Information
-
Patent Grant
-
6736096
-
Patent Number
6,736,096
-
Date Filed
Thursday, February 21, 200222 years ago
-
Date Issued
Tuesday, May 18, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Denion; Thomas
- Corrigan; Jaime
Agents
-
CPC
-
US Classifications
Field of Search
US
- 123 9015
- 123 9016
- 123 9017
- 074 567
- 074 568 R
-
International Classifications
-
Abstract
A variable valve actuating (VVA) mechanism includes a frame member and a rocker. The rocker includes a first end and a second end, with the first end being pivotally coupled to the frame. A link includes a first end and a second end. A first pin pivotally couples the first end of the link to the second end of the rocker. A second pin pivotally couples an output cam to the second end of the link. At least one of the first and second pins is an eccentric pin.
Description
TECHNICAL FIELD
The present invention relates to variable valve actuating mechanisms and, more particularly, to a variable valve actuating mechanism that enables adjustment of the amount by which one valve is lifted relative to another valve within the same engine cylinder.
BACKGROUND OF THE INVENTION
Modern internal combustion engines may incorporate advanced throttle control systems, such as, for example, intake valve throttle control systems, to improve fuel economy and performance. Generally, intake valve throttle control systems control the flow of gas and air into and out of the engine cylinders by varying the timing and/or lift (i.e., the valve lift profile) of the cylinder valves in response to engine operating parameters, such as engine load, speed, and driver input. For example, the valve lift profile is varied from a relatively high-lift profile under high-load engine operating conditions to a reduced/lower low-lift profile under engine operating conditions of moderate and low loads.
Intake valve throttle control systems vary the valve lift profile through the use of various mechanical and/or electromechanical configurations, collectively referred to herein as variable valve actuation mechanisms. Several examples of particular variable valve actuation mechanisms are detailed in commonly-assigned U.S. Pat. No. 5,937,809, the disclosure of which is incorporated herein by reference. A variable valve actuation mechanism varies the lift profiles of one or more associated valves from a high-lift profile under high-load engine operating conditions to a reduced/lower low-lift profile under engine operating conditions of moderate and low loads. The valves may be lifted, for example, 8-10 millimeter (mm) under the high-lift profile and 1.0 mm or less under the low-lift profile. Contemporary engines typically include 4 valves per cylinder, i.e., two intake valves and two exhaust valves. The engine may be variously configured, such as, for example, with one variable valve actuation mechanism per cylinder that actuates both intake valves of that cylinder or configured with two variable valve actuation mechanisms per cylinder each of which actuate a corresponding pair of intake or exhaust valves.
Variable valve actuating mechanisms may be manually adjusted during installation in order to match the peak lifts of valves in different cylinders. Matching the peak valve lifts of valves in different cylinders increases engine stability and reduces rough engine operation, especially at low peak lift operating conditions. Matching the peak lifts ensures each of the valves is opened the same amount and, thus, each cylinder produces approximately the same amount of power. Although the peak lifts of valves of different cylinders can be matched, conventional variable valve actuating mechanisms do not enable the adjustment and/or matching of peak valve lifts of the valves associated with an individual engine cylinder. Thus, the peak lifts of the valves associated with an individual engine cylinder may be undesirably mismatched.
An undesirable mismatch between the peak lifts of valves associated with an individual engine cylinder is generally attributable to dimensional variation, and will typically be in the range of from approximately 1.0 mm to approximately 0.5 mm or less. When the valves are actuated such that their peak lifts are relatively high, such as, for example, greater than 8 mm, such a mismatch constitutes a relatively small percentage of the peak lift. However, under certain engine operating conditions, such as, for example, engine idle and low speed engine operating conditions, the valves are actuated such that their peak lift is relatively small, such as, for example, from approximately 0.5 millimeters (mm) to approximately 1.0 mm of peak lift. At such relatively low peak lift amounts, such a mismatch constitutes a substantial and significant percentage of the peak valve lift. Thus, the mismatch in lifts becomes proportionally greater as the peak lifts decrease.
A mismatch between the peak lifts of the valves associated with an individual engine cylinder can result in undesirable or unintended airflow characteristics, such as, for example, reduced tumble and/or excessive swirl. Since the mismatch becomes proportionally greater relative to the peak valve lift as the peak valve lift decreases, these undesirable characteristics are also magnified as the peak valve lifts decrease.
Therefore, what is needed in the art is an apparatus and method that enables the peak valve lifts within a cylinder to be adjusted and, thus, set or calibrated to within a relatively close or desired tolerance.
Furthermore, what is needed in the art is an apparatus and method that enables the peak valve lifts within a cylinder to be matched to within a relatively close tolerance at low peak lift engine operating conditions.
SUMMARY OF THE INVENTION
The present invention provides a variable valve actuating mechanism that enables independent adjustment of the peak lift of one valve relative to another valve actuated by the same mechanism.
