Field

[0001] The present teachings relate to valvetrains, particularly valvetrains providing switching rocker arms that implement variable valve lift (VVL), cylinder deactivation (CDA), or engine braking.

Background

[0002] Hydraulically actuated latches are used on some rocker arm assemblies to implement variable valve lift (VVL), cylinder deactivation (CDA), or engine braking. 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).

Summary

[0003] Some aspects of the present teachings relate to a valvetrain for an internal combustion engine of a type that has a combustion chamber and a moveable valve having a seat formed in the combustion chamber. The valvetrain includes a rocker shaft, a camshaft, a rocker arm assembly, and an electromagnetic latch assembly. The rocker arm assembly includes a valve side rocker arm and a cam side rocker arm. The valve side rocker arm is rotatably mounted on the rocker shaft. The cam side rocker arm carries or provides a cam follower configured to engage a cam mounted on the camshaft as the camshaft rotates. The valve side rocker arm and the cam side rocker arm are pivotally connected through a pivot axle. The electromagnetic latch assembly includes a latch pin and an electromagnet operable to cause the latch pin to translate between a non-engaging position in which the valve side rocker arm is able to rotate relative to the cam side rocker arm about the pivot axle and an engaging position in which that relative rotation is restricted by the latch pin. The electromagnetic latch assembly provides faster switching and a broader operating temperature range compared to a hydraulic latch system.

[0004] In some of these teachings, the first latch pin position provides a configuration in which the rocker arm assembly is operative to actuate the moveable valve in response to rotation of a camshaft to produce a first valve lift profile while the second latch pin position provides a configuration in which the rocker arm assembly is operative to actuate the moveable valve in response to rotation of the camshaft to produce a second valve lift profile, which is distinct from the first valve lift profile, or the moveable valve is deactivated. Accordingly, the system may implement cylinder deactivation (CDA), variable valve actuation (VVA), or the like.

[0005] In some of these teachings, the electromagnet is mounted to the rocker arm assembly. This configuration provides simplifies the interface between the electromagnet and the latch pin while creating challenges for powering the electromagnet, which moves with the rocker arm assembly part to which the electromagnet is mounted. In some of these teachings, power transfer is made through a sliding connection. A sliding connection may be, for example, a connection formed by a contact pin on the rocker arm assembly and a contact pad that is held stationary with respect to the cylinder head. The contact pin may slide over the contact pad as the rocker arm assembly moves. In some of these teachings, the connection is made with a conductive spring. In some of these teachings, power is transferred inductively to the electromagnet’s circuit. In some of these teachings, a ground connection is formed through the structure of the rocker arm assembly.

[0006] In some aspects of the present teachings, the electromagnet is mounted to a part distinct from the rocker arm assembly and a mechanical interface is provided between an armature moved by the electromagnet and the latch pin. In some of these teachings, the mechanical interface includes an actuator shaft that abuts the latch pin.

In some of these teachings, the actuator shaft is decoupled from the latch pin. In some of these teachings, the actuator shaft travels through a slot formed in one the rocker arms assembly components at least when the latch pin is in the engaging position. In some of these teachings, the slot is formed in one of the rocker arms. In some of these teachings, the slot is formed in the outermost of two telescoping parts. In some of these teachings, the slot has a shape that traces an arc about the rocker shaft.

[0007] In some of these teachings, the electromagnetic latch assembly includes an armature and a mechanical interface between the armature and the latch pin. The electromagnet is operable to move the armature between a retracted position and an extended position. The mechanical interface is structured to provide compliance allowing the armature to move from the retracted position to the extended position while the cam is on lift and the latch pin remains stationary and to actuate the latch pin position when the cam descends to base circle with the armature remaining in the extended position. This structure allows actuation to be initiated at any time regardless of camshaft position.

[0008] In some of these teachings, the electromagnetic latch assembly further includes an armature and a mechanical interface between the armature and the latch pin. The electromagnet is operable to move the armature between a retracted position and an extended position. The mechanical interface is structured to amplify the armature motion whereby a distance travelled by the latch pin in response to armature motion is greater than a distance travelled by the armature. This motion amplification system allows a target range of motion for the latch pin to be achieved with a smaller electromagnet. [0009] In some of these teachings, the rocker arm assembly is one of a plurality of rocker arm assemblies, the latch pin is one of a plurality of latch pins each latch pin associated with one of the plurality of rocker arm assemblies, and the electromagnetic latch assembly comprises a shaft through which the electromagnet is operable to cause each of the plurality of latch pins to translate between a first position and a second position. This system allows a plurality of latches to be actuated using one electromagnet.

