Patent Description:
Valve actuation systems for use in internal combustion engines are well known in the art. Such valve actuation systems typically include a valve train that, in turn, comprises one or more components that transfer valve actuation motions from a valve actuation motion source (e.g., one or more cams) to an engine valve. A component often found in valve trains are so-called valve bridges comprising devices that span two or more engine valves associated with a given cylinder. In many cases, such valve bridges permit another component of a valve train (e.g., a rocker arm) to simultaneously actuate the two more engine valves engaged with the valve bridge. Ideally, in operation, opposition of forces applied by a motion-conveying component (such as a rocker arm) and by engine valve springs ensures that a valve bridge remains in contact (with allowances for normal lash settings) simultaneously with the motion-conveying component and with the engine valves. In this manner, the valve bridge is consistently maintained in alignment with, and positioned to convey valve actuation motions to, the engine valves. As used herein, this state of the valve bridge is referred to as a "controlled state" of the valve bridge relative to the engine valves.

Some valve actuation systems are configured to provide so-called auxiliary valve actuation motions, i.e., valve actuation motions other than or in addition to the valve actuation motions used to operate an engine in a positive power production mode through the combustion of fuel. In such valve actuation systems, a valve bridge may be configured to include devices or lost motion assemblies that permit valve actuation motions to be transmitted through the valve bridge to the engine valves, or selectively "lost" where such motions are not transmitted through the valve bridge to the engine valves. <FIG> illustrates such a system described in <CIT>.

In this case, a valve bridge <NUM> is provided with a lost motion assembly in the form of a locking mechanism. In the illustrated embodiment, the locking mechanism comprises a ball <NUM> that may be forced through an opening in an outer plunger <NUM> and into engagement with a recess <NUM> formed in the body of the valve bridge. In this state, the ball <NUM> is prevented from disengaging the recess <NUM> due to an outer diameter of an inner plunger <NUM>, thereby locking the outer plunger <NUM> into a fixed relationship relative to the valve bridge <NUM>. Consequently, any valve actuation motions applied to the outer plunger <NUM> by a rocker arm <NUM>/<NUM> is conveyed to the valve bridge <NUM> and to the engine valves <NUM>/<NUM>, <NUM>/<NUM>. However, when a recess formed in the inner plunger <NUM> is aligned with ball <NUM>, the ball is able to disengage the recess <NUM> in the valve bridge <NUM>, thereby unlocking the outer plunger <NUM> and allowing it to reciprocate relative to the valve bridge <NUM>. In this state, any valve actuation motions applied to the outer plunger <NUM> cause the outer plunger to move within the valve bridge <NUM> and are not conveyed to the engine valves. Another valve bridge-based locking/unlocking system is disclosed in <CIT> and <CIT>.

However, in systems of the type illustrated in <FIG>, the possibility exists for partial engagement of the locking mechanism. In this case, it is possible for valve actuation motions to be initially applied to the engine valves, thereby causing the engine valves to lift off their valve seats. Due to the partial engagement of the locking mechanism, however, increased loading or vibration in the valve actuation system causes the locking mechanism to quickly switch from the partially locked to an unlocked state. When this happens, the force provided by the valve actuation motions to open the engine valves is suddenly removed, permitting the engine valves to rapidly accelerate to a closed position in an unrestrained manner under the considerable force of the valve springs. When the engine valves reach the fully closed position (i.e., stopped against the valve seats formed in the cylinder head), the momentum applied to the valve bridge can cause the valve bridge to continue on an uncontrolled trajectory generally in a direction away from the engine valves until hitting the rocker arm or some other object. In fact, it is possible for the valve bridge to come off of either of the tips of the engine valves such that the valve bridge is dislodged from the engine valves, thereby causing engine damage. Movement of this type is referred to as "uncontrolled movement" of a valve bridge and, as used herein, this state of the valve bridge is referred to as an "uncontrolled state" of the valve bridge relative to the engine valves. It is also known for uncontrolled states of valve bridges to occur as a result of overspeed operation of an internal combustion engine.

Given this potential for malfunctioning, solutions that prevent, minimize or accommodate uncontrolled states of valve bridges (regardless of the cause) would represent a welcome addition to the art.

The instant disclosure describes valve bridge systems that overcome the above-described problems with prior art valve bridge systems. The valve bridge system according to claim <NUM> comprises a valve bridge configured to extend between at least two engine valves of an internal combustion engine. A valve bridge guide is operatively connected to the valve bridge and comprises a valve bridge control surface for selectively contacting at least one of the valve bridge or engine valve assembly (comprising the at least two engine valves, at least two valve springs corresponding to the at least two engine valves and at least two spring retainers corresponding to the at least two engine valves). In this embodiment, the valve bridge guide may be made out of a moldable polymer. The valve bridge control surface is configured to avoid contact with the valve bridge or the engine valve assembly when the valve bridge is in a controlled state relative to the at least two engine valves and further configured to contact the valve bridge or the engine valve assembly to resist uncontrolled movement of the valve bridge when the valve bridge is in an uncontrolled state relative to the at least two engine valves. The valve bridge guide is configured to extend between the at least two valve springs, where the valve bridge control surface is at least one concave surface corresponding to at least one convex surface defined by the at least two valve springs or the at least two spring retainers, or a convex surface defined by a portion of the valve bridge. More particularly, each of the at least one concave surfaces may be delimited by opposite edges such that a line intersecting the opposition edges forms a secant relative to outer diameters of corresponding ones of the at least two valve springs or the at least two spring retainers.