The invention comprises, in one form thereof, a frame member and a rocker. The rocker includes a first end and a second end, with the first end being pivotally coupled to the frame. A link includes a first end and a second end. A first pin pivotally couples the first end of the link to the second end of the rocker. A second pin pivotally couples an output cam to the second end of the link. At least one of the first and second pins is an eccentric pin.
An advantage of the present invention is that the peak valve lift of one valve relative to another valve within the same cylinder is adjustable.
A further advantage of the present invention is that the peak lifts of the valves within a cylinder are matched and/or set to within a relatively close tolerance.
A still further advantage of the present invention is that tumble and/or swirl within a cylinder is adjusted by adjusting the relative lifts of the valves within the cylinder.
An even further advantage of the present invention is that the peak lifts of the valves within a cylinder are matched to within a relatively close tolerance at low peak lift engine operating conditions.
BRIEF DESCRIPTION OF THE DRAWINGS
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become apparent and be better understood by reference to the following description of one embodiment of the invention in conjunction with the accompanying drawings, wherein:
FIG. 1
is a side view of a conventional variable valve actuating (VVA) mechanism;
FIG. 2
is a side view of one embodiment of a variable valve actuating mechanism of the present invention;
FIG. 3
is an exploded view of the rocker, links and eccentric pin of
FIG. 2
;
FIG. 4
is a partial, exploded view of an alternate embodiment of a VVA mechanism of the present invention;
FIG. 5
is a side view of the VVA mechanism of
FIG. 3
; and
FIG. 6
is a side view of the VVA mechanism of FIG.
4
.
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, and particularly to
FIG. 1
, there is shown a conventional variable valve actuating (VVA) mechanism. VVA mechanism
10
is configured as a control gear type VVA mechanism. VVA mechanism
10
is operably installed in relation to camshaft
12
of engine
14
, and includes frame
20
, rocker
22
, link
24
a
and output cam
26
.
Camshaft
12
is driven to rotate by and in timed relation to a crankshaft (not shown) of engine
14
. Camshaft
12
rotates relative to central axis A thereof, and includes cam lobe
28
that rotates as substantially one body with camshaft
12
. Frame
20
is pivotally associated with camshaft
12
and is pivoted relative to central axis A by control gear
30
. Control gear
30
is disposed upon and pivoted by control shaft
32
, which has a central axis S that is substantially parallel relative to and spaced apart from central axis A. Frame
20
is pivotally coupled to rocker
22
by pin
34
. Rocker
22
carries roller
36
that engages cam lobe
28
of camshaft
12
. Rotation of cam lobe
28
pivotally oscillates roller
36
and, thus, rocker
22
in a generally radial direction toward and away from central axis A of camshaft
12
. Rocker
22
is pivotally coupled to link
24
a
by pin
38
, which transfers the pivotal oscillation of rocker
22
to corresponding pivotal oscillation of link
24
a
. Link
24
a
is pivotally coupled to output cam
26
by pin
40
, which transfers the pivotal oscillation of link
24
a
to corresponding pivotal oscillation of output cam
26
. The pivotal oscillation of output cam
26
acts on cam follower
42
, such as, for example, a direct acting cam follower or roller finger follower, that reciprocates and thereby opens and closes valve
44
of engine
14
.
The angular orientation of output cam
26
relative to central axis A and relative to cam follower
42
determines the portion of the lift profile of output cam
26
that engages cam follower
42
as output cam
26
is pivotally oscillated. Thus, the angular orientation of output cam
26
relative to central axis A and relative to cam follower
42
determines the lift profile of valve
44
. As described above, frame
20
is pivoted relative to central axis A of camshaft
12
by control gear
30
which, in turn, is pivoted by control shaft
32
. Control shaft
32
is placed in a predetermined angular position relative to central axis S thereof to thereby determine the angular position of frame
20
and, thus, output cam
26
relative to central axis A. Output cam
26
is thus placed in a predetermined angular orientation relative to central axis A which corresponds to a desired valve lift profile.
Valve
44
is one of the valves, such as, for example, an intake valve, associated with a cylinder (not shown) of engine
14
. Each cylinder of engine
14
includes, for example, two intake valves and two exhaust valves. Thus, although not shown in
FIG. 1
, VVA mechanism
10
may include a second link and output cam assembly that actuates one of the other valves of the same cylinder with which valve
44
is associated.
As described above, conventional variable valve actuating mechanisms do not enable the peak valve lifts of the valves actuated thereby to be relatively adjusted. Thus, there is likely to be a mismatch between the peak lift amounts of the valves actuated by the variable valve actuating mechanism. A relatively small mismatch, such as, for example, 0.5 mm, between the peak lifts of the valves within an engine cylinder can result in undesirable airflow characteristics within the cylinder, such as, for example, reduced tumble and/or excessive swirl. The present invention enables the relative peak lifts of the valves to be matched and/or set, thereby enabling adjustment of tumble and/or swirl within that cylinder. Furthermore, dimensional variation within a conventional variable valve actuating mechanisms results in a mismatch between valve lifts operating under relatively low peak lift operating conditions. The present invention enables the lifts of valves operating under such low peak lift operation conditions to be more closely matched, thereby improving engine stability and reducing rough engine idling.