[0010] In some of these teachings, the electromagnetic latch assembly includes an armature and a mechanical interface between the armature and the latch pin. The electromagnet is operable to move the armature between a retracted position and an extended position. According to these teachings, the electromagnetic latch assembly is structured to provide the armature with positional stability independently from the electromagnet both when the armature is in the extended position and when the armature is in the retracted position. This dual positional stability enables the electromagnetic latch assembly to retain both latched and unlatched states without power to the electromagnetic. Designing the electromagnetic latch assembly to be operative with only short bursts of power allows the use of a small coil without overheating.

[0011] In some of these teachings, a permanent magnet contributes to the positional stability of the armature both when the armature is in the extended position and when the armature is in the retracted position. According to some further aspects of these teachings, the electromagnetic latch assembly is structured to operate through a magnetic circuit-shifting mechanism. In some of these teachings, absent any magnetic fields generated by the electromagnet or other external sources, when the armature is in the extended position, an operative portion of the magnetic flux from the permanent magnet follows a first magnetic circuit and when the armature is in the retracted position, an operative portion of the magnetic flux from the permanent magnet follows a second magnetic circuit distinct from the first magnetic circuit. The electromagnet 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 armature 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. An electromagnetic latch assembly structured to be operable through a magnetic circuit-shifting mechanism may be smaller than one that is not so structured and may be operative with a smaller electromagnet.

[0012] In some of these teaching, the electromagnet encircles a volume within which a portion of the armature comprising low coercivity ferromagnetic material translates and the electromagnetic latch assembly comprises one or more pole pieces of low coercivity ferromagnetic material outside the volume encircled by the electromagnet. The one or more pole pieces outside the volume encircled by the electromagnet may form a capped can around the electromagnet. Both the first and the second magnetic circuits pass through the armature portion formed of low coercivity ferromagnetic material. In some of these teachings, the first magnetic circuit passes around the outside of the electromagnet via the one or more pole pieces while the second magnetic circuit does not pass around the outside of the electromagnet. This characteristic of the second magnetic circuit reduces magnetic flux leakage and increases the force with which the permanent magnet holds the armature in the retracted position.

[0013] In some of these teachings, the electromagnetic latch assembly includes a second permanent magnet distal from the first permanent magnet 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 the path taken by an operative portion of the magnet flux from the second permanent magnet depending on the whether the armature is in the extended position or the retracted position. The path taken when the armature is in the retracted position may pass around the outside of the electromagnet via the pole pieces. The path taken when the armature is in the extended position may be a shorter path that does not pass around the outside of the electromagnet. One or the other of the permanent magnets may then provide a high holding force depending on whether the armature is in the extended position or the retracted position. In some of these teachings, both permanent magnets contribute to the positional stability of the armature in both the extended position or the retracted position. In some of these teachings, the two magnets are arranged with confronting polarities. In some of these teachings, the two magnets are located at distal ends of the volume encircled by the electromagnet. In some of these teachings, the permanent magnets are annular in shape and polarized along the directions of their axis. These structures may be conducive to providing a compact and efficient design. Whether the armature is in the extended position or the retracted position, the armature is held by magnetic flux following a short flux path, resulting in low flux leakage and allowing the permanent magnets to be made smaller.

[0014] In some of the present teaching, the circuit that powers the electromagnet is operable to energize the electromagnet with a current in either a first direction or a second direction, which is the reverse of the first direction. An electromagnetic latch assembly having dual positional stability may require the electromagnet current to be in one direction for latching and the opposite direction for unlatching. The electromagnet powered with current in the first direction may be operative to actuate the armature from the extended position to the retracted position. The electromagnet powered with current in the second direction may be operative to actuate the armature from the retracted position to the extended position.

