U.S. patent application number 15/517957 was filed with the patent office on 2017-08-24 for engine braking method and system.
The applicant listed for this patent is Shanghai Universoon Auto Parts Co., Ltd.. Invention is credited to Yong Xi, Zhou YANG, Rujie ZHU.
Application Number | 20170241305 15/517957 |
Document ID | / |
Family ID | 55746186 |
Filed Date | 2017-08-24 |
United States Patent
Application |
20170241305 |
Kind Code |
A1 |
Xi; Yong ; et al. |
August 24, 2017 |
Engine Braking Method and System
Abstract
An engine braking method includes the steps of engaging a cam
roller(235) of an internal combustion engine with an engine power
cam(230) for an engine power operation; disengaging the cam
roller(235) from the engine power cam(230); losing a motion from
the engine power cam(230) and a motion of an engine valve(301)
associated with the motion from the engine power cam(230); engaging
the cam roller(235) with an engine braking cam(2302) for an engine
braking operation; transmitting a motion from the engine braking
cam(2302) to the engine valve(301); and generating an engine valve
motion for the engine braking operation. An engine braking system
includes an engine power cam(230) of an internal combustion engine;
an engine braking cam(2302) of the internal combustion engine; and
a cam roller(235) that is designed to engage with the engine power
cam(230) for an engine power operation and to engage with the
engine braking cam(2302) for an engine braking operation.
Inventors: |
Xi; Yong; (Shanghai, CN)
; YANG; Zhou; (Oak Ridge, NC) ; ZHU; Rujie;
(Shanghai, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Shanghai Universoon Auto Parts Co., Ltd. |
Shanghai |
|
CN |
|
|
Family ID: |
55746186 |
Appl. No.: |
15/517957 |
Filed: |
May 21, 2015 |
PCT Filed: |
May 21, 2015 |
PCT NO: |
PCT/IB2015/001625 |
371 Date: |
April 9, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01L 1/08 20130101; F01L
1/181 20130101; F01L 1/047 20130101; F01L 1/267 20130101; F01L
2305/00 20200501; F01L 13/06 20130101; F01L 2001/186 20130101; F01L
2013/0052 20130101; F02D 13/04 20130101; F01L 1/20 20130101; F01L
13/0036 20130101; F01L 1/26 20130101 |
International
Class: |
F01L 13/06 20060101
F01L013/06; F01L 1/18 20060101 F01L001/18; F01L 1/26 20060101
F01L001/26; F01L 1/20 20060101 F01L001/20; F01L 1/047 20060101
F01L001/047 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 15, 2014 |
CN |
201410544937.5 |
Oct 16, 2014 |
CN |
201410546875.1 |
Nov 6, 2014 |
CN |
201410620840.8 |
Nov 11, 2014 |
CN |
201410632591.4 |
Mar 4, 2015 |
CN |
201510095431.5 |
Mar 5, 2015 |
CN |
201510097866.3 |
Claims
1. An engine braking method comprising: engaging a cam roller of an
internal combustion engine with an engine power cam for an engine
power operation; disengaging the cam roller from the engine power
cam; losing a motion from the engine power cam and a motion of an
engine valve associated with the motion from the engine power cam;
engaging the cam roller with an engine braking cam for an engine
braking operation; transmitting a motion from the engine braking
cam to the engine valve; and generating an engine valve motion for
the engine braking operation.
2. The engine braking method according to claim 1, wherein the step
of engaging the cam roller with the engine power cam includes using
an axial cam roller driver to move the cam roller axially on a
roller shaft of the engine to a first axial position on the roller
shaft, and wherein the step of engaging the cam roller with the
engine braking cam includes using the axial cam roller driver to
move the cam roller axially on the roller shaft of the engine to a
second axial position on the roller shaft.
3. The engine braking method according to claim 2, wherein said
axial cam roller driver is integrated into a valve actuator of the
engine.
4. The engine braking method according to claim 3, wherein said
axial cam roller driver comprises a piston-spring mechanism in the
valve actuator, said piston-spring mechanism being engaged with one
end of a linkage or a sliding fork, the other end of the linkage or
the sliding fork being engaged with the cam roller.
5. The engine braking method according to claim 2, wherein said
axial cam roller driver is placed outside of a valve actuator of
the engine, said axial cam roller driver moving the cam roller
axially on the roller shaft through a linkage or a sliding
fork.
6. The engine braking method according to claim 2, wherein said cam
roller is designed to have a tendency to separate radially from the
cam shaft to enhance the axial motion of the cam roller on the
roller shaft.
7. The engine braking method according to claim 1, wherein the
engine power cam and the engine braking cam are located on a common
cam shaft, are adjacent to each other, and have the same or
substantially the same inner base circle.
8. The engine braking method according to claim 1, further
comprising a transition mechanism that assists the cam roller to
move between the engine power cam and the engine braking cam.
9. The engine braking method according to claim 1, further
comprising a transition mechanism, wherein the transition mechanism
includes an inclined line or surface transition between a first
height on the engine power cam and a second height on the engine
braking cam.
10. The engine braking method according to claim 1, wherein the
step of engaging the cam roller with the engine power cam includes
moving both the engine power cam and the engine braking cam to a
first axial position on a camshaft, and wherein the step of
engaging the cam roller with the engine braking cam includes moving
both the engine power cam and the engine braking cam to a second
axial position on the camshaft.
11. The engine braking method according to claim 1 , wherein the
cam roller is placed on a rocker arm of the engine, and the step of
engaging the cam roller with the engine power cam includes moving
the rocker arm to a first axial position on a rocker shaft, and
wherein the step of engaging the cam roller with the engine braking
cam includes moving the rocker arm to a second axial position on
the rocker shaft.
12. The engine braking method according to claim 1, wherein said
cam roller comprises an exhaust cam roller, said engine power cam
comprises a normal exhaust cam, and said engine braking cam
comprises a braking exhaust cam.
13. The engine braking method according to claim 12, comprising,
engaging the exhaust cam roller with the normal exhaust cam for the
engine power operation; disengaging the exhaust cam roller with the
normal exhaust cam; losing a motion from the normal exhaust cam and
a motion of an engine exhaust valve associated with the motion from
the normal exhaust cam; engaging the exhaust cam roller with the
braking exhaust cam for the engine braking operation; transmitting
a motion from the braking exhaust cam to the engine exhaust valve;
and generating an engine exhaust valve motion for the engine
braking operation.
14. The engine braking method according to claim 12, wherein said
braking exhaust cam comprises three braking exhaust cam lobes, the
first braking exhaust cam lobe being the first compression release
cam lobe and associated with a location near the engine compression
top dead center, the second braking exhaust cam lobe being the
second compression release cam lobe and associated with a location
near the engine exhaust top dead center, the third braking exhaust
cam lobe being the exhaust gas recirculation cam lobe and
associated with a location mainly in the engine expansion stroke,
immediately following the first compression release cam lobe or
directly engaging with the first compression release cam lobe.
