Valve bridge system to resist uncontrolled movement of the valve bridge

Abstract

To provide valve bridge systems that prevent, minimize or accommodate uncontrolled states of valve bridges.SOLUTION: A valve bridge system comprises a valve bridge body configured to extend between at least two engine valves of an internal combustion engine. The valve bridge body comprises a through-bore configured to align with a first engine valve and to receive a bridge pin. A bridge pin boss has the through-bore formed therein, has a longitudinal length, and terminates in an upper surface. The longitudinal length is configured such that the upper surface of the bridge pin boss contacts a surface of the auxiliary rocker arm 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.SELECTED DRAWING: Figure 24

Description

[Technical Field]

[0001] The present disclosure relates generally to valve actuation systems for internal combustion engines, and more particularly to valve bridge systems including valve bridge guides for use in conjunction with such valve actuation systems. [Background technology]

[0002] Valve actuation systems for use in internal combustion engines are well known in the art. Such valve actuation systems typically include a valve train comprising one or more components that transmit valve actuation motion from a valve actuation motion source (e.g., one or more cams) to the engine valves. A common component found in a valve train is a so-called valve bridge, which comprises a device that spans two or more engine valves associated with a given cylinder. Often, such a valve bridge allows another valve train component (e.g., a rocker arm) to simultaneously operate two additional engine valves that engage the valve bridge. Ideally, during operation, opposing forces exerted by the motion-transmitting component (e.g., a rocker arm) and the engine valve springs ensure that the valve bridge remains in contact (allowing for normal lash settings) with the motion-transmitting component and the engine valve simultaneously. In this way, the valve bridge is positioned to consistently maintain alignment with the engine valves and transmit valve actuation motion to the engine valves. As used herein, this state of the valve bridge is referred to as the "controlled state" of the valve bridge relative to the engine valves.

[0003] Some valve actuation systems are configured to provide so-called auxiliary valve actuation motion, i.e., valve actuation motion other than or in addition to that used to operate the engine in a positive power-producing mode through the combustion of fuel. In such valve actuation systems, the valve bridge may be configured to include a device or lost motion assembly that allows valve actuation motion to be transmitted through the valve bridge to the engine valves, or to be selectively “lost” when such motion is not transmitted through the valve bridge to the engine valves. FIG. 1 illustrates such a system, as described in U.S. Patent Application Publication No. 2012 / 0024260, the teachings of which are incorporated herein by reference. In this case, the valve bridge 710 includes a lost motion assembly in the form of a locking mechanism. In the illustrated embodiment, the locking mechanism includes a ball 740 that can be pushed through an opening in an outer plunger 720 and engage a recess 770 formed in the body of the valve bridge. In this state, the ball 740 is prevented from disengaging from the recess 770 due to the outer diameter of the inner plunger 760, thereby locking the outer plunger 720 in a fixed relationship relative to the valve bridge 710. As a result, any valve actuation motion applied to the outer plunger 720 by the rocker arm 200 / 400 is transmitted to the valve bridge 710 and the engine valves 810 / 910, 820 / 920. However, when the recess formed in the inner plunger 760 aligns with the ball 740, the ball can disengage from the recess 770 in the valve bridge 710, thereby unlocking the outer plunger 720 and allowing it to reciprocate relative to the valve bridge 710. In this state, any valve actuation motion applied to the outer plunger 720 moves the outer plunger within the valve bridge 710 and is not transmitted to the engine valves. Another valve bridge based locking / unlocking system is disclosed in U.S. Patent Application Publication No. 2014 / 0326212, the teachings of which are incorporated herein by reference.

[0004] However, in systems of the type illustrated in FIG. 1 , the possibility exists for the locking mechanism to partially engage. In this case, valve actuation motion is initially applied to the engine valve, allowing the engine valve to lift from its valve seat. However, with the locking mechanism partially engaged, an increase in load or vibration in the valve actuation system can cause the locking mechanism to rapidly switch from a partially locked state to an unlocked state. When this occurs, the force provided by the valve actuation motion to open the engine valve is suddenly removed, allowing the engine valve to rapidly accelerate to a closed position without being constrained under the considerable force of the valve spring. Once the engine valve reaches a fully closed position (i.e., stops against the valve seat formed in the cylinder head), the momentum applied to the valve bridge allows the valve bridge to continue on an uncontrolled trajectory generally away from the engine valve until it strikes a rocker arm or some other object. In fact, it is possible for the valve bridge to detach from either end of the engine valve, resulting in the valve bridge falling off the engine valve and thereby causing engine damage. This type of movement is referred to as "uncontrolled movement" of the 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 valve. Uncontrolled states of the valve bridge are also known to occur as a result of overspeed operation of an internal combustion engine.

[0005] Given this potential for malfunction, a solution that prevents, minimizes, or accommodates uncontrolled valve bridge conditions (regardless of cause) would represent a welcome addition to the art. Summary of the Invention

[0006] This disclosure describes a valve bridge system that overcomes the above-mentioned problems associated with prior art valve bridge systems. In a first principal embodiment, the valve bridge system includes a valve bridge configured to extend between at least two engine valves of an internal combustion engine. A valve bridge guide is operably connected to the valve bridge and includes a valve bridge control surface for selectively contacting at least one of the valve bridge or engine valve assembly (including 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 of a moldable polymer. The valve bridge control surface is configured to avoid contact with the valve bridge or engine valve assembly when the valve bridge is in a controlled state for the at least two engine valves, and further configured to contact the valve bridge or engine valve assembly to resist uncontrolled movement of the valve bridge when the valve bridge is in an uncontrolled state for the at least two engine valves. In one embodiment, the valve bridge guide is configured to extend between at least two valve springs, and 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 at least two spring retainers or a convex surface defined by a portion of the valve bridge. More specifically, each of the at least one concave surface may be defined by edges such that a line intersecting the edges forms a secant with respect to an outer diameter of a corresponding one of the at least two valve springs or at least two spring retainers.

[0007] The valve bridge guide and the valve bridge may form a unitary structure, or the valve bridge guide may comprise one or more separate components operably connected to the valve bridge. In one embodiment, the valve bridge guide may comprise two guide members configured to engage opposite sides of the valve bridge and may further comprise at least one fastener for operably coupling the two guide members together. The valve bridge guide may comprise an opening for receiving at least a portion of the valve bridge and may further comprise at least two protruding members, each of which protrudes from the valve bridge guide toward the valve bridge and extends beyond at least a lower surface of the valve bridge facing the at least two engine valves. Furthermore, the at least two protruding members may define a valve bridge control surface. Alternatively, each of the at least two protruding members may comprise a mounting surface for engaging a corresponding surface of the valve bridge.

[0008] In a second main embodiment, a valve bridge system may include a valve bridge configured to extend between at least two engine valves of an internal combustion engine, the valve bridge including a lower surface facing the at least two engine valves and an upper surface opposite the lower surface. The system of this main embodiment further includes a valve bridge guide having a first member maintained in a first fixed position relative to the valve bridge, the first member including a first surface facing the upper surface of the valve bridge when the at least two engine valves are in a closed state and at a predetermined distance from the upper surface of the valve bridge. 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 for the at least two engine valves and to allow 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 for the at least two engine valves. If the valve bridge includes a receptacle for receiving 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.

