CN113167137B - Rocker arm assembly for engine braking - Google Patents

Abstract

The present application provides an exhaust valve rocker arm assembly 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 the first exhaust valve and the lever is configured to engage the second exhaust valve.

Description

Rocker arm assembly for engine braking

Cross Reference to Related Applications

The present application claims priority from U.S. application Ser. No. 16/195,120, filed 11/19/2018, which U.S. application Ser. No. 16/195,120 is part of the continuation-in-progress application of U.S. application Ser. No. 15/654,877 filed 7/20/2017, which U.S. application Ser. No. 15/654,877 is a continuation of International application Ser. No. PCT/US2016/013992 filed 1/20/2016, which International application Ser. No. PCT/US2016/013992 claims the benefit of U.S. patent application Ser. No. 62/106,203 filed 21/2015 and U.S. patent application Ser. No. 62/280,652 filed 1/19/2016. The disclosures of the above applications are incorporated herein by reference.

Technical Field

The present disclosure relates generally to a rocker arm assembly for a valve train assembly, and more particularly to a rocker arm assembly having an engine braking cross arm.

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 braking system is arranged to, when activated, provide additional opening of the exhaust valve of the cylinder when the piston in the engine cylinder is near the top dead centre position of its compression stroke, 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 down the vehicle.

In a typical valve train assembly used with a compression engine brake, the exhaust valve is actuated by a rocker arm that engages the exhaust valve via a valve bridge. The rocker arm rocks in response to rotating cams on the camshaft and presses down on the valve bridge, which itself presses down on the exhaust valve to open it. A hydraulic lash adjuster may also be provided in the valve train assembly to remove any lash or play 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 the first exhaust valve and the lever is configured to engage the 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 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 transfer 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 slide) 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 head 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, the lever is at least partially disposed within the bore, and wherein the lever is rotatably coupled to the body by a cross arm 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 upwardly against the body when the engagement surface moves downwardly.

In another aspect of the present disclosure, a valve train 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 the first exhaust valve and the lever is configured to engage the second exhaust valve. The engine brake rocker arm assembly includes an engine brake rocker arm configured to selectively engage and rotate a 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 opposing flanges of the body; wherein the exhaust wherein the valve bridge body has an interference fit with a valve 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 transfer 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 has an interference fit with the valve head 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 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 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, 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 valvetrain assembly incorporating a rocker arm assembly including an intake rocker arm assembly, an exhaust rocker arm assembly, and an engine brake rocker arm assembly configured according to one example of the present disclosure;

FIG. 2 is a perspective view of the valvetrain assembly of 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 shown in FIG. 1, constructed in accordance with one example of the present disclosure;

FIG. 7 is a plan view of a portion of the valve bridge assembly shown in 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 actuation of a normal exhaust event;

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 that may be used with the rocker arm assembly shown in FIG. 1 during normal exhaust event actuation 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 a braking event actuation;

FIG. 12 is a perspective view of a valvetrain assembly incorporating a rocker arm assembly including an intake rocker arm assembly, an exhaust rocker arm assembly, and an engine brake rocker arm assembly configured according to another example of the present disclosure;

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

FIG. 14 is a cross-sectional view of the valve train 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 example valve bridge assembly shown in FIG. 12;

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

FIG. 19 is a cross-sectional view of the valve train assembly shown in FIG. 12 with another exemplary valve bridge assembly.

Detailed Description

Referring initially to fig. 1 and 2, a partial valve train assembly constructed in accordance with one example of the present disclosure is shown and generally identified by reference numeral 10. The partial 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 valve train assembly that utilizes engine braking. The partial valve train assembly 10 is supported in a valve train 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 brake rocker arm assembly 18. The exhaust valve rocker arm assembly 16 and the engine brake rocker arm assembly 18 cooperate to control the 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 the actuated mode, and the engine brake rocker arm assembly 18 is configured to act on one of the two exhaust valves in the engine brake 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 more detail herein, the rocker shaft 22 may transfer 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 the first and second exhaust valves 26, 28, as described in more 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 lift profile or cam lobe 50 (fig. 2) of the camshaft 24. Thus, as 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 that engages the first and second exhaust valves 26, 28 (FIG. 2) associated with the cylinders of the engine (not shown).

The HLA assembly 36 is configured to occupy any gap between the HLA assembly 36 and the valve bridge assembly 32. Referring additionally to fig. 8 and 9, in one 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 aperture 48 defined in the rocker arm 30 and may have a first closed end defining a tap 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 plunger body 54 and the second plunger body 56.

The check ball assembly 64 may be configured to retain oil within a chamber 66 between the first plunger body 54 and the second plunger body 56. The 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 occupy any gap. When 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. Accordingly, oil may be supplied from the rocker shaft 22 to the 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 occupy the gap between the assembly and the valve bridge assembly 32.

