U.S. patent application number 11/674166 was filed with the patent office on 2008-08-14 for multi-step valve actuation system.
This patent application is currently assigned to GM Global Technology Operations, Inc.. Invention is credited to Burak A. Gecim, Ioan Manole, Madhusudan Raghavan.
Application Number | 20080190386 11/674166 |
Document ID | / |
Family ID | 39643223 |
Filed Date | 2008-08-14 |
United States Patent
Application |
20080190386 |
Kind Code |
A1 |
Raghavan; Madhusudan ; et
al. |
August 14, 2008 |
MULTI-STEP VALVE ACTUATION SYSTEM
Abstract
A multi-step valve actuation system is provided to selectively
open a poppet valve of an internal combustion engine having a
camshaft rotatably supported by a cylinder block. The multi-step
valve actuation system includes a rocker arm operable to
selectively open the poppet valve and a pushrod operable to bias
the rocker arm. A first follower arm is engageable with a first cam
of the camshaft and operates to selectively bias the pushrod. A
lash adjuster is disposed between the first follower arm and the
pushrod. A second follower arm is engageable with a second cam of
the camshaft and selectively latchable with respect to the first
follower arm, while a third follower arm is engageable with a third
cam of the camshaft and selectively latchable with respect to the
first follower arm. An internal combustion engine incorporating the
multi-step valve actuation system of the present invention is also
disclosed.
Inventors: |
Raghavan; Madhusudan; (West
Bloomfield, MI) ; Gecim; Burak A.; (Rochester Hills,
MI) ; Manole; Ioan; (Chesterfield, MI) |
Correspondence
Address: |
GENERAL MOTORS CORPORATION;LEGAL STAFF
MAIL CODE 482-C23-B21, P O BOX 300
DETROIT
MI
48265-3000
US
|
Assignee: |
GM Global Technology Operations,
Inc.
Detroit
MI
|
Family ID: |
39643223 |
Appl. No.: |
11/674166 |
Filed: |
February 13, 2007 |
Current U.S.
Class: |
123/90.1 ;
123/90.45 |
Current CPC
Class: |
Y10T 74/2107 20150115;
F01L 1/18 20130101; F01L 1/146 20130101; F01L 13/0036 20130101;
Y10T 74/20882 20150115 |
Class at
Publication: |
123/90.1 ;
123/90.45 |
International
Class: |
F01L 1/047 20060101
F01L001/047 |
Claims
1. A multi-step valve actuation system to selectively open a poppet
valve of an internal combustion engine having a camshaft rotatably
supported by a cylinder block, the multi-step valve actuation
system comprising: a rocker arm operable to selectively open the
poppet valve; a pushrod operable to bias said rocker arm; a first
follower arm engageable with a first cam of the camshaft and
operable to selectively bias said pushrod; a second follower arm
engageable with a second cam of the camshaft and selectively
latchable with respect to said first follower arm for unitary
movement; a third follower arm engageable with a third cam of the
camshaft and selectively latchable with respect to said first
follower arm for unitary movement; wherein said first and second
cam have respective first and second maximum valve lifts, said
second maximum valve lift being greater in magnitude than said
first maximum valve lift; wherein said third cam has a third
maximum valve lift of greater magnitude than said first and second
maximum valve lifts; wherein the poppet valve is opened to said
third maximum valve lift when said third follower arm is latched to
said first follower arm; wherein the poppet valve is opened to said
first maximum valve lift when said second follower arm is unlatched
from said first follower arm; and wherein the poppet valve is
opened to said second maximum valve lift when said second follower
arm is latched to said first follower arm.
2. (canceled)
3. The multi-step valve actuation system of claim 1, further
comprising a lash adjuster disposed between said first follower arm
and said pushrod.
4. The multi-step valve actuation system of claim 3, wherein said
lash adjuster includes a roller assembly in contact with said first
follower arm.
