U.S. patent application number 11/128328 was filed with the patent office on 2005-12-15 for rocker arm system for engine valve actuation.
Invention is credited to Sledesky, Stephen, Usko, James N., Waldburger, David.
Application Number | 20050274341 11/128328 |
Document ID | / |
Family ID | 35783268 |
Filed Date | 2005-12-15 |
United States Patent
Application |
20050274341 |
Kind Code |
A1 |
Usko, James N. ; et
al. |
December 15, 2005 |
Rocker arm system for engine valve actuation
Abstract
Systems and methods for actuating engine valves are disclosed.
The systems may include primary and auxiliary rocker arms disposed
adjacent to each other on a rocker arm shaft. A rocker arm coupling
assembly may be disposed between the auxiliary rocker arm and the
primary rocker arm. The coupling assembly may include a piston
having a curved surface disposed in a bore formed in the primary
rocker arm, and a slot having a second radius of curvature formed
in the auxiliary rocker arm. The piston may be selectively
hydraulically locked into an extended position between the primary
and auxiliary rocker arms so as to selectively transfer one or more
auxiliary valve actuation motions from the auxiliary rocker arm to
the primary rocker arm.
Inventors: |
Usko, James N.; (North
Granby, CT) ; Sledesky, Stephen; (East Hartford,
CT) ; Waldburger, David; (Coventry, CT) |
Correspondence
Address: |
COLLIER SHANNON SCOTT, PLLC
3050 K STREET, NW
SUITE 400
WASHINGTON
DC
20007
US
|
Family ID: |
35783268 |
Appl. No.: |
11/128328 |
Filed: |
May 13, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60570814 |
May 14, 2004 |
|
|
|
Current U.S.
Class: |
123/90.16 ;
123/90.2; 123/90.27 |
Current CPC
Class: |
F01L 1/18 20130101; F01L
1/181 20130101; F01L 13/065 20130101; F01L 2001/186 20130101; F01L
1/267 20130101; F01L 13/06 20130101; F01L 2800/10 20130101; F01L
2305/00 20200501; F01L 13/00 20130101; F01L 2800/19 20130101; F01L
1/08 20130101; F01L 9/11 20210101 |
Class at
Publication: |
123/090.16 ;
123/090.2; 123/090.27 |
International
Class: |
F01L 001/34; F01L
001/02 |
Claims
What is claimed is:
1. A system for actuating an engine valve comprising: a rocker arm
shaft; a means for imparting primary valve actuation motion; a
primary rocker arm disposed on the rocker arm shaft, said primary
rocker arm being adapted to actuate an engine valve and receive
motion from the means for imparting primary valve actuation motion;
a means for imparting auxiliary valve actuation motion selected
from the group consisting of: engine braking motion, exhaust gas
recirculation motion, and brake gas recirculation motion; an
auxiliary rocker arm disposed on the rocker arm shaft adjacent to
the primary rocker arm, said auxiliary rocker arm being adapted to
receive motion from the means for imparting auxiliary valve
actuation motion; and a rocker arm coupling assembly disposed
between the auxiliary rocker arm and the primary rocker arm, said
coupling assembly being adapted to selectively transfer one or more
auxiliary valve actuation motions from the auxiliary rocker arm to
the primary rocker arm.
2. The system of claim 1, wherein said coupling assembly comprises:
an actuator piston disposed in a bore formed in said primary rocker
arm; and a slot formed in said auxiliary rocker arm for selectively
receiving said actuator piston.
3. The system of claim 2, wherein said actuator piston is disposed
in said auxiliary rocker arm, and said slot is formed in said
primary rocker arm.
4. The system of claim 2, wherein said actuator piston includes a
curved surface to facilitate engagement with said slot.
5. The system of claim 2, wherein said slot includes a curved
surface to facilitate engagement with said piston.
6. The system of claim 1, wherein said primary rocker arm comprises
an exhaust rocker arm, and said auxiliary rocker arm comprises an
intake rocker arm.
