Field

[0001] The present teachings relate to valvetrains, particularly valvetrains providing variable valve lift (VVL) or cylinder deactivation (CDA).

Background

[0002] Hydraulically actuated latches are used on some rocker arm assemblies to implement variable valve lift (WL) 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.

Summary

[0003] The complexity and demands for oil in some valvetrain systems can be reduced by replacing hydraulic latches with solenoid-actuated magnetic latches.

According to some aspects of the present teachings, magnetic latches, like hydraulic latches, are incorporated into the rocker arm assembly. This may provide a compact design suitable for the limited space available under the valve cover, but conventionally powering rocker arm assembly-mounted solenoid-actuated magnetic latches could involve attaching wire pairs to the rocker arm assemblies. Rocker arm assemblies reciprocate rapidly over a prolonged period and in proximity to other moving parts. Wires attaching to the rocker arm assemblies could be caught, clipped, or fatigued and consequently short out.

[0004] The present teachings relate to an internal combustion engine. The internal combustion engine may include a cylinder head, a poppet valve having a seat formed within the cylinder head, a cam shaft, a cam mounted to the cam shaft, and a rocker arm assembly including a rocker arm, a cam follower, and a magnetic latch including a latch pin. An actuator for the magnetic latch includes a solenoid and is operative to cause the latch pin to translate between the first and second positions. Actuating the latch pin to the first position may configure the rocker arm assembly to actuate the poppet valve in response to rotation of the cam shaft to produce a first valve lift profile. Actuating the latch pin to the second position may configure the rocker arm assembly 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 may deactivate the poppet valve.

[0005] According to some aspects of the present teachings, the magnetic latch is mounted to a rocker arm of the rocker arm assembly and the actuator is mounted off the rocker arm. In some of these teachings, the actuator is mounted in a position that is fixed with respect to the cylinder head of the internal combustion engine. In some of these teachings, the solenoid is mounted to the cylinder head, a cam carrier, or a valve cover. Mounting off the rocker arm allows the wire positions to be static.

[0006] According to some aspects of the present teachings, the actuator is operative to cause the latch pin to actuate or maintain a latch pin position through a magnetic field that crosses an air gap between the actuator and the magnetic latch. In some of these teachings, the solenoid is operative to generate the magnetic field. In some of these teachings, a permanent magnet generates the magnetic field. The actuator may be operative to redirect the flux from the permanent magnet and thereby cause the latch pin to actuate.

[0007] In some of these teachings, a low coercivity ferromagnetic portion of the magnetic latch extends out from the rocker arm in the direction of the actuator to facilitate the interaction between the magnetic latch and the actuator. In some of these teachings, that portion of the magnetic latch is part of the latch pin. In some of these teachings, that portion of the magnetic latch is a pole piece that is rigidly mounted to the rocker arm. [0008] According to some aspects of the present teachings, the magnetic latch has both engaging and non-engaging configurations that are stable independently from the actuator. The two configurations may correspond to the first and second positions of the latch pin. In some of these teachings, the internal combustion engine has circuitry operable to energize a solenoid of the actuator with a current in either a first direction or a reverse of the first direction. The solenoid powered with current in the first direction maybe 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 teachings, the electromagnetic latch assembly includes two solenoids, one for latching and the other for unlatching. The two solenoids may have windings in opposite directions.

[0009] According to some aspects of the present teachings, a permanent magnet is operative to stabilize the latch pin in both the first and the second positions. In some of these teachings, the permanent magnet is part of the magnetic latch. In some others of these teachings, the permanent magnet is part of the actuator. In some of these teachings, absent any magnetic fields generated by the solenoid or other external sources, when the latch pin is in the first position, the majority of magnetic flux from the permanent magnet follows a first magnetic circuit and when the latch pin is in the second position, the majority of magnetic flux from the permanent magnet follows a second magnetic circuit distinct from the first magnetic circuit. The actuator may be operative to redirect the permanent magnet's flux away or toward one or the other of these magnetic circuits and thereby cause the latch pin to actuate. In some of these teachings redirecting the magnetic flux includes reversing the magnetic polarity in a low coercivity ferromagnetic element forming part of both the first and second magnetic circuits. In some of these teachings, the element is part of the latch pin. A magnetic latch operating on a flux-shifting principle may be made compact and thus more suitable for mounting on a rocker arm.

[0010] According to some aspects of the present teachings, at least one of the magnetic circuits passes through the actuator. A magnetic circuit passing through the actuator may facilitate actuation of the latch pin though operation of the solenoid. In some of these teachings, the other circuit does not pass through the actuator. The circuit not passing through the actuator may be much shorter, have lower magnetic flux leakage, and allow the permanent magnet to apply a greater holding force to the latch pin.

[0011] In some of these teachings, the magnetic latch comprises two permanent magnets, both of which are operative to stabilize the latch pin in both the first and the second positions. The second permanent magnet may also be part of the magnetic latch or part of the actuator. When the latch pin is in the first position, the majority of magnetic flux from the second permanent magnet follows a third magnetic circuit and when the latch pin is in the second position, the majority of magnetic flux from the permanent magnet follows a fourth magnetic circuit distinct from the third magnetic circuit. The actuator may be operative to redirect the second permanent magnet's flux away or toward one or the other of these magnetic circuits and thereby cause the latch pin to actuate. In some of these teachings, one of the third and fourth circuits passes through the actuator and the other does not. In each of the latch pin positions, one of the active magnetic circuits may provide a short flux path that results in a high holding force on the latch pin and the other magnetic circuit may pass through the actuator and facilitate actuation of the latch pin though operation of the solenoid.

[0012] According to some aspects of the present teachings, a permanent magnet that is operative to stabilize the latch pin in both its first and second positions is mounted fixedly with respect to a rocker arm on which the magnetic latch is mounted. 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 some of these teachings, the permanent magnet is annular. In some of these teachings, the permanent magnet if polarized in the direction the latch pin translates. In some of these teachings, the permanent magnet is positioned concentrically with respect to the latch pin. A permanent magnet so configured may provide a compact design. In some of these teachings, there are two such permanent magnets arranged with confronting polarity. In some of these teachings, the two magnets are at opposite ends of the magnetic latch. In some of these teachings, an annular ring of low coercivity

ferromagnetic material is located between the two magnets. The annular ring may provide a pole piece for both magnets.

[0013] According to some aspects of the present teachings, the magnetic latch is mounted to a rocker arm of the rocker arm assembly and, along with the rocker arm, has a range of motion relative to the actuator. The position of the magnetic latch relative to the actuator may be affected at times by the position of the cam. In some of these teachings, the rocker arm assembly and the magnetic latch are configured such that the actuator does not need to be operative on the latch except within a limited portion of latch's range of motion. In some of these teachings, the magnetic latch is operative to keep the latch pin position stable independently from the actuator in both the engaging and non-engaging configurations. Actuation may be effectuated only when the cam is on base circle.