Referring now to
FIGS. 2
,
3
and
5
, one embodiment of a VVA mechanism of the present invention is shown. VVA mechanism
60
, although differently configured from VVA mechanism
10
(FIG.
1
), includes several parts that correspond to VVA mechanism
10
in function and in design, and corresponding reference numbers are used to refer to those corresponding parts. VVA mechanism
60
includes frame
20
, rocker
22
carrying roller
36
(FIG.
3
), links
24
a
and
24
b
(FIG.
3
), output cam
26
, control clamp
30
and control shaft
32
(shown in
FIG. 2
only).
Generally, VVA mechanism
60
substitutes an eccentric pin for pin
38
of VVA
10
(
FIG. 1
) to pivotally couple rocker
22
to links
24
a
,
24
b
. The use of an eccentric pin to pivotally couple rocker
22
to links
24
a
and
24
b
enables the lift of a first valve (not shown) actuated by output cam
26
via link
24
a
to be matched and/or set relative to the lift of a second valve (not shown) actuated by a second output cam (not shown) via link
24
b
of VVA mechanism
60
.
As best shown in
FIGS. 3 and 5
, VVA mechanism
60
includes eccentric pin
62
that pivotally couples together rocker
22
and links
24
a
and
24
b
. Eccentric pin
62
has a first centerline C and a second centerline C′ that is substantially parallel relative to and spaced apart from centerline C. Eccentric pin
62
further includes pin sections
62
a
,
62
b
and eccentric pin section
62
c.
Pin section
62
a
extends axially from one side of pin section
62
b
, and both pin section
62
a
and section
62
b
are substantially concentric relative to each other and relative to centerline C. Eccentric section
62
c
is substantially concentric relative to centerline C′ and is, thus, eccentric relative to centerline C and pin sections
62
a
and
62
b
. The amount or distance by which centerlines C and C′ are separated, i.e., the degree of relative eccentricity of centerlines C and C′, is from approximately 0.001 millimeters (mm) to approximately 1.0 mm. At least one of pin section
62
a
and eccentric section
62
c
define tool-accepting feature
64
(
FIG. 3
, shown in pin section
62
a
), such as, for example, a hexagonal socket. Tool-accepting feature
64
accepts a tool, such as, for example, an Allen wrench or other type of wrench, to facilitate rotation and/or adjustment of the angular orientation of eccentric pin
62
when in the installed or use position.
As stated above, eccentric pin
62
pivotally couples together rocker
22
and links
24
a
,
24
b
. More particularly, pin section
62
a
is received within orifice
66
formed in link
24
b
, eccentric section
62
c
is received within orifice
66
formed in link
24
a
, and pin section
62
b
is received within bore
68
formed through rocker
22
. One of retaining means
72
(two shown), such as, for example, set screws, retains eccentric pin
62
in position within bore
69
and orifice
66
, and retains centerline C′ in a desired angular position or relative orientation relative to centerline C. It is to be understood that two retaining means
72
are shown only to illustrate two possible locations therefor. The use of both retaining means
72
is not required and, furthermore, would cause slippage between and undesirable wear of retaining means
72
and/or eccentric pin
62
.
Link
24
a
is pivotally coupled by pin
40
(
FIG. 5
) to output cam
26
, whereas link
24
b
is pivotally coupled to the second output cam (not shown) of VVA mechanism
60
by a second pin (not shown).
In use, the nominal lift and/or the nominal lift profile of the valves associated with VVA mechanism
60
is set by the angular position of control shaft
32
(
FIG. 2
) relative to central axis S thereof, as is known in the art. Generally, VVA mechanism
60
enables the peak lift of the valve actuated by output cam
26
to be matched with and/or set relative to the peak lift of the valve (not shown) actuated by the second output cam (not shown) of VVA mechanism
60
by pivoting eccentric pin
62
relative to centerline C. More particularly, pivoting eccentric pin
62
relative to centerline C pushes and/or pulls on link
24
a
to thereby pivot output cam
26
relative to central axis A. Pivoting output cam
26
relative to central axis A, in turn, changes the portion of the lift profile of output cam
26
that engages cam follower
42
(
FIGS. 1 and 2
) associated therewith and which transfers pivotal oscillation of output cam
26
to actuation of the associated valve (not shown). The portion of the lift profile of output cam
26
that engages the cam follower determines the amount of lift imparted to the associated valve. Thus, by pivoting eccentric pin
62
the peak lift of the valve associated with output cam
26
is adjusted relative to the peak lift of a second valve that is actuated by a second output cam of VVA mechanism
60
.
