Rocker arm assembly

Details Rocker arm assembly Rocker arm assembly

2000-12-06

2001-11-13

Lo, Wellun (Department: 3748)

Internal-combustion engines

Poppet valve operating mechanism

With means for varying timing

C123S090410, C123S19800E, C074S559000

Reexamination Certificate

active

06314928

ABSTRACT:

FIELD OF THE INVENTION
The field of the present invention is that of rocker arm assemblies for internal combustion engines. More particularly, the field of the present invention is that of rocker arm assemblies for internal combustion engines which can be selectively deactivated to totally or partially deactivate a combustion chamber valve of an internal combustion engine.
BACKGROUND OF THE INVENTION
Rocker arms transmit motion from a rotating cam shaft to a stem of a poppet valve to open and close the valve. Almost universally, the valve is spring-biased shut and the cam via the rocker arm controls the opening and closing of the valve. One type of rocker arm is the finger follower rocker arm.
In recent times, rocker arms have been made to selectively deactivate to allow enhanced control of vehicle engines in regard to emissions and fuel economy. In one such rocker arm assembly, the rocker arm
23
(
FIG. 9
) has an outer body
25
that engages the valve stem (not shown) and an inner lost motion arm
27
pivotally mounted on and within the outer body for movement relative to the outer body. The lost motion arm
27
is spring-biased upward against an overhead engine cam lobe (not shown) to be pivoted by the same. A latching mechanism with an extendable plunger
29
is positioned within the outer body
25
. The plunger
29
is normally in a position to limit movement of the lost motion arm
27
relative to the outer body
25
so that the cam lobe can pivot the outer body
25
and lost motion arm
27
together as an integral unit to activate the valve stem. Withdrawal of the latch mechanism plunger
29
allows the lost motion arm
27
to freewheel in a lost motion manner without causing any partial or full movement of the outer body
25
and valve stem.
Currently, such selectively deactivation rocker arm assemblies are valve lift limited due to a condition termed “super submarining” (hereinafter referred to as submarining) wherein the rocker arm assembly is permanently locked in a valve deactivated condition. Submarining occurs when the lost motion arm is inadvertently held underneath an extended plunger
29
. Submarining causes the cylinder serviced by the submarining rocker arm
23
to be permanently disabled. When the submarining occurs, major disassembly of the vehicle engine is required to alleviate the situation. Prior to the present invention, the valve lift and engine speed have been compromised by limiting them to such levels so as to prevent the lost motion control arm
27
from passing below the plunger
29
. It is desirable to provide a rocker arm assembly which is self-alleviating from any potential submarining conditions.
SUMMARY OF THE INVENTION
To make manifest the above delineated desire, the revelation of the present invention is brought forth. The rocker assembly of the present invention provides for selective deactivation of a valve while providing a freedom of engine design to maximize valve lift and engine speed. In a preferred embodiment, the rocker arm assembly of the present invention provides a longitudinal extending body. The body is engagable adjacent a first end with an engine valve stem to activate the same. Opposite the first end, the body is engagable with a pivot fulcrum. A lost motion arm is provided. The lost motion arm is pivotally connected to the first end of the body. The lost motion arm is spring biased by torsion springs into engagement with a rotatable cam lobe of the engine. The lost motion arm has first and second contact surfaces. A latch mechanism is connected on an end of the body generally opposite the pivotal connection of the lost motion arm with the body. The latch mechanism includes an extendable plunger with first and second contact surfaces. The plunger has a first position for first contact surface engagement with the lost motion arm first contact surface to prevent angular movement of the lost motion arm with respect to the body in a first angular direction. When angular movement in the first direction is prevented, the motion of the lost motion arm imparted by the cam to be transmitted to the body to provide for a first state of activation of the valve stem. When the plunger is in a second position, non-contacting with the lost motion arm, the lost motion arm is allowed to pivot relative to the body. Accordingly, the rocker arm assembly will be in a second state of total or partial deactivation of the valve. Additionally, the plunger has a second contact surface for contact with the lost motion arm second contact surface to cause the plunger to be cammed out of the first position when the plunger is in the first position and wherein the plunger first contact surface is not engaged with the lost motion arm's first contact surface.
It is a feature of the present invention to provide a selectively deactivatable rocker arm assembly that is self-relieving from a submarining condition.
Other features of invention will become more apparent to those skilled in the art from a reading of the following detailed description and upon reference to the drawings.


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