Engine brake rocker arm with offset configuration
阅读说明:本技术 具有偏置构型的引擎制动摇臂 (Engine brake rocker arm with offset configuration ) 是由 马克·范文杰登 马修·文斯 于 2018-12-04 设计创作,主要内容包括:本发明提供了一种摇臂组件,该摇臂组件能够在第一模式和第二模式下操作,该摇臂组件基于具有第一凸轮凸角和第二凸轮凸角的凸轮轴的旋转来选择性地打开第一引擎阀和第二引擎阀。该摇臂组件包括摇杆轴、第一摇臂组件和第二摇臂组件以及偏置组件。第二摇臂组件具有第二摇臂,该第二摇臂接纳摇杆轴并且被构造成基于与第二凸轮凸角的选择性接合在第二模式下围绕摇杆轴旋转,并且选择性地作用于第一引擎阀和第二引擎阀中的一者。偏置组件与第二摇臂配合以将第二摇臂偏置到空档位置。在空档位置中,第二摇臂相对于第二凸轮凸角和第二引擎阀两者间隔开而不接触。(A rocker arm assembly is operable in a first mode and a second mode that selectively opens a first engine valve and a second engine valve based on rotation of a camshaft having a first cam lobe and a second cam lobe. The rocker arm assembly includes a rocker shaft, first and second rocker arm assemblies, and an offset assembly. The second rocker arm assembly has a second rocker arm that receives the rocker shaft and is configured to rotate about the rocker shaft in a second mode based on selective engagement with the second cam lobe and selectively act on one of the first and second engine valves. A biasing assembly cooperates with the second rocker arm to bias the second rocker arm into a neutral position. In the neutral position, the second rocker arm is spaced apart from contact with both the second cam lobe and the second engine valve.)
1. A rocker arm assembly operable in a first mode and a second mode, the rocker arm assembly selectively opening a first engine valve and a second engine valve based on rotation of a camshaft having a first cam lobe and a second cam lobe, the rocker arm assembly comprising:
a rocker shaft;
a first rocker arm assembly having a first rocker arm receiving the rocker shaft and configured to rotate about the rocker shaft in the first mode based on engagement with the first cam lobe;
a second rocker arm assembly having a second rocker arm receiving the rocker shaft and configured to rotate about the rocker shaft in the second mode based on selective engagement with the second cam lobe and selectively acting on one of the first and second engine valves; and
a biasing assembly cooperating with the second rocker arm to bias the second rocker arm into a neutral position, wherein in the neutral position the second rocker arm is spaced apart from contact with respect to both the second cam lobe and the second engine valve.
2. The rocker arm assembly of claim 1 wherein the biasing assembly further comprises a spring plate assembly comprising:
a first spring plate fixed relative to the rocker shaft;
a second spring plate fixed for rotation with the second rocker arm; and
at least one biasing member disposed relative to the first and second spring plates and configured to load and unload based on rotation of the second rocker arm about the rocker shaft.
3. The rocker arm assembly of claim 2 wherein the spring plate assembly defines at least one window configured to receive the at least one biasing member.
4. The rocker arm assembly of claim 3, wherein at least one window is defined in part by a first bearing surface on the first spring plate and a second bearing surface on the second spring plate, wherein the at least one biasing member bears against the respective first and second bearing surfaces during rotation of the second rocker arm about the rocker shaft.
5. The rocker arm assembly of claim 3 wherein the spring plate assembly includes at least one spring retainer configured to retain the at least one biasing member within the at least one window.
6. The rocker arm assembly of claim 2, wherein the first plate defines at least one slot and the second plate defines at least one hole, wherein a fastener extends through the at least one slot and the at least one hole and is threadably secured into a threaded hole defined in the second rocker arm, wherein the second spring plate rotates relative to the first spring plate as the fastener travels along the at least one slot during rotation of the second rocker arm during operation in the second mode.
7. The rocker arm assembly of claim 2, wherein the second rocker arm includes a bladder configured to move between a retracted position and an extended position, wherein in the retracted position, the biasing assembly biases the second rocker arm to the neutral position.
8. The rocker arm assembly of claim 7 wherein in the extended position, the second rocker arm is rotated toward the second cam lobe preloading the biasing assembly.
