Patent Description:
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.

In <CIT> there is disclosed a rocker arm for engaging a cam in a valve actuation arrangement includes a latch pin assembly having includes a latch pin, retainer, and biasing mechanism. The latch pin has a pin body with a head and a tail at the second end; the body defining an open volume; the tail having an open mouth in communication with the open volume of the body; and the open volume having a non-circular cross-section. The retainer has a male engagement portion and an outer portion. The male engagement portion is within the open volume of the body through the open mouth. The male engagement portion has a non-circular cross section. The outer portion is non- removably secured to an outer arm of the rocker arm. The biasing mechanism is oriented in the open volume of the body and between and against the latch pin and the retainer. Further rocker arm assemblies are shown in <CIT>, <CIT>, and <CIT>.

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. Electric latches generate magnetic fields. These fields may magnetize ferromagnetic parts. In some cases, it may be desirable to use latch components that include permanent magnets. Rocker arm assemblies operate in an environment that contains engine oil in which small particles of metal may be suspended. Solenoids and magnetized parts may draw these particles to locations where they could interfere with latch pin operation.

The present invention is a method of installing a valvetrain in an internal combustion engine as it is defined in claim <NUM>. The internal combustion engine includes a cylinder head, a poppet valve having a seat within the cylinder head, a cam shaft on which is mounted an eccentrically shaped cam, an electromagnetic latch assembly comprising a latch pin translatable between a first position and a second position, and a rocker arm assembly abutting the poppet valve. The rocker arm assembly includes a cam follower positioned to follow the cam and a rocker arm forming a chamber out of which the latch pin extends when the latch pin is in one of the first and second positions. One of the first and second latch pin positions provides a configuration in which the rocker arm assembly is operative to actuate the poppet valve in response to rotation of the cam shaft to produce a first valve lift profile. The other of the first and second latch pin positions provides a configuration in which the rocker arm assembly is operative to actuate the poppet valve in response to rotation of the cam shaft to produce a second valve lift profile, which is distinct from the first valve lift profile, or the poppet valve is deactivated.

A solenoid or a permanent magnet forming part of the electromagnetic latch assembly is mounted to the rocker arm. In embodiments, each of the permanent magnets is mounted within a chamber formed by the corresponding rocker arm. In some embodiments, the chamber is sealed against intrusion of metal particles that may be carried by oil in an environment surrounding the rocker arm. The permanent magnets remain within the chamber as the latch pin translates between the first position and the second position. In some embodiments, parts of the electromagnetic latch assembly including the magnetic element are rigidly mounted to the rocker arm.

The present invention may be used for retrofitting a hydraulically latched rocker arm assembly with an electromagnetic latch. Rocker arms for commercial applications are typically manufactured using customized casting and stamping equipment requiring a large capital investment.

In embodiments, the solenoid or a permanent magnet forming part of the electromagnetic latch assembly is rigidly mounted to the rocker arm and the electromagnetic latch assembly provides the latch pin with positional stability independently from the solenoid when the latch pin is in the first position and when the latch pin is in the second position. This dual positional stability enables the latch to retain both latched and unlatched states without reliance on the solenoid. The solenoid then does not need to be powered and need not be operative on the latch pin except for latch pin actuation, which may be limited to times at which the cam is on base circle. This can facilitate the implementation of an electromagnetic latch assembly a portion which is mounted on a rocker arm that moves rapidly at times over the course of its operating cycle. Installing a significant portion of an electromagnetic latch assembly, including at least the solenoid or a permanent magnet, on the rocker arm can provide a more compact design as compared to one in which an electromagnetic latch assembly is mounted off the rocker arm.

In embodiments, a permanent magnet contributes to the positional stability of the latch pin both when the latch pin is in the first position and when the latch pin is in the second position. In embodiments, the electromagnetic latch assembly is structured to operate through a magnetic circuit shifting mechanism. The electromagnetic latch assembly may provide two distinct magnetic circuits, one or the other of which is operative to be the primary path for magnet flux from the permanent magnet depending on the whether the latch pin is in the first position or the second position, absent magnetic fields from the solenoid or any external source that might alter the path taken by the magnetic flux. In some of these embodiments, actuating the latch pin may involve using the solenoid to redirect the permanent magnet's flux from the one circuit to the other. An electromagnetic latch assembly structured to be operable through a magnetic circuit shifting mechanism may be smaller than one that is not so structured. In some of these embodiments, the permanent magnet is fixedly mounted to the rocker arm. Fixing the permanent magnet to the rocker arm means not fixing the permanent magnet to the latch pin. Taking the weight of the permanent magnet off the latch pin may increase actuation speed and allow the use of a smaller solenoid.

In embodiments, the solenoid encircles a volume within which a portion of the latch pin comprising low coercivity ferromagnetic material translates and the electromagnetic latch assembly comprises one or more sections of low coercivity ferromagnetic material outside the volume encircled by the solenoid. Both the first and the second magnetic circuits pass through the latch pin portion formed of low coercivity ferromagnetic material. In some of these embodiments, the first magnetic circuit passes around the solenoid's coils via the one or more sections of low coercivity ferromagnetic material while the second magnetic circuit does not pass around the solenoid's coils. This characteristic of the second magnetic circuit reduces magnetic flux leakage and increases the holding force per unit mass provided by the permanent magnet when the latch pin is in the second position.

