WO2024110066A1

WO2024110066A1 - Telescopic bridge assembly for rocker arm assembly

Info

Publication number: WO2024110066A1
Application number: PCT/EP2023/025495
Authority: WO
Inventors: Dhairyasheel THORAT; Pritam EDKE; Srijan SINGHAL
Original assignee: Eaton Intelligent Power Ltd
Current assignee: Eaton Intelligent Power Ltd
Priority date: 2022-11-25
Filing date: 2023-11-24
Publication date: 2024-05-30
Anticipated expiration: 2025-05-25
Also published as: DE112023004924T5; CN120202344A

Abstract

A valve bridge assembly for actuating at least one valve. The valve bridge assembly including a bridge having one surface configured to engage a rocker arm assembly and an opposite facing surface configured to engage a distal end of at least one valve. At least one valve stem extension extends between the bridge and the at least one valve wherein the valve stem extension is movable relative to one of the bridge or the at least one valve. A guide is attached to one of the bridge or the at least one valve for guiding the at least one valve stem extension relative to one of the bridge or the at least one valve. At least one spring is provided for biasing the bridge and the at least one valve away from each other.

Description

TELESCOPIC BRIDGE ASSEMBLY FOR ROCKER ARM ASSEMBLY

Priority

[0001] This application claims the benefit of priority of provisional Indian patent application Ser. No. 202211068005, filed November 25, 2022, the contents of which are incorporated herein by reference in their entirety.

Field

[0002] The subject application relates to, in general, a rocker arm assembly for use in a combustion engine wherein the rocker arm assembly includes a lost motion mechanism for cylinder deactivation and a bridge for actuating one or more valves. More particularly, this application relates to a rocker arm assembly having a telescopic valve bridge assembly for maintaining contact with the one or more valves during operation.

Background

[0003] An internal combustion engine may utilize a rocker arm assembly with a front rocker arm and a rear rocker arm that are selectively coupled to each other via a latching mechanism. When latched together, motion on a cam end of the rear rocker arm is transferred to a valve end of the front rocker arm to actuate one or more valves. When unlatched, motion on the cam end of the rear rocker arm is not transferred to the valve end of the front rocker arm. Because a spring links the rear rocker arm and the front rocker arm together, when the rocker arm assembly is in a “critical shift,” the momentum of the front rocker arm may cause the front rocker arm to over rotate, thereby resulting in a valve bridge on the valve end of the rocker arm assembly becoming dislodged from the one or more valves.

[0004] The present application discloses a telescopic bridge assembly for maintaining a valve bridge in alignment with distal ends of a valve during excessive rotation of a rear rocker arm relative to a front rocker arm. Summary of the Invention

[0005] There is provided a valve bridge assembly for actuating at least one valve. The valve bridge assembly including a bridge having one surface configured to engage a rocker arm assembly and an opposite facing surface configured to engage a distal end of at least one valve. At least one valve stem extension extends between the bridge and the at least one valve wherein the valve stem extension is movable relative to one of the bridge or the at least one valve. A guide is attached to one of the bridge or the at least one valve for guiding the at least one valve stem extension relative to one of the bridge or the at least one valve. At least one spring is provided for biasing the bridge and the at least one valve away from each other.

[0006] In the foregoing valve bridge assembly, the at least one valve stem extension includes a cavity dimensioned to engage the distal end of the at least one valve.

[0007] In the foregoing valve bridge assembly, the at least one valve stem extension includes cavity dimensioned to receive the at least one spring.

[0008] In the foregoing valve bridge assembly, the at least one valve stem extension includes a stem dimensioned to slide relative to the bridge.

[0009] In the foregoing valve bridge assembly, the guide is fixed to the bridge and the stem slides relative to the guide.

[00010] In the foregoing valve bridge assembly, the guide is integrally formed with the bridge.

[00011] In the foregoing valve bridge assembly, the guide is formed as a plate configured to be fixed to the at least one valve.

[00012] In the foregoing valve bridge assembly, the at least one spring is compressed between the bridge and the guide.

[00013] In the foregoing valve bridge assembly, the at least one valve stem extension is secured to the bridge.

[00014] There is further provided a valve bridge assembly for actuating at least one valve. The valve bridge assembly including a bridge having one surface configured to engage a rocker arm assembly and an opposite facing surface configured to engage a distal end of at least one valve. At least one valve stem extension extends between the bridge and the at least one valve wherein the valve stem extension is movable relative to the bridge. A guide is provided for guiding the at least one valve stem extension relative to the bridge. At least one spring is provided for biasing the bridge and the at least one valve away from each other. [00015] In the foregoing valve bridge assembly, the at least one valve stem extension includes a cavity dimensioned to engage a distal end of the least one valve.

