Cylinder deactivation with constant recharge via brake rocker arm

Abstract

A valve train assembly includes a rocker assembly for actuating a brake valve. The rocker assembly includes a rocker arm rotatable about a rocker shaft. An actuator is on a valve end of the rocker arm. The actuator is movable between an extended position and a retracted position by a first predetermined distance. A cam is configured to engage a cam side of the rocker arm. The cam has a recharge lift profile dimensioned to move the valve end of the rocker arm according to valve lift profile that has a maximum height in excess of the first predetermined distance.

Description

CYLINDER DEACTIVATION WITH CONSTANT RECHARGE VIA BRAKE ROCKER ARMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of provisional US patent application Ser. No. 63 / 510,681, filed June 28, 2023, the contents of which are incorporated herein by reference in their entirety.BACKGROUND

[0002] Cylinder Deactivation (CDA) encompasses engine management control methods defined by shutting off fueling and valve motion to select cylinders of a multi-cylinder engine. For example, in a half-engine CDA mode, half of the cylinders are deactivated such that their valves are closed and no pumping of air through the combustion chamber occurs. CDA can be applied to internal combustion engines to help improve performance in areas such as fuel consumption and thermal management. For example, CDA implementation can be used to reduce fuel consumption by cutting fuel to cylinders in idle, coasting, or low engine load situations where the amount of fuel consumed is less than what is required to power the engine and CDA implementation can improve thermal management by avoiding the pumping of cold air through the engine.

[0003] During CDA, gas is trapped inside the closed combustion chamber inside the cylinder. However, even when the combustion chamber is closed, leakage is still possible through small gaps at the piston rings. Overtime, the pressure of the gas inside the combustion chamber dissipates as the gas gradually leaks out. Eventually, a negative pressure can develop in the combustion chamber, which can lead to unwanted oil leaks to the inside of the cylinder. The presence of oil in the combustion chamber combined with low temperatures can be harmful to engine operation and in extreme cases, crystals can form from the trapped vapors inside the cylinder.BRIEF SUMMARY

[0004] There is provided a valve train assembly for a combustion engine. The valve train assembly includes a rocker assembly for actuating a brake valve. The rocker assembly includes a rocker arm rotatable about a rocker shaft. An actuator is on a valve end of the rocker arm. The actuator is movable between an extended position and a retracted position by a first predetermined distance. A cam is configured to engage a cam side of the rocker arm. The cam has a recharge lift profile dimensioned to move the valve end of the rocker arm according to valve lift profile that has a maximum height in excess of the first predetermined distance.

[0005] In the foregoing valve train assembly, there is further included a second rocker assembly for actuating a valve bridge. The valve bridge is configured to actuate the brake valve and an exhaust valve. The second rocker assembly includes a first rocker arm defining a cam end of the second rocker assembly. A second rocker arm defines a valve end of the second rocker assembly. The valve end is configured to actuate the valve bridge wherein the first rocker arm and the second rocker arm are independently rotatable about a second rocker shaft. A latch assembly is movable between a latched position wherein the first rocker arm is coupled to the second rocker arm and an unlatched position wherein the first rocker arm is uncoupled from the second rocker arm. A second cam is configured to engage the cam end of the second rocker assembly. The second cam has an exhaust lift profile for actuating the brake valve and the exhaust valve via the valve bridge at predetermined intervals, wherein the recharge lift profile aligns with the predetermined intervals of the exhaust lift profile.

[0006] In the foregoing valve train assembly, the valve bridge includes a bridge pin that is movable relative to a body of the valve bridge. The bridge pin is positioned to engage the brake valve to allow the brake valve to move independent of the valve bridge.

[0007] In the foregoing valve train assembly, when the actuator is in the extended position, a gap is formed between a distal end of the actuator and the bridge pin.

[0008] In the foregoing valve train assembly, the cam further includes a compression lift profile for actuating the brake valve according to a second valve lift profile, wherein the compression lift profile is spaced from the recharge lift profile.