7. The system of claim 1, further comprising: a control valve; and
a lash piston disposed in a bore formed in said primary rocker
arm.
8. A system for actuating an engine valve comprising: a rocker arm
shaft; a means for imparting primary valve actuation motion; a
primary rocker arm disposed on the rocker arm shaft, said primary
rocker arm being adapted to actuate an engine valve and receive
motion from the means for imparting primary valve actuation motion;
a means for imparting auxiliary valve actuation motion; an
auxiliary rocker arm disposed on the rocker arm shaft adjacent to
the primary rocker arm, said auxiliary rocker arm being adapted to
receive motion from the means for imparting auxiliary valve
actuation motion; and a coupling assembly, comprising: an actuator
piston disposed in a bore formed in said primary rocker arm; and a
slot formed in said auxiliary rocker arm for selectively receiving
said actuator piston, wherein said actuator piston includes a
curved surface to facilitate engagement with said slot.
9. The system of claim 8, said coupling assembly being adapted to
selectively transfer one or more auxiliary valve actuation motions
from the auxiliary rocker arm to the primary rocker arm.
10. The system of claim 8, wherein said actuator piston includes a
curved surface to facilitate engagement with the slot.
11. The system of claim 8, wherein said primary rocker arm
comprises an exhaust rocker arm, and said auxiliary rocker arm
comprises an intake rocker arm.
12. The system of claim 8, further comprising: a control valve; and
a lash piston disposed in a bore formed in said primary rocker
arm.
13. The system of claim 8, the auxiliary valve actuation motion
selected from the group consisting of: engine braking motion,
exhaust gas recirculation motion, and brake gas recirculation
motion.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application relates to and claims priority on U.S.
Provisional Application No. 60/570,814, filed May 14, 2004 and
entitled "Rocker Arm System for Engine Valve Actuation," a copy of
which is incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to systems and methods for
actuating valves in internal combustion engines. In particular, the
present invention relates to systems and methods for actuating
valves using a one or more rocker arms.
BACKGROUND OF THE INVENTION
[0003] Internal combustion engines typically use either a
mechanical, electrical, or hydro-mechanical valve actuation system
to actuate the engine valves. These systems may include a
combination of camshafts, rocker arms, and push rods that are
driven by the engine's crankshaft rotation. When a camshaft is used
to actuate the engine valves, the timing of the valve actuation may
be fixed by the size and location of the lobes on the camshaft.
[0004] For each 360 degree rotation of the camshaft, the engine
completes a full cycle made up of four strokes (i.e., expansion,
exhaust, intake, and compression). Both the intake and exhaust
valves may be closed, and remain closed, during most of the
expansion stroke wherein the piston is traveling away from the
cylinder head (i.e., the volume between the cylinder head and the
piston head is increasing). During positive power operation, fuel
is burned during the expansion stroke and positive power is
delivered by the engine. The expansion stroke ends at the bottom
dead center point, at which time the piston reverses direction and
the exhaust valve may be opened for a main exhaust event. A lobe on
the camshaft may be synchronized to open the exhaust valve for the
main exhaust event as the piston travels upward and forces
combustion gases out of the cylinder. Near the end of the exhaust
stroke, another lobe on the camshaft may open the intake valve for
the main intake event at which time the piston travels away from
the cylinder head. The intake valve closes and the intake stroke
ends when the piston is near bottom dead center. Both the intake
and exhaust valves are closed as the piston again travels upward
for the compression stroke.
[0005] The above-referenced main intake and main exhaust valve
events are required for positive power operation of an internal
combustion engine. Additional auxiliary valve events, while not
required, may be desirable. For example, it may be desirable to
actuate the intake and/or exhaust valves during positive power or
other engine operation modes for compression-release engine
braking, bleeder engine braking, exhaust gas recirculation (EGR),
or brake gas recirculation (BGR). FIG. 8 illustrates examples of a
main exhaust event 600, and auxiliary valve events, such as a
compression-release engine braking event 610, a bleeder engine
braking event 620, exhaust gas recirculation event 630, and brake
gas recirculation event 640, which may be carried out by an exhaust
valve using various embodiments of the present invention to actuate
exhaust valves for main and auxiliary valve events. An example of a
main intake event 650 which may be carried out by an intake valve
is also shown.
