CN113167137A

CN113167137A - Rocker arm assembly for engine braking

Info

Publication number: CN113167137A
Application number: CN201980078116.8A
Authority: CN
Inventors: 马克·范文杰登; 小道格拉斯·J·尼尔森; 小詹姆斯·E·麦卡锡
Original assignee: Eaton Intelligent Power Ltd
Current assignee: Eaton Intelligent Power Ltd
Priority date: 2018-11-19
Filing date: 2019-11-19
Publication date: 2021-07-23
Anticipated expiration: 2039-11-19
Also published as: CN117386475A; CN113167137B; WO2020104057A1; EP3884141A1

Abstract

An exhaust valve rocker arm assembly selectively opens a first exhaust valve and a second exhaust valve. The assembly includes an exhaust rocker arm and a valve bridge operatively associated with the rocker arm and including a body and a lever rotatably coupled to the body. The body is configured to engage a first exhaust valve and the lever is configured to engage a second exhaust valve.

Description

Rocker arm assembly for engine braking

Cross Reference to Related Applications

This application claims priority to U.S. application No. 16/195,120 filed on day 11/19 in 2018, U.S. application No. 16/195,120 is a continuation-in-part of U.S. application No. 15/654,877 filed on day 7/20 in 2017, U.S. application No. 15/654,877 is a continuation of international application No. PCT/US2016/013992 filed on day 20/1 in 2016, and international application No. PCT/US2016/013992 claims the benefit of U.S. patent application No. 62/106,203 filed on day 21 in 2015 and U.S. patent application No. 62/280,652 filed on day 19/1 in 2016. The disclosure of the above application is incorporated herein by reference.

Technical Field

The present disclosure relates generally to a rocker arm assembly for a valve train (valve train) assembly and, more particularly, to a rocker arm assembly having an engine brake bridge.

Background

In addition to wheel brakes, compression engine brakes may also be used as auxiliary brakes, for example on relatively large vehicles driven by heavy or medium duty diesel engines. The compression engine brake system is arranged to provide additional opening of the exhaust valve of the engine cylinder when the piston in the cylinder is near top dead center position of its compression stroke when activated, so that compressed air can be released through the exhaust valve. This results in the engine acting as a power consuming air compressor, which slows the vehicle.

In a typical valvetrain assembly used with compression engine brakes, the exhaust valves are actuated by rocker arms that engage the exhaust valves via valve crossbars. The rocker arm rocks in response to a cam on a rotating camshaft and presses down a valve bridge, which itself presses down the exhaust valve to open it. A hydraulic lash adjuster may also be provided in the valve train assembly to remove any lash or clearance created between the components in the valve train assembly.

The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

Disclosure of Invention

In one aspect of the present disclosure, an exhaust valve rocker arm assembly is provided that selectively opens a first exhaust valve and a second exhaust valve. The assembly includes an exhaust rocker arm and a valve bridge operatively associated with the rocker arm and including a body and a lever rotatably coupled to the body. The body is configured to engage a first exhaust valve and the lever is configured to engage a second exhaust valve.

In addition to the above, the exhaust valve rocker arm assembly may include one or more of the following features: wherein the lever is at least partially disposed within the body; wherein the lever is disposed between the opposing flanges of the body; wherein the valve bridge body is configured to have an interference fit with a valve tip of the first exhaust valve; and a Hydraulic Lash Adjuster (HLA) assembly coupled between the exhaust rocker arm and the valve bridge, wherein the interference fit is configured to transmit relative motion to the HLA assembly and the second exhaust valve.

In addition to the above, the exhaust valve rocker arm assembly may include one or more of the following features: a valve seat (valve shot) rotatably coupled to the lever; wherein the valve seat is rotatably coupled to the lever by a valve seat pin extending through the lever; wherein the valve seat is configured to have an interference fit with a valve tip of the second exhaust valve; and a Hydraulic Lash Adjuster (HLA) assembly coupled between the exhaust rocker arm and the valve bridge, wherein the interference fit is configured to transfer relative motion to the HLA assembly and the first exhaust valve.

In addition to the above, the exhaust valve rocker arm assembly may include one or more of the following features: wherein the lever is coupled to the body such that rotation of the lever and engagement of the second exhaust valve occurs without rotation of the body; wherein the body includes a bore in which the lever is at least partially disposed, and wherein the lever is rotatably coupled to the body by a crossbar pin extending through the body; and wherein the lever includes an engagement surface and an opposite side opposite the engagement surface, wherein the engagement surface is configured to be engaged by the engine brake rocker arm, and the opposite side is configured to move upward against the body when the engagement surface moves downward.

In another aspect of the present disclosure, a valvetrain assembly is provided. The valvetrain assembly includes a first exhaust valve, a second exhaust valve, and an exhaust valve rocker arm assembly that selectively opens the first exhaust valve and the second exhaust valve. The exhaust valve rocker arm assembly includes an exhaust rocker arm and a valve bridge operatively associated with the rocker arm and including a body and a lever rotatably coupled to the body. The body is configured to engage a first exhaust valve and the lever is configured to engage a second exhaust valve. The engine brake rocker arm assembly includes an engine brake rocker arm configured to selectively engage and rotate the lever to open the second exhaust valve.