Referring now further to fig. 2-4, the engine brake 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. The first aperture 80 may be configured to at least partially receive the piston assembly 76 and the second aperture 82 may be configured to at least partially receive the 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 roller 74 is engaged by cam lobe 84, brake rocker arm 70 rotates downward, causing downward movement of 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 a first bore 80 of the rocker arm 70. The first piston body 86 may include a first closed end defining a tap 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 a stop 94 may be secured to the second piston body 88. The second piston body 88 and nut 96 may be used as a trim screw to set the initial position of the piston assembly 76.

The 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 downwardly and outwardly from the orifice 80 to an extended position. When the oil supply 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 aperture 82 and may include a spool 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 no oil is 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 aperture 82 to retain the check valve assembly 78 therein.

Many known engines with hydraulic lash adjustment have a single rocker arm that actuates the valves through a valve bridge that spans both valves. The engine brake bypasses the bridge and pushes one of the valves (which cocks or tilts the bridge) to open a single valve and exhaust the cylinder. However, due to the cocked valve bridge, the HLA may react by extending to occupy the gap created. 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 cross arm 32), thereby preventing unintended extension of the HLA assembly during braking events. 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. Furthermore, the lever assembly 130 significantly reduces the actuation force required for a braking event as compared to known systems.

With additional reference 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 bridge 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 aperture 138, a second aperture 140, and a third aperture 142.

As shown in fig. 5, the lever assembly 130 may generally include a lever 150, a bridge 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 bridge body 132 by a bridge pin 152 that extends through the second and third bores 140, 142 of the bridge 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 bridge 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 bridge 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 a connecting portion 170 having an aperture 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 may be selectively engaged 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 cross arm 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 normal exhaust events (combustion mode); while the engine brake rocker arm assembly 18 may selectively engage the lever assembly 130 to actuate only the valve 26 and perform braking event actuation (engine braking mode).

The piston assembly 76 is configured to move the 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 from and does not contact the lever engagement surface 158 even when the cam lobe 84 of the camshaft 24 engages the engine brake rocker arm 70.

However, in the extended position, the first piston body 86 extends from the aperture 80 such that the socket 90 is positioned to engage the lever engagement surface 158. When the cam lobe 84 of the camshaft 24 engages the engine brake 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 brake rocker arm assembly 18 with the piston assembly 76 in an 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 brake rocker arm assembly 18 will be described.

Fig. 8 shows portions of the assemblies 16, 18 during actuation of a normal exhaust event, wherein the exhaust rocker arm 30 is engaged by the cam lobe 50 of the camshaft 24. Specifically, as the camshaft 24 rotates, the cam lobes 50 engage the rollers 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 actuation of a braking event, wherein the engine brake rocker arm 70 is engaged by the cam lobe 84 of the camshaft 24. Specifically, as camshaft 24 rotates, cam lobe 84 engages roller 74, which causes brake rocker arm 70 to rotate about 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, opening the valve 26 to brake the engine. Further, as the lever 150 pivots about the pin 156, the lever end 174 moves upward against the bridge 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. Accordingly, the valve bridge assembly 200 includes a hydraulic actuator assembly 202 and a valve bridge body 204 including 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 piston body 214 and the second piston body 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 capsule 236 coupled to the brake rocker arm 70 and configured to selectively receive a pressurized oil supply 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, the 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 piston 214 and the second piston 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 actuation of a normal exhaust event, wherein the exhaust rocker arm 30 is engaged by the cam lobe 50 of the camshaft 24 (see fig. 2). Specifically, as the camshaft 24 rotates, the cam lobes 50 engage the rollers 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 main body 204 downward to open the first and second exhaust valves 26, 28.

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

When the brake 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 the second piston body to move downward. This downward movement of the piston body 216 may force fluid in the central chamber 226 against the top of the first piston body 214, thereby causing the first piston body to move downward. This may force the valve 26 downward to open and brake the engine. Additionally, downward movement of the piston body 216 may force 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 the braking event.

Referring to fig. 12-14, a partial valve train assembly constructed in accordance with another example of the present disclosure is illustrated and generally identified with reference 300. The partial valve train assembly 300 may be similar in structure and function to the partial valve train assembly 10 described herein. The partial 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 valve train assembly that utilizes engine braking. The partial valve train assembly 300 is supported in a valve train 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 brake rocker arm assembly 318. The exhaust valve rocker arm assembly 316 and the engine brake 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 exhaust valve movement in the actuated mode, and the engine brake rocker arm assembly 318 is configured to act on one of the two exhaust valves in the engine brake 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 greater detail herein, the rocker shaft 322 may transfer 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 the first exhaust valve 326 and the second exhaust valve 328, as described in more 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 arm 370 may receive the rocker shaft 322 and may define an aperture 380 configured to at least partially receive the engine brake capsule 376. The rocker arm 370 is configured to be engaged by a brake lift profile or cam lobe (e.g., lobe 84) of the cam shaft 324 to rotate the brake rocker arm 370 downward, thereby causing the engine brake capsule 376 to move downward.