9. The rocker arm assembly of claim 2, further comprising an orientation system having a key extending from the camshaft, a keyway defined on the first plate, and a pair of opposing stops defining a rotation limiting slot on the second plate, wherein the key is fixed to the first plate at the keyway and rotation of the second rocker arm is limited by engagement of the key with the opposing stops on the second plate.
10. The rocker arm assembly of claim 1 wherein the first rocker arm assembly is an exhaust valve rocker arm assembly and the second rocker arm assembly is an engine brake rocker arm assembly.
11. The rocker arm assembly of claim 10 wherein the exhaust valve rocker arm assembly comprises an exhaust rocker arm and a valve bridge having a lever pivotally coupled thereto such that during operation in the second mode, the engine brake rocker arm does not transfer motion to the valve bridge.
12. The rocker arm assembly of claim 1 wherein the first and second engine valves are exhaust valves and one of the first and second modes includes Early Exhaust Valve Opening (EEVO).
13. The rocker arm assembly of claim 1 wherein the first and second engine valves are intake valves, and wherein one of the first and second modes comprises Late Intake Valve Closing (LIVC).
14. A rocker arm assembly operable in a first mode and a second mode, the rocker arm assembly selectively opening a first engine valve and a second engine valve based on rotation of a camshaft having a first cam lobe and a second cam lobe, the rocker arm assembly comprising:
a rocker shaft;
a first exhaust rocker arm configured to rotate about the rocker shaft based on engagement with the first cam lobe in the first mode;
a second engine brake rocker arm configured to rotate about the rocker shaft and selectively act on one of the first and second engine valves based on selective engagement with the second cam lobe in the second mode;
a bladder disposed on the second engine brake rocker arm and configured to move between an extended position and a retracted position; and
a spring plate assembly cooperating with the second rocker arm to bias the second rocker arm to a neutral position when the balloon is in the retracted position, wherein in the neutral position the second rocker arm is spaced apart from contact with respect to both the second cam lobe and the second engine valve, the spring plate assembly comprising:
a first spring plate fixed relative to the rocker shaft;
a second spring plate fixed for rotation with the second rocker arm; and
at least one biasing member that selectively biases against the first and second spring plates as the second rocker arm rotates.
15. The rocker arm assembly of claim 14 wherein the spring plate assembly defines at least one window configured to receive the at least one biasing member.
16. The rocker arm assembly of claim 15, wherein at least one window is defined in part by a first bearing surface on the first spring plate and a second bearing surface on the second spring plate, wherein the at least one biasing member bears against the respective first and second bearing surfaces during rotation of the second rocker arm about the rocker shaft.
17. The rocker arm assembly of claim 16 wherein the spring plate assembly includes at least one spring retainer configured to retain the at least one biasing member within the at least one window.
18. The rocker arm assembly of claim 14, wherein the first plate defines at least one slot and the second plate defines at least one hole, wherein a fastener extends through the at least one slot and the at least one hole and is threadably secured into a threaded hole defined in the second rocker arm, wherein the second spring plate rotates relative to the first spring plate as the fastener travels along the at least one slot during rotation of the second rocker arm during operation in the second mode.
19. The rocker arm assembly of claim 14 wherein in the extended position, the second rocker arm is rotated toward the second cam lobe preloading the biasing assembly.
20. The rocker arm assembly of claim 14, further comprising an orientation system having a key extending from the camshaft, a keyway defined on the first plate, and a pair of opposing stops defining a rotation limiting slot on the second plate, wherein the key is fixed to the first plate at the keyway and rotation of the second rocker arm is limited by engagement of the key with the opposing stops on the second plate.
Technical Field
The present disclosure relates generally to rocker arm assemblies for use in valve train assemblies, and more particularly to rocker arm assemblies incorporating dedicated rocker arms acting on a single valve and incorporating biasing assemblies that bias the rocker arm into a neutral position.
Background
In addition to wheel brakes, compression engine brakes may be used as auxiliary brakes on relatively large vehicles, such as trucks, driven by heavy or medium duty diesel engines. The compression engine brake system is arranged to provide additional opening of an exhaust valve of an engine cylinder when a piston in the cylinder is near a top dead center position of its compression stroke when activated, such that compressed air may be released through the exhaust valve. This results in the engine acting as a power consuming air compressor, which slows the vehicle.
In a typical 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 a cam on the rotating 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 clearance created between the components in the valve train assembly.