15. The engine braking method according to claim 1, wherein said
cam roller comprises an exhaust cam roller and an intake cam
roller, said engine power cam comprises a normal exhaust cam and a
normal intake cam, and said engine braking cam comprises a braking
exhaust cam and a braking intake cam.
16. The engine braking method according to claim 15, comprising
engaging the exhaust cam roller with the normal exhaust cam for the
engine power operation, and engaging the intake cam roller with the
normal intake cam for the engine power operation; disengaging the
exhaust cam roller with the normal exhaust cam, and disengaging the
intake cam roller with the normal intake cam; losing a motion from
the normal exhaust cam and a motion of an engine exhaust valve
associated with the motion from the normal exhaust cam, and losing
a motion from the normal intake cam and a motion of an engine
intake valve associated with the motion from the normal intake cam;
engaging the exhaust cam roller with the braking exhaust cam for
the engine braking operation, and engaging the intake cam roller
with the braking intake cam for the engine braking operation;
transmitting a motion from the braking exhaust cam to the engine
exhaust valve, and transmitting a motion from the braking intake
cam to the engine intake valve; and generating an engine exhaust
valve motion for the engine braking operation, and generating an
engine intake valve motion for the engine braking operation.
17. The engine braking method according to claim 15, wherein said
braking exhaust cam comprises at least two braking exhaust cam
lobes, the first braking exhaust cam lobe being the first
compression release cam lobe and associated with a location near
the engine compression top dead center, the second braking exhaust
cam lobe being the second compression release cam lobe and
associated with a location near the engine exhaust top dead
center.
18. The engine braking method according to claim 15, wherein said
braking intake cam comprises at least two braking intake cam lobes,
the first braking intake cam lobe being associated with a location
mainly in the engine's intake stroke, and the second braking intake
cam lobe being associated with a location mainly in the engine's
expansion stroke.
19. The engine braking method according to claim 1, wherein the
engine has a valve actuator, said valve actuator comprising a
rocker arm and a valve bridge, one end of the rocker arm being
engaged with the engine power cam or the engine braking cam through
the cam roller, the other end of the rocker arm being over the
valve bridge, the two ends of the valve bridge being engaged
respectively with an inner valve that is close to the cams and with
an outer valve that is away from the cams, wherein said engine
braking method further comprises the following steps: disengaging
the rocker arm from the center of the valve bridge while the
connection of the cam roller to the engine power cam is being
switched to the engine braking cam, opening the inner valve by the
rocker arm while the outer valve being kept closed, and
transmitting the motion of the engine braking cam to the inner
valve, and generating the engine braking operation.
20. The engine braking method according to claim 19, wherein a lost
motion mechanism is provided to disengage the rocker arm from the
center of the valve bridge, said lost motion mechanism being
integrated into the valve actuator.
21-41. (canceled)
Description
FIELD OF THE INVENTION
[0001] The present application relates to engine braking,
particularly to an engine braking method and system.
BACKGROUND OF THE INVENTION
[0002] In the prior art, conventional valve actuation for a vehicle
engine is well known and its application has more than one hundred
years of history. It uses a conventional valve actuator to control
engine valve motion, including the normal exhaust valve motion and
normal intake valve motion, for engine power operation. However,
due to the additional requirements on engine emission and engine
braking, more and more engines need to produce an auxiliary engine
valve event, such as an exhaust gas recirculation event or an
engine braking event, in addition to the normal engine valve event.
The engine brake has gradually become the must-have device for the
heavy-duty commercial vehicle engines.
[0003] The engine braking technology is also well known. During
engine braking, the engine is temporarily converted to an air
compressor, and in the conversion process, fuel supply is cut off,
and the exhaust valve is opened near the end of the compression
stroke of the engine piston, thereby allowing the compressed gases
(being air during braking) to be released. The energy absorbed by
the compressed gases during the compression stroke cannot be
returned to the engine piston at the subsequent expansion stroke,
but is dissipated by the engine exhaust and cooling systems, which
results in an effective engine braking and the slow-down of the
vehicle.
[0004] An example of engine brake devices in the prior art is
disclosed by Cummins in U.S. Pat. No. 3,220,392. The invention
utilizes a hydraulic linkage to transfer the motion from the nearby
injection cam or exhaust cam to an engine valve, creating a
compression release braking valve event in addition to the
conventional engine valve event. The invention produces only a
compression-release braking in each four-stroke engine cycle.
[0005] U.S. Pat. No. 4,572,114 (1986) discloses two-stroke engine
braking devices and methods in a four-stroke engine. Thus, for each
two-stroke or each crankshaft rotation of the engine, one engine
braking is generated. Theoretically, the braking power from two
compression releases of the two-stroke braking in each engine
four-stroke cycle would be twice that of conventional four-stroke
braking power. However, since the invention uses two hydraulic
actuation systems with great structural complexity, there is no
practical application.
[0006] U.S. Pat. No. 5,537,976 (1996) discloses another two-stroke
engine braking apparatus and method using a cam drive, hydraulic
linkage, high-speed solenoid valve and electronic control means, to
achieve the valve motion. Because within each cycle, the solenoid
valve is required to open at least once, the solenoid valve has a
particularly high reliability and durability requirements. Plus
other issues with the hydraulically actuation, such as valve
seating velocity control, engine cold start, etc., the invention
has no real application.
[0007] U.S. Pat. No. 6,293,248 (2001) discloses yet another
two-stroke engine braking apparatus and method. In order to achieve
the two-stroke engine braking on a four-stroke engine, in addition
to the four cams, four rocker arms must be used: two exhaust rocker
arms (one for firing and the other for braking) and two intake
rocker arms (one for firing and the other for braking). The
structure and the control are complex. Also, hydraulic actuation is
used to open the engine valves.
SUMMARY OF THE INVENTION
[0008] An object of the present invention is to provide an engine
braking method and system to solve the technical problems in the
prior art, such as complex structure and control, poor reliability
and durability of hydraulic valve actuation, and limited
applications. The mechanical loading (through solid contact) of the
present invention also eliminates the failure modes of hydraulic
loading (through liquid volume), such as high oil pressure, high
leakage and high compliance.
[0009] According to one aspect of the present invention, a new
engine braking method comprises the following steps: [0010] 1.
engaging a cam roller of an internal combustion engine with an
engine power cam for an engine power operation; [0011] 2.
disengaging the cam roller from the engine power cam; [0012] 3.
losing a motion from the engine power cam and a motion of an engine
valve associated with the motion from the engine power cam; [0013]
4. engaging the cam roller with an engine braking cam for an engine
braking operation; [0014] 5. transmitting a motion from the engine
braking cam to the engine valve; and generating an engine valve
motion for the engine braking operation.
[0015] Further, the step of engaging the cam roller with the engine
power cam includes using an axial cam roller driver to move the cam
roller axially on a roller shaft of the engine to a first axial
position on the roller shaft, and wherein the step of engaging the
cam roller with the engine braking cam includes using the axial cam
roller driver to move the cam roller axially on the roller shaft of
the engine to a second axial position on the roller shaft.
