Patent Description:
Internal combustion engines typically employ numerous valves to control the fluid connections amongst different parts of the engine, such as intake valves and exhaust valves to open and close intake and exhaust connections to a combustion cylinder. It is common for engine valve actuation to be achieved by a mechanical linkage between a crankshaft of the engine and one or more rotating camshafts, in turn rotatable to actuate the valves. In a typical valve actuation system the camshaft is rotated by a cam gear in mesh with an engine flywheel, and includes a plurality of non-circular cams that engage valve lifters to open engine valves, and permit the engine valves to be closed with biasing springs. Rocker arms are provided to reciprocate back and forth to open and close the valves, with pushrods or other intervening hardware coupling the valve lifters to the rocker arms.

In operation, cam followers such as rollers directly contact the cams and enable the valve lifters to reciprocate within bores in the engine housing. Proper operation generally requires an angular orientation of the valve lifters to be maintained relative to their axes of reciprocation, or permitted to rotate within a relatively tightly controlled range. Internal combustion engine operation is a dynamic process, however. Valve lifters can become misaligned, potentially requiring service or even resulting in catastrophic engine failure. Many designs for limiting rotation of valve lifters have been proposed over the years, ranging from geometry of the valve lifters themselves, relative to one another and/or relative to the engine housing, to specialized spring clips coupled with valve lifters and structured to engage with parts of the engine housing. One known anti-rotation roller valve lifter is set forth in <CIT>. The '<NUM> patent proposes a roller lifter having a first end with a first diameter, and a second end with a greater diameter and having a flat surface configured to engage a corresponding flat surface on an adjacent lifter. The strategy set forth in the '<NUM> patent may have various applications, but there is always room for improvement and development of alternative strategies.

<CIT> discloses a guide assembly for a valve lifter of an engine. The valve lifter is at least partly received within a bore of a body of the engine and an end portion of the valve lifter is exposed to an outside of the body. The guide assembly includes a pin and a guide. The pin is adapted to be fixedly coupled to the end portion of the valve lifter, while the guide is adapted to be coupled to the body. The guide defines a channel. The pin is received within the channel and cooperates with the channel to facilitate a movement of the valve lifter along an axis of the bore and restrict a rotation of the valve lifter about the axis of the bore.

<CIT> discloses an internal combustion engine including a cylinder block defining a lifter bore, and a valve lifter assembly positioned at least partially within the lifter bore and configured to actuate a push rod. The assembly includes a valve lifter and an angular displacement-limiting clip. A cutout is formed on a proximal end of the valve lifter and includes a channel and a taper. The valve lifter is rotatable out of alignment with a cam, and the clip limits angular displacement of the valve lifter via contacting a wall portion of the cylinder block. First and second fillets of the clip are positionable within the cutout, such that the taper provides a clearance for inhibiting impingement of the valve lifter upon the fillets.

<CIT> discloses a lifter rotation preventing structure including a lifter body, a retainer and a biasing member. The lifter body is inserted into a sliding hole of a housing and reciprocated according to rotation of a cam. The lifter body has a peripheral wall slidable in a sliding hole and a partition wall partitioning an inside of the peripheral wall into a first space where the cam is located and a second space located opposite the first space. The retainer has a retainer body connected to an engaging member and a rotation preventing protrusion protruding from an outer periphery of the retainer body and fittingly extending through the peripheral wall. The rotation preventing protrusion has a distal end moved into a rotation preventing groove to prevent the lifter body from rotation. The biasing member interposed between the retainer body and the housing to bias the lifter body to the cam side.

<CIT> discloses a roller cam follower, especially an engine hydraulic roller lifter, which is restrained from rotation away from a position in which the roller rotates squarely on its associated cam by a retainer clip fixed on the lifter body and having a tang with flat sides engaging an axial groove in an associated bore of the engine lifter gallery. The retainer clip is a closed ring with opposite flexible hat sections connected by arches having inner edges that snap into a groove on the lifter body. The inner edges are preferably angled upward to aid installation and the hat sections preferably have squared inner ends that engage flats on the lifter body to prevent relative rotation of the body and clip.

