Patent Publication Number: US-11022008-B2

Title: Ball engine brake mechanism

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/US2018/047729 filed Aug. 23, 2019, which claims the benefit of U.S. Provisional Application No. 62/549,615 filed Aug. 24, 2017. The disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates generally to a rocker arm assembly for use in a valve train assembly and more particularly to a rocker arm assembly that incorporates a ball mechanism to perform an engine brake function and other variable valve actuation (VVA) functions. 
     BACKGROUND 
     Compression engine brakes can be used as auxiliary brakes, in addition to wheel brakes, on relatively large vehicles, for example trucks, powered by heavy or medium duty diesel engines. A compression engine braking system is arranged, when activated, to provide an additional opening of an engine cylinder&#39;s exhaust valve when the piston in that cylinder is near a top-dead-center position of its compression stroke so that compressed air can be released through the exhaust valve. This causes the engine to function as a power consuming air compressor which slows the vehicle. 
     In a typical valve train assembly used with a compression engine brake, the exhaust valve is actuated by a rocker arm which engages the exhaust valve by means of a valve bridge. The rocker arm rocks in response to a cam on a rotating cam shaft and presses down on the valve bridge which itself presses down on the exhaust valve to open it. A hydraulic lash adjuster may also be provided in the valve train assembly to remove any lash or gap that develops between the components in the valve train assembly. 
     The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     SUMMARY 
     An exhaust valve rocker arm assembly operable in a combustion engine mode and an engine braking mode, the exhaust valve rocker arm assembly selectively opening first and second exhaust valves and including a rocker shaft, exhaust valve rocker arm assembly and a ball engine brake mechanism. The exhaust valve rocker arm assembly has an exhaust rocker arm that receives the rocker shaft and is configured to rotate around the rocker shaft. The ball engine brake mechanism is configured on the exhaust rocker arm and selectively actuates a valve plunger causing an exhaust valve to perform engine braking. The ball engine brake mechanism includes a capsule assembly having a capsule, a biasing member and a ball. The capsule has a cylindrical body that extends between a first end having an actuation face and a second end having a spring return face. The cylindrical body defines an opening that receives the ball therein. The capsule and the ball move as a unit from an unactuated position to an actuated position. 
     According to additional features, the ball engine brake mechanism further comprises a threaded plunger that threadably mates with the exhaust rocker arm. The threaded plunger opposes the valve plunger. The valve plunger and the threaded plunger both define respective concave receiving surfaces. The ball positively locates at the respective concave receiving surfaces in the actuated position. The capsule and ball translates to the actuated position causing the valve plunger to extend toward one of the first and second exhaust valves to perform engine braking. The cylindrical body defines a blind bore having the spring return face. 
     In other features, the biasing member is at least partially nestingly received in the blind bore. The biasing member biases the capsule toward the unactuated position. A valve plunger spring biases the valve plunger to a collapsed position. A lock nut locks the threaded plunger relative to the exhaust rocker arm. The capsule assembly can be hydraulically actuated in one example. The capsule assembly can be mechanically actuated in another example. The exhaust rocker arm can be a dedicated engine brake rocker arm. 
     An exhaust valve rocker arm assembly according to another example of the present disclosure is operable in a combustion engine mode and an engine braking mode, the exhaust valve rocker arm assembly selectively opening first and second exhaust valves and including a rocker shaft, exhaust valve rocker arm assembly and a ball engine brake mechanism. The exhaust valve rocker arm assembly has an exhaust rocker arm that receives the rocker shaft and is configured to rotate around the rocker shaft. The ball engine brake mechanism is configured on the exhaust rocker arm and selectively actuates a valve plunger causing an exhaust valve to perform engine braking. The ball engine brake mechanism includes a capsule assembly having a capsule, a biasing member and a ball. The capsule has a unitary cylindrical body that extends between a first end having an actuation face and a second end having a spring return face. The cylindrical body defines an opening that receives the ball therein. The capsule and the ball move as a unit from an unactuated position to an actuated position. In the unactuated position, the valve plunger does not act on the exhaust valve. In the actuated position, the valve plunger acts on the exhaust valve to open the exhaust valve during an engine braking event. Translation of the actuation face causes equal translation of the spring return face. 