[0009] In the foregoing valve train assembly, the second valve lift profile has a maximum height less than the first predetermined distance.

[0010] In the foregoing valve train assembly, the exhaust lift profile is configured to acuate the brake valve and the exhaust valve according to a third valve lift profile that aligns with the valve lift profile and that is at all instances greater than the valve lift profile.

[0011] In the foregoing valve train assembly, the brake valve and the exhaust valve are configured to open and close exhaust openings in a combustion chamber.

[0012] In the foregoing valve train assembly, the valve end of the second rocker assembly includes an elephant foot configured to engage the valve bridge.

[0013] There is further provided a method for operating an exhaust valve and a brake valve of a combustion engine. The brake valve and the exhaust valve are both actuated by a valve bridge and the brake valve movable relative to the valve bridge. The method includes during a cylinder deactivation mode wherein the valve bridge is not actuated, periodicallyallowing air to enter a cylinder of the combustion engine by periodically actuating the brake valve.

[0014] In the foregoing method, a rocker assembly has a first rocker arm and a second rocker arm that selectively coupled together via a latch assembly and a second rocker assembly has an actuator for selectively actuating the brake valve, wherein during a drive mode the first rocker arm and the second rocker arm are coupled together to actuate the valve bridge and the actuator is in a retracted position wherein the brake valve is not actuated by second rocker assembly.

[0015] In the foregoing method, during a brake mode the first rocker arm and the second rocker arm are coupled together to actuate the valve bridge and the actuator is in an extended position wherein the brake valve is actuated by second rocker assembly.BRIEF DESCRIPTIONS OF THE SEVERAL VIEWS OF THE DRAWINGS

[0016] FIG. 1 A illustrates a valve train assembly according to the present embodiment;

[0017] FIG. IB is a section view taken from FIG. 1A, showing a latch assembly of a rocker arm assembly of the valve train assembly of FIG. 1 A;

[0018] FIG. 2 illustrates a main rocker arm assembly of the rocker assembly of FIG.1 A, wherein a first rocker arm and a second rocker arm are latched together;

[0019] FIG. 3 illustrates a main rocker arm assembly of the rocker assembly of FIG. 1 A, wherein a first rocker arm and a second rocker arm are unlatched;

[0020] FIG. 4A illustrates a profile of a first cam of the valve train assembly of FIG. 1A;

[0021] FIG. 4B illustrates a profile of a second cam of the valve train assembly of FIG. 1A;

[0022] FIG. 5 illustrates lift profiles for the first and second cams of the valve train assembly of FIG. 1A, showing which lift profiles are active and inactive during a drive mode;

[0023] FIG. 6 illustrates the valve train assembly of FIG. 1A, wherein an actuator of a brake rocker arm is in an extended position during a brake mode;

[0024] FIG. 7 illustrates lift profiles for the first and second cams of the valve train assembly of FIG. 1 A, showing which lift profiles are active and inactive during a brake mode;

[0025] FIG. 8 illustrates the valve train assembly of FIG. 1A, wherein an actuator of the brake rocker arm is in a retracted position and the main rocker arm assembly is in lost motion during a CDA mode;

[0026] FIG. 13 illustrates lift profiles for the first and second cams of the valve train assembly of FIG. 1A, showing which lift profiles are active and inactive during a CDA mode;

[0027] FIG. 10 illustrates an enlarged view of a portion of a combustion chamber showing brake and exhaust valves in a closed position; and

[0028] FIG. 11 illustrates an enlarged view of a portion of a combustion chamber showing a brake valve in a recharge opening position.DETAILED DESCRIPTIONS OF THE DRAWINGS

[0029] Considering the above, there is a need for a way to gradually re-introduce gas into the combustion chamber to avoid the unwanted effects of negative pressure forming inside the combustion chamber. As will be described in detail below, a small valve opening can be periodically provided to deactivated cylinders in a CDA mode so that gas may enter the combustion chamber and prevent negative pressure from forming. According to the disclosure, the valve opening is provided by a rocker assembly controlling a brake valve and an exhaust valve to a cylinder of a combustion engine. The brake valve may be, for example, an exhaust valve for an engine brake. The rocker assembly may periodically open the brake valve for a deactivated cylinder during a CDA mode to allow small influxes of air into the combustion chamber.