[0014] In some of these teachings, the rocker arm assembly is configured whereby the rocker arm to which the magnetic latch is mounted remains substantially stationary when the latch pin is in a non-engaging configuration. The engaging configuration may be maintained by the magnetic latch independently from the actuator. In some of these teachings, the engaging configuration is maintained by a spring. If the actuator need only be operative on the latch when the rocker arm is in one particular position, a structure maintaining sufficient proximity between the solenoid and the magnetic latch is more easily achieved. In some of these teachings, in the engaging configuration, with each cycle of the cam the rocker arm reaches a position in which the actuator is operative to apply a magnetic force to the latch pin sufficient to overcome the spring force and hold the latch pin in the non-engaging configuration.

[0015] In some aspects of these teachings, the actuator is operative on the magnetic latch throughout the magnetic latch's range of motion. In some of these teachings, that operability is a result of the magnetic latch and the actuator being configured such that their relative motion is limited to a relatively narrow range. In some of these teachings, the magnetic latch may be configured near a pivot point for the rocker arm to which the magnetic latch is mounted. In some of these teachings, the rocker arm pivots on a fulcrum, the poppet valve is to one side of the fulcrum, and the actuator is to the opposite side of the fulcrum. The fulcrum may be a hydraulic lash adjuster. In some of these teachings, one of the first and second latch pin positions is maintained by a spring. The actuator may be operative to generate a magnetic field of sufficient strength to overcome the spring force and maintain the other of the first and second latch pin positions as the magnetic latch travels through its range of motion.

[0016] According to some aspects of the present teachings, the operability of the actuator throughout the magnetic latch's range of motion is maintained by one or more sliding joints in a magnetic circuit through which the actuator affects the magnetic latch. The magnetic circuit may include the latch pin. In some of these teachings, the latch pin can move in conjunction with rocker arm motion without breaking the magnetic circuit. The actuator and the magnetic latch may include one or more pole pieces that form the sliding magnetic joint. One part of the sliding magnetic joint may be attached to the actuator while the other part of the sliding magnetic joint may be attached to the magnetic latch. In some of these teachings, the magnetic circuit is operative as a primary path for magnetic flux from the solenoid. In some of these teachings, the magnetic circuit is operative as a primary path for magnetic flux from a permanent magnet that stabilizes the latch pin in an engaging or non-engaging configuration. In some of these teachings, the sliding magnetic joint completes magnetic circuits through which one or more permanent magnets stabilize the latch pin in both its engaging and non-engaging configurations.

[0017] In some of these teachings, the magnetic latch has a first low coercivity ferromagnetic component that moves with the rocker arm, the actuator has a second low coercivity ferromagnetic component, and one of the first and second components has a surface extending along the direction in which the first component moves. This structure may form a sliding magnetic joint and allow the first and second components to remain proximate as the rocker arm travels through its range of motion. In some of these teachings, both component have surfaces extending along the direction of relative motion. Providing both components with surfaces extending along the direction of relative motion may maintain proximity between the two components and provide a large area through which magnetic flux may easily pass between them.

[0018] In some of these teachings, the magnetic latch has a low coercivity

ferromagnetic component an outer portion of which travels an arc as the rocker arm moves through its range of motion and the actuator has a low coercivity ferromagnetic component with a surface parallel to the arc and positioned to remain in proximity to the arc throughout the rocker arm's range of motion. The two components may form a sliding joint for a magnetic circuit.

[0019] In some of these teachings, a magnetic circuit that is operative as a primary path for magnetic flux from the solenoid or a permanent magnet includes an air gap spanning between the magnetic latch and the actuator. The latch and the actuator may be configured whereby the width of the air gap does not vary by more than 50% over the first rocker arm range of motion. A magnetic circuit may include two air gaps spanning between the magnetic latch and the actuator. Magnetic flux traveling from the magnetic latch to the actuator may cross the first air gap and magnetic flux from the actuator to the magnetic latch may cross the second air gap. In some of these teachings, variation in the widths of both air gaps are limited during rocker arm motion by sliding magnetic joints.

[0020] According to some aspect of the present teachings, a magnetic latch mounted to a rocker arm includes a latch pin a portion of which is formed of a low coercivity ferromagnetic material and protrudes from the rocker arm in the direction of the actuator. Energizing the solenoid may be operative to actuate the latch pin in such a way that a variable air gap between the protruding portion of the latch pin and the actuator is reduced. In some of these teachings, pole pieces from the actuator extend proximate the latch pin, whereby magnetic flux from the solenoid follows a magnetic circuit that passes directly from the pole pieces to the latch pin before returning to the actuator across the variable air gap. In some alternate teachings, the pole pieces extend proximate pole pieces forming part of the magnetic latch; pole pieces of the magnetic latch extend proximate the latch pin; and the magnetic flux from the solenoid follows a magnetic circuit from the pole pieces of the actuator to the pole pieces of the magnetic latch and from there into the latch pin before returning to the actuator across the variable air gap.

[0021] According to some aspects of the present teachings, the magnetic latch is mounted to a first rocker arm and a second rocker arm passes between the first rocker arm and the actuator over the course of the second rocker arm's range of motion.

Nevertheless, a magnetic circuit may be formed between the actuator and a latch pin of the magnetic latch. Moreover, in some of these teachings, a magnetic circuit may be maintained and stabilize the latch pin position throughout the second rocker arm's range of motion. In some of these teachings, pole pieces are mounted to the second rocker arm that complete a magnetic circuit that includes the magnetic latch and the actuator. In some of these teachings, pole pieces mounted to either the actuator or the first rocker arm pass around the second rocker arm to complete a magnetic circuit that includes the magnetic latch and the actuator.

[0022] The effectiveness of the actuator depends on its positioning relative to the magnetic latch. The effect of variations in that positioning due to manufacturing tolerances may be ameliorated by one or more sliding magnetic joints. According to some aspects of the present teachings, the actuator comprises one or more members extending from the actuator to engage the sides of the rocker arm assembly. These members may facilitate the positioning of the actuator relative to the latch pin. In some of these teachings, the members engage the rocker arm assembly without attaching to the rocker arm assembly. In some of these teachings, the members engage a fulcrum of the rocker arm assembly.

[0023] Some of the present teachings relate to methods of operating an internal combustion engine. In some of these teachings, the engine includes a valvetrain in which a rocker arm assembly has a magnetic latch mounted to a rocker arm. The latch provides the rocker arm assembly with engaging and non-engaging configurations. According to some aspects of the present teachings, a method of operating the engine includes operating the engine with the magnetic latch in one of the engaging and non- engaging configurations. A solenoid of an actuator that is mounted off the rocker arm is energized to cause the magnetic latch to change its configuration. The engine is then further operated with the magnetic latch in the other of the engaging and non-engaging configurations. In some of these teachings, energizing the solenoid is limited to a predetermined portion of the cam cycle. The predetermined portion of the cam's cycle may correspond to the time that the cam is on base circle. In some of these teachings, the solenoid generates a magnetic field that crosses an air gap between the actuator and the latch to act on the latch.

