Patent Publication Number: US-10781729-B1

Title: Switchable rocker arm

Description:
TECHNICAL FIELD 
     The present invention relates to a switchable rocker arm for a valve train of an internal combustion (IC) engine. 
     BACKGROUND 
     Rocker arms are utilized within valve trains of IC engines to facilitate translation of rotary motion of a camshaft to linear motion of an intake or exhaust valve. Switchable rocker arms can facilitate different intake or exhaust valve lifts to achieve greater engine efficiency or power. Switchable rocker arms can employ a locking part that can be selectively actuated to switch between lift modes, which can include a no lift mode, low lift mode, and a full lift mode. Minimized packaging space and consistent switching times are two desired characteristics of switchable rocker arm systems. 
     SUMMARY 
     A switchable rocker arm that rotates about a pivot is provided for a valve train of an internal combustion engine. The switchable rocker arm includes a first lever, a second lever, and a locking part. The locking part is arranged to selectively lock the first lever to the second lever. The locking part is arranged to be mechanically actuated by the pivot, or, stated otherwise, arranged to be actuated by rotation of the pivot. The locking part can include a locking pin, a shuttle pin, and a bias spring. One or both of the locking pin and the shuttle pin can have a flat that is configured to engage the first or second lever. The locking pin is arranged at least partially within a locking pin bore of the first lever, and the shuttle pin is arranged at least partially within a shuttle pin bore of the second lever, with the locking pin engaging the shuttle pin. 
     The first cam lever can have a first cam end with a cam interface and a second locking end. The cam interface can be in the form of a roller follower or a slider pad. The first cam lever can further include a cam pivot interface arranged between the first cam end and the second locking end. 
     The second valve lever can have a first pivot end and a second valve end. The second valve end can include a hydraulic lash adjuster or an adjusting screw. The second valve lever can further include a first arm with a first pivot interface, and a second arm with a second pivot interface. The cam pivot interface can be axially aligned with the first and second pivot interfaces. 
     The switchable rocker arm can have: a first locked position with the first cam lever locked to the second valve lever, defining a first lift mode; and a second unlocked position with the first lever unlocked to the second lever, defining a second lift mode. The first lift mode can be a full-valve-lift mode, and the second lift mode can be a no-valve-lift mode. 
     The switchable rocker arm can have a resilient finger arranged at a first end of the locking pin bore. The resilient finger can be configured to actuate the locking pin upon rotation of the pivot. 
     A valve train system is provided that includes a pivot, at least one first switchable rocker arm arranged to rotate about the pivot, and at least one second switchable rocker arm arranged to rotate about the pivot. The at least one first switchable rocker arm has a first locking part arranged to be mechanically actuated by the pivot, and the at least one second switchable rocker arm has a second locking part arranged to be mechanically actuated by the pivot. The pivot can be a shaft that includes: a first protrusion that actuates the first locking part; and, a second protrusion that actuates the second locking part. The first protrusion can be at a first angular position, and the second protrusion can be at a second angular position which is different than the first angular position. The shaft can have an outer shaft and an inner shaft, with the outer shaft including the first protrusion, and the inner shaft including the second protrusion. The outer shaft can rotate to mechanically actuate the at least one first switchable rocker arm, and the inner shaft can rotate to mechanically actuate the at least one second switchable rocker arm. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing Summary as well as the following Detailed Description will be best understood when read in conjunction with the appended drawings. In the drawings: 
         FIG. 1  is a perspective view of a first embodiment of a switchable rocker arm together with a pivot, an engine valve, and a camshaft. 
         FIG. 2  is an exploded perspective view of the switchable rocker arm of  FIG. 1 . 
         FIG. 3A  is a top view of the switchable rocker arm and pivot of  FIG. 1 . 
         FIG. 3B  is a cross-sectional view taken from  FIG. 3A . 
         FIG. 4  is a perspective view of the pivot of  FIG. 1 . 
         FIG. 5  is a perspective view of the pivot and switchable rocker arm of  FIG. 1  together with an actuator. 