[0016] Further, the axial cam roller driver is integrated into a
valve actuator of the engine.
[0017] Further, the axial cam roller driver comprises a
piston-spring mechanism in the valve actuator, said piston-spring
mechanism being engaged with one end of a linkage or a sliding
fork, the other end of the linkage or the sliding fork being
engaged with the cam roller.
[0018] Further, the axial cam roller driver is placed outside of a
valve actuator of the engine, said axial cam roller driver moving
the cam roller axially on the roller shaft through a linkage or a
sliding fork.
[0019] Further, the cam roller is designed to have a tendency to
separate radially from the cam shaft to enhance the axial motion of
the cam roller on the roller shaft.
[0020] Further, the engine power cam and the engine braking cam are
located on a common cam shaft, are adjacent to each other, and have
the same or substantially the same inner base circle.
[0021] Further, the engine braking method comprises a transition
mechanism that assists the cam roller to move between the engine
power cam and the engine braking cam.
[0022] Further, the engine braking method comprises a transition
mechanism, wherein the transition mechanism includes an inclined
line or surface transition between a first height on the engine
power cam and a second height on the engine braking cam.
[0023] Further, the step of engaging the cam roller with the engine
power cam includes using an axial cam driver to move both the
engine power cam and the engine braking cam axially on the camshaft
to a first axial position on the camshaft, and wherein the step of
engaging the cam roller with the engine braking cam includes using
the axial cam driver to move both the engine power cam and the
engine braking cam axially on the camshaft of the engine to a
second axial position on the camshaft.
[0024] Further, the cam roller is placed on a rocker arm of the
engine, and the step of engaging the cam roller with the engine
power cam includes using an axial rocker arm driver to move the
rocker arm axially on a rocker shaft of the engine to a first axial
position on the rocker shaft, and wherein the step of engaging the
cam roller with the engine braking cam includes using the axial
rocker arm driver to move the rocker arm axially on the rocker
shaft of the engine to a second axial position on the rocker
shaft.
[0025] Further, the cam roller comprises an exhaust cam roller,
said engine power cam comprises a normal exhaust cam, and said
engine braking cam comprises a braking exhaust cam.
[0026] Further, the engine braking method comprises the following
steps: [0027] 1. engaging the exhaust cam roller with the normal
exhaust cam for the engine power operation; [0028] 2. disengaging
the exhaust cam roller with the normal exhaust cam; [0029] 3.
losing a motion from the normal exhaust cam and a motion of an
engine exhaust valve associated with the motion from the normal
exhaust cam; [0030] 4. engaging the exhaust cam roller with the
braking exhaust cam for the engine braking operation; [0031] 5.
transmitting a motion from the braking exhaust cam to the engine
exhaust valve; and [0032] 6. generating an engine exhaust valve
motion for the engine braking operation.
[0033] Further, the braking exhaust cam comprises three braking
exhaust cam lobes, the first braking exhaust cam lobe being the
first compression release cam lobe and associated with a location
near the engine compression top dead center, the second braking
exhaust cam lobe being the second compression release cam lobe and
associated with a location near the engine exhaust top dead center,
the third braking exhaust cam lobe being the exhaust gas
recirculation cam lobe and associated with a location mainly in the
engine expansion stroke, immediately following the first
compression release cam lobe or directly connecting to the first
compression release cam lobe.
[0034] Further, the cam roller comprises an exhaust cam roller and
an intake cam roller, said engine power cam comprises a normal
exhaust cam and a normal intake cam, and said engine braking cam
comprises a braking exhaust cam and a braking intake cam.
[0035] Further, the engine braking method comprises the following
steps: [0036] 1. engaging the exhaust cam roller with the normal
exhaust cam for the engine power operation, and engaging the intake
cam roller with the normal intake cam for the engine power
operation; [0037] 2. disengaging the exhaust cam roller with the
normal exhaust cam, and disengaging the intake cam roller with the
normal intake cam; [0038] 3. losing a motion from the normal
exhaust cam and a motion of an engine exhaust valve associated with
the motion from the normal exhaust cam, and losing a motion from
the normal intake cam and a motion of an engine intake valve
associated with the motion from the normal intake cam; [0039] 4.
engaging the exhaust cam roller with the braking exhaust cam for
the engine braking operation, and engaging the intake cam roller
with the braking intake cam for the engine braking operation;
[0040] 5. transmitting a motion from the braking exhaust cam to the
engine exhaust valve, and transmitting a motion from the braking
intake cam to the engine intake valve; and [0041] 6. generating an
engine exhaust valve motion for the engine braking operation, and
generating an engine intake valve motion for the engine braking
operation.
[0042] Further, the braking exhaust cam comprises at least two
braking exhaust cam lobes, the first braking exhaust cam lobe being
the first compression release cam lobe and associated with a
location near the engine compression top dead center, the second
braking exhaust cam lobe being the second compression release cam
lobe and associated with a location near the engine exhaust top
dead center.
[0043] Further, the braking intake cam comprises at least two
braking intake cam lobes, the first braking intake cam lobe being
associated with a location mainly in the engine's intake stroke,
and the second braking intake cam lobe being associated with a
location mainly in the engine's expansion stroke.
[0044] Further, the engine has a valve actuator, said valve
actuator comprising a rocker arm and a valve bridge, one end of the
rocker arm being engaged with the engine power cam or the engine
braking cam through the cam roller, the other end of the rocker arm
being over the valve bridge, the two ends of the valve bridge being
engaged respectively with an inner valve that is close to the cams
and with an outer valve that is away from the cams, wherein said
engine braking method further comprises the following steps: [0045]
1. disengaging the rocker arm from the center of the valve bridge
while the engagement of the cam roller to the engine power cam is
being switched to the engine braking cam, [0046] 2. opening the
inner valve by the rocker arm while the outer valve being kept
closed, [0047] 3. transmitting the motion of the engine braking cam
to the inner valve, and generating the engine braking
operation.
[0048] Further, a lost motion mechanism is provided to disengage
the rocker arm from the center of the valve bridge, said lost
motion mechanism being integrated into the valve actuator.
[0049] Further, the lost motion mechanism comprises a hydraulic
piston mechanism integrated with the rocker arm, said hydraulic
piston mechanism including an auto lash adjusting system.
[0050] Further, the lost motion mechanism comprises a mechanical
linkage mechanism integrated with the rocker arm, said rocker arm
comprising a full rocker arm for actuating the inner valve and a
half rocker arm for actuating both the inner valve and the outer
valve, one end of the full rocker arm being engaged with one of the
two cams through the cam roller, the other end of the full rocker
arm being engaged with the inner valve, the half rocker arm and the
full rocker arm being rotationally placed on a common rocker shaft,
the end of the half rocker arm being over the center of the valve
bridge, and the two rocker arms being linked through the mechanical
linkage mechanism.