[0009] The first fixed position of the first member may be aligned with a first engine valve of the at least two engine valves, the first engine valve being furthest from a rocker shaft of the internal combustion engine. The valve bridge system may further include a second member maintained at a second fixed position relative to the valve bridge, the second member having a second surface facing an upper surface of the valve bridge and at a predetermined distance from the upper surface of the valve bridge. In this case, the second fixed position of the second member is aligned with a second engine valve of the at least two engine valves, the second engine valve being closest to the rocker shaft of the internal combustion engine. The first member may be configured to be attached to a cylinder head of the internal combustion engine, while the second member may form an integral structure with a rocker shaft pedestal of the internal combustion engine.

[0010] In a further alternative of this second main embodiment, the valve bridge guide may further include a bridge pin disposed at one end of the valve bridge and aligned with an engine valve of the at least two engine valves. Alternatively, the first member of the valve bridge guide in this embodiment may include an arch configured to be attached to the cylinder head and extending between the at least two engine valves and over an upper surface of the valve bridge, the arch further including an opening formed therein that aligns with a portion of the valve bridge that contacts a valve train component. [Brief explanation of the drawings]

[0011] The features described in the present disclosure are set forth with particularity in the appended claims. These features and attendant advantages will become apparent from a consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which: One or more embodiments are now described, by way of example only, with reference to the accompanying drawings in which like reference numerals represent like elements and in which: [Figure 1] 1 is a cross-sectional illustrative view of a valve actuation system including a valve bridge with a locking mechanism according to the prior art; [Figure 2]1A-1C are top and bottom isometric cross-sectional views, respectively, of a first primary embodiment of a valve actuation system including a valve bridge and a valve bridge guide according to the present disclosure. [Figure 3] 1A-1C are top and bottom isometric cross-sectional views, respectively, of a first primary embodiment of a valve actuation system including a valve bridge and a valve bridge guide according to the present disclosure. [Figure 4] FIG. 10 is a schematic diagram illustrating the relationship between the valve spring and the surface of the valve bridge guide according to the first main embodiment. [Figure 5] 6A and 6B are an isometric view and a cross-sectional view (along section line VI-VI), respectively, of a valve bridge and a valve bridge guide according to a first variant of the first main embodiment. [Figure 6] 6A and 6B are an isometric view and a cross-sectional view (along section line VI-VI), respectively, of a valve bridge and a valve bridge guide according to a first variant of the first main embodiment. [Figure 7] 8A-8C are an isometric view and a cross-sectional view (along section line VIII-VIII), respectively, of a valve bridge and a valve bridge guide according to a second variant of the first main embodiment. [Figure 8] 8A-8C are an isometric view and a cross-sectional view (along section line VIII-VIII), respectively, of a valve bridge and a valve bridge guide according to a second variant of the first main embodiment. [Figure 9] 10A and 10B are an isometric view and a cross-sectional view (along section line XX) of a valve bridge and a valve bridge guide according to a third variant of the first main embodiment, respectively. [Figure 10] 10A and 10B are an isometric view and a cross-sectional view (along section line XX) of a valve bridge and a valve bridge guide according to a third variant of the first main embodiment, respectively. [Figure 11] FIG. 10 is an isometric view of a valve bridge guide according to a fourth variant of the first main embodiment. [Figure 12] FIG. 10 is an isometric view of a valve bridge and valve bridge guide according to a fifth variant of the first main embodiment. [Figure 13]FIG. 10 is an isometric view of a valve bridge guide according to a sixth variant of the first main embodiment. [Figure 14] 13A and 13B are an isometric view and a cross-sectional view, respectively, of a valve bridge guide according to a seventh variant of the first main embodiment. [Figure 15] 13A and 13B are an isometric view and a cross-sectional view, respectively, of a valve bridge guide according to a seventh variant of the first main embodiment. [Figure 16] FIG. 13 is an isometric view of a valve bridge guide according to an eighth variant of the first main embodiment. [Figure 17] FIG. 13 is an isometric view of a valve bridge guide according to a ninth variant of the first main embodiment. [Figure 18] 10A-10C are isometric, side, and front views, respectively, of a valve bridge and valve bridge guide according to the second main embodiment. [Figure 19] 10A-10C are isometric, side, and front views, respectively, of a valve bridge and valve bridge guide according to the second main embodiment. [Figure 20] 10A-10C are isometric, side, and front views, respectively, of a valve bridge and valve bridge guide according to the second main embodiment. [Figure 21] 10A-10C are isometric, side, and front views, respectively, of a valve bridge and valve bridge guide according to the second main embodiment. [Figure 22] FIG. 10 is a top isometric view of a valve bridge and valve bridge guide according to a first variant of the second main embodiment. [Figure 23] FIG. 1 is a cross-sectional view of a valve bridge according to a prior art technique. [Figure 24] FIG. 10 is a cross-sectional view of a valve bridge according to the third main embodiment. [Figure 25] FIG. 10 is a cross-sectional view of a valve bridge according to the fourth to sixth main embodiments. [Figure 26] 10A-10C are top, isometric, and cross-sectional views, respectively, of a valve bridge according to the seventh main embodiment. [Figure 27]10A-10C are top, isometric, and cross-sectional views, respectively, of a valve bridge according to the seventh main embodiment. [Figure 28] 10A-10C are top, isometric, and cross-sectional views, respectively, of a valve bridge according to the seventh main embodiment. [Figure 29] FIG. 13 is a side view of a valve bridge according to the eighth main embodiment. [Figure 30] 13A-13C are isometric and cross-sectional views, respectively, of a valve bridge and bridge pin according to the ninth main embodiment. [Figure 31] 13A-13C are isometric and cross-sectional views, respectively, of a valve bridge and bridge pin according to the ninth main embodiment. [Figure 32] 1 is a side partial cross-sectional view of a valve actuation system according to prior art techniques; [Figure 33] FIG. 19 is a top isometric view of a valve actuation system according to a tenth embodiment. [Figure 34] 19A-19C are top and bottom isometric views, respectively, of a valve bridge and valve bridge guide according to an eleventh embodiment. [Figure 35] 19A-19C are top and bottom isometric views, respectively, of a valve bridge and valve bridge guide according to an eleventh embodiment. [Figure 36] FIG. 36 is a top isometric view of the valve bridge and valve bridge guide of FIGS. 34 and 35 deployed into a valve actuation system. DETAILED DESCRIPTION OF THE INVENTION

[0012] Figures 2-36 illustrate various embodiments of valve bridge systems including valve bridge guides according to the present disclosure. In all of the embodiments and variations illustrated in Figures 2-36, it is assumed that the valve bridge is of the type illustrated in Figure 1, i.e., a valve bridge having a locking mechanism of the general type illustrated in Figure 1 and described above.

[0013] 2 illustrates a first embodiment according to the present disclosure in which an internal combustion engine 202 includes a pair of valve bridges 204, 212 for a single cylinder. In the illustrated embodiment, each valve bridge 204, 212 actuates two corresponding engine valves, although it is possible for each valve bridge to actuate more than two engine valves. As is known in the art, each valve bridge 204, 212 (or any of the other valve bridges illustrated and described herein) may actuate two engine valves of the same type, i.e., two intake valves or two exhaust valves. For ease of illustration, the features and operation of only a first valve actuation system according to the first embodiment will be described, with the understanding that the described features and operation are equally applicable to all valve bridges included in an internal combustion engine.