         FIG. 6A  is a cross-sectional view taken from  FIG. 1 , showing the rocker arm with a disengaged-locked locking part arrangement in a first locked position. 
         FIG. 6B  is a cross-sectional view taken from  FIG. 1 , showing the rocker arm with the disengaged-locked locking part arrangement in a second unlocked position. 
         FIG. 6C  is a cross-sectional view taken from  FIG. 1 , showing a lost motion position of the switchable rocker arm with the disengaged-locked locking part arrangement in the second unlocked position. 
         FIG. 7A  is a cross-sectional view of a switchable rocker arm with a disengaged-unlocked locking part arrangement in the second unlocked position. 
         FIG. 7B  is a cross-sectional view of the switchable rocker arm of  FIG. 7A  with the disengaged-unlocked locking part arrangement in the first locked position. 
         FIG. 8  is a perspective view of a locking part embodiment. 
         FIG. 9  is an end view of a shuttle pin bushing and locking pin bushing of the locking part of  FIG. 8 . 
         FIG. 10A  is a cross-sectional perspective view of a switchable rocker arm arrangement in a first rotational position of a pivot. 
         FIG. 10B  is a cross-sectional perspective view of the switchable rocker arm arrangement of  FIG. 10A  in a second rotational position of the pivot. 
         FIG. 11  is a cross-sectional perspective view of a switchable rocker arm arrangement together with a pivot having an inner shaft and an outer shaft with protrusions located at different angular locations. 
         FIG. 12  is a cross-sectional perspective view of a switchable rocker arm arrangement together with a pivot having an inner shaft and an outer shaft with protrusions located at the same angular position. 
         FIG. 13  is an exploded perspective view of the pivot of  FIG. 11 . 
         FIG. 14  is a perspective view of an example embodiment of a switchable rocker arm with alternative camshaft and valve interfaces. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Certain terminology is used in the following description for convenience only and is not limiting. The words “inner,” “outer,” “inwardly,” and “outwardly” refer to directions towards and away from the parts referenced in the drawings. A reference to a list of items that are cited as “at least one of a, b, or c” (where a, b, and c represent the items being listed) means any single one of the items a, b, c or combinations thereof. The terminology includes the words specifically noted above, derivatives thereof, and words of similar import. 
       FIG. 1  shows a perspective view of a first embodiment of a switchable rocker arm  10  together with a pivot  60 , a pivot axis,  11 , a camshaft  80 , and an engine valve  90 . Rotary motion of the camshaft  80  causes the switchable rocker arm  10  to rotate about the pivot  60  and respective pivot axis  11  to actuate the engine valve  90 .  FIG. 2  shows an exploded perspective view of the switchable rocker arm  10  of  FIG. 1 .  FIG. 3A  shows a top view of the switchable rocker arm  10  of  FIG. 1 , and  FIG. 3B  shows a cross-sectional view taken from  FIG. 3A .  FIG. 4  shows a perspective view of the pivot  60  of  FIG. 1 .  FIG. 5  shows a perspective view of the switchable rocker arm  10  and pivot  60  of  FIG. 1  together with an actuator  100 .  FIGS. 6A through 6C  show cross-sectional views of the switchable rocker arm  10  with a locking part  41  in different longitudinal positions to achieve different valve lift modes. The following discussion should be read in light of  FIGS. 1 through 6C . 
     The switchable rocker arm  10  can switch between at least two discrete valve lift modes. The components of the switchable rocker arm  10  include a first cam lever  12 , a second valve lever  14 , a first lost motion spring  16 A, and a second lost motion spring  16 B. Those familiar with switchable valve train components are aware that various forms of lost motion springs are possible. 