<CIT> discloses a roller lifter including a lifter body having a cylindrical peripheral wall and a roller rotatably mounted on the lifter body via a shaft member and brought into contact with a cam. The peripheral wall has an outer periphery formed with a sliding surface which is slid on an inner wall of a cylinder. The lifter body has a rotation stopper formed by outwardly protruding a part of the peripheral wall, and an opening formed in another part of the peripheral wall which another part is radially opposed to the rotation stopper. The opening is open so that the rotation stopper oppositely faces the opening.

<CIT> discloses a hydraulic lash adjuster (HLA) sleeve configured to be received within a lifter bore of an engine block, including a cylindrical sleeve having an outer surface defining an outer diameter, and an inner surface defining an inner diameter. The outer diameter is sized for an interference fit with the lifter bore to prevent rotation of the HLA sleeve within the lifter bore. The inner diameter is sized to receive a lifter.

<CIT> discloses a valve lifter assembly for an engine including a valve lifter body, a roller pin mounted in the valve lifter body and having a crowned barrel portion, and a substantially cylindrical roller mounted about the crowned barrel portion of the roller pin. The roller may have a crowned outer surface with a cylindrical center portion having a constant outer diameter equal to a roller maximum outer diameter, and oppositely disposed variable outer diameter outer portions extending outwardly from either side of the cylindrical center portion toward corresponding roller ends of the roller with a roller outer diameter decreasing as the variable outer diameter outer portions extend outwardly from the cylindrical center portion. The valve lifter assembly may further include a clip having engagement surfaces that are machined to have complimentary shapes to corresponding engagement surfaces of the valve lifter body.

There is provided herein a valve lifter assembly including an anti-rotation device having a collar with a sleeve portion having an inner peripheral guide surface forming a lifter bore and a boss portion having an outer peripheral surface. The anti-rotation device further includes a bridge connector projecting from the outer peripheral surface. The valve lifter assembly further includes a valve lifter coupled to the anti-rotation device and defining a longitudinal lifter axis extending between a first axial body end and a second axial body end. The valve lifter includes a lifting surface facing a direction of the first axial end, and a cam follower mounted to the second axial body end. The valve lifter is slidably coupled with the anti-rotation device such that the valve lifter and the anti-rotation device are free to reciprocate relative to one another and the inner peripheral guide surface has a shape configured to limit rotation of the valve lifter.

Referring to <FIG>, there is shown an engine <NUM> according to one embodiment. Engine <NUM> may include an internal combustion engine, such as a compression-ignition diesel engine structured to operate on diesel distillate fuel, however, the present disclosure is not thereby limited. Engine <NUM> includes an engine housing <NUM>, and a crankshaft <NUM> supported for rotation in engine housing <NUM>. One or more combustion cylinders <NUM> are formed in engine housing <NUM>, with a piston <NUM> structured to reciprocate in each combustion cylinder <NUM> between a top-dead-center position and a bottom-dead-center position in a conventional four-cycle pattern. Combustion cylinders <NUM>, one of which is shown and referred to in the singular hereinafter, may be arranged in any suitable configuration such as a V-pattern, an in-line pattern, or still another. A connecting rod <NUM> couples crankshaft <NUM> to piston <NUM> in a generally conventional manner. A first engine valve <NUM> and a second engine valve <NUM> are structured to open and close fluid communication between combustion cylinder <NUM> and gas exchange conduits formed in engine housing <NUM>. One of engine valves <NUM> and <NUM> can include an intake valve and the other an exhaust valve, however, in a practical implementation strategy both of engine valves <NUM> and <NUM> are intake valves or exhaust valves, with a valve bridge <NUM> coupling engine valves <NUM> and <NUM> to a common rocker arm <NUM>. It will be appreciated that additional engine valves can be associated with combustion cylinder <NUM>, but are not visible in the view of <FIG>.