In some of these embodiments, the electromagnetic latch assembly includes a second permanent magnet distal from the first and fulfilling a complimentary role. The electromagnetic latch assembly may provide two distinct magnetic circuits for the second permanent magnet, one or the other of which is operative to be the primary path for magnet flux from the second permanent magnet depending on the whether the latch pin is in the first position or the second position. The path taken when the latch pin is in the second position may pass around the solenoid's coils via the one or more sections of low coercivity ferromagnetic material. The path taken when the latch pin is in the first position may be a shorter path that does not pass around the solenoid's coils. One or the other of the permanent magnets may then provide a high holding force depending on whether the latch pin is in the first or second positions. In some of these embodiments, both permanent magnets contribute to the positional stability of the latch pin in both the first and the second latch pin positions. In some of these embodiments, the two magnets are arranged with confronting polarities. In some of these embodiments, the two magnets are located at distal ends of the volume encircled by the solenoid. In some of these embodiments, the permanent magnets are annular in shape and polarized along the directions of the axes. These structures may be conducive to providing a compact and efficient design.

In some of the present teaching, the electromagnetic latch assembly includes at least one permanent magnet and the internal combustion engine has circuitry operable to energize the solenoid with a current in either a first direction or a second direction, which is the reverse of the first direction. A latch having dual positional stability may require the solenoid current to be in one direction for latching and the opposite direction for unlatching. The solenoid powered with current in the first direction may be operative to actuate the latch pin from the first position to the second position. The solenoid powered with current in the second direction may be operative to actuate the latch pin from the second position to the first position. In some others of these embodiments, the electromagnetic latch assembly include two solenoids, one for latching and the other for unlatching. The two solenoids may have windings in opposite directions. Employing two solenoid may allow for the control circuitry to be more robust. Employing only one solenoid may provide the most compact design.

Some of the present embodiments relate to powering or communicating with an electronic device such as a solenoid that is mounted to a rocker arm. If the electronic 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 disclosure provides embodiments that simplify or increase the reliability of these wiring connections.

According to some aspects of the present embodiments, the rocker arm includes a spring post and an electrical connection for the electronic device enters the rocker arm through the spring post. A lost motion spring maybe mounted to the spring post. The spring post may have a narrow range of motion relative to the cylinder head as compared to distal locations on the rocker arm. In some of these embodiments, the rocker arm has a valve end and a second end distal from the valve end and a slot entering the spring post is formed in one of the ends. Such a slot may facilitate installation of an electronic device with a wiring connection through the spring post.

According to some aspects of the present embodiments, an electrical connection for an electronic device mounted to a rocker arm is formed with a spring extending toward the rocker arm. The spring may be electrically isolated from the cylinder head, which may be grounded. In some of these embodiments, the current is carried by the spring itself. In some of these embodiments, the current is carried by a wire trace formed on the spring. In some of these embodiments, the current is carried by a wire bound along the length of the spring. The spring may stabilize the wiring connection. In some of these embodiments, the spring has a natural frequency tuned to dampen its oscillations caused by motion of the rocker arm. In some of these embodiments, the spring has a natural frequency greater than <NUM>. A frequency above <NUM> may be required for damping. In some of these embodiments, the spring is formed from a coiled metal ribbon. In some of these embodiments, the spring has the form of a spring clip.

According to the present invention, a valve actuation module is formed by attaching the plurality of rocker arms , corresponding hydraulic lash adjusters and a wiring harness to a frame. A wiring harness bound to the hydraulic lash adjuster may provide a good base from which to form an electrical connection to the rocker arm. In some of these teachings, the wiring harness is bound to a plurality of hydraulic lash adjusters and provides connections to rocker arms associated with each. The wiring harness bound to the hydraulic lash adjusters may facilitate installation of the valvetrain.

According to the present invention, there is formed a valve actuation module that includes a framework holding together a plurality of rocker arm assemblies each including at least one rocker arm with an electronic device mounted thereto and a hydraulic lash adjuster operative as a fulcrum for the rocker arm. The framework may support a wiring harness with connections to the electronic devices. In some of these embodiments, the valve actuation module includes removable connectors between the rocker arms and the hydraulic lash adjusters. In some of these embodiments, the removable connectors are breakaway connectors. The valve actuation module may be used to install a plurality of rocker arm assemblies and their wiring on a cylinder head simultaneously.

The primary purpose of this summary has been to present broad aspects of the present invention in a simplified form to facilitate understanding of the present disclosure. This summary is not a comprehensive description of every aspect of the present invention. Other aspects of the present invention will be conveyed to one of ordinary skill in the art by the following detailed description together with the drawings.

In the drawings, some reference characters consist of a number with a letter suffix. In this description and the claims that follow, a reference character consisting of that same number without a letter suffix is equivalent to a listing of all reference characters used in the drawings and consisting of that same number with a letter suffix. For example, "rocker arm <NUM>" is the same as "rocker arm 103A, 103B".

<FIG> illustrate an internal combustion engine <NUM> according to some aspects of the present invention. The views of <FIG> are cutaway side views. <FIG> is a non-cutaway side view corresponding to <FIG>. Internal combustion engine <NUM> includes a rocker arm assembly <NUM>, a poppet valve <NUM>, and a cam shaft <NUM> on which is mounted a cam <NUM>. Rocker arm assembly <NUM> includes an outer arm 103A, an inner arm 103B, and a hydraulic lash adjuster <NUM>. Outer arm 103A and inner arm 103B are selectively engaged by latch pin <NUM> of electromagnetic latch assembly <NUM>. Rocker arm assembly <NUM> is mounted on cylinder head <NUM>. Hydraulic lash adjuster <NUM> sits within a bore <NUM> formed in cylinder head <NUM>. Poppet valve <NUM> has a seat <NUM> within cylinder head <NUM>.

Rocker arms <NUM> are held in place by contact with hydraulic lash adjuster <NUM>, one or more cams <NUM>, and poppet valve <NUM>. Cam follower <NUM> is configured to abut and follow cam <NUM>. Cam follower <NUM> may be rotatably mounted to inner arm 103B through bearings <NUM> and axle <NUM>. In embodiments, cam follower <NUM> could instead be mounted to outer arm 103A. Rocker arm assembly <NUM> may include cam followers mounted to both inner arm 103B and outer arm 103A. Cam follower <NUM> is a roller follower. Another type of cam follower, such as a slider, may be used instead.