In addition to the above, the valvetrain assembly may include one or more of the following features: wherein the lever is at least partially disposed within the body between the opposing flanges of the body; wherein the exhaust valve bridge body has an interference fit with the valve stem head of the first exhaust valve; and a Hydraulic Lash Adjuster (HLA) assembly coupled between the exhaust rocker arm and the valve bridge, wherein the interference fit is configured to transmit relative motion to the HLA assembly and the second exhaust valve.

In addition to the above, the valvetrain assembly may include one or more of the following features: a valve seat rotatably coupled to the lever by a valve seat pin extending through the lever; wherein the valve seat and the valve rod head of the second exhaust valve have interference fit; and a Hydraulic Lash Adjuster (HLA) assembly coupled between the exhaust rocker arm and the valve bridge, wherein the interference fit is configured to transfer relative motion to the HLA assembly and the first exhaust valve.

In addition to the above, the valvetrain assembly may include one or more of the following features: wherein the engine brake rocker arm assembly further comprises an engine brake capsule coupled to the engine brake rocker arm, the engine brake capsule movable between a retracted position and an extended position, wherein in the retracted position the engine brake capsule does not engage the lever and in the extended position the engine brake capsule selectively engages the lever, wherein the engine brake capsule comprises an outer housing, a plunger, and a pin assembly, wherein the plunger is disposed in a lower chamber of the outer housing and the pin assembly is at least partially disposed in an upper chamber of the outer housing, and wherein the engine brake capsule comprises a check ball assembly disposed within the lower chamber, the pin assembly being operatively associated with the check ball assembly to selectively enable hydraulic fluid to enter the lower chamber to move the plunger from the retracted position to the extended position.

Drawings

The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

FIG. 1 is a plan view of a valve train assembly incorporating a rocker arm assembly including an intake rocker arm assembly, an exhaust rocker arm assembly, and an engine brake rocker arm assembly constructed in accordance with one example of the present disclosure;

FIG. 2 is a perspective view of the valvetrain assembly shown in FIG. 1 without the intake rocker arm assembly;

FIG. 3 is an exploded view of the exhaust valve rocker arm assembly and engine brake rocker arm assembly of FIG. 1;

FIG. 4 is a cross-sectional view of the engine brake rocker arm assembly shown in FIG. 3 and taken along line 4-4;

FIG. 5 is a perspective view of a portion of the rocker arm assembly shown in FIG. 1;

FIG. 6 is a perspective view of a valve bridge assembly of the exhaust valve rocker arm assembly of FIG. 1 constructed in accordance with an example of the present disclosure;

FIG. 7 is a plan view of a portion of the valve bridge assembly of FIG. 6;

FIG. 8 is a cross-sectional view of the rocker arm assembly shown in FIG. 5 taken along line 8-8 and during normal exhaust event actuation;

FIG. 9 is a cross-sectional view of the rocker arm assembly shown in FIG. 5 taken along line 8-8 and during actuation of a braking event;

FIG. 10 is a cross-sectional view of another exhaust rocker arm assembly during normal exhaust event actuation that may be used with the rocker arm assembly shown in FIG. 1 and constructed in accordance with one example of the present disclosure;

FIG. 11 is a cross-sectional view of the exhaust rocker arm assembly of FIG. 10 during actuation of a braking event;

FIG. 12 is a perspective view of a valve train assembly incorporating a rocker arm assembly including an intake rocker arm assembly, an exhaust rocker arm assembly, and an engine brake rocker arm assembly constructed in accordance with another example of the present disclosure;

FIG. 13 is a cross-sectional view of the valvetrain assembly shown in FIG. 12 in a first mode;

FIG. 14 is a cross-sectional view of the valvetrain assembly shown in FIG. 12 in a second mode;

FIG. 15 is a cross-sectional view of the engine brake capsule shown in FIG. 13;

FIG. 16 is a cross-sectional view of the engine brake capsule shown in FIG. 14;

FIG. 17 is a perspective view of the exemplary valve bridge assembly of FIG. 12;

FIG. 18 is a cross-sectional view of the valve train assembly of FIG. 12 with an exemplary valve bridge assembly; and is

Fig. 19 is a cross-sectional view of the valve train assembly of fig. 12 having another exemplary valve bridge assembly.

Detailed Description

Referring initially to fig. 1 and 2, a partial valvetrain assembly in accordance with one example configuration of the present disclosure is illustrated and generally identified by reference numeral 10. The local valvetrain assembly 10 utilizes engine braking and is shown configured for use in a three cylinder bank portion of a six cylinder engine. However, it should be understood that the present teachings are not so limited. In this regard, the present disclosure may be used in any valvetrain assembly that utilizes engine braking. The local valvetrain assembly 10 is supported in a valvetrain carrier 12, and may include three rocker arms per cylinder.

