Patent Publication Number: US-2022235677-A1

Title: Valvetrain power tranfer module with shortened leaf-spring contact

Description:
FIELD 
     The present teachings relate to valvetrains, particularly valvetrains providing variable valve lift (VVL) or cylinder deactivation (CDA). 
     BACKGROUND 
     Hydraulically actuated latches are used on some rocker arm assemblies to implement variable valve lift (VVL) or cylinder deactivation (CDA). For example, some switching roller finger followers (SRFF) use hydraulically actuated latches. In these systems, pressurized oil from an oil pump may be used for latch actuation. The flow of pressurized oil may be regulated by an oil control valve (OCV) under the supervision of an engine control unit (ECU). A separate feed from the same source provides oil for hydraulic lash adjustment. In these systems, each rocker arm assembly has two hydraulic feeds, which entails a degree of complexity and equipment cost. 
     The oil demands of these hydraulic feeds may approach the limits of existing supply systems. The complexity and demands for oil in some valvetrain systems can be reduced by replacing hydraulically latched rocker arm assemblies with electrically latched rocker arm assemblies. Electrically latched rocker arm assemblies require power. There is an ongoing need for reliable structures for power transfer to the rocker arm assembly. 
     SUMMARY 
     The present teachings relate to powering an electrical device that is mounted to a mobile portion of a rocker arm assembly such as a rocker arm. The electrical device may be an electromagnet of an electromagnetic latch assembly. If the electrical device is powered with conventional wiring, it is a possible for a wire to be caught, clipped, or fatigued and consequently short out. The present teachings provide a valvetrain suitable for an internal combustion engine that includes a combustion chamber, a moveable valve having a seat formed within the combustion chamber, and a camshaft. The valvetrain includes a camshaft and a rocker arm assembly. The rocker arm assembly includes a rocker arm, a cam follower configured to engage a cam mounted on the camshaft as the camshaft rotates, and an electrical device mounted to the rocker arm. The rocker arm assembly may rest on a pivot that is supported by a cylinder head of the engine. 
     An electrical circuit that powers the electrical device includes a connection formed by abutment between the surfaces of two distinct parts. One of those parts is a contact pin that is mounted to a rocker arm of the rocker arm assembly. The other part is a contact pad held by the framework of a power transfer module. The power transfer module may include a wiring harness. The contact pad may be a leaf spring. Preferably, the contact pin is one of a pair on either side of the rocker arm. Having two contact pins abutted by leaf springs on opposite sides of the rocker arm tends to balance the forces placed on the rocker arm by the contact pins and leaf springs. 
     According to some aspects of the present teachings, the contact pads have protrusions toward the rocker arm assembly in an area above the contact pins. The protrusions are operative together with the contact pins to improve retention of the rocker arm assembly on the pivot. The protrusions may be bulges on the contact pad surfaces. The contact pads may be sheet metal. In some of these teaching, the protrusions are formed by rolls in the contact pads that form inward-facing lips. In some of these teachings, the contact pads are leaf springs. In some of these teachings, the contact pads have resiliency that biases the contact pads against the contact pins. The contact pads may be connected to metal leads and the framework that supports the contact pads may contain the metal leads. In some of these teachings, the framework abuts a pivot for the rocker arm assembly. In some of these teachings, the framework fits around the pivot. In some of these teachings, the framework fits around a plurality of pivots associates with a plurality of rocker arm assemblies. 