[0014] Thus, as shown, a first valve bridge 204 spans a pair of engine valves (not visible in FIG. 2 ) in a conventional manner known in the art. Each engine valve has a valve spring 208, 210 that biases its corresponding engine valve to a closed position (i.e., with the engine valve head engaged with a valve seat formed in a cylinder head 230), and a valve spring retainer 209, 211 attached to the valve stem of the engine valve. As further shown, the valve bridge system 202 further includes a valve bridge guide 206 that extends downward (i.e., toward the cylinder head, away from the rocker arm 220) from the valve bridge 204 and between the valve springs 208, 210. In one embodiment, the distance that the valve bridge guide 206 extends between the valve springs 208, 219 is minimally defined by that portion of the valve bridge 204 that surrounds the locking mechanism (e.g., with reference to FIG. 1 , the depth of that portion of the valve bridge that houses the outer plunger 720 and outer plunger spring 746). In the embodiment illustrated in FIG. 2 , the valve bridge and valve bridge guide form a unitary structure, i.e., an undivided whole, whereby the locking mechanism is housed within an opening (best shown in FIG. 3 ) formed in the valve bridge 204 and valve bridge guide 206. As described in more detail below, the valve bridge guide 206 includes at least one valve bridge control surface configured to interact with one or both of the valve springs 208, 210 or valve spring retainers 209, 211 to prevent, minimize, or at least accommodate uncontrolled movement of the valve bridge 204.

[0015] FIG. 3 illustrates a cross-sectional view of the valve spring guide 206 and first valve spring 208 taken along section line III-III (as shown in FIG. 2). An opening 310 for accommodating a locking mechanism is formed in the valve spring guide 206, and FIG. 3 further illustrates a valve stem 320 disposed within the corresponding valve spring 208. More specifically, FIG. 3 illustrates two valve bridge control surfaces 402 defined by the valve bridge guide 206 such that the valve bridge control surfaces 402 conform to the corresponding valve springs 306 (only one is shown in FIG. 3), i.e., the valve bridge control surfaces 402 are concave relative to the convex outer surfaces of the valve springs 208, 210. While conforming, the valve bridge control surfaces 402 are configured such that the valve bridge control surfaces 402 (and therefore the valve bridge guide 206) can avoid contact with their corresponding valve springs 208, 210 during controlled states of the valve bridge. The valve bridge control surface 402 may be configured to be as close as possible to the valve springs 208, 210 (within manufacturing tolerances) so that normal movement and vibration of the valve bridge 204, valve bridge guide 206, and valve springs 208, 210 is insufficient to cause contact between the valve bridge control surface 402 and the valve springs 208, 210. For example, as is known in the art, when a compression spring, such as the valve springs 208, 210, deforms (i.e., is compressed), the outer diameter of the spring increases slightly. Thus, the valve bridge control surface 402 may be configured to account for the maximum expected change in spring diameter while remaining as close as possible to the valve springs 208, 210.

[0016] In some cases, it may be undesirable for the valve bridge guide 206 to contact the valve springs 208, 210, as doing so could lead to premature deterioration of the valve springs 208, 210. Therefore, it may be desirable to configure the valve bridge control surface 402 to contact the spring retainers 209, 211 instead. To achieve this configuration, the spring retainers 209, 211 may need to be dimensioned to have an outer diameter that is larger than the outer diameter of the valve springs 208, 210. In this case, the valve bridge control surface 402 is instead defined by the valve bridge guide 206 such that the valve bridge control surface 402 fits into the corresponding spring retainer 209, 211, i.e., the valve bridge control surface 402 is concave relative to the convex outer surface of the spring retainer 209, 211. Again, such concavities are configured to enable the valve bridge control surfaces 402 to avoid contact with their corresponding spring retainers 209, 211 during controlled states of the valve bridge, and further configured to be as close as possible (within manufacturing tolerances) to the valve springs 208, 210 so that normal movement and vibration of the valve bridge 204, valve bridge guide 206, and valve springs 208, 210 is insufficient to cause contact between the valve bridge control surfaces 402 and the spring retainers 209, 211.

[0017] While the various figures illustrated and described in this disclosure show at least two concave valve bridge control surfaces 402, this is not necessarily a requirement. For example, a single such valve bridge control surface 402 may be employed when used in conjunction with another feature that provides additional control of otherwise uncontrolled movement of the valve bridge 204. For example, if the valve bridge 204 includes a bridge pin (see, e.g., element 2102 in FIG. 21), then a single valve bridge control surface 402 and bridge pin combination may be sufficient.

[0018] The configuration of the valve bridge control surface 402 according to a preferred embodiment is further described in connection with FIG. 4, which schematically illustrates the valve bridge guide 206 and valve spring 208 in enlarged form. (Alternatively, as explained above, the valve spring 208 illustrated in FIG. 4 can be considered a spring retainer, although for ease of explanation, only the valve spring 208 is described herein.) As shown, the valve bridge guide 206 includes a concave valve bridge control surface 402 adjacent to the outer diameter 408 of the valve spring 208. In practice, the clearance between the valve bridge control surface 402 and the outer diameter 408 is based in part on the manufacturing tolerances of the valve springs 208, 210 (or spring retainers 209, 211) and the valve bridge 204. This clearance is further based on the clearance of the engine valve tip within a receptacle formed in the valve bridge 204 to receive the engine valve tip. For example, if the valve bridge 204 is allowed to move ±0.25 mm, then the clearance between the valve spring 208 and the valve bridge control surface 402 must be greater than the 0.25 mm of play allowed for component tolerances. Additionally, the chamfer at the bottom of the valve bridge 204 must be large enough to allow the valve bridge 204 to reposition itself over the tip of the engine valve, even if the valve bridge 204 experiences uncontrolled movement across its full clearance to the valve spring or spring retainer.

[0019] 4, the circumferential extent of the concave valve bridge control surface 402 (relative to the outer diameter 408 of the spring 208) is defined by edges 404, 406. In this preferred embodiment, the edges 404, 406 are spaced apart such that when the valve bridge guide 206 is positioned during a controlled state of the valve bridge 204, a line 410 intersecting the edges 404, 406 forms a secant with at least the outer diameter 408 of the valve spring 208, as shown. Configured in this manner, it will be appreciated that movement of the valve bridge guide 206 in either direction indicated by line 410 (such as may occur during an uncontrolled state of the valve bridge 204), if large enough, will bring the concave valve bridge control surface 402 into contact with the outer diameter 408 of the spring, thereby generally deflecting the valve bridge guide 206 away from the valve spring 208 and toward the other valve spring 210. More generally, any rotational movement of the valve bridge 204 about the locking mechanism's centerline axis is constrained, as is lateral movement in both horizontal planes. With this in mind, and returning to reference to Figures 2 and 3, this movement of the concave valve bridge control surface 402 during the uncontrolled state of the valve bridge 204 tends to realign the valve bridge guide 206 itself with the valve springs 208, 210, thereby effectively damping or even eliminating uncontrolled movement of the valve bridge 204 and valve bridge guide 206.