[0051] The present invention is also a new engine braking system,
which comprises an engine power cam on a camshaft of an
international combustion engine; an engine braking cam on the
camshaft of the internal combustion engine; and a cam roller that
is designed to engage with the engine power cam for an engine power
operation and to engage with the engine braking cam for an engine
braking operation.
[0052] Further, the new engine braking system comprises an axial
cam roller driver, and a roller shaft, wherein the cam roller is
rotationally placed on the roller shaft, wherein the cam roller is
also axially slidable along the roller shaft between a first axial
position and a second axial position, in said first axial position,
the cam roller being engaged with the engine power cam for the
engine power operation, and in said second axial position, the cam
roller being engaged with the engine braking cam for the engine
braking operation.
[0053] Further, the axial cam roller driver comprises a
piston-spring mechanism integrated into a valve actuator of the
engine, said piston-spring mechanism being engaged with one end of
a linkage or a sliding fork, the other end of the linkage or the
sliding fork being engaged with the cam roller.
[0054] Further, the axial cam roller driver is placed outside of a
valve actuator of the engine, and wherein said axial cam roller
driver moves the cam roller axially on the roller shaft through a
linkage or a sliding fork.
[0055] Further, the cam roller is designed to have a tendency to
separate radially from the cam shaft to enhance the axial motion of
the cam roller on the roller shaft.
[0056] Further, the engine power cam and the engine braking cam are
located on a common cam shaft, are adjacent to each other and have
the same or substantially the same inner base circle.
[0057] Further, the new engine brake system comprises a transition
mechanism that assists the cam roller to move between the engine
power cam and the engine braking cam.
[0058] Further, the new engine brake system comprises a transition
mechanism, wherein the transition mechanism includes an inclined
surface transition between a first height on the engine power cam
and a second height on the engine braking cam.
[0059] Further, the new engine brake system comprises an axial cam
driver, wherein both the engine power cam and the engine braking
cam are axially slidable along the camshaft between a first axial
position and a second axial position, in said first axial position,
the cam roller being engaged with the engine power cam for the
engine power operation, and in said second axial position, the cam
roller being engaged with the engine braking cam for the engine
braking operation.
[0060] Further, the new engine brake system comprises an axial
rocker arm driver, wherein the cam roller is placed on a rocker arm
of the engine, and said rocker arm is axially slidable along a
rocker shaft of the engine between a first axial position and a
second axial position, in said first axial position, the cam roller
on the rocker arm being engaged with the engine power cam for the
engine power operation, and in said second axial position, the cam
roller on the rocker arm being engaged with the engine braking cam
for the engine braking operation
[0061] Further, the engine power cam comprises a normal exhaust
cam, and said engine braking cam comprises a braking exhaust
cam.
[0062] Further, the braking exhaust cam comprises three braking
exhaust cam lobes, the first braking exhaust cam lobe being the
first compression release cam lobe and associated with a location
near the engine compression top dead center, the second braking
exhaust cam lobe being the second compression release cam lobe and
associated with a location near the engine exhaust top dead center,
the third braking exhaust cam lobe being the exhaust gas
recirculation cam lobe and associated with a location mainly in the
engine expansion stroke, immediately following the first
compression release cam lobe or directly engaging with the first
compression release cam lobe.
[0063] Further, the engine power cam comprises a normal exhaust cam
and a normal intake cam, and said engine braking cam comprises a
braking exhaust cam and a braking intake cam.
[0064] Further, the braking exhaust cam comprises at least two
braking exhaust cam lobes, the first braking exhaust cam lobe being
the first compression release cam lobe and associated with a
location near the engine compression top dead center, the second
braking exhaust cam lobe being the second compression release cam
lobe and associated with a location near the engine exhaust top
dead center.
[0065] Further, the braking intake cam comprises at least two
braking intake cam lobes, the first braking intake cam lobe being
associated with a location mainly in the engine's intake stroke,
and the second braking intake cam lobe being associated with a
location mainly in the engine's expansion stroke.
[0066] Further, the engine braking system comprises a lost motion
mechanism, wherein said lost motion mechanism is integrated into
the engine's valve actuator, wherein when said lost motion
mechanism is actuated, the engine's rocker arm is disconnected to
the center of the engine's valve bridge, said valve bridge having
two ends being engaged respectively with the inner valve that is
close to the cams and with an outer valve that is away from the
cams, and there being also a single valve linkage mechanism between
the rocker arm and the inner valve.
[0067] Further, lost motion mechanism comprises a hydraulic piston
mechanism integrated with the rocker arm, said hydraulic piston
mechanism being also an auto lash adjusting system.
[0068] Further, the lost motion mechanism comprises a mechanical
linkage mechanism integrated with the rocker arm, said rocker arm
comprises a full rocker arm for actuating the inner valve and a
half rocker arm for actuating both the inner valve and the outer
valve, one end of the full rocker arm being engaged with one of the
two cams through the cam roller, the other end of the full rocker
arm being engaged with the inner valve, the half rocker arm and the
full rocker arm are rotationally placed on a common rocker shaft,
the end of the half rocker arm being over the center of the valve
bridge, and the two rocker arms being linked through the mechanical
linkage mechanism.
[0069] Further, the engine braking system comprises an
anti-no-follow mechanism, wherein said anti-no-follow mechanism
comprises an elastic part.
[0070] A working principle of the present invention is summarized
as follows. When an engine power operation needs to be converted to
an engine braking operation, an engagement of a cam roller with an
engine power cam is switched to an engine braking cam. The
switching is accomplished in one or more of three different ways:
(1) using an axial cam roller driver to move the cam roller axially
on a roller shaft from a first axial position on the roller shaft
where the cam roller is engaged with the engine power cam to a
second axial position on the roller shaft where the cam roller is
engaged with the engine braking cam; (2) using an axial rocker arm
driver to move a rocker arm axially on a rocker arm shaft from a
first axial position on the rocker shaft where a cam roller on the
rocker arm is engaged with the engine power cam to a second axial
position on the rocker shaft where the cam roller on the rocker arm
is engaged with the engine braking cam; and (3) using an axial cam
driver to move both engine power cam and engine braking cam axially
on a camshaft from a first axial position on the camshaft where a
cam roller is engaged with the engine power cam to a second axial
position on the camshaft where the cam roller is engaged with the
engine braking cam. After the switching, the motion from the engine
power cam and the motion of an engine valve associated with the
motion from the engine power cam are lost, while the motion from
the engine braking cam is transmitted to the engine valve for the
engine braking operation.
[0071] The present application has positive and significant
advantages over the prior art. By changing the engagement of the
cam roller from the engine power cam to the engine braking cam, the
present invention achieves the conversion between the engine power
(firing) operation and the engine braking operation. The simple and
compact structure is easy to assemble and manufacture with a wide
range of applications and other advantages. Since the engine
braking cam and the engine power cam are independent from each
other, engine braking performance can be optimized. The present
invention uses a solid chain (mechanical linkage) to transfer
loads, eliminating the high oil pressure, high compliance and high
leakage as well as hydraulic jacking and other disadvantages or
failure modes linked to the hydraulic loading of conventional
engine brakes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0072] FIG. 1 is an engine braking control diagram used in the
first embodiment of the engine braking method of the present
invention.