Specifically, each cylinder includes an intake valve rocker arm assembly 14, an exhaust valve rocker arm assembly 16, and an engine braking rocker arm assembly 18. The exhaust valve rocker arm assembly 16 and the engine braking rocker arm assembly 18 cooperate to control opening of the exhaust valves and are collectively referred to as a dual rocker arm assembly 20 (fig. 2). The intake valve rocker arm assembly 14 is configured to control movement of the intake valve, the exhaust valve rocker arm assembly 16 is configured to control exhaust valve movement in an actuation mode, and the engine braking rocker arm assembly 18 is configured to act on one of the two exhaust valves in an engine braking mode, as will be described herein.

The rocker shaft 22 is received by the valve train carrier 12 and supports rotation of the exhaust valve rocker arm assembly 16 and the engine brake rocker arm assembly 18. As described in greater detail herein, the rocker shaft 22 may communicate oil to the assemblies 16, 18 during operation. The camshaft 24 includes a lift profile or cam lobe configured to rotate the assemblies 16, 18 to actuate a first exhaust valve 26 and a second exhaust valve 28, as described in greater detail herein.

Referring now further to fig. 2 and 3, the exhaust valve rocker arm assembly 16 will be further described. The exhaust valve rocker arm assembly 16 may generally include an exhaust rocker arm 30, a valve bridge assembly 32, and a Hydraulic Lash Adjuster (HLA) assembly 36.

The exhaust rocker arm 30 includes a body 40, a shaft 42, and a roller 44. The body 40 may receive the rocker shaft 22 and define an aperture 48 configured to at least partially receive the HLA assembly 36. The shaft 42 may be coupled to the body 40 and may receive a roller 44 configured to be engaged by an exhaust lifting profile or cam lobe 50 (fig. 2) of the camshaft 24. Accordingly, when the roller 44 is engaged by the exhaust lift profile 50, the exhaust rocker arm 30 rotates downward, causing downward movement of the valve bridge assembly 32, which engages the first and second exhaust valves 26, 28 (fig. 2) associated with the cylinders of an engine (not shown).

The HLA assembly 36 is configured to take up any lash between the HLA assembly 36 and the valve bridge assembly 32. With additional reference to fig. 8 and 9, in an exemplary implementation, HLA assembly 36 may include a plunger assembly 52 including a leak down plunger or first plunger body 54 and a ball plunger or second plunger body 56. The plunger assembly 52 is received by the bore 48 defined in the rocker arm 30 and may have a first closed end defining a spigot 58 that is received in a socket 60 that acts against the valve bridge assembly 32. The second plunger body 56 has an opening defining a valve seat 62, and a check ball assembly 64 may be positioned between the first and

second plunger bodies

54, 56.

Check ball assembly 64 may be configured to retain oil within a chamber 66 between first and

second plunger bodies

54, 56. A biasing mechanism 68 (e.g., a spring) biases the second plunger body 56 upward (as shown in fig. 8 and 9) to extend the first plunger body 54 to take up any gap. As the second plunger body 56 is biased upward, oil is drawn through the check ball assembly 64 and into the chamber 66 between the

plunger bodies

54, 56. Thus, oil may be supplied from the rocker shaft 22 to a chamber within the second plunger 56 through a passage (not shown), and downward pressure may cause downward movement of the first plunger body 54 due to the oil in the chamber 66. However, the HLA assembly 36 may have any other suitable configuration that enables the assembly 36 to take up the gap between the assembly and the valve bridge assembly 32.

Referring now further to fig. 2-4, the engine braking rocker arm assembly 18 will be further described. The engine brake rocker arm assembly 18 may generally include an engine brake rocker arm 70, a shaft 72, a roller 74, an actuator or piston assembly 76, and a check valve assembly 78.

The engine brake rocker arm 70 may receive the rocker shaft 22 and may define a first aperture 80 and a second aperture 82. First orifice 80 may be configured to at least partially receive piston assembly 76, and second orifice 82 may be configured to at least partially receive check valve assembly 78. The shaft 72 may be coupled to the rocker arm 70 and may receive a roller 74 configured to be engaged by a brake lift profile or cam lobe 84 (fig. 2) of the camshaft 24. Thus, when the roller 74 is engaged by the cam lobe 84, the brake rocker arm 70 rotates downward, causing downward movement of the piston assembly 76.

As shown in fig. 3 and 4, the actuator or piston assembly 76 may include a first actuator or piston body 86, a second actuator or piston body 88, a socket 90, a biasing mechanism 92, a stop 94, and a nut 96. The piston assembly 76 may be received by the first bore 80 of the rocker arm 70. The first piston body 86 may include a first closed end defining a spigot 98 that is received in the socket 90 that acts against the valve bridge assembly 32. The second piston body 88 may be secured to the rocker arm 70 by a nut 96, and the stop 94 may be secured to the second piston body 88. The second piston body 88 and the nut 96 may be used as a fine adjustment screw to set the initial position of the piston assembly 76.