The valve bridge guide and valve bridge may form a unitary structure, or the valve bridge guide may comprise one or more separate components operatively connected to the valve bridge. In an embodiment, the valve bridge guide comprises two guide members configured to engage opposite sides of the valve bridge, and may further comprise at least one fastener for operatively coupling the two guide members together. The valve bridge guide may comprise an opening to receive at least a portion of the valve bridge, and may further comprise at least two protruding members, each of the at two protruding members projecting from the valve bridge guide toward the valve bridge and extending past at least a lower surface of the valve bridge facing the at least two engine valves. Further, the at least two protruding members may define the valve bridge control surface. Alternatively, each of the at least two protruding members may comprise an attachment surface for engaging a corresponding surface of the valve bridge.

In a second primary embodiment not according to the appended claims, the valve bridge system may comprise a valve bridge configured to extend between at least two engine valves of an internal combustion engine, the valve bridge comprising a lower surface facing the at least two engine valves and an upper surface opposite the lower surface. The system of this primary embodiment further comprises a valve bridge guide having a first member maintained in a first fixed position relative to the valve bridge, the first member comprising a first surface facing and at a predetermined distance from the upper surface of the valve bridge when the at least two engine valves are in a closed state. The predetermined distance is configured to prevent contact between the first surface and the upper surface of the valve bridge when the upper bridge body is in a controlled state relative to the at least two engine valves, and to permit contact between the first surface and the upper surface of the valve bridge to resist uncontrolled movement of the valve bridge when the valve bridge is in an uncontrolled state relative to the at least two engine valves. Where the valve bridge comprises a receptacle to receive an engine valve tip of one of the at least two engine valves, the predetermined distance may be less than a depth of the receptacle.

The first fixed position of the first member may be in alignment with a first engine valve of the at least two engine valves, the first engine valve being farthest from a rocker shaft of the internal combustion engine. The valve bridge system may further comprise a second member maintained in a second fixed position relative to the valve bridge, the second member comprising a second surface facing and at the predetermined distance from the upper surface of the valve bridge. In this case, the second fixed position of the second member is in alignment with a second engine valve of the at least two engine valves, the second engine valve being closest to a rocker shaft of the internal combustion engine. The first member may be configured for attachment to a cylinder head of the internal combustion engine, whereas the second member may form a unitary structure with a rocker shaft pedestal of the internal combustion engine.

In further alternatives of this second primary embodiment, the valve bridge guide may further comprise a bridge pin disposed in one end of the valve bridge and in alignment with an engine valve of the at least two engine valves. Alternatively, the first member of the valve bridge guide in this embodiment may comprise an arch, configured for attachment to the cylinder head, extending between the at least two engine valves and over the upper surface of the valve bridge, the arch further comprising an opening formed therein aligned with a portion of the valve bridge contacting a valve train component.

The features described in this disclosure are set forth with particularity in the appended claims. These features and attendant advantages will become apparent from consideration of the following detailed description, taken in conjunction with the accompanying drawings. One or more embodiments are now described, by way of example only, with reference to the accompanying drawings wherein like reference numerals represent like elements and in which:.

<FIG> illustrate various embodiments of valve bridge systems comprising valve bridge guides in accordance with the instant disclosure. In all of the embodiments and variations illustrated in <FIG>, it is assumed that valve bridges are of the type illustrated in <FIG>, i.e., valve bridges having locking mechanisms of the general type illustrated in <FIG> and described above.

<FIG> illustrates a first embodiment in accordance with the instant disclosure in which an internal combustion engine <NUM> comprises a pair of valve bridges <NUM>, <NUM> for a single cylinder. In the illustrated embodiment, each valve bridge <NUM>, <NUM> actuates two corresponding engine valves, though it is possible for each valve bridge to actuate more than two engine valves. As known in the art, each valve bridge <NUM>, <NUM> (or any of the other valve bridges illustrated and described herein) may actuate two engine valves of the same type, i.e., two intake or two exhaust valves. For ease of illustration, the features and operation of only a first valve actuation system in accordance with the first embodiment is described, it being understood that the described features and operation are equally applicable to all valve bridges included in the internal combustion engine.