Outer arm 103A may be pivotally coupled to inner arm 103B through an axle <NUM>. Axle <NUM> may also support an elephant's foot <NUM> through which rocker arm assembly <NUM> acts on valve <NUM>. Axle <NUM> may be mounted on bearings or may be rigidly coupled to one of inner arm 103B, outer arm 103A, and elephant's foot <NUM>. As shown in <FIG>, a torsion spring <NUM>, or a pair thereof, may be mounted to outer arm 103A on spring posts <NUM>. Torsion springs <NUM> may act upwardly on axle <NUM> to create torque between inner arm 103B and outer arm 103A about axle <NUM> and bias cam follower <NUM> against cam <NUM>. Openings <NUM> may be formed in outer arm <NUM> to allow axle <NUM> to pass through it and move freely up and down.

<FIG> illustrates internal combustion engine <NUM> with cam <NUM> on base circle and latch pin <NUM> extended. This may be described an engaging position for latch pin <NUM> or an engaging configuration for rocker arm assembly <NUM>. <FIG> shows the result if cam <NUM> is rotated off base circle while latch pin <NUM> is in the engaging position. Initially head <NUM> of latch pin <NUM> engages lip <NUM> of inner arm 103B. The force of cam <NUM> on cam follower <NUM> may then cause both inner arm 103B and outer arm 103A to pivot together on hydraulic lash adjuster <NUM>, bearing down on valve <NUM> and compressing valve spring <NUM>. Valve <NUM> may be lifted off its seat <NUM> with a valve lift profile determined by the shape of cam <NUM>. The valve lift profile is the shape of a plot showing the height by which valve <NUM> is lifted of its seat <NUM> as a function of angular position of cam shaft <NUM>. In this configuration, cam shaft <NUM> may do work on rocker arm assembly <NUM> as cam <NUM> rises off base circle. Much of the resulting energy may be taken up by valve spring <NUM> and returned to cam shaft <NUM> as cam <NUM> descend back toward base circle.

Electromagnetic actuator <NUM> may be operated to retract latch pin <NUM>. <FIG> illustrates internal combustion engine <NUM> with cam <NUM> on base circle and latch pin <NUM> retracted. This may be described a non-engaging position for latch pin <NUM> or a non-engaging configuration for rocker arm assembly <NUM>. <FIG> shows the result if cam <NUM> is rotated off base circle while latch pin <NUM> is in the non-engaging position. In this configuration, the downward force on cam follower <NUM> applied by cam <NUM> as it rises off base circle may be distributed between valve <NUM> and torsion springs <NUM>. Torsions springs <NUM> may be tuned relative to valve spring <NUM> such that torsion springs <NUM> yield in the unlatched configuration while valve spring <NUM> does not. Torsion springs <NUM> may wind when inner arm 103B descends while outer arm 103A remains in place. As a result, valve <NUM> may remain on its seat <NUM> even as cam <NUM> rises off base circle. In this configuration, cam shaft <NUM> still does work on rocker arm assembly <NUM> as cam <NUM> rises of base circle. But in this case, most of the resulting energy is taken up by torsions springs <NUM>, which act as lost motion springs.

Hydraulic lash adjuster <NUM> may be replaced by a static fulcrum or other type of lash adjuster. Hydraulic lash adjuster <NUM> may include an inner sleeve <NUM> and an outer sleeve <NUM>. Lash adjustment may be implemented using a hydraulic chamber <NUM> that is configured to vary in volume as hydraulic lash adjuster <NUM> extends or contracts through relative motion of inner sleeve <NUM> and outer sleeve <NUM>. A supply port 146A may allow a reservoir chamber <NUM> to be filled from an oil gallery <NUM> in cylinder block <NUM>. The fluid may be engine oil, which may be supplied at a pressure of about <NUM> atm. When cam <NUM> is on base circle, this pressure may be sufficient to open check valve <NUM>, which admits oil into hydraulic chamber <NUM>. The oil may fill hydraulic chamber <NUM>, extending hydraulic lash adjuster <NUM> until there is no lash between cam <NUM> and roller follower <NUM>. As cam <NUM> rises off base circle, hydraulic lash adjuster <NUM> may be compressed, pressure in hydraulic chamber <NUM> may rise, and check valve <NUM> may consequently close.

In accordance with some aspects of the present invention, rocker arm assembly <NUM> may have been originally designed for use with a hydraulically latching rocker arm assembly. Accordingly a second supply port 146B may be formed in hydraulic lash adjuster <NUM> and communicate with a second reservoir chamber <NUM> in hydraulic lash adjuster <NUM>. Cylinder head <NUM> may not include any provision for supplying oil to second supply port 146B. Second reservoir chamber <NUM> may be isolated from any substantial flow of hydraulic fluid in cylinder head <NUM>. Reservoir chamber <NUM> and hydraulic passages communicating therewith may be essentially non-functional in engine <NUM>.

Internal combustion engine <NUM> has an end pivot overhead cam (OHC) type valvetrain. But some of the present teaching are applicable to internal combustion engines having other types of valvetrains including, for example, other types of OHC valvetrains and overhead valve (OHV) valvetrains that may include rocker arm assemblies that are latched. As used in the present disclosure, the term "rocker arm assembly" may refer to any assembly of components that is structured and positioned to actuate valve <NUM> in response to rotation of a cam shaft <NUM>. Rocker arm assembly <NUM> is a cylinder deactivating rocker arm. The present invention also is applicable to switching rocker arms and other types of rocker arm assemblies. In some embodiments, a rocker arm is a unitary metal piece. But a rocker arm may include multiple parts that are rigidly joined.

