Patent Application
20240209758
The present disclosure relates generally to rocker arm assemblies for use in a valve train assembly and, more particularly, to a lost motion spigot assembly for an exhaust rocker arm.
Compression engine brakes can be used as auxiliary brakes in addition to wheel brakes, for example, on relatively large vehicles powered by heavy or medium duty diesel engines. A compression engine braking system is arranged, when activated, to provide an additional opening of an engine cylinder's exhaust valve when the piston in that cylinder is near a top-dead-center position of its compression stroke so that compressed air can be released through the exhaust valve. This causes the engine to function as a power consuming air compressor which slows the vehicle.
In a typical valve train assembly used with a compression engine brake, the exhaust valve is actuated by a rocker arm which engages the exhaust valve by means of a valve bridge. The rocker arm rocks in response to a cam on a rotating cam shaft 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 gap that develops 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.
In one aspect of the present disclosure, a combined exhaust and engine brake rocker arm assembly configured to selectively open first and second exhaust valves is provided. The assembly includes a rocker arm body, an exhaust rocker arm assembly formed in the rocker arm body, and a lost motion spigot assembly operably coupled to the exhaust rocker arm and including an adjustment nut and guide configured to receive a shaft assembly for adjusting a lash of the lost motion spigot assembly. The shaft assembly is disposed within a bore of the adjustment nut below an upper surface thereof, and an engine brake rocker arm assembly is formed in the rocker arm body and configured to operate in a collapse mode and a rigid mode. The lost motion spigot assembly is configured to selectively engage a valve bridge to open the first and second exhaust valves, and the engine brake rocker arm assembly is configured to selectively engage the valve bridge to open only the first exhaust valve.
In addition to the foregoing, the described rocker arm assembly may include one or more of the following features: wherein the adjustment nut has a T-shaped cross-section; wherein an upper flange portion of the T-shaped cross-section is not threaded; wherein the shaft assembly includes an upper shaft and a lower shaft extending through the guide, wherein the upper shaft is threaded to an internal bore of the adjustment nut; wherein the guide includes a first step configured to interface with the adjustment nut; and wherein the guide includes a second step configured as a seat for a biasing mechanism.
In addition to the foregoing, the described rocker arm assembly may include one or more of the following features: a cap coupled to the exhaust rocker arm and configured as a second seat for the biasing mechanism; wherein a bore formed in the rocker arm body defines a shoulder configured to provide at least a portion of the biasing mechanism seat along with the second step; and wherein the guide includes a third step configured to engage a stop surface formed on the rocker body; and wherein the second step is set radially inward of the third step, and the first step is set radially inward of the second step.
In addition to the foregoing, the described rocker arm 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 valve bridge, and in the extended position the engine brake capsule selectively engages the valve bridge to open the first exhaust valve; wherein the engine brake capsule includes 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 within an upper chamber of the outer housing; and wherein the engine brake capsule includes a check ball assembly disposed within the lower chamber, the pin assembly operatively associated with the check ball assembly to selectively enable a hydraulic fluid into the lower chamber to move the plunger from the retracted position to the extended position.
In another aspect of the present disclosure, a valvetrain assembly is provided. The valvetrain assembly includes a first engine valve, a second engine valve, a valve bridge operatively associated with the first and second engine valves, and a combined exhaust and engine brake rocker arm assembly configured to selectively open first and second exhaust valves. The rocker arm assembly includes a rocker arm body, an exhaust rocker arm assembly formed in the rocker arm body, and a lost motion spigot assembly operably coupled to the exhaust rocker arm and including an adjustment nut and guide configured to receive a shaft assembly for adjusting a lash of the lost motion spigot assembly. The shaft assembly is disposed within a bore of the adjustment nut below an upper surface thereof, and an engine brake rocker arm assembly is formed in the rocker arm body and configured to operate in a collapse mode and a rigid mode. The lost motion spigot assembly is configured to selectively engage a valve bridge to open the first and second exhaust valves, and the engine brake rocker arm assembly is configured to selectively engage the valve bridge to open only the first exhaust valve.
In addition to the foregoing, the described valvetrain assembly may include one or more of the following features: wherein the adjustment nut has a T-shaped cross-section; wherein an internal bore of the T-shaped adjustment nut is threaded except for an upper flange portion of the T-shaped cross-section is not threaded, wherein the shaft assembly includes an upper shaft and a lower shaft extending through the guide, wherein the upper shaft is threaded to the threaded internal bore of the adjustment nut; wherein the guide includes a first step configured to interface with the adjustment nut, a second step configured as a seat for a biasing mechanism, and a third step configured to engage a stop surface formed on the rocker body; a cap coupled to the exhaust rocker arm and configured as a second seat for the biasing mechanism, and wherein a bore formed in the rocker arm body defines a shoulder configured to provide at least a portion of the biasing mechanism seat along with the second step; and wherein the second step is set radially inward of the third step, and the first step is set radially inward of the second step.
