U.S. patent application number 09/792734 was filed with the patent office on 2001-10-04 for belt-driven variable valve actuating mechanism.
Invention is credited to Pierik, Ronald J..
Application Number | 20010025614 09/792734 |
Document ID | / |
Family ID | 26880236 |
Filed Date | 2001-10-04 |
United States Patent
Application |
20010025614 |
Kind Code |
A1 |
Pierik, Ronald J. |
October 4, 2001 |
Belt-driven variable valve actuating mechanism
Abstract
A belt-driven variable valve actuating mechanism includes a
rocker having a central rocker axis that is substantially parallel
with and spaced apart from a central axis of a rotary input shaft.
A frame member has a first end configured for being pivotally
mounted upon the input shaft and a second end pivotally carrying
the rocker. A connecting rod has a first end configured for
engaging an eccentric of the rotary input shaft and a second end
pivotally attached to the rocker. The connecting rod transfers
rotation of the input shaft to oscillation of the rocker relative
to the rocker central axis. An output cam is configured for being
pivotally mounted upon the input shaft. A belt engages the rocker
and the output cam, and transfers oscillation of the rocker to
oscillation of the output cam.
Inventors: |
Pierik, Ronald J.;
(Rochester, NY) |
Correspondence
Address: |
Delphi Technologies, Inc.
P.O. Box 5052
Mail Code 480414420
Troy
MI
48007
US
|
Family ID: |
26880236 |
Appl. No.: |
09/792734 |
Filed: |
February 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60184544 |
Feb 24, 2000 |
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Current U.S.
Class: |
123/90.15 ;
123/90.17 |
Current CPC
Class: |
F01L 13/0021 20130101;
Y10T 74/2102 20150115 |
Class at
Publication: |
123/90.15 ;
123/90.17 |
International
Class: |
F01L 001/34 |
Claims
What is claimed:
1. A belt-driven variable valve mechanism, comprising: a rocker
having a central rocker axis, said rocker central axis being
substantially parallel with and spaced apart from a central axis of
a rotary input shaft; at least one frame member having a first end
and a second end, said first end configured for being pivotally
mounted upon the input shaft, said second end pivotally carrying
said rocker; a connecting rod having a first end and a second end,
said first end configured for engaging an eccentric of the rotary
input shaft, said second end pivotally attached to said rocker,
said connecting rod configured for transferring rotation of the
input shaft to oscillation of said rocker relative to said rocker
central axis; at least one output cam configured for being
pivotally mounted upon the input shaft; and at least one belt, each
of said at least one belt engaging said rocker and a corresponding
one of said at least one output cam, said at least one belt
configured for transferring oscillation of said rocker to
oscillation of a corresponding one of said at least one output
cam.
2. The belt-driven variable valve mechanism of claim 1, further
comprising a control shaft pivotable about a central shaft axis,
said central shaft axis being substantially parallel with and
spaced apart from the central axis of the input shaft, said control
shaft being pivotally coupled to each of said at least one frame
member.
3. The belt-driven variable valve mechanism of claim 1, wherein
said at least one belt is fastened to at least one of said rocker
and a corresponding one of said at least one output cam.
4. The belt-driven variable valve mechanism of claim 1, wherein
each said at least one output cam includes a respective
belt-engaging surface, said belt-engaging surface being one of
attached to and integral with said at least one output cam, each of
said at least one belt engaging at least a portion of said
belt-engaging surface of a corresponding said at least one output
cam.
5. The belt-driven variable valve mechanism of claim 1, wherein
said rocker includes at least one belt-engaging surface, said at
least one belt-engaging surface being one of attached to and
integral with said rocker, each of said at least one belt-engaging
surface of said rocker corresponding to one of said at least one
output cam, each of said at least one belt engaging at least a
portion of a corresponding one of said at least one belt-engaging
surface of said rocker.
6. The belt-driven variable valve mechanism of claim 1, wherein
each of said at least one output cam includes a respective
belt-engaging surface, said rocker includes at least one
belt-engaging surface, each of said at least one belt-engaging
surface of said rocker corresponding to one of said at least one
output cam, each said at least one belt engaging at least a portion
of said belt-engaging surface of a corresponding one of said at
least one output cam and a corresponding one of said at least one
belt-engaging surface of said rocker.