A biasing mechanism 92 (e.g., a spring) is configured to pull or retract the first piston body 86 upward into the bore 80 to a retracted position. The stop 94 may be configured to limit upward movement of the first piston body 86. Pressurized oil is selectively supplied to a chamber 102 of the first piston body 86 through a passage 100 (fig. 4) to move the piston body 86 downward and outward from the orifice 80 to an extended position. When the supply of oil to the passage 100 is suspended, the first piston body 86 is returned to the retracted position by the biasing mechanism 92.

The check valve assembly 78 is at least partially disposed in the second orifice 82 and may include a sliding or check valve 110, a biasing mechanism 112, a cap 114, and a clamp 116. The check valve assembly 78 is configured to selectively supply oil from a passage 118 (fig. 4) in the rocker shaft 22 to the passage 100. The check valve 110 may be biased to a closed position by a biasing mechanism 112 such that oil is not supplied to the passage 100. When the oil pressure in passage 118 is sufficient to open check valve 110, oil is supplied via passage 100 to actuate piston assembly 76 into the extended position. The clip 116 may nest in a radial groove provided in the second bore 82 to retain the check valve assembly 78 therein.

Many known engines with hydraulic valve lash adjustment have a single rocker arm that actuates two valves through a valve bridge that spans the valves. The engine brake bypasses the bridge and pushes one of the valves (which cocks or tilts the valve bridge) to open a single valve and exhaust the cylinder. However, with a cocked valve bridge, the HLA may react by extending to take up the resulting lash. This may be undesirable because after a braking event, the extended HLA assembly may then hold the exhaust valve open with some degree of compression loss and possible piston-valve contact.

To overcome this potentially undesirable event, the assembly 10 includes a valve bridge assembly 32 having a movable lever assembly 130 integrated therein. The lever assembly 130 may transmit some of the valve actuation force back to the HLA assembly 36 (via the crossbar 32), thereby preventing unintended extension of the HLA assembly during a braking event. Thus, the lever assembly 130 allows the valve 26 to open during engine braking operations without allowing the valve bridge assembly 32 to move downward. Moreover, the lever assembly 130 significantly reduces the actuation force required for a braking event as compared to known systems.

Referring additionally to fig. 6 and 7, in one exemplary implementation, the valve bridge assembly 32 includes a lever assembly 130 disposed within a main bridge body 132. The cross arm body 132 includes a first end 134 and a second end 136. The first end 134 may be configured to engage the valve 28, and the second end 136 may include a first bore 138, a second bore 140, and a third bore 142.

As shown in fig. 5, the lever assembly 130 may generally include a lever 150, a crossbar pin 152, a valve seat 154, and a valve seat pin 156. A lever 150 may be disposed within the first bore 138 and rotatably coupled to the cross arm body 132 by a cross arm pin 152 extending through the second and

third bores

140, 142 of the cross arm body 132.

The lever 150 includes an engagement surface 158, a first opposing opening 160, a second opposing opening 162, and a stop flange 164. The engagement surface 158 is configured to be selectively engaged by the receptacle 90 of the piston assembly 76. The first opposing opening 160 may receive the crossbar pin 152 and the second opposing opening 162 may receive the valve seat pin 156. The stop flange 164 may be configured to engage a stem 166 (fig. 6 and 7) of the cross arm body 132 to limit downward movement of the lever 150 (as shown in fig. 6).

The valve seat 154 includes a body portion 168 and an attachment portion 170 having a bore 172 formed therein. The body portion 168 is configured to receive a portion of the valve 26, and the connecting portion 170 is at least partially disposed within the lever 150 such that the connecting portion bore 172 receives the valve seat pin 156 to rotationally couple the valve seat 154 to the lever 150.

Thus, the lever 150 is selectively engageable at the engagement surface 158, which may cause rotation about the pin 156 and upward movement of the opposite side 174 of the lever opposite the surface 158 (see fig. 9). This upward movement of the lever end 174 causes upward movement of the crossbar body 132 toward the HLA assembly 36 to prevent extension thereof.

Thus, during operation of the rocker arm assembly 20, the exhaust rocker arm assembly 16 may selectively engage the valve bridge body 132 to actuate the

valves

26, 28 and perform a normal exhaust event (combustion mode); and the engine braking rocker arm assembly 18 may selectively engage the lever assembly 130 to actuate only the valve 26 and perform a braking event actuation (engine braking mode).

Piston assembly 76 is configured to move first piston body 86 between a retracted position and an extended position. In the retracted position, the first piston body 86 is retracted into the bore 80 such that the socket 90 is spaced apart from and does not contact the lever engagement surface 158 even when the cam lobe 84 of the camshaft 24 engages the engine braking rocker arm 70.

However, in the extended position, the first piston body 86 extends from the bore 80 such that the receptacle 90 is positioned to engage the lever engagement surface 158. When the cam lobe 84 of the camshaft 24 engages the engine braking rocker arm 70, the socket 90 rotates the lever about the pin 156 to engage the valve 26 and perform a braking event actuation. Fig. 4 shows the engine braking rocker arm assembly 18 with the piston assembly 76 in the extended position due to oil being supplied from the rocker shaft 22 through the passage 100. In this position, engine braking event actuation is active and the piston assembly 76 is configured to engage the lever assembly 130 (fig. 9) of the valve bridge assembly 32. The engine braking event actuation capability may be deactivated by stopping the supply of oil through passages 100 and/or 118, thereby moving piston assembly 76 to the retracted position.

