Engine valve actuation systems with lost motion valve train components, including collapsing valve bridges with locking pins

Systems for valve actuation in internal combustion engines provide configurations for collapsing valve train components, particularly collapsing valve bridges. Various configurations for locking a bridge piston to a bridge housing include substantially cylindrical locking pins that may be housed within a substantially cylindrical receptacles defined by a transverse bore in the bridge piston and actuated hydraulically and may include an actuating pin that interacts with the locking pins to synchronize motion and provide positive positioning within an annular recess in the bridge housing to lock or unlock the bridge piston for movement relative to the bridge housing. Various geometries for locking pins and actuating pins provide benefits of manufacturing, ease of assembly, alignment and reduced wear.

FIELD

The instant disclosure relates generally to systems for actuating one or more engine valves in an internal combustion engine. In particular, embodiments of the instant disclosure relate to systems and methods for valve actuation using a lost motion system in the form of a collapsing valve train component, such as a collapsing valve bridge.

BACKGROUND

As known in the art, engine valve actuation is required in order to operate an internal combustion engine in a positive power generation mode. Further, auxiliary valve actuation motions (as opposed to “main” valve actuation motions used to operate in positive power generation mode) are known in the art that allow an internal combustion engine to operate in variations of positive power generation mode (e.g., exhaust gas recirculation (EGR)) or in other modes of operation, such as engine braking in which the internal combustion engine is operated essentially as an air compressor to develop retarding power to assist in slowing down the vehicle. Further still, variants in valve actuation motions used to provide engine braking are known (e.g., brake gas recirculation (BGR), bleeder braking, etc.)

To facilitate operation of an internal combustion engine in either positive power or engine braking modes, the use of lost motion components is also known in the art. Such lost motion components typically alter their length or engage/disengage adjacent components within a valve train to permit certain potentially-conflicting valve actuation motions, which are otherwise dictated by fixed-profile valve actuation motion sources such as rotating cams, to be “lost,” i.e., not conveyed via the valve train. A particular type of lost motion component known in the art are so-called collapsing (or, alternatively, locking) valve bridges. Examples of such components are taught in U.S. Pat. Nos. 8,936,006, 9,790,824 and European Patent No. 2975230. The subject matter of all of these documents is incorporated herein by reference. In these devices, locking elements are provided that permit a sliding plunger or similar element, disposed within a housing (such as within a centrally-located bore of a valve bridge), to be selectively unlocked (in which case the plunger is free to slide within the bore thereby permitting valve actuation motions applied to the plunger to be lost) or locked (in which case the plunger is maintained in a fixed position relative to the valve bridge thereby permitting valve actuation motions to be conveyed through the plunger to the housing).

While collapsing or locking valve bridges (or other valve train components) operate well for their intended purpose, various improvements thereto would be a welcome addition in the art. More specifically, improvements providing ease of assembly, lower manufacturing cost and more dependable and durable operation of collapsing valve train components, such as collapsing valve bridges, would contribute to the state of the art. It would therefore be advantageous to provide systems that address the aforementioned shortcoming and others in the prior art.

SUMMARY

Responsive to the foregoing challenges, the instant disclosure provides various embodiments of valve actuation systems with features for facilitating locking and unlocking of a collapsing valve train components, such as a valve bridge.

According to aspects of the disclosure, a device for controlling motion applied to the one or more engine valves comprises a housing disposed within the valve train, the housing including a housing bore and at least one housing locking surface, a piston disposed within the housing bore, the piston having a piston bore and at least one locking pin receptacle defined therein, the at least one locking pin receptacle having a cylindrical shape, a locking assembly for selectively locking the piston to the housing, the locking assembly comprising an actuator pin supported for movement within the piston bore and at least one respective locking pin disposed in the at least one locking pin receptacle, the actuator pin including an outer locking pin engagement surface adapted to support the at least one locking pin in an extended position, and an inner locking pin support surface adapted to support the at least one locking pin in a retracted position, whereby movement of the actuator pin causes the at least one locking pin to selectively engage or disengage the housing locking surface thereby selectively locking or unlocking the piston relative to the housing.