[0015] In some embodiments, the circuit includes a first wire that is isolated from ground and components such as capacitors and switches operable to provide the first wire with voltage at a potential that is either above ground or below ground. The circuit may include a second wire that is grounded, or the circuit may form a ground connection through a structural component of the valvetrain such as a valve, the camshaft, or the rocker shaft. Accordingly, the electromagnet may be powered using a single wire.

[0016] In some of these teaching, the electromagnetic latch assembly includes an actuator and a mechanical interface between the latch pin and the actuator and the dual positional stability is provided by a plunger and a cam within the mechanical interface. The cam is configured undergo rotation in response to translation of the armature. Rotation of the cam alternates the plunger between a configuration in which the plunger is stable in an extended position and a configuration in which the plunger is stable in a retracted position.

[0017] A valvetrain according to the present teachings can have various structural implementations. In some of these teachings, the latch pin translates between the first latch pin position and the second latch pin position by translating parallel to an axis of the rocker shaft. In some embodiments, the latch pin is one of two latch pins disposed on opposite sides of the rocker arm assembly. Using two latch pins on opposite side of the rocker arm assembly balances forces that might otherwise tend to tilt the rocker arm assembly off an axis of the rocker shaft.

[0018] The latch pin may move to selectively pin the valve side rocker arm to the cam side rocker arm. In some of these teachings, the rocker arm assembly includes a telescoping interface between the cam side rocker arm and the valve side rocker arm. The telescoping part may telescope in relation to relative rotation of the cam side rocker arm and the valve side rocker arm about the pivot axle. In these embodiments, the latch pin moves to selectively pin the inner sleeve to the outer sleeve. In some of these embodiments, the telescoping parts are structured to restrict relative rotation between the inner body and the outer body to prevent misalignment of the latch pin to openings in the inner and outer body.

[0019] The present teachings are useful for repurposing the rocker arms of a rocker arm assembly designed for hydraulic actuation to be used with electromagnetic actuation. Accordingly, another aspect of the present teachings is a method of manufacturing a valvetrain. The method includes manufacturing the valve side rocker arm with a hydraulic chamber for receiving hydraulic fluid to drive a latch pin from the hydraulic chamber into the cam side rocker arm. An opening is formed in the hydraulic chamber for receiving an actuator shaft driven by an electromagnetic latch assembly. In some of these teachings, the opening is a slot.

[0020] Another manufacturing method according to the present teaching includes manufacturing a rocker arm assembly with a extensible structure that include an inner body and an outer body. The inner body and the outer body form a hydraulic chamber for receiving hydraulic fluid to drive a latch pin from an engaging position to non engaging position. An opening onto the hydraulic chamber is formed in the outer body for receiving an actuator shaft driven by an electromagnetic latch assembly according to the present teachings. In some of these teachings, the opening is a slot.

[0021] According to some of the present teachings, in the engaging position the latch pin abuts two parts and in the non-engaging position the latch pin abuts only one of the two parts. In some embodiments, a spring is provided to bias the latch pin into the latching position. In some embodiments, in the engaging position the latch pin abuts both the valve side rocker arm and the cam side rocker arm and in the second position the latch pin is held entirely within the cam side rocker arm. A slot may be formed in the valve side rocker arm to allow the latch pin to be held inside the cam side rocker even as the cam side rocker arm moves past the actuator shaft. In some embodiments, in the engaging position the latch pin abuts both the inner sleeve and the outer sleeve of a extensible structure and in the non-engaging position the latch pin is held entirely within the inner sleeve. A slot may be formed in the outer sleeve to allow the latch pin to be held within the inner sleeve even as the outer sleeve moves relative to the actuator shaft.

[0022] The primary purpose of this summary has been to present broad aspects of the present teachings in a simplified form to facilitate understanding of the present disclosure. This summary is not a comprehensive description of every aspect of the present teachings. Other aspects of the present teachings will be conveyed to one of ordinary skill in the art by the following detailed description together with the drawings.

Brief Description of the Drawings

[0023] Fig. 1 is a view of an engine with a valvetrain according to the present teachings.

[0024] Fig. 2 provides a perspective view of a portion of the valvetrain of Fig. 1 .

[0025] Fig. 3 provides a perspective view of a rocker arm assembly of the valvetrain of Fig. 1.

[0026] Fig. 4 provides a cutaway top view of an exhaust side rocker arm assembly of the valvetrain of Fig. 1 in a non-latching configuration.