The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Disclosure of Invention
A rocker arm assembly is operable in a first mode and a second mode that selectively opens a first engine valve and a second engine valve based on rotation of a camshaft having a first cam lobe and a second cam lobe. The rocker arm assembly includes a rocker shaft, first and second rocker arm assemblies, and an offset assembly. The first rocker arm assembly has a first rocker arm that receives the rocker shaft and is configured to rotate about the rocker shaft in a first mode based on engagement with the first cam lobe. The second rocker arm assembly has a second rocker arm receiving the rocker shaft and configured to rotate about the rocker shaft in the second mode based on selective engagement with the second cam lobe and selectively acting on one of the first and second engine valves. A biasing assembly cooperates with the second rocker arm to bias the second rocker arm into a neutral position. In the neutral position, the second rocker arm is spaced apart from contact with both the second cam lobe and the second engine valve.
According to other features, the biasing assembly further includes a spring plate assembly having a first spring plate, a second spring plate, and at least one biasing member. The first spring plate is fixed relative to the rocker shaft. The second spring plate is fixed for rotation with the second rocker arm. At least one biasing member is disposed relative to the first and second spring plates and is configured to load and unload based on rotation of the second rocker arm about the rocker shaft. The spring plate assembly may define at least one window configured to receive at least one biasing member. At least one window is defined in part by a first bearing surface on the first spring plate and a second bearing surface on the second spring plate. During rotation of the second rocker arm about the rocker axis, the at least one biasing member bears against the respective first and second bearing surfaces.
In other features, the spring plate assembly includes at least one spring retainer configured to retain the at least one biasing member within the at least one window. The first plate may define at least one slot. The second plate may define at least one aperture. A fastener extends through the at least one slot and the at least one hole and is threadably secured to a threaded hole defined in the second rocker arm. The second spring plate rotates relative to the first spring plate as the fastener travels along the at least one slot during rotation of the second rocker arm during operation in the second mode.
According to an additional feature, the second rocker arm includes a bladder configured to move between a retracted position and an extended position. In the retracted position, the biasing assembly biases the second rocker arm to a neutral position. In the extended position, the second rocker arm is rotated toward the second cam lobe, preloading the biasing assembly.
In additional features, the orientation system may include a key extending from the camshaft. The keyway may be defined on the first plate. A pair of opposing stops may define a rotation limiting slot on the second plate. The key is secured to the first plate at the keyway. Rotation of the second rocker arm is limited by engagement of the key with an opposing stop on the second plate.
In one arrangement, the first rocker arm assembly is an exhaust valve rocker arm assembly and the second rocker arm assembly is an engine brake rocker arm assembly. The exhaust valve rocker arm assembly includes an exhaust rocker arm and a valve bridge. The valve bridge has a lever pivotally coupled thereto such that during operation in the second mode, the engine brake rocker arm does not transfer motion to the valve bridge. In one configuration, the first and second engine valves are exhaust valves, and one of the first and second modes includes Early Exhaust Valve Opening (EEVO). In another configuration, the first and second engine valves are intake valves, and wherein one of the first and second modes includes Late Intake Valve Closing (LIVC).
A rocker arm assembly is operable in a first mode and a second mode that selectively opens a first engine valve and a second engine valve based on rotation of a camshaft having a first cam lobe and a second cam lobe. The rocker arm assembly includes a rocker shaft, first and second rocker arms, a bladder, and a spring plate assembly. The first rocker arm is configured to rotate about a rocker shaft in a first mode based on engagement with the first cam lobe. The second rocker arm is configured to rotate about the rocker shaft in a second mode based on selective engagement with the second cam lobe and selectively act on one of the first engine valve and the second engine valve. The bladder is disposed on the second engine brake rocker arm and is configured to move between an extended position and a retracted position. A spring plate assembly cooperates with the second rocker arm to bias the second rocker arm into the neutral position when the bladder is in the retracted position. In the neutral position, the second rocker arm is spaced apart from contact with both the second cam lobe and the second engine valve. The spring plate assembly includes a first spring plate, a second spring plate, and at least one biasing member. The first spring plate is fixed relative to the rocker shaft. The second spring plate is fixed for rotation with the second rocker arm. At least one biasing member selectively biases against the first and second spring plates as the second rocker arm rotates.