According to one example implementation, a valve actuation system may include a collapsing valve bridge including a housing having a housing bore or cavity. A bridge piston is disposed in the housing bore and a locking assembly is disposed in the bridge piston for selectively locking and unlocking the piston for movement relative to the housing. A transverse bore, which may be generally cylindrical in shape and thus easily machined, may extend within the bridge piston and defines receptacles for locking pins of the locking assembly. A locking pin extension spring provides a biasing force on the locking pins tending to force the locking pins in a radially outward direction. Inward travel of the locking pins is limited by an inward travel limiting component, which may be a locking pin inner limit snap ring disposed centrally within the transverse bore. Outward travel of the locking pins may be limited by an outward travel limiting component, which may be in the form of a locking pin outer limit snap ring. The locking pins may include an undercut face on a radially outer surface, which may engage the outer limit snap ring. The undercut face may define a conical surface that engages a corresponding surface in an annular recess of the housing to ensure thorough engagement and load distribution when the piston is locked to the housing. Owing to the cylindrical shape, the locking pins may undergo some degree of rotation within their housings to facilitate alignment. The outer limit snap ring facilitates quick and easy installation of the locking assembly in the bridge piston and prevents significant rotation of the locking pins within the locking pin receptacles. The locking pins may be selectively actuated by control of hydraulic fluid provided through a piston fluid passage in the bridge piston which is in fluid communication with an annular channel formed in the housing bore. When pressurized hydraulic fluid is provided to the piston fluid passage and annular channel an inward force will be presented on radially-outermost surface of the locking pins and force them into a retracted position within the locking pin receptacles, thereby unlocking the bridge piston relative to the housing.

According to another example implementation, a bridge piston includes an actuation pin, which interacts with locking pins to provide synchronized motion and positive positioning thereof in locking and unlocking operations of a valve bridge piston within a valve bridge housing. The housing includes an internal bore in which is positioned a bridge piston for sliding movement relative thereto. Locking pins may be disposed in a transverse cylindrical bore extending through the piston. The piston includes an actuator pin bore for slidably receiving the actuator pin. Hydraulic fluid is conveyed through a fluid passage in a bridge piston cap to an upper surface of the actuator pin to cause downward movement thereof. A return spring returns the actuator pin to an upper indexed position in the absence of fluid pressure. The actuator pin includes an outer locking pin engagement surface for supporting the locking pins in an extended or deployed position in which they engage an annular recess in the bridge housing. The actuator pin also includes an inner locking pin engagement surface for supporting the locking pins in a retracted position. At least one transition surface on the actuating pin may be conical in shape and may extend from the outer locking pin engagement surface to the inner locking pin engagement surface. The locking pins may include an actuating pin interface with alignment surfaces for engaging the actuator pin and for aligning and preventing rotation of the locking pins in the deployed position, in the retracted position and during movement between the deployed and retracted positions. The alignment surfaces may include one or more conical chamfers on the locking pins adapted to cooperate with the transition surface(s) as the locking pin moves inward toward the actuation pin and to ultimately engage the transition surface of the actuating pin to provide for stable support of the locking pin in the retracted position. One or more conical surfaces on a housing interface of the locking pins may engage corresponding surfaces in an annular recess of the housing to ensure thorough engagement and load distribution when the piston is locked to the housing.

According to yet another example implementation, collapsing valve bridge locking pins comprise an actuation pin interface having a first concave surface for engaging the actuator pin outer locking pin engagement surface and a pair of conical chamfered surfaces for engaging respective transition surfaces on the actuator pin. A housing interface on the locking pins includes an outer convex surface and pair of opposed, symmetrical conical convex surfaces on top and bottom portions of the locking pins for providing effective engagement with one or more correspondingly shaped conical surfaces on an annular recess of the housing.

According to yet another example implementation, collapsing valve bridge locking pins may comprise an actuation pin interface having a first concave surface for engaging the actuator pin outer locking pin engagement surface and a single conical chamfered surface on an upper portion of the locking pin for engaging a transition surface on the actuation pin. A housing interface on the locking pins includes an outer convex surface and a single conical convex surface on a top portion of the locking pin.

According to yet another example implementation, collapsing valve bridge locking pins may comprise an actuation pin interface having a first concave surface for engaging the actuator pin outer locking pin engagement surface and a two, opposed, asymmetrical, conical chamfered surfaces on an upper and lower portion of the locking pin for engaging respective transition surface on the actuation pin. The asymmetrical conical chamfered surfaces prevent the locking pin from properly seating against the actuation pin inner locking pin engagement surface when the locking pin is upside down or improperly oriented, thus preventing improper assembly of the locking pin in the piston transverse bore. A housing interface on the locking pins includes an outer convex surface and an undercut portion forming a conical surface for engaging a correspondingly shaped conical surface on the piston bore annular recess. The undercut housing interface on the locking pin provides advantageous alignment and load distribution relative to the piston bore annular recess.