Thus, as shown, a first valve bridge <NUM> spans a pair of engine valves (not visible in <FIG>) in a conventional manner as known in the art. Each engine valve has a valve spring <NUM>, <NUM> that biases its corresponding engine valve into a closed state (i.e., with the engine valve head engaged with a valve seat formed in a cylinder head <NUM>) and a valve spring retainer <NUM>, <NUM> attached to valve stems of the engine valves. As further shown, the valve bridge system <NUM> further comprises a valve bridge guide <NUM> that extends downward (i.e., in the direction of the cylinder head and away from a rocker arm <NUM>) from the valve bridge <NUM> and between the valve springs <NUM>, <NUM>. In an embodiment, the distance that the valve bridge guide <NUM> extends between the valve springs <NUM>, <NUM> is minimally dictated by that portion of the valve bridge <NUM> enclosing the locking mechanism (e.g., with reference to <FIG>, the depth of that portion of the valve bridge housing the outer plunger <NUM> and outer plunger spring <NUM>). In the embodiment illustrated in <FIG>, the valve bridge and the valve bridge guide form a unitary structure, i.e., parts of an undivided whole, such that the locking mechanism is housed within an opening (best shown in <FIG>) formed in the valve bridge <NUM> and valve bridge guide <NUM>. As described in greater detail below, the valve bridge guide <NUM> comprises at least one valve bridge control surface configured to interact with one or both of the valve springs <NUM>, <NUM> or valve spring retainers <NUM>, <NUM> to prevent, minimize or at least accommodate uncontrolled motion of the valve bridge <NUM>.

<FIG> illustrates a cross-sectional view of the valve bridge guide <NUM> and a first valve spring <NUM> taken along section line III-III (as shown in <FIG>). An opening <NUM> for housing the locking mechanism is formed in the valve spring guide <NUM> and <FIG> further illustrates a valve stem <NUM> disposed within a corresponding valve spring <NUM>. More particularly, <FIG> illustrates two valve bridge control surfaces <NUM> defined by the valve bridge guide <NUM> such that the valve bridge control surfaces <NUM> conform to corresponding valve springs <NUM>, <NUM> (only one shown in <FIG>), i.e., the valve bridge control surfaces <NUM> are concave surfaces relative to the convex outer surface of the valve springs <NUM>, <NUM>. Though conforming, the valve bridge control surfaces <NUM> are configured so that, during a controlled state of the valve bridge, the valve bridge control surfaces <NUM> (and, consequently, the valve bridge guide <NUM>) are able to avoid contact with their corresponding valve springs <NUM>, <NUM>. The valve bridge control surfaces <NUM> may be configured so as to be as close as possible to the valve springs <NUM>, <NUM> (within manufacturing tolerances) such that normal movement and vibrations of the valve bridge <NUM>, valve bridge guide <NUM> and the valve springs <NUM>, <NUM> are insufficient to cause contact between the valve bridge control surfaces <NUM> and the valve springs <NUM>, <NUM>. For example, as known in the art, when compression springs such as the valve springs <NUM>, <NUM> are deformed (i.e., compressed), the outer diameter of the spring will increase slightly. Thus, the valve bridge control surfaces <NUM> may be configured to account for the maximum expected changes in the spring diameters while remaining as close as possible to the valve springs <NUM>, <NUM>.

In some instances, it may not be desirable for the valve bridge guide <NUM> to contact the valve springs <NUM>, <NUM>, which could otherwise lead to early degradation of the valve springs <NUM>, <NUM>. Thus, it may be desirable to instead configure the valve bridge control surfaces <NUM> to contact the spring retainers <NUM>, <NUM>. To implement this configuration, it may be necessary to dimension the spring retainers <NUM>, <NUM> to have outer diameters that are larger than outer diameters of the valve springs <NUM>, <NUM>. In this case, the valve bridge control surfaces <NUM> are instead defined by the valve bridge guide <NUM> such that the valve bridge control surfaces <NUM> conform to corresponding spring retainers <NUM>, <NUM>, i.e., the valve bridge control surfaces <NUM> are concave surfaces relative to convex outer surfaces of the spring retainers <NUM>, <NUM>. Once again, such concave surfaces are configured such that, during a controlled state of the valve bridge, the valve bridge control surfaces <NUM> are able to avoid contact with their corresponding spring retainers <NUM>, <NUM>, and are further configured so as to be as close as possible to the valve springs <NUM>, <NUM> (within manufacturing tolerances) such that normal movement and vibrations of the valve bridge <NUM>, valve bridge guide <NUM> and the valve springs <NUM>, <NUM> are insufficient to cause contact between the valve bridge control surfaces <NUM> and the spring retainers <NUM>, <NUM>.

Though the various Figures illustrated and described in this disclosure show at least two concave valve bridge control surfaces <NUM>, this is not necessarily a requirement. For example, a single such valve bridge control surface <NUM> may be employed if used in conjunction with another feature that provide additional control of otherwise uncontrolled movements of the valve bridge <NUM>. For example, in the case where the valve bridge <NUM> is equipped with a bridge pin (see, e.g., <FIG>, element <NUM>), the combination of a single valve bridge control surface <NUM> and the bridge pin may be sufficient.

Configuration of the valve bridge control surfaces <NUM> in accordance with a preferred embodiment is further described relative to <FIG>, which schematically illustrates the valve bridge guide <NUM> and a valve spring <NUM> in magnified form. (Alternatively, as described above, the valve spring <NUM> illustrated in <FIG> could be considered a spring retainer though, for ease of description, only a valve spring <NUM> is described herein. ) As shown, the valve bridge guide <NUM> comprises the concave valve bridge control surface <NUM> in proximity to an outer diameter <NUM> of the valve spring <NUM>. In practice, the clearance between the valve bridge control surface <NUM> and the outer diameter <NUM> is based in part upon manufacturing tolerances of the valve springs <NUM>, <NUM> (or spring retainers <NUM>, <NUM>) and valve bridge <NUM>. Additionally, this clearance is based on the clearance of engine valve tips within receptacles formed in the valve bridge <NUM> to receive the engine valve tips. For example, if the valve bridge <NUM> is allowed to move ± <NUM>, then the clearance between to the valve spring <NUM> and valve bridge control surface <NUM> should be larger than the tolerance of the parts plus the permitted <NUM> of play. Further, chamfer at the bottom of the valve bridge <NUM> should be large enough such that, if the valve bridge <NUM> experiences uncontrolled movement over the full clearance to the valve spring or spring retainer, the valve bridge <NUM> can still reposition itself on the engine valve tips.