[0030] Referring to FIG. 1 A, a rocker arm assembly 100 includes, in general, a first or main rocker assembly 102 and a second or brake rocker assembly 104. The main rocker assembly 102 has a first rocker arm 106, a second rocker arm 108, a latch assembly 110 and a rocker bore 113. The latch assembly 110 can selectively couple the first rocker arm 106 to the second rocker arm 108 together.

[0031] The second rocker arm 108 of the main rocker assembly 102 may include an actuation pin 112 attached to a valve end thereof. The actuation pin 112 may include an elephant foot (e-foot) 115 at a distal end thereof that is configured to engage a valve bridge 114. The valve bridge 114, in turn, causes the valves 116, 118 to be displaced. The exhaust valve 116 and the brake valve 118 may be positioned to engage the valve bridge 114. Thus, motion of the valve bridge 114 may result in motion to the exhaust valve 116 and the brake valve 118.

[0032] Referring to FIG. IB, the latch assembly 110 includes a latch pin 110a, an actuation piston 110b, a latch piston 110c, a spring 1 lOd and first and second caps 1 lOe, 1 lOf. The latch pin 110a is dimensioned and positioned to be partially received in the first rocker arm 106 and the second rocker arm 108. The actuation piston 110b is positioned between thefirst cap 1 lOe and the latch pin 110a and the latch piston 110c is positioned adjacent an opposite end of the latch pin 110a. The spring HOd is compressed between the latch piston 110c and the second cap 11 Of to bias the latch piston 110c, the latch pin 110a and the actuation piston 110b toward the first cap 1 lOe. When the latch pin 110a is partially received in both the first rocker arm 106 and the second rocker arm 108 (also referred to as a “latched position” of the latch pin assembly 110) and the first rocker arm 106 is actuated by the first cam 128, the first rocker arm 106 and the second rocker arm 108 pivot about the main rocker shaft as a unitary body.

[0033] When a lost motion is desired, i.e., when it is desired that motion from the first cam 128 is not translated to the valve end, pressurized fluid is supplied to a space between the first cap 1 lOe and the actuation piston 110b to force the actuation piston 110b to move toward the second cap 1 lOf. As the actuation piston 110b moves, the latch pin 110a and the latch piston 110c are forced toward the second cap 11 Of thereby compressing the spring HOd. Once the latch pin 110a is completely within the second rocker arm 108, the second rocker arm 108 is unlatched from the first rocker arm 106 such that movement from the first cam 128 causes motion of only to the first rocker arm 106 and the second rocker arm 108 pivots about the main rocker shaft. The motion of the second rocker arm 108 relative to the first rocker arm 106 causes the spring HOd to be compressed. This is referred to as a “lost motion” movement. During lost motion, i.e., when the latch pin 110a is in the unlatched position, the first rocker arm 106 does not pivot and no motion is transferred to the valves 116, 118.

[0034] Referring to FIG. 2, when the latch assembly 110 is in the latched position, the first rocker arm 106 is coupled to the second rocker arm 108 such that the first rocker arm 106 and the second rocker arm 108 move as a unitary body. In this position, a force applied to the first rocker arm 106, via the first cam 128, is transferred to the second rocker arm 108. In other words, the coupling of the first rocker arm 106 and the second rocker arm 108 results in movement of the valve end of the second rocker arm 108.