[0027] Fig. 5 provides a cutaway top view of an exhaust side rocker arm assembly of the valvetrain of Fig. 1 in a latching configuration.

[0028] Fig. 6 illustrate a variation of the rocker arm assembly of Fig. 5 according to some other aspects of the present teachings.

[0029] Fig. 7 provides a side view of a portion of the rocker arm assembly of Fig. 6.

[0030] Fig. 8 is a view of another engine with a valvetrain according to some aspects of the present teachings with a cam on base circle.

[0031] Fig. 9 is the view of Fig. 8 with the cam on lift and the rocker arms latched.

[0032] Fig. 10 is a perspective view of a rocker arm assembly of the valvetrain of Fig.

8 showing the latch pin location.

[0033] Fig. 11 is the view of Fig. 10 with the latch pin in a non-latching position and with the cam on lift. [0034] Fig. 12 illustrates a portion of the rocker arm assembly of Fig. 10 with an electromagnetic latch assembly according to the present teachings.

[0035] Fig. 13 illustrates a variation on the rocker arm assembly of Fig. 10 according to some aspects of the present teachings and with the cam on lift in a non-latching configuration.

[0036] Fig. 14 illustrates the rocker arm assembly of Fig. 13 with the cam on lift in a latching configuration.

[0037] Fig. 15 is a cross-sectional view of an actuator used in some aspects of the present teachings with its armature in an extended position. [0038] Fig. 16 is the actuator of Fig. 15 with the armature in a retracted position.

[0039] Fig. 17 illustrates a portion of the valvetrain of Fig. 8 with an electromagnetic latch assembly according to some other aspects of the present teachings.

[0040] Fig. 18 illustrates the rocker arm assembly of Fig. 13 with an electromagnetic latch assembly and a mechanical interface according to some other aspects of the present teachings.

[0041] Fig. 18A illustrates a portion of the mechanical interface of Fig. 18.

[0042] Fig. 19 illustrates a portion of the rocker arm assembly of Fig. 13 with a mechanical interface according to some other aspects of the present teachings.

[0043] Fig. 20 illustrates an electromagnetic latch assembly with mechanical interfaces for a plurality of rocker arm assemblies according to some aspects of the present teachings.

Detailed Description

[0044] Fig. 1 illustrates an internal combustion engine 1 that includes a valvetrain 2 according to some aspects of the present teachings. The valvetrain 2 is installed on a cylinder head 3. Fig. 2 illustrate a portion 4 of valvetrain 2 associated with one cylinder (not shown) having valve seats (not shown) formed in the cylinder head 3. The valvetrain 2 includes a camshaft 39, a rocker shaft 42, rocker arm assemblies 5A, rocker arm assemblies 5B, and two electromagnetic latch assemblies 25. Each of the rocker arm assemblies 5A is configured to actuate two exhaust valves 10 and a rocker arm assembly 5B configured to actuate two intake valves 9.

[0045] Fig. 3 provides a perspective view of one of the rocker arm assemblies 5B showing that it includes a valve side rocker arm 11B connected to a cam side rocker arm 6 through a pivot axle 15. A cam follower 14 that interfaces with a cam 38 (see Fig. 8) is mounted to the cam side rocker arm 6 through a cam axle 43. The valve side rocker arm 11 B includes an opening 16 that fits around a rocker shaft 8 (see Fig. 2). An extensible structure 13A is positioned between the valve side rocker arm 11 B and the cam side rocker arm 6 about the pivot axle 15. The two electromagnetic latch assemblies 25 are mounted on opposites sides of the extensible structure 13A [0046] Fig. 4 provides a cutaway top view of the rocker arm assembly 5B, which is a cylinder deactivating rocker arm. As shown in Fig. 4, the extensible structure 13A includes an inner body 21 and an outer body 12 that may be integral with the valve side rocker arm 11 B. Latch pins 20 selectively engage the inner body 21 and the outer body 12. If the armatures 27 are retracted as shown in Fig. 4, the latch pins 20 are in engaging positions. In the engaging positions, the latch pins 20 pin the inner body 21 to the outer body 12 restricting extension and retraction of the extensible structure 13A. If the cam follower 14 is actuated by the cam 38 while the latch pins 20 are in engaging positions, the rocker arm assembly 5B will rotate as a unit on the rocker shaft 8 to actuate the exhaust valves 10.