The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:
With initial reference to
Specifically, each cylinder includes an intake valve rocker arm assembly 14, an exhaust rocker arm assembly 16, and an engine brake rocker arm assembly 18. However, as illustrated, the exhaust valve rocker arm assembly 16 and the engine brake rocker arm assembly 18 are combined into a single rocker arm and are collectively referred to as a combined exhaust and engine brake rocker arm assembly 20, which cooperates to control opening of the exhaust valves. The intake valve rocker arm assembly 14 is configured to control motion of the intake valves, the exhaust valve rocker arm assembly 16 is configured to control exhaust valve motion in a drive mode, and the engine brake rocker arm assembly 18 is configured to act on one of the two exhaust valves in an engine brake mode, as will be described herein.
A rocker shaft 22 is received by the valve train carrier 12 and supports rotation of the combined exhaust and engine brake rocker arm assembly 20. As described herein in more detail, the rocker shaft 22 can communicate oil to the assemblies 16, 18 during operation. A cam shaft 24 includes lift profiles or cam lobes configured to rotate assemblies 16, 18 to activate first and second exhaust valves 26 and 28, as is described herein in more detail. For example,
With reference now to
The exhaust valve rocker arm assembly 16 can include exhaust rocker arm portion 46, which defines a bore 54 configured to at least partially receive a lost motion spigot assembly 56. When roller 44 is engaged by the exhaust lift profile 30, the exhaust rocker arm portion 46 and lost motion spigot assembly 56 can be rotated downward, causing downward movement of the valve bridge assembly 52, which engages the first and second exhaust valve 26 and 28 (
With particular reference to
As shown in the illustrated example, bore 54 defines a shoulder 76, and the guide 62 defines a first step 78, a second step 80, and a third step 82. The first step 78 is configured to interface with the adjustment nut 70. The second step 80, along with the bore shoulder 76, are configured to provide a first seat 84 for one end of the biasing mechanism 64. The third step 82 is configured to selectively engage a stop surface 86 defined on a bottom of the rocker arm body 40 to limit upward motion of the guide 62.
In the example embodiment, the cap 68 is coupled to an upper surface of the rocker arm body 40 and defines an aperture 88 configured to receive adjustment nut 70 therethrough. In this way, the cap 68 is configured to provide a second seat 90 for an opposite end of the biasing mechanism 64, which is configured to bias the guide downward toward the valve bridge assembly 52 and absorb motion during the engine brake mode. The adjustment nut 70 has a generally T-shaped cross-section with the smaller diameter portion extending into the cap 68 and bore 54 radially inward of the lost motion biasing mechanism 64. Both the adjustment nut 70 and the guide 62 define an internal bore 92 configured to receive shaft assembly 60. In the example embodiment, at least a portion of the internal bore 92 is threaded to an outer diameter surface of the upper shaft 72, which includes a tool cavity 94 (e.g., a hex-cavity) configured to receive a tool (not shown) for rotating the upper shaft 72. Notably, in the example embodiment, an upper flange portion 96 of the T-shaped nut 70 is not threaded with the upper shaft 72 to reduce or prevent torque load impact.
Rotation of the upper shaft 72 is configured to move/constrain the lower shaft 74 for setting the desired lash of the lost motion spigot assembly 56. In this way, the e-foot 66 is coupled to or operably associated with the lower shaft 74, and the adjustment nut 70 is threadably secured to the upper shaft 72. Utilizing the tool, the upper shaft 72 can be rotated downward until there is no lash at a gage block (not shown) temporarily placed between the third step 82 and the stop surface 86. In this way, the valve lash set at a predetermined contact point (e.g., central contact point) of the bridge assembly 52 may be adjusted by way of shaft assembly 60 and adjustment nut 70 to provide a desired lost motion stroke (LMS).
Accordingly, the spigot assembly 56 provides numerous advantages, including lost motion capability with a reduced height and simplified adjustment maintenance compared to known systems. Additionally, the upper shaft 72 at the tool cavity 94 is unthreaded to facilitate preventing torque load impact, while the tool cavity 94 is concealed within the adjustment nut 70 below a top surface 98 thereof to provide increased clearance gap between the spigot assembly 56 and the engine cover (not shown). Adjustment nut flange 96 facilitates integrating the shaft assembly 60 into the rocker arm assembly 20. Moreover, a length of adjustment nut 70 is variable based on design since the interface area between the adjustment nut 70 and guide 62 (i.e., the first step 78) does not contact the biasing mechanism 64. The bore shoulder 76 at least partially defines the first seat 84 for one end of the biasing mechanism 64 to facilitate setting the desired lash.