The effect of pivoting eccentric pin
62
on the angular orientation of output cam
26
is hereinafter discussed in detail. Referring to
FIG. 5
, angle α is defined between respective lines drawn from centerlines C and C′ to central axis A of camshaft
12
. With angle α equal to zero degrees, output cam
26
occupies a base angular orientation B relative to central axis A of camshaft
12
. Output cam
26
in base angular orientation B imparts substantially the desired nominal lift to the associated valve, since the position of output cam
26
is substantially unchanged from that established by control shaft
32
. Angle φ is defined as the degree to which output cam
26
has been pivoted from the base angular orientation B thereof relative to central axis A and into a new or adjusted base angular orientation. Generally, pivoting eccentric pin
62
relative to the centerline C varies angle α. A change in angle α results in a corresponding change in angle φ and, thus, a change in the angular orientation of output cam
26
relative to central axis A.
More particularly, as eccentric pin
62
is pivoted centerline C′ and eccentric section
62
c
(
FIG. 3
) pivot relative to centerline C thus causing angle α to vary. The pivoting of eccentric section
62
c
pushes and/or pulls link
24
a
thereby pivoting output cam
26
relative to central axis A and varying angle φ. Angle α is varied by rotation of eccentric pin
62
from a positive or clockwise maximum value α
MAX
to a negative or counter-clockwise maximum value referred to hereinafter as α
MIN
(not shown). Similarly, angle φ is varied by the rotation of eccentric pin
62
from a positive or clockwise maximum φ
MAX
to a negative or counterclockwise maximum hereinafter referred to as φ
MIN
(not shown).
Each of angles α and φ are approximately equal to zero degrees with eccentric pin
62
oriented such that centerlines C and C′ are approximately coplanar with central axis A, regardless of whether centerline C or centerline C′ is disposed most proximate to central axis A. Thus, angles α and φ are approximately equal to zero degrees with eccentric pin
62
in one of the two aforementioned angular orientations. With angles α and φ equal to zero degrees, output cam
26
is oriented in base angular orientation B. Thus, the lift imparted by output cam
26
to the associated valve is approximately the nominal lift as established by control shaft
32
.
Angle α is maximized in the clockwise direction to α
MAX
by pivoting eccentric pin
62
such that centerlines C and C′ are disposed in a generally coplanar manner with the central axis (not referenced) of pin
40
with centerline C′ being disposed most proximate to pin
40
. Pivoting eccentric pin
62
to place angle α at α
MAX
displaces or pushes link
24
a
in a clockwise direction, and thereby causes output cam
26
to pivot relative to central axis A in a clockwise direction such that angle φ is also maximized in a clockwise direction to angle φ
MAX
. Thus, output cam
26
is oriented in a new or adjusted base angular orientation B
MAX
by pivoting eccentric pin
62
such that centerlines C and C′ are disposed in a generally coplanar manner relative to the central axis (not referenced) of pin
40
with centerline C′ being disposed most proximate to pin
40
.
Adjusted base angular orientation B
MAX
represents the maximum clockwise angular orientation of output cam
26
, i.e., output cam
26
is maximally pivoted in a clockwise direction relative to base angular orientation B. Orienting output cam
26
in adjusted base orientation B
MAX
disposes a greater portion of the low lift or constant radius portion of output cam
26
within the pivotal oscillatory range of output cam
26
. As output cam
26
is pivotally oscillated from adjusted base orientation B
MAX
, more of the low-lift portion of the lift profile of output cam
26
engages the cam follower relative to the portion that engages the cam follower when output cam
26
is pivotally oscillated from base orientation B. Thus, the lift imparted to the associated valve when output cam
26
is pivotally oscillated from adjusted base orientation B
MAX
is maximally reduced relative to the nominal lift that is imparted by pivotally oscillating output cam
26
from base orientation B.
Angle α is maximized in the counterclockwise direction to α
MIN
(not shown) by pivoting eccentric pin
62
such that centerlines C and C′ are disposed approximately coplanar with the central axis (not referenced) of pin
40
with centerline C being disposed most proximate to pin
40
. Pivoting eccentric pin
62
to place angle α at α
MIN
displaces or pulls link
24
a
in a counter-clockwise direction and thereby causes output cam
26
to pivot relative to central axis A in a counter-clockwise direction such that angle φ is also maximized in a counter-clockwise direction to angle φ
MIN
(not shown). Thus, output cam
26
is oriented in a new or adjusted base angular orientation B
MIN
(not shown) by pivoting eccentric pin
62
such that centerlines C and C′ are disposed approximately coplanar relative to the central axis (not referenced) of pin
40
with centerline C being disposed most proximate to pin
40
.
Adjusted base orientation B
MIN
represents the maximum counter-clockwise base position of output cam
26
, i.e., output cam
26
is maximally pivoted in a counterclockwise direction relative to base angular orientation B. Orienting output cam
26
in adjusted base orientation B
MIN
disposes a greater portion of the higher lift profile of output cam
26
within the pivotal oscillation range of output cam
26
. As output cam
26
is pivotally oscillated from adjusted base orientation B
MIN
, more of the high lift portion of the lift profile of output cam
26
engages the cam follower relative to the portion that engages the cam follower when output cam
26
is pivotally oscillated from adjusted base orientation B
MIN
. Thus, the lift imparted to the associated valve when output cam
26
is pivotally oscillated from adjusted base position B
MIN
is maximally increased relative to the nominal lift that is imparted by pivotally oscillating output cam
26
from base angular orientation B.