[0024] Some of these teachings relate to the case in which the magnetic latch is stable in both engaging and non-engaging configuration. According to some aspects of the present teachings, a method of operating the engine includes operating the engine while using a permanent magnet to maintain a magnetic latch mounted to a rocker arm in an engaging configuration. A solenoid of an actuator that is mounted off the rocker arm is energized to redirect the magnetic flux from the magnet and cause the magnetic latch to switch to a non-engaging configuration. The engine is then further operated with the permanent magnet maintaining the magnetic latch in the non-engaging configuration. The solenoid may then be energized again, this time with a current in the reverse direction, to again redirect the magnetic flux from the magnet and cause the magnetic latch to switch back to the engaging configuration

[0025] The teachings of the present disclosure have been described primarily in terms of a magnetic latch mounted to a rocker arm and an actuator mounted off the rocker arm. However, some of the present teachings are applicable to valvetrains in which the magnetic latch is mounted to another part of the rocker arm assembly and the actuator is mounted off that part. In some of these teachings, the magnetic latch is mounted to a part that is mobile relative to the cylinder head and the actuator is mounted to a part that is stationary relative to the cylinder head. In some of these teachings, the magnetic latch is mounted to a mobile portion of a hydraulic lash adjuster or to a lifter. The actuator may be mounted to the cylinder head itself.

[0026] 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.

Brief Description of the Drawings

[0027] Fig. 1 is a top partial cutaway view of an internal combustion engine according to some aspects of the present teachings.

[0028] Fig. 2 illustrates a cross-section along the line 2-2 of Fig. 1 .

[0029] Fig. 3 is a cross-sectional side view of the internal combustion engine of Fig. 1 taken along the line 1 -1 of Fig. 1

[0030] Fig. 4 is the same view as Fig. 3, but with the latch pin moved from a non- engaging to an engaging configuration.

[0031] Fig. 5 is the same view as Fig. 2, but with the cam risen off base circle.

[0032] Fig. 6 is the same view as Fig. 4, but with the cam risen off base circle.

[0033] Fig. 7 illustrates a partial cross-section of an internal combustion engine according to some other aspects of the present teachings.

[0034] Fig. 8 illustrates the same cross-section as Fig. 7, but with the latch pin moved from a non-engaging to an engaging configuration.

[0035] Fig. 9 illustrates a cross-section along the line 4-4 of Fig. 8.

[0036] Fig. 10 illustrates a cross-section along the line 5-5 of Fig. 8.

[0037] Fig. 1 1 illustrates a cross-section along the line 6-6 of Fig. 8.

[0038] Fig. 12 illustrates a cross-section along the line 4-4 of Fig. 8 as it would appear after the cam has risen off base circle.

[0039] Fig. 13 illustrates a cross-section along the line 5-5 of Fig. 8 as it would appear after the cam has risen off base circle.

[0040] Fig. 14 illustrates a cross-section along the line 6-6 of Fig. 8 as it would appear after the cam has risen off base circle. [0041] Fig. 15 illustrates a partial cross-section of an internal combustion engine according to some other aspects of the present teachings.

[0042] Fig. 16 illustrates the same cross-section as Fig. 15, but with the latch pin moved from a non-engaging to an engaging configuration.

[0043] Fig. 17 illustrates a cross-section along the line 7- ^■ 7 of Fig. 16.

[0044] Fig. 18 illustrates a cross-section along the line 8- ^■ 8 of Fig. 16.

[0045] Fig. 19 illustrates a cross-section along the line Si- ^■ 9 of Fig. 16.

[0046] Fig. 20 illustrates a cross-section along the line 7- ^■ 7 of Fig. 16 as it would appear after the cam has risen off base circle.

[0047] Fig. 21 illustrates a cross-section along the line 8-8 of Fig. 16 as it would appear after the cam has risen off base circle.

[0048] Fig. 22 illustrates a cross-section along the line 9-9 of Fig. 16 as it would appear after the cam has risen off base circle.

[0049] Fig. 23 illustrates a cross-section of an internal combustion engine according to some other aspects of the present teachings.

[0050] Fig. 24 illustrates the same cross-section as Fig. 23, but with the latch pin moved from a non-engaging to an engaging configuration.

[0051] Fig. 25 illustrates a partial cross-section of an internal combustion engine according to some other aspects of the present teachings.

[0052] Fig. 26 illustrates a cross-section along the line 10-10 of Fig. 25.

[0053] Fig. 27 illustrates the same cross-section as Fig. 25, but with the latch pin moved from a non-engaging to an engaging configuration.

[0054] Fig. 28 illustrates a cross-section along the line 1 1 -1 1 of Fig. 27.

[0055] Fig. 29 illustrates a cross-section along the line 1 1 -1 1 of Fig. 27.

[0056] Fig. 30 illustrates a cross-section along the line 12-12 of Fig. 27.

[0057] Fig. 31 illustrates a cross-section along the line 13-13 of Fig. 27 as it would appear after the cam has risen off base circle.

[0058] Fig. 32 is a flow chart of a method of operating an internal combustion engine according to some aspects of the present disclosure. [0059] Fig. 33 is a flow chart of a method of operating an internal combustion engine according to some other aspects of the present disclosure.

[0060] Fig. 34 is a top partial cutaway view of an internal combustion engine according to some other aspects of the present teachings

[0061] Fig. 35 provides a side view illustrating the relative positioning of the parts shown in region 400 of Fig. 34.

[0062] Fig. 36 provides a side view illustrating the relative positioning of the parts shown in Fig. 35 after the cams rise off base circle with the latch in a non-engaging position.

[0063] Fig. 36 provides a side view illustrating the relative positioning of the parts shown in Fig. 35 after the cams rise off base circle with the latch in an engaging position.

Detailed Description

[0064] In the drawings, some reference characters consist of a number followed by a letter. In this description and the claims that follow, a reference character consisting of that same number without a letter is equivalent to a listing of all reference characters used in the drawings and consisting of that same number followed by a letter. For example, "permanent magnet 200" is the same as "permanent magnet 200A, 200B, 200C".

[0065] Fig. 1 provides a partial-cutaway top view of a portion of an engine 100A in accordance with some aspects of the present teachings. The view of Fig. 1 includes a rocker arm assembly 1 15A and an actuator 127A. Fig. 2 illustrates a cross-section through the actuator 127A taken along the line 2-2 of Fig. 1 . Fig. 3 illustrates a cross- sectional side view of engine 100A taken along the line 1 -1 of Fig. 1 . The view of Fig. 3 includes some parts of engine 100A in addition to those shown in Fig. 1 . Those additional parts include a poppet valve 185, a cam shaft 169 on which is mounted a cam 167, a hydraulic lash adjuster 181 , and more of the cylinder head 130.