[0047] The armatures 27 may be retracted by powering the electromagnets 26. In some embodiments, the armatures 27 are attached to or unitary with the latch pins 20 and the electromagnets 26 draw the latch pins 20 into their engaging positions. In some embodiments, such as the one illustrated in Fig. 4, the latch pins 20 are decoupled from the armatures 27. In those embodiments, springs 22 may be used to drive the latch pins 20 into their engaging positions when the armatures 27 are retracted. Extending the armatures 27 drives the latch pins 20 into non-engaging positions as shown in Fig. 5 [0048] If the cam follower 14 is actuated by the cam 38 while the latch pins 20 are in their non-engaging positions, the extensible structure 13 will contract, the valve side rocker arm 11 will remain stationary, and the cam side rocker arm 6B rotates on the pivot axle 15. The exhaust valves 10 will remain on their respective valve seats (not shown) and a lost motion spring 23 and a lost motion spring 24 will be compressed.

The lost motion spring 23 and the lost motion spring 24 will drive the extensible structure 13 back into extension as the cam 38 returns to base circle.

[0049] Parts of the rocker arm assembly 5B may have been designed for hydraulic actuation. The outer body 12 and the inner body 21 may form a chamber 28. Pressurizing the chamber 28 with hydraulic fluid may be operative to drive the latch pins 20 into the non-engaging configuration. Accordingly, the rocker arm assembly 5B may have been retrofit for electromagnetic latch actuation.

[0050] Fig. 6 shows a rocker arm assembly 5C that is like rocker arm assembly 5B except that it is adapted to allow the electromagnetic latch assemblies 25 to be mounted to parts distinct from the rocker arm assembly 5C and may remain stationary relative to the cylinder head 3. If the rocker arm assembly 5C is actuated by the cam 38 while the armatures 27 are extend to hold the latch pins 20 in their non-engaging positions, the latch pins 20 may move with the inner body 21. This motion may pull the latch pins 20 out of engagement with the armatures 27. The outer body 12 may prevent the latch pins 20 from moving outward, whereby the latch pins 20 may slide back over the armatures 27 as the cam 38 returns to base circle.

[0051] If the rocker arm assembly 5C is actuated by the cam 38 while the armatures 27 are retracted and the latch pins 20 are their non-engaging positions, the latch pins 20 may move away from the armatures 27 together with the inner body 21 and the outer body 12. As shown in Fig. 7, a slot 30 formed in the outer body 12. The armatures 27 may then travel back and forth across the slot 30 as the rocker arm assembly 5C pivots back and forth on the rocker shaft 42 in relation to the rotation of the camshaft 39. The slot 30 may trace an arc centered on the rocker shaft 42 to accommodate this motion. [0052] Figs. 8-9 illustrate an in internal combustion engine 31 that has parts similar to the internal combustion 1 including a valvetrain 44 that has parts similar to the valvetrain 2. The valvetrain 44 includes rocker arm assemblies 5D, the rocker shaft 42, and the camshaft 39 on which the cams 38 are mounted. The camshaft 39 may be held by a cam cap 7 to the cylinder head 3 or another part that is held to the cylinder head 3 such as a cam carrier. The rocker arm assemblies 5D are similar to the rocker arm assemblies 5A-5C and include a valve side rocker arm 11 D connected to a cam side rocker arm 6D through the pivot axle 15. The cam side rocker arm 6D includes the cam follower 14 that interfaces with the cam 38. The valve side rocker arm 11 D pivots on the rocker shaft 42. The lost motion spring 24 biases the valve side rocker arm 11 D and the cam side rocker arm 6D apart about the pivot axle 15. The cam side rocker arm 6D will pivot on the pivot axle 15 and lost motion spring 24 will extend and retract in relation to rotation of the camshaft 39 when the valve side rocker arm 11 D and the cam side rocker arm 6D are disengaged.

[0053] Fig. 8 illustrates the valvetrain 44 with the cam 38 is on base circle. Fig. 9 illustrates the valvetrain 44 with the cam 38 on lift and the valve side rocker arm 11 D and the cam side rocker arm 6D are latched together. In the latched configuration the valve side rocker arm 11 D and the cam side rocker arm 6D pivot as a unit on the rocker shaft 42 in relation to rotation of the camshaft 39, opening and closing the valve 10.