     The second valve lever  14  includes a first pivot end  22  with a first arm  24 A and a second arm  24 B, such that the first arm  24 A is axially offset from the second arm  24 B, creating a space or passage  25  in between the two arms  24 A,  24 B. The first arm  24 A includes a first rocker shaft bore  26 A and the second arm  24 B includes a second rocker shaft bore  26 B. A first retainer slot  53 A for an end of the first lost motion spring  16 A is arranged on the first arm  24 A, and a second retainer slot  53 B for the second lost motion spring  16 B is arranged on the second arm  24 B. The first and second retainer slots  53 A,  53 B also provide clearance to one or more protruding features on the pivot  60 ; the protruding features are further described in the following paragraphs. A second valve end  28  of the second valve lever  14  has a valve interface  20  in the form of a hydraulic lash adjuster which can receive hydraulic fluid via a bore  45  which is fluidly connected to a lever fluid passage  42  that extends from the second rocker shaft bore  26 B. The lever fluid passage  42  of the second valve lever  14  is fluidly connected with a radial fluid passage  44 , which is fluidly connected to an axial fluid passage  47  that receives hydraulic fluid from a pressurized fluid source  66  such as an oil pump of the IC engine. Both the radial fluid passage  44  and the axial fluid passage  47  are arranged within the pivot  60 . Other fluid passage arrangements that serve the purpose of providing hydraulic fluid to the switchable rocker arm  10  are also possible. 
     The first cam lever  12  includes a first cam end  30  with a cam interface in the form of a roller follower  18 , and a second locking end  32  with a locking pin bore  35 . A third rocker shaft bore  26 C is present at a medial position on the first cam lever  12 . The first cam lever  12  fits within the space or passage  25  created by the two arms  24 A,  24 B of the second valve lever  14 , such that the first arm  24 A extends along a first longitudinal side  48 A of the first cam lever  12 , and the second arm  24 B extends along a second longitudinal side  48 B of the first cam lever  12 . In addition, the third rocker shaft bore  26 C is in axial alignment with the first and second rocker shaft bores  26 A,  26 B of the first and second arms  24 A,  24 B, respectively, of the second valve lever  14 . A first retainer aperture  27 A for one end of the first lost motion spring  16 A is arranged on the first longitudinal side  48 A, and a second retainer aperture  27 B for one end of the second lost motion spring  16 B is arranged on the second longitudinal side  48 B. 
     The switchable rocker arm  10  captured in  FIGS. 1 through 6C  can switch between at least two discrete valve lift modes, achieved by different longitudinal positions of the locking part  41 . The locking part  41  includes a locking pin  34 , a shuttle pin  36 , a bias spring  40 , a retention cap  54 , and a retaining ring  56 . Different forms of the locking part  41  are possible, which may include additional or less components. The different longitudinal positions of the locking part  41  are achieved by rotation of the pivot  60 ; or more specifically, by rotation of a protrusion  62  arranged on the pivot  60  that can engage a resilient finger  50  arranged within a radial inner recess  46  formed around the third rocker shaft bore  26 C of the first cam lever  12 . Therefore, the locking part  41  is mechanically actuated by the pivot  60 , as opposed to being actuated by hydraulic fluid. The resilient finger  50  can be retained via a reception groove  52  formed within a wall of the radial inner recess  46 ; however, other retention means are also possible. The resilient finger  50  has a distal end  51  that is proximate to a radial inward end of the locking pin bore  35 . Referring now to  FIG. 6A , a first locked position is shown at which the locking pin bore  35  of the first cam lever  12  is axially aligned with the shuttle pin bore  37  of the second valve lever  14 , enabling engagement of the shuttle pin  36  with both the first cam lever  12  and the second valve lever  14 . The first locked position can facilitate a full-valve-lift mode such that when the first cam lever  12  is rotationally actuated by the camshaft  80  ( FIG. 1 ), the second valve lever  14  rotates in unison with the first cam lever  12  about the pivot axis  11 . In the first locked position, the locking pin bias spring  40  or resilient element with a first compressed length C 1 , urges the locking pin  34  with a pre-load force to its shown position in  FIG. 6A . 