[0006] With respect to auxiliary valve events, flow control of
exhaust gas through an internal combustion engine has been used in
order to provide vehicle engine braking. Generally, engine braking
systems may control the flow of exhaust gas to incorporate the
principles of compression-release type braking, exhaust gas
recirculation, exhaust pressure regulation, and/or bleeder type
braking.
[0007] During compression-release type engine braking, the exhaust
valves may be selectively opened to convert, at least temporarily,
a power producing internal combustion engine into a power absorbing
air compressor. As a piston travels upward during its compression
stroke, the gases that are trapped in the cylinder may be
compressed. The compressed gases may oppose the upward motion of
the piston. As the piston approaches the top dead center (TDC)
position, at least one exhaust valve may be opened to release the
compressed gases in the cylinder to the exhaust manifold,
preventing the energy stored in the compressed gases from being
returned to the engine on the subsequent expansion down-stroke. In
doing so, the engine may develop retarding power to help slow the
vehicle down. An example of a prior art compression release engine
brake is provided by the disclosure of the Cummins, U.S. Pat. No.
3,220,392 (November 1965), which is hereby incorporated by
reference.
[0008] During bleeder type engine braking, in addition to, and/or
in place of, the main exhaust valve event, which occurs during the
exhaust stroke of the piston, the exhaust valve(s) may be held
slightly open during remaining three engine cycles (full-cycle
bleeder brake) or during a portion of the remaining three engine
cycles (partial-cycle bleeder brake). The bleeding of cylinder
gases in and out of the cylinder may act to retard the engine.
Usually, the initial opening of the braking valve(s) in a bleeder
braking operation is in advance of the compression TDC (i.e., early
valve actuation) and then lift is held constant for a period of
time. As such, a bleeder type engine brake may require lower force
to actuate the valve(s) due to early valve actuation, and generate
less noise due to continuous bleeding instead of the rapid
blow-down of a compression-release type brake.
[0009] Exhaust gas recirculation (EGR) systems may allow a portion
of the exhaust gases to flow back into the engine cylinder during
positive power operation. EGR may be used to reduce the amount of
NO.sub.x created by the engine during positive power operations. An
EGR system can also be used to control the pressure and temperature
in the exhaust manifold and engine cylinder during engine braking
cycles. Generally, there are two types of EGR systems, internal and
external. External EGR systems recirculate exhaust gases back into
the engine cylinder through an intake valve(s). Internal EGR
systems recirculate exhaust gases back into the engine cylinder
through an exhaust valve(s). Embodiments of the present invention
primarily concern internal EGR systems.
[0010] Brake gas recirculation (BGR) systems may allow a portion of
the exhaust gases to flow back into the engine cylinder during
engine braking operation. Recirculation of exhaust gases back into
the engine cylinder during the intake stroke, for example, may
increase the mass of gases in the cylinder that are available for
compression-release braking. As a result, BGR may increase the
braking effect realized from the braking event.
[0011] A valve actuation system may be adapted to provide one or
more of the auxiliary valve events described above, in addition to
providing main valve events. Moreover, the motion imparted by a
valve train element to produce a main valve event may be used to
provide an auxiliary valve event. For example, a main intake event
lobe on a camshaft may be used to additionally actuate one or more
valves for an EGR event. In valve actuation systems providing both
main and auxiliary valve events, packaging, cost, reliability,
and/or performance are design factors that may be considered.
