Sliding spring contacts providing electrical power to rocker arms

The present teachings relate to valvetrains, particularly valvetrains providing variable valve lift (VVL) or cylinder deactivation (CDA).

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. This means that each rocker arm 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.

Using electromechanical latch assemblies instead of hydraulically-actuated latches can reduce complexity and demands for oil in some valvetrain systems. Electromechanical latch assemblies create the need to provide electrical power to the valvetrain. Valvetrain electrical power is also desirable for devices that could provide on board diagnostic information for cylinder deactivating and switching rocker arm assemblies.

The present teachings relate to a valvetrain suitable for an internal combustion engine of a type that includes a combustion chamber and a moveable valve having a seat formed within the combustion chamber. The valvetrain includes a camshaft, a lash adjuster, and a rocker arm assembly. The rocker arm assembly includes an electrical device, a rocker arm, and a cam follower configured to engage a cam on the camshaft as the camshaft rotates. A contact held to the rocker arm abuts a spring attached to a component distinct from the rocker arm assembly to form an interface. The electrical device is powered through the interface. The spring slides over the contact as the rocker arm assembly pivots to actuate a moveable valve. The interface may be formed near a pivot axis whereby the motion undergone by the interface is much less than the motion undergone by points on the rocker arm assembly more distal from the axis. Keeping the interface proximate the pivot axis and leaving the spring free to slide over the contact reducing the extent to which the spring undergoes movement and wear during valvetrain operation.

The lash adjuster provides a fulcrum for the rocker arm assembly. In some of these teachings, the spring extends and contracts along a direction in which the lash adjuster extends and contracts to adjust lash. In some of these teachings, one end of the spring is attached to a framework that abuts the lash adjuster. In some of these teachings the spring has a first end that abuts the contact surface, a second end that is distal from the contact surface and is held in a fixed position. In some of these teachings, that fixed position is proximate a cylinder head. In some of these teachings, the contact is held to a side of the rocker arm and presents a contact surface that is close to and parallel to an axis on which the rocker arm assembly pivots to actuate the moveable valve.

In some of these teachings the spring is ribbon-shaped. In some of these teachings, a face of the spring abuts a face of the contact. This configuration may provide a high contact area. In some of these teachings the spring curves to form convex and concave sides and a concave side of the spring abuts the contact. The contact may be a pin although in some of these teachings, the contact is provided by a ribbon of metal.

In some of these teachings the spring is an accordion spring. The spring may have two straight arms connected by a hoop. In some of these teachings, the hoop is larger than required to connect the ends of the straight arms with a steady curve. In some of these teachings, the two straight arms are connected to the hoop by bends having a curvature opposite a curvature of the hoop.

In some of these teachings, the spring is partially enclosed by a spring box in a manner that resists twisting of the spring. The spring may be flat. The spring box may include two parallel sides. A flat face of the spring may bend between the two parallel sides while the flat face remains perpendicular to those sides.

In some of these teachings, the spring wraps around the contact to provide an interference fit. In some of these teachings the spring forms a hoop around a contact that is in the form of a pin. These configurations increase the reliability with which an electrical connection between the spring and the contact is maintained.

In some of these teachings, the contact surface is proximate a pivot axis for the rocker arm assembly. Preferably, the contact is on the pivot axis. In some of these teachings the rocker arm forms a spring post proximate the pivot axis and the contact is installed on the spring post. In some of these teachings the contact is support by a pin piloted to the rocker arm. The rocker arm may be made of a conductive material. In some of these teachings the pin is held within an insulating sleeve in the rocker arm. In some of these teachings a lead for the electrical device is soldered to the contact.

In some of these teachings, the electrical device is an electromechanical latch assembly. The electromechanical latch assembly may include a latch pin and an electrical coil. The electrical coil may be mounted on a rocker arm of the rocker arm assembly. Alternatively, the electrical device may be a sensor that provides information useful for diagnostic or control operations.

