30 , which causes the lash adjuster  32  to retract such that it is not in contact with crosshead  300 . Hydraulic fluid does not flow from the passage  52  to the intake rocker arm  30 . The control valve  33  returns to a position within the control slot  522 , as shown in FIG.  8 . The range of movement of the rocker arm  30  is again limited to the size of the control slot  522 . The lash adjuster  32  does not extend which reduces intake valve lift and delays intake valve timing, as shown in FIG. 1 by line E. 
     The operation of the braking rocker arm  20  during an engine braking operation will now be described. During engine braking, the valve assembly  530  is operated. Hydraulic fluid is permitted to flow from passage  53  through passageway  531  within the rocker shaft  50 . The control valve  23  is biased against the flow of hydraulic fluid such that hydraulic fluid flows through passageway  24  to the actuator piston  22 . The actuator piston  22  then extends to a fully extended position such that it contacts crosshead  400 . When the passageway  24  is filled with hydraulic fluid and the pressure is equalized within valve  23 , a hydraulic lock is formed thus holding the actuator piston  22  in an extended position. The operation of the exhaust valve is now partially controlled by the braking rocker arm  20  in response to actuation by the brake cam lobe  12 . The operation of the exhaust valves will occur in response to the profile of the brake cam lobe  12 , as shown in FIG. 1 by line A. 
     It will be apparent to those skilled in the arts that various modifications and variations can be made in the construction and configuration of the present invention, without departing from the scope or spirit of the invention. For example, the braking rocker arm  20  may be eliminated. Engine braking can occur using conventional methods. Several variations have been discussed in the preceding text. Furthermore, it is contemplated that the present invention may be used with a common rail camless type engine whereby the above described rocker arms may be electronically operated. Others will be apparent to persons of ordinary skills in the art. It is intended that the present invention cover the modifications and variations of the invention, provided they come within the scope of the appended claims and their equivalence.