It should be particularly noted that the angular orientation of eccentric pin
62
and, thus, the angular position of centerline C′ relative to centerline C are variable through three hundred and sixty degrees. Therefore, VVA
60
enables the substantially continuous adjustment of the lift of the valve associated with output cam
26
. The lift of the associated valve is minimized, i.e., adjusted to a peak value of the nominal lift minus an adjustment value, with output cam
26
oriented in adjusted base position B
MAX
. Conversely, the lift of the associated valve is maximized, i.e., adjusted to a peak value of the nominal lift plus an adjustment value, with output cam
26
oriented in adjusted base position B
MIN
.
Pivoting eccentric pin
62
in either a clockwise or counterclockwise direction with output cam
26
in adjusted base angular orientation B
MAX
, wherein the lift is minimized, increases the lift imparted to the associated valve. More particularly, such a pivoting of eccentric pin
62
displaces or pulls link
24
a
thereby causing output cam
26
to pivot in a counterclockwise direction. As output cam
26
pivots in a counterclockwise direction from adjusted base angular orientation B
MAX
, the high lift portion thereof is brought angularly more proximate to the cam follower. Thus, as output cam
26
is pivotally oscillated more of the high lift portion of the lift profile of output cam
26
engages the cam follower relative to adjusted base angular orientation B
MAX
.
The counterclockwise pivoting of output cam
26
, and thus the increase in lift imparted to the associated valve, continues until eccentric pin
62
is pivoted in either direction approximately one-hundred eighty degrees (180°) from adjusted base angular orientation B
MAX
. Pivoting eccentric pin
62
approximately 180° in either direction from adjusted base angular orientation B
MAX
orients eccentric pin
62
such that centerlines C and C′ are substantially coplanar relative to the central axis of pin
40
with centerline C most proximate to pin
40
. Thus, output cam
26
is placed in adjusted base angular orientation B
MIN
wherein the lift imparted to the valve is maximized.
Conversely, pivoting eccentric pin
62
in either a clockwise or counterclockwise direction with output cam
26
in adjusted base angular orientation B
MIN
, wherein the lift is maximized, decreases the lift imparted to the associated valve. Such a pivoting of eccentric pin
62
displaces or pushes link
24
a
in a clockwise direction thereby causing output cam
26
to pivot in a clockwise direction. As output cam
26
pivots in a clockwise direction from adjusted base angular orientation B
MIN
, the low lift portion thereof is brought angularly more proximate to the cam follower. Thus, as output cam
26
is pivotally oscillated more of the low lift portion of the lift profile of output cam
26
engages the cam follower relative to adjusted base angular orientation B
MAX
. The clockwise pivoting of output cam
26
, and thus the decrease in lift imparted to the associated valve, continues until eccentric pin
62
is pivoted in either direction approximately 180° from adjusted base angular orientation B
MIN
.
As stated above, the relative eccentricity of centerlines C and C′ is from approximately 0.001 mm to approximately 1.0 mm. Centerlines C and C′ can be positioned such that they are each substantially coplanar relative to the central axis of pin
40
in two possible orientations, i.e., one with centerline C′ most proximate to pin
40
and the other with centerline C most proximate to pin
40
. Thus, for example, with a given eccentricity of 1.0 mm the eccentricity of eccentric pin
62
is continuously adjustable from ±1.0 mm relative to (i.e., toward and away from) pin
40
. The corresponding range over which output cam
26
is pivoted relative to central axis A, and thus the range over which the lift of the valve associated with output cam
26
is adjusted, is dependent upon the configuration of the particular VVA mechanism with which eccentric pin
62
is used.
Adjustment of the angular orientation of eccentric pin
62
is facilitated by, for example, inserting a wrench or other tool into, tool-accepting feature
64
. With eccentric pin
62
in the desired angular orientation, either one of retaining means
72
is installed and tightened to secure and retain eccentric pin
62
in the desired orientation and position within orifices
66
and bore
68
. Thus, the lift of the valve associated with output cam
26
is adjusted from a nominal value to an adjusted valve relative to the lift of the second valve actuated by the second output cam of VVA mechanism
60
. The relative lifts of the valve actuated by output cam
26
and the second output cam are set and/or calibrated to achieve, for example, matching peak lifts or a desirable difference in peak lifts to create favorable air flow characteristics within the cylinder.
Referring now to
FIGS. 4 and 6
, a second exemplary embodiment of a VVA mechanism of the present invention is shown. Generally, VVA mechanism
80
substitutes an eccentric pin for pin
40
of VVA
10
(
FIG. 1
) to pivotally couple links
24
a
and
24
b
to output cam
26
. The eccentric pin enables the lift of a first valve (not shown) actuated by output cam
26
via link
24
a
to be matched with and/or set relative to the lift of a second valve (not shown) actuated by a second output cam via link
24
b
(not shown) of VVA mechanism
80
.