7. The belt-driven variable valve mechanism of claim 6, wherein
each of said at least one belt is fastened to at least one of said
belt-engaging surface of a corresponding one of said at least one
output cam and a corresponding one of said at least one
belt-engaging surface of said rocker.
8. The belt-driven variable valve mechanism of claim 6, wherein
said at least one belt-engaging surface of said rocker comprises a
drum sleeve affixed to said rocker.
9. The belt-driven variable valve mechanism of claim 6, wherein
said at least one belt-engaging surface of said rocker and said
belt-engaging surface of each of said at least one output cam are
substantially cylindrical, said belt-engaging surface of each of
said at least one output cam having a first diameter, said at least
one belt-engaging surface of said rocker having a second
diameter.
10. The belt-driven variable valve mechanism of claim 9, wherein
said first diameter is less than said second diameter.
11. The belt-driven variable valve mechanism of claim 6, wherein
said belt-engaging surface of each of said at least one output cam
is one of elliptical and eccentric in shape.
12. The belt-driven variable valve mechanism of claim 6, wherein
each of said at least one belt-engaging surface of said rocker is
one of elliptical and eccentric in shape.
13. The belt-driven variable valve mechanism of claim 1, wherein
each of said at least one frame member includes a bearing support,
said bearing support being one of attached to and integral with
said frame member.
14. A belt-driven variable valve mechanism, comprising: an elongate
input shaft having a central axis, an input eccentric disposed on
said input shaft; a rocker having a central rocker axis, said
central rocker axis being substantially parallel with and spaced
apart from said central axis of said rotary input shaft; at least
one frame member having a first end and a second end, said first
end pivotally mounted upon said input shaft, said second end
pivotally carrying said rocker; a connecting rod having a first end
and a second end, said first end engaging said eccentric, said
second end pivotally attached to said rocker, said connecting rod
configured for transferring rotation of said eccentric to
oscillation of said rocker relative to said rocker central axis; at
least one output cam pivotally mounted upon said input shaft; and
at least one belt, each of said at least one belt engaging said
rocker and a corresponding one of said at least one output cam,
said at least one belt configured for transferring oscillation of
said rocker to oscillation of a corresponding one of said at least
one output cam.
15. The belt-driven variable valve mechanism of claim 14, further
comprising a control shaft pivotable about a central shaft axis,
said central shaft axis being substantially parallel with and
spaced apart from said central axis of said input shaft, said
control shaft being pivotally coupled to each of said at least one
frame member.
16. The belt-driven variable valve mechanism of claim 14, wherein
said at least one belt is fastened to at least one of said rocker
and said at least one output cam.
17. The belt-driven variable valve mechanism of claim 14, wherein
each said at least one output cam includes a respective
belt-engaging surface, said belt-engaging surface being one of
attached to and integral with said at least one output cam, each of
said at least one belt engaging at least a portion of said
belt-engaging surface of a corresponding said at least one output
cam.
18. The belt-driven variable valve mechanism of claim 14, wherein
said rocker includes at least one belt-engaging surface, said at
least one belt-engaging surface being one of attached to and
integral with said rocker, each of said at least one belt-engaging
surface of said rocker corresponding to one of said at least one
output cam, each of said at least one belt engaging at least a
portion of a corresponding one of said at least one belt-engaging
surface of said rocker.
19. The belt-driven variable valve mechanism of claim 14, wherein
each of said at least one output cam includes a respective
belt-engaging surface, said rocker includes at least one
belt-engaging surface, each of said at least one belt-engaging
surface of said rocker corresponding to one of said at least one
output cam, each said at least one belt engaging at least a portion
of said belt-engaging surface of a corresponding one of said at
least one output cam and a corresponding one of said at least one
belt-engaging surface of said rocker
20. The belt-driven variable valve mechanism of claim 19, wherein
each of said at least one belt is fastened to at least one of said
belt-engaging surface of a corresponding one of said at least one
output cam and a corresponding one of said at least one
belt-engaging surface of said rocker.
21. The belt-driven variable valve mechanism of claim 19, wherein
said at least one belt-engaging surface of said rocker comprises a
drum sleeve affixed to said rocker.