[00016] In the foregoing valve bridge assembly, the at least one valve stem extension includes a cavity dimensioned to receive the at least one spring.

[00017] In the foregoing valve bridge assembly, the at least one valve stem extension includes a stem dimensioned to slide relative to the bridge.

[00018] In the foregoing valve bridge assembly, the guide is fixed to the bridge and the stem slides relative to the guide.

[00019] In the foregoing valve bridge assembly, the guide is integrally formed with the bridge.

[00020] There is further provided a valve bridge assembly for actuating at least one valve. The valve bridge assembly includes a bridge having one surface configured to engage a rocker arm assembly and an opposite facing surface configured to engage a distal end of at least one valve. At least one valve stem extension extends between the bridge and the at least one valve wherein the valve stem extension is connected to the bridge and movable relative to the at least one valve. A guide is attached to the at least valve for guiding the at least one valve stem extension. At least one spring is provided for biasing the bridge and the at least one valve away from each other.

[00021] In the foregoing valve bridge assembly, the bridge includes a cavity dimensioned to engage a distal end of the at least one valve.

[00022] In the foregoing valve bridge assembly, the at least one valve stem extension includes a stem dimensioned to slide relative to the guide.

Brief Description of the Drawings

[00023] FIG. 1 is a perspective view of a rocker arm assembly having a lost motion mechanism;

[00024] FIG. 2 is a side view of a rocker arm assembly illustrating a valve bridge for engaging two valves with the valve bridge dislodged from distal ends of the valves;

[00025] FIG. 3 is a sectioned view of a telescopic valve bridge assembly according to a first embodiment of the present invention;

[00026] FIG. 4 is an enlarged sectioned view of the telescopic valve bridge assembly of FIG. 3;

[00027] FIG. 5 is a sectioned view of a valve stem extension of the telescopic valve bridge assembly of FIG. 3; [00028] FIG. 6 is a sectioned view of an extender guide of the telescopic valve bridge assembly of FIG. 3;

[00029] FIG. 7 is a sectioned view of a compression spring of the telescopic valve bridge assembly of FIG. 3;

[00030] FIG. 8 is a side view of the telescopic valve bridge showing a front rocker arm in an over rotated position with the telescopic valve bridge assembly in contact with distal ends of valve stems;

[00031] FIG. 9 is an enlarged view of FIG. 8;

[00032] FIG. 10 is a perspective view of a telescopic valve bridge assembly according to a second embodiment;

[00033] FIG. 11 is a sectioned view of the telescopic valve bridge assembly of FIG. 10;

[00034] FIG. 12 is a side view of the telescopic valve bridge of FIG. 10 showing a front rocker arm in an over rotated position with the telescopic valve bridge assembly in contact with distal ends of valve stems;

[00035] FIG. 13 is an enlarged view of FIG. 12; and

[00036] FIG. 14 is a sectioned view of a telescopic valve bridge assembly according to a third embodiment.

Detailed Description

[00037] The following presents a description of the disclosure; however, aspects may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Furthermore, the following examples may be provided alone or in combination with one or any combination of the examples discussed herein. Directional references such as “left” and “right” are for ease of reference to the figures.

[00038] Referring to FIG. 1, a rocker arm assembly 10 is shown. The rocker arm assembly 10, in general, includes a front rocker arm 22, a rear rocker arm 24, a latch mechanism 26 (partially seen in FIG. 1) and a spring 28 that links the front rocker arm 22 and the rear rocker arm 24 together. The rocker arm assembly 10 has a valve end 12 configured to engage a valve bridge 50 (FIG. 2) and a cam end 14 configured to engage a cam 40 (FIG. 2). The front rocker arm 22 and the rear rocker arm 24 each include a bore 22a, 24a (FIG. 2), respectively, for allowing the front rocker arm 22 and the rear rocker arm 24 to receive a main rocker shaft 30. The front rocker arm 22 and the rear rocker arm 24 are configured to pivot on the main rocker shaft 30 via actuation by the cam 40. The cam 40 includes a cam profile that is configured to cause the entire rocker arm assembly 10 to pivot about the main rocker shaft 30 at predetermined intervals as the cam 40 rotates. [00039] When the latch mechanism 26 is in a latched position, a center pin (not shown) of the latch mechanism 26 is partially in both the front rocker arm 22 and the rear rocker arm 24 to couple them together so that they pivot as a unitary body. When the latch mechanism 26 is in an unlatched position (i.e., the center pin (not shown) is in only one of the front rocker arm 22 or the rear rocker arm 24), the rear rocker arm 24 may pivot independent of the front rocker arm 22. In this position, when the cam 40 applies motion/displacement to the rear rocker arm 24, no motion is transferred to the front rocker arm 22 or the valve end 12 of the rocker arm assembly 10.