Rocker arm <NUM> is part of an engine valve actuation system <NUM>. Valve actuation system <NUM> may include a rotatable camshaft <NUM> that is coupled to rotate with crankshaft <NUM> such as by way of suitable intervening gearing. Valve actuation system <NUM> further includes a plurality of valve lifters, one of which is shown at <NUM>. Valve lifter <NUM> is coupled by way of a pushrod <NUM> with rocker arm <NUM> and reciprocates in engine housing <NUM> to reciprocate rocker arm <NUM> to open and close engine valves <NUM> and <NUM> together. Valve lifter <NUM> includes a lifting surface <NUM> that is contacted by pushrod <NUM>. In other embodiments, a valve lifter might be associated with a single pushrod and a single engine valve, or might be directly coupled with a rocker arm, or reciprocated to actuate an engine valve according to still another architecture. An anti-rotation device <NUM> is shown coupled with valve lifter <NUM> in <FIG>, the details and functionality of which are further discussed herein.

Referring now to <FIG> and <FIG>, there are shown additional details of valve actuation system <NUM>, including a valve lifter assembly <NUM>. Valve lifter assembly <NUM> includes a first valve lifter <NUM>, and a second valve lifter <NUM>. It should be appreciated that description and discussion herein of either of valve lifters <NUM> or <NUM> can be understood to refer by way of analogy to the other of valve lifters <NUM> and <NUM>, except where otherwise indicated or apparent from the context. Accordingly, the terms "first" and "second" are used herein merely for convenience. First valve lifter <NUM> and second valve lifter <NUM> (hereinafter "valve lifter <NUM>" and "valve lifter <NUM>") may be substantially identical and interchangeable for service in engine <NUM>, however, the present disclosure is not thereby limited.

Valve lifter <NUM> includes a lifter body <NUM>, defining a longitudinal lifter axis <NUM>. Valve lifter <NUM> includes a lifter body <NUM> defining a longitudinal lifter axis <NUM>. Lifter axes <NUM> and <NUM> may be oriented perpendicular to a cam axis of rotation <NUM> defined by camshaft <NUM>. In the illustrated embodiment camshaft <NUM> includes a first cam or cam lobe <NUM> having a first cam profile about cam axis of rotation <NUM>, and a second cam or cam lobe <NUM> having a second cam profile different from the first cam profile, about cam axis of rotation <NUM>. The first cam profile and the second cam profile may be substantially identical in shape, but have different angular orientations about cam axis of rotation <NUM>. Valve lifter <NUM> may be structured to actuate one or more intake valves in engine <NUM>, with valve lifter <NUM> being structured to actuate one or more exhaust valves in engine <NUM>, or vice versa. Each of valve lifters <NUM> and <NUM> may be coupled to anti-rotation device <NUM>, as further discussed herein.

In valve lifter <NUM>, as shown in <FIG>, longitudinal lifter axis <NUM> extends between a first axial body end <NUM> and a second axial body end <NUM>. Valve lifter <NUM> and valve lifter <NUM> may each include a lifting surface, shown in valve lifter <NUM> at <NUM> as noted above, that faces a direction of the corresponding first axial lifter body end. Valve lifter <NUM> includes a cam follower <NUM> mounted to second axial body end <NUM>. Valve lifter <NUM> includes a cam follower <NUM> analogously mounted. Each of cam followers <NUM> and <NUM> can include a roller in contact with the corresponding cam <NUM> and <NUM>, respectively. Contact between cam follower <NUM> and first cam <NUM> enables valve lifter <NUM> to reciprocate in response to rotation of cam <NUM>. Contact between cam follower <NUM> and cam <NUM> enables valve lifter <NUM> to reciprocate in response to rotation of cam <NUM>.