As further shown in <FIG>, the circumferential length of the concave valve bridge control surface <NUM> (relative to the outer diameter <NUM> of the spring <NUM>) is delimited by opposite edges <NUM>, <NUM>. In this preferred embodiment, the opposite edges <NUM>, <NUM> are spaced apart to a degree such that, when the valve bridge guide <NUM> is positioned during a controlled state of the valve bridge <NUM>, a line <NUM> intersecting the opposite edges <NUM>, <NUM> as shown forms a secant relative to at least the outer diameter <NUM> of the valve spring <NUM>. Configured in this manner, it will be appreciated that movement of the valve bridge guide <NUM> in either direction indicated by line <NUM> (such as might occur, for example, during an uncontrolled state of the valve bridge <NUM>) will result, if large enough, in contact between the concave valve bridge control surface <NUM> and the spring outer diameter <NUM> such that the valve bridge guide <NUM> will deflect generally in a direction away from the valve spring <NUM> and toward the other valve spring <NUM>. More generally, any rotary motion of the valve bridge <NUM> about the axis of the locking mechanism centerline is constrained as well as lateral movement in both horizontal planes. With this in mind, and referring back to <FIG> and <FIG>, this operation of the concave valve bridge control surfaces <NUM> during an uncontrolled state of the valve bridge <NUM> will tend to cause the valve bridge guide <NUM> to realign itself with valve springs <NUM>, <NUM>, thereby effectively dampening or even eliminating any uncontrolled movement of the valve bridge <NUM> and valve bridge guide <NUM>.

Referring now to <FIG>, a first variation of a valve bridge guide <NUM> comprises a unitary body, separate from the valve bridge <NUM>, having valve bridge control surfaces <NUM> formed on lateral sides thereof, as shown. The valve bridge <NUM> is also illustrated as having receptacles <NUM> for receiving valve stem tips of engine valves, as known in the art and described above. In this embodiment (as well as the further embodiments illustrated in <FIG>), the valve bridge guide <NUM> may be fabricated from the same material (e.g., steel) as the valve bridge <NUM>, though, in a preferred embodiment, the valve bridge guide <NUM> is formed of a lighter, strong material that is nevertheless softer than the valve bridge springs <NUM>, <NUM> (or spring retainers <NUM>, <NUM>) so as to avoid marring or damage. For example, a suitable moldable polymer, as known in the art, may be used for this purpose. Still further types of materials for fabricating the valve bridge guide will be apparent to those skilled in the art.

Regardless, as further shown, the valve bridge guide <NUM> has an opening or bore <NUM> formed therein configured to snugly receive a portion <NUM> of the valve bridge <NUM>. As shown, the portion <NUM> of the valve bridge <NUM> received by the valve bridge guide <NUM> preferably houses at least some of the locking mechanism <NUM>. As further shown, in this embodiment, both the valve bridge guide <NUM> and the portion <NUM> of the valve bridge <NUM> comprise a fastener-receiving feature <NUM>, <NUM>. In this embodiment, the fastener-receiving feature <NUM> of the valve bridge guide comprises a bore that intersects with the opening <NUM> formed in the valve bridge guide <NUM>. Thus, where the bore intersects with the opening <NUM>, the fastener-receiving feature <NUM> essentially comprises a channel having a semi-circular cross section formed in a sidewall of the opening <NUM>. In complementary fashion, the fastener-receiving feature <NUM> of the portion <NUM> of the valve bridge <NUM> is also formed as a semi-circular channel in an exterior side wall surface of the portion <NUM>. When aligned, these respective fastener-receiving features <NUM>, <NUM> may receive fasteners <NUM>, <NUM> such that the valve bridge guide <NUM> is operatively connected to the portion <NUM> of the valve bridge <NUM>. For example, in the illustrated embodiment, the fastener <NUM> may comprise a split dowel pin, as shown, though those skilled in the art will recognize that other types of fasteners, e.g., screws, may be equally employed. In this manner, the valve bridge guide <NUM> is relatively rigidly attached to the valve bridge <NUM> such that they move in unison. As an alternative to the fastener embodiment described above, the valve bridge guide <NUM> (or the other embodiments of the valve bridge guide illustrated in <FIG>) may instead be securely attached to the valve bridge <NUM> using a suitably strong and durable epoxy or similar adhesive. Further still, combinations of such techniques may also be employed as a matter of design choice.