[00040] Referring to FIG. 2, when the rocker arm assembly 10 is in a critical position (referred to as “critical shift”) wherein the rocker arm assembly 10 actuates the valves 60 but the front rocker arm 22 becomes unlatched from the rear rocker arm 24. During this critical shift, the front rocker arm 22 is free to over rotate by the angle A. This over rotation, in turn, causes the valve bridge 50 to be dislodged from the distal ends 62 of the valves 60 by a distance Xf₀ (referred to as maximum bridge dislodgement). This dislodgement is commonly referred to as “fly-off’ and may cause a failure of the rocker arm assembly 10 if the valve bridge 50 is not able to re-align with and engage the distal ends 62 of the valves 60.

[00041] Referring to FIGS. 3-7, a telescopic valve bridge assembly 100, according to a first embodiment of the present invention, is shown. The telescopic valve bridge assembly 100 includes, in general, a bridge 110, an extender guide 120, a valve stem extension 130 and a spring 150.

[00042] Referring to FIG 4, the bridge 110 of the telescopic valve bridge assembly 100 includes a counterbored hole 112 that extends into a lower surface 114 of the bridge 110. A hole 118 extends through the bridge 110 from a bottom of the counterbored hole 112 and exits through an upper surface 116 of the bridge 110. A portion of the lower surface 114 around the counterbored hole 112 is recessed to define a peripheral seat 112a.

[00043] The extender guide 120 is dimensioned to be received into the hole 118 and to extend into the counterbored hole 112. Referring to FIG. 6, the extender guide 120 includes a tubular-shaped body 122 having an outwardly extending peripheral flange 124 at one end thereof.

[00044] Referring back to FIG. 4, the valve stem extension 130 is dimensioned to slide in the extender guide 120. As shown in FIG. 5, the valve stem extension 130 includes a tubular-shaped body 132 having an outwardly extending peripheral flange 134 at one end thereof. A partition 136 transverses an inner cavity of the body 132 to divide the inner cavity into a first cavity 142a and a second cavity 142b. A stem 144 extends from one side of the partition 136, through the first cavity 142a and protrudes from an end of the body 132. The second cavity 142b is dimensioned to receive the distal end 62 of a respective valve 60, as described in detail below.

[00045] The compression spring 150 is dimensioned to be received in the first cavity 142a. Referring to FIG. 7, the compression spring 150 is a wire that is wrapped into a coil. The compression spring 150 is configured to apply an axially directed force when compressed.

[00046] Referring to FIG. 4, the telescopic valve bridge assembly 100 is assembled by placing the extender guide 120 into the hole 118 in the bridge 110 such that the flange 124 is positioned adjacent the upper surface 116 of the bridge 110 and the body 122 of the extender guide 120 extends into the counterbored hole 112. It is contemplated that the extender guide 120 may be press-fit into the hole 118. The spring 150 is dimensioned to have an inner diameter that is larger than an outer diameter of the extender guide 120 but smaller than the inner diameter of the first cavity 142a of the valve stem extension 130. The spring 150 is placed in the first cavity 142a. The valve stem extension 130 is then inserted into the extender guide 120. In particular, the stem 144 is inserted into the bridge 110 from the lower surface 114 thereof and into the extender guide 120. As the stem 144 is moved into the extender guide 120, the spring 150 is compressed between the surface of the partition 136 defining the first cavity 142a and the end surface of the counterbored hole 112. The spring 150 is configured to bias the valve stem extension 130 outwardly from the counterbored hole 112.