     Some aspects of the present teachings relate to a valvetrain for an internal combustion engine of a type that has a combustion chamber and a moveable valve having a seat formed in the combustion chamber. The valvetrain includes a camshaft, a pivot, a rocker arm assembly mounted on the pivot, a latch assembly, and a power transfer module. The rocker arm assembly includes a rocker arm, a cam follower configured to engage a cam mounted on the camshaft as the camshaft rotates, and two contacts pin protruding to opposite sides of the rocker arm assembly. The electromagnetic latch assembly is mounted on the rocker arm assembly and includes a latch pin and an electromagnet that is powered through at least one of the contact pins. The electromagnet is operable to move the latch pin between a first latch pin position and a second latch pin position. The power transfer module includes a framework that supports two contact pad each contacting a respective one of the contact pins. The framework has a base that abuts the pivot. The contact pads extend upward from the base and terminate at a height that is below a height of the rocker arm assembly above the pivot. In some of these teachings, the contact pads extend upwards 20 mm or less. The shortened contact pads that extend upward from the base provide a better package design than longer contact pads or contact pads that are held at the top as well as at the bottom. The design allows the rocker arms to be installed by lowering them onto the pivots after the framework has been placed on the cylinder head. The framework may fit around the pivot and be held in position by the pivot. 
     In some of these teachings the electromagnetic latch assembly provides the latch pin with positional stability independently from the electromagnet when the latch pin is in the first position and when the latch pin is in the second position. In some of these teachings, that stability is provided by one or more permanent magnets. In some of these teachings, the electromagnetic latch assembly is operable with a DC current in a first direction to actuate the latch pin from the first position to the second positions and with a DC current in a second direction, which is a reverse of the first, to actuate the latch pin from the second position to the first position. Having the electromagnetic latch assembly make the latch pin stable without power in both the first and the second positions allows the electrical connection to be broken without the latch pin position changing. Moreover, the bi-stable latch allows operation of the electromagnet to be restricted to times at which the cam is on base circle and the contact pins are stationary relative to the contact pads. It has been found that restricting current flow to times at which the contacting surfaces are stationary relative to one another reduces wear on the contacting surfaces. 
     In some of these teachings, the contact pads angle outward from the rocker arm assembly as they extend upward from the base. Having the contact pads angle outward minimizing the possibility of the rocker arm assembly rocking to one or the other side to strike one of the contact pads. Consistent with this alternative, inward bulges may still be formed in the contact pads above the contact pins. In a method according to the present teachings, the rocker arm assembly is installed on the pivot by deforming the contact pads outward to get the contact pins past the inward bulges. 
     The rocker arm assembly has a front end and a back end. The front end is the end proximate to which the rocker arm assembly abuts a valve stem. The back end is proximate the one to which the rocker arm assembly rests on the pivot. The pivot may have a dome-shaped upper surface and the rocker arm may have a gothic profile formed in its bottom surface to interface with the dome of the pivot. In some of these teachings, the contact pads extend toward the back end as they extend upward from the base. In some of these teachings, the inward protrusions above the contact pins continue into the backward extended area of the contact pad. This design facilitates retention of the rocker arm assembly on the pivot during a critical shift wherein the rocker arm may jump on the pivot and be displaced toward the back end. A contact pad that provides the surface in this backward area using a backward extending contact pad is more easily packaged as compared to the alternative of providing this backward area using a contact pad that is wider through the base. 
     The primary purpose of this summary has been to present certain of the inventors&#39; concepts in a simplified form to facilitate understanding of the more detailed description that follows. This summary is not a comprehensive description of every one of the inventors&#39; concepts or every combination of the inventors&#39; concepts that can be considered “invention”. Other concepts of the inventors will be conveyed to one of ordinary skill in the art by the following detailed description together with the drawings. The specifics disclosed herein may be generalized, narrowed, and combined in various ways with the ultimate statement of what the inventors claim as their invention being reserved for the claims that follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  provides a perspective view of a power transfer module according to some aspects of the present teachings. 
         FIG. 1B  provides another perspective view showing a portion of the power transfer module of  FIG. 1A . 
         FIG. 1C  provides a side view showing a portion of the power transfer module of  FIG. 1A . 
         FIG. 2  provides a cutaway overhead view of an engine according to some aspects of the present teachings. 
         FIG. 3  provides a perspective view of a portion of a valvetrain according to some aspects of the present teachings. 