As further illustrated, valve lifter <NUM>, and by analogy valve lifter <NUM>, includes a necked-down portion <NUM>. Necked-down portion <NUM> may include a plurality of arcuate outer surfaces <NUM> and <NUM> and a plurality of planar outer surfaces <NUM> and <NUM>, in an alternating arrangement with arcuate outer surfaces <NUM> and <NUM>. A cutout <NUM> may also be formed in first axial body end <NUM>, to remove mass in compensation for a mass of anti-rotation device <NUM> carried by valve lifter <NUM> as further discussed herein. Valve lifter <NUM> may also include a first carrying bore <NUM> and a second carrying bore <NUM>, formed in and opening at one of the plurality of planar outer surfaces, in the illustrated case surface <NUM>. Carrying bores <NUM> and <NUM> are used for coupling valve lifter <NUM> to anti-rotation device <NUM> as further discussed herein. The substantially identical configurations of valve lifter <NUM> and valve lifter <NUM> can enable coupling with anti-rotation device <NUM> in either of two configurations, as will be apparent from <FIG>. Embodiments are contemplated where valve lifter assembly <NUM> includes, such as in a service package or kit, an assembly of a valve lifter coupled with anti-rotation device <NUM> in one of the two possible configurations, as well as embodiments where a valve lifter is coupled with anti-rotation device <NUM> in the other of the two possible configurations. In still other instances, a service package or kit could include two valve lifters, identical to one another or different, assembled with anti-rotation device <NUM>, or packaged together but not assembled. As will be further apparent from the following description, anti-rotation device <NUM> may be fixedly coupled to a first one of valve lifters <NUM> and <NUM>, and slidably coupled with a second one of valve lifters <NUM> and <NUM>, when positioned for service in engine <NUM>. Coupling between anti-rotation device <NUM> and valve lifters <NUM> and <NUM> when installed in engine <NUM> will permit reciprocation of each of valve lifters <NUM> and <NUM> but limit rotation of each of valve lifters <NUM> and <NUM>.

Referring also now to <FIG>, there is shown a top view of valve lifters <NUM> and <NUM> as they might appear installed in engine <NUM> and positioned for reciprocation in engine housing <NUM>. Anti-rotation device <NUM> is coupled with each of valve lifters <NUM> and <NUM>, and each of valve lifters <NUM> and <NUM> can be reciprocated, in and out of the page in the <FIG> illustration, but inhibited from rotating. Such functionality is based on the shape and design of anti-rotation device <NUM>, enabling fixed coupling with one of valve lifters <NUM> and <NUM>, and slidable coupling with the other of valve lifters <NUM> and <NUM>.

Referring also now to <FIG> there are shown additional features of anti-rotation device <NUM>. Anti-rotation device <NUM> includes a collar <NUM> having a sleeve portion <NUM> and a boss portion <NUM>. Sleeve portion <NUM> includes an inner peripheral guide surface <NUM> forming a lifter bore <NUM> defining a bore center axis <NUM>. Inner peripheral guide surface <NUM> has a shape that is varied, circumferentially around bore center axis <NUM>, to limit rotation of a first valve lifter slidably received in lifter bore <NUM>. As discussed above, either of valve lifter <NUM> or valve lifter <NUM> could be a first valve lifter slidably received in lifter bore <NUM>. In a practical implementation, inner peripheral guide surface <NUM> includes a plurality of inner planar surfaces <NUM> in an alternating arrangement with a plurality of inner arcuate surfaces <NUM>. It will be understood that valve lifter <NUM>, for example, can be slidably received in lifter bore <NUM> such that outer planar surfaces <NUM> and <NUM> are positioned in facing relation to inner planar surfaces <NUM>, and arcuate outer surfaces <NUM> and <NUM> are in facing relation to inner arcuate surfaces <NUM>. As a result, while valve lifter <NUM> can slide within lifter bore <NUM> it is restricted from rotation about longitudinal lifter axis <NUM>.