In accordance with some aspects of the present invention, components of electromagnetic latch assembly <NUM> are mounted within a chamber <NUM> formed in rocker arm 103A of rocker arm assembly <NUM>. Electromagnetic latch assembly <NUM> includes solenoid <NUM>, permanent magnets 120A, and permanent magnet 120B, each of which is rigidly mounted to rocker arm 103A. These parts may be rigidly mounted to rocker arm 103A by being rigidly mounted to other parts that are themselves rigidly mounted to rocker arm 103A. Electromagnetic latch assembly <NUM> further include latch pin <NUM> and low coercivity ferromagnetic pieces 116A, 116B, 116C, 116D, and 116E.

Latch pin <NUM> includes latch pin body <NUM>, latch head <NUM>, and a low coercivity ferromagnetic portion <NUM>. Low coercivity ferromagnetic portion <NUM> may be part of latch pin body <NUM> or may be a separate component such as an annular structure fitting around latch pin body <NUM>. Low coercivity ferromagnetic portion <NUM> provides a low reluctance pathway for magnetic circuits passing through latch pin <NUM> and may facilitate the application of magnetic forces to latch pin <NUM>.

Low coercivity ferromagnetic pieces <NUM> may be described as pole pieces in that they are operative within electromagnetic latch assembly <NUM> to guide magnetic flux from the poles of permanent magnets <NUM>. Low coercivity ferromagnetic pieces 116A, 116B, and 116C are located outside solenoid <NUM> and may form a shell around it. Low coercivity ferromagnetic pieces 116D may provide stepped edges in magnetic circuits formed by electromagnetic latch assembly <NUM>. Low coercivity ferromagnetic portion <NUM> of latch pin <NUM> may be shaped to mate with these edges. During actuation, magnetic flux may cross an air gap between one of these stepped edge and latch pin <NUM>, in which case the stepped edge may be operative to increase the magnetic forces through which latch pin <NUM> is actuated.

Solenoid <NUM> comprises a large number of coils that wrap around a volume <NUM>. In some of these teaching permanent magnets <NUM> are positioned within volume <NUM>. Low coercivity ferromagnetic pieces 116D and 116E may also be positioned within volume <NUM>. In some of these embodiments, permanent magnets 120A and permanent magnets 120B are arranged with confronting polarities. In some of these embodiments, Low coercivity ferromagnetic piece 116E is positioned between the confronting poles and provides a pole piece for both magnets <NUM>. In some of these embodiments, permanent magnets 120A and 120B are located at distal ends of volume <NUM>. In some of these embodiments, permanent magnets <NUM> are annular in shape and polarized in a direction parallel to that in which latch pin <NUM> translates. This may be along a central axis for solenoid <NUM>.

In accordance with some aspects of the present embodiments, electromagnetic latch assembly <NUM> provides both extended and retracted positions in which latch pin <NUM> is stable. As a consequence, either the latched or unlatched configuration can be reliably maintained without solenoid <NUM> being powered. Positional stability refers to the tendency of latch pin <NUM> to remain in and return to a particular position. Stability is provided by restorative forces that acts against small perturbations of latch pin <NUM> from a stable position. In accordance with some of the present embodiments, in electromagnetic latch assembly <NUM> stabilizing forces are provided by permanent magnets <NUM>. Alternatively or in addition, one or more springs may be positioned to provide positional stability. Springs may also be used to bias latch pin <NUM> out of a stable position, which may be useful for increasing actuation speed.

In accordance with some aspects of the present embodiments and as shown in <FIG>, electromagnetic latch assembly <NUM>, permanent magnet 120A stabilizes latch pin <NUM> in both the extended and the retracted positions. In accordance with other aspects of the present embodiments, electromagnetic latch assembly <NUM> forms two distinct magnetic circuits <NUM> and <NUM> to provide this functionality. As shown in <FIG>, magnetic circuit <NUM> is operative to be the primary path for magnet flux from permanent magnet 120A when latch pin <NUM> is in the extended position, absent magnetic fields from solenoid <NUM> or any external source that might alter the path taken by flux from permanent magnet 120A.

Magnetic circuit <NUM> proceeds from the north pole of permanent magnet 120A, through pole piece 116E, through latch pin <NUM>, through a pole piece 116D and pole piece 116A and ends at the south pole of permanent magnet 120A. Path <NUM> is operative to be the primary path for magnet flux from permanent magnet 120A when latch pin <NUM> is in the extend position. A primary magnetic circuit is a magnetic circuit taken by the majority of flux from a magnet. Perturbation of latch pin <NUM> from the extended position would introduce an air gap into magnetic circuit <NUM>, increasing its magnetic reluctance. Therefore, the magnetic forces produced by permanent magnet 120A resist such perturbations.

As shown in <FIG>, magnetic circuit <NUM> is operative to be the primary path for magnet flux from permanent magnet 120A when latch pin <NUM> is in the retracted position, absent magnetic fields from solenoid <NUM> or any external source that might alter the path taken by flux from permanent magnet 120A. Magnetic circuit <NUM> proceeds from the north pole of permanent magnet 120A, through pole piece 116E, through latch pin <NUM>, through a pole piece 116D, through pole pieces 116C, 116B, and 116A, and ends at the south pole of permanent magnet 120A. Path <NUM> is operative to be the primary path for magnet flux from permanent magnet 120A when latch pin <NUM> is in the retracted position. Perturbations of latch pin <NUM> from the retracted position would introduce an air gap into magnetic circuit <NUM>, increasing its magnetic reluctance. Therefore, the magnetic forces produced by permanent magnet 120A resist such perturbations.