Referring now to <FIG>, a second variation of a valve bridge guide <NUM> is substantially similar to the valve bridge guide <NUM> of <FIG> in that it comprises a unitary body, separate from the valve bridge <NUM>, having valve bridge control surfaces <NUM> formed on lateral sides thereof, as shown. In this embodiment, however, the valve bridge guide <NUM> comprises one or more teeth <NUM> extending inwardly from a sidewall surface of the opening <NUM> and configured to engage with a notch <NUM> formed in an outer sidewall surface of the portion <NUM> of the valve bridge <NUM>. For example, the notch <NUM> may comprise an annular groove or channel formed in the sidewall of the portion <NUM> of the valve bridge <NUM>. When the teeth <NUM> engage the notch <NUM>, the valve bridge guide <NUM> is once again operatively connected to the valve bridge in relatively rigid fashion such that the valve bridge guide <NUM> and the valve bridge <NUM> move in unison. It is noted that, in this embodiment, the deployment of the one or more teeth <NUM> and notch <NUM> may be equally reversed, i.e., the teeth <NUM> may be formed on the outer sidewall surface of the portion <NUM> of the valve bridge <NUM> and the notch <NUM> formed on the inner sidewall surface of the opening <NUM>.

As further shown in <FIG>, the valve bridge guide <NUM> may comprise at least two protruding members <NUM>, <NUM> projecting from the valve bridge guide <NUM> toward the valve bridge <NUM>. As shown in <FIG>, the valve bridge <NUM> has a lower surface <NUM> and, in an embodiment, the protruding members <NUM>, <NUM> extend at least past the lower surface <NUM> of the valve bridge <NUM>. In this embodiment, the at least two protruding members <NUM>, <NUM> aid in orienting the valve bridge guide <NUM> on the valve bridge <NUM>, thereby preventing rotation of the valve bridge <NUM> relative to the valve bridge guide <NUM>. In this manner, at least two protruding members <NUM>, <NUM> further aid in aligning the valve bridge control surface(s) <NUM> with the valve springs <NUM>, <NUM> or spring retainers <NUM>, <NUM>.

Referring now to <FIG>, a third variation of a valve bridge guide <NUM> is illustrated in which the valve bridge guide <NUM> is once again formed as a unitary body, separate from the valve bridge <NUM>, having valve bridge control surfaces <NUM> formed on lateral sides thereof, as shown. In this embodiment, however, the valve bridge guide <NUM> has side openings <NUM> having cantilevered latches or catches <NUM> disposed therein. As shown, the catches <NUM> are configured to engage corresponding notches <NUM> formed in an outer sidewall surface of the portion <NUM> of the valve bridge <NUM>. For example, once again, the notches <NUM> may comprise an annular groove or channel formed in the sidewall of the portion <NUM> of the valve bridge <NUM>. When the catches <NUM> engage the notches <NUM>, the valve bridge guide <NUM> is once again operatively connected to the valve bridge <NUM> in relatively rigid fashion such that the valve bridge guide <NUM> and the valve bridge <NUM> move in unison. As shown, the valve bridge guide <NUM> may further comprise secondary latching surfaces <NUM> configured to engage corresponding secondary notches <NUM> formed in the portion <NUM> of the valve bridge <NUM>. By providing multiple latching pairs <NUM>, <NUM>/<NUM>, <NUM>, the stability of the valve bridge guide <NUM> relative to the valve bridge <NUM> may be improved.

Referring now to <FIG>, a fourth variation of a valve bridge guide <NUM> is shown. In this variation, the valve bridge guide <NUM> is a unitary body that is disposed between the spring retainers <NUM>, <NUM> and the valve bridge <NUM>. Notches <NUM>, <NUM> are provided to allow the valve bridge guide <NUM> to locate relative to the tips of the engine valves. Additionally, a central opening <NUM> may be provided that permits a portion of the valve bridge <NUM> (e.g., that portion housing the locking mechanism as shown in <FIG>) to extend through the valve bridge guide <NUM>. Similar to the embodiment of <FIG>, the valve bridge guide <NUM> comprises at least two protruding members in the form of side walls <NUM>, <NUM> that define a channel <NUM> that, in turn, is configured to receive the valve bridge <NUM>. In this embodiment, the inner surfaces <NUM>, <NUM> of the side walls <NUM>, <NUM>, which rise above the valve bridge <NUM>, serve as valve bridge controls surfaces that prevent lateral movement or rotation of the valve bridge <NUM> as may result during an uncontrolled state of the valve bridge <NUM>. Further, though not shown in <FIG>, additional valve bridge control surfaces <NUM> may be optionally provided on a lower portion <NUM> of the valve bridge guide <NUM> in order prevent tilting of the valve bridge <NUM>, as described above. To the extent that the valve bridge guide <NUM> is securely attached to the valve bridge <NUM> (using any of the above-described techniques), any excessive lift of the valve bridge <NUM> (e.g., off of the engine valve tips) will cause a similar lift in the valve bridge guide <NUM>, which again resists uncontrolled movement and permits the valve bridge <NUM> to once again settle back onto the engine valve tips.