[0066] Rocker arm assembly 1 15A includes rocker arm 103A (an outer arm), rocker arm 103B (an inner arm), and a hydraulic lash adjuster (HLA) 181 . A cam follower 107 may be mounted to rocker arm 103B through bearings 165 and shaft 147. Cam follower 107 is a roller follower. Alternatively, cam follower 107 may be a slider. A magnetic latch 1 17A is mounted to rocker arm 103A. Latch 1 17A includes a latch pin 1 14A, a spacer 139A, and a spring 141 . Latch pin 1 14A includes latch pin body 1 13A, latch head 1 1 1 . A portion 135 of latch pin 1 14A protrudes outward from rocker arm 103A in the direction of actuator 127. The protruding portion 135 may be integral with latch pin body 1 13A. At least a part of portion 135 is formed of low coercivity ferromagnetic material.

[0067] Latch pin 1 14A is translatable between a first position and a second position. The first position may be a non-engaging position, which is illustrated in Fig. 3. The second position may be an engaging position, which is illustrated in Fig. 4. When latch pin 1 14A is in the engaging position, rocker arm assembly 1 15A may be described as being in an engaging configuration. When latch pin 1 14A is in the non-engaging position, rocker arm assembly 1 15A may be described as being in a non-engaging configuration.

[0068] Both rocker arms 103A and 103B may pivot on a shaft 149. Openings 182 may be formed into the sides of rocker arm 103A to allow it to pivot on shaft 149 independently from rocker arm 103B without interference from shaft 147, which is mounted to rocker arm 103B and extends outwardly to engage torsion spring 145.

Torsion spring 145 acts on shaft 147 to bias rocker arm 103B upward relative to rocker arm 103A and maintain engagement between cam follower 107 and cam 167. Torsion spring 145 may be mounted to rocker arm 103A on trunnions 143.

[0069] Fig. 6 shows the effect if cam 167 rises off of base circle with while latch pin 1 14A is in the engaging position. Latch head 1 1 1 may engage lip 109 of rocker arm 103B, after which rocker arm 103B and rocker arm 103A may be constrained to move in concert. HLA 181 may operate as a fulcrum on which rocker arm 103B and rocker arm 103A may pivot together, driving down on valve 185 via an elephant's foot 151 , compressing valve spring 183 against cylinder head 130, and lifting valve 185 of its seat lifted of its seat 186 within cylinder head 130 with a valve lift profile determined by the shape of cam 167. The valve lift profile is the shape of a plot showing the height by which valve 185 is lifted of its seat 186 as a function of angular position of cam shaft 169.

[0070] Fig. 5 shows the effect if cam 167 rises off of base circle while latch pin 1 14A is in the non-engaging position. Cam 167 still drives rocker arm 103B downward. But in the non-engaging configuration, rocker arm 103A may remain stationary. Torsion springs 145 may yield before valve spring 183, whereby rocker arm 103B merely pivots on shaft 149 without lifting valve 185 of its seat 186. This configuration may provide deactivation of a cylinder with a port controlled by valve 185. Alternatively, there may be additional cams that operate directly on rocker arm 103A independently from rocker arm 103B. These additional cams may provide a lower valve lift profile than cam 167. Therefore, the non-engaging configuration for rocker arm assembly 1 15A may provide an alternate valve lift profile and rocker arm assembly 1 15A may provide a switching rocker arm.

[0071] Actuator 127A may be mounted to cylinder head 130. Actuator 127A may be mounted using a bracket 129, for example. Alternatively, actuator 127A could be mounted to another part on engine 100 that is stationary relative to cylinder head 130. A cam carrier and a valve cover are examples of parts that engine 100 may include that would be stationary relative to cylinder head 130. Actuator 127A is mounted off rocker arm assembly 1 15A. Alternatively, actuator 127A could be mounted to an outer sleeve 173 of HLA 181 . Outer sleeve 173 of HLA 181 may remain stationary relative to cylinder head 130. Even if actuator 127A is mounted off rocker arm assembly 1 15A, it may still include alignment guides (not shown) that extend to engage the sides of HLA 181 or another part of rocker arm assembly 1 15A. Such guides may facilitate alignment of actuator 127A with latch 1 17A.

[0072] Actuator 127A may include a solenoid 1 19, pole pieces 131 A, 131 B, 131 C, and 131 D, a spacer 133, and a shell 121 . Pole pieces 131 may be formed of low coercivity ferromagnetic material. Pole piece 131 A may provide be a core centrally located within solenoid 1 19. Shell 121 may protect solenoid 1 19 from its surrounding environment and facilitate mounting of actuator 127A. Spacer 133 may facilitate proper spacing in magnetic circuits formed with pole pieces 131 . Accordingly, spacer 133 may be made of a steel that is not ferromagnetic.

[0073] A spring 141 may bias latch pin 1 14A toward and hold latch pin 1 14A in the engaging position. If solenoid 1 19 is energized while cam 167 is at or near base circle, the majority of magnetic flux from solenoid 1 19 may follow a magnetic circuit 220E illustrated in Figs. 3 and 4. Magnetic circuit 220E includes pole pieces 131A-D, and low coercivity ferromagnetic portion 135 of latch pin 1 14A. Depending on the positon of latch pin 1 14A, magnetic circuit 220E may include an air gap 134 spanning between latch pin 1 14A and pole piece 131 A. Air gap 134 may be reduced by translation of latch pin 1 14A toward the non-engaging position. Reducing the size of air gap 134 reduces the magnetic reluctance of magnetic circuit 220E. Accordingly, the magnetic forces will tend to reduce the size of air gap 134 and energizing solenoid 1 19 may be operative to overcome the force of spring 141 , translate latch pin 1 14A to its non-engaging position, and hold it there.

[0074] Latch 1 17A, by virtue of being mounted to rocker arm 103A, has a range of motion relative to cylinder head 130 and actuator 127A. This range of motion may be primarily the result of rocker arm 103A pivoting on HLA 181 when rocker arm assembly 1 15A is in the engaging configuration. But if latch 1 17A is in the non-engaging configuration, the position of latch 1 17A relative to actuator 127A may be substantially fixed. Extension and retraction of HLA 181 may introduce some relative motion. But excluding a brief period during start-up, the range of motion introduced by HLA 181 may be negligible. As long as latch pin 1 14A as in the non-engaging configuration, magnetic circuit 220E may remain intact whereby solenoid 1 19 may act through that circuit to maintain latch pin 1 14A in the non-engaging configuration

[0075] In accordance with some aspects of the present teachings, pole piece 131 D may be configured to be proximate latch pin protrusion 135 on multiple sides, including two opposite sides, when cam 167 is on base circle. Such a configuration is shown in Fig. 2 and may provide a large area through which magnetic flux may easily pass between latch pin 1 14A and pole pieces 131 . As shown in Fig. 6, latch pin protrusion 135 may rise relative to actuator 127A as cam 167 lifts off base circle with rocker arm assembly 1 15A in the engaging configuration. In some of these teachings, pole piece 131 D has a slot 159 to accommodate this upward motion. In some examples, HLA 181 may descend and cause latch pin protrusion 135 to drop substantially when engine 100A is shut down. In some of these teachings, another slot (not shown) may be formed in pole piece 131 D to accommodate this motion as well.