SUMMARY OF THE INVENTION
[0012] Responsive to the foregoing challenges, Applicant has
developed an innovative system for actuating an engine valve. In
one embodiment of the present invention, the system comprises: a
rocker arm shaft; a means for imparting primary valve actuation
motion; a primary rocker arm disposed on the rocker arm shaft, the
primary rocker arm being adapted to actuate an engine valve and
receive motion from the means for imparting primary valve actuation
motion; a means for imparting auxiliary valve actuation motion
selected from the group consisting of: engine braking motion,
exhaust gas recirculation motion, and brake gas recirculation
motion; an auxiliary rocker arm disposed on the rocker arm shaft
adjacent to the primary rocker arm, the auxiliary rocker arm being
adapted to receive motion from the means for imparting auxiliary
valve actuation motion; and a rocker arm coupling assembly disposed
between the auxiliary rocker arm and the primary rocker arm, the
coupling assembly being adapted to selectively transfer one or more
auxiliary valve actuation motions from the auxiliary rocker arm to
the primary rocker arm.
[0013] Applicant has further developed a system for actuating an
engine valve comprising: a rocker arm shaft; means for imparting
primary valve actuation motion; a primary rocker arm disposed on
the rocker arm shaft, the primary rocker arm being adapted to
actuate an engine valve and receive motion from the means for
imparting primary valve actuation motion; means for imparting
auxiliary valve actuation motion; an auxiliary rocker arm disposed
on the rocker arm shaft adjacent to the primary rocker arm, the
auxiliary rocker arm being adapted to receive motion from the means
for imparting auxiliary valve actuation motion; and a coupling
assembly, comprising: an actuator piston disposed in a bore formed
in the primary rocker arm; and a slot formed in the auxiliary
rocker arm for selectively receiving the actuator piston, wherein
the actuator piston includes a curved surface to facilitate
engagement with the slot.
[0014] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory only, and are not restrictive of the invention as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In order to assist the understanding of this invention,
reference will now be made to the appended drawings, in which like
reference characters refer to like elements.
[0016] FIG. 1 is a schematic view of a valve actuation system
according to a first embodiment of the present invention.
[0017] FIG. 2 is a schematic view of a valve actuation system
according to a second embodiment of the present invention.
[0018] FIG. 3 is an overhead view of a valve actuation system
according to the embodiment of the present invention shown in FIG.
1.
[0019] FIG. 4 is an overhead view of a valve actuation system
according to the embodiment of the present invention shown in FIG.
2.
[0020] FIG. 5A is a partial side view of a valve actuation system
in a first operating mode according to an embodiment of the present
invention.
[0021] FIG. 5B is a partial side view of a valve actuation system
in a second operating mode according to an embodiment of the
present invention.
[0022] FIG. 6 is a cross-sectional view of the valve actuation
system shown in FIG. 3 along section lines 6-6 according to an
embodiment of the present invention.
[0023] FIG. 7 is a detailed view of a rocker arm coupling assembly
according to an embodiment of the present invention.
[0024] FIG. 8 is a valve lift diagram depicting a number of
different and exemplary main and auxiliary engine valve events, one
or more of which may be produced with an embodiment of the present
invention.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0025] Reference will now be made in detail to an embodiment of the
present invention, an example of which is illustrated in the
accompanying drawings. With reference to FIG. 1, a system for
actuating engine valves is shown.
[0026] The valve actuating system includes at least two rocker arms
disposed on a rocker shaft (500, as shown in FIGS. 3 and 4). The at
least two rocker arms may include a primary rocker arm 100 and an
auxiliary rocker arm 200. The primary rocker arm 100 and the
auxiliary rocker arm 200 may be pivoted about the rocker shaft as a
result of motion imparted to them by motion imparting means 150 and
250, respectively. The motion imparting means 150 and 250 may
comprise a camshaft and/or another suitable motion imparting
device, such as, for example, a push tube or equivalent valve train
element. The rocker arms 100 and 200 are adapted to actuate one or
more engine valves 400 to produce an engine valve event by
contacting the valve directly, through a pin, or through a valve
bridge 410 (as shown in FIGS. 2, 5A, and 5B).
