WO2017091798A1

WO2017091798A1 - Hydraulic lash adjuster with electromechanical rocker arm latch linkage

Info

Publication number: WO2017091798A1
Application number: PCT/US2016/063729
Authority: WO
Inventors: James Mccarthy, Jr.; Hongbin N. Wang; Craig Steven Jacobs; Matthew Vance; Matthew Busdiecker
Original assignee: Eaton Corporation
Priority date: 2015-11-25
Filing date: 2016-11-24
Publication date: 2017-06-01

Abstract

A valvetrain for an internal combustion engine of the type that has a combustion chamber, a moveable valve having a seat formed in the combustion chamber, and a camshaft includes a rocker arm assembly, a pivot providing a fulcrum for a rocker arm of the rocker arm assembly, and a latch assembly. The latch assembly includes a latch pin mounted on the rocker arm, an electromechanical actuator mounted to the pivot, and a mechanical linkage between the latch pin and the electromechanical actuator. The electromagnetic actuator may be packaged adjacent to or within the pivot to provide a compact design that does not require wiring to the rocker arm.

Description

HYDRAULIC LASH ADJUSTER WITH ELECTROMECHANICAL ROCKER ARM LATCH

LINKAGE

Field

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

Priority

[0002] The present application claims priority from US Provisional Patent Application No. 62/259,841 filed November 25, 2015.

Background

[0003] Hydraulically actuated latches are used on some rocker arm assemblies to implement variable valve lift (VVL) or cylinder deactivation (CDA). For example, some switching roller finger followers (SRFF) use hydraulically actuated latches. In these systems, pressurized oil from an oil pump may be used for latch actuation. The flow of pressurized oil may be regulated by an oil control valve (OCV) under the supervision of an engine control unit (ECU). A separate feed from the same source may provide oil for hydraulic lash adjustment. In these systems, each rocker arm assembly has two hydraulic feeds, which entails a degree of complexity and equipment cost.

[0004] The oil demands of valvetrains with hydraulically actuated latches may approach the limits of existing supply systems. The complexity and demands for oil in these valvetrain systems can be reduced by replacing hydraulically latched rocker arm assemblies with electrically latched rocker arm assemblies. Electromechanical latch actuators that mount off the rocker arm assemblies may be difficult to accommodate in the limited space available under the valve cover. Electromechanical latch actuators that mount to rocker arms may be difficult to power. Rocker arms reciprocate rapidly. Wires running to a rocker arm might be caught, clipped, or fatigued and consequently short out.

Summary

[0005] 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, a pivot, and a latch assembly. The rocker arm assembly includes a rocker arm and a cam follower configured to engage a cam on a camshaft as the camshaft rotates. The pivot provides a fulcrum for the rocker arm. The latch assembly includes a latch pin mounted on the rocker arm, an electromechanical actuator that is mounted to the pivot, and a mechanical linkage between the latch pin and the electromechanical actuator. The electromechanical actuator is operable to actuate the latch pin between a first position and a second position through the mechanical linkage. In some of these teachings, the pivot is a lash adjuster.

[0006] In some of these teachings, the electromechanical actuator is mounted inside the pivot, which may protect the actuator from metal particles carried by engine oil. In some of these teachings, the electromechanical actuator is mounted to a side of the pivot. The mechanical linkage extends from the pivot to the rocker arm. In some of these teachings, the mechanical linkage extends from inside the pivot to the rocker arm. In some of these teachings, the mechanical linkage passes through an enclosed interface between the pivot and the rocker arm.

[0007] In some of these teachings, the rocker arm assembly is operative to form a force transmission pathway between a cam and a moveable valve. The pathway may include the rocker arm, which may pivot on the fulcrum. In some of these teachings, one of the first and second latch pin positions provides a configuration in which the rocker arm assembly is operative to actuate a moveable valve in response to rotation of a camshaft to produce a first valve lift profile and the other of the first and second latch pin positions 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. In some of the present teachings, the electromechanical actuator is operative to actuate the latch pin from the engaging to the non- engaging position.

[0008] The rocker arm assembly may include two rocker arms. The latch pin may be mounted to one rocker arm while the cam follower is mounted to the other. In some of these teachings, one of the first and second latch pin positions provides a configuration in which motion of the rocker arm to which the latch pin is mounted is decoupled from motion of the rocker arm assembly induced by a cam displacing the cam follower.

[0009] In some of these teachings, the pivot is a hydraulic lash adjuster. In some of these teachings, the rocker arm includes a hydraulic chamber and the mechanical linkage passes through a port designed to provide hydraulic fluid to that hydraulic chamber. In some of these teachings, the hydraulic lash adjuster is a dual feed hydraulic lash adjuster originally designed to provides hydraulic fluid to the rocker arm. In some of these teachings, the mechanical linkage passes through a passage formed in the lash adjuster to provide hydraulic fluid to the rocker arm. In some of these teachings, the mechanical linkage passes through an enclosed interface between the lash adjuster and the rocker arm designed to communicate hydraulic fluid between the lash adjuster and the rocker arm.