VVA mechanism
80
includes eccentric pin
82
having centerlines C and C′, pin sections
82
a
,
82
b
, and eccentric section
82
c
. Centerline C is substantially parallel relative to and spaced apart from centerline C′. Pin section
82
a
extends axially from one side of eccentric section
82
c
, and pin section
82
b
extends axially from an opposite end of eccentric section
82
c
. Pin sections
82
a
and
82
b
are substantially concentric relative to each other and relative to centerline C. Eccentric section
82
c
is substantially concentric relative to centerline C′ and is, thus, eccentric relative to centerline C and pin sections
82
a
and
82
b
. The amount or distance by which centerlines C and C′ are separated, i.e., the degree of relative eccentricity of centerlines C and C′, is from approximately 0.001 millimeters (mm) to approximately 1.0 mm.
Eccentric pin
82
pivotally couples link
24
a
with output cam
26
. Pin sections
82
a
and
82
b
are received within a respective one of orifices
84
formed in link
24
a
, and eccentric section
82
c
is received within orifice
86
formed in output cam
26
. Retaining means
72
, such as, for example, a set screw, retains eccentric pin
62
within orifice
86
and further retains centerline C′ and centerline C in a desired angular position and/or relative angular orientation. Collars or bushings
88
are inserted into a respective one of orifices
84
and over a corresponding one of pin sections
82
a
and
82
b.
In use, VVA mechanism
80
operates in a generally similar manner to VVA mechanism
60
and enables the lift of the valve associated with output cam
26
to be matched with and/or set relative to the lift of a second valve actuated by a second output cam of VVA mechanism
80
. The nominal lift and/or the nominal lift profile of the valves associated with VVA mechanism
60
is set by the angular position of control shaft
32
(
FIG. 2
) relative to central axis S thereof, as is known in the art.
The effect of pivoting eccentric pin
82
on the angular orientation of output cam
26
is hereinafter discussed in detail. Referring to
FIG. 6
, angle α is varied by rotation of eccentric pin
82
from a positive or clockwise maximum value α
MAX
to a negative or counter-clockwise maximum value α
MIN
(not shown). Similarly, angle φ is varied by the rotation of eccentric pin
82
from a positive or clockwise maximum φ
MAX
to a negative or counterclockwise maximum φ
MIN
(not shown).
Each of angles α and φ are approximately equal to zero degrees with eccentric pin
82
oriented such that centerlines C and C′ are approximately coplanar with central axis A, regardless of whether centerline C or centerline C′ is disposed most proximate to central axis A. Thus, angles α and φ are approximately equal to zero degrees with eccentric pin
82
in one of the two aforementioned angular orientations. With angles α and φ equal to zero degrees, output cam
26
is oriented in base angular orientation B. Thus, the lift imparted by output cam
26
to the associated valve is approximately the nominal lift as established by control shaft
32
.
Angle α is maximized in the clockwise direction to α
MAX
by pivoting eccentric pin
82
such that centerlines C and C′ are disposed in a generally coplanar manner with the central axis (not referenced) of pin
38
with centerline C being disposed most proximate to pin
38
. Pivoting eccentric pin
82
to place angle α at α
MAX
displaces or pushes output cam
26
in a clockwise direction, and thereby causes output cam
26
to pivot relative to central axis A in a clockwise direction such that angle φ is also maximized in a clockwise direction to angle φ
MAX
. Thus, output cam
26
is oriented in adjusted base angular orientation B
MAX
with eccentric pin
82
oriented such that centerlines C and C′ are disposed in a generally coplanar manner relative to the central axis (not referenced) of pin
30
with centerline C being disposed most proximate to pin
38
.
Adjusted base position B
MAX
represents the maximum clockwise base position of output cam
26
, i.e., output cam
26
is maximally pivoted in a clockwise direction relative to base angular orientation B. Orienting output cam
26
in adjusted base orientation B
MAX
disposes a greater portion of the low lift or constant radius portion of output cam
26
within the pivotal oscillatory range of output cam
26
. As output cam
26
is pivotally oscillated from adjusted base orientation B
MAX
, more of the low-lift portion of the lift profile of output cam
26
engages the cam follower relative to the portion that engages the cam follower when output cam
26
is pivotally oscillated from base position B. Thus, the lift imparted to the associated valve when output cam
26
is pivotally oscillated from adjusted base orientation B
MAX
is maximally reduced relative to the nominal lift that is imparted by pivotally oscillating output cam
26
from base position B.
Angle α is maximized in the counterclockwise direction to α
MIN
(not shown) by pivoting eccentric pin
82
such that centerlines C and C′ are disposed approximately coplanar with the central axis (not referenced) of pin
38
with centerline C′ being disposed most proximate to pin
30
. Pivoting eccentric pin
82
to place angle α at α
MIN
displaces or pulls output cam
26
in a counter-clockwise direction such that angle φ is also maximized in a counter-clockwise direction to angle φ
MIN
(not shown). Thus, output cam
26
is oriented in adjusted base angular orientation B
MIN
(not shown).