[0020] 5 and 6, a first variation of the valve bridge guide 502 comprises a single piece separate from the valve bridge 204, as shown, with the valve bridge control surface 402 formed on its side. The valve bridge 204 is also illustrated as having a receptacle 614 for receiving the tip of the valve stem of an engine valve, as known in the art and described above. In this embodiment (as well as additional embodiments illustrated in FIGS. 7-13), the valve bridge guide 502 may be manufactured from the same material (e.g., steel) as the valve bridge 204; however, in preferred embodiments, the valve bridge guide 502 is formed from a softer, yet lighter, stronger material than the valve bridge springs 208, 201 (or spring retainers 209, 211) to avoid scratching or damage. For example, a suitable moldable polymer, as known in the art, may be used for this purpose. Still additional types of materials for manufacturing valve bridge guides will be apparent to those skilled in the art.

[0021] Regardless, as further shown, the valve bridge guide 502 has an opening or bore 602 formed therein that is configured to snugly receive a portion 604 of the valve bridge 204. As shown, the portion 604 of the valve bridge 204 that is received by the valve bridge guide 502 preferably houses at least a portion of a locking mechanism 606. As further shown, in this embodiment, both the valve bridge guide 502 and the portion 604 of the valve bridge 204 include fastener receiving features 504, 608. In this embodiment, the fastener receiving feature 504 of the valve bridge guide comprises a bore that intersects with the opening 602 formed in the valve bridge guide 502. Thus, where the bore intersects the opening 602, the fastener receiving feature 504 essentially comprises a channel having a semicircular cross-section formed in the sidewall of the opening 602. In a complementary manner, the fastener receiving feature 608 of the portion 604 of the valve bridge 204 is also formed as a semicircular channel in the outer wall of the portion 604. When aligned, these respective fastener-receiving features 504, 608 can receive fasteners 610, 612 such that the valve bridge guide 502 is operably connected to the portion 604 of the valve bridge 204. For example, in the illustrated embodiment, the fasteners 612 may comprise split dowel pins as shown, although those skilled in the art will recognize that other types of fasteners, such as screws, could equally be employed. In this manner, the valve bridge guide 502 is relatively rigidly attached to the valve bridge 204 so that they move in unison. As an alternative to the fastener embodiments described above, the valve bridge guide 502 (or other embodiments of the valve bridge guide illustrated in FIGS. 7-13) could instead be fixedly attached to the valve bridge 204 using a suitably strong and durable epoxy or similar adhesive. Furthermore, a combination of such techniques could also be employed as a design option.

[0022] 7 and 8, a second variation of a valve bridge guide 702 is substantially similar to the valve bridge guide 502 of FIGS. 5 and 6 in that it comprises a unitary body separate from the valve bridge 204, with the valve bridge control surface 402 formed on its side, as shown. However, in this embodiment, the valve bridge guide 702 comprises one or more teeth 802 extending inwardly from the sidewall surface of the opening 602 and configured to engage with a notch 804 formed in the outer sidewall surface of the portion 604 of the valve bridge 204. For example, the notch 804 may comprise an annular groove or channel formed in the sidewall of the portion 604 of the valve bridge 204. When the teeth 802 engage the notch 804, the valve bridge guide 702 is again operably connected to the valve bridge in a relatively rigid manner such that the valve bridge guide 702 and the valve bridge 204 move in unison. It should be noted that in this embodiment, the arrangement of one or more teeth 802 and notches 804 can equally be reversed, i.e., teeth 802 can be formed on the outer sidewall surface of portion 604 of valve bridge 204, and notches 804 can be formed on the inner sidewall surface of opening 602.

[0023] As further shown in Figure 7, the valve bridge guide 702 may include at least two protruding members 704, 706 that protrude from the valve bridge guide 702 toward the valve bridge 204. As shown in Figure 8, the valve bridge 204 has a lower surface 806, and in one embodiment, the protruding members 704, 706 extend at least beyond the lower surface 806 of the valve bridge 204. In this embodiment, the at least two protruding members 704, 706 help to orient the valve bridge guide 702 on the valve bridge 204, thereby preventing rotation of the valve bridge 204 relative to the valve bridge guide 702. In this manner, the at least two protruding members 704, 706 further help to align the valve bridge control surface 402 with the valve springs 208, 210 or spring retainers 209, 211.

[0024] 9 and 10 , a third variation of the valve bridge guide 902 is illustrated; as shown, the valve bridge guide 902 is again formed as a separate, unitary piece from the valve bridge 204, with the valve bridge control surface 402 formed on its side. However, in this embodiment, the valve bridge guide 902 has a side opening 904 with a cantilevered latch or catch 906 disposed therein. As shown, the catch 906 is configured to engage with a corresponding notch 1002 formed in the outer sidewall surface of the portion 604 of the valve bridge 204. For example, the notch 1002 may again comprise an annular groove or channel formed in the sidewall of the portion 604 of the valve bridge 204. When the catch 906 engages the notch 804, the valve bridge guide 702 is again operably connected to the valve bridge in a relatively rigid manner, such that the valve bridge guide 902 and the valve bridge 204 move in unison. As shown, the valve bridge guide 902 may further include a secondary latch surface 908 configured to engage a corresponding secondary notch 1004 formed in the portion 604 of the valve bridge 204. By providing multiple latch pairs 906, 1002 / 908, 1004, the stability of the valve bridge guide 902 relative to the valve bridge 204 may be improved.

[0025] Referring now to FIG. 11 , a fourth variation of the valve bridge guide 1102 is shown. In this variation, the valve bridge guide 1102 is a single piece disposed between the spring retainers 209, 211 and the valve bridge 204. Notches 1104, 1106 are provided to allow the valve bridge guide 1102 to position against the tip of the engine valve. Additionally, a central opening 1107 may be provided to allow a portion of the valve bridge 204 (e.g., the portion housing the locking mechanism as shown in FIG. 1 ) to extend through the valve guide 1102. Similar to the embodiment of FIGS. 7 and 8 , the valve bridge guide 1102 includes at least two protruding members in the form of sidewalls 1108, 1110 that define a channel 1116 configured to receive the valve bridge 204. In this embodiment, the inner surfaces 1112, 1114 of the upwardly rising sidewalls 1108, 1110 of the valve bridge 204 function as valve bridge control surfaces that prevent lateral movement or rotation of the valve bridge 204 that may occur during an uncontrolled state of the valve bridge 204. Furthermore, although not shown in FIG. 11 , an additional valve bridge control surface 402 may optionally be provided on the lower portion 1118 of the valve bridge guide 1102 to prevent tilting of the valve bridge 204, as described above. As long as the valve bridge guide 1102 is fixedly attached to the valve bridge 204 (using any of the techniques described above), excessive lifting of the valve bridge 204 (e.g., moving off the tip of the engine valve) will cause a similar lifting in the valve bridge guide 1102, which again resists uncontrolled movement and allows the valve bridge 204 to settle back onto the tip of the engine valve.