In some of these teachings the spring bears down on the contact to bias the rocker arm assembly against the lash adjuster. In some of these teachings the lash adjuster is a hydraulic lash adjuster. In some of these teachings the spring retains the rocker arm assembly on the lash adjuster. In some of these teachings the spring is anchored to the lash adjuster. Retaining the rocker arm assembly on the lash adjuster using the spring may facilitate installation of the valvetrain.

In some of these teachings a second contact projects from the rocker arm opposite the first contact. First and second leads for the electrical device may be attached to the first and second contacts. Having springs on both sides of the rocker arm balances the forces the springs place on the rocker arm assembly.

Some aspects of the present teachings relate to a method of installing a valvetrain that includes attaching the rocker arm assembly to a pivot, such as a lash adjuster, using the spring and installing the pivot with the attached rocker arm assembly in the cylinder head of an engine. This method simplifies installation of the valvetrain. Moreover, this method allows the valvetrain manufacturer to complete most of the wiring for any electrical devices that are provided with the valvetrain.

The primary purpose of this summary has been to present certain of the inventors' 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' concepts or every combination of the inventors' 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.

FIG. 1 is a rear view of a rocker arm assembly in a valvetrain of an engine according to some aspects of the present teachings.

FIG. 2 is a side view of the rocker arm assembly of FIG. 1 in the valvetrain of the engine of FIG. 1 .

FIG. 3 is a perspective cutaway view of the rocker arm assembly of FIG. 1 fitted with a lead frame.

FIG. 4 is a flow chart of a method according to some aspects of the present teachings.

FIG. 5 is a rear view of a rocker arm assembly in a valvetrain of an engine according to some aspects of the present teachings.

FIG. 6 is a side view of the rocker arm assembly of FIG. 5 in the valvetrain of the engine of FIG. 5 .

FIG. 7 is a perspective view of rocker arm assembly and a pivot in a valvetrain according to some other aspects of the present teachings.

FIG. 8 is another perspective view of the rocker arm assembly and the pivot of FIG. 7 .

FIG. 9 is a cutaway side view of the rocker arm assembly and the pivot of FIG. 7 with the rocker arm assembly in a valve-closed position and the lash adjuster raised.

FIG. 10 is the same view as FIG. 9 , but with the rocker arm assembly pivoted to a valve-open position.

FIG. 11 is the same view as FIG. 9 , but with the lash adjuster lowered.

FIGS. 1 and 2 illustrates a portion of an engine 100 A including portions of a cylinder head 102 and a valvetrain 104 A. Valvetrain 104 A includes hydraulic lash adjuster 140 and rocker arm assembly 106 A. Hydraulic lash adjuster 140 is a pivot and is installed in cylinder head 102 . Rocker arm assembly 106 A is a cylinder deactivating rocker arm that includes an inner arm 110 A, an outer arm 111 A, and a cam follower 112 mounted to inner arm 110 A. Spring posts 157 are formed in outer arm 111 A. Torsion springs 159 are mounted on hubs 149 that fit over spring posts 157 . Contacts 121 A having the form of pins are mounted to outer arm 111 A and are piloted in spring posts 157 . Hydraulic lash adjuster 140 provides a fulcrum on which rocker arm assembly 106 A pivots with a pivot axis that is close to and may intersect contacts 121 A.

FIG. 3 illustrates rocker arm assembly 106 A in greater detail. Rocker arm assembly 106 A includes an electromagnetic latch assembly 107 mounted to outer arm 111 A. Electromagnetic latch assembly 107 includes a latch pin 108 and an electrical coil 109 . Electrical coil 109 is operable to actuate latch pin 108 between engaging and non-engaging positions. Rotating a camshaft (not shown) actuates rocker arm assembly 106 A through cam follower 112 . With latch pin 108 in the engaging position, rocker arm assembly 106 A is operative to open and close a moveable valve (not shown), such as a poppet valve having a seat formed in cylinder head 102 . With latch pin 108 in the non-engaging position, actuating rocker arm assembly 106 A by rotating the camshaft causes inner arm 110 A to pivot and torsion springs 159 to wind, but leaves outer arm 111 A stationary and the moveable valve closed.