Adjusted base orientation B
MIN
represents the maximum counter-clockwise base position of output cam
26
, i.e., output cam
26
is maximally pivoted in a counterclockwise direction relative to base angular orientation B. Orienting output cam
26
in adjusted base orientation B
MIN
disposes a greater portion of the higher lift profile of output cam
26
within the pivotal oscillation range of output cam
26
. As output cam
26
is pivotally oscillated from adjusted base orientation B
MIN
, more of the high lift portion of the lift profile of output cam
26
engages the cam follower relative to the portion that engages the cam follower when output cam
26
is pivotally oscillated from adjusted base orientation B
MIN
. Thus, the lift imparted to the associated valve when output cam
26
is pivotally oscillated from adjusted base position B
MIN
is maximally increased relative to the nominal lift that is imparted by pivotally oscillating output cam
26
from base angular orientation B.
It should be particularly noted that, substantially similar to VVA mechanism
60
, the angular orientation of eccentric pin
82
of VVA mechanism
80
and, thus, the angular orientation of centerline C′ relative to centerline C are variable through three hundred and sixty degrees. Accordingly, the angular orientation of output cam
26
is substantially continuously adjustable from adjusted base orientation B
MIN
to adjusted base orientation B
MAX
. Therefore, the lift of the valve associated with output cam
26
is also substantially continuously adjustable from a maximally increased lift to a maximally decreased lift relative to the nominal lift, as determined by the angular orientation of control shaft
32
. The lift of the valve associated with output cam
26
is thereby set or relative to or calibrated with the lift of the valve associated with the second output cam of VVA mechanism
80
.
It should further be particularly noted that, substantially similar to VVA mechanism
60
, pivoting eccentric pin
82
in either a clockwise or counterclockwise direction with output cam
26
in adjusted base angular orientation B
MAX
, wherein the lift is minimized, increases the lift imparted to the associated valve. Conversely, and still substantially similar to VVA mechanism
60
, pivoting eccentric pin
82
in either a clockwise or counterclockwise direction with output cam
26
in adjusted base angular orientation B
MIN
, wherein the lift is maximized, decreases the lift imparted to the associated valve.
In the embodiments shown, an eccentric pin couples together at least one of the links with one of a rocker or corresponding output cam. However, it is to be understood that the VVA of the present invention can be alternately configured, such as, for example, with an eccentric pin coupling at least one of the links with each of a corresponding output cam and the rocker.
In the embodiments shown, the eccentric pins are shown in conjunction with a particularly configured VVA mechanism. However, it is to be understood that the VVA mechanism of the present invention can be alternately configured, such as, for example, as a belt-driven VVA mechanism or any other suitable type of VVA mechanism, and still effectively adjust the amount of lift imparted to the associated valve.
In the embodiments shown, an eccentric pin is used to pivotally couple together one of two links with an output cam or one of two links with a rocker. However, it is to be understood that the present invention can be alternately configured, such as, for example, with a dual or integrated link (rather than two separate links) that is pivotally coupled by an eccentric pin to one of a pair of output cams or to a corresponding separate or an integrated rocker.
In the embodiments shown, retaining means, such as a set screw and/or a set screw and collar assembly, are used to retain the eccentric pin in the desired location and angular orientation. However, it is to be understood that the present invention can be alternately configured with various other retaining means.
In the embodiment shown, an eccentric pin is used to pivotally couple together one of a link and an output cam or a link and a rocker. However, it is to be understood that the present invention can be alternately configured, such as, for example, using an eccentric pin to pivotally couple together each link and rocker, and each link and corresponding output cam.
While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the present invention using the general principles disclosed herein. Further, this application is intended to cover such departures from the present disclosure as come within the known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
Claims
- 1. A method for setting the lift of a first valve relative to a second valve of an engine cylinder, at least said first valve being actuated by a variable valve actuating (VVA) mechanism, said method comprising:ascertaining the maximum lift of the second valve; determining the maximum lift of the first valve; and pivoting an eccentric pin of the VVA mechanism to thereby pivot an output cam thereof from a base angular orientation to an adjusted base angular orientation, thereby one of increasing and decreasing the lift imparted to the first valve by the VVA mechanism, wherein said pivoting step comprises pivoting an eccentric pin that pivotally couples together a rocker and a link of the VVA mechanism.
- 2. A method for setting the lift of a first valve relative to a second valve of an engine cylinder, at least said first valve being actuated by a variable valve actuating (VVA) mechanism, said method comprising:ascertaining the maximum lift of the second valve; determining the maximum lift of the first valve; and pivoting an eccentric pin of the VVA mechanism to thereby pivot an output cam thereof from a base angular orientation to an adjusted base angular orientation, thereby one of increasing and decreasing the lift imparted to the first valve by the VVA mechanism, wherein said pivoting step comprises pivoting an eccentric pin that pivotally couples together a link and an output cam of the VVA mechanism.
- 3. The method of claim 2, wherein said pivoting step comprises engaging a tool-accepting feature of the eccentric pin with a corresponding tool.