     According to additional features, the ball engine brake mechanism further comprises a threaded plunger that threadably mates with the exhaust rocker arm and that opposes the valve plunger. The valve plunger and the threaded plunger both define respective concave receiving surfaces. The ball positively locates at the respective concave receiving surfaces in the actuated position. The cylindrical body defines a blind bore having the spring return face. 
     In other features, the biasing member is at least partially nestingly received in the blind bore. The biasing member biases the capsule toward the unactuated position. The capsule assembly can be hydraulically actuated in one example. The capsule assembly can be mechanically actuated in another example. The capsule assembly can be electrically actuated in another example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a top view of a partial valve train assembly incorporating a rocker arm assembly including ball engine brake mechanism for engine brake constructed in accordance to one example of the present disclosure; 
         FIG. 2  is a side view of the exhaust valve rocker arm assembly of  FIG. 1 ; 
         FIG. 3  is a sectional view of the ball engine brake mechanism of  FIG. 1  and shown in an extended position subsequent to application of an actuation force; 
         FIG. 4  is a sectional view of the ball engine brake mechanism of  FIG. 1  and shown in a collapsed position subsequent to application of an actuation force; 
         FIG. 5  is a side view of an exhaust valve rocker arm assembly having a dedicated engine brake rocker arm according to another example of the present disclosure; 
         FIG. 6  is an exploded perspective view of a capsule assembly constructed in accordance to one example of the present disclosure; and 
         FIG. 7  is a sectional view of the capsule assembly of  FIG. 6  and shown disposed between a threaded plunger and valve plunger in an actuated position according to one example of the present disclosure; and 
         FIG. 8  is a sectional view of the capsule assembly of  FIG. 7  and shown offset from the threaded plunger and valve plunger in an unactuated position according to one example of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Heavy duty (HD) diesel engines with single overhead cam (SOHC) valvetrain requires high braking power, in particular at low engine speed. The present disclosure provides an added motion type De-Compression engine brake. To provide high braking power without applying high load on the rest of the valvetrain (particularly the camshaft), the present disclosure provides a rocker arm assembly having a rotating stepped brake capsule with castellation mechanism for engine brake that acts on one exhaust valve. In this regard, half of the input load is experienced compared to other configurations that have two exhaust valves opening. 
     With initial reference to  FIGS. 1 and 2 , a partial valve train assembly constructed in accordance to one example of the present disclosure is shown and generally identified at reference  10 . The partial valve train assembly  10  utilizes engine braking can be configured for use in a six-cylinder engine. It will be appreciated however that the present teachings are not so limited. In this regard, the present disclosure may be used in any valve train assembly that utilizes engine braking. The partial valve train assembly  10  is supported in a valve train carrier  12  and can include two rocker arms per cylinder. It will be appreciated that the configuration shown in  FIG. 1  is merely exemplary and the valve train assembly  10  can take other arrangements within the scope of the present disclosure. 
     Each cylinder includes an intake valve rocker arm assembly  20 , and an exhaust valve rocker arm assembly  22 . The exhaust valve rocker arm assembly  22  incorporates integrated engine brake functionality. The exhaust valve rocker arm assembly  22  controls opening of the exhaust valves. The intake valve rocker arm assembly  20  is configured to control motion of the intake valves. The exhaust valve rocker arm assembly  22  is configured to control exhaust valve motion in a drive mode and in brake mode. The exhaust valve rocker arm assembly  22  is configured to act on one of the two exhaust arms in an engine brake mode as will be described herein. A rocker shaft  34  is received by the valve train carrier  12  and supports rotation of the exhaust valve rocker arm assembly  22 . 
     With further reference now to  FIG. 2 , the exhaust valve rocker arm assembly  22  will be further described. The exhaust valve rocker arm assembly  22  can generally include an exhaust rocker arm  40 , a valve bridge  42 , a spigot assembly  44  and a ball engine brake mechanism  48 . The valve bridge  42  engages a first and second exhaust valve  50  and  52  ( FIG. 1 ) associated with a cylinder of an engine (not shown). In the example shown, the first exhaust valve  50  is a non-braking exhaust valve that is biased by a valve spring  54 . The second exhaust valve  52  is a braking exhaust valve that is biased by a valve spring  56 . The exhaust rocker arm  40  rotates around the rocker shaft  34  based on a lift profile of a cam shaft (explained below). 