[0073] FIG. 2 is a schematic view showing an engine braking device
(side view) according to the first embodiment of the engine braking
method of the present invention.
[0074] FIG. 3 is a schematic diagram showing an axial cam roller
driver (partial top view) when the cam roller is in the first axial
position according to the first embodiment of the engine braking
method of the present invention.
[0075] FIG. 4 is a schematic diagram showing an axial cam roller
driver (partial top view) when the cam roller is at the second
axial position according to the first embodiment of the engine
braking method of the present invention.
[0076] FIG. 5 is a schematic diagram showing the normal cam (or
valve) lift profiles.
[0077] FIG. 6 is a schematic diagram showing a braking exhaust cam
(or valve) lift profile during the engine braking operation
according to the first embodiment of the engine braking method of
the present invention.
[0078] FIG. 7 is a schematic diagram showing braking exhaust and
braking intake cam (or valve) lift profiles during the engine
braking operation according to the second embodiment of the engine
braking method of the present invention.
[0079] FIG. 8 is a schematic view showing an engine braking system
according to the third embodiment of the engine braking method of
the present invention.
[0080] FIG. 9 is a schematic view showing a liquid flow control
valve according to the third embodiment of the engine braking
method of the present invention.
[0081] FIG. 10 is a schematic view showing an engine braking system
according to the fourth embodiment of the engine braking method of
the present invention.
[0082] FIG. 11 is a schematic view showing an engine braking system
(side view) according to the fifth embodiment of the engine braking
method of the present invention.
[0083] FIG. 12 is a top view of the fifth embodiment when the full
rocker arm is in the first axial position on the rocker shaft and
the cam roller is engaged with the engine power cam.
[0084] FIG. 13 is a top view of the fifth embodiment when the full
rocker arm is in the second axial position on the rocker shaft and
the cam roller is engaged with the engine braking cam.
[0085] FIG. 14 is a schematic view showing an engine braking system
(side view) according to the sixth embodiment of the engine braking
method of the present invention.
[0086] FIG. 15 is an engine braking control diagram used in the
seventh embodiment of the engine braking method of the present
invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
First Embodiment
[0087] FIGS. 1 to 6 are used to describe the first embodiment of
the engine braking method of the present invention. FIG. 1 is an
engine braking control diagram of the invention. The engine power
operation 10 follows the solid line arrows on the left in FIG. 1.
The engine brake controller 50 is turned off (not energized). The
axial cam roller driver 100 biases the cam roller 235 to a first
axial position. The cam roller 235 is engaged with an engine power
cam 230, and the motion from the engine power cam 230 is
transmitted to an engine valve for the engine power operation 10.
When the engine power operation 10 needs to be converted to an
engine braking operation 20, the engine braking control is switched
to the right in FIG. 1 and follow the dashed line arrows. The
engine brake controller 50 is now turned on (energized). The axial
cam roller driver 100 moves the cam roller 235 from the first axial
position to the second axial position. The cam roller 235 is
disengaged from the engine power cam 230 and switched to an
engagement with an engine braking cam 2302. The motion from the
engine power cam 230 is completely lost, while the motion from the
engine braking cam 2302 is transmitted to the engine valve for the
engine braking operation 20. As can be seen from FIG. 1, the engine
power operation 10 and the engine braking operation 20 are
independent of each other.
[0088] FIG. 2 is a schematic diagram (side view) of an engine brake
device of the present invention. The engine's valve actuator 200,
for both intake valve actuator and exhaust valve actuator, includes
two cams (an engine power cam 230 and an engine braking cam 2302),
a cam roller 235 and a roller shaft 231. The cam roller 235 can
rotate on the roller shaft 231. It can also slide axially along the
roller shaft between a first axial position (FIG. 3) and a second
axial position (FIG. 4). The engine power cam (cam lobe 220) and
the engine braking cam (cam lobes 232 and 233) have different lift
and timing. Note that the engine braking cam lobes 232 and 233 have
much lower lifts than the engine power cam lobe 220. The two cams
are located on a common camshaft 225, adjacent to each other and
have the same or substantially the same inner base circle. The
valve actuator 200 further includes a rocker arm 210 rotationally
mounted on a rocker shaft 205. There is a flow passage 211 in the
rocker shaft 205. Through a valve lash adjusting mechanism, the
rocker arm 210 actuates the engine valve 301 (shown here is a
single valve, but the present invention is equally applicable to
dual-valve engine, but a valve bridge is needed for actuating two
engine valves). The valve 301 is biased by a valve spring 311 on
valve seat 320 in the engine block 500 to prevent gases from
flowing between the engine cylinder and gas duct 600. The valve
lash adjustment mechanism includes a valve lash adjusting screw
110, a locking nut 105, and an elephant foot 114.
[0089] FIGS. 3 and 4 (partial top views) illustrate the axial cam
roller driver 100 used in the first embodiment of the engine
braking method of the present invention with the cam roller 235
being movable between a first axial position and a second axial
position. Near the cam side, there is a gap or open slot in the end
of the rocker arm 210 (rocker arm 210 shown here can also be a cam
follower of a push-tube engine). A roller shaft 231 is provided
across the gap, and on the roller shaft 231 provided with the cam
roller 235. The cam roller 235 can not only rotate on the roller
shaft 231, but also move axially along the roller shaft 231. The
length of the roller shaft 231 in the gap is larger than the width
of the cam roller 235. The cam roller 235 has a first axial
position (FIG. 3) and a second axial position (FIG. 4) on the
roller shaft 231. The axial cam roller driver 100 is integrated in
the rocker arm 210, which moves the cam roller 235 between the
first axial position and the second axial position through a
linkage or a sliding fork 236.
[0090] One end of the sliding fork 236 includes two spaced prongs,
and each of the two prongs has a hole or slot 238 and 239. The
roller shaft 231 passes through the holes or slots 238 and 239 in
the two prongs, and the cam roller 235 is placed between the two
prongs. The other end 237 of the sliding fork 236 is engaged with
the axial cam roller driver 100 (the way of the engagement may
vary). The axial cam roller driver 100 shown here is a
piston-spring mechanism integrated in the valve actuator (the
rocker arm 210). The piston-spring mechanism includes a piston 164
disposed within a piston bore 260, with its axial direction being
parallel to the axis of the roller shaft 231. There is a fluid
passage 214 on one side of the piston 164, and a spring 156 on the
other side. Piston 164 is pushed separately by the spring force
near the spring side (left side in the Figures) and by a fluid
(e.g. engine oil) force near the fluid passage side (right side in
the Figures). The two forces have opposite directions and make the
piston 164 move axially. The piston-spring mechanism is engaged
with one end 237 of the sliding fork 236 (the connection here is
that the end 237 of the sliding fork 236 is located in annular
groove 126 of the piston 164, and the connecting end 237 having a
guide groove 270 in the rocker arm 210). The motion of the piston
164 is transmitted to the cam roller 235 through the sliding fork
136, and the cam roller 235 being moved between the first axial
position (FIG. 3) and the second axial position (FIG. 4) on the
roller shaft 231.