Other aspects and advantages of the disclosure will be apparent to those of ordinary skill from the detailed description that follows and the above aspects should not be viewed as exhaustive or limiting. The foregoing general description and the following detailed description are intended to provide examples of the inventive aspects of this disclosure and should in no way be construed as limiting or restrictive of the scope defined in the appended claims.

DETAILED DESCRIPTION

FIG. 1is a pictorial illustration of a valve actuation system100, including a valvetrain with a lost motion device in the form of a collapsing valve bridge200. The system may include a rocker arm110, which may receive valve actuation motions from a suitable valve actuation motion source, such as a cam120. As is known, the rocker arm may be supported for pivoting movement on a rocker shaft130, which may include one or more hydraulic fluid passages132extending therein for supplying hydraulic fluid to the rocker arm. A cam roller112may be disposed at a cam roller end114of the rocker110and may interact with the surface of the cam120to convey the motion of the cam surface to the rocker110. A biasing mechanism140, which may include a spring142acting against a rocker arm ledge or extension144and secured to a stationary mount146affixed to the engine block or head, may bias the rocker110toward the motion source120and maintain the cam roller112in contact with the cam.

As illustrated schematically inFIG. 1, one or more hydraulic fluid delivery channels118may extend within the interior of the rocker110to deliver hydraulic fluid from the rocker shaft hydraulic passage132to a valve bridge end119of the rocker110. The hydraulic fluid may pass from the delivery channel118through additional components in the valve train, such as a swivel foot150, having an internal passage152, and further to internal working components of the valve bridge, as will be detailed herein. Opposing valve-engaging ends202and204of the valve bridge200may engage respective engine valves160and170, or other components, such as bridge pins, that ultimately control motion of the engine valves. Each valve160,170may include a valve spring162,172to bias the valve in a closed position and may provide a biasing force on the valve bridge tending to move the valve bridge in an upward direction, and thus also providing a biasing force tending to keep the cam roller112against the cam120, as is known in the art. Valves160,170may be guided within valve guides164,174, which may be supported on and fixed to the engine cylinder head or engine block.

FIGS. 2 and 3illustrate components of a first example collapsing valve bridge200according to aspects of the disclosure.FIG. 2is an assembled cross-section view andFIG. 3is an exploded perspective view of the valve bridge components. The collapsing valve bridge200may include a housing210having a housing bore or cavity212defined in a central portion thereof. Opposing valve-engaging ends202and204of the housing210may extend from the central portion. A bridge piston or plunger240may be disposed in the housing bore212and may include an upper portion242having a valve train engaging interface244for engaging a valve train component, such as swivel foot150(FIG. 1). Bridge piston240may also include a lower portion246having a spring seat248defined therein for engaging a piston return spring250, an opposite end of which may be seated against a bottom wall214of the housing bore212.

According to aspects of the disclosure, a locking assembly260may be disposed in the bridge piston240for selectively locking and unlocking the piston240for movement relative to the housing210. A transverse or radially-extending bore241, which may be generally cylindrical in shape and thus easily formed, may extend within the bridge piston240and thus may provide respective, axially aligned locking pin housings or receptacles. Locking assembly260may include a pair of opposed locking pins262disposed in the transverse bore241. A locking pin extension spring264may be provided in the transverse bore241between the two locking pins262and may provide a biasing force on the locking pins tending to force the locking pins in a deployed or locking direction radially outward from the axis or center of the bridge piston240. Each locking pin262may include a recessed spring seat261formed on an inner surface thereof to engage the spring264. Inward travel of the locking pins262may be limited by an inward travel limiting component, which may be in the form of a locking pin inner limit snap ring266disposed centrally within the transverse bore. Locking pin inner limit snap ring266may thus also serve to minimize any potential for one of the locking pins262to be fully retracted while the other locking pin is only partially retracted.