22. The belt-driven variable valve mechanism of claim 19, wherein
said at least one belt-engaging surface of said rocker and said
belt-engaging surface of each of said at least one output cam are
substantially cylindrical, said belt-engaging surface of each of
said at least one output cam having a first diameter, said at least
one belt-engaging surface of said rocker having a second
diameter.
23. The belt-driven variable valve mechanism of claim 22, wherein
said first diameter is less than said second diameter.
24. The belt-driven variable valve mechanism of claim 19, wherein
said belt-engaging surface of each of said at least one output cam
is one of elliptical and eccentric in shape.
25. The belt-driven variable valve mechanism of claim 19, wherein
each of said at least one belt-engaging surface of said rocker is
one of elliptical and eccentric in shape.
26. The belt-driven variable valve mechanism of claim 14, wherein
each of said at least one frame member includes a bearing support,
said bearing support being one of attached to and integral with
said frame member.
27. The belt-driven variable valve mechanism of claim 14, wherein
said at least one belt defines a longitudinal slot therein, each of
said at least one belt engaging said rocker and a corresponding one
of said at least one output cam such that a portion of said belt is
disposed within said longitudinal slot.
28. An internal combustion engine, comprising: a belt-driven
variable valve mechanism, including: an elongate input shaft having
a central axis, an input eccentric disposed on said input shaft; a
rocker having a central rocker axis, said central rocker axis being
substantially parallel with and spaced apart from said central axis
of said rotary input shaft; at least one frame member having a
first end and a second end, said first end pivotally mounted upon
said input shaft, said second end pivotally carrying said rocker; a
connecting rod having a first end and a second end, said first end
engaging said eccentric, said second end pivotally attached to said
rocker, said connecting rod configured for transferring rotation of
said eccentric to oscillation of said rocker relative to said
rocker central axis; at least one output cam pivotally mounted upon
said input shaft; and at least one belt, each of said at least one
belt engaging said rocker and a corresponding one of said at least
one output cam, said at least one belt configured for transferring
oscillation of said rocker to oscillation of a corresponding one of
said at least one output cam.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application Ser. No. 60/184,544, filed Feb. 24, 2000.
TECHNICAL FIELD
[0002] The present invention relates to variable valve
mechanisms.
BACKGROUND OF THE INVENTION
[0003] Variable valve actuating mechanisms enable the variation of
the timing, lift and duration (i.e., the valve lift profile) of
associated valves, such as, for example, the valves of an internal
combustion engine. Two examples of variable valve actuating
mechanisms are detailed in commonly-assigned U.S. Pat. Nos.
5,937,809 and 6,019,076, the disclosure of which are incorporated
herein by reference.
[0004] As related to internal combustion engines, conventional
variable valve mechanisms are associated with a cam or input shaft
of the engine. More particularly, a conventional variable valve
mechanism typically includes a roller which engages an input cam of
the input shaft or the engine camshaft. One or more link or rocker
arms carry and link the roller to an output cam. Rotation of the
input cam displaces the roller to create oscillatory movement of
the components coupled thereto, such as link or rocker arms,
relative to the central axis of the input shaft or camshaft. The
oscillatory movement of the components that are coupled to the
roller, in turn, directly or indirectly oscillate an output cam and
thereby actuate one or more valves of the engine.
[0005] A biasing means, such as one or more return springs, is
generally required in order to maintain the roller in contact with
the input cam thereby reducing any mechanical lash. The use of
return springs, however, negatively impacts the durability and
limits the operating range of conventional variable valve
mechanisms, thereby limiting the range of engine operation speeds
over which the variable valve mechanism can be efficiently
utilized. In addition to return springs, conventional variable
valve mechanisms typically include numerous other component parts,
such as link arms, joints, pins and frames, and are thus relatively
complex mechanically. The numerous component parts increase the
cost of the mechanism and make the mechanism more difficult to
assemble and to manufacture.
[0006] Many of these numerous component parts are directly or
indirectly coupled to the roller, and are therefore caused to pivot
relative to the central axis of the input shaft as the input cam
displaces the roller. Each of these components parts increase the
mass of the structure which undergoes pivotal movement, and thereby
further limits the range of engine operation speeds over which the
variable valve mechanism can be used. The joints and pins that
interconnect the component parts of a conventional variable valve
mechanism are subject to interfacial frictional forces that
negatively impact durability and efficiency of the mechanism.
