U.S. patent application number 12/877550 was filed with the patent office on 2012-03-08 for engine including variable valve lift mechanism.
This patent application is currently assigned to GM GLOBAL TECHNOLOGY OPERATIONS, INC.. Invention is credited to CLYDE A. BULLOCH.
Application Number | 20120055426 12/877550 |
Document ID | / |
Family ID | 45769728 |
Filed Date | 2012-03-08 |
United States Patent
Application |
20120055426 |
Kind Code |
A1 |
BULLOCH; CLYDE A. |
March 8, 2012 |
ENGINE INCLUDING VARIABLE VALVE LIFT MECHANISM
Abstract
An engine assembly may include an engine structure, an engine
valve, a valve lift mechanism, and first and second camshafts. The
engine structure may define a combustion chamber and a port in
communication with the combustion chamber. The engine valve may be
supported by the engine structure and displaceable between an open
position where the port is in communication with the combustion
chamber and a closed position to isolate the port from
communication with the combustion chamber. The valve lift mechanism
may be engaged with the engine valve. The first camshaft may be
rotationally supported by the engine structure and may include a
first cam lobe engaged with the valve lift mechanism. The second
camshaft may be rotationally supported by the engine structure and
may include a second cam lobe engaged with the valve lift
mechanism.
Inventors: |
BULLOCH; CLYDE A.;
(HARTLAND, MI) |
Assignee: |
GM GLOBAL TECHNOLOGY OPERATIONS,
INC.
DETROIT
MI
|
Family ID: |
45769728 |
Appl. No.: |
12/877550 |
Filed: |
September 8, 2010 |
Current U.S.
Class: |
123/90.15 |
Current CPC
Class: |
Y02T 10/18 20130101;
F02D 13/0257 20130101; F02D 13/0261 20130101; F01L 13/0047
20130101; Y02T 10/12 20130101 |
Class at
Publication: |
123/90.15 |
International
Class: |
F01L 1/34 20060101
F01L001/34 |
Claims
1. An engine assembly comprising: an engine structure defining a
combustion chamber and a port in communication with the combustion
chamber; an engine valve supported by the engine structure and
displaceable between an open position where the port is in
communication with the combustion chamber and a closed position to
isolate the port from communication with the combustion chamber; a
valve lift mechanism engaged with the engine valve; a first
camshaft rotationally supported by the engine structure and
including a first cam lobe engaged with the valve lift mechanism;
and a second camshaft rotationally supported by the engine
structure and including a second cam lobe engaged with the valve
lift mechanism.
2. The engine assembly of claim 1, further comprising a first cam
phaser coupled to the first camshaft and operable to rotate the
first camshaft between first and second positions relative to the
second camshaft to vary a lift profile of the engine valve.
3. The engine assembly of claim 2, wherein a first peak of the
first cam lobe is engaged with the valve lift mechanism when a
second peak of the second cam lobe is engaged with valve lift
mechanism when the first camshaft is in the first position.
4. The engine assembly of claim 3, wherein the first peak of the
first cam lobe is rotationally offset from the valve lift mechanism
when the second peak of the second cam lobe is engaged with valve
lift mechanism when the first camshaft is in the second
position.
5. The engine assembly of claim 2, further comprising a second cam
phaser coupled to the second camshaft and operable to rotate the
second camshaft relative to the first camshaft.
6. The engine assembly of claim 5, wherein the lift profile defines
a maximum valve lift height of the engine valve when the first cam
lobe is in a fully retarded position and the second cam lobe is in
a fully advanced position.
7. The engine assembly of claim 6, wherein the lift profile defines
a maximum retard condition for opening of the engine valve when the
first cam lobe is in a fully retarded position and the second cam
lobe is in a fully retarded position.
8. The engine assembly of claim 6, wherein the lift profile defines
a maximum advanced condition for opening of the engine valve when
the first cam lobe is in a fully advanced position and the second
cam lobe is in a fully advanced position.
9. The engine assembly of claim 6, wherein the lift profile defines
a maximum opening duration of the engine valve when the first cam
lobe is in a fully advanced position and the second cam lobe is in
a fully retarded position.
10. The engine assembly of claim 2, wherein the valve lift
mechanism includes a pivot arm defining a first end engaged with
the first cam lobe, a second end engaged with the second cam lobe
and a pivot located between the first and second ends, the valve
lift profile being varied by the first and second cam lobes
adjusting a rotational orientation of the valve lift mechanism
about the pivot.