Outward travel of locking pins262may be limited by an outward travel limiting component, which may be in the form of a locking pin outer limit snap ring270disposed in a retaining groove243and having an outer diameter that substantially matches that of the bridge piston. As will be recognized, locking pins262may include an undercut face263on an outer surface thereof, which, in addition to providing advantages in engaging and locking the bridge piston to the housing210, as will be detailed further herein, may engage the outer limit snap ring270when installed in groove243to define an outer travel limit of the locking pins262. As will be recognized, outer limit snap ring270facilitates easy assembly of the locking pins262within the bridge piston240. The inner limit snap ring266, spring264and locking pins262may be installed in transverse bore241and held in a retracted position manually or with manufacturing equipment while the outer limit snap ring270may be fit onto the bridge piston240and positioned into groove243. The outer limit snap ring270facilitates quick and easy installation of the locking assembly260in the bridge piston240and also serves as a locking pin travel limiting component to provide an outer limit on the travel of the locking pins262. Still further, the outer limit snap ring prevents significant rotation of the locking pins262within the locking pin receptacles241and thus operate to maintain the locking pins262in a proper orientation.

Locking pins262may be selectively actuated by control of hydraulic fluid provided to the collapsing piston bridge200. A piston fluid passage245may be provided in the bridge piston240and may receive hydraulic fluid via a hydraulic fluid source and passages in the valve train, such as the passage152in the swivel foot150(FIG. 1), which in turn is fed hydraulic fluid via the rocker delivery passage118(FIG. 1). As best seen inFIG. 3, an upper section of piston fluid passage245may extend axially within the piston240and a lower portion of piston fluid passage245may extend radially outward to an outlet247.

When the piston is installed in the piston bore212, outlet247may be in fluid communication with an annular channel216formed within the lateral surface of the piston bore212. Locking pins may be controlled through application of pressurized hydraulic fluid in the piston fluid passage and annular channel216. When pressurized hydraulic fluid is provided to the piston fluid passage245and annular channel216, for example, by way of a control solenoid, as is generally known in the art, controlling fluid in the hydraulic passages in the valve train, an inward force will be presented on radially-outermost surface of the locking pins262and will be sufficient to overcome the bias of the locking pin extension spring264. Consequently, the locking pins262will be forced into a retracted position within the locking pin receptacles241and out of contact with the annular channel216, thereby unlocking the bridge piston240relative to the housing210and permitting the piston240to move within the housing bore212, with the corresponding loss of motion in the valve train. Piston240may include a piston vent passage249, which may vent hydraulic fluid from within the transverse bore241to the bottom of the housing bore212. A housing vent passage218permits vented hydraulic fluid to exit the bottom of the housing210. This arrangement prevents the buildup of hydraulic fluid in the transverse bore241behind (i.e., on the radially inward surfaces of) the locking pins262.

As will be recognized from the instant disclosure, when the piston fluid passage245is not charged with pressurized hydraulic fluid, for example, when the control solenoid valve shuts off the flow of hydraulic fluid, bias of the piston return spring250may cause the bridge piston240to index upward within the housing bore212until the transverse bore241registers with the annular channel. At that point, the bias of the locking pin extension spring264is sufficient to cause the locking pins262to extend into the annular channel216, thereby locking the bridge piston240relative to the housing210.

As can best be seen inFIG. 2, the undercut face263of the locking pins262may provide for alignment of the locking pins262with the annular channel216as the locking pins262move into the deployed position. In addition, the upper extending portion of the locking pins262may have a dimension that permits sufficient clearance with an upper surface of the annular channel216in order to prevent binding when the locking pins262move to the deployed position. As will be recognized, the cylindrical shape of the locking pins262may permit rotational movement of the locking pins262within the correspondingly-shaped locking pin receptacles241. On the other hand, some limit on the extent of rotation of the locking pins262within the locking pin receptacles may be provided by the outer limit snap ring270. Thus, in accordance with aspects of the disclosure, the locking pins262are permitted sufficient rotation to facilitate self-alignment with the annular channel216, but not such a degree of rotation that would result in misalignment or interference of movement of the locking pins262as they move to a deployed position.