Advantageously, the length of guide 62 is disposed toward a bottom of the spigot assembly 56, thereby allowing the guide top portion to be shorter due to bias torque load reduction compared to conventional systems. Wear is also reduced because of torque load improvement and stiffness enhancement. As shown in FIG. 4, load stress at corner 100 is reduced since the bending arm ‘R’ is shortened compared to conventional systems. Such a system also enables the diameter of lower shaft 74 to be larger, for example to increase stiffness and ability to bear more bending load, since guide 62 can have a larger diameter.
With continued reference to
In the example embodiment, brake capsule assembly 112 is configured to selectively move from a collapsing mode to a rigid mode to selectively transfer cam motion to the valve 26 during an engine braking event. As shown in
A check ball assembly 132 can be disposed in the lower chamber 120. The check ball assembly 132 can be configured to hold oil within a space or area 134 between the plunger 116 and the intermediate chamber 122. A pin assembly 136 is disposed in the upper chamber 124 and includes a main body 138 and a pin arm 140. The main body 138 defines a seat 142 configured to receive a biasing mechanism 144 (e.g., a spring), and pin arm 140 extends downwardly from the main body into the intermediate chamber 122. The biasing mechanism 144 is configured to rest against the cap 118 and bias the pin assembly 136 downward into contact with the check ball assembly 132.
Oil can be supplied to the intermediate chamber 122 via, for example, the rocker shaft 22 and through ports 146. The upward pressure of the fluid supply compresses the biasing mechanism 144 such that pin assembly 136 is moved away from the check ball assembly 132. This movement allows the oil in intermediate chamber 122 to fill area 134 and move plunger 116 downward and outward into an extended position to engage the valve pin 130 (e.g., a brake mode). When the supply of oil ceases, the oil in intermediate chamber 122 can be at least partially evacuated and plunger 116 is able to slide upward into lower chamber 120 when the plunger 116 comes into contact with the valve pin 130 (e.g., drive mode).
Thus, the engine brake capsule assembly 112 can be selectively operated between the brake mode and the drive mode. In the brake mode, pressurized oil is selectively supplied to ports 146 to move the plunger downward into the extended position. In the drive mode, the oil supply to ports 146 is suspended, and the plunger 116 returns to the retracted position within the lower chamber 120 of outer housing 114.
As such, during operation of rocker arm assembly 20, the exhaust rocker arm assembly 16 can selectively engage the valve bridge main body 52 to actuate valves 26, 28 and perform a normal exhaust event (combustion mode); whereas, the engine brake rocker arm assembly 18 can selectively engage the valve pin 130 to only actuate valve 26 and perform a brake event actuation (engine braking mode).
As previously noted, the engine brake capsule assembly 112 is configured to move the plunger 116 between the retracted position and the extended position. In the retracted position, the plunger 116 is withdrawn into the outer housing lower chamber 120 such that the plunger 116 is spaced apart from and does not contact the valve pin 130 even when the cam lobe (e.g., lobe 32) of camshaft 24 engages the combined rocker arm assembly 20.
However, in the extended position, the plunger 116 extends from the outer housing lower chamber 120 such that plunger 116 is positioned to engage the valve pin 130. When the cam lobe engages the combined rocker arm assembly 20, plunger 116 engages valve pin 130 to open valve 26 and perform the brake event actuation.
Turning now to
With continued reference to
As the exhaust cam lift profile 30 rotates rocker arm body 40 even farther to where spigot assembly 56 no longer absorbs rocker arm motion (e.g.,
In braking mode, operation begins when the base circle of the cam lift profile engages the combined rocker arm assembly 20, represented as point 220 (
At point 224 (
Described herein are systems and methods for a single rocker arm assembly configured to selectively perform exhaust and engine braking events on an engine. The system includes a single rocker arm having an exhaust rocker arm assembly and an engine brake rocker arm assembly. The exhaust rocker arm assembly selectively engages a valve bridge to actuate two valves to perform an exhaust event. The engine brake rocker arm assembly includes a brake capsule assembly configured to selectively transfer motion to a portion of the valve bridge to thereby actuate one of the two valves and perform an engine brake event.
In one aspect, the exhaust rocker arm includes a lost motion spigot assembly that provides a top spring location and adjustment nut for a type III or type V valve train system. The adjustment nut is T-shaped with a portion extending into the rocker arm to reduce assembly height. Additionally, a three-step hollow guide enables the top spring location and obviates the need for a spring seat collar, while improving bias torque and reducing wear.
As used herein, the term controller refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.
The foregoing description of the examples has been provided 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. The same 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.
This application claims the benefit of U.S. Prov. App. No. 63/179,667, filed Apr. 26, 2021, the contents of which are incorporated herein by reference thereto.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/025186 | 4/26/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63179667 | Apr 2021 | US | |
| 63269201 | Mar 2022 | US |