[00047] Referring to FIG. 3, the second cavity 142b of the valve stem extension 130 is dimensioned to receive the distal end 62 of the valve 60. The second cavity 142b is dimensioned to allow the distal end 62 to slide therein. During normal operation, i.e., when the latch mechanism 26 is in the latched position or the front rocker arm 24 has not rotated an excessive distance (i.e., in the clockwise direction when viewed in FIG. 3), the telescopic valve bridge assembly 100 is captured between the valve end 12 of the rocker arm assembly 10 and the distal ends 62 of the valves 60. In this position, the valve stem extension 130 is fully seated in the bridge 110 such that the spring 150 is compressed and the telescopic valve bridge assembly 100 acts as a solid, unitary body. Any motion applied to the telescopic valve bridge assembly 100 by the valve end 12 of the rocker arm assembly 10 is transferred through the telescopic valve bridge assembly 100 to the distal ends 62 of the valves 60 to cause the valves 60 to move accordingly.

[00048] Referring to FIGS. 8 and 9 (wherein springs 150 are not shown for clarity), when the rocker arm assembly 10 is in the critical shift, as explained in detail above, the bridge 110 still experiences the valve dislodgement displacement of Xf₀, but the spring 150 in the telescopic valve bridge assembly 100 moves the valve stem extension 130 outwardly from the counterbored hole 112 in the bridge 110. A length DI of the valve stem extension 130 and a length D2 of the extender guide 120 (see, FIG. 4) are selected so that the second cavity 142b maintains engagement with the distal end 62 of the valve 60, and, simultaneously, the stem 144 of the valve stem extension 130 maintains sliding engagement with the extender guide 120. For example, it is contemplated that the valve stem extension 130 and the extender guide 120 may be configured to provide about 22 mm of engagement when the maximum fly-off of the bridge 110 is about 19 mm.

[00049] It is contemplated that the valve stem extension 130 may move out of the counterbored hole 112 in the bridge 110 during the rotation of the front rocker arm 22. The seat 112a of the counterbored hole 112 may be chamfered to aid in the re-engagement of the valve stem extension 130 with the counterbored hole 112 when the bridge 110 moves toward the valves 60. It is also contemplated that the length DI (FIG. 4) of the stem 144 of the valve stem extension 130 may be selected based on a maximum rotation expected for the front rocker arm 22 so that the valve stem extension 130 always remains in contact with the valve 60 and the extender guide 120 during movement of the front rocker arm 22.

[00050] Once the first rocker arm 22 has reached is maximum displacement in the clockwise direction, the front rocker arm 22 begins to move in the counterclockwise direction. Because the telescopic valve bridge assembly 100 maintained engagement with the valve 60 during the critical shift of the front rocker arm 22, the alignment of the telescopic valve bridge assembly 100 with the valves 60 is maintained. The rocker arm assembly 10 may then return to the position shown in FIG. 3.

[00051] It is contemplated that a gap between an outer diameter of the stem 144 of the valve stem extension 130 and the inner diameter of the extender guide 120 may be about 0.015 mm to allow the stem 144 to slide within the extender guide 120. A gap between an outer diameter of the body 132 of the valve stem extension 130 and the inner diameter of the counterbored hole 112 of the bridge 110 may be about 0.05 mm to allow the valve stem extension 130 to slide within the bridge 110. A gap between an outer diameter of the flange 134 of the valve stem extension 130 and the seat 112a around the counterbored hole 112 of the bridge 110 may be about 0.10 mm to allow the valve stem extension 130 to slide within the bridge 110.

[00052] According to a second embodiment, illustrated in FIGS. 10-13 (wherein springs 250 are not shown in FIGS. 12 and 13 for clarity), a telescopic valve bridge assembly 200 includes a bridge 210 that incorporates the features of the extender guide 120 into the bridge 110. Referring to FIG. 11, the bridge 210 includes a hole 212 that extends between a lower surface 214 and an upper surface 216 of the bridge 210. The hole 212 defines an entirety of the sliding bearing surface for a stem 244 of a valve stem extension 230 (described in detail below). A peripheral groove 218 is formed around the hole 212 from the lower surface 214 of the bridge 210. The peripheral groove 218 defines a cavity for receiving a compression spring 250 that biases the valve stem extension 230 away from the lower surface 214 of the bridge 210.

[00053] The valve stem extension 230 includes the stem 244 that engages the hole 212, a flange 234 and a lower cavity 242 that receives the distal end 62 of the valve 60 (similar to the second cavity 142b of the valve stem extension 130). A hole 238 extends through the stem 244 and is dimensioned to receive a retaining wire 260.