5. The multi-step valve actuation system of claim 3, wherein said
lash adjuster is selectively collapsible to maintain the poppet
valve in a closed position irrespective of camshaft rotation.
6. The multi-step valve actuation system of claim 1, wherein at
least one of said first and second follower arms rotatably supports
a roller assembly engageable with a respective one of said first
and second cams.
7. The multi-step valve actuation system of claim 1, wherein said
third follower arm rotatably supports a roller assembly engageable
with said third cam.
8. The multi-step valve actuation system of claim 1, wherein the
internal combustion engine includes a cylinder head mounted with
respect to the cylinder block and wherein said rocker arm is
pivotably mounted with respect to the cylinder head and the poppet
valve is at least partially contained within the cylinder head.
9. The multi-step valve actuation system of claim 1, further
comprising a first spring member operable to bias said second
follower arm toward said second cam.
10. The multi-step valve actuation system of claim 9, further
comprising a second spring member operable to bias said third
follower arm toward said third cam.
11. An internal combustion engine comprising: a cylinder block; a
cylinder head mounted with respect to said cylinder block; a
selectively openable poppet valve at least partially disposed
within said cylinder head; a rocker arm pivotably mounted with
respect to said cylinder head and operable to selectively open said
poppet valve; a camshaft having a plurality of cams and rotatably
supported within said cylinder block; a first follower arm
engageable with a first cam of said plurality of cams; a second
follower arm engageable with a second cam of said plurality of cams
and selectively latchable with respect to said first follower arm;
a third follower arm engageable with a third cam of said plurality
of cams and selectively latchable with respect to one of said first
and second follower arms; wherein said first and second cam have
respective first and second maximum valve lifts, said second
maximum valve lift being greater in magnitude than said first
maximum valve lift; wherein said third cam has a third maximum
valve lift of greater magnitude than said first and second maximum
valve lifts; wherein said selectively openable poppet valve is
opened to said third maximum valve lift when said third follower
arm is latched to said one of said first and second follower arms;
wherein said selectively openable poppet valve is opened to said
first maximum valve lift when said second follower arm is unlatched
from said first follower arm; and wherein said selectively openable
poppet valve is opened to said second maximum valve lift when said
second follower arm is latched to said first follower arm.
12. (canceled)
13. The internal combustion engine of claim 11, further comprising:
a lash adjuster disposed between said first follower arm and said
pushrod; and wherein said lash adjuster is one of a selectively
collapsible and non-collapsible type.
14. The internal combustion engine of claim 13, wherein said lash
adjuster includes a roller assembly in contact with said first
follower arm.
15. The internal combustion engine of claim 11, wherein at least
one of said first and second follower arms rotatably supports a
roller assembly engageable with a respective one of said first and
second cams.
16. The internal combustion engine of claim 11, wherein said third
follower arm rotatably supports a roller assembly engageable with
said third cam.
17. A multi-step valve actuation system to selectively open a
poppet valve of an internal combustion engine having a camshaft
rotatably supported by a cylinder block, the multi-step valve
actuation system comprising: a rocker arm operable to selectively
open the poppet valve; a pushrod operable to bias said rocker arm;
a first follower arm engageable with a first cam of the camshaft
and operable to selectively bias said pushrod; a lash adjuster
disposed between said first follower arm and said pushrod; a second
follower arm engageable with a second cam of the camshaft and
selectively latchable with respect to said first follower arm; a
third follower arm engageable with a third cam of the camshaft and
selectively latchable with respect to said first follower arm;
wherein said first, second, and third cam have respective first,
second, and third maximum valve lifts; wherein said third maximum
valve lift is greater in magnitude than said second maximum valve
lift and said second maximum valve lift is greater in magnitude
than said first maximum valve lift; wherein the poppet valve is
opened to said first maximum valve lift when said second follower
arm is unlatched from said first follower arm; wherein the poppet
valve is opened to said second maximum valve lift when said second
follower arm is latched to said first follower arm; and wherein the
poppet valve is opened to said third maximum valve lift when said
third follower arm is latched to said first follower arm.