Referring now to fig. 4,8 and 9, an exemplary sequence of operation of the exhaust valve rocker arm assembly 16 and the engine braking rocker arm assembly 18 will be described.

Fig. 8 shows portions of the assemblies 16, 18 during normal exhaust event actuation, with the exhaust rocker arm 30 engaged by the cam lobe 50 of the camshaft 24. Specifically, as the camshaft 24 rotates, the cam lobe 50 engages the roller 44, which causes the exhaust rocker arm 30 to rotate about the rocker shaft 22. In this motion, the exhaust rocker arm 30 pushes through the HLA assembly 36 and moves the valve bridge body 132 downward to open the first and

second exhaust valves

26, 28.

Fig. 9 shows portions of the assemblies 16, 18 during a braking event actuation, with the engine brake rocker arm 70 engaged by the cam lobe 84 of the camshaft 24. Specifically, as the camshaft 24 rotates, the cam lobe 84 engages the roller 74, which causes the brake rocker arm 70 to rotate about the rocker shaft 22. When the first piston body 86 is in the extended position, the brake rocker arm 70 pushes the socket 90 downward to engage the lever engagement surface 158 and cause it to move downward. This in turn may cause downward movement of the valve seat 154, thereby opening the valve 26 to brake the engine. In addition, as the lever 150 pivots about the pin 156, the lever end 174 moves upwardly against the crossbar body 132, which pushes against the HLA assembly 36 to prevent it from extending during a braking event.

Fig. 10 and 11 illustrate a valve bridge assembly 200 constructed in accordance with one example of the present disclosure. The valve bridge assembly 200 may be used with the valve train assembly 10 and may be similar to the valve train assembly 32, except that the valve bridge assembly may include a hydraulic actuator assembly 202 instead of the lever assembly 130. Thus, the valve bridge assembly 200 includes a hydraulic actuator assembly 202 and a valve bridge body 204 that includes a first end 206 and a second end 208. The first end 206 may be configured to engage the valve 28, and the second end 208 may include an aperture 210.

The hydraulic actuator assembly 202 may be at least partially disposed within the bore 210 and may generally include a capsule or outer housing 212, a first actuator or piston body 214, a second actuator or piston body 216, a check ball assembly 218, and a biasing mechanism 220.

The outer housing 212 defines an upper aperture 222, a lower aperture 224, and a central chamber 226. At least a portion of the second piston body 216 extends through the upper bore 222 and the lower bore 224 is configured to receive at least a portion of the exhaust valve 26. The central chamber 226 defines a space between the first and

second piston bodies

214, 216 that is configured to receive oil or other fluid from the brake rocker arm 70.

The first piston body 214 may be disposed within the outer housing 212 and may include a valve receiving slot 228 and a seat 230. The valve receiving slot 228 is configured to receive an end of the exhaust valve 26, and the seat 230 may be configured to seat at least a portion of the biasing mechanism 220.

The second piston body 216 may be at least partially disposed within the outer housing 212 and may include an oil supply passage 232 and a check ball assembly seat 234. The oil supply passage 232 is fluidly connected to a bladder 236 that is coupled to the brake rocker arm 70 and is configured to selectively receive a supply of pressurized oil from the passage 118 of the rocker shaft 22.

The check ball assembly 218 may be at least partially disposed within the check ball seat 234. The check ball assembly 218 may generally include a retainer 238, a check ball 240, and a biasing mechanism 242. A retainer 238 may be seated within the seat 234 and configured to retain a check ball 240 therein. The biasing mechanism 242 may bias the check ball against the seat 234 to seal the oil supply passage 232. Thus, check ball assembly 218 is in a normally closed position. However, the assembly 18 may be configured to have a normally open position.

The biasing mechanism 220 may have a first end seated in a seat 230 of the first piston 214 and a second end seated in a seat 234 of the second piston 216. The biasing mechanism 220 may be configured to bias the first and

second pistons

214, 216 away from each other and may secure the check ball assembly retainer 238 within the seat 234. The biased separation of the first and

second pistons

214, 216 may be used to draw oil from the passage 232 into the central chamber 226 to ensure that oil is stored therein.

Fig. 10 shows portions of the assemblies 16, 18 during normal exhaust event actuation, with the exhaust rocker arm 30 engaged by the cam lobe 50 of the camshaft 24 (see fig. 2). Specifically, as the camshaft 24 rotates, the cam lobe 50 engages the roller 44, which causes the exhaust rocker arm 30 to rotate about the rocker shaft 22. In this motion, the exhaust rocker arm 30 pushes through the HLA assembly 36 and moves the bridge body 204 downward to open the first and

second exhaust valves

26, 28.