The lost motion spring 24 undergoes little or no compression during this cycling.

[0054] If the valve side rocker arm 11 D and the cam side rocker arm 6D are not latched together, the lost motion spring 24 will compress as the cam 38 goes on lift.

The cam side rocker arm will pivot on the pivot axle 15 in relation to rotation of the camshaft 39. The valve side rocker arm 11 D will either remain stationary, providing CDA, or another cam will directly lift the valve side rocker arm 11 D by a reduced amount, providing VVA.

[0055] Figs. 10 and 11 provides cutaway views of the rocker arm assembly 5D showing a latch pin 46 that selectively latches the valve side rocker arm 11 D and the cam side rocker arm 6D. The latch pin 46 is configured to translate parallel to an axis of the rocker shaft 8, which is also a direction parallel to the camshaft 39 (see Fig. 9). In an engaging position, the latch pin 46 threads the valve side rocker arm 11 D and the cam side rocker arm 6D. In the non-engaging position, shown in Fig. 11 , the latch pin 46 is held entirely within the valve side rocker arm 11 D.

[0056] Fig. 12 provides a partial view of the rocker arm assembly 5D along with an electromagnetic latch assembly 53. The electromagnetic latch assembly 53 includes an actuator 59 and an actuator shaft 52. The actuator shaft 52 passes through an opening 55 in valve side rocker arm 11 D to connect with an actuating member 61 that is attached to or is integral with the actuator shaft 52. The actuating member 61 interfaces with the latch pin 46. In the engaging position, which is shown in Fig. 12, the latch pin 46 may be partially within a bore 51 formed in valve side rocker arm 11 D, partially within a bore 62 formed in the cam side rocker arm 6D, and may abut the actuating member 61. The bore 51 and the bore 62 may have approximately the same diameter. That diameter may be approximately the same as a diameter of the latch pin 46 except for a tolerance that allows the latch pin 46 to travel within the bore 51 and the bore 62 over a range of operating temperatures.

[0057] The electromagnetic latch assembly 53 is operative to extend the actuator shaft 52, overcoming the force of a spring 54 that biases the latch pin 46 into the engaging position and driving the latch pin 46 out of the bore 51 into a non-engaging position. The latch pin 46 may be driven entirely within the bore 62. If the cam side rocker arm 6D goes on lift, as shown in Fig. 11 , while the latch pin 46 is in the non engaging position, the latch pin 46 may move away from the actuating member 61. If this happens, the latch pin 46 may be held in the non-engaging position by the valve side rocker arm 11 D until the latch pin 46 moves back in alignment with the bore 51 and the actuating member 61 .

[0058] The bore 51 may have been originally designed as a hydraulic chamber. Accordingly, the valve side rocker arm 11 D may have been formed with the same casting and stamping equipment used for a rocker arm assembly with a hydraulically actuated latch. A hydraulic fluid passage 50 is typically formed after casting and stamping and may or may not be present.

[0059] The electromagnetic latch assembly 53 is mounted to the valve side rocker arm 11 D of the rocker arm assembly 11 D. Figs. 13 and 14 illustrate an alternate embodiment in which the electromagnetic latch assembly 53 is mounted a part distinct from the rocker arm assembly 5D. In this embodiment, the actuating member 61 is eliminated and the actuator shaft 52 is allowed to at directly on the latch pin 46 at least when the cam 38 is on base circle. At least when the latch pin 46 is in the engaging position, the valve side rocker arm 11 D will move while the actuator shaft 52 remains stationary. The opening 55 is extended by a slot 63 to accommodate this motion. If the cam 38 goes on lift while the latch pin 46 is in the engaging position, then valve side rocker arm 11 D will pivot on the rocker shaft 42 causing the actuator shaft 52 to travel across the slot 63. Accordingly, the slot 63 has dimension at least sufficient for the actuator shaft 52 to trace an arc about the rocker shaft 42.