18. The multi-step valve actuation system of claim 17, wherein said
lash adjuster is selectively collapsible.
19. The multi-step valve actuation system of claim 17, wherein at
least one of said first, second, and third follower arms include a
roller assembly engageable with a respective one of said first,
second, and third cams.
20. The multi-step valve actuation system of claim 17, further
comprising first and second spring members operable to bias a
respective one of said second and third follower arms toward said
respective second and third cams.
Description
TECHNICAL FIELD
[0001] The present invention relates to a multi-step valve
actuation system for an internal combustion engine having an
overhead valve, camshaft-in-block configuration.
BACKGROUND OF THE INVENTION
[0002] Recent advances in internal combustion engine operating
strategies have led to the development of two-step or multi-step
valve actuation systems. These systems allow two or more distinct
valve lift profiles, thereby allowing a poppet valve of the
internal combustion engine to be opened in accordance with one
valve lift profile having a first predetermined maximum lift, when
operating in one engine speed and load condition and to be opened
in accordance with another valve lift profile having a second
predetermined maximum lift, when operating in another engine speed
and load condition. This two-step characteristic is usually
facilitated in overhead camshaft internal combustion engines
through the use of a switchable follower disposed between the
camshaft, which is rotatably mounted with respect to a cylinder
head, and the poppet valve. The increased amount of space required
for the packaging of the multi-step valve actuation system has
prevented its use within overhead valve, camshaft-in-block internal
combustion engines where space is typically limited.
SUMMARY OF THE INVENTION
[0003] A multi-step valve actuation system is provided to
selectively open a poppet valve of an internal combustion engine
having a camshaft rotatably supported by a cylinder block. The
multi-step valve actuation system includes a pivotably mounted
rocker arm operable to selectively open the poppet valve and a
pushrod operable to bias the rocker arm. A first follower arm is
engageable with a first cam of the camshaft and operable to
selectively bias the pushrod. Similarly, a second follower arm is
engageable with a second cam of the camshaft and is selectively
latchable with respect to the first follower arm for unitary
movement. The first and second cam have respective first and second
maximum valve lifts, such that the second maximum valve lift is
greater in magnitude than the first maximum valve lift.
[0004] In operation, the poppet valve is opened to the first
maximum valve lift when the second follower arm is unlatched from
the first follower arm. Alternately, the poppet valve is opened to
the second maximum valve lift when the second follower arm is
latched to the first follower arm.
[0005] In one embodiment, a third follower arm is engageable with a
third cam of the camshaft and is selectively latchable with respect
to the first follower arm for unitary movement. Additionally, the
third cam has a third maximum valve lift of greater magnitude than
the first and second maximum valve lifts. In operation, the poppet
valve is opened to the third maximum valve lift when the third
follower arm is latched to the first follower arm.
[0006] A lash adjuster may be disposed between the first follower
arm and the pushrod to account for clearances within the multi-step
valve actuation system. The lash adjuster may be selectively
collapsible to enable deactivation of the poppet valve. Each of the
first, second, and third follower arms may rotatably support
friction reducing roller assemblies. An internal combustion engine
incorporating the multi-step valve actuation system is also
disclosed.
[0007] The above features and advantages and other features and
advantages of the present invention are readily apparent from the
following detailed description of the best modes for carrying out
the invention when taken in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a perspective view of a portion of an internal
combustion engine incorporating a multi-step valve actuation system
of the present invention; and
[0009] FIG. 2 is a perspective view of a portion of the multi-step
valve actuation system of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0010] Referring to the drawings wherein like reference numbers
correspond to like or similar components throughout the several
figures, there is shown in FIG. 1 an internal combustion engine,
generally indicated at 10. The internal combustion engine 10
includes a cylinder block 12 having a first bank of cylinders 14
and a second bank of cylinders 16. A first cylinder head 18, shown
in phantom, and a second cylinder head 20 are mounted to a
respective one of the first and second bank of cylinders 14 and 16.