[0076] Figs. 7 and 8 illustrate cross-sections of a portion of an engine 100B, which may be the same as the engine 100A except for the illustrated differences. Engine 100B provides another example in accordance with some aspects of the present teachings. Engine 100B includes rocker arm assembly 1 15B and actuator 127B. The view of Figs. 7 and 8 includes a portion of rocker arm assembly 1 15B and of actuator 127B. Fig. 7 illustrates rocker arm assembly 1 15B in a non-engaging configuration and Fig. 8 illustrates rocker arm assembly 1 15B in an engaging configuration.

[0077] Latch 1 17B includes latch pin 1 14B and pole piece 192A. Actuator 127B includes solenoid 1 19 and pole pieces 131 A, 131 B, and 131 E. A pole piece, as the term is used in the present disclosure, may be any part formed with low coercivity ferromagnetic material. Figs. 9, 10, and 1 1 illustrate cross-sections through the actuator 127B taken along the lines 4-4, 5-5, and 6-6 of Fig. 8, respectively. Figs. 12-14 illustrate corresponding cross-sections, but with changes resulting for cam 167 rising off base circle with rocker arm assembly 1 15B in the engaging configuration.

[0078] Pole piece 131 A may be a core for solenoid 1 19. Pole piece 131 B may be a disc covering an end of solenoid 1 19 that is distal from latch 1 17B. There may be two pole pieces 131 E. Each pole pieces 131 E may have the form of a half cylinder where they lie adjacent solenoid 192. Solenoid 1 19 may be cylindrical and the two pole pole pieces 131 E may together form a cylindrical shell around solenoid 1 19. Solenoid 1 19 may have any suitable shape. In some of the present teachings, pole pieces 131 fit closely around solenoid 1 19 to enhance its efficiency.

[0079] In accordance with some aspects of the present teachings, and as can be seen by comparing the cross-sections illustrated by Figs. 9-14, pole pieces 131 E of actuator 127B change their profile shape as they extend towards rocker arm assembly 1 15B. In some of these teachings, they flatten toward planar shapes. The planar shapes may be realized in the region where pole pieces 131 E are adjacent pole piece 192A. As shown in Figs. 9-14, the flattening of pole pieces 131 E to a planar shape allows latch 1 17B including pole piece 192A to move with the rocker arm 103A without interfering with pole pieces 131 E. While in this example, pole piece 192A remains cylindrical in cross-section as it extends adjacent pole pieces 131 E, in some aspects of the present teachings, which are illustrated with other examples, pole piece 192A are split and flatten into planar shapes like pole pieces 131 E. Such flattening may be used to provide a large areas through which magnetic flux may easily pass between pole pieces 131 of actuator 127 and pole pieces 192 of magnetic latch 1 17.

[0080] In engine 100B, if solenoid 1 19 is energized it may generate magnetic flux that follows magnetic circuit 220F shown in Fig. 8. Magnetic circuit 220F may include pole pieces 131 A, 131 B, and 131 E of actuator 127B, pole piece 192A of latch 1 17B, latch pin 1 14B, and an air gap 134. The operation of actuator 127B may be similar to that of actuator 127A. One difference is that the magnetic circuit 220F formed by actuator 127B and magnetic latch 1 15B transfers flux from the outer pole pieces 131 E to latch pin 1 14B through pole pieces 192A. The structures of magnetic circuits 220E and 220F each have potential advantages in terms of efficiency and packaging.

[0081] Fig. 15 illustrates a cross-section of a portion of an engine 100C in

accordance with some other aspects of the present teachings. Engine 100C includes rocker arm assembly 1 15C and an actuator 127C. Rocker arm 1 15C includes a rocker arm 103A to which is mounted a magnetic latch 1 17C having a latch pin 1 14C. Actuator 127C may remain in a fixed position with respect to cylinder head 130 while being operative on latch 1 17C throughout the range of motion of rocker arm 103A. Engine 100C includes circuitry (not shown) through which a voltage with either a forward polarity or a reverse polarity may be applied to solenoid 1 19 of actuator 127C. Actuator 127C is operative both to actuate latch pin 1 14C of latch 1 17C from either an engaging position, shown in Fig. 16, to a non-engaging position, shown in Fig. 15, and from the non-engaging position to the engaging position. Figs. 17, 18, and 19 illustrate cross- sections through the actuator 127C taken along the lines 7-7, 8-8, and 9-9 of Fig. 16, respectively. Figs. 20-22 illustrate corresponding cross-sections, but with changes resulting for cam 167 rising off base circle with rocker arm assembly 1 15C in the engaging configuration.

[0082] Magnetic latch 1 17C includes a first permanent magnet 200A, a second permanent magnet 200B, and pole pieces 192C, 192D, 192E, and 192F. Latch pin 1 14C may include a latch pin body 1 13C to which a low coercivity ferromagnetic portion 209 of latch pin 1 14C is mounted. Actuator 127C includes solenoid 1 19 and pole pieces 131 F, 131 B, and 131 E. As illustrated in Figs. 15 and 16, magnetic latch 1 17C forms magnetic circuits 220A and 220D. Magnetic latch 1 17C and actuator 127C together form magnetic circuits 220B and 220C.

[0083] In accordance with some aspect of the present teachings, the pole pieces of actuator 127C and of latch 1 17C form nearly planar surfaces in areas where they approach each other to complete magnetic circuits. As illustrated by the cross-sections of Figs. 17-22, pole piece 192C and 192B flatten toward a planar shape as they extend near pole pieces 131 . Likewise, pole pieces 131 E flatten toward a planar shape as they extend toward where they lie adjacent pole pieces 192. Pole piece131 F may be cylindrical where it forms a core for solenoid 1 19, but its surfaces flatten to form a rectangular cross-section as it extends to lie adjacent pole pieces 192B.

[0084] Actuator 127C may be operative to assist latch 1 17C in maintaining the position of latch pin 1 14C throughout the range of motion of rocker arm assembly 1 15C even if latch pin 1 14C is in the engaging position where relative motion between actuator 127C and latch 1 15C is highest. Even when solenoid 1 19 is not energized, actuator 127C may be operative on latch 1 15C by complete magnetic circuits 220 through which permanent magnets 200A and 200B stabilize the position of latch pin 1 14C.

[0085] In accordance with some aspects of the present teachings, latch pin 1 14C is stable in either the first position, which provides a non-engaging configuration for rocker arm assembly 1 15C shown in Fig. 15, or in the second position, which provides an engaging configuration for rocker arm assembly 1 15C shown in Fig. 16. The stability referred to here is a positional stability. A stable position may correspond to a local minima in a potential energy that is variable over a bounded range. A position may be stabilized by restorative forces that are generated without external power. Restorative forces will tend to return latch pin 1 14C to its stable position if latch pin 1 14C is displaced from that position by a small perturbation. Restorative forces may be provided by springs, permanent magnets, or a combination thereof. In engine 100C, restorative forces are provided by permanent magnets 200A and 200B.

