Field

[0001] The present disclosure relates to valvetrains with switching or cylinder deactivating rocker arms.

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 present teachings relate to a valvetrain suitable for an internal combustion engine that includes a combustion chamber, a moveable valve having a seat formed within the combustion chamber, and a camshaft. The valvetrain includes a rocker arm assembly that has a rocker arm and a cam follower configured to engage a cam on the camshaft as the camshaft rotates. In the present teachings, the valvetrain further includes a latch assembly. The latch assembly includes a latch pin mounted on the rocker arm and an actuator. The actuator includes one or more permanent magnets. The one or more permanent magnets are mounted on a component distinct from the rocker arm, whereby the rocker arm with the latch pin mounted to it has a freedom of movement independent from the one or more permanent magnets.

[0004] The latch pin is moveable between first and second positions. The actuator is operable to move the one or more permanent magnets. The movement of the magnets induces the latch pin to translate between the first and second positions. One of the first and second latch pin positions may provide 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 first valve lift profile. The other latch pin position may provide 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 may be deactivated. In some of these teachings, the actuator is operative to simultaneously switch the valve lift profiles of or deactivate a plurality of rocker arm assemblies.

[0005] Using electromechanical latch assemblies instead of hydraulically- actuated latches can reduce complexity and demands for oil in some valvetrain systems. Mounting the actuator on parts that are distinct from the rocker arm avoids running wires to the rocker arm. Rocker arms reciprocate rapidly over a prolonged period and in proximity to other moving parts. Wires attaching to a rocker arm could be caught, clipped, or fatigued and consequently short out. An actuator according to the present teachings operates on the latch pin through magnetic forces provided by permanent magnets and does not require an electrical, mechanical, or hydraulic interface with either the latch pin or any other part of the rocker arm assembly.

[0006] In some of the present teachings, the component to which the one or more permanent magnets are mounted is a rotary shaft or another structure configured to rotate the magnets. The actuator may rotate the magnets or a component to which the one or permanent magnets are mounted. Rotation may reverse the permanent magnets poles that are nearest the latch pin.

[0007] In some of the present teachings, the actuator is operative to translate the part to which the one or more permanent magnets are mounted. In some of the present teachings, the actuator is operative to translate the one or more permanent magnets in a direction perpendicular to a direction in which the latch pin translates when moving between the first and second positions. Translation may move one or more permanent magnets toward or away from the latch pin. In some of these teachings, the translation moves a pole of one magnet toward the latch pin as it moves the pole of another magnet away from the latch pin. The pole moved away from the latch pin may have opposite polarity from the pole moved toward the latch pin.

[0008] In some of the present teachings, another permanent magnet is mounted to the latch pin. In some of these teachings, the actuator is operative to reverse the polarity of magnetic forces it exerts on the latch pin. In these teachings, the actuator may be operative both to drive the latch pin from the first position to the second position and to drive the latch pin from the second position to the first position.

[0009] In some of these teachings, a spring is configured to drive the latch pin away from the one or more permanent magnets of the actuator. In these teachings, the actuator may move one or more magnet poles into proximity with the latch pin to magnetically overcome the spring force and cause the latch pin to move from the first position to the second position. The actuator may subsequently move the one or more magnet poles away from the latch pin allowing the spring to drive the latch pin back to the first position. When a spring return is provided, a permanent magnet does not need to be mounted to the latch pin.

[0010] In some of the present teachings, a cap is mounted on the rocker arm. The cap may enclose a space surrounding an end of the latch pin that is proximate the actuator magnets. The end of the latch pin may move within the enclosed space as the latch pin translates between its first and second positions. In some of these teachings, the cap is made of non-magnetic material. The cap may prevent metal particle from accumulating on the end of the latch pin.

[0011] In some of the present teachings, the valvetrain may comprise a sweep positioned to sweep a surface of one of the permanent magnets as the actuator moves the one or more permanent magnets between the first magnet positions and the second magnet positions. The sweep may remain stationary with respect to the combustion chamber even as the actuator moves the permanent magnets relative to the combustion chamber. In some of these teachings, the sweep is in the form of a sleeve. The one or more permanent magnets may slide or rotate within the sleeve as the actuator moves them between the first and second magnet positions. The sweep may be made of low coercivity ferromagnetic material. The sweep may be operative to prevent metal particles from accumulating on the one or more permanent magnets to a point where the metal particles interfere with the operation of the latch assembly.