[0010] In some of these teachings, the electromechanical actuator includes a solenoid. A solenoid-based actuator can be made very compact. In some others of these teachings, the electromechanical actuator includes a motor. In some of these teachings, the motor is a piezoelectric motor. A motor may allow precision control over the latch pin position.

[0011] In some of these teachings, the electromechanical actuator is operative to push a portion of the mechanical linkage toward the rocker arm on which the latch pin is mounted. In some of these teachings, the electromechanical actuator is operative to draw a portion of the mechanical linkage away from the rocker arm on which the latch pin is mounted. In some of these teachings, the electromechanical actuator is operative to rotate a portion of the

mechanical linkage. Each of these structures has advantages as shown by the examples that follow.

[0012] In some of these teachings, the mechanical linkage includes a sliding interface between a first member and a second member, one of which may be the latch pin itself. In some of these teachings, the electromechanical actuator is operative to extend the first member so that it interferes with the second member causing the latch pin to be displaced. The displacement may cause the latch pin to be moved into or out of the engaging position. The latch pin motion created by extension of the first member may be opposed by a latch pin spring, whereby the spring may restore the latch pin position when the actuator's force on the first member is relaxed or reversed.

[0013] In some of these teachings, the mechanical linkage comprises a cam. In some of these teachings, the mechanical linkage includes a gear. Either a cam or a gear may be part of a mechanism that transmits a translational force in a first direction to produce a translational force in a second direction. In some of these teachings, the mechanical linkage includes a worm gear. The worm gear may convert a rotational motion driven by the electromechanical actuator into a translational motion of the latch pin. A cam may also perform that function. In some of these teachings, the mechanical linkage provides a bell crank. Each of these structures has advantages shown by the examples that follow. In some of these teachings, the mechanical linkage is structured to provide a mechanical advantage that magnifies the latch pin displacement in comparison to movement of the actuator.

[0014] According to some of the present teachings, valvetrain parts designed and put into production for use with a hydraulically actuated rocker arm latch are repurposed for

electromechanical latching. In some of these teachings, the latch pin is installed on a rocker arm designed to hold a hydraulically actuated latch pin. In some of these teachings, the latch pin is installed in place of a hydraulically actuated latch pin. In some of these teachings, the mechanical linkage passes through a port in the rocker arm designed to receive hydraulic fluid. In some of these teachings, the mechanical linkage passes through an enclosed interface between the pivot and the rocker arm. The interface may be operative to contain hydraulic fluid. In some of these teachings, the mechanical linkage passes through a hydraulic port in the pivot. [0015] Some of these teachings provide a method of manufacturing a valvetrain. The method includes manufacturing a rocker arm having a hydraulic chamber and suitable for receiving a hydraulically actuated latch pin, mounting a mechanically actuated latch pin to that rocker arm, and installing a mechanical linkage operative to actuate the latch pin so that the mechanical linkage passes into the hydraulic chamber. In some of these teachings, the method further includes installing an electromechanical actuator inside a dual feed rocker hydraulic lash adjuster and installing a mechanical linkage between that actuator and the latch pin.

[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] Spatially relative terms, such as "beneath," "below," "lower," "above," "upper" and the like are used in the following detailed description to describe spatial relationships as illustrated in the figures. These relationships are independent from the orientation of any illustrated device in actual use.

[0018] Fig. 1A provides a partial cross-sectional side view of an internal combustion engine including a valvetrain in accordance with some aspects of the present teachings.

[0019] Fig. 1 B provides the same view as Fig. 1A, but with the latch pin actuated to a non- engaging position.

[0020] Fig. 1 C provides the same view as Fig. 1A, but with a configuration that results after the cam has risen off base circle.

[0021] Fig. 1 D provides the same view as Fig. 1 B, but with a configuration that results after the cam has risen off base circle.

[0022] Fig. 2A provides a partial cross-sectional side view of an internal combustion engine including a valvetrain in accordance with some aspects of the present teachings.

[0023] Fig. 2B provides the same view as Fig. 2A, but with the latch pin actuated to a non- engaging position.

[0024] Fig. 3A provides a partial cross-sectional side view of an internal combustion engine including a valvetrain in accordance with some aspects of the present teachings.

[0025] Fig. 3B provides the same view as Fig. 3A, but with the latch pin actuated to an engaging position. [0026] Fig. 3C provides the same view as Fig. 3B, but with a configuration that results after the cam has risen off base circle.

[0027] Fig. 4A provides a partial cross-sectional side view of an internal combustion engine including a valvetrain in accordance with some aspects of the present teachings.

[0028] Fig. 4B provides the same view as Fig. 4A, but with the latch pin actuated to a non- engaging position.

