U.S. patent application number 15/285512 was filed with the patent office on 2018-04-05 for variable camshaft.
The applicant listed for this patent is GM GLOBAL TECHNOLOGY OPERATIONS LLC. Invention is credited to Domenic Certo, Bradley R Kaan, Joseph J. Moon.
Application Number | 20180094554 15/285512 |
Document ID | / |
Family ID | 61623429 |
Filed Date | 2018-04-05 |
United States Patent
Application |
20180094554 |
Kind Code |
A1 |
Kaan; Bradley R ; et
al. |
April 5, 2018 |
VARIABLE CAMSHAFT
Abstract
A variable camshaft includes a base shaft, an axially movable
structure, and an actuator. The axially movable structure includes
a plurality of lobe packs and at least one barrel cam defining a
control groove having an engagement region, a first shift region, a
balancing region, a second shift region and a disengagement region.
The actuator includes at least one pin operatively configured to
move relative to the actuator body between a retracted position and
an extended position into the control groove. The axially movable
structure moves axially relative to the base shaft the pin is in
the extended position and is at least partially disposed in one of
the first or second shift regions of the control groove.
Inventors: |
Kaan; Bradley R;
(Ortonville, MI) ; Moon; Joseph J.; (Beverly
Hills, MI) ; Certo; Domenic; (Niagra Falls,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GM GLOBAL TECHNOLOGY OPERATIONS LLC |
Detroit |
MI |
US |
|
|
Family ID: |
61623429 |
Appl. No.: |
15/285512 |
Filed: |
October 5, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01L 1/053 20130101;
F01L 2800/08 20130101; F01L 2013/101 20130101; F01L 1/34 20130101;
F01L 2013/0052 20130101; F01L 1/047 20130101; F01L 13/0036
20130101 |
International
Class: |
F01L 1/34 20060101
F01L001/34; F01L 1/047 20060101 F01L001/047 |
Claims
1. A variable camshaft comprising: a base shaft; an axially movable
structure mounted on the base shaft, the axially movable structure
being axially movable relative to the base shaft and being
rotationally fixed to the base shaft, wherein the axially movable
structure includes a plurality of lobe packs and at least one
barrel cam defining a control groove having an engagement region, a
first shift region, a balancing region, a second shift region and a
disengagement region having a disengagement catch wall; an actuator
including an actuator body and at least one pin movably coupled to
the actuator body, the at least one pin being configured to move
relative to the actuator body between a retracted position and an
extended position; and wherein the axially movable structure is
configured to move axially relative to the base shaft when the base
shaft rotates about a longitudinal axis and the at least one pin is
in the extended position and at least partially disposed in one of
the first or second shift regions of the control groove.
2. The variable camshaft as defined in claim 1 wherein the
balancing region is defined in the control groove between the first
and second shift regions.
3. The variable camshaft as defined in claim 2 wherein the at least
one pin is operatively configured to be axially stationary in the
balancing region.
4. The variable camshaft as defined in claim 3 wherein the first
shift region defines a first push wall operatively configured to
engage with the at least one pin thereby moving the axially
moveable structure along the base shaft.
5. The variable camshaft as defined in claim 4 wherein the
balancing region defines an outer catch wall operatively configured
to engage with the pin upon impact, the outer catch wall having a
thickness greater than the thickness of the disengagement catch
wall.
6. The variable camshaft as defined in claim 4 wherein the second
shift region defines a second push wall operatively configured to
engage with the at least one pin thereby moving the axially
moveable structure along the base shaft.
7. The variable camshaft as defined in claim 6 wherein a first
entry area is defined where the engagement region transitions into
the first shift region.
8. The variable camshaft as defined in claim 7 wherein a second
entry area is defined where the balancing region transitions into
the second shift region.
9. The variable camshaft as defined in claim 8 wherein the outer
catch wall is operatively configured to engage with the at least
one pin in order to stop the axial movement of the axially moveable
structure relative to the base shaft while the pin travels straight
through the balancing region.
10. A variable camshaft comprising: a base shaft; an axially
movable structure mounted on the base shaft, the axially movable
structure being axially movable relative to the base shaft and
being rotationally fixed to the base shaft, wherein the axially
movable structure includes at least one barrel cam defining a
control groove having a first shift region, a balancing region
having an outer catch wall, a second shift region, and a
disengagement region having a disengagement catch wall; an actuator
including an actuator body and at least one pin movably coupled to
the actuator body, the at least one pin being configured to move
relative to the actuator body between a retracted position and an
extended position; and wherein the axially movable structure is
configured to move axially relative to the base shaft when the base
shaft rotates about a longitudinal axis and the at least one pin is
in the extended position and at least partially disposed in one of
the first or second shift regions of the control groove.