[0026] 12, a fifth variation of a valve bridge guide 1202 is substantially similar to the valve bridge guide 502 of FIGS. 5 and 6 in that it comprises a unitary body separate from the valve bridge 204, having the valve bridge control surface 402 formed on its side, as shown. As further shown, and similar to the second variation illustrated in FIGS. 7 and 8, this embodiment of the valve bridge guide 1202 further comprises a plurality of protruding members 1204-1212 extending upwardly from the body of the valve bridge guide 1202, which serve the same purpose as described above. Furthermore, as shown, each of the protruding members 1204-1212 comprises a mounting surface 1214, 1216 in the form of inwardly extending fingers 1214, 1216 (only two are shown in FIG. 12) disposed at the distal end of the protruding member 1204-1212. The mounting surface thus defined is configured to engage a corresponding surface 1220 of the valve bridge 204, in this case the top surface of the valve bridge 204. In this way, the valve bridge guide 1202 is retained on the valve bridge 204. Alternatively, similar to the embodiment of Figures 9 and 10, the fingers 1214, 1216 may instead engage with notches or similar features formed in the side of the valve bridge 204.

[0027] 13 illustrates a sixth variation of the first embodiment in which a valve bridge guide 1302 is formed from two guide members 1304, 1306 configured to engage opposite sides of the valve bridge. As with the other embodiments, each of the guide members 1304, 1306 defines a valve bridge control surface 402 as described above. Additionally, each of the guide members 1304, 1306 defines a first opening 1308 (only one shown) configured to receive a portion 604 of the valve bridge 204 (not shown). As further shown, each of the guide members 1304, 1306 also includes a channel or second opening 1310 configured to receive one of the arms of the valve bridge 204 (i.e., that portion of the valve bridge that extends from the center of the valve bridge to one of the engine valves). Additionally, each of the guide members 1304, 1306 includes fasteners in the form of complementary first latch 1312 and first latch notch 1314 and second latch 1316 and second latch notch 1318 such that the guide members 1304, 1306 may be fixedly connected to one another. Alternatively, any of the attachment mechanisms described above (dowel pins, epoxy, etc.) may be used as "fasteners" for this purpose. When connected, the guide members 1304, 1306 collectively define a valve bridge guide 1302 that is maintained in position relative to the valve bridge 204 by the fact that the second opening 1310 encompasses an arm of the valve bridge 204.

[0028] 14 and 15 illustrate a seventh variation of the first main embodiment in which the valve bridge guide 1402 is formed as a stamped sheet metal structure having a horizontal surface 1404 and a continuous sidewall 1406 extending downwardly therefrom. In this variation, similar to the embodiment illustrated in FIG. 11, the valve bridge guide 1402 is designed to rest above the spring retainers 209, 211 ( FIG. 15 ) and below the valve bridge 204 (not shown). In FIG. 15 , the sidewall 1406 is shown extending beyond the spring retainers 209, 211 and the initial portions of the valve springs 208, 210. In one embodiment, the extent of the sidewall 1406 is such that the valve bridge guide 1402 cannot lift completely off the spring retainers 209, 211, even when vertical displacement is applied to the valve bridge 204. In addition to the central opening 1406 that allows passage of a portion of the valve bridge 204, the valve bridge guide 1402 also includes a plurality of protruding members 1408-1416 (four are shown in the illustrated example) similar to those illustrated in Figures 7, 8, 11, and 12. As shown, the protruding members 1408-1416 are formed as upwardly curved portions of the horizontal surface 1404, resulting in openings 1426, 1428 that allow passage of the tips of the engine valves 1502. In this case, the protruding members 1408-1416 again define valve bridge control surfaces 1422, 1424 to resist uncontrolled movement of the valve bridge 204.

[0029] Figure 16 illustrates an isometric view of an eighth variation of the first main embodiment in which a valve bridge guide 1602 includes two guide members 1603 (only one shown) configured to engage opposite sides of a valve bridge 204 (not shown). Each guide member 1603 is formed as a stamped sheet metal structure having a horizontal surface 1604 and a continuous sidewall 1606 extending downwardly therefrom, similar to the embodiment of Figures 14 and 15, but is configured to rest on only a single spring retainer 209. Again, each guide member 1603 includes a plurality of upwardly extending protruding members 1608, 1610 and a central opening 1612 for passage of the tip of an engine valve, with each of the protruding members 1608, 1610 defining a valve bridge control surface 1614 for resisting uncontrolled movement of the valve bridge 204.

[0030] Like the embodiment of FIG. 16 , the embodiment illustrated in FIG. 17 includes a valve bridge guide 1702 including a pair of guide members 1703 configured to rest on separate spring retainers 209, 211. In this case, formed from a moldable polymer, each guide member 1703 includes a horizontal surface 1704 and a continuous sidewall 1706 extending downwardly therefrom, similar to the embodiments of FIGS. 14 and 15 , but is configured to rest on only a single spring retainer 209, as in the embodiment of FIG. 16 . Again, each guide member 1603 includes a plurality of upwardly extending protruding members 1708, 1710 and a central opening 1712 for passage of the tip of an engine valve, each of the protruding members 1708, 1710 defining a valve bridge control surface 1614 for resisting uncontrolled movement of the valve bridge 204. However, in this case, each guide member 1703 is also provided with a lateral concave valve bridge control surface 402, as described above. In this case, however, the transverse concave valve bridge control surface 402 is not configured to fit against the outer surfaces of the valve springs 208, 210, but rather against that portion of the valve bridge 204 that extends downwardly between the valve springs 208, 210 and houses the locking mechanism, as described and illustrated above in connection with FIG. 1.

[0031] 18-21, a second primary embodiment according to the present disclosure is illustrated, in which an internal combustion engine 202 includes a pair of valve bridges 204, 212 for a single cylinder. In the illustrated embodiment, each valve bridge 204, 212 operates two corresponding engine valves, although each valve bridge can operate three or more engine valves. In the illustrated embodiment, a first valve bridge 204 spans a pair of engine valves in a conventional manner known in the art. Each engine valve has a valve spring 208, 210 that biases the corresponding engine valve closed, and a valve spring retainer 209, 211 attached to the valve stem of the engine valve. As best shown in FIG. 19, the valve bridge 204 includes a lower surface 1902 facing the engine valve and an upper surface 1904 opposite the lower surface 1902.

[0032] As further shown in this second main embodiment, the valve bridge system further includes a valve bridge guide in the form of a first member 1802 having a first surface 1906 facing the top surface of the valve bridge 204. Using suitable fasteners 1806 (such as bolts threaded into a cylinder head or similar fixed structure), the first member 1802 is maintained in a first fixed position relative to the valve bridge 204. In particular, the first fixed position maintains the first member a predetermined distance 1908 from the top surface of the valve bridge 204 when at least two valve bridges are maintained in a closed state. Further, as shown, the first fixed position of the first member 1802 aligns with a first engine valve of at least two engine valves, the first engine valve being furthest from a rocker shaft 1808 of the internal combustion engine 202. As shown, the first member 1802 may be configured to align with a first engine valve for two or more valve bridges 204, 212, as described. Furthermore, the first member 1802, in this regard, may also extend across the valve bridges of multiple cylinders of an internal combustion engine, or multiple such first members 1802 may be provided if the configuration of the cylinders precludes the use of a single first member 1802.