FIGS. 4, 5.1 and 5.2illustrate an alternative embodiment of a collapsing bridge400according to aspects of the disclosure. According to these aspects, positive positioning and synchronized motion of locking pins462is facilitated by an actuation pin480disposed within the piston440. The collapsing bridge may include a housing410, which in this case is in the form of a valve bridge, having an internal housing bore or cavity412defined in a central portion thereof and including an annular recess416extending into a surface of the housing bore412. Opposing valve-engaging ends402and404of the housing210may extend from the central portion. A bridge piston or plunger440may be disposed in the housing bore412and may include an upper portion442. A bridge piston cap490may include a valve train engaging interface494for engaging a valve train component, such as swivel foot150(FIG. 1) and a bridge piston cap fluid passage496extending through the bridge piston cap490. A reduced diameter bridge piston cap plug498may fit within a bridge piston cap plug receiving bore444on the bridge piston. Bridge piston440may also include a lower portion446having a spring seat448defined thereon for engaging a piston return spring450, an opposite end of which may be seated against a bottom wall414of the housing bore412. Piston return spring450applies a biasing force to piston440tending to move the piston440in an upward direction. A housing vent418permits the flow of hydraulic fluid from the housing bore412.

According to aspects of the disclosure, a locking assembly460may be disposed in the bridge piston440for selectively locking and unlocking the piston440for movement relative to the housing410. A transverse or radially-extending bore441, which may be generally cylindrical in shape and thus easily formed, may extend within the bridge piston440and thus may provide respective, axially aligned locking pin housings or receptacles. Locking assembly460may include a pair of opposed locking pins462disposed in the respective locking pin receptacles forming the transverse bore441.

Piston440may include an actuation pin receiving bore445for receiving actuation pin480. Actuation pin480may include an outer actuation pin engagement surface482, which may be a cylindrical portion of the actuation pin having a diameter substantially corresponding to the internal diameter of actuation pin receiving bore445. Actuation pin480may also include an inner actuation pin engagement surface484, which may be a reduced diameter cylindrical portion compared to the outer actuation pin engagement surface482. One or more conical, chamfered or otherwise tapered transition surfaces486may extend between the inner actuation pin engagement surface484and the outer actuating pin engagement surface482. Actuation pin480may cooperate with an actuation pin return spring488, which at one end may engage an actuation pin spring seat489formed on the actuation pin. An opposite end of actuation pin return spring488may be housed within an actuation pin return spring cavity443defined within the bridge piston440and may engage an end wall447thereof. As will be recognized, actuator return spring488provides a biasing force on the actuation pin480tending to move the actuation pin480to the position shown inFIG. 5.1, which is a locked mode of operation.

Actuation pin480may be moved downward, against the bias of actuation pin return spring488under control of hydraulic fluid entering the bridge piston cap fluid passage496and acting upon an upper surface of the actuation pin480. This motion transitions the collapsing bridge400from a locked state, shown inFIG. 5.1, to an unlocked state, shown inFIG. 5.2. As shown particularly inFIG. 5.1, when the outer actuation pin engagement surface482is in contact with the inner surfaces of the locking pins462, the locking pins462are extended into contact with the annular channel416of the housing410and positively maintained in that position by surface-to-surface contact by the actuation pin480. Downward movement of the actuation pin480from the position shown inFIG. 5.1results in alignment of the actuation pin inner engagement surface—the reduced diameter portion of actuation pin480—aligning with the inner surfaces of the locking pins462, thereby permitting retraction of the locking pins462into opposing ends of transverse bore441and unlocking of the bridge piston440relative to the housing410, as shown inFIG. 5.2. The motive force for the inward motion of locking pins462may be provided by the surface geometry of the locking pins462, particularly where they interface with the lower surface of the annular channel416such that downward force on the piston440by the valve train components causes a net inward force on the locking pins462. That is, the lower surface419of channel416and the undercut surface463of the locking pins462may extend at such an angle to an axis of the piston axis that downward force on the piston440results in inward movement of the locking pins462if the actuation pin480is in the unlocked position. For example, as disclosed in European Patent No. 2975230, the undercut surface463of the locking pins462and the lower surface419of the annular recess416may be defined according to a cone frustum such that engagement of these complementary surfaces induces the net inward force on the locking pins462.

As will be recognized from the instant disclosure, the use of an actuation pin480as shown inFIGS. 4, 5.1 and 5.2provides for positive positioning and synchronized movement of the locking pins462. This may offer additional improvements over the embodiment described above with reference toFIGS. 2 and 3, as the potential scenario in which either or both of the locking pins are either partially engaged or disengaged due to the independent nature in which each are controlled is eliminated. More particularly, the potential for one of the locking pins to remain partially engaged while the other locking pin is fully disengaged, and the associated stress concentration and potential damage to the locking pins or other components is eliminated by the synchronization and positive positioning features of the embodiment ofFIGS. 4, 5.1 and 5.2. Because the reduced diameter portion of the actuation pin462will simultaneously engage or disengage with the locking pins462, the likelihood of partial engagements/disengagements is significantly reduced if not eliminated altogether.