In embodiments, electromagnetic latch assembly <NUM> also includes a second permanent magnet 120B that is also operative to stabilize latch pin <NUM> in both the extended and the retracted positions. Electromagnetic latch assembly <NUM> forms two distinct magnetic circuits <NUM> and <NUM> for magnetic flux from second permanent magnet 120B. Magnetic circuit <NUM> is operative to be the primary path for magnet flux from permanent magnet 120B when latch pin <NUM> is in the extended position and magnetic circuit <NUM> is operative to be the primary path for magnet flux from permanent magnet 120B when latch pin <NUM> is in the retracted position. Like magnetic circuit <NUM>, magnetic circuit <NUM> goes around the outside of solenoid <NUM>. Like magnetic circuit <NUM>, magnetic circuit <NUM> does not.

Electromagnetic latch assembly <NUM> is structured to operate through a magnetic circuit shifting mechanism. <FIG> illustrates this for the case in which solenoid <NUM> is operated to induce latch pin to actuate from the extended position to the retracted position. A voltage of suitable polarity may be applied to solenoid <NUM> to induce magnetic flux following the circuit <NUM>. The magnetic flux from solenoid <NUM> reverses the magnetic polarity in low coercivity ferromagnetic elements forming the magnetic circuits <NUM> and <NUM> through which permanent magnets <NUM> stabilized latch pin <NUM> in the extended position. This greatly increase the reluctance of magnetic circuit <NUM> and <NUM>. Magnetic flux from permanent magnets <NUM> may shift from magnetic circuits <NUM> and <NUM> toward magnetic circuits <NUM> and <NUM>. The net magnetic forces on latch pin <NUM> may drive it to the retracted position shown in <FIG>. In accordance with some aspects of the present invention, the total air gap in the magnetic circuit <NUM> taken by flux from solenoid <NUM> does not vary as latch pin <NUM> actuates. This feature may relate to operability through a flux shifting mechanism.

One way in which electromagnetic latch assembly <NUM> may be identified as having a structure that provides for a magnetic circuit shifting mechanism is that solenoid <NUM> does not need to do work on latch pin <NUM> throughout its traverse from the extended position to the retracted position or vis-versa. While permanent magnets <NUM> may initially holds latch pin <NUM> in a first position, at some point during latch pin <NUM>'s progress toward the second position, permanent magnets <NUM> begins to attract latch pin <NUM> toward the second position. Accordingly, at some point during latch pin <NUM>'s progress, solenoid <NUM> may be disconnected from its power source and latch pin <NUM> will still complete its travel to the second position. And as a further indication that a magnetic circuit shifting is formed by the structure, a corresponding statement may be made in operation of solenoid <NUM> to induce actuation from the second position back to the first. Put another way, a permanent magnet <NUM> that is operative to attract latch pin <NUM> into the first position is also operative to attract latch pin <NUM> into the second position.

As used herein, a permanent magnet is a high coercivity ferromagnetic material with residual magnetism. A high coercivity means that the polarity of permanent magnet <NUM> remains unchanged through hundreds of operations through which electromagnetic latch assembly <NUM> is operated to switch latch pin <NUM> between the extended and retracted positions. Examples of high coercivity ferromagnetic materials include compositions of AlNiCo and NdFeB.

Magnetic circuits <NUM>, <NUM>, <NUM>, <NUM> may be formed by low coercivity ferromagnetic material, such as soft iron. These circuit may have little or no air gaps. Magnetic circuits <NUM>, <NUM>, <NUM>, <NUM> may have low magnetic reluctance. In accordance with some aspects of the present invention, permanent magnets <NUM> have at least one low reluctance magnetic circuit available to them in each of the extended and retracted positions. These paths may be operative as magnetic keepers, maintaining polarization and extending the operating life of permanent magnets <NUM>.

Low coercivity ferromagnetic pieces <NUM> may form a shell around solenoid <NUM>. In some of these embodiments, a rocker arm <NUM> to which solenoid <NUM> is mounted is formed of a low coercivity ferromagnetic material, such as a suitable steel, and the rocker arm <NUM> may be consider as providing these pieces or fulfilling their function.

In accordance with some aspects of the present invention, magnetic circuits <NUM> and <NUM> are short magnetic circuits between the poles of permanent magnets 120A and 120B respectively. Magnetic circuits <NUM> and <NUM> pass through low coercivity ferromagnetic portion <NUM> of latch pin <NUM> but not around the coils of solenoid <NUM>. These short magnetic circuits may reduce magnetic flux leakage and allow permanent magnets <NUM> to provide a high holding force for latch pin <NUM>. Magnetic circuits <NUM> and <NUM>, on the other hand, pass around the coils of solenoid <NUM>. Routing these magnetic circuits around the outside of solenoid <NUM> may keep them from interfering with the shorter magnetic circuits. These longer, alternate magnetic circuits can allow permanent magnets <NUM> to contribute to stabilizing latch pin <NUM> in both extended and retracted positions and can assure there is a low reluctance magnetic circuit to help maintain the polarization of permanent magnets <NUM> regardless of whether latch pin <NUM> is in the extended or the retracted position.

In accordance with some aspects of the present invention, electromagnetic latch assembly <NUM> is operative to actuate latch pin <NUM> between the extended and retracted positions by redirecting flux from permanent magnet <NUM>.