[0086] Both permanent magnets 200A and 200B stabilize the position of latch pin 1 14C in both the engaging and the non-engaging configurations. When latch pin 1 14C is in the non-engaging configuration, absent magnetic fields from solenoid 1 19 or any external source, magnetic circuit 220A provides the primary path for magnetic flux from permanent magnet 200A. The primary path for magnetic flux from a magnet is a path taken by the majority of flux from that magnet. Magnetic circuit 220A passes from the north pole of permanent magnet 220A, through pole piece 192D, through low coercivity ferromagnetic portion 209 of latch pin 1 14C, through pole pieces 131 A, 131 B, and 131 C of actuator 127C, through pole pieces 192B and 192C of magnetic latch 1 15C, to the south pole of permanent magnet 220A. Magnetic circuit 220C provides the primary path for magnetic flux from permanent magnet 200B. Magnetic circuit 220C passes from the north pole of permanent magnet 220B, through pole piece 192D, through low coercivity ferromagnetic portion 209 of latch pin 1 14C, through pole piece 192D, to the south pole of permanent magnet 220B. Magnetic circuit 220C is shorter than magnetic circuit 220A and does not pass through actuator 127C.

[0087] If solenoid 1 19 is energized with current in a forward direction while latch pin 1 14C is in the non-engaging configuration, the resulting magnetic field may reverse magnetic polarity in the low coercivity ferromagnetic materials throughout magnetic circuit 220A. This greatly increase the reluctance of magnetic circuit 220A for flux from permanent magnet 200A. Magnetic circuit 220C may also be affected. Magnetic flux from permanent magnets 200A and 200B may be shifted away from magnetic circuits 220A and 220C and the net magnetic forces on latch pin 1 14C may drive it toward the engaging configuration shown in Fig. 16.

[0088] Latch pin 1 14C may reach the engaging configuration and remain there after solenoid 1 19 has been disconnected from its power source. When latch pin 1 14C is in the engaging configuration, absent magnetic fields from solenoid 1 19 or any external source, magnetic circuit 220D provides the primary path for magnetic flux from permanent magnet 200B. Magnetic circuit 220D passes from the north pole of permanent magnet 220B, through pole piece 192D, through low coercivity

ferromagnetic portion 209 of latch pin 1 14C, through pole pieces 192B and 192C of magnetic latch 1 15C, through pole pieces 131 A, 131 B, and 131 C of actuator 127C, through pole piece 192E to the south pole of permanent magnet 220A. In the engaging configuration, magnetic circuit 220B provides the primary path for magnetic flux from permanent magnet 200A. Magnetic circuit 220B passes from the north pole of permanent magnet 220A, through pole piece 192D, through low coercivity

ferromagnetic portion 209 of latch pin 1 14C, through pole pieces 192F and 192G, to the south pole of permanent magnet 220A. Magnetic circuit 220B is shorter than magnetic circuit 220D and does not pass through actuator 127C.

[0089] In accordance with some aspects of the present teachings, permanent magnets 200A and 200B are fixedly mounted to rocker arm 103A and arranged with confronting polarity. A pole piece 192D is positioned between the confronting poles. Permanent magnets 200A and 200B and pole piece 192D may be annular in shape and mounted to be concentric with respect to latch pin 1 14C. While this provides a compact and efficient design, other shapes and configurations may be substituted.

[0090] Low coercivity ferromagnetic portion 209 of latch pin 1 14C may have a stepped edge. Pole pieces 192 of latch 1 15C may be shaped to mate with that edge. During actuation, magnetic flux may cross an air gap between latch pin 1 14C and pole pieces 192. The stepped edge may increase the magnetic forces through which latch pin 1 14C is actuate from the second position to the first.

[0091] As illustrated in Figs. 17-23, pole pieces 192C and 131 E form a sliding magnetic joint. The distance between pole pieces 192C and 131 E varies by less than 50% as rocker arm 103A travels through its range of motion with latch pin 1 14C in the engaging position. As rocker arm 103A moves, pole piece 192C moves in a

substantially vertical direction. Pole piece 192C has a surface extending in this direction of motion, whereby it may maintain its proximity to pole piece 131 E throughout the range of motion. This surface is also parallel to an arc travelled by the outer surface of pole piece 192C. Parallel to an arc means parallel to a tangent of that arc.

[0092] As the used in the present disclosure, a sliding joint in a magnetic circuit may refer to an air gap between two parts in the circuit where the air gap does not change significantly in size as the two parts move relative to one another. A variation that remains less than 50% is usually not significant. In some of these teachings, one of the parts forming the sliding joint has a surface adjacent the air gap that is substantially parallel to a direction along which one of the parts is free to move relative to the other.

[0093] Pole pieces 192B and 131 F form another sliding magnetic joint. The distance between pole pieces 192B and 131 F varies by less than 50% as rocker arm 103A travels through its range of motion with latch pin 1 14C in the engaging position. As rocker arm 103A moves, pole piece 192B moves in a substantially vertical direction. Pole piece 192B has a surface extending in this direction of motion, whereby it may maintain its proximity to pole piece 131 F throughout the range of motion. Pole piece 131 F also has a surface extending in this direction of motion, which could also be sufficient to maintain this proximity through the travel of pole piece 192B. Providing each pole piece with a surface extending in the direction of motion allows the two surface to remain proximate and provide a large area for magnetic flux transfer throughout the range of motion. Since magnetic flux must complete a circuit, in some of the present teachings actuator 127 and latch 1 17 form at least two sliding magnetic joints.

[0094] Figs. 23 and 24 illustrates an engine 100D, which provides an example in which a permanent magnet 200C that is part of an actuator 127D mounted off rocker arm 103A is operative to stabilize the position of a latch pin 1 14D of a latch 1 17D that is mounted on rocker arm 103A. Latch pin 1 14D has both engaging and non-engaging positions in which its position is stable.

[0095] When latch pin 1 14D is in the non-engaging position, latch pin 1 14D is held there by permanent magnet 200C with magnetic circuit 220G providing the primary path for permanent magnet 200C's magnetic flux. Magnetic circuit 220G passes from the north pole of magnet 200C through pole pieces 131 B, 131 C of actuator 127D, through pole piece 192C of magnetic latch 1 15D, through latch pin 1 14D, through pole pieces 131 A and 131 F of actuator 137D to the south pole of magnet 200C. Magnetic circuit 220G may be maintained throughout the range of motion of rocker arm 103A by sliding magnetic joints, although in this example that is not necessary as rocker arm 103A remains stationary while latch pin 1 14D is in the non-engaging position.

[0096] If solenoid 1 19 is energized with current in a suitable first direction while latch pin 1 14D is in the non-engaging position, polarities in magnetic circuit 220G may be reversed. Flux from permanent magnet 200C may be redirected to a magnetic circuit 220H, which is illustrated in Fig. 24. Magnetic circuit 220H passes from the north pole of magnet 200C through pole pieces 131 B, 131 C and 131 F of actuator 127D, to the south pole of magnet 200C. Magnetic circuit 220H does not pass through latch pin 1 14D. Energizing solenoid 1 19 with current in the first direction disrupts the magnetic attraction between latch pin 1 14D and pole piece 192A allowing spring 141 to drive latch pin 1 14D to the engaging position and hold it there.