[0029] Fig. 4C provides the same view as Fig. 4A, but with a configuration that results after the cam has risen off base circle.

[0030] Fig. 5A provides a partial cross-sectional side view of an internal combustion engine including a valvetrain in accordance with some aspects of the present teachings.

[0031] Fig. 5B provides the same view as Fig. 5A, but with the latch pin actuated to a non- engaging position.

[0032] Fig. 5C provides the same view as Fig. 5A, but with a configuration that results after the cam has risen off base circle.

[0033] Fig. 6A provides a partial cross-sectional side view of an internal combustion engine including a valvetrain in accordance with some aspects of the present teachings.

[0034] Fig. 6B provides the same view as Fig. 6A, but with the latch pin actuated to a non- engaging position and with the upper part of the U-joint rotated 90° relative to its position in the view of Fig. 6A.

[0035] Fig. 6C provides the same view as Fig. 6A, but with a configuration that results after the cam has risen off base circle.

[0036] Fig. 7A provides a partial cross-sectional side view of an internal combustion engine including a valvetrain in accordance with some aspects of the present teachings.

[0037] Fig. 7B provides the same view as Fig. 7A, but with the latch pin actuated to a non- engaging position.

[0038] Fig. 7C provides the same view as Fig. 7A, but with a configuration that results after the cam has risen off base circle.

[0039] Fig. 8 is a flow chart of a method in accordance with some aspects of the present teachings.

Detailed Description

[0040] Figs. 1A-1 D illustrate an internal combustion engine 1 17A having a valvetrain 1 15A in accordance with some aspects of the present teachings. Internal combustion engine 117A may include a cylinder head 103 in which is formed a combustion chamber 101 , a poppet valve 106 having a seat 102 within combustion chamber 101 , and a cam shaft 125 on which is mounted an eccentrically shaped cam 127. Valvetrain 1 15A may include a rocker arm assembly 132 having an inner arm 1 11 A, an outer arm 1 11 B, a pivot 149A providing a fulcrum for outer arm 11 1 B, a cam follower 1 19 mounted to inner arm 11 1 A, and a latch assembly 137A. Cam follower 119 is a roller follower, but could be another type of cam follower such as a slider. Cam follower 1 19 is configured to engage cam 127 as cam shaft 125 rotates.

[0041] Latch assembly 137A includes latch pin 133A mounted to outer arm 1 11 B, an electromechanical actuator 157A mounted to pivot 149A, and a mechanical linkage 144A between latch pin 133A and electromechanical actuator 157A. Latch pin 133A is moveable between an engaging position and a non-engaging position. Figs. 1A and 1C illustrate rocker arm assembly 132 with latch pin 133A in the engaging position. Figs. 1 B and 1 D illustrate rocker arm assembly 132 with latch pin 133A in the non-engaging position.

[0042] Referring to Figs. 1A and 1C, as cam 127 rises off base circle with latch pin 133A in the engaging position, cam follower 1 19 is actuated by cam 127. Inner arm 11 1A may pivot on pivot 149A and rocker arm assembly 132 may transmit force from cam 127 to compress valve spring 105 and lift valve 106 off its seat 102. In the engaging position, latch pin 1 13 engages inner arm 1 11 A and outer arm 11 1 B coupling their motions.

[0043] With latch pin 1 13 in the non-engaging position, the motions of inner arm 11 1A and outer arm 1 11 B may be decoupled. Referring to Figs. 1 B and 1 D, with latch pin 133A is in the non-engaging position, outer arm 1 11 B does not pivot on pivot 149A and may remain stationary even as cam 127 rises off base circle. Rocker arm assembly 132 may transmit force from cam 127 to wind a pair of torsion springs 139, but valve spring 105 is not compressed and valve 106 remains on its seat 102. Torsion springs 139 may be mounted to outer arm 11 1 B and be acted on by axle 123 to which cam follower 1 19 is mounted through bearings 121 , but the relative tuning of torsion springs 139 and valve spring 105 may be such that outer arm 1 11 B remains substantially stationary even as torsion springs 139 are wound by cam 127 rising off base circle and displacing axle 123 downward.