[0033] In this embodiment, the predetermined distance 1908 between the first member 1802 and the top surface 1904 of the valve bridge 204 is preferably sufficient to prevent contact between the first surface 1906 of the first member 1802 and the top surface 1904 of the valve bridge 204 when the valve bridge 204 is in a controlled state for at least two engine valves, and sufficient to allow contact between the first surface 1906 and the top surface 1904 when the valve bridge 204 is in an uncontrolled state for at least two engine valves to resist uncontrolled movement of the valve bridge 204. As used herein, uncontrolled movement of the valve bridge 204 is resisted to the extent that any of the disclosed valve bridge guides oppose movement of the valve bridge outside of its normal range of movement when operating in a controlled state. 2-12 , while resisting movement that may result in tilting or rotation of the valve bridge 204 relative to the engine valve, the first member 1802 resists excessive vertical displacement of the valve bridge 204 relative to the engine valve, particularly preventing the valve bridge 204 from completely disengaging from the engine valve. By defining the predetermined distance 1908 relative to the closed position of the engine valve, contact between the valve bridge 204 and the first member 1802 is avoided during controlled movement of the valve bridge 204. However, by further defining the predetermined distance 1908 to be sufficiently small, desired resistance to uncontrolled movement of the valve bridge 204 can nevertheless be provided. In one embodiment, the predetermined distance 1908 can be based on the depth 2002 of the receptacle 2004 provided by the valve bridges 204, 212 for engaging the valve tip 2006 of the engine valve ( FIG. 20 ). In particular, the predetermined distance 1908 may be selected to be less than the depth 2002 of the receptacle 2004 .In this manner, if the valve bridges 204, 212 are operated in an uncontrolled manner, they may contact the first member 1802 and otherwise disengage the valve bridges 204, 212 from the valve tip 2006 before they are able to travel a distance greater than the depth 2002 of the receptacle 2004. Furthermore, some forms of engine brakes are known to actuate only a single on-board engine valve (i.e., closest to the rocker shaft), thereby causing that portion of the valve bridge to engage with the external engine valve (i.e., furthest from the rocker shaft) and lift slightly upward, e.g., approximately 1-2 mm. Therefore, the predetermined distance 1908 should be selected to accommodate this possibility to avoid undesired contact with the valve bridge 204. Furthermore, normal wear of the engine valve seat can cause the engine valve tip to lift over time, and the predetermined distance 1908 should also take this possibility into account.

[0034] In this second embodiment, the valve bridge guide may further include a second member 1804 maintained in a second fixed position relative to the valve bridge 204 and having a second surface 1910 facing the top surface 1904 of the valve bridge 204. Like the first member 1802, the second surface 1910 is maintained a predetermined distance 1908 from the top surface 1904 for the same reasons described above. In one embodiment, the second fixed position of the second member 1804 is aligned with a second engine valve of the at least two engine valves, the second engine valve being closest to the rocker shaft 1808. Additionally, as best shown in FIGS. 18 and 19 , the second member 1804 may be formed as a unitary structure with the rocker pedestal 1810. In this manner, the first and second members 1802, 1808 can be aligned with different engine valves separately and at the same predetermined distance 1908 from the upper surface 1904, thereby functioning as valve bridge guides that provide uniform resistance to uncontrolled movement.

[0035] As is known in the art, some valve actuation systems include an auxiliary motion source and valve train that provides auxiliary motion to a single engine valve despite the presence of a valve bridge 212. This is accomplished by the use of a bridge pin 2102, as is known in the art, which allows auxiliary valve actuation motion to be applied to the single engine valve and primary valve actuation motion to be applied to the single engine valve via the valve bridge 212. In this case, the presence of the bridge pin 712 passing through the valve bridge 212 effectively functions as a second member defining a valve bridge guide. That is, when the valve bridge 212 moves uncontrolled, the presence of the bridge pin 712 (operably connected to both the auxiliary rocker arm 2104 and the single engine valve) acts to constrain the valve bridge 212 to only sliding motion relative to the bridge pin 712. In this case, the presence of the auxiliary rocker arm 2104 (or other auxiliary valve train component) acts to prevent movement of the valve bridge 212 off of the bridge pin 2102. Again, where a first member 1802 is provided (as shown), the cooperative action of the first and second members resists uncontrolled movement of the valve bridge 212, particularly upward movement.

[0036] Figure 22 illustrates a first variation of the second embodiment in which the valve bridge guide comprises a first member 2202 formed as a three-sided "strap." Similar to the embodiment of Figures 18-21, the variation illustrated in Figure 22 operates to resist uncontrolled movement by positioning the first member 2202 in contact with the top surface 1904 of the valve bridge. In this embodiment, the first member 2202 may comprise sheet metal or similar material having two substantially vertical elongated sides 2204 (one shown in Figure 22) that extend from above the valve bridge 214 to the base of each of the engine valve springs 208, 210 that are attached to the cylinder head 230. A third substantially horizontal side surface 2206 of the first member 2202 connects with the first and second elongated side surfaces 2204 at the highest normal rest point of the valve bridge 214 (i.e., when the engine valves are fully closed) and above the top surface 1904 of the valve bridge 214. Similar to the embodiment of FIGS. 18-21 , the third side surface 2206 is preferably maintained in a fixed position a predetermined distance 1908 (not shown in FIG. 22 ) from the top surface 1904. As further shown, the third side surface 2206 includes an opening 2210 that allows a portion of the valve bridge 214 (e.g., with reference to FIG. 1 , the outer plunger 720 / cap 730) to contact the rocker arm 2212, as shown. Thus, in this variation, displacement of the valve bridge 204 is constrained by the third side surface 2206 of the first member 2202 and the opening 2206 formed therein.

[0037] Figure 23 is a cross-sectional view of a valve bridge illustrating the shortcomings of prior art systems. In particular, Figure 23 illustrates a valve bridge having a valve bridge body 2302 that spans two engine valve stems 2304, 2306. As shown, a first engine valve 2306 is actuated by an auxiliary rocker arm 2312 via a bridge pin 2308 that receives the stem of the first engine valve 2306. The bridge pin 2308 is then received in a through bore 2310 formed in the valve bridge body 2302 and aligned with the first engine valve 2306, thereby allowing the bridge pin 2308 to contact the auxiliary rocker arm 2312. Additionally, the valve bridge body 2302 includes a receptacle 2314 configured to align with and receive the stem of the second engine valve 2304. 23, the valve bridge 2302 is in an uncontrolled state, as depicted by the receptacle 2314 losing contact with the second engine valve 2304. This results from the fact that there is no surface provided to restrain the upward movement of the valve bridge 2302 during the uncontrolled state.

[0038] Figure 24 illustrates a valve bridge according to the third main embodiment, in which a valve bridge substantially similar to that depicted in Figure 23 is shown. In this case, however, the valve bridge also includes a bridge pin boss 2402 having a through bore 2404 formed therein and having a greater longitudinal length (or height) compared to the embodiment illustrated in Figure 23. As a result, the upper surface 2406 of the bridge pin boss 2402 is closer to the lower surface 2408 of the auxiliary rocker arm 2312 (e.g., in the depicted embodiment, the lower surface of the actuator). Thus, when the valve bridge is in an uncontrolled state resulting in upward movement of the valve bridge body 2302, the upper surface 2406 of the bridge pin boss 2402 contacts the lower surface 2408 of the auxiliary rocker arm 2312 before the valve bridge body 2302 has the potential to fully disengage from the valve stem. This is illustrated in FIG. 24, where contact between the upper surface 2406 and the lower surface 2408 prevents complete disengagement of the receptacle 2410 from the stem of the second engine valve 2304 .