The spring plate assembly may define at least one window configured to receive at least one biasing member. At least one window is defined in part by a first bearing surface on the first spring plate and a second bearing surface on the second spring plate. During rotation of the second rocker arm about the rocker axis, the at least one biasing member bears against the respective first and second bearing surfaces.
In other features, the spring plate assembly includes at least one spring retainer configured to retain the at least one biasing member within the at least one window. The first plate may define at least one slot. The second plate may define at least one aperture. A fastener extends through the at least one slot and the at least one hole and is threadably secured to a threaded hole defined in the second rocker arm. The second spring plate rotates relative to the first spring plate as the fastener travels along the at least one slot during rotation of the second rocker arm during operation in the second mode.
In additional features, in the extended position, the second rocker arm is rotated toward the second cam lobe, preloading the biasing assembly. The orientation system may include a key extending from the camshaft. A keyway may be defined on the first plate. A pair of opposing stops may define a rotation limiting slot on the second plate. The key is secured to the first plate at the keyway. Rotation of the second rocker arm is limited by engagement of the key with an opposing stop on the second plate.
Drawings
The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:
FIG. 1 is a first perspective view of a partial valve train assembly incorporating a rocker arm assembly including an intake rocker arm, an exhaust rocker arm, and an engine brake rocker arm having an offset assembly constructed in accordance with one example of the present disclosure;
FIG. 2 is a second perspective view of the partial valvetrain assembly of FIG. 1, and shown with the intake rocker arms and associated intake valves removed for illustrative purposes;
FIG. 3 is a first perspective view of an engine brake rocker arm and associated biasing assembly;
FIG. 4 is a second perspective view of the engine brake rocker arm and associated biasing assembly of FIG. 3;
FIG. 5 is an exploded perspective view of the engine brake rocker arm and associated biasing assembly of FIG. 4;
FIG. 6 is a front view of the engine braking rocker arm and biasing assembly of FIG. 3, and is shown in a neutral position;
FIG. 7 is a front view of the engine braking rocker arm and biasing assembly of FIG. 3, and is shown during an engine braking event, wherein the biasing member of the biasing assembly is loaded as the rocker arm rotates toward engagement with the engine braking cam lobe; and is
Fig. 8 is a front view of the engine braking rocker arm and biasing assembly of fig. 7, and is shown with the valve undergoing a valve lift event, and with the biasing member unloaded as the rocker arm rotates clockwise from the position shown in fig. 7 to the position shown in fig. 8.
Detailed Description
The following discussion is in the context of a rocker arm for opening an exhaust valve configured in a compression engine braking system. The discussion focuses on a camshaft having a main lift cam and an engine brake lift cam. It should be understood that the present disclosure is not limited thereto. For example, the present disclosure may additionally or alternatively be applicable to exhaust valves in other non-compression braking systems. Furthermore, the present disclosure may also be applicable to intake valves. In this regard, the camshaft may be configured with primary and secondary lift cams. For example, the present disclosure may also be applicable to valve trains configured for Early Exhaust Valve Opening (EEVO), Late Intake Valve Closing (LIVC), or other Variable Valve Actuation (VVA) configurations.
Heavy Duty (HD) diesel engines with single overhead cam (SOHC) valves require high braking power, especially at low engine speeds. The present disclosure provides an accelerating sports type decompression engine brake. In order to provide high braking power without imposing high loads on the rest of the valve train, in particular the camshaft, the present disclosure provides an engine brake dedicated rocker arm acting on one exhaust valve. In this regard, there is half the input load as compared to other configurations with two exhaust valve openings.
Referring initially to FIG. 1, a partial valve train assembly constructed in accordance with one example of the present disclosure is illustrated and generally identified by
Specifically, each cylinder includes an intake valve
With continuing reference to fig. 1 and with additional reference to fig. 2, the exhaust valve
The
Referring now additionally to fig. 3-5, the engine
The engine brake
In the exemplary embodiment, biasing
The
Referring to fig. 6-8, the
The key 422 can be coupled to the
The
As described above, the
The neutral position, as described herein, is intended to represent a first non-contact volume 450 (fig. 6) between the engine
During operation, the biasing
The foregoing description of these examples has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular example are generally not limited to that particular example, but, where applicable, are interchangeable and can be used in a selected example, even if not specifically shown or described. Which can also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
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