Boss portion <NUM> includes an outer peripheral surface <NUM> facing a radially outward direction, relative to bore center axis <NUM>. Outer peripheral surface <NUM> may include an outer planar surface <NUM> located opposite to one of inner planar surfaces <NUM>, such that a radial thickness of boss portion <NUM>, relative to bore center axis <NUM>, is defined between outer planar surface <NUM> and the one of inner planar surfaces <NUM>. It can also be seen that sleeve portion <NUM> includes an arcuate band <NUM> originating and terminating at boss portion <NUM>. Arcuate band <NUM> may have a semi-circular or other curvilinear outer profile, and an inner profile, formed by shapes of surfaces <NUM> and <NUM>.

Anti-rotation device <NUM> further includes a bridge connector <NUM> projecting from outer peripheral surface <NUM> for engagement with a second valve lifter, again, either of valve lifter <NUM> or valve lifter <NUM>. Anti-rotation device <NUM> may further include a second bridge connector <NUM> projecting, in parallel with first bridge connector <NUM>, from outer peripheral surface <NUM>. Also in the illustrated embodiment each of first bridge connector <NUM> and second bridge connector <NUM> includes a cylindrical protrusion. Embodiments are contemplated where first bridge connector <NUM> and second bridge connector <NUM> are separate pieces installed in and supported within boss portion <NUM>. To this end, boss portion <NUM> may include a first connector bore <NUM> and a second connector bore <NUM> formed therein, and each opening at outer peripheral surface <NUM> within outer planar surface <NUM>. First bridge connector <NUM> and second bridge connector <NUM> are supported, respectively, in first connector bore <NUM> and second connector bore <NUM>. Each of first bridge connector <NUM> and second bridge connector <NUM> may include a dowel, such as a cylindrical metallic dowel, interference-fitted in first connector bore <NUM> and second connector bore <NUM>, respectively. A suitable adhesive, such as those available under the trade name LOCTITE®, may enhance the retention of first and second bridge connectors <NUM> and <NUM> within first and second connector bores <NUM> and <NUM>. Collar <NUM> may include a single fabricated metallic piece. In other embodiments, one or more bridge connectors might be formed integrally with a collar. Accordingly, collar <NUM> and one or more bridge connectors <NUM> and <NUM> might include a single fabricated piece formed of a metallic material and machined to a suitable shape, or potentially a different material such as a polymeric material or a glass polymer material that is molded and/or machined.

Returning to <FIG>, it can be seen from the top view of the illustration that first bridge connector <NUM> is visible and received within carrying bore <NUM>, while second bridge connector <NUM> is hidden and behind the plane of the page. As shown, first bridge connector <NUM> and second bridge connector <NUM> are offset from one another in an axial direction, in and out of the page in <FIG>, and aligned with one another in a circumferential direction around bore center axis <NUM>. It can also be seen from <FIG> that outer peripheral surface <NUM> defines a longitudinal midline <NUM> parallel to bore center axis <NUM>. First bridge connector <NUM> and second bridge connector <NUM> are offset, generally in the circumferential direction, relative to longitudinal midline <NUM>. The offset of bridge connectors <NUM> and <NUM> can be understood to mean that longitudinal midline <NUM> does not intersect center axes of bridge connectors <NUM> and <NUM>, not necessarily that midline <NUM> does not intersect bridge connectors <NUM> and <NUM> themselves. Planar outer surface <NUM> of valve lifter <NUM> may also define a longitudinal midline <NUM>, with bridge connectors <NUM> and <NUM> and carrying bores <NUM> and <NUM> being analogously offset, in a circumferential direction around lifter axis <NUM>, relative to longitudinal midline <NUM>. As illustrated in <FIG>, an engine housing protrusion <NUM> is located adjacent to each of valve lifter <NUM> and valve lifter <NUM> when installed for service in engine <NUM>. The offset of first and second bridge connectors <NUM> and <NUM> relative to longitudinal midlines <NUM> and <NUM> assists in packaging valve assembly <NUM> for service in engine <NUM> without interference with engine housing protrusion <NUM> or other structures. Also in the illustrated embodiment, anti-rotation device <NUM> includes a first axial end surface <NUM>, and a second axial end surface <NUM>. Second axial end surface <NUM> may be substantially planar, whereas first axial end surface <NUM> may include two separate substantially planar surfaces, including a first planar portion located upon arcuate band <NUM>, and a second planar portion located in part upon arcuate band <NUM> and in part upon boss portion <NUM>. An axial thickness of anti-rotation device <NUM> between first axial end surface <NUM> and second axial end surface <NUM> may be less through arcuate band <NUM> than through boss portion <NUM>, as depicted in the drawings.