- 4. The method of claim 3, wherein said tool-accepting feature comprises a socket defined by an end of the eccentric pin.
- 5. A variable valve actuating (VVA) mechanism, comprising:a frame member configured for being pivoted relative to a central axis that is at least one of substantially parallel relative to and coaxial with a central axis of an input shaft; a rocker having a first end and a second end, said first end pivotally coupled to said frame; a link having a first end and a second end; a first pin pivotally coupling said first end of said link to said second end of said rocker; an output cam; a second pin pivotally coupling said output cam to said second end of said link; wherein at least one of said first and second pins is an eccentric pin.
- 6. The VVA mechanism of claim 5, wherein said first pin comprises an eccentric pin.
- 7. The VVA mechanism of claim 6, wherein said first pin comprises:a first pin portion having a first centerline, said first pin portion being substantially concentric relative to said first centerline; a second pin portion extending axially from said first pin portion, said second pin portion being substantially concentric relative to said first centerline; and an eccentric portion extending axially from said second pin portion, said eccentric portion having a second centerline, said eccentric portion being substantially concentric relative to said second centerline and eccentric relative to said first centerline, said second centerline being substantially parallel with and spaced apart from said first centerline.
- 8. The VVA mechanism of claim 7, wherein said second end of said rocker defines a rocker bore therethrough, said first end of said link defines a link bore therethrough, said eccentric portion being disposed at least partially within said link bore, said second pin portion being disposed at least partially within said rocker bore.
- 9. The VVA mechanism of claim 8, wherein said first centerline and said second centerline are spaced apart from each other from approximately 0.001 mm to approximately 1.5 mm.
- 10. The VVA mechanism of claim 5, wherein said second pin comprises an eccentric pin.
- 11. The VVA mechanism of claim 10, wherein said second pin comprises:an eccentric portion having a first centerline, said eccentric portion being substantially concentric relative to said first centerline; and pin portions extending axially in each direction from said eccentric portion, said pin portions having a second centerline and being substantially concentric relative thereto, said eccentric portion being eccentric relative to said second centerline, said second centerline being substantially parallel relative to and spaced apart from said first centerline.
- 12. The VVA mechanism of claim 11, wherein said second end of said link defines opposing link orifices therethrough, said output cam defines a cam orifice therein, said eccentric portion being disposed within said cam orifice, said pin portions being disposed at least partially within a respective one of said link orifices.
- 13. The VVA mechanism of claim 11, wherein said first centerline and said second centerline are spaced apart from each other from approximately 0.015 mm to approximately 1.5 mm.
- 14. The VVA mechanism of claim 5, further comprising retaining means associated with each said at least one eccentric pin.
- 15. The VVA mechanism of claim 14, wherein said retaining means comprises a set screw.
- 16. The VVA mechanism of claim 5, wherein said at least one eccentric pin includes a tool-accepting feature.
- 17. The VVA mechanism of claim 16, wherein said tool-accepting feature comprises a recessed socket defined by an end of said eccentric pin.
- 18. An internal combustion engine, said engine having at least one cylinder, at least four valves operably associated with said cylinder, said engine comprising:a variable valve actuating mechanism actuating at least one of said valves, said variable valve mechanism including: a frame member configured for being pivoted relative to a central axis that is one of substantially parallel relative to and coaxial with a central axis of a camshaft of said engine; a rocker having a first end and a second end, said first end pivotally coupled to said frame; a link having a first end and a second end; a first pin pivotally coupling said first end of said link to said second end of said rocker; an output cam; a second pin pivotally coupling said output cam to said second end of said link; wherein at least one of said first and second pins is an eccentric pin.
- 19. A variable valve actuating (VVA) mechanism, comprising:a frame member configured for being pivoted relative to a central axis that is at least one of substantially parallel relative to and coaxial with a central axis of an input shaft; a rocker having a first end and a second end, said first end pivotally coupled to said frame; a link having a first end and a second end; a first pin pivotally coupling said first end of said link to said second end of said rocker; an output cam; a second pin pivotally coupling said output cam to said second end of said link; wherein said first pin is an eccentric pin, and wherein said first pin comprises: a first pin portion having a first centerline, said first pin portion being substantially concentric relative to said first centerline; a second pin portion extending axially from said first pin portion, said second pin portion being substantially concentric relative to said first centerline; and an eccentric portion extending axially from said second pin portion, said eccentric portion having a second centerline, said eccentric portion being substantially concentric relative to said second centerline and eccentric relative to said first centerline, said second centerline being substantially parallel with and spaced apart from said first centerline.
- 20. The VVA mechanism of claim 19, wherein said second end of said rocker defines a rocker bore therethrough, said first end of said link defines a link bore therethrough, said eccentric portion being disposed at least partially within said link bore, said second pin portion being disposed at least partially within said rocker bore.
- 21. The VVA mechanism of claim 20, wherein said first centerline and said second centerline are spaced apart from each other from approximately 0.001 mm to approximately 1.5 mm.
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