Only a portion of the first and second cylinder heads 18 and 20 are
shown in FIG. 1. Those skilled in the art will realize that in a
complete internal combustion engine 10, the first and second
cylinder heads 18 and 20 will span substantially the entirety of
the respective first and second cylinder banks 14 and 16. The first
and second bank of cylinders 14 and 16 are arranged in a generally
V-shaped configuration, thereby defining a valley 22. Therefore,
the internal combustion engine 10 can be generally regarded as a
V-type engine.
[0011] A selectively openable poppet valve 24 is at least partially
contained within each of the first and second cylinder heads 18 and
20 and is operable to allow the selective introduction of intake
air into the internal combustion engine 10. As such, the poppet
valves 24 may be considered intake valves. Additionally, a
selectively openable poppet valve 26 is at least partially
contained within each of the first and second cylinder heads 18 and
20 and is operable to allow the selective exhaust of products of
combustion from the internal combustion engine 10. As such, the
poppet valves 26 may be considered exhaust valves. The poppet
valves 24 and 26 are biased in a closed position by valve springs
28 and 30, respectively. With the arrangement of the poppet valves
24 and 26 discussed hereinabove, the internal combustion engine 10
may be characterized as an overhead valve engine.
[0012] The internal combustion engine includes a multi-step valve
actuation system 31. The multi-step valve actuation system 31
includes rocker arms 32 and 34, pushrods 36 and 38, and camshaft
40. The camshaft 40 is rotatably supported within the cylinder
block 12 by camshaft bearings 42, shown in FIG. 2; therefore, the
internal combustion engine 10 may be further characterized as
having a camshaft-in-block configuration. The rotation of the
camshaft 40 forces or urges the pushrods 36 and 38 to bias the
respective rocker arms 32 and 34 to effect the movement of the
respective poppet valves 24 and 26 from the closed position to an
open position. The rocker arms 32 and 34 are pivotably mounted with
respect to the first and second cylinder heads 18 and 20. The
construction and operation of the multi-step valve actuation system
31 will be discussed in greater detail with reference to FIG. 2.
The hydraulic circuitry employed for the operation of the
multi-step valve actuation system 31 has been removed from FIG. 1
for clarity.
[0013] Referring to FIG. 2, and with continued reference to FIG. 1,
there is shown a portion of the multi-step valve actuation system
31 of FIG. 1 further illustrating various aspects of the present
invention. The camshaft 40 includes a plurality of cams 44
including first cams 46, second cams 48, and third cams 50
associated with the operation of the poppet valves 24, i.e. the
intake valves, of the internal combustion engine 10. Each of the
first, second, and third cams 46, 48, and 50 have a predetermined
valve lift profile with a predetermined maximum valve lift
determined by the respective first, second, and third lobe portions
52, 54, and 56. The first, second, and third cams 46, 48, and 50
further include respective first, second, and third base circle
portions 58, 60, and 62. In the preferred embodiment, the
predetermined maximum valve lift of the third cam 50 is greater
than that of the second cam 48 which, in turn, has a greater
predetermined maximum valve lift than that of the first cam 46.
[0014] Additionally, cams 64 are associated with the operation of
the poppet valves 26, i.e. the exhaust valves, of the internal
combustion engine 10. The cams 64 have a predetermined valve lift
profile with a predetermined maximum valve lift determined by the
lobe portion 66 of each of the cams 64, while a base circle portion
68 is also provided on each of the cams 64.