[0044] Pivot 149A may be a hydraulic lash adjuster. Alternatively, pivot 149A may be replaced with another type of lash adjuster or a static pivot. Lash adjustment may be implemented using a hydraulic chamber 168 that is configured to vary in volume as pivot 149A extends or contracts through relative motion of inner sleeve 145 and outer sleeve 147. A supply port 165 may allow a reservoir chamber 166 to fill from an oil gallery 163 in cylinder block 103. The fluid may be engine oil, which may be supplied at a pressure of about 2 atm. When cam 127 is on base circle, this pressure may be sufficient to open check valve 167, admitting oil into hydraulic chamber 168. The oil may fill hydraulic chamber 168, extending pivot 149A until there is no lash between cam 127 and cam follower 1 19. As cam 127 rises off base circle, pivot 149A may be compressed, pressure in hydraulic chamber 168 may rise, and check valve 167 may consequently close. This process allows pivot 149A to extend to reduce or eliminate lash while cam 127 is on base circle and preserves the length of pivot 149A while cam 127 is risen off base circle and applying force to rocker arm assembly 132. [0045] Electromechanical actuator 157A may include a solenoid 159. Mechanical linkage 144A may form a mechanical link between electromechanical actuator 157A and latch pin 133A. Mechanical linkage 144A may include a shaft 143A passing upward through a passage 146A centrally located within pivot 149A and a sliding interface between an angled surface 140 of shaft 143A and an angled surface 134 of latch pin 133A. Shaft 143A may be paramagnetic except for a sleeve 161 or similar structure. Sleeve 161 may be formed of low coercivity ferromagnetic material, such as soft iron. Solenoid 159 may act on mechanical linkage 144A through sleeve 161. When solenoid 159 is energized, it may produce a magnetic field that follows a magnetic circuit that includes sleeve 161. The magnetic circuit may also include a low coercivity ferromagnetic shell 155 around solenoid 159. The magnetic circuit may include outer sleeve 125 if that is formed of low coercivity ferromagnetic material. Raising shaft 143A may move sleeve 161 into a position where it reduces a high magnetic reluctance gap (air gap) 158 in that magnetic circuit. Accordingly, the net of the magnetic forces operating on shaft 143A through sleeve 161 may drive shaft 143A upward.

[0046] As can be seen by comparing Figs. 1A and 1 B, electromechanical actuator 157A is operative to push shaft 143A upward toward outer arm 1 11 B and latch pin 133A so that shaft 143A interferes with latch pin 133A. Shaft 143A and latch pin 133A contact through angled surfaces 134 and 140, whereby the vertical force on shaft 143A results in a horizontal force on latch pin 133A. That force may be operative to drive latch pin 133A from the engaging position to the non-engaging position. A spring 135 mounted to outer arm 1 11 B may be configured to oppose this motion and be compressed by this action. If the upward force on shaft 143A is relaxed, spring 135 may drive latch pin 133A back into the engaging configuration. Spring 135 may also be operative to drive shaft 143A back downward. An independent mechanism, such as another spring, may be configured within pivot 149A to assist in driving shaft 143A back downward.

[0047] Electromechanical actuator 157A may be powered through one or more wires 153. Solenoid 159 or other components of electromechanical actuator 157A may be grounded to the structure of pivot 149A, in which case there may be only one wire 153 providing power. On the other hand, there may be additional wires 153 such as wires to provide ground, feedback signals, or control signals. Wires 153 may pass through a slot 154 formed in outer sleeve 147. Slot 154 may be of sufficient height to allow for the upward and downward motion of inner sleeve 145 relative to outer sleeve 147. Wires 153 may be moved to some extent by the motions of inner sleeve 145, but these motions are far lesser in extent than the motions that could be expected if wires 153 ran to inner arm 111 A or outer arm 1 11 B.

[0048] In an alternative arrangement according to the present teachings, a conductive ring and a contact plate may be mounted, one to inner arm 1 11 A and the other to outer arm 1 11 B. They may be arranged to remain in contact as pivot 149 varies in length to adjust lash. They may also remain in contact as inner sleeve 145 and outer sleeve 147 undergo relative rotation. A wire 153 may connect to the member of this contacting arrangement that is mounted to outer sleeve 1 1 1 B. In some of these teachings, the contact ring (not shown) is mounted to outer sleeve 147 and the connection between wire 153 and the contact ring allows for rotation of pivot 149 in cylinder head 103.

[0049] Electromechanical actuator 157A may be housed within a chamber 162 formed within pivot 149A. Chamber 162 may be sealed against intrusion of engine oil in the

environment surrounding pivot 149A. Small particles of metal may be suspended in that oil. These particles could be attracted by and possibly interfere with the operation of solenoid 159 or other parts of electromechanical actuator 157A that become magnetized. A plug 151 may seal the aperture through which wires 153 enter the chamber 162. Mechanical linkage 144A may exit pivot 149A and enter outer arm 11 1 B through an enclosed interface 142 formed by continuous contact between pivot 149A and outer arm 1 1 1 B. Because interface 142 is enclosed, chamber 157A may communicate with the interior of outer arm 11 1 B while still being sealed from the surrounding environment.