     Referring now to  FIG. 6B , a second unlocked position is shown in which the shuttle pin  36  is moved from the locking pin bore  35 . This occurs when the protrusion  62  acts on a first end  31  of the locking pin  34  via the resilient finger  50 , displacing the locking pin  34  radially outwardly within the locking pin bore  35 . As a second end  33  of the locking pin  34  is engaged with the shuttle pin  36 , this displacement of the locking pin  34  causes the shuttle pin  36  to move radially outwardly within the shuttle pin bore  37  until it disengages the locking pin bore  35 . In the second unlocked position, the bias spring  40  compresses to a second compressed length C 2  that is shorter than the first compressed length C 1  in the first locked position. The second unlocked position can facilitate a no-valve-lift mode in which the first cam lever  12  is rotationally displaced about the pivot axis  11  by the camshaft  80  independently from the second valve lever  14 , which remains stationary. While in the no valve lift or deactivation mode, the first and second lost motion springs  16 A,  16 B provide a force that can: 1). act upon the first cam lever  12  via first and second retainer apertures  27 A,  27 B, controlling the motion of the first cam lever  12  such that separation with the camshaft does not occur at a maximum deactivation speed, and 2). act upon the second valve lever  14  via the first and second retainer slots  53 A,  53 B to prevent a pump-up or extended length condition of the valve interface  20 , such as the shown hydraulic lash adjuster, which could hinder the switching function of the switchable rocker arm  10 . 
       FIG. 6C  shows the switchable rocker arm  10  with the locking part  41  in the second unlocked position, and the first cam lever  12  rotated to depict a lost motion position where the camshaft  80  rotates the first cam lever  12 , while the second lever  14  remains stationary and does not actuate the engine valve  90 . 
       FIGS. 6A through 6C  depict a “disengaged-locked” arrangement for the locking part  41 , defined by when the protrusion  62  of the pivot  60  is not engaged with the resilient finger  50  of the switchable rocker arm  10 , the first locked position is achieved (see  FIG. 6A ). Furthermore, the second unlocked position is achieved when the protrusion  62  of the pivot  60  engages the resilient finger  50 , causing radially outwardly displacement of the locking pin  34  and the adjacent shuttle pin  36 . 
       FIGS. 7A and 7B  depict an “engaged-locked” arrangement for a locking part  41 ′, defined by when the protrusion  62  of the pivot  60  is engaged with the resilient finger  50  of the switchable rocker arm  10 ′, the first locked position is achieved (see  FIG. 7B ). Furthermore, the second unlocked position is achieved when the protrusion  62  of the pivot  60  disengages the resilient finger  50 , causing radially inwardly displacement of a locking pin  34 ′ and an adjacent shuttle pin  36 ′ (see  FIG. 7A ). 
     Referring to  FIG. 8 , an embodiment of a locking part  41 ″ is shown that includes a locking pin  34 ″ configured with a first flat  29 , a locking pin bore sleeve  38  configured with a second flat  57 , a shuttle pin  36 ″ configured with a third flat  49 , and a shuttle pin bore sleeve  39  configured with a fourth flat  58 . The locking part  41 ″ can provide a flat locking interface between the first cam lever  12  and the second valve lever  14 . In the first locked position, the third flat  49  of the shuttle pin  36 ″ engages the second flat  57  of the locking pin bore sleeve  38  and the fourth flat  58  of the shuttle pin bore sleeve  39  (see  FIG. 12 ). For clarity purposes,  FIG. 9  shows an end view of the locking pin bore sleeve  38  and the shuttle pin bore sleeve  39 , which have identical end views. However, it could be possible that the locking pin bore sleeve  38  and the shuttle pin bore sleeve  39  do not have duplicative end views, as shown in  FIG. 9 . 
       FIG. 4  shows an isometric exploded view of the pivot  60  in the form of a rocker shaft. The protrusion  62  is shown displaced from a protrusion receiving aperture  63  that fixes the protrusion  62  to the pivot  60 . Other forms of the protrusion  62  and its attachment to the pivot  60  are also possible. The pivot  60  is configured with an outer recess  43  that fluidly connects the radial fluid passage  44  of the pivot  60  to the lever fluid passage  42  of the switchable rocker arm  10  throughout at least a portion of an angular range of rotation of one or both of the pivot  60  and the switchable rocker arm  10 . 