[0097] When latch pin 1 14D moves to the engaging configuration, it introduces an air gap 134 into magnetic circuit 220G. Air gap 134 greatly increases the magnetic reluctance of magnetic circuit 220G. Therefore, there may be little or no tendency for magnetic flux from permanent magnet 200C to shift back to magnetic circuit 220G until solenoid 1 19 is energized with current in a reverse of the first direction. When solenoid 1 19 is so energized, polarities in magnetic circuit 220G may be re-established in a direction that attracts flux from permanent magnet 200C. Permanent magnet 200C and solenoid 1 19 may then cooperate to magnetically actuate latch pin 1 14D back to the non-engaging configuration where latch pin 1 14D may be stably maintained by permanent magnet 200C alone.

[0098] Actuation in both latches 1 17C and 1 17D may occur through a flux shifting mechanism. A flux-shifting mechanism involves redirecting the flux from a permanent magnetic from a first magnetic circuit to a second distinct magnetic circuit. In some of these teachings, the first and second circuits share a structural element formed of a low coercivity ferromagnetic material. A first magnetic polarity in that structural element favors the magnetic flux traveling the first circuit and a second polarity favors the magnetic flux traveling the second circuit. The availability of the second magnetic circuit may reduce the energy required to actuate a latch pin away from a position that is held by a permanent magnet with its flux following the first magnetic circuit.

[0099] Solenoid 1 19 may be considered an electromagnet. In the examples above, a solenoid 1 19 was positioned with a pole facing the rocker arm assembly 1 15, including latch pin 1 14. Figs. 25-31 illustrates an internal combustion engine 100E including a rocker arm assembly 106E and an actuator 127E. Engine 100E provides an example in which a solenoid 1 19 is positioned with its poles off axis from a latch pin 1 14E. This configuration may facilitate packaging of actuator 127E under a valve cover. Fig. 25 shows the non-engaging configuration. Fig. 27 shows the engaging

configuration. Fig. 26 illustrates a cross-section of actuator 127E taken through line 10- 10 of Fig. 25. Figs. 28 and 29 illustrates cross-sections of latch 127E taken through lines 1 1 -1 1 and 12-12 of Fig. 27. Fig. 30 illustrates the cross-section taken through line 13-13 of Fig. 27. Fig. 31 illustrates this cross-section after cam 167 has risen off base circle.

[0100] Both permanent magnets 200A and 200B may stabilize latch pin 1 14E in the engaging configuration. In the engaging configuration, most of the flux from permanent magnet 200A follows magnetic circuit 220I and most of the flux from permanent magnet 200B follows magnetic circuit 220K. Magnetic circuit 220I proceeds from the north pole of permanent magnet 200A, through pole piece 192J, through low coercivity

ferromagnetic portion 209 of latch pin 1 14E, through pole pieces 192E and 1921, and ends at the south pole of permanent magnet 200A. Magnetic circuit 2201 may be a short magnetic circuit contained entirely within magnetic latch 1 17E. Magnetic circuit 220K proceeds from the north pole of permanent magnet 200B, through pole piece 192D, through low coercivity ferromagnetic portion 209 of latch pin 1 14E, through a pole pieces 192E, 192I, and 192J of magnetic latch 1 17E, across a narrow air gap and onward through pole piece 131 1, 131 A, and 131 H of actuator 127E, across another narrow air gap to pole piece 192G of magnetic latch 1 17E, and then through pole piece 192H to the south pole of permanent magnet 200B. Magnetic circuit 220I forms two sliding magnetic joints. Pole pieces 131 H and 131 1 of actuator 127E may be planar in shape. Pole pieces 192G and 192J of magnetic latch 1 17E may be quarter cylinders. Pole piece 192H and 1921 may be planar. Pole piece 192H may close off a space within magnetic latch 1 17E. Pole piece 1921 may have an opening through which latch pin 1 14E translates.

[0101] Energizing solenoid 1 19 with a current in a suitable direction may redirect the flux from permanent magnets 200A and 200B and cause latch pin 1 14E to translate to a non-engaging position. As shown in Fig. 23 in the non-engaging configuration, after solenoid 1 19 has been disconnected from its power source, both permanent magnets 200A and 200B may again stabilize the position of latch pin 1 14E. In the non-engaging configuration, most of the flux from permanent magnet 200A follows magnetic circuit 220J and most of the flux from permanent magnet 200B follows magnetic circuit 220L. Magnetic circuit 220J proceeds from the north pole of permanent magnet 200A, through pole piece 192D, through low coercivity ferromagnetic portion 209 of latch pin 1 14E, through pole pieces 192H and 192Gof magnetic latch 1 17E, across a narrow air gap to131 H and then through pole piece 131 A and 131 1 of actuator 127E, across another narrow air gap to pole piece 192J of magnetic latch 1 17E, and then through pole piece 1921 to the south pole of permanent magnet 200A. Magnetic circuit 220L proceeds from the north pole of permanent magnet 200B, through pole piece 192D, through low coercivity ferromagnetic portion 209 of latch pin 1 14E, through pole pieces 192E and 1921 to the south pole of permanent magnet 200B. The process of actuating latch pin 1 14E to the non-engaging position may be reversed by applying a reversed polarity voltage to solenoid 1 19.

[0102] Fig. 32 is flow chart of a method 300 providing an example in accordance with some aspects of the present teaching. Method 300 begins with act 301 , which is energizing a solenoid 1 19 to magnetically disengage a magnetic latch 1 17. The solenoid 1 19 is mounted in a position that is stationary with respect to cylinder head 130. In some of these teachings, that position is off rocker arm assembly 1 15. In some of these teaching, that position is a portion of rocker arm assembly 1 15 that does not move relative to cylinder head 130. The magnetic latch 1 17 may be on a mobile portion of a rocker arm assembly 1 15. In some of these teachings, magnetic latch 1 17 is mounted to a rocker arm 103. In some of these teachings, solenoid 1 19 generates a magnetic field that crosses from the actuator 127 to the latch to exert a magnetic force that actuates latch pin 1 14. Energizing solenoid 1 19 may include coupling solenoid 1 19 to a voltage source.

[0103] In some of the present teachings, magnetic latch 1 17 is only actuated when cam 169 is on base circle. Any suitable method may be used to control the actuation timing. In some of these teachings, a signal to actuate magnetic latch 1 17 is only generated when cam 169 is on base circle. The signal may be generated by an engine control unit (not shown), for example. In some of these teachings, once a signal to actuate magnetic latch 1 17 is received, a controller delays engaging solenoid 1 19 with an energy source until cam 169 has arrived on base circle. In some of these teachings, solenoid 1 19 is energized before cam 169 reaches base circle to preload force on latch pin 1 17 and thereby accelerate actuation once the base circle position has arrived.