[0050] Rocker arm assembly 132 may be made with parts of a rocker arm assembly designed to operate with a hydraulically actuated latch. These parts may have been

repurposed for electromechanical latching. For example, outer arm 11 1 B may have been designed to hold a hydraulically actuated latch pin. In some of these teachings, the latch pin is installed in place of a hydraulically actuated latch pin. The chamber 136 which houses latch pin 133A may have been designed to hold hydraulic fluid to actuate a hydraulically actuated latch pin in the place of latch pin 133A. The port 141 through which shaft 143A of mechanical linkage 144A enters outer arm 111 B may have been designed as a passage for hydraulic fluid. The part of rocker arm 1 11 B that forms interface 142 with pivot 149A may have been designed to form a hydraulic seal that is maintained even as outer arm 11 1 B pivots on pivot 149A.

[0051] Likewise, pivot 149A may include parts that were originally designed to supply hydraulic fluid to a rocker arm 1 11 pivoting on pivot 149A. The upper part of pivot 149A may be shaped to form a hydraulic seal along interface 142. The passage 146 through which mechanical linkage 144A passes upward through and out of pivot 149A may have been designed as a passage for hydraulic fluid. The chamber 162 that houses electromechanical actuator 157A may have been designed as a reservoir for hydraulic fluid. The part designs may have previously been in production and used in accordance with the intent of those designs. The equipment used in that production may be used again to provide parts for valvetrains according to the present teachings.

[0052] Fig. 8 provides a flow chart of a method 200 that may be used to manufacture a rocker arm assembly 132 or another rocker arm assembly in accordance with the present teachings. Many of the steps in method 200 are optional and their order is optional to the extent consistent with the logic of the method. For example, in method 200, parts of pivot 149A are adapted from parts originally designed to from a hydraulic lash adjuster that supplies hydraulic fluid to a rocker arm. But method 200 may be adapted to use a hydraulic lash adjuster originally designed for electromechanical latching, with just the rocker arm 1 11 B having been repurposed from a hydraulic latching application. Rocker arms for commercial applications are typically manufactured using customized casting and stamping equipment requiring a large capital investment. Being able to repurpose even one cast and stamp part of a rocker arm assembly from a prior application can result in substantial savings.

[0053] Method 200 begins with act 201 , a design operation in which a rocker arm assembly including a hydraulically actuated latch may be designed in detail. The design may be made without specifications for electromechanical actuator 157A or mechanical linkage 144A. Method 200 continues with act 203, building casting and stamping equipment sufficient for implementing the design of act 201. Act 205 is using a first portion of that equipment to manufacture an outer arm 11 1 B having a chamber 136. Act 207 is using an additional portion of that equipment to manufacture parts of a hydraulic lash adjuster adapted to supply hydraulic fluid to the outer arm 11 1 B. Act 209 is installing a mechanically actuated latch pin 133A or the like within the chamber 136. This and similar acts may include machining operations to complete the adaptation of parts. Act 211 is installing electromechanical actuator 157A within a pivot 149A made using parts manufactured with act 207. Act 213 is installing a mechanical linkage 144A or the like between electromechanical actuator 157A and latch pin 133A. The resulting rocker arm assembly 132 may be installed in a valvetrain 115A, which in turn becomes part of an internal combustion engine 1 17A.

[0054] Rocker arm assembly 132 and other examples herein illustrate cylinder deactivating rocker arms. The present teachings are also applicable to switching rocker arms, but cylinder deactivating rocker arms such as rocker arm assembly 132 may simplify implementation of some aspects of the present teachings. In rocker arm assembly 132, rocker arm 11 1 B to which latch pin 133A is mounted becomes decoupled from actuation of cam follower 119 and ceases to undergo pivotal motion when latch pin 133A is in the non-engaging position. As a result, mechanical linkage 144A does not require any provision to allow rocker arm 1 11 B to pivot while mechanical linkage 144A is holding latch pin 133A in the non-engaging position. Such a provision might include a joint in shaft 143A similar to joints shown in some of the other examples provided herein.

[0055] Figs. 2A-2B illustrate an internal combustion engine 1 17B having a valvetrain 1 15B in accordance with some aspects of the present teachings. Internal combustion engine 117B may be similar to internal combustion engine 1 17A. Valvetrain 115A may be similar to valvetrain 1 15B, although it include a different latch assembly, latch assembly 137B. Latch assembly 137B is generally similar to latch assembly 137A, but includes a mechanical linkage 144B rather than mechanical linkage 144A. Mechanical linkage 144B has a rounded surface 138 on the tip of shaft 143B which differs from the flattened surface 140 of mechanical linage 144A.

[0056] Fig. 2A shows the default state of rocker arm assembly 132 that may be expected to develop when power to actuator 157A is off. Fig. 2B shows the state that may be expected to develop after power to actuator 157A has been turned on. As shown by comparison between these two figures, rounded surface 138 forms a sliding interface with angled surface 134 of latch pin 133B through which vertical force on shaft 143B may be redirected to provide a horizontal force on latch pin 133B. While the angled surface 134 of shaft 143A allows force from actuator 157A to be spread over a wide area, rounded surface 138 may advantageously avoid problems of alignment.