Referring to the drawings generally, during operation of engine <NUM> a mixture of fuel and air is combusted in combustion cylinder <NUM> to urge piston <NUM> toward a bottom dead center position to rotate crankshaft <NUM> by way of connecting rod <NUM>. Camshaft <NUM> may be rotated, typically at one-half engine speed, in a conventional four-cycle pattern, causing valve lifters <NUM> and <NUM> to reciprocate to open and close the associated engine valves. Each of valve lifter <NUM> and valve lifter <NUM> includes a lifting surface in contact with a pushrod and structured to actuate the respective engine valves as described, with the respective cam followers <NUM> and <NUM> contacting cams <NUM> and <NUM> on camshaft <NUM> to reciprocate valve lifters <NUM> and <NUM> at suitable timings.

As discussed herein, anti-rotation device <NUM> may be fixedly coupled to bridge connector <NUM> and bridge connector <NUM>. Valve lifter <NUM> may be slidably received in lifter bore <NUM>. Contact between inner peripheral guide surface <NUM> and valve lifter <NUM> inhibits rotation of valve lifter <NUM>. The fixed coupling of valve lifter <NUM> to bridge connector <NUM> and bridge connector <NUM> causes anti-rotation device <NUM> to move with valve lifter <NUM>, relative to valve lifter <NUM>, between a lifted position and a dropped position in response to rotation of camshaft <NUM>, in particular rotation of cam <NUM> in the illustrated embodiment. In <FIG>, valve lifter <NUM> and valve lifter <NUM> are shown approximately as they might appear at lowered or dropped positions, such that the respective engine valves are closed. As camshaft <NUM> is rotated, about cam axis of rotation <NUM>, valve lifter <NUM> will be urged upward and downward in response to rotation of cam <NUM>, causing anti-rotation device <NUM> to move upward and downward relative to valve lifter <NUM>, depending upon the present lifted or lowered state of valve lifter <NUM>. Different cam profiles, and/or cam angular orientations, can give different results respecting whether relative movement is upward versus downward at any given time, however, in all cases anti-rotation device <NUM> and valve lifter <NUM> are free to reciprocate relative to one another but valve lifter <NUM> is inhibited from rotating or restricted to rotation in a relatively narrow range about lifter axis <NUM>.

Claim 1:
A valve lifter assembly (<NUM>) comprising:
an anti-rotation device (<NUM>) including, a collar (<NUM>) having a sleeve portion (<NUM>) with an inner peripheral guide surface (<NUM>) forming a lifter bore (<NUM>) and a boss portion (<NUM>) having an outer peripheral surface (<NUM>), and a bridge connector (<NUM>) projecting from the outer peripheral surface (<NUM>); and
a valve lifter (<NUM>, <NUM>) coupled to the anti-rotation device (<NUM>) and defining a longitudinal lifter axis extending between a first axial body end (<NUM>) and a second axial body end (<NUM>), and the valve lifter (<NUM>, <NUM>) including a lifting surface (<NUM>) facing a direction of the first axial body end (<NUM>), and a cam follower (<NUM>, <NUM>) mounted to the second axial body end (<NUM>);
wherein the valve lifter (<NUM>, <NUM>) is slidably coupled with the anti-rotation device (<NUM>) such that the valve lifter (<NUM>, <NUM>) and the anti-rotation device (<NUM>) are free to reciprocate relative to one another; and
the inner peripheral guide surface (<NUM>) has a shape configured to inhibit rotation of the valve lifter (<NUM>, <NUM>).