[0060] Figs. 15 and 16 show an electromagnetic latch assembly 122 that may be used in place of the actuator 59 or any other electromagnetic latch assembly in the present disclosure. The electromagnetic latch assembly 122 includes an electromagnet 119, an armature 131 , and two permanent magnets 120A and 120B arranged with confronting polarities. The two permanent magnets 120A and 120B may be arranged with confronting polarities and may be separated by a low coercivity ferromagnetic ring 121 . The electromagnet 119 may be a coil of wire wound about a bobbin 114 and contained within a low coercivity ferromagnetic shell 116. The two permanent magnets 120A and 120B and the ferromagnetic ring 121 may be disposed within the electromagnet 119. The ferromagnetic ring 121 may have a smaller ID than the permanent magnets 120A and 120B and supports the armature 131 , keeping the armature 131 from contacting permanent magnets 120A and 120B.

[0061] Figs. 15 shows the armature 131 in a first position, which is an extended position, and Fig. 16 shows the armature 131 in a second position, which is a retracted position. The permanent magnets 120A and 120B operate on the armature 131 through low coercivity ferromagnetic ferule 123. The magnetic circuits taken by flux from the permanent magnets 120A and 120B vary as the armature 131 moves between the first position and the second position. In the first position, the flux from the permanent magnet 120A follows a magnetic circuit 128 (see Fig. 15) which includes the ferromagnetic ring 121 and the ferule 123 and goes around the electromagnet 119 through the shell 116. In the second position, flux from the permanent magnet 120A follows a magnetic circuit 127 (see Fig. 16), which also includes the ring 121 and the ferule 123 but only a small portion of the shell 116. The magnetic circuit 127 is a very tight magnetic circuit with a low flux leakage. This flux shifting mechanism allows the same permanent magnets 120A and 120B that hold the armature 131 in the extended position to also hold the armature 131 in the retracted position.

[0062] The electromagnet 119 is operable to alter magnetic polarizations in the magnetic circuits taken by flux from the permanent magnets 120A and 120B. Energized with current in a first direction, the electromagnet 119 is operable to cause the armature 131 to translate from the first position to the second position. Once the armature 131 is in the second position, the permanent magnets 120A and 120B will stably maintain the armature 131 in the second position after power to the electromagnet 119 is cut off. Energized with current in a second direction, which is a reverse of the first, the electromagnet 119 is operable to cause the armature 131 to translate from the second position back to the first position. Once the armature 131 is in the first position, the permanent magnets 120A and 120B will stably maintain the armature 131 in the first position after power to the electromagnet 119 is again cut off.

[0063] As shown in Fig. 17, the electromagnetic latch assembly 122 may be attached to the rocker arm 11 D through a mounting frame 132 and the armature 131 may act directly on the latch pin 46 through the actuator shaft 52. Alternatively, as shown in Fig. 18, the actuator shaft 52 may be replaced by a more complex mechanical interface 60. The mechanical interface 60 may amplify the motion of the armature 131 whereby a distance travelled by the latch pin 46 is greater than a distance travelled by the armature 131. The mechanical interface 60 may include a compliance spring or the like, whereby if the armature 131 moves to push the latch pin 46 into the non-engaging position while the latch pin 46 is under load, mechanical energy is stored. When the load is relieved, the stored energy is released by the compliance spring (not shown) to move the latch pin 46 to the non-engaging position. Retracting the plunger 70 will allow the spring 54 (see Fig. 12) to move latch pin 46 back into the engaging position.

[0064] As shown by Fig 18A, the mechanical interface 60 may include a cam system 64 similar to that of a ball point pen. The cam system 64 allow the benefits of the bi stable electromagnetic latch assembly 122 to be achieved with a conventional solenoid. Cam system 62 includes a plunger 70 and a cam 71. Energizing the electromagnet 119 for a brief period causes the armature 131 to push down on the plunger 70, which in turn causes the cam 71 to rotate and toggle the cam system 64 between extended and retracted positions.

[0065] Fig. 19 shows another mechanical interface 74 that provides compliance and may be used between to actuate latch pin 46. As shown in Fig. 20, the mechanical interface 74 may be one of a plurality of mechanical interfaces 74 on a shaft 75 that is driven by a single actuator 72. Each mechanical interface 74 may operate on a distinct latch pin 46 of a distinct rocker arm assembly 5D.

[0066] The components and features of the present disclosure have been shown and/or described in terms of certain teachings 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 some aspects of the present teachings or some examples, 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.