[0091] When the cam roller 235 is in the first axial position, it
is engaged with the engine power cam 230 on the camshaft 225 (FIG.
3). When the cam roller 235 is in the second axial position, it is
engaged with the engine braking cam 2302 on the camshaft 225 (FIG.
4). Preferably the engine power cam 230 and the engine braking cam
2302 are designed to have the same or substantially the same inner
base circle, and to have an axial transition mechanism that assists
the cam roller to move between them, such as an inclined surface
transition between a first height on the engine power cam 230 to a
second height on the engine braking cam 2302, so that the cam
roller 235 could have a smooth and stable transition when the
engagement of the cam roller 235 is switched between the two cams.
Alternatively, the transition mechanism could include any other
suitable mechanism. For example, the transition may be accomplished
by switching between the two cams only when the height difference
between the engine power cam 230 and the engine braking cam 2302 is
below a certain value to reduce any impact during the switch. Also
it is better for the cam roller 235 to have a tendency to separate
radially from the camshaft 225 to enhance the axial motion of the
cam roller 235 on the roller shaft 231.
[0092] The operation of this embodiment is as follows. Spring 156
biases piston 164 to the bottom surface of piston bore 260 near the
side with fluid passage 214 (the right side), The piston 164,
through the sliding fork 236, pushes the cam roller 235 to the
first axial position (the right side in FIG. 3), and the cam roller
235 is engaged with the engine power cam 230. The motion of the
engine power cam 230 is transmitted to the engine valve 301 (FIG.
2), generating the valve motion for engine power operation (see
FIG. 5 for the valve profile 220 (exhaust) or 321 (intake)). When
it is desired to convert the engine power operation 10 to the
engine braking operation 20, the engine brake controller 50 is
turned on to provide a driving force to the axial cam roller driver
100. Fluid, such as engine oil through the fluid passages, for
example, 211 and 214 in the rocker shaft and rocker arm, flows into
piston bore 260. The oil pressure overcomes the force of spring 156
and moves piston 164 in piston bore 260 to the side with spring 156
(left side), and piston 164 pushes the sliding fork 236 with the
cam roller 235 to the second axial position (left side in FIG. 4).
The cam roller 235 is disengaged from the engine power cam 230 and
engaged with the engine braking cam 2302. The motion of the engine
power cam 230 is lost, while the motion of the engine braking cam
2302 is transmitted to the engine valve 301 for the engine braking
operation.
[0093] Note that the above description applies to both the exhaust
valve actuation and the intake valve actuation. However, in this
embodiment, the engine braking operation 20 simply switches the
power operation of the exhaust valve to the engine braking
operation, the engine power operation of the intake valve is
maintained without any change. The intake valve motion for engine
power operation is shown in FIG. 5 (the intake lift curve 321) and
the engine braking exhaust valve motion which is from the braking
exhaust cam 2302, as shown in FIG. 6 as an example, is generated by
three braking exhaust cam lobes. The first braking exhaust cam lobe
is the first compression release cam lobe 232, located near the
engine's compression top dead center (0.degree. crank angle); the
second braking exhaust cam lobe is the second compression release
cam lobe 233, located near the engine's exhaust top dead center
(360.degree. crank angle); and the third braking exhaust cam lobe
is the exhaust gas recirculation cam lobe 231, mainly located in
the expansion stroke of the engine and immediately following the
first compression-release cam lobe 232 or directly connecting to
the first compression release cam lobe 232 to form a combined cam
lobe.
Second Embodiment
[0094] In this embodiment of the present invention, the intake
valve engine braking operation is added to the above-described
embodiment. The exhaust valve actuator and the intake valve
actuator are both provided with the axial cam roller driver 100,
which has the same working principle and procedure as described in
the first embodiment, and is not repeated here.
[0095] The engine power cams in the present embodiment are the same
as embodiment one, including both the normal exhaust cam and the
normal intake cam, whose lift curves are shown in FIG. 5 (220 for
exhaust and 312 for intake). The braking cams include the braking
exhaust cam and a braking intake cam, whose lift curves are shown
in FIGS. 7 (232 and 233 for exhaust, and 322 and 323 for intake).
Therefore, the present embodiment has one more braking intake cam
than the first embodiment. When the engine power operation is
needed, the axial cam roller driver 100 biases the cam roller 235
to the first axial position, both the intake and exhaust cam
rollers are engaged with the normal intake and exhaust cams
respectively, whose motions are passed to the engine's intake and
exhaust valves to produce the intake and exhaust valve motions for
the engine power operation (see FIG. 5 for the intake and exhaust
lift curves 321 and 220).
[0096] When it is desired to convert the engine power operation 10
to the engine braking operation 20, the engine brake controller 50
is turned on to provide a driving force to the axial cam roller
driver 100, which moves the exhaust cam roller 235 from the first
axial position to the second axial position, switching the
connection of the exhaust cam roller 235 from the normal exhaust
cam 230 to the braking exhaust cam 2302, losing the normal exhaust
cam motion and the corresponding normal exhaust valve motion,
generating the engine braking exhaust valve motion. At the same
time, the intake cam roller is also moved from the first axial
position to the second axial position, switching the connection of
the intake cam roller from the normal intake cam to the braking
intake cam, losing the normal intake cam motion and the
corresponding normal intake valve motion, generating the engine
braking intake valve motion.
[0097] As shown in FIG. 7, the braking exhaust cam has two braking
exhaust cam lobes, one being the first compression-release cam lobe
232 located near the engine's compression top dead center
(0.degree. crank angle), and the other being the second compression
release cam lobe 233 located near the engine's exhaust top dead
center (360.degree. crank angle). FIG. 7 also shows two braking
intake cam lobes for the braking intake cam, one being the first
braking intake cam lobe 322, mainly located in the intake stroke of
the engine, and the other being the second braking intake cam lobe
323, mainly located in the expansion stroke of the engine. The
first braking intake cam lobe 322 is to charge the engine cylinder
prior to the first compression release event, and the first
compression release cam lobe 232 to achieve the first stroke
braking. The second braking intake cam lobe 323 is to charge the
engine cylinder prior to the second compression release event, and
the second compression release cam lobe 233 to achieve the second
stroke braking. Thus, the four-stroke engine is able to achieve
two-stroke braking in one cycle, greatly improving the braking
power. Note that the two braking exhaust cam lobes (the first and
second compression-release cam lobes 232 and 233) are much smaller
(lower lift and short duration) than the two braking intake cam
lobes.