[0057] Figs. 3A-3C illustrate an internal combustion engine 1 17C in including a valvetrain 115C in accordance with some other aspects of the present teachings. Internal combustion engine 117C is similar to internal combustion engine 1 17B. Valvetrain 1 15C is similar to valvetrain 1 15B, includes a pivot 149C similar to pivot 149B, and includes a latch assembly 137C. Latch assembly 137C differs from latch assembly 137B in that it contains a spring 135C that is mounted to outer arm 11 1 B and is configured to pull latch pin 133C into a non-engaging position shown in Fig. 3A. In this system, the non-engaging position is the default position expected to result when actuator 157A is shut off.

[0058] Latch assembly 137C includes a mechanical linkage 144C. Mechanical linkage 144C includes an upper shaft 171. As shown in Fig. 3B, turning actuator 157A on may drive shaft 171 upward. A rounded upper surface 138 of shaft 171 abuts sloped surface 134 of latch pin 133C, whereby the upward force on shaft 171 may force spring 135C to extend and drive latch pin 133C into an engaging configuration.

[0059] Mechanical linkage 144C includes a lower shaft 175 connected to upper shaft 171 through a joint that includes an axle 173. As shown in Fig. 3C, upper shaft 171 may pivot relative to lower shaft 175 on axle 173, allowing upper shaft 171 to move in unison with outer arm 11 1 B and maintain latch pin 133C in the engaging position while cam 127 rises off base circle to lift valve 106 off its seat 102.

[0060] Figs. 4A-4C illustrate an internal combustion engine 117D including a valvetrain 117D in accordance with some other aspects of the present teachings. Internal combustion engine 117D is similar to internal combustion engine 1 17C. Valvetrain 115D is similar to valvetrain 1 15C, includes a pivot 149D similar to pivot 149C, and includes a latch assembly 137D. Latch assembly 137D differs from latch assembly 137C in the form of mechanical linkage 144D, actuator 157D, and the way on which they interact with latch pin 133D to move it between engaging and non-engaging positions. [0061] Mechanical linkage 144D includes a lower shaft 175D, an upper shaft 171 D, and a cam 174. Upper shaft 171 D is positioned to interfere with cam 176 whereby upward motion of shaft 171 D drives rotation of cam 176. Upper shaft 171 D may also interfere with cam 176 whereby downward motion of shaft 171 D drives a counter-rotation of cam 176. These interferences may be created by gear teeth 179 on cam 174 intermeshing with gear teeth 180 on upper shaft 171 D.

[0062] If cam 176 is driven to rotate in a clockwise direction, it may act against surface 177 of latch pin 133D, driving latch pin 133D from the engaging configuration shown in Fig. 4A to the non-engaging configuration shown in Fig. 4B. If cam 176 is driven to rotate in the anti-clockwise direction, it may act against surface 174 of latch pin 133D and drive latch pin 133D into the non- engaging configuration. If, as in this example, latch pin 133D can be driven into either the engaging or the non-engaging position through mechanical linkage 144D, an independent mechanism for driving latch pin 133D such as a spring configured to bias latch pin 133D in one or the other direction may be absent.

[0063] Lower shaft 175D and upper shaft 171 D are pivotally connected through an axle 173. This linkage maintains the required stiffness in linkage 144D while allowing relative bending between lower shaft 175D and upper shaft 171 D. As shown in Fig. 4C, such relative bending may be desirable if a mechanical connection between actuator 157D and latch pin 133D is to be maintained while outer arm 11 1 B pivots on pivot 149D.

[0064] Electromechanical actuator 157D may be capable of applying either an upward or a downward force to lower shaft 144D. A variety of different actuators may be suitable for this purpose. One type of actuator that may be suitable includes a solenoid and spring. In some aspects of the present teachings, electromechanical actuator 157D includes a motor 160 as shown schematically in Figs. 4A-4C.

[0065] In some of these teachings, motor 160 is a servomotor. A servomotor is a motor that may be operative to actuate to a particular position in response to a command to move to that position. In some of these teachings, the action of motor 160 is disabled during a period when cam 127 or another cam may be applying substantial force to rocker arm assembly 132. A servomotor may lend itself to rapidly changing the position of latch pin 133D.

[0066] In some of these teachings, motor 160 is a stepper motor. A stepper motor may be operative to move one or a whole number of unit distances (steps) in response to commands. A stepper motor may provide a high degree of positional stability and may simplify control. A stepper motor may also have a low sensitivity to variations in its power supply. According to some aspects of the present teachings, actuator 157D includes a motor 160 of a type that can maintain its position under load without power. For example, motor 160 may be a SQUIGGLE® motor. This property may increase the reliability with which latch 133D is repositioned. [0067] In some of these teachings, motor 160 is electromagnetic motor. In some of these teachings, motor 160 is a piezoelectric motor. A piezoelectric motor may be a SQUIGGLE® motor. In some of these teachings, motor 160 is a stepping piezo actuator. In some of the teachings, motor 160 is an amplified piezo actuator. A piezoelectric actuator may lend itself to a simple, reliable, and compact construction suitable for placement within pivot 149D.