[0104] Method 300 continues with act 303, using solenoid 1 19 to maintain the unlatched configuration while operating the rocker arm assembly 1 15. Operating rocker arm assembly 1 15 may comprise rotating cam shaft 169. Solenoid 1 19 may maintain the unlatched configuration by continuously generating a magnetic field that crosses from actuator 127 to latch 1 14 to exert a force that keeps latch 1 14 disengaged. In some of these teachings, the magnetic field from solenoid 1 19 maintains sufficient strength to overcomes a force from a spring 141 that continuously biases latch 1 14 toward the engaging configuration. In some of these teachings, a rocker arm 103 to which magnetic latch 1 14 is mounted moves but remains within solenoid 1 19's range during act 303. In some of these teachings, a rocker arm 103 to which magnetic latch 1 14 is remains substantially stationary during act 303.

[0105] The present disclosure provides several means by which solenoid 1 19 may maintain the latch configuration while the rocker arm assembly 1 15 is operating. In some of these teachings, rocker arm assembly 1 15 is configured to keep latch 1 14 substationally stationary while operating in the unlatched configuration. Rocker arm assemblies 1 15A-E can provide examples of such configurations. In some of these teachings, the motion of latch 1 14 relative to solenoid 1 19 may be sufficiently small that solenoid 1 19 remains operative on latch 1 14 through that motion. For example, the motion may be kept small by placing latch 1 14 near a pivot point for a rocker arm 103 on which latch 1 14 is mounted. Latches 1 14 of rocker arm assemblies 1 15A-E may be so configured. Continuous operability of solenoid 1 19 to maintain the position of latch 1 14 throughout the range of motion could be beneficial if the latches 1 14 are

reconfigured so that spring 141 maintains the unlatched configuration and solenoid 1 19 maintains the latched configuration. In some of these teachings, a sliding magnetic joint is provided to make solenoid 1 19 operative to maintain the latch configuration

throughout the range of motion of a rocker arm 1 13 to which latch 1 14 is mounted.

[0106] Fig. 33 is flow chart of a method 310 providing an example in accordance with some other aspects of the present teaching. Method 310 begins with act 31 1 , which is energizing solenoid 1 19 with a current in a first direction to magnetically disengage a magnetic latch 1 17. As for method 300, the solenoid 1 19 may be mounted in a position that is stationary with respect to cylinder head 130 while the latch 1 17 may be on a mobile portion of a rocker arm assembly 1 15. In some of these teachings, solenoid 1 19 generates a magnetic field that crosses from actuator 127 to latch 1 17 to exert a force that disengages magnetic latch 1 17. In some of these teachings, solenoid 1 19 redirects magnetic flux away from a circuit through which it maintains latch 1 17 in an engaging configuration. In some of these teachings, act 31 1 proceeds through a flux shifting mechanism.

[0107] Method 310 continues with act 313, interrupting the current flow to solenoid 1 19 and maintaining the unlatched configuration of latch 1 17 while operating rocker arm assembly 1 15. In these teaching, the unlatched configuration is maintained

independently from solenoid 1 19. In some of these teachings, latch pin 1 14 is stabilized in the unlatched configuration by permanent magnets 200, latch springs 141 , or a combination thereof. In some of these teachings, even after solenoid 1 19 has been de- energized actuator 127 continues to be operative to assist maintaining latch pin 1 14 in the unlatched configuration by providing a portion of a magnetic circuit that is the primary circuit for magnet flux from a magnet 200 that assists in maintaining the unlatched configuration. In some of these teachings, the magnetic circuit is maintained through a sliding magnetic joint while rocker arm assembly 1 15 operates.

[0108] Method 310 continues with act 315, which is energizing solenoid 1 19 with a current in a second direction, which is the reverse of the first direction, to magnetically engage magnetic latch 1 17. In some of these teachings, solenoid 1 19 generates a magnetic field that crosses from actuator 127 to latch 1 17 to exert a force that engages latch 1 17. In some of these teachings, solenoid 1 19 redirects magnetic flux away from a circuit through which it maintains latch 1 17 in a non-engaging configuration. In some of these teachings, act 315 proceeds through a flux shifting mechanism

[0109] Energizing solenoid 1 19 with a current in a first direction may include connecting a circuit (not shown) comprising solenoid 1 19 to a DC voltage source (not shown). In some of these teachings, to energize solenoid 1 19 with a current in a reverse direction, the circuit is again connected to the voltage source, but with a reverse polarity. This may be accomplished with, for example, an H-bridge. Alternatively, different voltage sources may be connecting depending on whether a forward or reverse current is desired in solenoid 1 19. In some others of these teachings, solenoid 1 19 may include a first set of coils to provide a magnetic field with a first polarity and a second, independently set of coils to provide a magnetic field with a second polarity. The two sets of coils may be electrically isolated and wound in different directions.

[0110] Method 310 continues with act 317, interrupting the current flow to solenoid 1 19 and maintaining the latched configuration of latch 1 17 while operating rocker arm assembly 1 15. In these teaching, the latched configuration is also maintained independently from solenoid 1 19. In some of these teachings, latch pin 1 14 is stabilized in the latched configuration by permanent magnets 200, latch springs 141 , or a combination thereof. In some of these teachings, even after solenoid 1 19 has been de- energized actuator 127 continues to be operative to assist maintaining latch pin 1 14 in the latched configuration by providing a portion of a magnetic circuit that is the primary circuit for magnet flux from a magnet 200 that assists in maintaining the latched configuration. In some of these teachings, the magnetic circuit is maintained through a sliding magnetic joint while rocker arm assembly 1 15 operates. [0111] Fig. 34 illustrates and engine 10OF in accordance with some further aspects of the present teachings. Engine 100F include an actuator 127F and a switching rocker arm assembly 1 15F. Switching rocker arm assembly 1 15F include an inner arm 103D, an outer arm 103C, and a magnetic latch 1 17F. Magnetic latch 1 17F and actuator 127F may be similar to magnetic latch 1 17D and actuator 127D except for the shapes of their pole pieces where they interface. Magnetic latch 1 17F includes a pole piece 192K. Actuator 127F includes a pole piece 131 J. These pole piece remain adjacent and close magnetic circuits formed by magnetic latch 1 17F and actuator 127F through the ranges of motion rocker arms 103C and 103D.

[0112] Figs. 35-37 illustrate the relative positioning of pole pieces 192K and 131 J for various states of rocker arm assembly 1 15F. Fig. 35 shows the relative positioning when neither rocker arm 103C or 103D is lifted by a cam. Fig. 36 shows the relative positioning when both rocker arm 103C or 103D are in positons of maximum lift with latch 1 17F in a non-engaging configuration. Fig. 37 shows the relative positioning when both rocker arm 103C or 103D are in positons of maximum lift with latch 1 17F in an engaging configuration. It can be seen from these illustrations that pole pieces 192K and 131 J form a sliding magnetic joint and are able to keep magnetic circuits formed by magnetic latch 1 17F and actuator 127F closed throughout the ranges of motion of rocker arms 103C and 103D, in both engaging and non-engaging configurations, and without interfering with the rocker arm motions. Pole pieces 192K and 131 J may remain continuously proximate over a large surface area. It may also be seen from these examples that similar circuits can be formed by mounting pole pieces to outer arm 103C.

[0113] 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.