11. The variable camshaft as defined in claim 10 wherein the
balancing region is defined in the control groove between the first
and second shift regions, the balancing having an outer catch wall
thickness which is greater than a thickness of the disengagement
catch wall.
12. The variable camshaft as defined in claim 11 wherein the at
least one pin is operatively configured to be axially stationary in
the balancing region.
13. The variable camshaft as defined in claim 11 wherein the first
shift region defines a first push wall operatively configured to
engage with the at least one pin thereby moving the axially
moveable structure along the base shaft.
14. The variable camshaft as defined in claim 13 wherein the
disengagement region of the control groove defines a disengagement
catch wall.
15. The variable camshaft as defined in claim 14 wherein the second
shift region defines a second push wall operatively configured to
engage with the at least one pin thereby moving the axially
moveable structure further along the base shaft.
16. The variable camshaft as defined in claim 15 wherein the outer
catch wall and the disengagement catch wall are operatively
configured to engage with the at least one pin in order to stop the
axial movement of the axially moveable structure relative to the
base shaft.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to vehicle engines and more
particularly, variable camshafts for vehicle engines.
BACKGROUND
[0002] Some internal combustion engines include an adjustable or
slideable camshaft assembly. The camshaft assembly includes a base
camshaft that is rotatable about a cam axis. An axially moveable
structure (which includes a lobe pack) is slideably attached to the
camshaft for axial movement along the cam axis relative to the
camshaft. The lobe pack is rotatable with the camshaft about the
cam axis. The lobe pack is moveable between at least two different
axial positions along the cam axis. Each different position of the
lobe pack presents a different cam lobe having a different lobe
profile for engaging a respective valve stem of the engine.
Accordingly, by adjusting the position of the lobe pack, the cam
profile that each valve stem of the engine follows may be
changed.
[0003] The lobe pack includes a barrel cam 114 (shown in FIG. 1)
that defines a control groove 118 disposed annularly about the cam
axis 140. A first shifting pin 116 is moveable in a direction 123
transverse to the cam axis 140. The first shifting pin 116 moves
between an engaged position (shown in FIG. 1A) and a disengaged
position (shown in FIG. 1B). When disposed in the engaged position,
the first shifting pin 116 is engaged with the control groove 118,
such that interaction between the first shifting pin 116 and the
control groove 118 moves an axially moveable structure (shown
schematically as element 120) which includes the lobe pack axially
along the cam axis 140 relative to the base shaft 128, in a first
axial direction 134 and into a first axial position, as the axially
moveable structure/lobe pack 120 rotates about the cam axis 140
with the base shaft 128. Similarly, a second shifting pin (not
shown) may be moveable in a direction transverse to the cam axis
140. The second shifting pin moves between an engaged position and
a disengaged position. When disposed in the engaged position, the
second shifting pin may be engaged with the control groove 118,
such that interaction between the second shifting pin and the
control groove 118 moves the axially moveable structure 120 (having
the lobe packs) axially along the cam axis 140 relative to the
camshaft 126, in a second axial direction 135 and into a second
axial position, as the lobe pack rotates about the cam axis 140
with the camshaft 126. When disposed in their respective disengaged
positions, the first shifting pin 116 and the second shifting pin
are disengaged from the control groove 118 such that the axially
moveable structure 120 remains positionally fixed along the cam
axis 140, relative to the base shaft 128, as the axially movable
structure/lobe pack 120 rotates about the cam axis 140 with the
base shaft 128. The axially moveable structure 120 having a lobe
pack may remain positionally fixed relative to the camshaft 126 via
an interlocking detent ball and detent groove retention mechanism
disposed on the lobe pack and the base shaft 128 respectively.