Third Embodiment
[0098] FIGS. 8 and 9 are used to illustrate the third embodiment of
the present invention. The present embodiment has two valves 301
and 302 that are biased against the valve seat 320 in the engine
block 500 by the two valve springs 311 and 312. The valve actuator
200 also includes a rocker arm 210 and a valve bridge 400 placed on
the two valves. The rocker arm 210 actuates a single engine valve
(the first valve or the inner valve close to the cams) through a
lash adjusting mechanism (a lash adjusting screw 1102), an e-foot
1142, and a braking bar 116 in the valve bridge 400. The lash
adjusting screw 1102 is fixed on the rocker arm 210 by a lock nut
1052. The rocker arm 210 contains also a lost motion mechanism that
is a hydraulic piston mechanism including a hydraulic piston 160
and a liquid flow control valve 75 (see FIG. 9 for details of the
valve), which happens also to be an auto lash adjusting mechanism.
The hydraulic piston 160 is slidably placed in a piston bore 190. A
hydraulic linkage with a liquid column is formed between piston 160
and rocker arm 210 through the liquid flow control valve 75. The
height 234 of the liquid column is automatically adjusted according
to the gap between the cam 230 and the bridge 400 or the two
valves. The hydraulic piston 160 is engaged with the center of the
valve bridge 400 though an e-foot 114.
[0099] The liquid flow control valve 75 (FIG. 9 for cross section
view) integrated into the rocker arm 210 includes a one-way ball
valve 165, biased upwards by spring 177. The top of the ball valve
165 is actuated by a funnel shaped piston 58 that is biased
downwards by spring 256. When pressured liquid (for example, engine
lube oil) is provided though flow passage 218, oil pressure
overcomes the force of the spring 256 and moves the piston 58
upward. At the same time, oil pressure overcomes the force of the
spring 177 and moves the ball valve 165 downwards. Oil is fed into
the hydraulic passage 216 as well as all the hydraulic passages and
chambers including the piston bore 190 underneath the ball valve
165 to form a hydraulic lock.
[0100] The operation of this embodiment is as follows. The axial
motion of the cam roller 235 on the roller shaft 231 is the same as
the first embodiment. The axial cam roller driver 100 shown in
FIGS. 3 and 4 has a spring 156 or oil pressure that biases the
piston 164 to the bottom surface of piston bore 260 near the side
with the fluid passage 214 (the right side). The piston 164,
through the sliding fork 236, pushes the cam roller 235 to the
first axial position (the right side in FIG. 3), and the cam roller
235 is engaged with the engine power cam 230. Through the roller
shaft 231, the rocker arm 210, the lost motion mechanism that forms
a hydraulic linkage and the valve bridge 400, the motion of the
engine power cam 230 is transmitted to both of the two engine valve
301 and 302 (FIG. 8), generating the valve motion for engine power
operation (see FIG. 5 for the valve lift profile 220 (exhaust) or
321 (intake)). Since the rocker ratio at the e-foot 1142 that opens
the inner valve is smaller than the rocker ration at the e-foot 114
that actuates the valve bridge 400 and both of the two valves 301
(inner valve) and 302 (outer valve), the e-foot 1142 will not be
loaded or transmit any motion to the inner valve 301.
[0101] When it is desired to convert the engine power operation 10
to the engine braking operation 20, the engine brake controller 50
is turned on to provide a driving force to the axial cam roller
driver 100. Fluid, such as engine oil through the fluid passages
211 and 214 in the rocker shaft and rocker arm, flows into piston
bore 260 (FIGS. 3 and 4). The oil pressure overcomes the force of
spring 156 and moves piston 164 in piston bore 260 to the side with
spring 156 (left side), and piston 164 pushes the sliding fork 236
with the cam roller 235 to the second axial position (left side in
FIG. 4). The cam roller 235 is disengaged from the engine power cam
230 and engaged with the engine braking cam 2302. The motion of the
engine power cam 230 is lost.
[0102] At the same time, oil to the liquid flow control valve 75 is
discharged through fluid passage 218. Piston 58 moves downwards
under the action of spring 256 (see FIG. 9) and pushes the one-way
ball valve 165 off its seat. Oil is discharged from the piston bore
190 through the hydraulic passage 216. The liquid column 234 is now
like an air gap and the hydraulic linkage is lost. The motion from
the engine braking cam (cam lobes 232 and 233) is lost at the
e-foot 114 and cannot be transmitted to the two engine valves 301
and 302 through the center of the valve bridge 400. However, due to
the engagement of the rocker arm 210 with the inner valve 301
through the e-foot 1142 and the braking bar 116 in the valve bridge
400, the motion of the engine braking cam 2302 engaged with the cam
roller is transmitted to the inner valve 301 for the engine braking
operation with a single valve actuation, which has much lower
engine braking load.
[0103] In summary, the present embodiment uses an axial cam roller
driver to move the cam roller axially on the roller shaft to switch
its connection from the engine power cam to the engine braking cam.
The motion of the engine power cam is lost. At the same time, the
connection between the rocker arm and the center of the valve
bridge is also cut off by a lost motion mechanism, which converts
the valve actuator 200 from opening two valves to opening one
valve. The motion of the engine braking cam 2302 is transmitted by
the rocker arm to one of the two valves, i.e., the inner valve 301
for the engine braking operation with a single valve actuation.
[0104] The clip ring 176 (or other stopping mechanism) inside the
piston bore 190 is used to limit the stroke of piston 160 as well
as to keep the piston 160 from falling out of the bore (good for
shipping and assembly). An anti-no-follow mechanism is added to
prevent no-follow of the moving parts due to the gap 234 formed by
the lost motion mechanism 250. The anti-no-follow mechanism
includes a spring or an elastic part, such as 117, 118 and 198 in
FIG. 8. The shape, type, installation and location of the springs
or elastic parts can be changed to serve the purpose of keeping the
moving parts, such as the valve bridge 400, from having no-follow.
The height of the gap 234 is determined by the braking cam lobes to
escape (or lose) the motion of the braking cam lobes so that it
won't be transmitted to the valves through the valve bridge
400.
Fourth Embodiment
[0105] FIG. 10 is used to illustrate the fourth embodiment of the
present invention. Instead of a single rocker arm in the third
embodiment, the present embodiment has two rocker arms: a full
rocker arm 210 for opening one valve (the inner valve) 301 and a
half rocker arm 212 for opening both of the two valves (the inner
and outer valves) 301 and 302. The lost motion mechanism 250 is now
a mechanical linkage mechanism that connects the full rocker arm
210 and the half rocker arm 212. The full rocker arm 210 is similar
to that of the first embodiment and has the cam roller 235 on the
roller shaft 231 on its end close to the cams 230 and 2302. The
other end of the full rocker arm 210 is linked to the first valve
(the inner valve) 301 through a braking lash adjusting mechanism,
an e-foot 1142 and a braking bar 116. The half rocker arm 212 and
the full rocker arm 210 are placed rotationally on the common
rocker shaft 205. For example, the full rocker arm 210 could be
placed in the middle while the half rocker arm 212 have a fork
shape and be placed on both sides of the full rocker arm 210. Note
that the half rocker arm 212 is not engaged with cam 230 or 2302.