[0039] It will also be appreciated that the like upper surface of that portion of the valve bridge body 2302 aligned with the primary rocker arm 2412 may also be configured in a similar manner as the upper surface 2406 of the bridge pin boss 2402. In this case, the height of the valve bridge body 2302 aligned with the primary rocker arm 2412 may likewise be increased so as to increase the likelihood that the upper surface 2411 of the valve bridge body 2302 will contact the primary rocker arm 2412 (e.g., in the depicted embodiment, the lower surface of the pivot foot) during uncontrolled movement of the valve bridge body 2302. However, in this case, the height of the upper surface 2411 must be selected so as not to interfere with the ability of the folding mechanism 2412 to fully absorb any valve actuation motion provided by the primary rocker arm 2412. In other words, the upper surface 2411 should not be increased to the point where it contacts the primary rocker arm 2412 during controlled state (or controlled movement) of the valve bridge body 2302 and when the folding mechanism 2414 is absorbing a primary valve event.

[0040] Referring now to FIG. 25, valve bridges according to the fourth through sixth main embodiments are illustrated. In particular, FIG. 25 again illustrates a valve bridge of similar configuration to the valve bridge illustrated in FIG. 23. The fourth main embodiment relates to the clearance characteristics between the inner diameter of the through bore 2502 and the outer diameter of the bridge pin 2504. In particular, by tightly controlling and minimizing the clearance between the through bore and the bridge pin, the occurrence of uncontrolled movement would result in a "pinch" (or jamming) of the valve bridge body 2302 and the bridge pin 2504. This is illustrated in FIG. 25 by the contact point 2505 between the through bore 2502 and the bridge pin 2504. This pinch, in turn, damps any further movement of the valve bridge body 2302, thereby tending to keep the valve bridge body 2302 aligned with the engine valve.

[0041] 25 further illustrates the fifth primary embodiment to the extent that it depicts an increased radius spring retainer 2506 (relative to the radius of a typical spring retainer 2510, i.e., comparable to the radius of a valve spring (not shown)). In this embodiment, the increased radius spring retainer 2506 allows that portion 2508 of the valve bridge body 2302 that extends between the engine valve stems to come into quicker contact 2511 with the increased radius spring retainer 2506 during uncontrolled movement (particularly rotation of the valve bridge body 2302), thereby resisting further rotation of the valve bridge body 2302.

[0042] FIG. 25 further illustrates the sixth primary embodiment in that it shows an extended valve stem feature. In the illustrated embodiment, the extended valve stem feature takes the form of a bridge pin 2512 residing in the second through bore 2518. As shown, the bridge pin 2512 is free to move up and down on the engine valve stem 2514. In this case, when the valve bridge body 2302 is in an uncontrolled state, the bridge pin 2512 is free to move upward with the valve bridge body 2302. Regardless of uncontrolled movement of the bridge pin 2512 and the valve bridge body 2302, the bridge pin 2512 maintains alignment of the valve bridge body 2302 with the engine valve stems 2514, 2516 as long as the bridge pin 2512 remains seated on the engine valve stem 2514. As shown, the same principles of controlled movement on the engine valve stem 2516 can be equally applied to a bridge pin 2504 aligned with an auxiliary rocker arm. In this embodiment, it may be desirable for either or both of the engine valve stems 2514, 2516 to have an extended length beyond the spring retainers 2506, 2512, for example, up to 10 mm, compared to a more typical length of 2-3 mm.

[0043] 26-28 illustrate a valve bridge according to the seventh principal embodiment. In accordance with a typical valve bridge, the illustrated valve bridge includes a valve bridge body 2602 spanning at least two engine valves 2604, 2606. In this embodiment, slots 2608 are formed in those portions of the valve bridge body 2602 configured to contact the stems of the engine valves 2604, 2606. In particular, as best shown in FIG. 28, the slots 2608 may comprise laterally extending slots that intersect transversely with the receptacles 2802 and the longitudinal axes 2806 of the engine valve stems 2604 (only one shown in FIG. 28). When the engine valve stem 2604 is aligned with and inserted into a corresponding receptacle 2802, an annular channel 2804 formed in the engine valve stem 2604 aligns with the slots 2608. The C-clip 2702 is inserted into the slot 2608 and engages with the annular channel 2804 such that the C-clip 2702 is retained on the engine valve stem 2604. Once retained on the engine valve stem 2604, further engagement of the C-clip 2702 with the slot 2608 enables the C-clip 2702 to resist disengagement of the engine valve stem 2604 from the receptacle 2802, for example, during uncontrolled movement of the valve bridge body 2602. While the slot 2608 is illustrated in FIGS. 26-28 as extending laterally away from the valve bridge body 2602, this is not a requirement. For example, the slot 2608 could instead extend perpendicular to the plane of FIG. 28, i.e., perpendicular to the longitudinal axis of the valve bridge body and perpendicular to the longitudinal axis 2806 of the engine valve stems 2604, 2606.

[0044] 29 is a side view of a valve bridge according to the eighth principal embodiment. In this embodiment, a valve bridge body 2902 includes a protrusion 2904 extending downward from a lower surface 2908 of the valve body 2902 and positioned between at least two engine valve stems (not shown). As further shown, the protrusion 2904 further includes at least one hook feature 2906 (only one shown) extending away from the protrusion 2904 toward and below the at least one spring retainer 2910 such that the hook or latch feature 2906 extends beyond the outer periphery of the at least one spring retainer 2910. When the valve bridge body 2902 is in an uncontrolled state, the hook feature 2906 contacts a lower surface 2912 of the valve spring retainer 2910, preventing the valve bridge body 2902 from separating from the engine valve stems until the point at which the valve bridge body is fully disengaged from the engine valve stems. 25, the increased radius spring retainer 2910 can provide a protruding rim of material that extends beyond the outer periphery of the corresponding valve spring 2914. In this manner, the hook feature 2906 can better engage the spring retainer 2910, thereby ensuring better resistance to valve bridge disengagement.

[0045] As further shown in FIG. 29 , the perimeter 2914 of the protrusion 2904 is configured to allow the valve bridge body 2902 to move downward over one of the engine valves (the right-most, as depicted in FIG. 29 , as in the case of an auxiliary valve actuation movement) and tilt without contacting the springs 2914, 2918. Based on the illustrated configuration, installation of the valve bridge is facilitated by installing the left side first, then rotating the valve bridge downward onto the right-most engine valve stem (and corresponding bridge pin 2920). The bridge pin 2920 is held down by a separate auxiliary rocker or its integral actuator piston (not shown), but the bridge cannot be removed due to the latching effect of the hook feature 2906.