11. A method comprising: displacing an engine valve from a closed
position to an open position at a first valve lift profile to
provide communication between an engine port and an engine
combustion chamber, the displacing including a first cam lobe on a
first camshaft and a second cam lobe on a second camshaft engaging
a valve lift mechanism engaged with the engine valve; rotating the
first camshaft relative to the second camshaft; and displacing the
engine valve from the closed position to the open position at a
second valve lift profile different than the first valve lift
profile after the rotating via engagement between the first and
second cam lobes and the valve lift mechanism.
12. The method of claim 11, wherein the rotating includes actuating
a cam phaser coupled to the first camshaft.
13. The method of claim 12, wherein the first valve lift profile
includes a peak of the first cam lobe being engaged with the valve
lift mechanism when a peak of the second cam lobe is engaged with
the valve lift mechanism.
14. The method of claim 13, wherein the second valve lift profile
includes the peak of the first cam lobe being rotationally offset
from the valve lift mechanism when the peak of the second cam lobe
is engaged with the valve lift mechanism.
15. The method of claim 12, further comprising rotating the second
camshaft relative to the first camshaft via a second cam phaser
coupled to the second camshaft.
16. The method of claim 15, wherein the engine valve is displaced
to a maximum valve lift height when the first cam lobe is in a
fully retarded position and the second cam lobe is in a fully
advanced position.
17. The method of claim 16, wherein a maximum retard condition for
displacement of the engine valve is defined when the first cam lobe
is in a fully retarded position and the second cam lobe is in a
fully retarded position.
18. The method of claim 16, wherein a maximum advanced condition
for displacement of the engine valve is defined when the first cam
lobe is in a fully advanced position and the second cam lobe is in
a fully advanced position.
19. The method of claim 16, wherein a maximum opening duration of
the engine valve is defined when the first cam lobe is in a fully
advanced position and the second cam lobe is in a fully retarded
position.
20. The method of claim 11, wherein the displacing the engine valve
from the closed position to the open position at the second valve
lift profile includes the first cam lobe being engaged with a first
end of the valve lift mechanism and the second cam lobe being
engaged with a second end of the valve lift mechanism, the
engagement between the first and second cam lobes and the valve
lift mechanism rotationally displacing the valve lift mechanism
about a pivot located between the first and second ends of the
valve lift mechanism to provide the second valve lift profile.
Description
FIELD
[0001] The present disclosure relates to engine valvetrain
assemblies.
BACKGROUND
[0002] This section provides background information related to the
present disclosure which is not necessarily prior art.
[0003] Engines typically include a camshaft to actuate intake
and/or exhaust valves. The camshaft may include cam lobes engaged
with a valve lift mechanism to open and the close the valves. The
timing of valve opening and/or closing may be varied by a cam
phaser coupled to the camshaft.
SUMMARY
[0004] An engine assembly may include an engine structure, an
engine valve, a valve lift mechanism, and first and second
camshafts. The engine structure may define a combustion chamber and
a port in communication with the combustion chamber. The engine
valve may be supported by the engine structure and displaceable
between an open position where the port is in communication with
the combustion chamber and a closed position to isolate the port
from communication with the combustion chamber. The valve lift
mechanism may be engaged with the engine valve. The first camshaft
may be rotationally supported by the engine structure and may
include a first cam lobe engaged with the valve lift mechanism. The
second camshaft may be rotationally supported by the engine
structure and may include a second cam lobe engaged with the valve
lift mechanism.
[0005] A method of actuating an engine valve may include displacing
the engine valve from a closed position to an open position at a
first valve lift profile to provide communication between an engine
port and an engine combustion chamber. The displacing may include a
first cam lobe on a first camshaft and a second cam lobe on a
second camshaft engaging a valve lift mechanism engaged with the
engine valve. The first camshaft may be rotated relative to the
second camshaft. The engine valve may be displaced from the closed
position to the open position at a second valve lift profile
different than the first valve lift profile after the first
camshaft is rotated relative to the second camshaft via engagement
between the first and second cam lobes and the valve lift
mechanism.
[0006] Further areas of applicability will become apparent from the
description provided herein. The description and specific examples
in this summary are intended for purposes of illustration only and
are not intended to limit the scope of the present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The drawings described herein are for illustrative purposes
only and are not intended to limit the scope of the present
disclosure in any way.