[0015] First, second, and third follower arms 70, 72, and 74 are
engageable with the respective first, second, and third cams 46,
48, and 50. Each of the first, second, and third follower arms 70,
72, and 74 rotatably supports a roller assembly 76. The roller
assemblies 76 operate to reduce the friction between the first,
second, and third follower arms 70, 72, and 74 and the respective
first, second, and third cams 46, 48, and 50 during rotation of the
camshaft 40. Those skilled in the art will recognize that the
roller assemblies 76 may be omitted, at the expense of greater
frictional losses, while remaining within the scope of that which
is claimed. The second and third follower arms 72 and 74 are each
disposed on either side of the first follower arm 70 and are
selectively latchable to the first follower arm 70 for unitary
movement therewith. Those skilled in the art will recognize various
methods of latching the second and third follower arms 72 and 74
with respect to the first follower arm 70, including, for example,
a hydraulically actuated pin or a mechanically actuated pin. The
latching of the second and third follower arms 72 and 74 to the
first follower arm 70 is preferably performed when the first,
second, and third follower arm 70, 72, and 74 are in contact with
the base circle portions 58, 60, and 62 of the respective first,
second, and third cams 46, 48, and 50.
[0016] Follower arms 78 are engageable with the cams 64 and include
roller assemblies 80, one of which is shown in FIG. 2, which are
operable to reduce friction between the follower arms 78 and the
cams 64 as the camshaft 40 rotates. As with the roller assemblies
76, those skilled in the art will recognize that the roller
assemblies 80 may be omitted, at the expense of greater frictional
losses, while remaining within the scope of that which is
claimed.
[0017] The follower arms 70, 72, 74, and 78 are pivotably mounted
with respect to the cylinder block, shown in FIG. 1, by a shaft 82,
shown with dashed lines in FIG. 2. The shaft 82 is spaced from the
camshaft 40 and mounted substantially within the valley 22 of the
internal combustion engine 10. By mounting the follower arms 70,
72, 74, and 78 within the valley 22 of the internal combustion
engine 10, the multi-step valve actuation system 31 may be
efficiently packaged within a space that would otherwise have been
left empty in traditional camshaft-in-block engine designs.
Additionally, by packaging the follower arms 70, 72, 74, and 78
within the valley 22, the design changes required to the first and
second cylinder heads 18 and 20 to incorporate the multi-step valve
actuation system 31 are minimized.
[0018] A hydraulic lash adjuster 84 is disposed between the first
follower arm 70 and the pushrod 36. Similarly, a hydraulic lash
adjuster 86 is disposed between the follower arm 78 and the pushrod
38. The hydraulic lash adjusters 84 and 86 are operable to account
for the lash or clearance that may be present within the multi-step
valve actuation system 31 during operation of the internal
combustion engine 10. Preferably, each of the lash adjusters 84 and
86 each include a roller assembly 88 operable to reduce friction
within the multi-step valve actuation system 3 1. Additionally, the
lash adjusters 84 and 86 may be selectively collapsible to allow
the respective poppet valves 24 and 26 to remain in the closed
position irrespective of the rotation of the camshaft 40. This type
of operation is especially suited for so-called Active Fuel
Management or Displacement on Demand modes of engine operation
where at least one of the cylinders of the internal combustion
engine 10 is deactivated by maintaining the poppet valves 24 and 26
in the closed position. By maintaining the poppet valves 24 and 26
in the closed position, the pumping losses of the internal
combustion engine 10 are decreased, thereby increasing operating
efficiency. This mode of operation is beneficial during certain
engine operating conditions, such as low load engine operation.
[0019] A plunger 90 is biased by a spring 92 to urge the second
follower arm toward the second cam 48. Similarly, a plunger 94 is
biased by a spring 96 to urge the third follower arm toward the
third cam 50. The plungers 90 and 94 and springs 92 and 96
cooperate to keep the respective second and third follower arms 72
and 74 in contact with the respective second and third cams 48 and
50 during modes of engine operation when the second follower arm 72
and/or third follower arm 74 are unlatched from the first follower
arm 70.