The end of the half rocker arm 212 is engaged with the center of
the valve bridge 400 through a valve lash adjusting screw 110 and
an e-foot 114. The valve bridge 400 is engaged with the two valves
301 and 302. The adjusting screw 110 is fixed on the half rocker
arm 212 by a lock nut 105. The half rocker arm 212 is also engaged
with the full rocker arm 210 though the lost motion mechanism (the
mechanical linkage mechanism) 250. The mechanical linkage mechanism
250 includes two links 184 and 186 that are linked through a middle
pin 125. The other (left) end of link 184 is engaged with the full
rocker arm 210 through a left pin 122. The other (right) end of
link 186 is engaged with the half rocker arm 212 through a right
pin 128. One end of a returning spring 198 is placed on the
extension part of the right end of link 186. Another end of the
returning spring 198 is located on the half rocker arm 212.
[0106] When it is desired to convert the engine power operation 10
to the engine braking operation 20, the engine brake controller 50
is turned on to provide driving force to the axial cam roller
driver 100. Fluid, such as engine oil through the fluid passage
214, flows into piston bore 260 (FIGS. 3 and 4). The oil pressure
overcomes the force of spring 156 and moves piston 164 in piston
bore 260 to the side with spring 156 (left side), and piston 164
pushes the sliding fork 236 with the cam roller 235 to the second
axial position (left side in FIG. 4). The cam roller 235 is
disengaged from the engine power cam 230 and engaged with the
engine braking cam 2302. The motion of the engine power cam 230 is
lost.
[0107] At the same time, the engine brake controller 50 supplies
oil to the activation piston 162 in FIG. 10. Oil pressure overcomes
the action of spring 198 and pushes upwards the activation piston
162 as well as the center of the mechanical linkage mechanism 250
near the middle pin 125. The half rocker arm 212 rotates
anticlockwise and the e-foot 114 is disconnected from the valve
bridge 400 and the two valves. The motion from the engine braking
cam (cam lobes 232 and 233) is lost at the e-foot 114 and cannot be
transmitted to the two valves 301 and 302 through the center of the
valve bridge 400. However, due to the connection of the full rocker
arm 210 to the inner valve 301 through the e-foot 1142 and the
braking bar 116 in the valve bridge 400, the motion of the engine
braking cam 2302 being engaged with the cam roller 235 is
transmitted to the inner valve 301 for the engine braking operation
with a single valve actuation.
Fifth Embodiment
[0108] FIGS. 11 to 13 are used to describe the fifth embodiment of
the engine braking method of the present invention. Similar to
embodiment four, the present embodiment has also two rocker arms: a
full rocker arm 210 and a half rocker arm 212. However, the full
rocker arm 210 of the present embodiment can be moved axially on
the rocker shaft 205 between a first axial position (FIG. 12) and a
second axial position (FIG. 13). When the full rocker arm 210 is in
the first axial position on the rocker shaft 205, the cam roller
235 on one end of the full rocker arm 210 is engaged with the
engine power cam 230 on the camshaft 225 as shown in FIG. 11. When
the full rocker arm 210 is in the second axial position, the cam
roller 235 is engaged with the engine braking cam 2302 as shown in
FIG. 12. Note that the cam roller 235 on the full rocker arm 210 is
not axially movable in the present embodiment. The other end of the
full rocker arm 210 is engaged with the half rocker arm 212.
[0109] An axial rocker arm driver (not shown here) 100 is used to
move the full rocker arm 210 axially on the rocker shaft 205
through a linkage, such as a hydraulic piston 162 in the full
rocker arm 210. The axial rocker arm driver 100 is placed outside
of the valve actuator of the engine and it can be a hydraulic,
pneumatic, electromagnetic, and mechanical mechanism or a
combination of the above mechanisms. The motion of the axial rocker
arm driver 100 can be synchronized with the motion of the camshaft
225.
Sixth Embodiment
[0110] FIG. 14 is used to describe the sixth embodiment of the
engine braking method of the present invention. The present
embodiment is similar to the fifth embodiment except that the lost
motion mechanism 250 in the third embodiment (FIG. 8) is used here
in the half rocker arm 212. The half rocker arm 212 is also engaged
with the inner valve 301 through a braking bar 116. The operation
of the present embodiment is a combination of the fifth embodiment
(to move the full rocker arm 212 axially on the rocker shaft 205
between a first axial position and a second axial position so that
the cam roller 235 on the full rocker arm 210 will be engaged with
the engine power cam 230 or the engine braking cam 2302) and the
third embodiment (to disengage the half rocker arm 212 from the
center of the valve bridge 400 by a lost motion mechanism 250 so
that the motion from the engine braking cam 2302 can only be
transmitted to the inner valve 301, not to the outer valve
302).
Seventh Embodiment
[0111] FIG. 15 is used to describe the seventh embodiment of the
engine braking method of the present invention. FIG. 15 is similar
to FIG. 1 and the present embodiment is an extension of the
previous embodiments. The engine power cam 230 and the engine
braking cam 2302 are placed on the same camshaft 225 and are
axially movable between a first axial position and a second axial
position on the camshaft 225. However, the cam roller 235 of the
engine is no longer axially movable. The step of engaging the cam
roller 235 with the engine power cam 230 includes using an axial
cam driver 100 to move both the engine power cam 230 and the engine
braking cam 2302 axially on the camshaft 225 to the first axial
position on the camshaft 225, and the step of engaging the cam
roller 235 with the engine braking cam 2302 includes using the
axial cam driver 100 to move both the engine power cam 230 and the
engine braking cam 2302 axially on the camshaft 225 of the engine
to the second axial position on the camshaft 225.
[0112] While the above description contains many specific
embodiments, these embodiments should not be regarded as
limitations on the scope of the present invention, but rather as
specific exemplifications. Many other variations are likely to be
derived from the specific embodiments. For example, the engine
braking method or device described herein can be used not only for
overhead cam engines, but also for pushtube engines; not only for
actuating one engine valve, but also for two engine valves. Also,
the present invention involves different cams, such as the intake
cam, the exhaust cam, and the braking cam, which include cam lobes
that could have different number, size, shape, timing, lift and so
on.
[0113] In addition, the axial cam roller driver, the axial rocker
arm driver and the axial cam driver described herein can not only
be the piston-spring mechanism, but also other mechanism, such as a
hydraulic, a pneumatic, a electromagnetic, and mechanical mechanism
or a combination of the above mechanisms; it can not only be
integrated in the valve actuator (such as with the rocker arm), but
also be placed outside of the valve actuator (such as on the
engine) to move the cam roller, the rocker arm or the cams axially
on the roller shaft, the rocker shaft or the camshaft through a
linkage.
[0114] In addition, the lost motion mechanism integrated into the
valve actuator could have different type, shape, size and location
(such as integrated into a valve bridge), etc.
[0115] Therefore, the scope of the present invention should not be
defined by the above-mentioned specific examples, but by the
appended claims and their legal equivalents.
* * * * *