       FIG. 5  shows an isometric view of a rotary actuator  100 , controlled by an electronic controller  70 , together with the pivot  60  and switchable rocker arm  10 . The electronic controller  70  communicates electronically with the rotary actuator  100  to move the pivot  60  in either a first direction D 1  or a second direction D 2  to any desired rotational position within a continuous range of rotational positions. Stated otherwise, a rotary position of the pivot is continuously variable. The rotary actuator  100  is non-rotatably connected to the shaft via a coupling  98  that translates rotary motion of the actuator  100  to rotary motion of the pivot  60 . The term “non-rotatably connected” is meant to signify two elements that are directly or indirectly connected in a way that whenever one of the elements rotate, both of the elements rotate in unison, such that relative rotation between these elements is not possible. Radial and/or axial movement or offset of non-rotatably connected elements with respect to each other is possible, but not required. 
       FIGS. 10A and 10B  show a tandem switchable rocker arm and pivot arrangement  200  that includes a first switchable rocker arm  10 A, a second switchable rocker arm  10 B, and a pivot  60 A. The first switchable rocker arm  10 A includes a first resilient finger  50 A that interacts with a first protrusion  62 A arranged on the pivot  60 A to selectively lock and unlock the first switchable rocker arm  10 A. The second switchable rocker arm  10 B includes a second resilient finger  50 B that interacts with a second protrusion  62 B arranged on the pivot  60 A to selectively lock and unlock the second switchable rocker arm  10 B. As shown in  FIG. 10A , a first axis AX 1  extends from the center of the first protrusion  62 A and intersects the pivot axis  11  at a first angle AN 1 . A second axis AX 2  extends from the center of the second protrusion  62 B and intersects the pivot axis  11  at a second angle AN 2 . The second angle AN 2  is different than the first angle AN 1 . The different angular locations AN 1 , AN 2  of the first and second protrusions  62 A,  62 B can facilitate different angular engagement positions of the first and second protrusions  62 A,  62 B and respective first and second resilient fingers  50 A,  50 B.  FIG. 10A  shows the pivot  60 A in a first angular position in which the first protrusion  62 A is not engaged with the first resilient finger  50 A, while the second protrusion  62 B is engaged with the second resilient finger  50 B.  FIG. 10B  shows the pivot  60 A in a second angular position in which the pivot  60 A is rotated in the first direction D 1  from the first angular position shown in  FIG. 10A . In this second angular position, both of the first and second protrusions  62 A,  62 B are engaged with respective first and second resilient fingers  50 A,  50 B. 
     The first resilient finger  50 A has a first distal end  51 A that extends further circumferentially than a second distal end  51 B of the second resilient finger  50 B. This extended first distal end  51 A facilitates an engagement between the first protrusion  62 A and the first resilient finger  50 A over a longer circumferential distance than an engagement between the second protrusion  62 B and the second resilient finger  50 B. 
       FIG. 11  shows a perspective view of an embodiment of a pivot  60 ′ together with a switchable rocker arm  10 ″ configured with the previously described locking part  41 ″ in the second unlocked position.  FIG. 13  shows an exploded perspective view of the pivot  60 ′. With view to  FIGS. 11 and 13 , the pivot  60 ′ includes an outer shaft  64 ′ and an inner shaft  67 ′ that are each rotatable relative to the other and can each be separately actuated. The pivot  60 ′ includes a first protrusion  62 A′ that is connected to the inner shaft  67 ′ via a first protrusion aperture  63 A′; the first protrusion  62 A′ extends through a circumferential slot  65 ′ of the outer shaft  64 ′. The pivot  60 ′ also includes a second protrusion  62 B′ that is connected to the outer shaft  64 ′ via a second protrusion aperture  63 B′. Upon rotation of the inner shaft  67 ′ or the outer shaft  64 ′ relative to the other, the first protrusion  62 A′ can move back and forth within the circumferential slot  65 ′. A first axis AX 1 ′ extends from the center of the first protrusion  62 A′ and intersects the pivot axis  11  at a first angle AN 1 ′. For clarity purposes, the first angle AN 1 ′ is shown at an end of the pivot axis  11  within  FIG. 11 . A second axis AX 2 ′ extends from the center of the second protrusion  62 B′ and intersects the pivot axis  11  at a second angle AN 2 ′. The second angle AN 2 ′ is different than the first angle AN 1 ′. The different angular locations AN 1 ′, AN 2 ′ of the first and second protrusions  62 A′,  62 B′ can facilitate different angular engagement positions of the first and second protrusions  62 A′,  62 B′ and respective resilient fingers. 