[0012] In some of the present teachings, the rocker arm to which the latch pin is mounted is of a design that was put into production for use with a hydraulically actuated latch. In some of these teachings, the rocker arm to which the latch pin is mounted includes a hydraulic chamber adapted to receive a hydraulically actuated latch pin. In some of these teachings, a latch pin for magnetic actuation in

accordance with the present teachings is installed in that hydraulic chamber. Rocker arms for commercial applications are typically manufactured using customized casting and stamping equipment requiring a large capital investment. The present disclosure provides designs that allow these same rocker arms to be used with a magnetically actuated latch pin.

[0013] Some aspects of the present teachings relate to a method of retrofitting for magnetic latching a rocker arm manufactured for hydraulic latching. The method includes installing a latch pin within a hydraulic chamber of the rocker arm with a portion of the latch pin protruding from the chamber. In some of these teachings, the latch pin includes a permanent magnet. The rocker arm is installed in a valvetrain with an actuator that is operative to move one or more permanent magnets between first magnet positions and second magnet positions, whereby the magnets induce the latch pin to translate between first and second latch pin positions.

[0014] Some aspects of the present teachings relate to a method of operating an internal combustion engine of a type that has a combustion chamber, a moveable valve having a seat formed in the combustion chamber, a camshaft on which a cam is mounted, a rocker arm assembly having a rocker arm, a latch pin mounted to the rocker arm, and a cam follower configured to engage the cam as the camshaft rotates. The method includes moving one or more permanent magnets from first magnet positions to second magnet positions and thereby causing the latch pin to translate between a first position and a second position through magnetic forces provided by the one or more permanent magnets. The one or more permanent magnets are subsequently returned to the first magnet positions, which results in the latch pin translating back to its first position. In some of these teaching, the latch pin is driven back to its first position by the magnets of the actuator. In some of these teaching, the latch pin is driven back to its first position by a return spring.

[0015] In some of these teachings, moving the one or more permanent magnets from the first magnet positions to the second magnet positions includes rotating a part to which the one or more permanent magnets are mounted. In some of these teachings, moving the one or more permanent magnets from the first magnet positions to the second magnet positions includes translating a part to which the one or more permanent magnets are mounted. In some of these teachings, the method further includes sweeping a surface of one the magnets to displace metal particles that have accumulates on that surface. The sweeping action may be accomplished by positioning a part to sweep the surface in conjunction with the permanent magnets being moved between the first and second magnet positions.

[0016] 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

[0017] Fig. 1 is a cut away side view of a portion of a valvetrain according to some aspects of the present teachings.

[0018] Fig. 2 is the same view as Fig. 1 , but after the magnets have rotated and the latch pin has moved from an engaging to a non-engaging position.

[0019] Fig. 3 is a sketch that illustrates a top view of the valvetrain of Fig. 1 .

[0020] Fig. 4 is a sketch that illustrates a top view of the valvetrain of Fig. 1 in the configuration of Fig. 2.

[0021] Fig. 5 is a cutaway side view of a latch pin according to some aspects of the present teachings. [0022] Fig. 6 is a flow chart of a method of operating a valvetrain according to some aspects of the present teachings.

[0023] Fig. 7 is a flow chart of a method of manufacturing a valvetrain according to some aspects of the present teachings.

[0024] Fig. 8 is a sketch that illustrates a top view of a valvetrain according to some other aspects of the present teachings.

[0025] Fig. 9 is the same view as Fig. 8, but after the magnets have been translated and the latch pin has moved from an engaging to a non-engaging position.

[0026] Fig. 10 is a sketch that illustrates a top view of a valvetrain according to some other aspects of the present teachings.

[0027] Fig. 1 1 is the same view as Fig. 10, but after the magnets have been translated and the latch pin has moved from an engaging to a non-engaging position.

Detailed Description

[0028] In the drawings, some reference characters consist of a number with a letter suffix. In this description and the claims that follow, a reference character consisting of that same number without a letter suffix is equivalent to a listing of all reference characters used in the drawings and consisting of that same number with a letter suffix. For example, "latch pin 1 13" is the same as "latch pin 1 13A, 1 13B, 1 13C".