In accordance with some aspects of the present invention, solenoid <NUM> is powered by circuitry (not shown) that allows the polarity of a voltage applied to solenoid <NUM> to be reversed. A conventional solenoid switch forms a magnetic circuit that include an air gap, a spring that tends to enlarge the air gap, and an armature moveable to reduce the air gap. Moving the armature to reduce the air gap reduces the magnetic reluctance of that circuit. As a consequence, energizing a conventional solenoid switch causes the armature to move in the direction that reduces the air gap regardless of the direction of the current through the solenoid or the polarity of the resulting magnetic field. As described above, however, latch pin <NUM> of electromagnetic latch assembly <NUM> may be moved in either one direction or another depending on the polarity of the magnetic field generated by solenoid <NUM>. Circuitry, an H-bridge for example, that allows the polarity of the applied voltage to be reversed enables the operation of electromagnetic latch assembly <NUM> for actuating latch pin <NUM> to either an extended or a retracted position. Alternatively, one voltage source may be provided for extending latch pin <NUM> and another for retracting latch pin <NUM>. Another alternative is provide solenoid <NUM> as two electrically isolated coils, one with coils wound in a first direction and the other with coils wound in the opposite direction. One or the other set of coils may be energized depending on the position in which it is desired to place latch pin <NUM>.

<FIG> provides a flow chart of a method <NUM> illustrating some aspects of the present invention that may be used to operate internal combustion engine <NUM>. Method <NUM> begins with action <NUM>, holding latch pin <NUM> in a first position using a magnetic field generated by a first permanent magnet 120A and following a magnetic circuit <NUM> that encircles the coils of solenoid <NUM>. Such a magnetic circuit may include a segment passing through solenoid <NUM> and a segment that is outside solenoid <NUM>. The first position may correspond to either an extended or a retracted position for latch pin <NUM>. In some of these embodiments, action <NUM> further includes holding latch pin <NUM> in the first position using a magnetic field generated by a second permanent magnet 120B and following a shorter magnetic circuit <NUM> that does not encircles the coils of solenoid <NUM>.

Method <NUM> continues with action <NUM>, energizing solenoid <NUM> with a current in a forward direction to alter the circuit taken by flux from first permanent magnet 120A and cause latch pin <NUM> to translate to a second position. Energizing solenoid <NUM> with a current in a forward direction may also alter the circuit taken by flux from a second permanent magnet 120B. Action <NUM> may be initiated by an automatic controller. In some of these embodiments, the controller is an ECU.

Following translation of latch pin <NUM> to the second position through action <NUM>, solenoid <NUM> may be disconnected from its power source with action <NUM>. Method <NUM> then continues with action <NUM>, holding latch pin <NUM> in the second position using a magnetic field generated by a first permanent magnet 120A and following a magnetic circuit <NUM> that does not encircles the coils of solenoid <NUM>. This may be a short magnetic circuit with low magnetic flux leakage. In some of these embodiments, action <NUM> further includes holding latch pin <NUM> in the second position using a magnetic field generated by a second permanent magnet 120B and following a magnetic circuit <NUM> that encircles the coils of solenoid <NUM>.

Method <NUM> may continue with action <NUM>, energizing solenoid <NUM> with a current in a reverse direction to again alter the circuit taken by flux from first permanent magnet 120A and cause latch pin <NUM> to translate back to the first position. Energizing solenoid <NUM> with a current in a reverse direction may also alter the circuit taken by flux from a second permanent magnet 120B. Action <NUM> also may be initiated by an automatic controller, such as an ECU. Action <NUM> may then be carried out, again de-energizing solenoid <NUM>. The action of method <NUM> may subsequently repeat.

In accordance with some aspects of the present invention, electromagnetic latch assembly <NUM> has dual positional stability and may be operated by the method <NUM>. In some embodiments, however, electromagnetic latch assembly <NUM> may be a different type of latch such as a conventional solenoid switch that forms a magnetic circuit that include an air gap, a spring that tends to enlarge the air gap, and an armature moveable to reduce the air gap. This conventional switch may have only one stable position, one maintained by a spring for example. The stable position may correspond to an extended or a retracted position for latch pin <NUM>. The other position may be maintained by continuously powering solenoid <NUM>.

In accordance with some aspects of the present disclosure, magnetic components of electromagnetic latch assembly <NUM> are housed in a chamber <NUM> formed in rocker arm <NUM>. The magnetic component housed in chamber <NUM> are permanent magnets 120A and 120B and solenoid <NUM>. In some of these embodiments, chamber <NUM> is sealed against intrusion from metal particles that may be in oil dispersed throughout the environment <NUM> surrounding rocker arm assembly <NUM>. Openings off chamber <NUM> may be sealed in any suitable manner consistent with the objective. For examples, a Sealing of chamber <NUM> may be provided in part by a seal around latch pin <NUM> at a location where latch pin <NUM> extends out of chamber <NUM>. Pole piece 116C or another component may seal off an opening through which parts of electromagnetic latch assembly <NUM> may have been installed in chamber <NUM>.

In accordance with some aspects of the present invention, chamber <NUM> is a hydraulic chamber. Chamber <NUM> may have been adapted to house parts of electromagnetic latch assembly <NUM>. In accordance with some of these embodiments, rocker arm assembly <NUM> is made using rocker arms <NUM> put into production for use with a hydraulically actuated latch. In accordance with some of these embodiments, an electric latch assembly <NUM> has been installed in place of a hydraulic latch. While chamber <NUM> is a hydraulic chamber, it need not be functionally connected to a hydraulic system. A hydraulic passage <NUM> may connect to chamber <NUM>. Hydraulic passage <NUM> may be blocked to help seal chamber <NUM>. In some of these teaching, hydraulic passage <NUM> couples with a hydraulic passage <NUM> formed in hydraulic lash adjuster <NUM>.

In accordance with some aspects of the present embodiments, some magnetic components of electromagnetic latch assembly <NUM> are retained within chamber <NUM>. These may include permanent magnets 120A and 120B and solenoid <NUM>. Alternatively, solenoid <NUM> may be mounted at any location where it is operative when energized to generate a magnetic field that operates on electromagnetic latch assembly <NUM> to actuate latch pin <NUM>. Actuating latch pin <NUM> may be moving latch pin <NUM> between an extended position and a retracted position.