     The ball engine brake mechanism  48  will be further described. The ball engine brake mechanism  48  is capable of handling lost motion. High load can be actuated either mechanically or hydraulically and is biased to be normally collapsed ( FIG. 4 ). The ball engine brake mechanism  48  can be used for added motion engine brake, integrated lost motion engine brake and other WA functions. In this regard, the ball engine brake mechanism  48  is configured to perform engine braking and other WA function by selectively changing a valve lift profile based on a control signal and actuation. 
     The ball engine brake mechanism  48  includes a press-out plunger  110  and an actuation plunger  112 . A press-out biasing member  114  biases the press-out plunger  110  in a direction toward the actuation plunger  112 . The press-out plunger  110  and the actuation plunger  112  are horizontally opposed. A ball  120  is positioned between the press-out plunger  110  and the actuation plunger  112 . A threaded plunger  130  threadably mates with the rocker arm  40 . A lock nut  134  locks the threaded plunger  130  relative to the rocker arm  40 . A valve plunger  140  vertically opposes the threaded plunger  130 . A valve plunger retainer  144  supports a valve plunger spring  150 . The valve plunger spring  150  biases the valve plunger  140  to a collapsed position ( FIG. 4 ). 
     The ball engine brake mechanism  48  moves between a collapsed position ( FIG. 4 ) and an extended position ( FIG. 3 ). The ball engine brake mechanism  48  is normally in the collapsed position. When a controller  160  determines that an engine braking event should occur, the controller  160  sends a signal to an actuator  162 . The actuator  162  urges the actuation plunger  112  in a direction leftward as viewed in FIG.  3 . The actuator  162  can be a hydraulic actuator, a mechanical actuator, an electric actuator or other actuator suitable to move the actuation plunger leftward causing the ball  120  to located in the position shown in  FIG. 3  between the threaded plunger  130  and the valve plunger  140 . Once an actuation force (hydraulic, mechanical, electrical, etc.) urges the actuation plunger  112  leftward from a position shown in  FIG. 4  to a position shown in  FIG. 3 , the ball  120  locates between the threaded plunger  130  and the valve plunger  140  causing the valve plunger  140  to move to an extended position ( FIG. 3 ) and act on pin  166  thereby actuating the engine valve  52  and allowing engine braking and/or other VVT functions. 
     When the actuation force ceases, the press-out spring  114  urges the ball  120  back to the position in  FIG. 4 . Concurrently, the valve plunger  140  moves back to the collapsed position by the valve plunger spring  150 . The process repeats upon entering engine braking mode or other VVA function where the actuation plunger  112  is urged toward the ball  120 . 
     With reference to  FIG. 5 , an exhaust valve rocker arm assembly  222  constructed in accordance to another example of the present disclosure is shown. The exhaust valve rocker arm assembly  222  includes a normal exhaust rocker arm  238  and a dedicated engine brake rocker arm  240 . The exhaust valve rocker arm assembly  222  controls opening of exhaust valves  250  and  252 . The intake valve rocker arm assembly can be configured similar to the intake valve rocker arm assembly  20  shown in  FIG. 1 . The exhaust valve rocker arm assembly  222  is configured to control exhaust valve motion in a drive mode and in brake mode. The dedicated engine brake rocker arm  240  of the exhaust valve rocker arm assembly  222  is configured to act on the exhaust valve  252  in an engine brake mode as will be described herein. A rocker shaft  234  is received by the valve train carrier and supports rotation of the dedicated engine brake rocker arm  240 . The exhaust valve rocker arm assembly  222  includes a valve bridge  242 , a spigot assembly  244  and a ball engine brake mechanism  248 . 
     The ball engine brake mechanism  248  can operate similar to the ball engine brake mechanism  48  described above. The ball engine brake mechanism  248  includes a press-out plunger  310  and an actuation plunger  312 . A press-out biasing member  314  biases the press-out plunger  310  in a direction toward the actuation plunger  312 . The press-out plunger  310  and the actuation plunger  312  are horizontally opposed. A ball  320  is positioned between the press-out plunger  310  and the actuation plunger  312 . A threaded plunger  330  threadably mates with the rocker arm  240 . A lock nut  334  locks the threaded plunger  330  relative to the rocker arm  240 . A valve plunger  340  vertically opposes the threaded plunger  330 . A valve plunger retainer  344  supports a valve plunger spring  350 . The valve plunger spring  350  biases the valve plunger  340  to a collapsed position (see position of valve plunger  140 ,  FIG. 4 ). 