[0027] The engine valves 400 comprise poppet-type valves that are
used to control communication between the combustion chambers
(e.g., cylinders) in an engine and aspirating (e.g., intake and
exhaust) manifolds. The system may further include a rocker arm
coupling assembly 300 disposed between the primary rocker arm 100
and the auxiliary rocker arm 200 so as to selectively transfer one
or more valve actuation motions from the auxiliary rocker arm 200
to the primary rocker arm 100.
[0028] In one embodiment of the present invention, the primary
rocker arm 100 may comprise an exhaust rocker arm and the auxiliary
rocker arm 200 comprises an intake rocker arm. The exhaust rocker
arm 100 may be adapted to actuate one or more exhaust valves to
produce a main exhaust event, and an auxiliary valve event, such
as, an engine braking event, an exhaust gas recirculation (EGR)
event, and/or a brake gas recirculation event (BGR). The intake
rocker arm 200 is adapted to actuate one or more intake valves to
produce an engine valve event, such as, for example, a main intake
event. In one embodiment of the present invention, the exhaust
valve actuated by the exhaust rocker arm 100 and the intake valve
actuated by the intake rocker arm 200 are in the same engine
cylinder. It is contemplated, however, that the engine valves may
be in different engine cylinders. FIG. 3 is an overhead view of a
valve actuation system having a primary rocker arm (exhaust rocker
arm) 100, and an auxiliary rocker arm (intake rocker arm) 200.
[0029] In an alternative embodiment, as shown in FIG. 2, the
primary rocker arm 100 may comprise a dedicated rocker arm. The
dedicated rocker arm 100 may be adapted to actuate one or more
exhaust valves to produce an auxiliary valve event, such as, an
engine braking event, an exhaust gas recirculation (EGR) event,
and/or a brake gas recirculation event (BGR). In this embodiment,
the valve actuation system may further comprise an exhaust rocker
arm 175 adapted to actuate one or more exhaust valves to produce an
engine valve event, such as, for example, a main exhaust event. The
exhaust rocker arm 175 may be pivoted about the rocker shaft as a
result of motion imparted to them by motion imparting means 170.
FIG. 4 is an overhead view of a valve actuation system having a
primary rocker arm (dedicated rocker arm) 100, an auxiliary rocker
arm (intake rocker arm) 200, and an exhaust rocker arm 175.
[0030] In one embodiment of the present invention, the primary
rocker arm 100 may actuate one or more engine valves 400 to produce
an engine braking event. FIGS. 5A and 5B are side views, of the
valve actuation system according to an embodiment of the present
invention. With reference to FIGS. 5A and 5B, a cam 150 may include
a main exhaust event lobe 152, and an engine braking lobe 155, such
as a bleeder braking lobe (shown in FIGS. 5A-B) or a compression
release braking lobe. The depictions of the lobes on the cam 150
are intended to be illustrative only, and not limiting. It is
appreciated that the number, combination, size, location, and shape
of the lobes may vary markedly without departing from the intended
scope of the present invention. For example, in conjunction with
the embodiment of the present invention shown in FIG. 3, the cam
150 imparting motion to the primary rocker arm 100 may comprise a
dedicated cam for braking that does not include a main exhaust
event lobe.
[0031] The system may include a lash piston 120 disposed in a bore
formed in the primary rocker 100 and in selective contact with the
cam 150. A spring 126 biases the lash piston 120 away from the cam
150. The system may include a plunger 122 extending into the lash
piston bore, and a locking nut 124. The locking nut 124 may be
adjusted to extend the plunger 122 a desired distance within the
bore, and, correspondingly, adjust the position of the lash piston
120 relative to the cam 150. The lash piston 120 may include a
surface 128 suitable for contacting and following the motion of the
cam 150.
[0032] The rocker arm shaft 500 may include one or more internal
passages for the delivery of hydraulic fluid, such as engine oil,
to the rocker arms mounted thereon. Hydraulic fluid may be
selectively supplied to the primary rocker arm 100 by a fluid
supply valve (not shown), such as a solenoid valve, to initiate
engine braking operation.