Fig. 11 shows portions of the assemblies 16, 18 during a braking event actuation, with the engine brake rocker arm 70 engaged by the cam lobe 84 of the camshaft 24 (see fig. 2). Specifically, as the camshaft 24 rotates, the cam lobe 84 engages the roller 74, which causes the brake rocker arm 70 to rotate about the rocker shaft 22. Pressurized oil is supplied to the oil supply chamber 232 through the bladder 236. The pressurized fluid and/or the biasing mechanism 220 opens the check ball assembly 218 such that oil fills the central chamber 226.

When the braking rocker arm 70 is engaged by the cam lobe 84, the rocker arm 70 may push the capsule 236 downward to engage the second piston body 216, causing it to move downward. This downward movement of the piston body 216 may force the fluid in the central chamber 226 against the top of the first piston body 214, causing the first piston body to move downward. This may force the valve 26 downward to open and brake the engine. Additionally, the downward movement of the piston body 216 may force the fluid in the central chamber 226 upward against the inner edge 244 of the outer housing 212. This causes upward movement of the outer housing 212, which provides sufficient upward force to the valve bridge body 204 to prevent extension of the HLA assembly 36 during actuation of a braking event.

Referring to fig. 12-14, a partial valvetrain assembly constructed in accordance with another example of the present disclosure is illustrated and generally identified with reference 300. The local valvetrain assembly 300 may be similar in structure and function to the local valvetrain assembly 10 described herein. The local valvetrain assembly 300 utilizes engine braking and is shown configured for use in a three cylinder bank portion of a six cylinder engine. However, it should be understood that the present teachings are not so limited. In this regard, the present disclosure may be used in any valvetrain assembly that utilizes engine braking. The local valvetrain assembly 300 is supported in a valvetrain carrier 312 and may include three rocker arms per cylinder.

Specifically, each cylinder includes an intake valve rocker arm assembly 314, an exhaust valve rocker arm assembly 316, and an engine braking rocker arm assembly 318. The exhaust valve rocker arm assembly 316 and the engine braking rocker arm assembly 318 cooperate to control the opening of the exhaust valves and are collectively referred to as a dual rocker arm assembly 320. The intake valve rocker arm assembly 314 is configured to control movement of the intake valve, the exhaust valve rocker arm assembly 316 is configured to control movement of the exhaust valve in an actuation mode, and the engine braking rocker arm assembly 318 is configured to act on one of the two exhaust valves in an engine braking mode, as will be described herein.

The rocker shaft 322 is received by the valve train carrier 312 and supports rotation of the exhaust valve rocker arm assembly 316 and the engine brake rocker arm assembly 318. As described in more detail herein, the rocker shaft 322 may communicate oil to the

assemblies

316, 318 during operation. The camshaft 324 includes a lift profile or cam lobe configured to rotate the

assemblies

316, 318 to actuate a first exhaust valve 326 and a second exhaust valve 328, as described in greater detail herein.

The exhaust valve rocker arm assembly 316 is similar to the exhaust valve rocker arm assembly 16 and may generally include an exhaust valve rocker arm 330, a valve bridge assembly 332, and an HLA assembly 336, which may be similar to the HLA assembly 36.

The engine brake rocker arm assembly 318 may generally include an engine brake rocker arm 370 and an engine brake capsule 376. The engine brake rocker 370 may receive the rocker shaft 322 and may define an aperture 380 configured to at least partially receive the engine brake capsule 376. Rocker arm 370 is configured to be engaged by a brake lift profile or cam lobe (e.g., lobe 84) of camshaft 324 to rotate brake rocker arm 370 downward, causing engine brake capsule 376 to move downward.

With further reference to fig. 15 and 16, actuator or engine brake capsule 376 may generally include an outer housing 500, a plunger 502, and a top cover 504. The outer housing 500 may be received by the bore 380 of the rocker arm 370 and may generally include a lower chamber 506, an intermediate chamber 508, and an upper chamber 510. The plunger 502 is slidably received within the lower chamber 506 and is configured to act against the valve bridge assembly 332.

A check ball assembly 512 may be disposed in the lower chamber 506. Check ball assembly 512 may be configured to retain oil within a space or region 514 between plunger 502 and intermediate chamber 508. A pin assembly 516 is disposed in the upper chamber 510 and includes a body 518 and a pin arm 520. The body 518 defines a seat 522 configured to receive a biasing mechanism 524 (e.g., a spring), and a pin arm 520 extends downwardly from the body into the intermediate chamber 508. Biasing mechanism 524 is configured to bear against cap 504 and bias pin assembly 516 downward into contact with check ball assembly 512.

Oil may be supplied to the intermediate chamber 508 via, for example, the rocker shaft 322 and through the port 526. The upward pressure of the fluid supply compresses biasing mechanism 524, causing pin assembly 516 to move away from check ball assembly 512. This movement allows oil in the intermediate chamber 508 to fill the area 514 and move the plunger 502 downward and outward to an extended position to engage the valve bridge assembly 332 (e.g., a braking mode). When the oil supply is stopped, when the plunger 502 is in contact with the valve bridge assembly 332 (e.g., drive mode), the oil in the intermediate chamber 508 may be at least partially drained, and the plunger 502 may be able to slide upward into the lower chamber 506.