With further reference to fig. 15 and 16, the actuator or engine brake capsule 376 may generally include an outer housing 500, a plunger 502, and a overcap 504. The outer housing 500 may be received by the aperture 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. The check ball assembly 512 may be configured to retain oil within a space or region 514 between the plunger 502 and the 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 abut overcap 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 the biasing mechanism 524 causing the pin assembly 516 to move away from the check ball assembly 512. This movement allows the 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., braking mode). When the oil supply is stopped, oil in the intermediate chamber 508 may be at least partially drained when the plunger 502 is in contact with the valve bridge assembly 332 (e.g., drive mode), and the plunger 502 may be able to slide upward into the lower chamber 506.

Thus, the engine brake capsule 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 port 526 to move the plunger downward into the extended position. In the drive mode, the supply of oil to port 526 is suspended and plunger 502 returns to the retracted position within lower chamber 506 of outer housing 500.

With additional reference to FIG. 17, the valve train assembly 300 includes a valve bridge assembly 332 to overcome the potentially undesirable events described above with respect to conventional valve bridge. 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 braking events. 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. Furthermore, 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 bridge 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 holes 440 and 442.

As shown in fig. 17, the lever assembly 430 may generally include a lever 450, a cross arm 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 bridge body 432 by a bridge pin 452 that extends through the opposed apertures 440, 442 of the bridge body 432. Further, a lever 450 may be disposed between the opposing flanges 444 of the bridge 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. The first opposing opening 460 may receive the bridge pin 452 and the second opposing opening 462 may receive the valve seat pin 456.

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

Thus, the lever 450 may be selectively engaged at the engagement surface 458, which may cause rotation about the pin 456 and upward movement of an 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 normal exhaust events (combustion mode); while the engine brake rocker arm assembly 318 may selectively engage the lever assembly 430 to actuate only the valve 326 and perform braking event actuation (engine braking mode).

The engine braking capsule 376 is configured to move the plunger 502 between a retracted position and an extended position. In the retracted position, the plunger 502 is retracted into the outer housing lower chamber 504 such that the plunger 502 is spaced from and does not contact the lever engagement surface 458 even when the cam lobe (e.g., lobe 84) of the cam shaft 324 engages the 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 brake rocker arm 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 the port 526. In this position, engine braking event actuation is active and the engine braking 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 oil supply through port 526, thereby moving the engine braking capsule 376 to the retracted position.

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

In another exemplary embodiment shown in FIG. 19, the valve tip motion of the valve 328 may be constrained within the valve bridge body 432. Thus, during braking operations, the brake valve 328 is constrained 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 exhaust events. In one aspect, a 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 an 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, preventing unintended extension of the HLA assembly during braking events. Thus, the internal lever allows the valve to open during engine braking operations 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 multiplies the load (reduces stroke) with a hydraulic intensifier while transferring some of the load to the bridge and HLA.

The foregoing description of these examples has been provided for the purposes of illustration and description. And are 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 are interchangeable where applicable and can be used in a selected example, even if not specifically shown or described. Which may 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 (7)

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

an exhaust rocker arm;

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

wherein the valve bridge is engaged with the first exhaust valve and the second exhaust valve such that at least one of: (i) The second exhaust valve is constrained within a valve seat coupled to the lever, and (ii) the first exhaust valve is constrained within a body of the valve bridge.

2. The exhaust valve rocker arm assembly of claim 1 wherein the second exhaust valve is constrained within the valve seat such that relative motion is transferred to the first exhaust valve and the exhaust rocker arm during a braking operation in which the lever engages the second exhaust valve.

3. The exhaust valve rocker arm assembly of claim 2 wherein the relative motion is transferred to a hydraulic lash adjuster of the exhaust rocker arm.

4. The exhaust valve rocker arm assembly of claim 2 wherein the second exhaust valve is constrained within the valve seat by a tight tolerance or interference fit.

5. The exhaust valve rocker arm assembly of claim 1 wherein the first exhaust valve is constrained within the body of the valve bridge such that during a braking operation in which the lever engages the second exhaust valve, relative motion is transferred to the second exhaust valve and the exhaust rocker arm.

6. The exhaust valve rocker arm assembly of claim 5 wherein the relative motion is transferred to a hydraulic lash adjuster of the exhaust rocker arm.

7. The exhaust valve rocker arm assembly of claim 5 wherein the first exhaust valve is constrained within the valve bridge body by a tight tolerance or interference fit.