[0007] As stated above, conventional VVA mechanisms generally
include one or more link or rocker arms that carry and/or connect
the roller of the mechanism with the output cam of the mechanism.
The use of links and/or rockers increase the size of the VVA
mechanism, and thus a larger space is required in order to install
the VVA mechanism within the engine. The links and rocker arms are
typically coupled together by joints and/or pins, which further
increase the number of component parts and make the VVA mechanism
relatively complex from a mechanical standpoint. Furthermore, the
joints and pins are subject to interfacial frictional forces that
negatively impact durability and efficiency. Moreover, the link
adds to the oscillatory mass of the VVA mechanism, and thereby
limits the effective engine operating range within which the VVA
mechanism can be used.
[0008] Therefore, what is needed in the art is a variable valve
mechanism having fewer component parts.
[0009] Furthermore, what is needed in the art is a variable valve
mechanism with fewer joints and/or pins, and thus has reduced
frictional losses.
[0010] Still further, what is needed in the art is a variable valve
mechanism that eliminates the use of return springs, and is
therefore operable over an increased range of engine operating
speeds.
[0011] Moreover, what is needed in the art is a variable valve
mechanism that has reduced pivoting mass, and is therefore operable
over an increased range of engine operating speeds.
SUMMARY OF THE INVENTION
[0012] The present invention provides a belt-driven variable valve
actuating mechanism.
[0013] The invention comprises, in one form thereof, a rocker
having a central rocker axis that is substantially parallel with
and spaced apart from a central axis of a rotary input shaft. A
frame member has a first end configured for being pivotally mounted
upon the input shaft and a second end pivotally carrying the
rocker. A connecting rod has a first end configured for engaging an
eccentric of the rotary input shaft and a second end pivotally
attached to the rocker. The connecting rod transfers rotation of
the input shaft to oscillation of the rocker relative to the rocker
central axis. An output cam is configured for being pivotally
mounted upon the input shaft. A belt engages the rocker and the
output cam, and transfers oscillation of the rocker to oscillation
of the output cam.
[0014] An advantage of the present invention is that it uses fewer
component parts relative to a conventional variable valve
mechanism, thereby reducing the cost and complexity of the
mechanism.
[0015] Another advantage of the present invention is that fewer
joints/pins are necessary relative to a conventional variable valve
mechanism, thereby reducing frictional losses and increasing
durability of the mechanism.
[0016] A still further advantage of the present invention is that
return springs are not required, thereby further increasing the
durability of the mechanism and enabling use of the mechanism over
a wider range of engine operating conditions.
[0017] An even further advantage of the present invention is that
the pivoting mass is substantially reduced, thereby rendering the
mechanism operable over a wider range of engine operating
speeds.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] 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:
[0019] FIG. 1 is a perspective view of one embodiment of the
belt-driven variable valve mechanism of the present invention;
[0020] FIG. 2 is an end view of the belt-driven variable valve
mechanism of FIG. 1;
[0021] FIG. 3 is a cut-away end view of the belt-driven variable
valve mechanism of FIG. 1, wherein certain components are omitted
for the sake of clarity; and
[0022] FIG. 4 is a detail view of the connecting rod and rocker of
FIG. 1;
[0023] FIG. 5 is an end view of a second embodiment of a
belt-driven variable valve mechanism of the present invention;
and
[0024] FIG. 6 is a top view of the belt of FIG. 5.
[0025] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplifications set out
herein illustrate one preferred embodiment of the invention, in one
form, and such exemplifications are not to be construed as limiting
the scope of the invention in any manner.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] Referring now to the drawings, and particularly to FIG. 1,
there is shown one embodiment of a belt driven variable valve
actuating (VVA) mechanism of the present invention. Generally, and
as will be more particularly described hereinafter, WA mechanism 10
is operably associated with valves 12a, 12b and with rotary input
shaft 16 of internal combustion engine 14. Control shaft 18 is
pivoted to selectively vary the timing, duration and lift, i.e.,
the valve lift profile, of valves 12a, 12b. VVA 10 includes rocker
20, connecting rod 22, frame members 24a, 24b, drum sleeves 26a,
26b (only one shown), belts 28a, 28b and output cams 30a, 30b.