It has been determined that a solenoid <NUM> of sufficient power can be fit in a chamber <NUM> of rocker arm <NUM>. In particular, simulations have shown that solenoid <NUM> may have a <NUM> outer diameter, a <NUM> inner diameter, and a <NUM> length. It may have <NUM> turns of <NUM> AWG copper wire. It may be powered at <NUM> VDC with a maximum current of <NUM> A. A peak electromagnetic force of <NUM> N on latch pin 115A may be realized with the aid of a shell <NUM> having a thickness of <NUM>. Latch pin weight can be limited to about <NUM>. Frictional resistance may be limited to <NUM> N @ <NUM>, with much lower friction expected at higher temperatures. Under these conditions, solenoid <NUM> may drive latch pin <NUM> through a distance of <NUM> in <NUM>. In some of the present embodiments, solenoid <NUM> has a diameter of <NUM> or less. In some of these embodiments, solenoid <NUM> has a diameter of <NUM> or less. These dimensions facilitate fitting solenoid <NUM> into a chamber <NUM> formed in rocker arm <NUM>.

In some of the present embodiments, the displacement required to actuate latch pin <NUM> from the first the second position is <NUM> or less, e.g., about <NUM>. Actuating latch pin <NUM> may be operative to change valve lift timing. In some of these embodiments, rocker arm assembly <NUM> is a cylinder deactivating rocker arm and actuating latch pin <NUM> activates or deactivates valve <NUM>. In some alternative embodiments, rocker arm assembly <NUM> is a switching rocker arm. A switching rocker arm may be operative to provide VVL. A switching rocker arm may include an inner arm <NUM> and an outer arm <NUM> that are selectively engaged by a latch pin <NUM> and actuating latch pin <NUM> switches the valve lift timing between a first profile and a second profile.

<FIG> provides a flow chart of a manufacturing method <NUM> illustrating some aspects of the present invention. Method <NUM> begins with action <NUM>, a design operation in which a rocker arm assembly <NUM> including a hydraulically actuated latch may be designed in detail. The design may be made without specifications for an electromagnetic latch assembly <NUM>. Method <NUM> continues with action <NUM>, building casting and stamping equipment sufficient for implementing the design of action <NUM>. Action <NUM> is using that equipment to manufacture a rocker arm 103A having a hydraulic latch chamber <NUM>.

Act <NUM> is forming a slot <NUM> in end <NUM> of rocker arm <NUM> through to spring posts <NUM> as shown in <FIG>. Slot <NUM> intersects chamber <NUM>. This enables the subsequent act <NUM>, installing solenoid <NUM> in chamber <NUM> with a wire <NUM> emerging from one of the spring posts <NUM>. In some of these embodiments, wires <NUM> may emerge from both spring posts <NUM>. In some others of these embodiments, solenoid <NUM> is grounded through the structure of rocker arm assembly <NUM> which is in turn grounded through cylinder head <NUM>. In that case, only one wire is required. That wire can be electrically isolated from cylinder head <NUM> and raised to a substantially higher electrical potential. Optionally, action <NUM> includes installing the entire electromagnetic latch assembly <NUM> on rocker arm <NUM>.

Action <NUM> is sealing hydraulic latch chamber <NUM> against intrusion by metal particles that may be in oil dispersed in the environment <NUM> surrounding rocker arm assembly <NUM>. This may include installing a seal ring around an opening <NUM> out of which latch pin <NUM> extends, closing off an opening <NUM> through which electromagnetic latch assembly <NUM> is installed in chamber <NUM>, closing of a hydraulic passage <NUM>, and closing off slot <NUM>. In some of these embodiments, electromagnetic latch assembly <NUM> itself forms a sealed chamber within hydraulic chamber <NUM>. Electromagnetic latch assembly <NUM> may be provided with a shell for this purpose. In some of these embodiments, electromagnetic latch assembly <NUM> cooperates with the structure of rocker arm 103A to complete the sealing of chamber <NUM>.

<FIG> is a flow chart of a method <NUM> of manufacturing an internal combustion engine <NUM> illustrating some aspects of the present invention. Method <NUM> may begin with action <NUM>, temporarily joining rocker arms <NUM> and HLAs <NUM>. In accordance with some of the present teaching, these parts may be joined with connectors <NUM> as shown in <FIG>. Connectors <NUM> may be any type of connector that can hold rocker arms <NUM> and HLAs <NUM> together during installation and easily removed after installation. In some of these embodiments, connectors <NUM> are made of plastic or cardboard. Connectors <NUM> may be formed of a material unsuited for engine operating conditions. In some of these embodiments, connectors <NUM> have weak points <NUM> formed or designed into their structure. Connectors <NUM> may be identifiable as breakaway connectors. Connectors <NUM> may join rocker arms <NUM> and HLAs <NUM> directly, or may join rocker arms <NUM> to a frame <NUM> to which HLAs <NUM> are joined.

Method <NUM> may include action <NUM>, attaching HLAs <NUM> to frame <NUM>. In accordance with the present invention, frame <NUM> maintains spacing between HLAs <NUM> that is equivalent to their spacing when installed within internal combustion engine <NUM>. In some of these embodiments, frame <NUM> wraps at least most of the way around a cylindrical portion of each of the HLAs <NUM>.

Action <NUM> is attaching a wiring harness <NUM> to frame <NUM>. Wiring harness <NUM> may include a plurality of wires <NUM> connecting to distinct HLAs <NUM>. Each of the wires <NUM> may be coupled to a separate pin of connection plug <NUM>. Wiring harness <NUM> may provide a conduit surrounding and protecting wires <NUM>.