[0008] FIG. 1 is a schematic fragmentary section view of an engine
assembly including first and second camshafts engaged with a valve
lift mechanism in a first position according to the present
disclosure;
[0009] FIG. 2 is a schematic illustration of the first and second
camshafts and the valve lift mechanism shown FIG. 1 in a second
position;
[0010] FIG. 3 is a schematic illustration of the first and second
camshafts and the valve lift mechanism shown FIG. 1 in a third
position;
[0011] FIG. 4 is a schematic illustration of the first and second
camshafts and the valve lift mechanism shown FIG. 1 in a fourth
position; and
[0012] FIG. 5 is a graphical illustration of the range of lift
profiles provided by the present disclosure.
[0013] Corresponding reference numerals indicate corresponding
parts throughout the several views of the drawings.
DETAILED DESCRIPTION
[0014] Examples of the present disclosure will now be described
more fully with reference to the accompanying drawings. The
following description is merely exemplary in nature and is not
intended to limit the present disclosure, application, or uses.
[0015] Example embodiments are provided so that this disclosure
will be thorough, and will fully convey the scope to those who are
skilled in the art. Numerous specific details are set forth such as
examples of specific components, devices, and methods, to provide a
thorough understanding of embodiments of the present disclosure. It
will be apparent to those skilled in the art that specific details
need not be employed, that example embodiments may be embodied in
many different forms and that neither should be construed to limit
the scope of the disclosure. In some example embodiments,
well-known processes, well-known device structures, and well-known
technologies are not described in detail.
[0016] When an element or layer is referred to as being "on,"
"engaged to," "connected to" or "coupled to" another element or
layer, it may be directly on, engaged, connected or coupled to the
other element or layer, or intervening elements or layers may be
present. In contrast, when an element is referred to as being
"directly on," "directly engaged to," "directly connected to" or
"directly coupled to" another element or layer, there may be no
intervening elements or layers present. Other words used to
describe the relationship between elements should be interpreted in
a like fashion (e.g., "between" versus "directly between,"
"adjacent" versus "directly adjacent," etc.). As used herein, the
term "and/or" includes any and all combinations of one or more of
the associated listed items.
[0017] Although the terms first, second, third, etc. may be used
herein to describe various elements, components, regions, layers
and/or sections, these elements, components, regions, layers and/or
sections should not be limited by these terms. These terms may be
only used to distinguish one element, component, region, layer or
section from another region, layer or section. Terms such as
"first," "second," and other numerical terms when used herein do
not imply a sequence or order unless clearly indicated by the
context. Thus, a first element, component, region, layer or section
discussed below could be termed a second element, component,
region, layer or section without departing from the teachings of
the example embodiments.
[0018] An exemplary engine assembly 10 is schematically illustrated
in FIG. 1 and may include an engine structure 12, first and second
camshafts 14, 16 rotationally supported on the engine structure 12,
a first cam phaser 18 coupled to the first camshaft 14, a second
cam phaser 20 coupled to the second camshaft 16, an engine valve 22
and a valve lift mechanism 24 engaged with the first and second
camshafts 14, 16 and the engine valve 22. In the present
non-limiting example, the engine assembly 10 is illustrated as an
overhead camshaft engine where the engine structure 12 is a
cylinder head. However, it is understood that the present
disclosure is not limited to overhead camshaft arrangements and
applies equally to a variety of other engine configurations as
well, such as cam-in-block (or pushrod) engines. It is also
understood that the engine valve 22 may be an exhaust valve or an
intake valve.
[0019] The first camshaft 14 may include a first cam lobe 26
engaged with the valve lift mechanism 24 and the second camshaft 16
may include a second cam lobe 28 engaged with the valve lift
mechanism 24. The first cam lobe 26 may include a first base circle
region 30 and a first peak region 32 defining a first peak 34.
Similarly, the second cam lobe 28 may include a second base circle
region 36 and a second peak region 38 defining a second peak
40.
[0020] The first and second camshafts 14, 16 may be laterally
offset from one another (non-coaxial) and may extend generally
parallel to one another. The first and second cam lobes 26, 28 may
be laterally offset from one another and longitudinally aligned to
one another. More specifically, the second cam lobe 28 may be
radially spaced from an outer periphery of the first cam lobe
26.