[0027] Rotary input shaft 16 is an elongate shaft member, such as,
for example, a camshaft of engine 14. Input shaft 16 has central
axis A, and is rotated three-hundred and sixty degrees (360
degrees) about central axis A. Input shaft 16 is driven to rotate
in timed relation to the engine crankshaft (not shown), such as,
for example, by a camshaft drive, chain, or other suitable means.
Input shaft 16 extends the length of the cylinder head (not shown)
of multi-cylinder engine 14. A single WA mechanism 10 is associated
with each cylinder of engine 14. Input shaft 16 includes input
eccentric 16a which rotates as substantially one body with input
shaft 16. Input eccentric 16a is, for example, affixed to or
integral with input shaft 16.
[0028] Control shaft 18 is selectively pivoted, such as, for
example, by an actuator subassembly (not shown) to establish the
lift profile of valves 12a, 12b, as will be more particularly
described hereinafter. Control shaft 18 pivots relative to shaft
axis S, which is substantially parallel with and spaced apart from
central axis A of input shaft 16. Control shaft 18 is coupled to
each of frame members 24a, 24b by respective shaft couplers 18a,
18b (FIG. 2, only one shown), such as, for example, shaft clamps,
such that pivotal movement of control shaft 18 relative to shaft
axis S is transferred to pivoting of frame members 24a, 24b
relative to central axis A.
[0029] Rocker 20 is an elongate arm member having central axis R.
Central axis R is substantially parallel with and spaced apart from
central axis A of input shaft 16. As best shown in FIG. 4, rocker
20 defines notched or recessed section 20a. A first end (not
referenced) of connecting rod 22 is pivotally coupled by rod
coupler 22a, such as, for example, a pin or peg, to rocker 20 at
notch section 20a. Rocker 20 is pivotally carried by each of frame
members 24a, 24b, such that pivotal movement of frame members 24a,
24b relative to central axis A results in the pivoting of rocker 20
relative to central axis A. Rocker 20 is free to pivot within and
relative to each of frame members 24a, 24b and about its own
central axis R. Drum sleeves 26a, 26b are affixed to rocker 20 at
opposite ends thereof.
[0030] Connecting rod 22 is an elongate arm member that is
pivotally coupled at a first end to rocker 20 and at the opposite
end to eccentric 16a of input shaft 16. More particularly, first
end (not referenced) of connecting rod 22 defines orifice 32a (see
FIG. 4) therethrough, within which is received at least a portion
of rod coupler 22a to thereby pivotally couple connecting rod 22 to
rocker 20. A second end (not referenced) of connecting rod 22
defines orifice 32b therethrough, within which is disposed at least
a portion of eccentric 16a to thereby couple connecting rod 22 to
input shaft 16. Connecting rod 22 transfers rotation of input shaft
16 and eccentric 16a to oscillatory movement of rocker 20 within
frame members 24a, 24b and about rocker axis R. Input eccentric 16a
is configured to impart a fixed range or degree of oscillation,
such as, for example, forty-five (45) degrees, to rocker 20.
[0031] Frame members 24a, 24b are substantially identical. As best
shown in FIG. 3, wherein only frame member 24b is shown for the
sake of clarity, each of frame members 24a, 24b define a respective
frame rocker orifice 36a, 36b and a respective frame shaft orifice
38a, 38b. Each frame rocker orifice 36a, 36b receives a
corresponding portion of rocker 20 to thereby pivotally associate
frame members 24a, 24b and rocker 20 such that rocker 20 is free to
undergo oscillatory movement relative to frame members 24a, 24b and
about rocker axis R, and be carried by frame members 24a, 24b
during pivotal movement thereof relative to central axis A of input
shaft 16. Each frame shaft orifice 38a, 38b receives a
corresponding portion of input shaft 16 to thereby pivotally
associate frame members 24a, 24b and input shaft 16 such that frame
members 24a, 24b are free to pivot relative to central axis A and
yet are not rotated by the rotation of input shaft 16. Each of
frame members 24a, 24b further include a respective bearing support
portion 42a, 42b (see FIG. 1). Bearing support portions 42a, 42b
surround a respective one of frame rocker orifices 36a, 36b, and
are substantially cylindrical in shape. Bearing support portions
42a, 42b are affixed, such as, for example, welded, to or formed
integrally with frame members 24a, 24b. Frame member 24a is
disposed on a first side (not referenced) of connecting rod 22
while frame member 24b is disposed on the opposite side of
connecting rod 22.