[0068] Figs. 5A-5C illustrate an internal combustion engine 1 17E including a valvetrain 117E in accordance with some other aspects of the present teachings. Internal combustion engine 117E is similar to internal combustion engine 1 17D. Valvetrain 1 15E is similar to valvetrain 1 15D, includes a pivot 149E similar to pivot 149D, and includes a latch assembly 137E. Latch assembly 137E differs from latch assembly 137D in the form of mechanical linkage 144E.

[0069] Mechanical linkage 144E includes a lower shaft 175D, an upper shaft 171 D, and, a gear 183. Gear 183 rotates on an axle 178 that may be mounted to outer arm 11 1 B and include teeth 182 that intermesh with teeth 181 of latch pin 133E and teeth 180 of shaft 171 D. Upward motion of shaft 171 D may drive rotation of gear 183 which in turn produces lateral movement of latch pin 133E. Gear 183, cam 174, or another suitable mechanism may be configured within mechanical linkage 144E to provide a mechanical advantage between lower shaft 175D and latch pin 133E whereby an upward or downward movement of lower shaft 175D driven by motor 160 may provide a lateral movement of latch pin 133E that is of greater magnitude. This may be particularly useful if motor 160 is a piezoelectric motor, but in any case may increase the speed with which electromechanical actuator 157D is able to actuate latch pin 133E between engaging and non-engaging configurations.

[0070] Figs. 6A-6C illustrate an internal combustion engine 1 17F including a valvetrain 117F in accordance with some other aspects of the present teachings. Internal combustion engine 117F is similar to internal combustion engine 117E. Valvetrain 1 15F is similar to valvetrain 1 15E, includes a pivot 149F similar to pivot 149E, and includes a latch assembly 137F. Latch assembly 137F differs from latch assembly 137E in the form of mechanical linkage 144F.

[0071] Mechanical linkage 144F includes a lower shaft 175F connected to an upper shaft 171 F through a universal joint 172. Electromechanical actuator 157F includes a motor 160F configured to rotate lower shaft 175F. Rotational motion of upper shaft 171 F may be coupled to rotational motion of lower shaft 175F through universal joint 172. Moreover, as shown in Fig. 6C, this coupling of rotational motions may continue even as upper shaft 171 F becomes canted relative to lower shaft 175F due to pivoting of outer arm 11 1 B on pivot 149F. Upper shaft 171 F may include helical teeth 180F that mesh with teeth 182 on gear 183, whereby mechanical linkage 144F includes a worm gear and rotation of upper shaft 171 F about its axis may result in rotation of gear 183 on axle 178 and actuation of latch pin 133E into and out of the non- engaging position shown in Fig. 6B. Motor 160F may be of any suitable type for rotating lower shaft 175F.

[0072] Figs. 7A-7C illustrate an internal combustion engine 1 17G including a valvetrain 117G in accordance with some other aspects of the present teachings. Internal combustion engine 117G is similar to internal combustion engine 117F. Valvetrain 1 15G is similar to valvetrain 1 15F, includes a pivot 149G similar to pivot 149F, and includes a latch assembly 137G. Latch assembly 137G differs from latch assembly 137F in the form of mechanical linkage 144G and the configuration of electromechanical actuator 157G.

[0073] Mechanical linkage 144G includes a bell crank 185. Bell crank 185 may include a first cable 186A connecting to latch pin 133G and a second cable 186B connecting to a vertical shaft 143G. Vertical shaft 143G may be configured to slide up and down within pivot 149G. Electromechanical actuator 157G includes a solenoid 159 having an air gap 158.

Electromechanical actuator 157G may be configured such that air gap 158 is reduced by downward movement of shaft 143G. Shaft 143G may be formed entirely of low coercivity ferromagnetic material or may have just a portion at its bottom, such as a sleeve 161 , that includes low coercivity ferromagnetic material, such as soft iron.

[0074] As shown in Fig. 7B, pulling shaft 143G downward may pull latch pin 133G out of its engaging position. Latch spring 135 may return latch pin 133G to the engaging configuration when solenoid 159 loses power. Alternatively, rocker arm assembly 149G could be configured so that latch spring 135 maintains the non-engaging position and downward movement of shaft 143G pulls latch pin 133G into its engaging configuration. As shown in Fig. 7C, bell crank 185 allows actuator 157A to maintain tension on latch pin 133G even as latch pin 133G moves in conjunction with pivoting of outer arm 1 11 B on pivot 149G. Bell crank 185 may be structured to provide a mechanical advantage for the action of actuator 157A on latch pin 133G.

[0075] 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.