In electromagnetic latch assembly 107 , magnets 120 make latch pin 108 stable independently from electrical coil 109 in both engaging and non-engaging positions. Energized with a DC current in a first direction, electrical coil 109 is operable to actuate latch pin 109 from the engaging to the non-engaging position. Energized with a DC current in the opposite direction, electrical coil 109 is operable to actuate latch pin 108 from the non-engaging position to the engaging position.

Coil 109 is powered through contacts 121 A. A lead frame, which is not shown in FIGS. 1 and 2 but may be similar to the lead frame 409 shown on rocker arm 106 A in FIG. 3 may be used for that purpose. Lead frame 409 includes conductors 413 that may be soldered to contacts 121 A. Conductors 419 connect with coil 109 at coil tie-offs 135 at the back of outer arm 111 A. Lead frame 409 may be supported in an opening formed in the back of outer arm 111 A. Alternatively, or in addition, lead frame 409 may be supported at the sides of outer arm 111 A by contacts 121 A. Lead frame 409 may be over-molded around conductors 419 .

Referring to FIGS. 1 and 2 , spring 137 A is anchored at one end to a support frame 139 A. Support frame 139 A abuts hydraulic lash adjuster 140 . Having support frame 139 A abut hydraulic lash adjuster 140 facilitates locating spring 137 A correctly relative to contacts 121 A. Support frame 139 A surrounds and attaches to hydraulic lash adjuster 140 . Spring 137 A is anchored to hydraulic lash adjuster 140 through support frame 139 A. Support frame 139 A may rest on cylinder head 102 and may be attached to cylinder head 102 . For example, support frame 139 A may be bolted to cylinder head 102 . Support frame 139 A keeps one end of spring 137 A fixed in a position proximate cylinder head 102 . In addition to providing an anchor for spring 137 A, support frame 139 A electrically isolates spring 137 A from cylinder head 102 .

Spring 137 A is a ribbon of conductive metal bent to form convex side 141 and concave side 143 . Spring 137 abuts contact 121 A on concave side 143 . Contact between spring 137 A and contact 121 A is maintained as rocker arm assembly 106 A undergoes motions associated with its normal operation. Those motions include raising and lowering due to lash adjustment and pivoting on hydraulic lash adjuster 140 . Spring 137 A may slide over a surface 151 of contact 121 A as these motions occur. The pivoting action may result in rotation of contact 121 A with little or no horizontal extension and contraction of spring 137 A. Spring 137 A remains in contact with contact 121 A as contact 121 A undergoes horizontal and vertical motion by flexing and or sliding over the surface of contact 121 A. The surface 151 of contact 121 A that contacts spring 137 A preferably conforms to the shape of spring 137 A to provide a large area of contact. In this example, conformity is achieved by making both surfaces parallel to pivot axis 150 (see FIG. 2 ).

Contact 121 A is proximate to but slightly off pivot axis 150 . Rocker arm assembly 106 A may be redesigned or the mounting of contact 121 A may be modified to reduce or eliminate this separation. Preferably, contact 121 A is 5 mm or less contact from axis 150 . More preferably, contact 121 A is 2 mm or less from axis 150 . More preferably, contact 121 A is 1 mm or less from axis 150 . Still more preferably, axis 150 passes through contact 121 A.

FIG. 4 is a method 300 of manufacturing an engine 100 . The method include action 301 , joining rocker arm assembly 106 A to hydraulic lash adjuster 140 using a spring 137 and installing rocker arm assembly 106 A together with hydraulic lash adjuster 140 in cylinder head 102 . Support frame 139 A may then be anchored to cylinder head 102 with bolts or the like.