[00054] Referring to FIGS. 10 and 11, the telescopic valve bridge assembly 200 is assembled by placing the spring 250 in the peripheral groove 218 and then inserting the stem 244 of the valve stem extension 230 into the hole 212 such that the flange 234 of the valve stem extension 230 is positioned adjacent the lower surface 214 of the bridge 210. The hole 238 is positioned and dimensioned so that when the stem 244 extends from the upper surface 216 of the bridge 210 the retaining wire 260 may be inserted into the hole 238 to prevent the valve stem extension 230 from being forced out of the hole 212 in the bridge 210. The telescopic valve bridge assembly 200 is then positioned into engagement with the valves 60 such that the distal ends 62 of the valves 60 are received into and engaged with the lower cavity 242 of the valve stem extension 230. The retaining wire 260 is then removed to allow the valve stem extension 230 to move, as described below.

[00055] Similar to the telescopic valve bridge assembly 100 of the first embodiment, when the latch mechanism 26 is in the unlatched position (i.e., the front rocker arm 22 is free to rotate relative to the rear rocker arm 24) over rotation (angle A in FIG. 12) of the front rocker arm 22 in the clockwise direction when viewed in FIGS. 12 and 13, causes the bridge 210 to be offset by the distance Xf₀ (FIG. 13)the spring 250 in the telescopic valve bridge assembly 200 to move the valve stem extension 230 outwardly from the hole 212 in the bridge 210. The hole 212 and the valve stem extension 230 are dimensioned such that the lower cavity 242 maintains engagement with the distal end 62 of the valve 60, and, simultaneously, the stem 244 of the valve stem extension 230 maintains sliding engagement with the hole 212 in the bridge 210.

[00056] It is contemplated that a length D3 (FIG. 11) of the stem 244 of the valve stem extension 230 may be selected based on a maximum rotation expected of the front rocker arm 22 so that the valve stem extension 230 always remains in contact with the valve 60 and the hole 212 during movement of the front rocker arm 22.

[00057] Once the first rocker arm 22 has reached is maximum displacement in the clockwise direction, the front rocker arm 22 begins to move in the counterclockwise direction (when viewed in FIG. 12). Because the telescopic valve bridge assembly 200 maintained engagement with the valve 60 during the movement of the front rocker arm 22, the alignment of the telescopic valve bridge assembly 200 with the valves 60 is maintained. [00058] According to a third embodiment, referring to FIG. 14, a telescopic valve bridge assembly 300 includes, in general, a bridge 310, a stem guide plate 320 and a valve stem extensions 330. In the embodiment illustrated, the bridge 310 includes recessed pockets 312 that are dimensioned to receive the distal ends 62 of the valves 60. The valve stem extensions 330 (two of which are illustrated in FIG. 14) are illustrated as elongate rods having one end attached to the bridge 310. The opposite end of the valve stem extensions 330 are dimensioned to slide through holes 322 formed in the stem guide plate 320.

[00059] The stem guide plate 320 includes holes 324 for attaching the stem guide plate 320 to the distal end 62 of the valve 60. A spring 350 is positioned between a lower surface 314 of the bridge 310 and an upper surface 326 of the stem guide plate 320 for biasing the stem guide plate 320 away from the lower surface 314 of the bridge 310.

[00060] In the embodiment illustrated, the stem guide plate 320 is attached to two valves 60, two valve stem extensions 330 extend from the bridge 310 through the stem guide plate 320 and two springs 350 are provided for biasing the stem guide plate 320 away from the bridge 310. The telescopic valve bridge assembly 300 is assembled by placing the stem guide plate 320 on the distal ends 62 of the valves 60. Thereafter, the springs 350 are placed on the valve stem extensions 330 and the valve stem extensions 330 are inserted through the mating holes 322 in the stem guide plate 320.

[00061 ] Similar to the telescopic valve bridge assembly 100 of the first embodiment, when the rocker arm assembly 10 is in the critical position (described in detail above) the over rotation of the front rocker arm 22 in the counterclockwise direction when viewed in FIG. 14, causes the bridge 310 to also move in the counterclockwise direction B away from the valves 60 (which are stationary). As the bridge 310 moves a gap Y between the bridge 310 and the stem guide plate 320 increases because the springs 350 in the telescopic valve bridge assembly 300 bias the stem guide plate 320, i.e., away from the bridge 310. The holes 322 in the stem guide plate 320 and the valve stem extensions 330 are dimensioned such that the valve stem extensions 330 maintain engagement with the holes 322 in the stem guide plate 320 as the bridge 310 rotates in the counterclockwise direction. After the front rocker arm 22 has reached the maximum displacement (referred to as Xf₀ above), the valve stem extensions 330 are guided by the holes 322 to realign the recessed pockets 312 in the bridge 310 with the distal ends 62 of the valves 60. The telescopic valve bridge assembly 300 may then return to the position illustrated in FIG. 14.