Referring now to <FIG>, a fifth variation of a valve bridge guide <NUM> is substantially similar to the valve bridge guide <NUM> of <FIG> in that it comprises a unitary body, separate from the valve bridge <NUM>, having valve bridge control surfaces <NUM> formed on lateral sides thereof, as shown. As further shown, and similar to the second variation illustrate in <FIG>, this embodiment of the valve bridge guide <NUM> further comprises a plurality of protruding members <NUM>-<NUM> extending upwardly from the main body of the valve bridge guide <NUM>, which serve similar purposes as described above. Additionally, as shown, each of the protruding members <NUM>-<NUM> comprises an attachment surface <NUM>, <NUM> (only two shown in <FIG>) in the form of inwardly extending fingers <NUM>, <NUM> disposed at terminal ends of the protruding members <NUM>-<NUM>. The attachment surfaces thus defined are configured to engage a corresponding surface <NUM> of the valve bridge <NUM>, in this case, an upper surface of the valve bridge <NUM>. In this manner, the valve bridge guide <NUM> is retained on the valve bridge <NUM>. Alternatively, and similar to the embodiment of <FIG>, the fingers <NUM>, <NUM> may instead engage notches or similar features formed in lateral sides of the valve bridge <NUM>.

<FIG> illustrates a sixth variation of the first embodiment in which the valve bridge guide <NUM> is formed of two guide members <NUM>, <NUM> configured to engage opposite sides of a valve bridge. As in other embodiments, each of the guide members <NUM>, <NUM> defines a valve bridge control surface <NUM> as described above. Further, each of the guide members <NUM>, <NUM> defines a first opening <NUM> (only one shown) that is configured to receive the portion <NUM> of the valve bridge <NUM> (not shown). As further shown, each of the guide members <NUM>, <NUM> also includes a channel or second opening <NUM> configured to receive one of the arms of the valve bridge <NUM> (i.e., that portion of the valve bridge extending from the center of the valve bridge to one of the engine valves). Further still, each of the guide members <NUM>, <NUM> includes fasteners in the form of complementary first latches <NUM> and first latch notches <NUM> and second latches <NUM> and second latch notches <NUM> such that the guide members <NUM>, <NUM> may be securely connected to each other. Alternatively, any of the attachment mechanisms described above (dowel pins, epoxies, etc.) may be used as "fasteners" for this purpose. When connected, the guide members <NUM>, <NUM> collectively define the valve bridge guide <NUM> that is maintained in position relative to the valve bridge <NUM> by virtue of the fact that the second openings <NUM> encompass the arms of the valve bridge <NUM>.

<FIG> illustrate a seventh variation of the first primary embodiment in which a valve bridge guide <NUM> is formed as a stamped sheet metal structure having a horizontal surface <NUM> and a continuous sidewall <NUM> extending downwardly therefrom. In this variation, and similar to the embodiment illustrated in <FIG>, the valve bridge guide <NUM> is designed to rest on top of the spring retainers <NUM>, <NUM> (<FIG>) and beneath the valve bridge <NUM> (not shown). In <FIG>, the sidewall <NUM> is shown extending past the spring retainers <NUM>, <NUM> as well as initial portion of the valve springs <NUM>, <NUM>. In an embodiment, the extent of the sidewall <NUM> is such that the valve bridge guide <NUM> is unable to lift completely off of the spring retainers <NUM>, <NUM> despite any vertical displacement applied to the valve bridge <NUM>. In addition to a central opening <NUM> that permits passage of a portion of the valve bridge <NUM>, the valve bridge guide <NUM> also comprises a plurality of protruding members <NUM>-<NUM> (four shown in the illustrated example) similar to those illustrated in <FIG>, <FIG>. As shown, the protruding members <NUM>-<NUM> are formed as upwardly bent portions of the horizontal surface <NUM>, which results in openings <NUM>, <NUM> that permit passage of the tips of the engine valves <NUM>. In this case, the protruding members <NUM>-<NUM> once again define valve bridge control surfaces <NUM>, <NUM> for resisting uncontrolled movement of the valve bridge <NUM>.

<FIG> illustrates an isometric view of an eighth variation of the first primary embodiment in which the valve bridge guide <NUM> comprises a two guide members <NUM> (only one shown) that are configured to engage opposite sides of the valve bridge <NUM> (not shown). Each guide member <NUM> is formed as a stamped sheet metal structure having a horizontal surface <NUM> and a continuous sidewall <NUM> extending downwardly therefrom, similar to the embodiment of <FIG>, but configured to rest atop only a single spring retainer <NUM>. Once again, each guide member <NUM> comprises a plurality of protruding members <NUM>, <NUM> extending upwardly and a central opening <NUM> for passage of engine valve tips, where each of the protruding members <NUM>, <NUM> defines valve bridge control surfaces <NUM> for resisting uncontrolled movement of the valve bridge <NUM>.

Similar to the embodiment of <FIG>, the embodiment illustrated in <FIG> comprises a valve bridge guide <NUM> comprising a pair of guide members <NUM> configured to rest atop separate spring retainers <NUM>, <NUM>. Formed, in this case, from a moldable polymer, each guide member <NUM> comprise a horizontal surface <NUM> and a continuous sidewall <NUM> extending downwardly therefrom, similar to the embodiments of <FIG>, but configured to rest atop only a single spring retainer <NUM> as in the embodiment of <FIG>. Once again, each guide member <NUM> comprises a plurality of protruding members <NUM>, <NUM> extending upwardly and a central opening <NUM> for passage of engine valve tips, where each of the protruding members <NUM>, <NUM> defines valve bridge control surfaces <NUM> for resisting uncontrolled movement of the valve bridge <NUM>. In this case, however, each guide member <NUM> is also provided with lateral, concave valve bridge control surfaces <NUM> as described above. In this case, however, the lateral, concave valve bridge control surfaces <NUM> are not configured to conform to the outer surfaces of valve springs <NUM>, <NUM>, but to that portion of a the valve bridge <NUM> extending downwardly between the valve springs <NUM>, <NUM> and housing the locking mechanism, as described above relative to and illustrated <FIG>.