[0033] A control valve 110 may be disposed in a bore 112 formed in
the primary rocker arm 100. The control valve 110 controls fluid
communication between the passage in the rocker shaft 500 and the
lash piston 120 through a hydraulic passage 105 formed in the
primary rocker arm 100. A spring 114 biases the control valve 110
into a first position, as shown in FIG. 5A, wherein the control
valve is seated in a detent 505 on the rocker shaft 500. In this
position, the control valve 110 substantially prevents fluid
communication to the lash piston 120, and holds the primary rocker
arm 100 in position on the rocker shaft 500.
[0034] When engine braking is desired, a supply valve, such as, for
example, a solenoid valve (not shown), is activated and hydraulic
fluid is supplied through the rocker shaft 500 to the control valve
bore 112. The hydraulic pressure created by the fluid causes the
control valve 110 to actuate from the first position, as shown in
FIG. 5A, corresponding to a non-braking operating mode, to a second
position, as shown in FIG. 5B, corresponding to braking operating
mode. With the control valve 110 in this position, hydraulic fluid
is permitted to flow through the hydraulic passage 105 to the lash
piston 120.
[0035] The intake rocker arm 200 may include a cam roller 210 for
following the motion of an intake cam 250 (not shown). The motion
from the intake cam 250 may be used to actuate an intake valve to
provide a main intake event. The motion from the intake cam 250
also may be transferred to the primary rocker arm 100 through the
coupling assembly 300 such that the primary rocker arm 100 actuates
the exhaust valve 400 to provide an auxiliary valve event, such as
an EGR valve event.
[0036] In one embodiment of the present invention, with reference
to FIG. 6, the rocker arm coupling assembly 300 may comprise an
actuator piston 310 disposed in a bore 320 formed in the primary
rocker arm 100, and a slot 330 formed in the intake rocker arm 200
that selectively receives the piston 310. A spring 340 biases the
piston 310 in the bore 320 away from the slot 330. It is
contemplated that the piston 310 may be disposed in a bore formed
in the auxiliary rocker arm 200 and the slot 330 formed in the
primary rocker arm 100 without departing from the scope of the
present invention.
[0037] Hydraulic fluid may be selectively supplied from a passage
in the rocker arm shaft 500 (not shown) to the bore 320 through a
hydraulic passage 360 formed in the primary rocker arm 100. The
hydraulic fluid may be selectively supplied by a fluid supply valve
(not shown), such as, for example, a solenoid valve. The hydraulic
pressure created by the fluid in the bore 320 causes the piston 310
to translate against the bias of the spring 340 and extend into the
slot 330. A mechanical stop 350 limits the travel of the piston 310
within the bore 320.
[0038] A partial detailed view of the coupling assembly 300
according to an embodiment of the present invention is shown in
FIG. 7. The piston 310 may include a slot engagement portion having
a curved surface 315. The slot 330 may include a piston engagement
portion having a curved surface 335 with a centerline 336. When the
piston 310 is engaged in the slot 330, rotation of the auxiliary
rocker arm 200 causes rotation of the primary rocker arm 100. The
piston surface 315 and the slot surface 335 may facilitate receipt
of the piston 310 into the slot 330, and, accordingly, transfer of
the auxiliary valve actuation motion from the auxiliary rocker arm
200 to the primary rocker arm 100. The location of the piston 310
and the slot 330 may be varied depending on the desired engine
valve lift.
[0039] Operation of an embodiment of the valve actuation system of
the present invention will now be described. During positive power
operation, when engine braking is not desired, hydraulic fluid is
not supplied to the control valve bore 112 through the rocker shaft
500. The control valve 110 remains seated in the rocker shaft
detent 505, in an "engine brake off" position, substantially
preventing hydraulic fluid communication to the lash piston 120.
Without sufficient hydraulic pressure acting on it, the lash piston
120 remains in a retracted position, as shown in FIG. 5A. As the
cam 150 rotates, the engine braking lobe 155 does not come into
contact with the lash piston 120, and accordingly, the engine
braking valve motion is not transferred to the engine valve(s) 400.