Claims

The claims are:

1. A valvetrain for an internal combustion engine of a type that has a combustion chamber, a moveable valve having a seat formed in the combustion chamber, and a camshaft, the valvetrain comprising:

a rocker arm assembly comprising a rocker arm and a cam follower configured to engage a cam mounted on a camshaft as the camshaft rotates;

a pivot providing a fulcrum for the rocker arm; and

a latch assembly comprising a latch pin that is mounted on the rocker arm, an electromechanical actuator that is mounted to the pivot, and a mechanical linkage between the latch pin and the electromechanical actuator;

wherein the electromechanical actuator is operable to actuate the latch pin between a first position and a second position through the mechanical linkage.

2. A valvetrain according to claim 1 , wherein the mechanical linkage extends from the pivot to the rocker arm.

3. A valvetrain according to claim 1 , wherein the mechanical linkage extends from within the pivot to the rocker arm.

4. A valvetrain according to claim 1 , wherein the mechanical linkage passes through an enclosed interface between the pivot and the rocker arm.

5. A valvetrain according to claim 1 , wherein the electromechanical actuator is mounted to a side of the pivot.

6. A valvetrain according to any one of claims 1 to 5, wherein the electromechanical actuator is contained within the pivot.

7. A valvetrain according to any one of claims 1 to 6, wherein:

the rocker arm assembly is operative to form a force transmission pathway between a camshaft-mounted cam and a moveable valve; and

the force transmission pathway includes the rocker arm.

8. A valvetrain according to any one of claims 1 to 6, wherein:

one of the first and second latch pin positions provides a configuration in which the rocker arm assembly is operative to actuate a moveable valve in response to rotation of a camshaft to produce a first valve lift profile; and the other of the first and second latch pin positions 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

9. A valvetrain according to any one of claims 1 to 6, wherein the rocker arm assembly is configured such that when the latch pin is in the second position, the motion of the rocker arm is decoupled from motion of the rocker arm assembly induced by a cam displacing the cam follower.

10. A valvetrain according to any one of claims 1 to 6, wherein the rocker arm assembly further comprises a spring mounted to the rocker arm and configured to bias the latch pin toward one of the first and second positions.

11. A valvetrain according to any one of claims 1 to 10, wherein the pivot is a lash adjuster.

12. A valvetrain according to claim 11 , wherein the pivot is a hydraulic lash adjuster.

13. A valvetrain according to any one of claims 1 to 10, wherein the mechanical linkage passes through a hydraulic port formed in the rocker arm to which the latch pin is mounted.

14. A valvetrain according to any one of claims 1 to 10, wherein the mechanical linkage passes through a hydraulic port formed in the pivot.

15. A valvetrain according to any one of claims 1 to 14, wherein the

electromechanical actuator comprises a solenoid.

16. A valvetrain according to any one of claims 1 to 14, wherein the

electromechanical actuator comprises a motor.

17. A valvetrain according to any one of claims 1 to 16, wherein:

the actuator is configured to apply a first force on a first member of the mechanical linkage;

the mechanical linkage is operable to transmit part of the first force to produce a second force; and that first and second forces have distinct directions.

18. A valvetrain according to any one of claims 1 to 16, wherein the actuator is configured to rotate a first member of the mechanical linkage.

19. A valvetrain according to any one of claims 1 to 16, wherein:

the actuator is configured to apply a rotational force to a first member of the mechanical linkage; and

the mechanical linkage is operable to transmit part of the rotational force of the first member to a translational force on the latch pin.

20. A valvetrain according to any one of claims 1 to 16, wherein the mechanical linkage comprises a sliding interface between a first member and a second member.

21. A valvetrain according to any one of claims 1 to 16, wherein the

electromechanical actuator is operative to extend a first member of the mechanical linkage so that it interferes with a second member causing the latch pin to be displaced.

22. A valvetrain according to any one of claims 1 to 16, wherein the mechanical linkage comprises a cam.

23. A valvetrain according to any one of claims 1 to 16, wherein the mechanical linkage comprises a gear.

24. A valvetrain according to any one of claims 1 to 16, wherein the mechanical linkage comprises a bell crank.

25. An internal combustion engine comprising:

a combustion chamber;

a moveable valve having a seat formed in the combustion chamber;

a camshaft; and

a valvetrain according to any one of claims 1 to 17.

26. A method of manufacturing a valvetrain according to any one of claims 1 to 17, the method comprising:

manufacturing a rocker arm comprising a hydraulic chamber and suitable for receiving a hydraulically actuated latch; mounting a mechanically actuated latch pin to that rocker arm;

mounting an electromechanical actuator to a pivot for the rocker arm; and installing and a mechanical linkage between the latch pin and the electromechanical actuator.

27. A method of manufacturing a valvetrain according to claim 26, wherein the mechanical linkage passes through a port in the rocker arm connecting to the hydraulic chamber.