[0046] Figures 30 and 31 illustrate a valve bridge and bridge pin according to the ninth principal embodiment. In this embodiment, a valve bridge body 3002 includes open, laterally extending slots 3004, 3006 configured to receive a corresponding bridge pin 3008, 3010 between respective arms 3022, 3024 defined by the slots 3004, 3006 extending into the valve body 3002. As best shown in Figure 31, each bridge pin 3008, 3010 has a receptacle 3102 formed therein and configured to receive a corresponding engine valve stem 3012. As shown, each of the bridge pins 3008, 3010 has a spool-like shape including a barrel body 3016 and an increased diameter end cap 3018, 3020 (relative to the barrel body 3016). The slots 3004, 3006 are configured to maintain relatively close clearance between the arms 3022, 3024 and the barrel body 3016 of their respective bridge pins 3008, 3010, while the slots 3004, 3006 are configured to allow the arms 3022, 3024 to contact the end caps 3018, 3020. In this manner, vertical movement of the bridge pins 3008, 3010 is constrained by the spacing 3104 between the upper (and / or lower) surfaces of the arms 3022, 3024 and the complementary surfaces defined by the end caps 3018, 3020. In this manner, the constraint placed on the valve bridge body 3002 by the bridge pins 3008, 3010 prevents disengagement from the engine valve stems 3012, 3014 if the valve bridge body 3002 undergoes uncontrolled movement. It should be noted that similar to the third main embodiment illustrated in FIG. 24, the top surface 3026 of the valve bridge body 3002 may be configured such that the spacing between the top surface 3026 and the end cap 3010 is configured to even further restrict upward movement of the valve bridge body 3002.

[0047] FIG. 32 illustrates a valve actuation system according to prior art techniques. In particular, valve actuation systems are known in which a folding mechanism similar to that shown in FIG. 1 is deployed on a rocker arm 3202 or push rod 3204, rather than on a valve bridge 3206 as depicted in many of the previously described embodiments. As is known in the art, the rocker arm 3202 fully engages the rocker shaft 3208, but such valve actuation systems present an opportunity for the valve bridge 3206 to enter an uncontrolled state if excessive lash builds up in the valve train. For example, a sudden collapse in the push rod 3204 could allow the rocker to rotate rearward (i.e., toward the push rod 3204), which is equivalent to a sudden elimination of valve lift. If the valve lift lost in this manner is relatively high (e.g., 14 mm in some systems), the sudden rearward rotation of the rocker arm 3202 could cause the rocker arm 3202 to hit the valve cover 3210 or other object. Because the rocker arm 3202 is normally relied upon to maintain engagement of the valve bridge 3206 with the engine valve stem, the sudden backward rotation of the rocker arm 3202 combined with the rapid acceleration of the valve bridge 3206 under the influence of the valve spring can cause the valve bridge to move in an uncontrolled manner, potentially resulting in disengagement.

[0048] To prevent the valve bridge 3206 from disengaging in such a situation, a stop can be provided to prevent over-rotation of the rocker arm 3202 that would normally allow the valve bridge 3206 to disengage. An example of this is illustrated in FIG. 33 , which shows a rigid or fixed block 3302 deployed to prevent backward rotation of the rocker arm 3202. In the illustrated embodiment, the fixed block 3302 is rigidly attached to the rocker shaft 3208 and, in this example, includes both a vertical surface 3304 and a horizontal surface 3306 configured to engage surfaces of the rocker arm 3202 to prevent over-rotation thereof. The fixed block 3302 is configured such that the vertical surface 3304 and the horizontal surface 3306 do not interfere with the normal reciprocating (i.e., controlled) motion of the rocker arm 3202. However, the fixed block 3302 is also configured such that the vertical surface 3304 and the horizontal surface 3306 are positioned to prevent over-rotation of the rocker arm 3202.

[0049] For example, the illustrated rocker arm 3202 may include a rear facing surface 3308, in this case defined by a control valve boss formed on the rocker arm 3202. In the event of a sudden rearward rotation, the rear facing surface 3308 contacts the vertical surface 3304, preventing over-rotation of the rocker arm 3202. Similarly, the rocker arm further includes an upward facing surface 3310. In the event of a sudden rearward rotation, the rear facing surface 3310 contacts the horizontal surface 3306, preventing over-rotation of the rocker arm 3202. While the illustrated embodiment includes both the vertical surface 3304 and the horizontal surface 3306, this is not a requirement, as it is anticipated that either such surface may be sufficient to prevent over-rotation depending on the configuration of the rocker arm 3202.

[0050] 34 and 35 illustrate a valve bridge and valve bridge guide according to an eleventh embodiment. In this embodiment, a valve bridge guide 3404 is provided that is attached to (or integrally formed with) a valve bridge body 3402. As shown, the valve bridge guide 3404 is deployed on a side of the valve bridge body 3402 that is not intended to engage with an engine valve (not shown), which may also be actuated by an auxiliary motion source. In the illustrated embodiment, the valve bridge guide 3404 is shaped as a half-cylinder wall configured to be attached to the lower surface 3502 of the valve bridge body 3402, with the half-cylinder wall extending downwardly from the lower surface 3502. However, it will be understood that the valve bridge guide 3404 may be attached to some other surface (e.g., the upper surface) of the valve bridge body 3402, so long as the half-cylinder wall extends downwardly below the lower surface 3502 as shown.

[0051] Figure 36 illustrates the valve bridge and valve bridge guide of Figures 34 and 35 deployed in a valve actuation system. As shown, the valve bridge body 3402 spans two engine valve stems, and the valve bridge guide 3404 encompasses the outer lateral portions of the valve spring retainer 3602. The radii of the half-cylinder walls (preferably centered on or near the longitudinal axis of the corresponding engine valve stem) are configured to prevent contact between the half-cylinder walls and the valve spring retainer 3602 or the corresponding valve spring 3604 during normal (i.e., controlled) operation of the valve bridge. Meanwhile, the radii of the half-cylinder walls are further configured to contact the valve spring retainer 3602 but avoid contact with the valve spring 3604 during an uncontrolled state of the valve bridge body 3402. Similar to the embodiment described above in connection with Figures 25 and 29, an increased radius spring retainer can be used to better ensure contact between the valve spring retainer 3602 and the spring retainer (preferably not the valve spring 3604).

[0052] As noted above, the present disclosure describes various embodiments and variations of valve bridge guides that may be used to resist, i.e., prevent, minimize, or accommodate, uncontrolled movement of a valve bridge. While various features have been described in conjunction with particular embodiments, those skilled in the art will understand that various of such features may be incorporated into the other embodiments described herein.

Claims

1. 1. A valve actuation assembly for use in actuating at least two engine valves in an internal combustion engine, comprising: a rocker arm disposed within the valve train and operatively connected to the at least two engine valves, the rocker arm including an upwardly facing surface, a rearwardly facing surface, or both; a stop comprising a block fixed relative to the rocker arm, the block comprising a horizontal surface or a vertical surface or both, the block further configured such that the horizontal surface or the vertical surface or both are configured to avoid interference with the rocker arm during a controlled state of the rocker arm, but allow contact between the upwardly facing surface and the horizontal surface or contact between the rearwardly facing surface and the vertical surface, or both, to resist rearward rotation of the rocker arm when the rocker arm is in an uncontrolled state due to the formation of a sudden lash in the valve train.

2. 2. The valve actuation assembly of claim 1, further comprising a rocker arm shaft, said rocker arm being mounted on said rocker arm shaft for reciprocating movement, said block being fixed to said rocker arm shaft.

Images