Referring now to <FIG>, a second primary embodiment not according to the appended claims is illustrated in which an internal combustion engine <NUM> comprises a pair of valve bridges <NUM>, <NUM> for a single cylinder. In the illustrated embodiment, each valve bridge <NUM>, <NUM> actuates two corresponding engine valves, though, once again, it is possible for each valve bridge to actuate more than two engine valves. In the illustrated embodiment, a first valve bridge <NUM> spans a pair of engine valves in a conventional manner as known in the art. Each engine valve has a valve spring <NUM>, <NUM> that biases its corresponding engine valve into a closed state and a valve spring retainer <NUM>, <NUM> attached to valve stems of the engine valves. As best shown in <FIG>, the valve bridge <NUM> comprises a lower surface <NUM> facing the engine valves and an upper surface <NUM> opposite the lower surface <NUM>.

As further shown in this second primary embodiment, the valve bridge system further comprises a valve bridge guide in the form of a first member <NUM> having a first surface <NUM> facing the upper surface <NUM> of the valve bridge <NUM>. Using a suitable fastener <NUM> (such as a bolt screwed into a cylinder head or similar fixed structure), the first member <NUM> is maintained in a first fixed position relative to the valve bridge <NUM>. In particular, the first fixed position maintains the first member <NUM> at a predetermined distance <NUM> away from the upper surface <NUM> of the valve bridge <NUM> when the at least two valve bridges <NUM>, <NUM> are maintained in a closed state. Additionally, as shown, the first fixed position of the first member <NUM> is aligned with a first engine valve of the at least two engine valves, where the first engine valve is farthest from a rocker shaft <NUM> of the internal combustion engine <NUM>. As shown, the first member <NUM> may be configured such that it is aligned with a first engine valve, as described, for more than one valve bridge <NUM>, <NUM>. Further still, the first member <NUM> may also extend in this manner across the valve bridges <NUM>, <NUM> for multiple cylinders of the internal combustion engine, or may comprise multiple such first members <NUM> where configuration of the cylinders prevents use of a single first member <NUM>.

In this embodiment, the predetermined distance <NUM> between the first member <NUM> and the upper surface <NUM> of the valve bridge <NUM> is preferably sufficient to prevent contact between the first surface <NUM> of the first member <NUM> and the upper surface <NUM> of the valve bridge <NUM> when the valve bridge <NUM> is in a controlled state relative to the at least two engine valves and sufficient to permit contact between the first surface <NUM> and the upper surface <NUM> to resist uncontrolled movement of the valve bridge <NUM> when the valve bridge <NUM> is in an uncontrolled state relative to the at least two engine valves. As used herein, uncontrolled movement of the valve bridge <NUM> is resisted to the extent that any of the disclosed valve bridge guides oppose movement of the valve bridge <NUM> outside its normal range of movement when operating in a controlled state. Thus, whereas the multiple variations of the first embodiment illustrated in <FIG> oppose movement that would result in tilting or rotation of the valve bridge <NUM> relative to engine valves, the first member <NUM> opposes excessive vertical displacement of the valve bridge <NUM> relative to the engine valves, particular to prevent complete disengagement of the valve bridge <NUM> from the engine valves. By defining the predetermined distance <NUM> relative to the closed position of the engine valves, contact between the valve bridge <NUM> and the first member <NUM> is avoiding during controlled operation of the valve bridge <NUM>. However, by further defining the predetermined distance <NUM> to nevertheless be sufficiently small, the desired resistance to uncontrolled movement of the valve bridge <NUM> may be provided. In one embodiment, the predetermined distance <NUM> may be based on a depth <NUM> of a receptacle <NUM> provided by the valve bridge <NUM>, <NUM> to engage valve tips <NUM> of the engine valves (<FIG>). In particular, the predetermined distance <NUM> may be chosen to be less than the depth <NUM> of the receptacle <NUM>. In this manner, the valve bridge <NUM>, <NUM>, if operating in an uncontrolled state, will make contact with the first member <NUM> before the valve bridge <NUM>, <NUM> can travel a distance exceeding the depth <NUM> of the receptacle <NUM>, which could otherwise result in disengagement of the valve bridge <NUM>, <NUM> from the valve tips <NUM>. Further still, it is known in some forms of engine brakes to actuate only a single, inboard engine valve (i.e., closest to the rocker shaft), which can cause that portion of the valve bridge <NUM> engaged with the outboard engine valve (i.e., farthest from the rocker shaft) to rise upwards slightly, for example, by about <NUM>-<NUM>. Thus, the predetermined distance <NUM> should be selected to accommodate this possibility to avoid undesired contact with the valve bridge <NUM>. Additionally, normal wear of engine valve seats could cause an upward rise, over time, of the engine valve tips <NUM>, and the predetermined distance <NUM> should account for this possibility as well.