         FIG. 4  provide a cross-sectional rear view of a portion of a valvetrain according to some aspects of the present teachings. 
         FIG. 5  provides a side view of a portion of a valvetrain according to some aspects of the present teachings. 
         FIG. 6  is a cross-sectional view of an electromagnetic latch assembly according to some aspects of the present teachings with its plunger in an extended position. 
         FIG. 7  is the view of  FIG. 6  with the plunger in a retracted position. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1A-1C  provides several views of a power transfer module  100 . Power transfer module  100  include a framework  101 , wiring  103  in framework  101 , and four pairs of contact pads  105  each extending upward from a base  107  of framework  101 . As shown in  FIG. 1A , the framework  101  including the four bases  107 . Wiring  103  is contained in framework  101  making framework  101  a lead frame. Individual wires of wiring  103  couple to contact pads  105 . The wires may terminate in a single connection plug (not shown). 
       FIG. 1B  provides a bottom perspective view of a portion of framework  101  that includes one of the bases  107  and two associated contact pads  105 . Circular openings  109  are formed in bases  107  allowing them to fit around pivots. Contact pads  105  are formed from sheet metal and are supported at one end by folds embedded in base  107 . Upper ends  137  of contact pads  105  are unsupported and free floating. Contact pads  105  are short, rising 20 mm or less from base  107 , in this example a distance in the range from 12-15 mm. Near their upper ends  137 , contact pads  105  have inward facing rolls that form inward bends  111 . 
       FIG. 1C  provides a side view of a portion of framework  101  that includes one of the bases  107  and two associated contact pads  105 . As best seen from this view, contact pads  105  generally have an outward taper. This taper is interrupted near the tops of contact pads  105  by inward bends  111 . Inward bends  111  facilitate retention of a rocker arm assembly flanked by contact pads  105  on a pivot. 
       FIG. 2  provides a cutaway overhead view of an engine  200  including a cylinder head  201  on which power transfer module  100  has been installed. Installed in this manner, contact pads  105  are located to either side of rocker arm assemblies  203 . 
       FIG. 3  provides a perspective view of a portion of a valvetrain  300  including two power transfer modules  100  and four rocker arm assemblies  203 . One of the power transfer modules  100  may be for a set of exhaust valves and the other power transfer modules  100  may be for a set of intake valves. Each rocker arm assembly  203  has a front end  309  proximate where the rocker arm assembly  203  contacts a valve stem  305  of a poppet valve  307  and a back end  311  proximate where the rocker arm assembly  203  rests on a pivot  303 . Pivots  303  may be hydraulic lash adjusters that rise from bores in cylinder head  201 . Each rocker arm assembly  203  includes a cam follower  301  for engaging a cam on a camshaft of valvetrain  300  (cams and camshafts shown in  FIG. 5 ). 
       FIG. 4  provide a cross-sectional rear view of a portion of valvetrain  300  including a power transfer module  100 , two pivots  303 , and two rocker arm assemblies  203 . A shown by this view, each rocker arm assembly  203  includes a rocker arm  401  having a latch pin  405  and two contact pins  403 . Contact pins  403  may be piloted in holes on either side of rocker arm  401 . Contact pins  403  may power an electromagnet (not shown) that is operative to actuate latch pin  405  between first and second positions. Placing latch pin  405  in the first position provides a configuration in which rocker arm assembly  203  is operative to actuate poppet valve  307  in response to rotation of the camshaft to produce a first valve lift profile. Placing latch pin  405  in the second position provides a configuration in which rocker arm assembly  203  is operative to actuate poppet valve  307  in response to rotation of the camshaft to produce a second valve lift profile, which is distinct from the first valve lift profile, or poppet valve  307  is deactivated. Latch pin  405  and the electromagnet are part of an electromagnetic latch assembly that effectuates this mode switching. 