Accordingly, the engine brake bladder 376 may be selectively operated between a braking mode (fig. 14 and 16) and a driving mode (fig. 13 and 15). In the braking mode, pressurized oil is selectively supplied to the port 526 to move the plunger downward into the extended position. In the drive mode, the supply of oil to the port 526 is suspended and the plunger 502 is returned to the retracted position within the lower chamber 506 of the outer housing 500.

With additional reference to fig. 17, the valvetrain assembly 300 includes a valve bridge assembly 332 to overcome the potentially undesirable events described above with respect to conventional valve bridges. In an exemplary embodiment, the valve bridge assembly 332 includes a movable lever assembly 430 integrated therein that may transmit some of the valve actuation force back to the HLA assembly 336 (via the bridge 332) to prevent unintended extension of the HLA during a braking event. Thus, the lever assembly 330 allows the valve 326 to open during engine braking operations without allowing the valve bridge assembly 332 to move downward. Moreover, the lever assembly 430 significantly reduces the actuation force required for a braking event as compared to known systems.

In the illustrated example, the valve bridge assembly 332 includes a lever assembly 430 disposed within a bridge body 432. The crossbar body 432 includes a first end 434 and a second end 436. The first end 434 may be configured to engage the valve 328, and the second end 436 may include a cutout 438 and opposing

apertures

440 and 442.

As shown in FIG. 17, lever assembly 430 may generally include a lever 450, a crossbar pin 452, a valve seat 454, and a valve seat pin 456. The lever 450 may be at least partially disposed within the cutout 438 and rotatably coupled to and within the cross arm body 432 by a cross arm pin 452 that extends through the opposing

bores

440, 442 of the cross arm body 432. In addition, the lever 450 may be disposed between the opposing flanges 444 of the cross arm body 432.

The lever 450 includes an engagement surface 458, a first opposing opening 460 and a second opposing opening 462. The engagement surface 458 is configured to be selectively engaged by the plunger 502 of the piston assembly 376. A first opposing opening 460 may receive the cross arm pin 452 and a second opposing opening 462 may receive the valve seat pin 456.

The valve seat 454 includes a body portion 468 having a bore 472 formed therein. The body portion 468 is configured to receive a portion of the valve 326 and also to receive the valve seat pin 456 to rotatably couple the valve seat 454 to the lever 450.

Thus, the lever 450 is selectively engageable at the engagement surface 458, which may cause rotation about the pin 456 and upward movement of the opposite side 474 of the lever opposite the surface 458 (see fig. 18 and 19). This upward movement of the lever end 474 causes upward movement of the cross arm body 432 toward the HLA assembly 336 to prevent extension thereof.

Thus, during operation of the rocker arm assembly 320, the exhaust rocker arm assembly 316 may selectively engage the valve bridge body 432 to actuate the

valves

326, 328 and perform a normal exhaust event (combustion mode); and the engine braking rocker arm assembly 318 may selectively engage the lever assembly 430 to actuate only the valve 326 and perform a braking event actuation (engine braking mode).

Engine brake capsule 376 is configured to move plunger 502 between a retracted position and an extended position. In the retracted position, plunger 502 is retracted into outer housing lower chamber 504 such that plunger 502 is spaced apart from and does not contact lever engagement surface 458 even when a cam lobe (e.g., lobe 84) of camshaft 324 engages engine brake rocker arm 370.

However, in the extended position, the plunger 502 extends from the outer housing lower chamber 502 such that the plunger 502 is positioned to engage the lever engagement surface 458. When the cam lobe engages the engine braking rocker 370, the plunger 502 rotates the lever 450 about the pin 456 to engage the valve 326 and perform a braking event actuation. Fig. 14 and 16 show the engine brake capsule 376 in an extended position due to the supply of oil through port 526. In this position, engine braking event actuation is active and the engine brake capsule 376 is configured to engage the lever assembly 430 of the valve bridge assembly 332. The engine braking event actuation capability may be deactivated by stopping the supply of oil through the port 526, thereby moving the engine braking capsule 376 to the retracted position.

In an exemplary embodiment shown in fig. 18, the valve tip motion of the valve 326 may be constrained (e.g., a close tolerance or interference fit) within the valve seat 454. Thus, during a braking operation, the pivot arm will produce relative motion between the valve 326 and the valve bridge assembly 332. In this arrangement, the brake valve 326 is restricted and relative motion is transferred to the HLA 336 and the valve 328.

In another exemplary embodiment shown in fig. 19, valve tip motion of the valve 328 may be constrained within a valve bridge body 432. Thus, during a braking operation, the brake valve 328 is restricted and relative motion is transferred to the HLA 336 and the valve 326.

Systems and methods for braking an engine are described herein. The system includes an exhaust valve rocker arm that engages a valve bridge to actuate two valves to perform an exhaust event. In one aspect, the valve bridge includes a body and a lever integrated therein, the internal lever being rotatable relative to the valve bridge body. The rotatable lever is selectively engageable and rotatable by the engine braking rocker arm to actuate one of the two valves to perform an engine braking event.