[0020] The multi-step valve actuation system 31 of the present
invention provides three valve lift profiles to the poppet valve
24. In operation, the internal combustion engine 10 may operate in
a low lift mode of operation where the poppet valve 24 is
selectively opened in accordance with a predetermined valve lift
profile having a predetermined maximum valve lift. This mode of
operation is accomplished by unlatching the second and third
follower arms 72 and 74 from the first follower arm 70 thereby
allowing the first follower arm 70 to follow the profile of the
first cam 46 and bias the pushrod 36 in accordance with the valve
lift profile of the first cam 46. The plungers 90 and 94 and
springs 92 and 96 cooperate to keep the respective second and third
follower arms 72 and 74 in contact with the respective second and
third cam 48 and 50. Those skilled in the art will recognize that
the first cam 46 may be formed such that it provides zero lift to
the poppet valve 24 thereby allowing the deactivation of the
associated cylinder of the internal combustion engine 10.
[0021] When operating in the medium lift mode of operation, the
second follower arm 72 is latched to the first follower arm 70
providing unitary movement therewith. The second follower arm 72
will follow the valve lift profile of the second cam 48 and cause
the first follower arm 70 to bias the pushrod 36 in accordance with
that profile. The first follower arm 70 no longer follows the
profile of the first cam 46 in the medium lift mode of operation.
The plunger 94 and spring 96 cooperate to keep the third follower
arm 74 in contact with the third cam 50.
[0022] When operating in the high lift mode of operation, the third
follower arm 74 is latched to the first follower arm 70 providing
unitary movement therewith. The third follower arm 74 will follow
the valve lift profile of the third cam 50 and cause the first
follower arm 70 to bias the pushrod 36 in accordance with that
profile. The first follower arm 70 no longer follows the profile of
the first cam 46 and in the high lift mode of operation. The
plunger 90 and spring 92 cooperate to keep the second follower arm
72 in contact with the second cam 48. Alternately, both the second
and the third follower arm 72 and 74 may be latched to the first
follower arm 70 during the high lift mode of operation.
[0023] Although the multiple lift functionality of the multi-step
valve actuation system 31 has been described herein above with
reference to the selective opening of the poppet valves 24, i.e.
the intake valves, those skilled in the art will recognize that the
multiple lift functionality may be applied to the poppet valves 26,
i.e. the exhaust valves, should the operational strategies of the
internal combustion engine 10 require such functionality.
Additionally, a multi-step valve actuation system 31 having two
lift functionality may be provided by eliminating the third
follower arm 74 and the third cam 50. In the alternative, a
multi-step valve actuation system 31 having greater than three
distinct valve lifts may be provided by increasing the number of
follower arms and respective cams.
[0024] The multi-step valve actuation system 31 may include a
camshaft phaser, not shown, operable to adjust the timing of the
camshaft 40, thereby providing a greater range of valve actuation
functionality. The internal combustion engine 10 incorporating the
multi-step valve actuation system 31 of the present invention is
especially suited for use with an electrically variable hybrid
transmission, or EVT, as the EVT may employ the variable valve lift
and/or valve deactivation functionality provided by the multi-step
valve actuation system 31 to optimize fuel economy. Further the
multi-step valve actuation system 31 of the present invention may
facilitate a Homogeneous Charge Compression Ignition, or HCCI, mode
of operation for the internal combustion engine 10. When operating
in the HCCI mode of operation, the intake valve may require
multiple valve lift strategies and possible valve deactivation.
Additionally, by providing the exhaust valve with valve reopening
capabilities, such as is possible with a two lobe cam, selective
re-breathing of products of combustion is possible thereby
stabilizing the HCCI combustion process.
[0025] While the best modes for carrying out the invention have
been described in detail, those familiar with the art to which this
invention relates will recognize various alternative designs and
embodiments for practicing the invention within the scope of the
appended claims.
* * * * *