[0035] A first cam 128 may be positioned to engage the cam end 111 of the main rocker assembly 102, as shown in FIG. 2. The first cam 128 may be, for example, a rotatable body provided with a lift profile that converts rotational movement of the first cam 128 to displacement of the valves 116, 118. Referring to FIG. 4a, an exhaust lift 130 may be formed at a predetermined position on the first cam 128. The exhaust lift 130, when viewed with the first cam 128 as a profile, has a maximum height EX defined as a distance from the base circle of the first cam 128 to an apex 132 of the exhaust lift 130. As the first cam 128 rotates, theexhaust lift 130 applies motion to the cam end 111 of the first rocker arm 106 to induce rotation of the first rocker arm 106 about the rocker bore 113.

[0036] Referring to FIG. 3, when the latch assembly 110 is in the unlatched position the first rocker arm 106 is decoupled from the second rocker arm 108 such that the first rocker arm 106 and the second rocker arm 108 are free to move as independent bodies. In this position, a force applied to the first rocker arm 106, via the first cam 128, is not transferred to the second rocker arm 108. In other words, the decoupling of the first rocker arm 106 and the second rocker arm 108 results in lost motion when a force is applied to the first rocker arm 106.

[0037] When the latch assembly 110 is in the unlatched position, the rotation of the first rocker arm 106 caused by the exhaust lift 130 is not transferred to the second rocker arm 108. Because the motion is not transferred to the second rocker arm 108, the valve bridge 114 and the corresponding valves 116, 118 experience no motion.

[0038] Referring back to FIG. 1A, in the embodiment illustrated, the brake rocker assembly 104 of the rocker arm assembly 100 includes a single rocker arm that moves pivotally around a rocker bore 120. It is contemplated that the brake rocker assembly 104 may also be a multi-arm assembly, similar to the main rocker assembly 102.

[0039] The brake rocker assembly 104 has a cam end 121 and a valve end 123. Displacement of the cam end 121 about the rocker bore 120 causes the valve end 123 to be displaced. The brake rocker assembly 104 includes an engine brake capsule assembly (schematically shown in FIG. 1A) which includes an actuator 124 that is movable between a retracted position (FIG. 1 A) and an extended position (illustrated with broken lines in FIG. 1 A) in a slot 122. The actuator 124 may be extended a distance LM from the retracted position to the extended position. The distance LM represents a “lost motion” distance for the brake rocker assembly 104. When the actuator 124 is in the retracted position, rotation of the brake rocker assembly 104 applies no force at the valve end 123 until the valve end 123 has moved the distance LM plus a gap “g,” described below. In other words, during a lost motion of the brake rocker assembly 104, no force is applied by the actuator 124 to the brake valve 118 until the valve end 123 has moved more than the distance LM plus the gap “g ”

[0040] The valve bridge 114 includes a bridge pin 126. As shown in FIG. 1 A, when the actuator 124 is in the retracted position, the actuator 124 of the brake rocker assembly 104 is spaced from the bridge pin 126. Movement of the actuator 124 to the extended position moves the actuator 124 to a position wherein a gap “g” is formed between a distal end of the actuator 124 and the bridge pin 126. When the actuator 124 is actuated, the actuator 124 is brought intocontact with the bridge pin 126 when sufficient displacement is applied to the cam end 121 of the brake rocker assembly 104 by a second cam 134.

[0041] The second cam 134 may be positioned to engage the cam end 121 of the brake rocker assembly 104. The second cam 134 may be, for example a rotatable body similar to the first cam 128. A profile of the second cam 134 is shown in FIG. 4b. A compression release lift 136 may be formed as a displacement from a base circle of the second cam 134. The compression release lift 136, when viewed with the second cam 134 as a profile, has a maximum height CR defined as a distance from the base circle of the second cam 134 to an apex 138 of the compression release lift 136.