As the cam continues to rotate, the main exhaust event lobe 152
contacts the cam follower surface 128 of the lash piston 120 and
causes the primary rocker arm 100 to rotate about the rocker shaft
500 in a counter-clockwise direction (relative to the view shown in
FIG. 5A), and act on the engine valve 400 directly, through a pin,
or through a valve bridge, as shown in FIG. 5A. The primary rocker
arm 100 actuates the engine valve 400 to produce the main exhaust
valve event.
[0040] During engine braking operation, hydraulic fluid is supplied
to the control valve bore 112 through the rocker shaft 500. The
hydraulic pressure causes the control valve 110 to translate in the
bore 112 against the bias of the spring 114, as shown in FIG. 5B.
With the control valve 110 in this "engine brake on" position,
hydraulic fluid is permitted to flow through the hydraulic passage
105 to the lash piston 120. Under the pressure of the hydraulic
fluid, the lash piston 120 extends from the primary rocker arm 100
taking up the lash between the piston and the cam 150. As the cam
150 rotates, the cam follower surface 128 of the lash piston 120
follows the entire motion of the cam 120, including the engine
braking lobe 155. As a result, the engine braking valve motion is
transferred to the engine valve(s) 400 through the rocker arm
100.
[0041] When auxiliary exhaust valve actuation is desired for EGR
and/or BGR, for example, a solenoid supply valve (not shown) may be
activated so as to provide hydraulic fluid through the rocker shaft
500 through the hydraulic passage 360 to the actuator piston bore
320. The hydraulic fluid pressure created in the bore 320 causes
the piston 310 to translate against the bias of the spring 340 and
extend into the slot 330. As auxiliary valve motion is applied to
the auxiliary rocker arm 200, the auxiliary rocker arm 200 begins
to rotate. Because the piston 310 is engaged in the slot 330, the
rotation of the auxiliary rocker arm 200, in turn, causes the
primary rocker arm 100 to rotate and actuate the exhaust valve 400.
The timing of the auxiliary valve motion may be appropriate to
provide an auxiliary valve event, such as an EGR or BGR event.
[0042] With reference to FIG. 7, the piston surface 315 and the
slot surface 335 may facilitate receipt of the piston 310 into the
slot 330, and, accordingly, transfer of the auxiliary valve
actuation motion from the auxiliary rocker arm 200 to the primary
rocker arm 100. For example, if the piston 310 extends towards the
slot 330 after the auxiliary rocker arm 200 has begun to rotate
under the influence of the cam 250, the piston surface 315 may
contact the slot surface 335 to the right of the centerline 336. In
this case, because of the curvature of the surfaces 315 and 335,
the piston 310 may be pulled into position within the slot 330. If
the piston surface 315 contacts the slot surface 335 to the left of
the centerline 336, the piston 310 will not immediately engage the
slot 330. During the next rotation of the cam 250, as the cam
approaches lower base circle, the piston 310 will then engage the
slot 330. The shape of the surfaces 315 and 335 also may prevent
the piston from resting on the slot surface 335. This may reduce or
eliminate unwanted additional valve lift, and stress loading on the
auxiliary rocker arm 200.
[0043] It will be apparent to those skilled in the art that various
modifications and variations can be made in the construction,
configuration, and/or operation of the present invention without
departing from the scope or spirit of the invention. For example,
it is appreciated that the primary rocker arm 100 could be
implemented as an intake rocker arm, or an auxiliary rocker arm,
without departing from the intended scope of the invention.
Further, where engine braking functionality is not required, it is
contemplated that embodiments of the valve actuation system may be
provided without the control valve 110 and/or the lash piston 120.
In addition, the rocker shaft 500 may further include a hydraulic
passage adapted to provide lubrication fluid to the one or more
rocker arms. These and other modifications to the above-described
embodiments of the invention may be made without departing from the
intended scope of the invention.
* * * * *