Action <NUM> is installing connectors <NUM> that make electrical connections between wires <NUM> of wiring harness <NUM> and wires <NUM> of solenoids <NUM>. In accordance with some aspects of the present invention, connectors <NUM> are formed with springs <NUM> as shown in <FIG>. Spring <NUM> may have a natural frequency greater than <NUM>. The same springs <NUM> that provide this degree of stiffness may also be operative to carry current form solenoid <NUM>. Alternatively, wire traces may be provided on the springs <NUM> for carrying the current. Another option is to bind current carrying wires along the length of the springs <NUM>. Bound along the length means continuously bound or multiple bindings distributed along the length.

Springs <NUM> may be any suitable type of spring. In most of the illustrations, spring <NUM> are shown as being formed from a coiled metal ribbon. <FIG> shows an alternative design with springs 149A in the form of spring clips. The present teaching of using springs <NUM> to form electrical connections to a rocker arm <NUM> are applicable to powering or communicating with any type of electrical device that may be mounted on rocker arm <NUM>. The connection may be made from rocker arm <NUM> to any suitable location. A suitable location may be stationary with respect to cylinder head <NUM>.

In some of the present embodiments, springs <NUM> are used to form connections to a wiring harness <NUM>. In some of these embodiments, wiring harness <NUM> is mounted to a frame <NUM>. Frame <NUM> may be mounted at any suitable location. A suitable location may be stationary with respect to cylinder head <NUM>. In some of these embodiments frame <NUM> is mounted to HLAs <NUM>. In some of these embodiments frame <NUM> is mounted to cylinder head <NUM>, a cam carrier (not shown), or a valve cover (not shown). In alternate embodiments, springs <NUM> make connections to a wiring harness <NUM> that is mounted directly to an HLA <NUM>, a cylinder head <NUM>, a cam carrier, or a valve cover.

Alternatively, solenoids <NUM> may be electrically connected to wiring harness <NUM> and connection plug <NUM> without springs. For example, the connections can be made with wires that are specially designed to endure the motion induced by rocker arm 103A. If such wires are used, they may be connected to solenoids <NUM> prior to mounting on rocker arm 103A in accordance with method <NUM>. According to some aspects of the present invention, prior to mounting solenoid <NUM> on rocker arm 103A, wires are connected to solenoid <NUM> having sufficient length to run continuously from solenoids <NUM> to connection plug <NUM>. Such wires can be gathered together to form wiring harness <NUM>.

Actions <NUM> through <NUM> together form a valve actuation module <NUM> in accordance with some aspects of the present invention. A valve actuation module <NUM> formed in accordance with the present invention is illustrated by <FIG>. In accordance with the present invention, valve actuation module <NUM> formed includes at least two rocker arm assemblies <NUM>. In some of these embodiments, valve actuation module <NUM> includes four rocker arm assemblies <NUM>. Four rocker arm assemblies <NUM> may be the number installed between adjacent pairs of cam towers (not shown) in engine <NUM>. In accordance with some of these embodiments, valve actuation module <NUM> includes electrical connections for a plurality of solenoids <NUM>.

Action <NUM> is installing valve actuation module <NUM> in cylinder head <NUM>. In accordance with the present invention, this may include installing all the HLAs <NUM> of valve actuation module <NUM> simultaneously in openings formed in cylinder head <NUM>. Action <NUM> may be simply dropping valve actuation module <NUM> onto cylinder head <NUM>. Action <NUM> is removing the connectors <NUM> joining rocker arms <NUM> to HLAs <NUM> or frame <NUM>. Action <NUM> is plugging connection plug <NUM> into the electrical system (not shown) of internal combustion engine <NUM>. The actions of method <NUM> may take place in any order consistent with the logic of this method.

Claim 1:
A method of installing a valvetrain in an internal combustion engine (<NUM>) comprising
a cylinder head (<NUM>),
a poppet valve (<NUM>) having a seat (<NUM>) within the cylinder head (<NUM>),
a cam shaft (<NUM>) on which is mounted an eccentrically shaped cam (<NUM>),
an electromagnetic latch assembly (<NUM>) comprising a latch pin (<NUM>) translatable between a first position and a second position; and
a rocker arm assembly (<NUM>) abutting the poppet valve (<NUM>) and comprising:
a cam follower (<NUM>) positioned to follow the cam (<NUM>); and
a rocker arm (<NUM>) forming a chamber (<NUM>) out of which the latch pin (<NUM>) extends when the latch pin is in one of the first and second positions;
wherein one of the first and second latch pin positions provides a configuration in which the rocker arm assembly (<NUM>) is operative to actuate the poppet valve (<NUM>) in response to rotation of the cam shaft (<NUM>) to produce a first valve lift profile;
the other of the first and second latch pin positions provides a configuration in which the rocker arm assembly (<NUM>) is operative to actuate the poppet valve (<NUM>) in response to rotation of the cam shaft (<NUM>) to produce a second valve lift profile, which is distinct from the first valve lift profile, or the poppet valve is deactivated; and
a solenoid (<NUM>) and two permanent magnets (120A, 120B) forming part of the electromagnetic latch assembly (<NUM>) is mounted to the rocker arm (<NUM>);
the method comprising:
mounting an electromagnetic latch assembly (<NUM>) to each of a plurality of rocker arms (<NUM>);
forming a valve actuation module (<NUM>) by attaching the plurality of rocker arms (<NUM>), corresponding hydraulic lash adjusters (<NUM>), and a wiring harness (<NUM>) to a frame (<NUM>); and installing the valve actuation module (<NUM>) on the cylinder head (<NUM>) so that the rocker arm assemblies abut poppet valves (<NUM>) and the hydraulic lash adjusters (<NUM>) provide fulcrums for the rocker arms (<NUM>);
installing connectors (<NUM>) that make electrical connections between wires (<NUM>) of wiring harness (<NUM>) and wires (<NUM>) of each solenoid (<NUM>), thereby facilitating installation of a valvetrain.