[00062] It is contemplated that a length D4 (FIG. 14) of the valve stem extensions 330 may be selected based on a maximum rotation expected of the front rocker arm 22 so that the valve stem extensions 330 always remain in contact with the stem guide plate 320 during movement of the front rocker arm 22.

[00063] The present invention thereby provides telescopic bridge assemblies that maintain contact between a bridge and distal ends of valves during a “fly-off’ condition of the bridge. By maintaining contact between the bridge and the distal ends of the valves, the present invention allows the bridge to re-align with the distal ends of the valves and reduces the likelihood that the bridge will not properly seat on the valves. In the embodiments illustrated, the valve stem extensions are fixed to either the bridge or the valves and are configured to move respect to the other. In other words, when the valve stem extension is fixed to the valve, the valve stem extension is guided by a guide fixed on the bridge. Similarly, when the valve stem extensions are fixed to the bridge, the valve stem extensions are guided by a guide fixed to the valve.

[00064] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the claimed invention.

Claims

Claims What we claim is:

1. A valve bridge assembly for actuating at least one valve, the valve bridge assembly comprising: a bridge having one surface configured to engage a rocker arm assembly and an opposite facing surface configured to engage a distal end of at least one valve; at least one valve stem extension extending between the bridge and the at least one valve wherein the valve stem extension is movable relative to one of the bridge or the at least one valve; a guide attached to one of the bridge or the at least one valve for guiding the at least one valve stem extension relative to one of the bridge or the at least one valve; and at least one spring for biasing the bridge and the at least one valve away from each other.

2. The valve bridge assembly of claim 1 , wherein the at least one valve stem extension includes a cavity dimensioned to engage a distal end of the at least one valve.

3. The valve bridge assembly of claim 2, wherein the at least one valve stem extension includes cavity dimensioned to receive the at least one spring.

4. The valve bridge assembly of claim 2, wherein the at least one valve stem extension includes a stem dimensioned to slide relative to the bridge.

5. The valve bridge assembly of claim 4, wherein the guide is fixed to the bridge and the stem slides relative to the guide.

6. The valve bridge assembly of claim 1, wherein the guide is integrally formed with the bridge.

7. The valve bridge assembly of claim 1, wherein the guide is formed as a plate configured to be fixed to the at least one valve.

8. The valve bridge assembly of claim 7, wherein the at least one spring is compressed between the bridge and the guide.

9. The valve bridge assembly of claim 7, wherein the at least one valve stem extension is secured to the bridge.

10. A valve bridge assembly for actuating at least one valve, the valve bridge assembly comprising: a bridge having one surface configured to engage a rocker arm assembly and an opposite facing surface configured to engage a distal end of at least one valve; at least one valve stem extension extending between the bridge and the at least one valve wherein the valve stem extension is movable relative to the bridge; a guide for guiding the at least one valve stem extension relative to the bridge; and at least one spring for biasing the bridge and the at least one valve away from each other.

11. The valve bridge assembly of claim 10, wherein the at least one valve stem extension includes a cavity dimensioned to engage a distal end of the least one valve.

12. The valve bridge assembly of claim 10, wherein the at least one valve stem extension includes a cavity dimensioned to receive the at least one spring.

13. The valve bridge assembly of claim 10, wherein the at least one valve stem extension includes a stem dimensioned to slide relative to the bridge. The valve bridge assembly of claim 10, wherein the guide is fixed to the bridge and the at least one valve stem slides relative to the guide. The valve bridge assembly of claim 10, wherein the guide is integrally formed with the bridge. A valve bridge assembly for actuating at least one valve, the valve bridge assembly comprising: a bridge having one surface configured to engage a rocker arm assembly and an opposite facing surface configured to engage a distal end of at least one valve; at least one valve stem extension extending between the bridge and the at least one valve wherein the valve stem extension is connected to the bridge and movable relative to the at least one valve; a guide attached to the at least valve for guiding the at least one valve stem extension; and at least one spring for biasing the bridge and the at least one valve away from each other. The valve bridge assembly of claim 16, wherein the bridge includes a cavity dimensioned to engage a distal end of the at least one valve. The valve bridge assembly of claim 16, wherein the at least one valve stem extension includes a stem dimensioned to slide relative to the guide.