In this second embodiment, the valve bridge guide may further comprise a second member <NUM> maintained in a second fixed position relative to the valve bridge <NUM> and having a second surface <NUM> facing the upper surface <NUM> of the valve bridge <NUM>. As with the first member <NUM>, the second surface <NUM> is maintained at the predetermined distance <NUM> away from the upper surface <NUM> for the same reasons described above. In an embodiment, the second fixed position of the second member <NUM> is in alignment with a second engine valve of the at least two engine valves, where the second engine valve is closest to the rocker shaft <NUM>. Further, as best shown in <FIG>, the second member <NUM> may be formed as a unitary structure with a rocker pedestal <NUM>. In this manner, the first and second members <NUM>, <NUM> may be separately aligned with different engine valves and at the same predetermined distance <NUM> from the upper surface <NUM>, thereby functioning as a valve bridge guide to provide uniform resistance to uncontrolled movement.

As known in the art, some valve actuation systems include auxiliary motion sources and valve trains that provide auxiliary motion to a single engine valve despite the presence of a valve bridge <NUM>. This is achieved through the use of bridge pin <NUM> that, as known in the art, permits auxiliary valve actuation motions to be applied to a single engine valve and main valve actuation motions to also be applied to the singe engine valve via the valve bridge <NUM>. In this case, the presence of the bridge pin <NUM>, which passes through the valve bridge <NUM>, effectively serves as the second member <NUM> defining a valve bridge guide. That is, if the valve bridge <NUM> is operated in an uncontrolled state, the presence of the bridge pin <NUM> (operatively connected to both an auxiliary rocker arm <NUM> and the single engine valve) will operate to constrain the valve bridge <NUM> to only sliding motion relative to the bridge pin <NUM>. In this case, the presence of the auxiliary rocker arm <NUM> (or other auxiliary valve train component) will operate to prevent travel of the valve bridge <NUM> off of the bridge pin <NUM>. Once again, where the first member <NUM> is provided (as shown in <FIG>), the joint operation of the first and second members <NUM>, <NUM> will resist uncontrolled movement, particularly upward movement, of the valve bridge <NUM>.

Finally, <FIG> illustrates a first variation of the second embodiment in which a valve bridge guide comprises a first member <NUM> formed as a three-sided arch or "strap. " Like the embodiment of <FIG>, the variation illustrate in <FIG> operates to resist uncontrolled movement by placing a first member <NUM> in a position to contact an upper surface <NUM> of the valve bridge <NUM>. In this embodiment, the first member <NUM> may comprise sheet metal or similar material having two, substantially vertical elongated sides <NUM> (one shown in <FIG>) extending from above the valve bridge <NUM> to the base of the engine valve springs <NUM>, <NUM> where each of the elongated sides <NUM> is mounted to the cylinder head <NUM>. Above the highest normal resting point of the valve bridge <NUM> (i.e., when the engine valves are fully closed) and the upper surface <NUM> of the valve bridge <NUM>, a third, substantially horizontal side <NUM> of the first member <NUM> connects the first and second elongated sides <NUM>. As with the embodiment of <FIG>, the third side <NUM> is preferably maintained in a fixed position at a predetermined distance <NUM> (not shown in <FIG>) away from the upper surface <NUM>. As further shown, the third side <NUM> includes an opening <NUM> that permits a portion of the valve bridge <NUM> (e.g., with reference to <FIG>, the outer plunger <NUM>/cap <NUM>) to contact a rocker arm <NUM>, as shown. In this variation, then, displacement of the valve bridge <NUM> is constrained by the third side <NUM> of the first member <NUM> and the opening <NUM> formed therein.

Claim 1:
A valve bridge system (<NUM>) for use with an engine valve assembly of an internal combustion engine, the engine valve assembly comprising at least two engine valves, at least two valve springs (<NUM>, <NUM>) corresponding to the at least two engine valves and at least two spring retainers (<NUM>, <NUM>) corresponding to the at least two engine valves, the valve bridge system comprising:
a valve bridge (<NUM>, <NUM>) configured to extend between the at least two engine valves; and
a valve bridge guide (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) operatively connected to the valve bridge and comprising a valve bridge control surface (<NUM>) configured to selectively contact at least one of the valve bridge or the engine valve assembly,
wherein the valve bridge guide is configured to extend downward between the at least two valve springs,
characterised in that
the valve bridge control surface is at least one concave surface corresponding to at least one convex surface defined by the at least two valve springs or the at least two spring retainers,
wherein the valve bridge control surface is configured to be as close as possible to one or more of the at least two valve springs or the at least two spring retainers such that normal movement and vibration of the valve bridge, valve bridge guide and at least two valve springs does not result in contact between the valve bridge control surface and the springs or spring retainers of the engine valve assembly when the valve bridge is in a controlled state relative to the at least two engine valves,
and wherein the valve bridge control surface is configured to contact the at least one of the springs or spring retainers of the engine valve assembly to resist uncontrolled movement of the valve bridge when the valve bridge is in an uncontrolled state relative to the at least two engine valves.