Further, the lever may simultaneously transmit some of the valve actuation force back to the HLA assembly, thereby preventing unintended extension of the HLA assembly during a braking event. Thus, the internal lever allows the valve to open during engine braking operation without cocking or rotating the body, which may cause unintended extension. In addition, the lever assembly significantly reduces the actuation force required for a braking event as compared to known systems. In another aspect, the valve bridge may include a hydraulic actuator assembly that utilizes a hydraulic intensifier to multiply the load (reduce the stroke) while transferring some of the load to the bridge and HLA.

The foregoing description of these examples has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular example are generally not limited to that particular example, but, where applicable, are interchangeable and can be used in a selected example, even if not specifically shown or described. Which can also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

1. An exhaust valve rocker arm assembly that selectively opens a first exhaust valve and a second exhaust valve and that comprises:

an exhaust rocker arm; and

a valve bridge operatively associated with the rocker arm and including a body and a lever rotatably coupled to the body, the body configured to engage the first exhaust valve, and the lever configured to engage the second exhaust valve.

2. The assembly of claim 1, wherein the lever is at least partially disposed within the body.

3. The assembly of claim 2, wherein the lever is disposed between opposing flanges of the body.

4. The assembly of claim 1, wherein the valve bridge body is configured to have an interference fit with a valve tip of the first exhaust valve.

5. The assembly of claim 4, further comprising a Hydraulic Lash Adjuster (HLA) assembly coupled between the exhaust rocker arm and the valve bridge, wherein the interference fit is configured to transfer relative motion to the HLA assembly and the second exhaust valve.

6. The assembly of claim 1, further comprising a valve seat rotatably coupled to the lever.

7. The assembly of claim 6, wherein the valve seat is rotatably coupled to the lever by a valve seat pin extending through the lever.

8. The assembly of claim 7, wherein the valve seat is configured to have an interference fit with a valve tip of the second exhaust valve.

9. The assembly of claim 8, further comprising a Hydraulic Lash Adjuster (HLA) assembly coupled between the exhaust rocker arm and the valve bridge, wherein the interference fit is configured to transfer relative motion to the HLA assembly and the first exhaust valve.

10. The assembly of claim 1, wherein the lever is coupled to the body such that rotation of the lever and engagement of the second exhaust valve occurs without rotation of the body.

11. The assembly of claim 1, wherein the body includes a bore in which the lever is at least partially disposed, and wherein the lever is rotatably coupled to the body by a crossbar pin extending through the body.

12. The assembly of claim 1, wherein the lever includes an engagement surface and an opposite side opposite the engagement surface, wherein the engagement surface is configured to be engaged by an engine brake rocker arm, and the opposite side is configured to move upward against the body when the engagement surface moves downward.

13. A valve train assembly comprising:

a first exhaust valve;

a second exhaust valve;

an exhaust valve rocker arm assembly that selectively opens the first and second exhaust valves and that includes:

an exhaust rocker arm; and

a valve bridge operatively associated with the rocker arm and including a body and a lever rotatably coupled to the body, the body configured to engage the first exhaust valve and the lever configured to engage the second exhaust valve; and

an engine brake rocker arm assembly including an engine brake rocker arm configured to selectively engage and rotate the lever to open the second exhaust valve.

14. The assembly of claim 13, wherein the lever is at least partially disposed within the body between opposing flanges of the body.

15. The assembly of claim 13, wherein the exhaust has an interference fit with the valve bridge body and the valve stem head of the first exhaust valve.

16. The assembly of claim 15, further comprising a Hydraulic Lash Adjuster (HLA) assembly coupled between the exhaust rocker arm and the valve bridge, wherein the interference fit is configured to transfer relative motion to the HLA assembly and the second exhaust valve.

17. The assembly of claim 13, further comprising a valve seat rotatably coupled to the lever by a valve seat pin extending through the lever.

18. The assembly of claim 17, wherein the valve seat has an interference fit with a valve tip of the second exhaust valve.

19. The assembly of claim 18, further comprising a Hydraulic Lash Adjuster (HLA) assembly coupled between the exhaust rocker arm and the valve bridge, wherein the interference fit is configured to transfer relative motion to the HLA assembly and the first exhaust valve.

20. The assembly of claim 13, wherein the engine brake rocker arm assembly further comprises an engine brake capsule coupled to the engine brake rocker arm, the engine brake capsule being movable between a retracted position and an extended position, wherein in the retracted position the engine brake capsule does not engage the lever and in the extended position the engine brake capsule selectively engages the lever,

wherein the engine brake capsule comprises an outer housing, a plunger and a pin assembly,

wherein the plunger is disposed in a lower chamber of the outer housing and the pin assembly is at least partially disposed in an upper chamber of the outer housing, an

Wherein the engine braking capsule includes a check ball assembly disposed within the lower chamber, the pin assembly being operatively associated with the check ball assembly to selectively enable hydraulic fluid to enter the lower chamber to move the plunger from the retracted position to the extended position.