     The ball engine brake mechanism  248  moves between a collapsed position and an extended position (see ball engine brake mechanism  48 ,  FIGS. 3 and 4 ). The ball engine brake mechanism  248  is normally in the collapsed position. When a controller  460  determines that an engine braking event should occur, the controller  460  sends a signal to an actuator  462 . The actuator  462  urges the actuation plunger  312  in a direction leftward as viewed in  FIG. 5 . The actuator  462  can be a hydraulic actuator, a mechanical actuator, an electric actuator or other actuator suitable to move the actuation plunger leftward causing the ball  320  to locate in the position shown in  FIG. 5  between the threaded plunger  330  and the valve plunger  340 . Once an actuation force (hydraulic, mechanical, electrical, etc.) urges the actuation plunger  312  leftward to the position shown in  FIG. 5 , the ball  320  locates between the threaded plunger  330  and the valve plunger  340  causing the valve plunger  340  to move to an extended position ( FIG. 5 ) and act on pin  366  thereby actuating the engine valve  252  and allowing engine braking and/or other WT functions. 
     When the actuation force ceases, the press-out spring  314  urges the ball  320  back to a position out of alignment with the threaded plunger  330  and the valve plunger  340 . Concurrently, the valve plunger  140  moves back to the collapsed position by the valve plunger spring  150 . The process repeats upon entering engine braking mode or other WA function where the actuation plunger  112  is urged toward the ball  120 . 
     With reference now to  FIGS. 6-8 , a capsule assembly  410  constructed in accordance to another example of the present disclosure will be described. It will be appreciated that that the capsule assembly  410  can be used in any of the rocker arm configurations described herein. The capsule assembly  410  generally comprises a capsule  412 , a biasing member  414  and a ball  420 . A threaded plunger  430  threadably mates with the rocker arm as discussed above. The threaded plunger  430  can define a concave receiving surface  431  on a distal end thereof. A valve plunger  440  vertically opposes the threaded plunger  430 . The valve plunger  440  can define a concave receiving surface  441  on a distal end thereof. A ball engine brake mechanism  448  comprises the capsule assembly  410 , the threaded plunger  430  and the valve plunger  440 . 
     As will become appreciated from the following discussion, the capsule assembly  410  can translate as a single unit between an unactuated position shown in  FIG. 7  and an actuated position (such as for engine braking) shown in  FIG. 8 . The capsule  412  can include a cylindrical body  422  extending between a first end  424  and a second end  444 . A central body portion  446  defines inset portions  447 . An opening  450  is defined through the cylindrical body  422  at the central body portion  446 . The opening  450  defines an inner diameter suitable to accept the ball  420  therein. 
     The first end  424  defines an actuation face  454 . The cylindrical body  422  defines a blind bore  455  having a spring return face  456  at the second end  444 . The biasing member  414  is at least partially nestingly received in the blind bore  455 . An actuation force  458  generated by actuator  462  (hydraulic, mechanical, electrical) in response to a signal from the controller  460  is applied onto the actuation face  454 . The biasing member  414  acts on the spring return face  456 . 
     The actuation force  458  is directly linked to the spring return face  456 . In other words, the capsule  412  is unitary or integrally formed whereby the force  458  acting onto the actuation face  454  is directly connected and acted onto the spring return face  456 . In this regard, separation of the actuation face  454  and the spring return face  456  is precluded. Translation of the actuation face  454  causes equal translation of the spring return face  456 . Greater control of the position of the ball  420  is realized by the capsule assembly  410  and the ball engine brake mechanism  448  as a whole. The ball  420  positively locates between the concave receiving surface  431  of the threaded plunger  430  and the concave receiving surface  441  of the valve plunger  440 . By way of example, the capsule  412  can be about 11.5 mm in diameter. The opening  450  can be 9.5 mm in diameter. The ball  420  can be 9 mm in diameter. Other dimensions are contemplated. 
     It will be further appreciated that any of the ball brake mechanisms described herein may be used in a dedicated added motion engine brake arm and/or a bolt on bleeder brake design. In this regard, the ball brake mechanism is mounted in a dedicated brake arm that acts on the brake valve through a pass through pin or similar arrangement. Similarly, the ball brake mechanism can be used in a bolt on carrier fixed to the cylinder head where the mechanism could act on the brake valve through a pass through pin or similar arrangement. 
     The foregoing description of the examples has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular example are generally not limited to that particular example, but, where applicable, are interchangeable and can be used in a selected example, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.