[0029] Figs. 1 -4 illustrate a valvetrain 101 A suitable for an internal combustion engine (not shown) that includes a combustion chamber 103, a moveable valve (not shown) having a seat formed within combustion chamber 103, and a camshaft (not shown). Valvetrain 101 A includes a plurality of rocker arm assemblies 105 each of which has a rocker arm 107 and a cam follower 109 configured to engage a cam (not shown) on the camshaft as the camshaft rotates. The valvetrain 101 A further includes a latch assembly 1 1 1 A, which includes an actuator 1 15A and latch pins 1 13A. Latch pins 1 13A are mounted on rocker arms 107. Actuator 1 15A includes a plurality of permanent magnets 1 17 mounted on a rotatable shaft 1 19. Rotatable shaft 1 19 may be mounted to a cylinder head (not shown) within which combustion chamber 103 is formed. Rocker arms 107 and latch pins 1 13A have a freedom of movement independent from permanent magnets 1 17. [0030] Latch pins 1 13A are moveable between first positions, which are shown in Figs. 1 and 3, and second positions, which are shown in Figs. 2 and 4. Rocker arm assembly 105 is a cylinder deactivating rocker arm. The first positions for latch pins 1 13A may be engaging positions that put rocker arm assemblies 105 in engaging configurations. In the engaging configurations, each rocker arm assembly 105 will open and close a valve for a combustion chamber 103 in relation to the rotation of a cam. The second positions for latch pins 1 13A may be non-engaging positions that put rocker arm assemblies 105 in non-engaging configurations. In the non-engaging configurations, the valves will remain closed regardless of cam position.

[0031] Actuator 1 15A operates by rotating shaft 1 19. The rotation may be regulated by a controller, such as an engine control unit. Any suitable driving mechanism may be used. Examples of suitable driving mechanisms include without limitation mechanical, electromechanical, and hydraulic mechanisms. Rotation of shaft 1 19 moves permanent magnets 1 17 between first magnet positions, which are shown in Figs. 1 and 3, and second magnet positions, which are shown in Figs. 2 and 4.

[0032] Moving permanent magnets 1 17 between the first and second magnet positions reverses the poles of permanent magnets 1 17 that are proximate latch pins 1 13A. This reverses the polarities of the magnetic fields acting on latch pins 1 13A. Latch pin 1 13A are magnetized. When permanent magnets 1 17 are in the first magnet positions, they repel latch pins 1 13A and drive them into their engaging positions. When permanent magnets 1 17 are in the second magnet positions, they attract latch pins 1 13A sufficiently to draw them out of their engaging positions and retain them in their non-engaging positions.

[0033] Fig. 5 illustrates a latch pin 1 13B that may be used in place of latch pin 1 13A. Latch pin 1 13B includes a permanent magnet 127 attached to a load-bearing structure 125. One advantage of latch pin 1 13B is that it allows the materials of these two latch pin parts to be selected independently. The other is that it may reduce any tendency for latch pin 1 13B to stick in its engaging configuration.

[0034] Although rocker arm assemblies 105 are cylinder deactivating rocker arms, they could alternatively be switching rocker arms providing either of two valve lift profiles. Permanent magnets 1 17 may have sufficient range to maintain latch pins 1 13A in either the engaging or non-engaging configuration even as rocker arms 107 pivot in response to their being actuated by cams.

[0035] As shown in Figs. 1 and 2, rotatable shaft 1 19 along with permanent magnets 1 17 may be held within a sleeve 129. Sleeve 129 is mounted to remain stationary as shaft 1 19 rotates. As a result, a leading edge 131 of sleeve 129 will sweep a surface 133 of a permanent magnet 1 17 as shaft 1 19 rotates. The operating environment for valvetrain 101 A is likely to include oil within which metal particles may be suspended. The sweeping action of leading edge 131 may be effective to remove a build-up of those metal particles on surface 133 and maintain operability of actuator 1 15A. Sleeve 129 may be made of low coercivity

ferromagnetic material, such as soft iron.

[0036] Figs. 1 and 2 also show rocker arm 107 with an end cap 135. End cap 135 encloses a space 137 surrounding an end 139 of latch pin 1 13A that is proximate magnets 1 17 of actuator 1 15A. As latch pin 1 13A moves between engaging and non-engaging positions, end 139 translates within the space 137. End cap 135 may be made of plastic or some other non-magnetic material. End cap 135 may prevent metal particles from accumulating on end 139 of latch pin 1 13A.

[0037] Figs. 8-9 illustrate a valvetrain 101 B that is in many ways similar to valvetrain 101 A. Valvetrain 101 B includes a plurality of rocker arm assemblies 105 and a latch assembly 1 1 1 B. Latch assembly 1 1 1 B includes latch pins 1 13A mounted on rocker arms 107 and an actuator 1 15B. Actuator 1 15B includes a plurality of permanent magnets 1 17A and 1 17B mounted on a translatable shaft 121 . Translatable shaft 121 may be mounted to a cylinder head (not shown) within which combustion chamber 103 is formed.

[0038] Actuator 1 15B operates by moving shaft 121 in a direction perpendicular to a direction in which latch pins 1 13A translate when moving between their first and second positions. The movement may be regulated by a controller, such as an engine control unit. Any suitable driving mechanism may be used. Examples of suitable driving mechanisms include without limitation mechanical,

electromechanical, and hydraulic mechanisms.