[0021] The valve lift mechanism 24 may include a pivot arm 42
defining a first end 44 engaged with the first cam lobe 26, a
second end 46 engaged with the second cam lobe 28 and a pivot 50
located between the first and second ends 44, 46. The valve lift
mechanism 24 may define a body extending laterally between the
first and second ends 44, 46. Therefore, the first and second ends
44, 46 may form lateral ends of the valve lift mechanism 24. The
first end 44 may include a first roller member 52 engaged with the
first cam lobe 26 and the second end 46 may include a second roller
member 54 engaged with the second cam lobe 28. The engine valve 22
may be pivotally coupled to the valve lift mechanism 24 at the
pivot 50 and may be displaced from a closed position (not shown) to
an open position (FIG. 1) against the force of a valve spring 58 by
the first and second cam lobes 26, 28 to provide communication
between an engine port 60 defined in the engine structure 12 and an
engine combustion chamber 62.
[0022] FIGS. 1-4 illustrate four lift conditions (lift profiles)
provided by the engine valve 22 and FIG. 5 graphically illustrates
each of the lift profiles. In FIG. 5, the Y-axis illustrates valve
lift and the X-axis illustrates crank angle. The lift duration and
height of the engine valve 22 may be controlled by advancing and
retarding the first and second cam lobes 26, 28 via the first and
second cam phasers 18, 20. The first and second camshafts 14, 16,
and therefore first and second cam lobes 26, 28, may be rotated
relative to one another. More specifically, the first camshaft 14
may be rotated from a first position (fully retarded) to a second
position (fully advanced) in a first rotational direction (R1) of
the first camshaft 14. The first camshaft 14 may additionally be
displaced to any position between the first and second
positions.
[0023] Similarly, the second camshaft 16 may be rotated from a
third position (fully retarded) to a fourth position (fully
advanced) in a second rotational direction (R2) of the second
camshaft 16. The second camshaft 16 may additionally be displaced
to any position between the third and fourth positions. While the
first and second rotational directions (R1, R2) are illustrated as
being opposite one another, it is understood that the first and
second camshafts 14, 16 may alternatively rotate in the same
direction.
[0024] FIG. 1 illustrates a maximum valve lift height condition,
graphically illustrated by curve (C1) in FIG. 5. The maximum valve
lift height condition may correspond to a minimum valve lift
duration condition. The first peak 34 of the first cam lobe 26 may
be engaged with the valve lift mechanism 24 when the second peak 40
of the second cam lobe 28 is engaged with valve lift mechanism 24
when the first camshaft 14 is in the first position and the second
camshaft 16 is in the fourth position. As discussed above, the
first position of the first camshaft 14 may provide a fully
retarded position for the first cam lobe 26 and the fourth position
of the second camshaft 16 may provide a fully advanced position for
the second cam lobe 28. Therefore, the lift profile (curve (C1))
may define the maximum valve lift height of the engine valve 22
when the first cam lobe 26 is in the fully retarded position and
the second cam lobe 28 is in the fully advanced position.
[0025] FIG. 2 illustrates a maximum advanced condition for engine
valve opening, graphically illustrated by curve (C2) in FIG. 5.
During the maximum advanced condition, the first camshaft 14 may be
in the second position and the second camshaft 16 may be in the
third position. Therefore, the lift profile (curve (C2)) may define
a maximum advanced condition for opening of the engine valve 22
when the first cam lobe 26 is in a fully advanced position and the
second cam lobe 28 is in a fully advanced position. The second peak
40 of the second cam lobe 28 may be rotationally offset from the
valve lift mechanism 24 when the first peak 34 of the first cam
lobe 26 is engaged with the valve lift mechanism 24 when the first
camshaft 14 is in the first position and the second camshaft 16 is
in the third position. The maximum advanced condition may generally
provide an earlier valve opening event relative to nominal
operating conditions. The peak engine valve lift during the maximum
advanced condition may occur earlier than a peak engine valve lift
occurring during the maximum valve lift height condition discussed
above.
[0026] FIG. 3 illustrates a maximum retarded condition for engine
valve opening, graphically illustrated by curve (C3) in FIG. 5.