     As shown in  FIGS. 3B and 13 , the pivot  60 ′ is configured with multiple fluid passages and features to fluidly connect the pressurized hydraulic fluid source  66  to the lever fluid passage  42 . The outer shaft  64 ′ is configured with first and second outer recesses  43 A′,  43 B′ that fluidly connect the lever fluid passage  42  to first and second outer radial fluid passages  44 A′,  44 B′. The first and second outer recesses  43 A′,  43 B′ also fluidly connect the outer shaft  64 ′ to the switchable rocker arm  10 ,  10 ′,  10 ″ throughout at least a portion of an angular range of rotation of one or both of the pivot  60  and the switchable rocker arm  10 ,  10 ′,  10 ″. The inner shaft  67 ′ is configured with first and second inner recesses  68 A′,  68 B′, first and second inner radial fluid passages  69 A′,  69 B′, and an inner axial fluid passage  47 ′ to complete a fluid circuit from the pressurized hydraulic fluid source  66  to the switchable rocker arm  10 ,  10 ′,  10 ″. The first and second inner recesses  68 A′,  68 B′ fluidly connect the inner shaft  67 ′ to the outer shaft  64 ′ throughout at least a portion of an angular range of relative rotation between the inner shaft  67 ′ and the outer shaft  64 ′. 
       FIG. 12  shows a perspective view of an embodiment of a pivot  60 ″ together with the switchable rocker arm  10 ″ of  FIG. 11 , but with the locking part  41 ″ in the first locked position. The pivot  60 ″ includes an outer shaft  64 ″ and an inner shaft  67 ″ that are rotatable relative to each other and can each be separately actuated. As with the pivot  60 ′ of  FIGS. 11 and 13 , the pivot  60 ″ includes a first protrusion  62 A″ and a second protrusion  62 B″ that are connected to respective inner and outer shafts  67 ″,  64 ″. A first axis AX 1 ″ of the first protrusion  62 A″ intersects the pivot axis  11  at a first angle AN 1 ″, and a second axis AX 2 ″ of the second protrusion  62 B″ intersects the pivot axis  11  at a second angle AN 2 ″; however, in this embodiment of the pivot  60 ″, the first angle AN 1 ″ is equal to the second angle AN 2 ″. 
     While  FIGS. 10A through 13  show a shaft arrangement that can accommodate two rocker arms, a larger number of rocker arms could be accommodated with an increased number of protrusions. The protrusions could be arranged in various angular locations including, but not limited to, those shown in the figures. 
     Referring to  FIG. 14 , an embodiment of a switchable rocker arm  10 ′″ is shown that utilizes an alternative valve interface  20 ′ in the form of an adjusting screw assembly, and an alternative cam interface  18 ′ in the form of a slider pad. Utilizing one or both of these alternative interfaces  20 ′,  18 ′ can reduce the complexity and cost of the switchable rocker arm  10 ′″. 
     Having thus described various embodiments of the present switchable rocker arm in detail, it is to be appreciated and will be apparent to those skilled in the art that many physical changes, only a few of which are exemplified in the detailed description above, could be made in the apparatus without altering the inventive concepts and principles embodied therein. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore to be embraced therein.