[0042] The second cam 134 also includes a recharge lift 140. The recharge lift 140 may be formed as a displacement from the base circle of the second cam 134. The recharge lift 140, when viewed with the second cam 134 as a profile, has a maximum height RCH defined as a distance from the base circle of the second cam 134 to an apex 142 of the recharge lift 140. The maximum height RCH of the recharge lift 140 is selected so that the brake rocker assembly 104 applies motion to the brake valve 118 regardless of the position of the actuator 124. In other words, the displacement of the valve end 123 of the brake rocker assembly 104 caused by the recharge lift 140 exceeds the distance LM that the actuator 124 moves into the slot 122 in the valve end 123 when the actuator 124 is in the retracted position.

[0043] In FIG. 1A, the main rocker assembly 102 and the brake rocker assembly 104 are illustrated as separate bodies with their respective cam ends 111, 121 disposed on opposite sides of the valve bridge 114. In this respect, they rotate around separate rocker shafts, i.e., the rocker bore 113 for the main rocker assembly 102 and the rocker bore 120 for the brake rocker assembly 104 may rotate around separate rocker shafts. It is contemplated that the main rocker assembly 102 and the brake rocker assembly 104 may be oriented so that their respective cam ends 111, 121 are on the same side of the valve bridge 114 such that the pivot around a common rocker shaft, i.e., the rocker bore 113 and the rocker bore 120 are axially aligned and rotate on the same rocker shaft.

[0044] Referring to FIGS. 2 and 5, a drive mode of the rocker arm assembly 100 is illustrated schematically (FIG. 2) and with reference to a valve lift profile (FIG. 5). When the latch assembly 110 is in the latched position, the rotation of the first rocker arm 106 by the exhaust lift 130 of the first cam 128 causes the second rocker arm 108 to pivot about the rocker bore 113. This motion is translated into movement of the valve bridge 114, and the corresponds valves 116, 118, by a distance DI.

[0045] During the drive mode of the rocker arm assembly 100, the actuator 124 of the brake rocker assembly 104 is in the retracted position. The first cam 128 and the second cam 134 are synchronized with the position of the piston, (i.e., timed with the piston being in bottom dead center (BDC) and top dead center (TDC)) so that the engine operates properly. In the drive mode, the actuator 124 is in the retracted position such that no motion from the second cam 134 is applied to the brake valve 118 regardless of the rotational position of the second cam 134. As illustrated in FIG. 5, only the exhaust lift 130 of the first cam 128 actuates the valve bridge 114 and the corresponding valves 116, 118. That is because, as illustrated, the actuator 124 is retracted such that the compression release lift 136 is not applied to the brake valve 118. The recharge lift 140 aligns with and is within the exhaust lift 130 so that only the higher of the exhaust lift 130 and the recharge lift 140, i.e., the exhaust lift 130, is applied to the main rocker assembly 102 and, subsequently, to the valve bridge 114 and the corresponding valves 116, 118.

[0046] Referring to FIG. 5, a valve lift profile DI corresponds to valve movement caused by the exhaust lift 130 of the first cam 128, a valve lift profile D2 corresponds to valve movement caused by the compression release lift 136 of the second cam 134 and a valve lift profile D3 corresponds to valve movement caused by the recharge lift 140 of the second cam 134. As the first cam 128 and the second cam 134 rotate synchronously with the movement of the piston 160, the exhaust lift 130 “hides” the recharge lift 140, causing the recharge lift 140 to not apply movement to the valves 116, 118.

[0047] Referring to FIGS. 6 and 7, a brake mode of the rocker arm assembly 100 is illustrated schematically (FIG. 6) and with reference to a valve lift profile (FIG. 7). During the brake mode, the latch assembly 110 of the main rocker assembly 102 is in the latched positioned, as discussed in the aforementioned drive mode. As illustrated in FIG. 6, the actuator 124 is extended from the slot 122 (i.e., a distance LM) and placed in engagement with the bridge pin 126 when the compression release lift 136 applies motion to the cam end 121 of the brake rocker assembly 104.