According to further aspects of the disclosure, various geometries and configurations for the locking pins and actuation pin used in a collapsing valve train component may provide additional advantages, especially with regard to alignment, ease of manufacture and assembly of locking pins, actuating pin, and the collapsing valve train components generally contemplated herein. Examples of such geometries and configurations are illustrated inFIGS. 6.1 to 6.8, 7.1to7.8,8.1to8.9, andFIGS. 9-12. Generally, as shown in these figures and further detailed herein, the locking pins may comprise a generally cylindrical body having a circular, oval or elliptical cross-section. As used herein, both in the preceding and following description, the term “cylindrical” is intended to (and should be interpreted to) include shapes that may have circular, oval or elliptical cross-sections. As will be recognized, while non-circular-shaped (or even substantially rectangular) locking pins are less likely to rotate within the transverse bore, substantially circular-shaped locking pins are advantageous to the extent that the transverse bore241,441may be relatively easier and less expensive to produce in comparison to a non-circular, such as an oval- or rectangle-shaped transverse bore. The locking pins may have an actuation pin interface at one end, which may comprise one or more concave actuation pin engaging surfaces, and a housing interface at an opposite end, which may comprise one or more convex housing engaging surfaces.

The concave actuation pin engaging surfaces of the actuation pin interface of the locking pins may be configured to complementarily engage the outer actuation pin engagement surface (i.e.,482inFIG. 4)—the outer diameter—of the actuation pin as described above. In this manner, the concave actuation pin engaging surfaces of each locking pin may operate as alignment surfaces to ensure alignment of the locking pins with the actuation pin and to prevent excessive rotation of the locking pin when in the retracted and in the deployed positions and when moving from a retracted position to a deployed or extended position out of the transverse bore and vice versa. Likewise, the convex housing engaging surfaces of the housing interface of the locking pins may be configured to complementarily engage surfaces of the annular channel formed in housing (i.e., the valve bridge body).

Referring collectively toFIGS. 6.1 to 6.8,FIGS. 6.1 to 6.4are isometric views andFIGS. 6.5 to 6.8are orthographic projected views of an outer end, inner end, side and top of an example embodiment of a locking pin600. The locking pin600may have a generally cylindrical shape and may include an actuation pin interface610on the inner end and a housing interface630on an outer end. Actuating pin interface610may include a first actuating pin engagement surface612formed as a concave surface having a radius that is sufficient to accommodate the outer diameter of the outer locking pin engagement surface (i.e.,482inFIG. 4) of the actuating pin480, thus providing stable engagement of the locking pin600with the actuating pin when the locking pin is in an extended position. In this regard, actuating pin engagement surface612also functions as an alignment surface to keep the locking pin aligned with the actuating pin when the locking pin is in the extended position. Actuating pin interface610may further include second and third actuator pin engagement surfaces614and616on an upper and lower portion, respectively, of the actuating pin interface610. The second and third actuator pin engagement surfaces614and616may each comprise a conical, chamfered surface that may extend at an angle to the actuating pin axis and be adapted to engage respective transition surfaces (i.e.,486inFIG. 4) on the actuating pin480. Conical surfaces614and616may serve as a mechanism for maintaining alignment and preventing rotation of the locking pins within the transverse bore, particularly as the locking pins move from an extended position to the retracted position. Such alignment and anti-rotation function is illustrated in more detail inFIG. 9, where the conical transition986of the actuation pin980is about to be engaged by a conical chamfered alignment surface916of locking pin962. In the example shown inFIG. 9, only one conical alignment surface is provided on the locking pin and only one transition surface is provided on the actuating pin980.

Alignment surface916is adapted to guide and prevent rotation of the locking pin962during its entire travel from the extended position in engagement with the outer locking pin engagement surface982of actuating pin980to the retracted position in which locking pin is in engagement with the inner locking pin engagement surface984of actuating pin480. Stated another way, when these two conical surfaces,916and986, engage each other (as in the case where the actuation pin is sliding to cause locking of the bridge piston), their complementary shapes urge alignment of the locking pin with the actuation pin, thereby preventing or at least minimizing rotation of the locking pin.