[0032] Drum sleeves 26a, 26b are affixed to respective ends of
rocker 20. More particularly, drum sleeve 26a is disposed upon
rocker 20 generally adjacent bearing support 42a, and drum sleeve
26b is disposed upon rocker 20 generally adjacent bearing support
42b. Each of drum sleeves 26a, 26b are affixed, such as, for
example welded, bolted or otherwise secured by suitable means, to
rocker 20. The outer surfaces (not referenced) of drum sleeves 26a,
26b are configured for engaging an inside surface (not referenced)
of a respective belt 28a, 28b.
[0033] Belts 28a, 28b are disposed around and engage a portion of
the outside surface (not referenced) of drum sleeves 26a, 26b,
respectively. Belts 28a, 28b also engage respective surfaces of
output cams 30a, 30b, respectively, as will be more particularly
described hereinafter. Belts 28a, 28b are each fastened to output
cams 30a, 30b by belt fasteners 52a, 52b, respectively, such as,
for example, clamps, bolts, pins, screws, rivets, roll pins or
other suitable fasteners. Similarly, belts 28a, 28b are each
fastened to drum sleeves 26a, 26b, respectively, by fasteners 54a,
54b, such as, for example, clamps, bolts, pins, screws, rivets,
roll pins or other suitable fasteners. Belts 28a, 28b are
constructed of, for example, metal, reinforced rubber, or other
suitable material.
[0034] Output cams 30a, 30b are pivotally mounted upon input shaft
16, generally adjacent a respective frame member 24a, 24b. Output
cams 30a, 30b are not rotated by rotation of input shaft 16, but
are rather free to pivot relative to central axis A thereof. Output
cams 30a, 30b each include belt engaging surfaces 56a, 56b, such
as, for example, substantially cylindrical surfaces. Belt engaging
surfaces 56a, 56b are affixed to or integral with a respective
output cam 30a, 30b. Each of output cams 30a, 30b are associated
with a respective roller finger follower (RFF) 60a, 60b. More
particularly, the outer surface (not referenced) or of output cams
30a, 30b engage rollers 62a, 62b, respectively, of a corresponding
RFF 60a, 60b. As will be understood by one skilled in the art, the
outer surfaces of output cams 30a, 30b define a lift profile which
includes a base circle portion and a lift portion (neither of which
is referenced).
[0035] In use, valves 12a, 12b are actuated by VVA mechanism 10 in
accordance with the lift profile of the portion of the outer
surfaces of output cams 30a, 30b that engage rollers 62a, 62b,
respectively, as output cams 30a, 30b oscillate through the
predetermined range of oscillation. The oscillation of output cams
30a, 30b, and the portion of the outer surfaces thereof that engage
rollers 62a, 62b, respectively, cause RFFs 60a, 60b to pivot about
lash adjusters 68a, 68b, respectively, and actuate a corresponding
one of valves 12a, 12b.
[0036] More particularly, and as stated above, input shaft 16 is
driven to rotate relative to central axis A thereof in timed
relation to the crankshaft (not shown) of engine 14. Connecting rod
22 transfers rotation of input shaft 16 and eccentric 16a to
oscillatory movement of rocker 20 within frame members 24a, 24b and
relative to central axis R. Input eccentric 16a is configured to
impart to rocker 20 a fixed range or degree of oscillation, such
as, for example, forty-five (45) degrees. Drum sleeves 26a, 26b are
affixed to rocker 20, and thus drum sleeves 26a, 26b oscillate as
substantially one body with rocker 20. Belts 28a, 28b are secured
to drum sleeves 26a, 26b, respectively, by belt fasteners 54a, 54b,
respectively, and to output cams 30a, 30b, respectively, by belt
fasteners 52a, 52b, respectively, and transfer the oscillation of
drum sleeves 26a, 26b to corresponding oscillatory movement of
output cams 30a, 30b.