FIGS. 5 and 6 illustrate an engine 100 B that is similar to engine 100 A except that it uses a spring 137 B in place of spring 137 A. Spring 137 B forms a hoop 145 that encircles contact 121 A. Rather than forming a complete hoop 145 , spring 137 B could simply wrap around contact 121 A to form an interference fit, thereby achieving much the same effect as hoop 145 using only a ribbon of conductive metal.

FIGS. 7-11 illustrates a rocker arm assembly 106 C and a hydraulic lash adjuster 140 of a valvetrain 104 C according to some aspects of the present teachings. Rocker arm assembly 106 C may be a switching rocker am including an inner arm 110 C, an outer arm 111 C selectively engaged by an electromagnetic latch assembly such as electromagnetic latch assembly 107 .

FIGS. 7 and 8 are perspective views that show a contact frame 501 mounted to outer arm 111 C and a support frame 139 C that fits around hydraulic lash adjuster 140 . Support frame 139 C may be bolted to a cylinder head 102 . FIGS. 9-11 are partial cutaway views showing that contact frame 501 supports and houses two contacts 121 C and that support frame 139 C supports and houses two springs 137 C. Power is provided to a coil 109 through springs 137 C and contacts 121 C.

With reference to FIG. 9 , spring 137 C is an accordion spring. An accordion spring is made from a ribbon of metal. Spring 137 C extends and contracts along a direction in which hydraulic lash adjuster 140 extends and contracts to adjust lash. Each spring 137 C includes a first arm 505 and a second arm 507 connected by a hoop 509 . First arm 505 and second arm 507 connect to hoop 509 through bends 511 that have a curvature opposite that of hoop 509 . Bends 511 allow hoop 509 to have a radius of curvature greater than a connection between first arm 505 and second arm 507 made with a constant radius of curvature. Hoop 509 may span an arc in the range between 280 and 320 degrees. This configuration keeps the stress on hoop 509 low as first arm 505 and second arm 507 undergo deflection.

Frame 139 C includes vertical sidewalls 515 , one on either side of each spring 137 C. Vertical sidewalls 515 are perpendicular to flat faces 517 (see FIG. 8 ) of springs 137 C and form boxes around springs 137 C that protect springs 137 C and prevent them from twisting. Contacts 121 C are also provided by flat strips of metal. A faces of contact 121 C abut a face of spring 137 C to provide an electrical connection 517 having a large surface area.

FIGS. 9-11 illustrate how springs 137 C maintain electrical connections 517 as rocker arm assembly 106 C undergoes various types of motions connected to normal operation of a valvetrain. FIG. 9 shows the position when cams (not shown) that act on with arm assembly 106 C are on base circle providing a valve-closed position and lash adjuster 140 is pumped up. FIG. 10 shows the case where rocker arm assembly 106 C has pivoted forward to open a valve under the influence of a cam to open a valve. The pivoting action has partially compressed spring 137 C. Contact 121 C has slid over spring 137 C, but contact 517 has been maintained. FIG. 11 shows the case where the cams acting on rocker arm assembly 106 C are on base circle, but lash adjuster 140 is pumped down. This causes spring 137 C to compress even more than the pivoting of rocker arm assembly 106 C but contact 517 is still maintained allowing operation of electromagnetic latch assembly 107 .

Contact 517 remains in proximity to axis 150 (See FIG. 10 ) on which rocker arm assembly 106 C pivots. One measure of that proximity is physical distance. That distance may be 5 mm or less, preferably 2 mm or less, more preferably 1 mm or less from axis 150 . Another measure of proximity is the ratio between distance moved by contact 517 (too small to clearly illustrate) as rocker arm assembly 106 C pivots in comparison to distance 521 (see FIG. 10 ) moved by a point 519 on rocker arm assembly 106 C that is most distal from axis 150 . The motion of contact 518 may be 20% or less the motion of point 519 , preferably 10% or less, more preferably 5% or less.

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.