Housing interface630of locking pin600may include an outer concave surface632and two housing engagement surfaces634and636. Housing engagement surfaces634and636may engage one or respective chamfered surfaces in the annular channel in the housing bore (i.e.,419inFIG. 5.1 or 919inFIG. 9). Housing engagement surfaces634and636may be defined according to a cone frustum or conical frustum and may engage a correspondingly shaped surface in the annular channel in the housing bore. This shape of the housing engagement surfaces634and636, together with the shape of the surfaces on the annular channel, not only provide for alignment and anti-rotation of the locking pins when moving to the extended position, but facilitate inward force on and movement of the locking pins to the retracted position when the actuating pin is in an unlocked position and the bridge piston is subject to downward valve train forces.

Referring collectively toFIGS. 7.1 to 7.8, there is illustrated another example embodiment of a locking pin700according to aspects of the disclosure. In this embodiment, the actuating pin interface710includes a first engagement surface712for engaging the outer locking pin engagement surface of the actuating pin480(FIG. 4) and a single chamfered conical surface714on an upper portion of the actuating pin interface710. The housing interface730of the locking pin700is similarly provided with a single conical surface734on an upper portion of the housing interface730.

FIGS. 8.1 to 8.9collectively illustrate another example embodiment of a locking pin800according to aspects of the disclosure. In this embodiment, locking pin800is provided with two conical chamfered alignment surfaces814and816on an actuating pin interface810. Locking pin800is also provided with an undercut housing interface830, including an outer convex end surface831, conical housing engagement surface836and a reduced diameter convex inner end surface833. In this example, a lower portion of the convex end surface (e.g., half or more of the thickness of the lock pin) is removed to form the conical surface836transitioning between the outermost convex end surface831and a reduced diameter convex inner end surface833. The resulting projection, as best shown inFIG. 11, preferably has surfaces that closely match the curvatures of the annular channel. In this manner, the conical transition surface on the locking pin800is able to relatively broadly engage a corresponding surface of the annular channel, thereby better dispersing the applied forces and minimizing the likelihood of damage to the components. This configuration also provides alignment benefits with regard to alignment of the housing interface830with the annular channel. Particularly, the undercut housing interface830provides an extended guiding surface840that extends above the housing engagement surface836. As will be recognized by the instant disclosure, provision of a relatively broad and flat or conical surface on the locking pin in this manner may better distribute the substantial forces applied to the locking pin when it is extended into and in contact with a similarly broad and flat or conical surface of the annular channel.

A further advantage of the double conical chamfered surfaces on the actuating pin interface according to aspects of the disclosure, such as the surfaces814and816in the embodiment ofFIG. 8, and the surfaces614and616in the embodiment inFIG. 6, is improved alignment and anti-rotation of the locking pin. Referring additionally toFIG. 10, such configurations are used in conjunction with actuating pins, such as actuating pin1080, which has dual transition surfaces1486and1487cooperating with the conical chamfered surfaces on the locking pin1814and1816is improved alignment and anti-rotation features of the locking pin. More specifically,FIG. 10shows the extent of rotation of locking pin1462(and the degree of misalignment of conical housing engagement surface1836) permitted within the locking pin receptacle (transverse bore) before rotation of the locking pin1462is limited by the chamfered surfaces1816and1814. As will be recognized, the double conical chamfered surfaces1816and1814may prevent the locking pin1462from rotating to a degree that would prevent the projected portion of the locking pin from entering the annular channel on the housing, thus ensuring proper alignment and operation of the locking pin.

Referring additionally toFIG. 12, according to further aspects of the disclosure, locking pins may be provided with an asymmetrical configuration of the conical surfaces in order to prevent assembly errors. As can be seen inFIGS. 8.1-8.9andFIG. 10, the conical surfaces814,1814and816,1816are not symmetrical. In the illustrated example, the conical surface1814on the normally upward facing portion of the concave end surface is formed at a deeper depth as compared to the conical surface1816on the normally downward facing portion of the concave end surface. At the same time, the conical, chamfered transitions of the actuation pin may be similarly asymmetrical formed to complementarily engage the asymmetrical conical surfaces of the concave end surface. As a result, if the lock pin is inserted upside down, as illustrated inFIG. 12, engagement of the conical surface on the normally downward facing portion of the concave end surface with the conical chamfer of the actuation pin will cause the actuation pin to extend from the transverse bore, thereby causing the locking pin to extend from the piston even in an innermost position of the locking pin against the actuating pin, thereby preventing insertion of the bridge piston into the bore formed in the bridge body.