[0037] The valve lift profile of valves 12a, 12b is selected, and
varied, dependent at least in part upon the angular position of
control shaft 18. As stated above, control shaft 18 is coupled by
shaft couplers 18a, 18b to frame members 24a, 24b, respectively.
Thus, as control shaft 18 is pivoted relative to central axis S
thereof frame members 24a, 24b are, in turn, pivoted relative to
central axis A of input shaft 16. Frame members 24a, 24b carry
rocker 20, and thus the pivoting of frame members 24a, 24b relative
to central axis A, in turn, pivots center axis R of rocker 20
relative to central axis A of input shaft 16. Drum sleeves 26a, 26b
are affixed to rocker 20, and thus pivoting of center axis R of
rocker 20 relative to central axis A of input shaft 16 is
transferred to pivotal movement of drum sleeves 26a, 26b relative
to central axis A. The pivoting of drum sleeves 26a, 26b relative
to central axis A is transferred to pivoting of output cams 30a,
30b relative to central axis A by belts 28a, 28b, respectively.
Thus, the angular position of control shaft 18 relative to central
axis S thereof determines the angular relation of output cams 30a,
30b relative to central axis A and relative to rollers 62a, 62b of
RFFs 60a, 60b, respectively, thereby determining the portion of the
lift profile of output cams 30a, 30b which engage rollers 62a, 62b
during the fixed angular range of oscillation of output cams 30a,
30b. The portion of the lift profile of output cams 30a, 30b which
engage rollers 62a, 62b, in turn, determines the valve lift profile
of valves 12a, 12b.
[0038] For example, a relatively high amount of valve lift is
obtained by placing the lift portion of the lift profile of output
cams 30a, 30b well within the fixed angular range of oscillation
thereof. Thus, as output cams 30a, 30b are oscillated, at least a
substantial portion of the lift portion of the lift profile thereof
engages rollers 62a, 62b, respectively, and impart a
correspondingly high amount of lift to valves 12a, 12b. Conversely,
and as a second example, a relatively low amount of or
substantially no valve lift is obtained by placing the lift portion
of the valve lift profile of output cams 30a, 30b only partially
within or substantially entirely outside the fixed angular range of
oscillation thereof. Thus, as output cams 30a, 30b are oscillated,
only a small portion of the lift portion or only the base circle
portion of the lift profile thereof engages rollers 62a, 62b,
respectively, and impart a correspondingly small amount of lift to
valves 12a, 12b.
[0039] As stated above, connecting rod 22 is coupled by rod coupler
22a to rocker 20. As control shaft 18 is pivoted relative to
central axis S thereof, thereby causing frame members 24a, 24b and
central axis R of rocker 20 to pivot relative to central axis A,
rocker 20 itself pivots relative to its own center axis R within
frame members 24a, 24b. With input shaft 16 rotating, for example,
in a clockwise direction, the pivoting of rocker relative to its
center axis R advances the timing of the actuation of valves 12a,
12b with VVA mechanism 10 in a low-lift position relative to the
timing of the actuation of valves 12a, 12b with VVA mechanism 10 in
a high-lift position.
[0040] In the embodiment shown, belts 28a, 28b are configured as
cylindrical and/or continuous belts. However, it is to be
understood that belt-driven VVA mechanism 10 can be alternately
configured, such as, for example, with non-continuous and/or
non-cylindrical belts. A second embodiment of a belt-driven VVA
mechanism of the present invention is shown in FIGS. 5 and 6, in
which the same reference characters used in referring to component
parts of belt-driven WA mechanism 10 have been used to indicate
corresponding parts. Belt-drive VVA mechanism 110 includes a
cross-over belt 128a which transfers oscillatory movement of rocker
20 (not shown) and drum sleeve 26a to oscillation of output cam
30a. As best shown in FIG. 6, belt 128a includes a first portion
130a and a second portion 130b. First portion 130a defines a
longitudinal slot 132a therethrough. Belt fasteners 152a, 152b and
154a, such as, for example, pins or rivets, affix belt 128a to
output cam 32a and drum sleeve 26a, respectively. More
particularly, belt 128a is affixed at one end to the base circle
portion of the lift profile of output cam 30a by fastener 152a.