     Rocker arm assemblies  203  may be installed on pivots  303  by pushing them downward until gothics  409  of rocker arms  401  contact domes  407  of pivots  303 . This installation process may include deforming contact pads  105  outward to allow contact pins  403  to move past the inward facing rolls that form inward bends  111 . After installation, contact pads  105  are resiliently biased against contact pins  403 . If rocker arm assembly  203  begins to rise off pivot  303 , contact pins  403  may encounter inward bends  111 , which may then function to retain rocker arm assembly  203  on pivot  303 . 
       FIG. 5  provides a side view of a portion of valvetrain  300  including camshafts  501  and cams  503 . Cams  503  engage cam followers  301  as camshafts  501  rotate. Bases  107  of framework  101  rest on cylinder head  201  and may be attached to cylinder head  201  by bolts  505 . Bases  107  abut and fit around pivots  303 . Having bases  107  abut and/or go around pivots  303  helps located contact pads  105  relative to contact pins  403 . In the present disclosure “fit around” means that after bases  107  are slid down onto pivots  303 , bases  107  surround pivots  303  to a sufficient extent to restrict motion of bases  107  in any lateral direction. 
       FIG. 5  shows rocker arms  401  fit with contact frames  507 . Contact frames  507  have conductors  509 , which are leads that may couple contact pins  403  with poles of an electromagnet housed in rocker arm  401 .  FIG. 5  also show that contact pads  105  have a rearward taper. This rearward taper causes contact pads  105  to extend toward back end  311  as they extend upward from base  107  of power transfer module  100 . The rearward taper allows inward bends  111  to extend into a rearward area  511 . During a critical shift, a rocker arm assembly  203  may shift rearward and upward to the point that contact pins  403  encounter inward bends  111  in rearward area  511 , at which point inward bends  111  may restrain the rocker arm assembly  203  and allow it to return to its normal position on pivot  303 . A critical shift is an event in which latch pin  405  slips out of engagement while rocker arm  401  is on lift, which results in rocker arm  401  moving with abnormal speed. 
       FIG. 6  shows an electromagnetic latch assembly  122  having a plunger  131  in an extended position.  FIG. 7  shows the electromagnetic latch assembly  122  with the plunger  131  in a retracted position. Permanent magnets  120  operate on the plunger  131  through low coercivity ferromagnetic ferule  123 . As illustrated by  FIGS. 6 and 7 , the magnetic circuits taken by flux from permanent magnets  120  varies as plunger  131  moves between the first and second positions. In the first position, the flux from permanent magnet  120 A follows magnetic circuit  128  (see  FIG. 6 ) which includes ring  121  and ferule  123  and goes around electromagnet  119  through shell  116 . In the second position, the flux from permanent magnet  120 A follows magnetic circuit  127  (see  FIG. 7 ), which also includes ring  121  and ferule  123  but only a small portion of shell  116 . Magnetic circuit  127  is a very tight magnetic circuit with a low flux leakage. 
     Electromagnet  119  is operable to alter magnetic polarizations in the magnetic circuits taken by flux from permanent magnets  120 . Energized with current in a first direction, electromagnet  119  is operable to cause plunger  131  to translate from the first position to the second position. Once plunger  131  is in the second position, permanent magnets  120  will stably maintain plunger  131  in the second position after power to electromagnet  119  is cut off. Energized with current in a second direction, which is the reverse of the first, electromagnet  119  is operable to cause plunger  131  to translate from the second position back to the first position. Once plunger  131  is in the first position, permanent magnets  120  will stably maintain plunger  131  in the first position after power to electromagnet  119  is again cut off. 
     The components and features of the present disclosure have been shown and/or described in terms of certain embodiments and examples. While a particular component or feature, or a broad or narrow formulation of that component or feature, may have been described in relation to only one embodiment or one example, all components and features in either their broad or narrow formulations may be combined with other components or features to the extent such combinations would be recognized as logical by one of ordinary skill in the art.