During the maximum retarded condition, the first camshaft 14 may be
in the second position and the second camshaft 16 may be in the
third position. Therefore, the lift profile (curve (C3)) may define
a maximum retarded condition for opening the engine valve 22 when
the first cam lobe 26 is in the fully retarded position and the
second cam lobe 28 is in the fully retarded position. The first
peak 34 of the first cam lobe 26 may be rotationally offset from
the valve lift mechanism 24 when the second peak 40 of the second
cam lobe 28 is engaged with the valve lift mechanism 24 when the
first camshaft 14 is in the second position and the second camshaft
16 is in the fourth position. The maximum retarded condition may
generally provide delayed valve opening event relative to nominal
operating conditions. The peak engine valve lift during the maximum
retarded condition may occur later than a peak engine valve lift
occurring during the maximum valve lift height condition discussed
above.
[0027] FIG. 4 illustrates a maximum valve lift duration condition,
graphically illustrated by curve (C4) in FIG. 5 (minimum height).
The maximum valve lift duration condition may correspond to a
minimum valve lift height condition. The first peak 34 of the first
cam lobe 26 and the second peak 40 of the second cam lobe 28 may be
rotationally out of phase with one another during the maximum valve
lift duration condition. More specifically, the first camshaft 14
may be in the second position and the second camshaft 16 may be in
the third position during the maximum valve lift duration
condition. As discussed above, the second position of the first
camshaft 14 may provide a fully advanced position for the first cam
lobe 26 and the third position of the second camshaft 16 may
provide a fully retarded position for the second cam lobe 28.
Therefore, the lift profile (curve (C4)) may define the maximum
opening duration of the engine valve 22 when the first cam lobe 26
is in the fully advanced position and the second cam lobe 28 is in
the fully retarded position.
[0028] The valve lift mechanism 24 provides for variation of engine
valve lift height, duration and timing of engine valve opening by
adjusting the phase of the first and second cam lobes 26, 28
relative to one another without the use of a hydraulically actuated
lift mechanism. During operation, the engine valve 22 may be
displaced from the closed position (not shown) to the open position
(FIG. 1) at a first valve lift profile to provide communication
between the engine port 60 and the engine combustion chamber 62.
The displacing may include the first cam lobe 26 on the first
camshaft 14 and the second cam lobe 28 on the second camshaft 16
engaging the valve lift mechanism 24 engaged with the engine valve
22.
[0029] The engine valve 22 may be displaced from the closed
position to the open position at a second valve lift profile
different than the first valve lift profile after rotating the
first camshaft 14 relative to the second camshaft 16 via engagement
between the first and second cam lobes 26, 28 and the valve lift
mechanism 24. Rotating the first camshaft 14 relative to the second
camshaft 16 may include actuating the first cam phaser 18 coupled
to the first camshaft 14. The second camshaft 16 may also be
rotated relative to the first camshaft 14 via the second cam phaser
20 coupled to the second camshaft 16.
[0030] The first valve lift profile may include the first peak 34
of the first cam lobe 26 being engaged with the valve lift
mechanism 24 when the second peak 40 of the second cam lobe 28 is
engaged with the valve lift mechanism 24. The second valve lift
profile may include the first peak 34 of the first cam lobe 26
being rotationally offset from the valve lift mechanism 24 when the
second peak 40 of the second cam lobe 28 is engaged with the valve
lift mechanism 24.
[0031] The engine valve 22 may be displaced to a maximum valve lift
height when the first cam lobe 26 is in a fully retarded position
and the second cam lobe 28 is in a fully advanced position. A
maximum retarded condition for displacement of the engine valve 22
may be defined when the first cam lobe 26 is in a fully retarded
position and the second cam lobe 28 is in a fully retarded
position. A maximum advanced condition for displacement of the
engine valve 22 may be defined when the first cam lobe 26 is in a
fully advanced position and the second cam lobe 28 is in a fully
advanced position. A maximum opening duration of the engine valve
22 may be defined when the first cam lobe 26 is in a fully advanced
position and the second cam lobe 28 is in a fully retarded
position.
[0032] Displacing the engine valve 22 from the closed position to
the open position at the second valve lift profile may include the
first cam lobe 26 being engaged with the first end 44 of the valve
lift mechanism 24 and the second cam lobe 28 being engaged with the
second end 46 of the valve lift mechanism 24. The engagement
between the first and second cam lobes 26, 28 and the valve lift
mechanism 24 may rotationally displace the valve lift mechanism 24
about the pivot 50 located between the first and second ends 44, 46
of the valve lift mechanism 24 to provide the second valve lift
profile.
* * * * *