Belt 128a the wraps around drum sleeve 26a and is fastened thereto
by fastener 154a, passes through slot 132 and is fastened at the
other end by fastener 152b to output cam 30a.
[0041] In the embodiments shown, output cams 30a, 30b each include
belt-engaging surfaces 56a, 56b. Similarly, the outer surfaces (not
referenced) of drum sleeves 26a, 26b are configured for engaging an
inside surface (not referenced) of a respective belt 28a, 28b, and
are thus also belt-engaging surfaces. Each pair of belt-engaging
surfaces, i.e., surfaces 56a, 56b and the belt-engaging surfaces of
drum sleeves 26a, 26b, are configured as, for example,
substantially cylindrical surfaces. However, it is to be understood
that one or both pairs of belt-engaging surfaces 56a, 56b and of
drum sleeves 26a, 26b can be alternately configured, such as, for
example, with an elliptical, eccentric or various other shape. It
should be particularly noted that, by varying the shapes of at
least one pair of the belt-engaging surfaces, such as, for example,
belt-engaging surfaces 56a, 56b, certain benefits can be obtained.
For example, to obtain a more desirable low-lift valve lift profile
at least one pair of the belt-engaging surfaces is configured with
an elliptical shape to thereby decrease the duration of the lift
and obtain low ratio of valve lift to lift duration. The valve lift
profile therefore has a sharper peak and is less flat. Thus, VVA
mechanism 10 is configurable to meet various application-specific
requirements by providing a family of valve lift profiles.
[0042] It should be further particularly noted that the diameter of
the belt-engaging surfaces 56a, 56b and of drum sleeves 26a, 26b
are similarly modified from the embodiments shown to obtain certain
benefits. For example, by configuring the belt-engaging surfaces of
the drum sleeves to have a relatively large diameter relative to
the belt-engaging surfaces of the output cams, a relatively small
or slight degree of oscillation of rocker 20 and, thus, of the
relatively large-diameter belt-engaging surfaces of the drum
sleeves results in an relatively large or magnified degree of
oscillation of the small-diameter belt-engaging surfaces of the
output cams. Thus, substantially less oscillation of rocker 20 is
required in order to oscillate the output cams through a fixed
angle or range of oscillation when the output cams are configured
with relatively small diameter belt-engaging surfaces relative to
the belt-engaging surfaces of the drum sleeves.
[0043] In the embodiments shown, VVA mechanism 10 is configured
without means for lash adjustment. However, it is to be understood
that VVA mechanism 10 can be alternately configured to include lash
adjustment means, such as, for example, belt tensioning means to
adjust tension and/or slack of the belts and thereby substantially
remove and/or compensate for lash.
[0044] In the embodiments shown, VVA mechanism 10 includes two
frame members 24a, 24b and two output cams 30a, 30b, to thereby
actuate dual inlet valves 12a, 12b of a corresponding cylinder of
engine 14. However, it is to be understood that VVA mechanism 10
can be alternately configured, such as, for example, for use with a
cylinder having only one inlet valve. In this embodiment, the VVA
mechanism includes a single frame member and a single output
cam.
[0045] In the embodiments shown, a single VVA mechanism 10 is
associated with one cylinder (not shown) of engine 14. However, it
is to be understood that multiple WA mechanisms of the present
invention can be associated with each cylinder of an engine, and be
operable to variably actuate the intake and/or exhausts valves
thereof.
[0046] In the embodiment shown, frame members 24a, 24b are
pivotally mounted upon input shaft 16. However, it is to be
understood that VVA mechanism 10 can be alternately configured,
such as, for example, having frame members mounted to a secondary
shaft or other structure and still being configured for pivotal
movement relative to the central axis of the input shaft or
relative to a central axis of the secondary shaft.
[0047] In the embodiment shown, WA mechanism 10 is configured for
use with an internal combustion engine. However, it is to be
understood that VVA mechanism 10 can be alternately configured,
such as, for example, for use with various other mechanisms or
machinery which require may advantageously utilize variable
displacement, duration and/or timing of one or more moving
components.
[0048] 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.
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