[0048] Referring to FIG. 7, the valve lift profile DI corresponds to the exhaust lift 130 of the first cam 128 and still “hides” the valve lift profile D3 (corresponding to the recharge lift 140 of the second cam 134). In other words, the valve lift profile DI aligns with the valve lift profile D3 and is at all instances greater than the valve lift profile D3 such that the valve lift profile D3 is not experienced by the valves 116, 118. However, the valve lift profile D2 corresponds to the compression release lift 136 of the second cam 134 and is applied to the brake valve 118 via the bridge pin 126.

[0049] Referring to FIGS. 8 and 9, a CD A mode of the rocker arm assembly 100 is illustrated schematically (FIG. 8) and with reference to a valve lift profile (FIG. 9). During the CDA mode, the latch assembly 110 of the main rocker assembly 102 is in the unlatched positioned such that the first rocker arm 106 is uncoupled from the second rocker arm 108. As such, motion from the first cam 128 is not applied to the valve bridge 114, i.e., the main rocker assembly 102 is in lost motion. As illustrated in FIG. 8, the actuator 124 is retracted into the slot 122. However, because the recharge lift 140 causes movement of the valve end 123 in excess of the distance LM that the actuator 124 is retracted, the second cam 134 applies motion to the brake valve 118. In particular, the displacement applied to the brake valve 118 is equal to the valve lift D3 caused by the recharge lift 140 of the second cam 134 minus the distance LM, i.e., D3-LM.

[0050] Referring to FIG. 9, the valve lift profile DI corresponds to the exhaust lift 130 of the first cam 128 and is not applied because the main rocker assembly 102 is in lost motion. The valve lift profile D2 corresponding to the compression release lift 136 of the second cam 134 is not applied because the actuator 124 is retracted and the maximum lift applied by the compression release lift 136 is less than the distance LM that the actuator 124 was retracted into the slot 122. The valve lift profile D3-LM corresponds to the recharge lift 140 of the second cam 134 minus the distance LM that that actuator 124 is retracted into the slot 122. Accordingly, on the valve lift profile D3-LM is experienced by the brake valve 118.

[0051] The rocker assembly according to the present disclosure thereby opens the brake valve 118 momentarily during the CDA mode to allow air to enter the piston chamber. Thus, during the CDA mode, the brake valve 118 periodically may open to allow an influx of gas into the combustion chamber.

[0052] FIG. 10 is a schematic of a combustion chamber 148 of a cylinder of a combustion engine in a cylinder deactivation (CDA) mode. The combustion chamber 148 may contain gas, which can be, for example, fuel, air a mixture thereof, and is defined by a piston 160 on its lower end. As shown, the exhaust opening 150 may be fluidly connected to an exhaust pipe 154 and the brake valve opening 152 may be fluidly connected to a brake valve pipe 156. The exhaust valve 116 and the brake valve 118 are configured to selectively open or close the exhaust opening 150 and the brake valve opening 152, respectively. Thus, as described in regard to FIGS. 1-8, the motion of the exhaust valve 116 can allow the release of gas from the cavity and the brake valve 118 can allow gas to be reintroduced into the cavitynecessarily drawn to scale, and other variations of the combustion chamber are contemplated having different alignments, shapes, number of valves, and the like.

[0053] The reintroduction of gas into the cavity 158 is shown by example in FIG. 11, which corresponds to the operation shown in FIGS. 8 and 9. In FIG. 11, the brake valve 118 is forced downward a small distance D3-LM. This movement causes the slight, periodic opening of the brake valve opening 152, allowing for a small amount of air to be introduced into the cavity 158.

[0054] FIGS. 5, 7 and 9 provide graphical illustrations for comparing the relative heights of the valve lift profiles for the various modes of operation of the rocker arm assembly 100. The x-axis of the graphs are time relative to the piston 160 being attop dead center position or bottom dead center position. The top dead center positions are labeled as TDC, and the bottom dead center positions are labeled as BDC. The valve lift profiles that are applied to the valves are shown in solid lines and the valve lift profiles that are not applied are shown in dashed lines. In the embodiments illustrated, the ratio of the cam lift profiles to the valve lift profiles is 1 : 1. It is contemplated that in actual application, the ratio may not be 1 :1.