[0039] Translation of shaft 121 moves permanent magnets 1 17A and 1 17B between first magnet positions, which are shown in Fig. 8, and second magnet positions, which are shown in Fig. 9. In the first magnet positions, North poles of permanent magnets 1 17A are proximate latch pins 1 13A and permanent magnets 1 17B are relatively distant from latch pins 1 13A. In the second magnet positions, South poles of permanent magnets 1 17B are proximate latch pins 1 13A and permanent magnets 1 17A are relatively distant from latch pins 1 13A. The overall effect is to reverse the polarity of the magnetic forces applied by permanent magnets 1 17A and 1 17B on latch pins 1 13A. Moving permanent magnets 1 17A and 1 17B into the first magnet positions causes latch pin 1 13A to move into and remain in first positions, which are engaging positions. Moving permanent magnets 1 17A and 1 17B into the second magnet positions causes latch pin 1 13A to move into and remain in second positions, which are non-engaging positions. A sleeve may be provided to sweep the surfaces of permanent magnets 1 17A and 1 17B as they translate back and forth.

[0040] Figs. 10-1 1 illustrate a valvetrain 101 C that is in many way similar to valvetrain 101 B. Valvetrain 101 C includes a plurality of rocker arm assemblies 105 and a latch assembly 1 1 1 C. Latch assembly 1 1 1 C includes latch pins 1 13C and springs 123, which are mounted on rocker arms 107, and an actuator 1 15C including permanent magnets 1 17 mounted on a translatable shaft 121 . Latch pins 1 13C do not need to include permanent magnets. Latch pins 1 13C are made from, or include, magnetically susceptible material. Springs 123 bias latch pins 1 13C into their engaging positions. Alternatively, rocker arm assemblies 105 could also be structured such that these latch pin positions, which are the ones more distal from permanent magnets 1 17, are non-engaging positions.

[0041] Actuator 1 15C operates by moving shaft 121 in a direction perpendicular to a direction in which latch pins 1 13A translate when moving between their first and second positions. Translation of shaft 121 moves permanent magnets 1 17 between first magnet positions, which are shown in Fig. 10, and second magnet positions, which are shown in Fig. 1 1 . In the first magnet positions, poles of permanent magnets 1 17 are proximate latch pins 1 13C. In the second magnet positions, poles of permanent magnets 1 17 are relatively distant from latch pins 1 13C. Moving permanent magnets 1 17 into the first magnet positions results in magnets 1 17 overcoming the forces of springs 123 and moving latch pins 1 13C into their non- engaging positions. Moving permanent magnets 1 17 into the second magnet positions reduces the magnetic forces on latch pins 1 13C, which allows springs 123 to overcome the magnetic forces and drive latch pins 1 13C back into their engaging positions. The concept of a spring return is also applicable with an actuator 1 15A, which operates by rotating shaft 1 19.

[0042] Fig. 6 provides a flow chart of a method 200 of operating an internal combustion engine of a type that has a combustion chamber, a moveable valve having a seat formed in the combustion chamber, a camshaft on which a cam is mounted, a rocker arm assembly having a rocker arm, a latch pin mounted to the rocker arm, and a cam follower configured to engage the cam as the camshaft rotates. Method 200 includes action 201 , which is moving one or more permanent magnets 217 from first magnet positions to second magnet positions and thereby causing latch pin 1 13 to translate between a first position and a second position. Method 200 also includes action 203, moving the one or more permanent magnets 217 back to the first magnet positions and thereby causing latch pin 1 13 to translate back to the first position. One or both latch pin movements may be driven by magnetic forces provided by permanent magnets 217. In some embodiments, one of the movements is driven by a spring. In some embodiments, the movements of actions 201 and 203 are rotations of magnets 217. In some embodiments, the movements of actions 201 and 203 are translations of magnets 217. In some embodiments, one or both of actions 201 and 203 move a surface 133 of a magnet 217 past a sweep 131 that displaces metal particles that have accumulates on surface 133.

[0043] Fig. 7 provides a flow chart of a manufacturing method 210 in accordance with some aspects of the present teachings. Method 210 begins with action 21 1 , a design operation in which a rocker arm assembly 105 including a hydraulically actuated latch may be designed in detail. The design may be made without specifications for a latch assembly 1 1 1 according to the present teachings. Method 210 continues with action 213, building casting and stamping equipment sufficient for implementing the design of action 21 1 . Action 213 is using that equipment to manufacture a rocker arm 107 having a hydraulic chamber 141 . Action 215 is installing a latch pin 1 13 according to the present teachings within the hydraulic chamber 141 . The rocker arm assembly may then be used in a valvetrain 101 according to the present teachings.

[0044] 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.