[0055] While various features are presented above, it should be understood that the features may be used singly or in any combination thereof. Further, it should be understood that variations and modifications may occur to those skilled in the art to which the claimed examples pertain. While the illustrations provide exemplary embodiments, they are not necessarily drawn to scale and can include additional or alternative elements in suitable operation.

Claims

CLAIMSWhat is claimed is:

1. A valve train assembly for a combustion engine, the valve train assembly comprising: a rocker assembly for actuating a brake valve, the rocker assembly comprising: a rocker arm rotatable about a rocker shaft, and an actuator on a valve end of the rocker arm, the actuator movable between an extended position and a retracted position by a first predetermined distance; and a cam configured to engage a cam side of the rocker arm, the cam having a recharge lift profile dimensioned to move the valve end of the rocker arm according to valve lift profile that has a maximum height in excess of the first predetermined distance.

2. The valve train assembly of claim 1, further comprising: a second rocker assembly for actuating a valve bridge, the valve bridge configured to actuate the brake valve and an exhaust valve, the second rocker assembly comprising: a first rocker arm defining a cam end of the second rocker assembly; a second rocker arm defining a valve end of the second rocker assembly, the valve end configured to actuate the valve bridge wherein the first rocker arm and the second rocker arm are independently rotatable about a second rocker shaft; and a latch assembly movable between a latched position wherein the first rocker arm is coupled to the second rocker arm and an unlatched position wherein the first rocker arm is uncoupled from the second rocker arm; and a second cam configured to engage the cam end of the second rocker assembly, the second cam having an exhaust lift profile for actuating the brake valve and the exhaust valve via the valve bridge at predetermined intervals,wherein the recharge lift profile aligns with the predetermined intervals of the exhaust lift profile.

3. The valve train assembly of claim 2, wherein the valve bridge includes a bridge pin that is movable relative to a body of the valve bridge, the bridge pin positioned to engage the brake valve to allow the brake valve to move independent of the valve bridge.

4. The valve train assembly of claim 3, wherein when the actuator is in the extended position, a gap is formed between a distal end of the actuator and the bridge pin.

5. The valve train assembly of claim 2, the cam further comprising a compression lift profile for actuating the brake valve according to a second valve lift profile, wherein the compression lift profile is spaced from the recharge lift profile.

6. The valve train assembly of claim 5, wherein the second valve lift profile has a maximum height less than the first predetermined distance.

7. The valve train assembly of claim 2, wherein the exhaust lift profile is configured to acuate the brake valve and the exhaust valve according to a third valve lift profile that aligns with the valve lift profile and that is at all instances greater than the valve lift profile.

8. The valve train assembly of claim 2, wherein the brake valve and the exhaust valve are configured to open and close exhaust openings in a combustion chamber.

9. The valve train assembly of claim 2, wherein the valve end of the second rocker assembly includes an elephant foot configured to engage the valve bridge.

10. A method for operating an exhaust valve and a brake valve of a combustion engine, the brake valve and the exhaust valve both actuated by a valve bridge and the brake valve movable relative to the valve bridge, the method comprising:during a cylinder deactivation mode wherein the valve bridge is not actuated, periodically allowing air to enter a cylinder of the combustion engine by periodically actuating the brake valve.

11. The method of claim 10, comprising a rocker assembly having a first rocker arm and a second rocker arm that selectively coupled together via a latch assembly and a second rocker assembly having an actuator for selectively actuating the brake valve, wherein: during a drive mode the first rocker arm and the second rocker arm are coupled together to actuate the valve bridge and the actuator is in a retracted position wherein the brake valve is not actuated by second rocker assembly.

12. The method of claim 11, wherein: during a brake mode the first rocker arm and the second rocker arm are coupled together to actuate the valve bridge and the actuator is in an extended position wherein the brake valve is actuated by second rocker assembly.

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