[0004] During normal operation, the base shaft 128 and the axially
movable structure/lobe pack 120 only rotate about the cam axis 140
in a first rotational direction. The control groove 118 is shaped
to engage the first shifting pin 116 and the second shifting pin
(not shown), to guide the axially movable structure/lobe pack 120
between the first axial position and the second axial position
along the cam axis 140 respectively, when the base shaft 128 and
the axially movable structure/lobe pack 120 are rotating in the
first rotational direction. However, the wall 132 in the ejection
region 130 of the control groove 118 may experience failure due to
the loads that either the first or second shifting pin imposes on
the barrel cam wall 132 when the pin 116 transitions from the
engagement groove 122 through the shifting groove 124 and into the
ejection groove 130. It is understood that design constraints limit
the width of the barrel cam 114. Therefore, the relative axial
movement of the pin 116 to the barrel cam--from the first position
to the second position imposes significant loads on the outer wall
132 of the barrel cam 114. As shown in FIGS. 1A-1B, the outer wall
132 in the ejection region 130 of the control groove 118 is rather
thin due to the required axial movement and the design constraints
for the barrel cam width. Accordingly, the outer wall 132 may be
prone to failure when the pin 116 moves to the ejection groove and
engages with the outer wall in the ejection groove.
[0005] Accordingly, there is a need for an improved camshaft
assembly which can sustain significant loads resulting from the
engagement between barrel cam 114 and the actuator pin 116.
SUMMARY
[0006] The present disclosure provides a variable camshaft having a
base shaft, an axially movable structure, and an actuator. The
axially movable structure includes a plurality of lobe packs and at
least one barrel cam defining a control groove having an engagement
region, a first shift region, a balancing region, a second shift
region and a disengagement region. The actuator includes at least
one pin operatively configured to move relative to the actuator
body between a retracted position and an extended position into the
control groove. The axially movable structure moves axially
relative to the base shaft the pin is in the extended position and
is at least partially disposed in one of the first or second shift
regions of the control groove.
[0007] The invention and its particular features and advantages
will become more apparent from the following detailed description
considered with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] These and other features and advantages of the present
disclosure will be apparent from the following detailed description
of preferred embodiments, and best mode, appended claims, and
accompanying drawings in which:
[0009] FIG. 1A shows a prior art barrel cam on a base shaft where
the first shifting pin is in the engagement position.
[0010] FIG. 1B illustrates the prior art barrel cam of FIG. 1A
where the first shifting pin is in the disengagement position.
[0011] FIG. 2 illustrates a schematic diagram of a vehicle
including an engine assembly.
[0012] FIG. 3 illustrates a schematic side view of a portion of the
camshaft assembly and two engine cylinders where the lobe packs of
the camshaft assembly are in a first position.
[0013] FIG. 4 illustrates a schematic side view of a portion of the
camshaft assembly and two engine cylinders where the lobe packs of
the camshaft assembly are in a second position.
[0014] FIG. 5 illustrates a schematic diagram showing the various
regions of the control groove for the camshaft of the present
disclosure.
[0015] FIG. 6A illustrates a first shifting pin in an engagement
region in the camshaft of the present disclosure.
[0016] FIG. 6B illustrates a first shifting pin in a balancing
region in the camshaft of the present disclosure.
[0017] FIG. 6C illustrates a first shifting pin in an ejection
region in the camshaft of the present disclosure.
[0018] Like reference numerals refer to like parts throughout the
description of several views of the drawings.
DETAILED DESCRIPTION
[0019] The exemplary embodiments described herein provide detail
for illustrative purposes, and are subject to many variations in
composition, structure, and design. It is understood that various
omissions and substitutions of equivalents are contemplated as
circumstances may suggest or render expedient, but these are
intended to cover the application or implementation without
departing from the spirit or scope of the claims of the present
disclosure. Also, it is to be understood that the phraseology and
terminology used herein are for the purpose of description and
should not be regarded as limiting.
[0020] Those having ordinary skill in the art will recognize that
terms such as "above," "below," "upward," "downward," "top,"
"bottom," etc., are used descriptively for the figures, and do not
represent limitations on the scope of the disclosure, as defined by
the appended claims. Furthermore, the disclosure may be described
herein in terms of functional and/or logical block components
and/or various processing steps. It should be realized that such
block components may be comprised of any number of hardware,
software, and/or firmware components configured to perform the
specified functions.
[0021] Referring to the drawings, wherein like reference numbers
correspond to like or similar components throughout the several
figures, FIG. 2 schematically illustrates a vehicle 10 such as a
car, truck or motorcycle. The vehicle 10 includes an engine
assembly 12. The engine assembly 12 includes an internal combustion
engine 14 and a control module 16, such an engine control module
(ECU), in electronic communication with the internal combustion
engine 14. The terms "control module," "module," "control,"
"controller," "control unit," "processor" and similar terms mean
any one or various combinations of one or more of Application
Specific Integrated Circuit(s) (ASIC), electronic circuit(s),
central processing unit(s) (preferably microprocessor(s)) and
associated memory and storage (read only, programmable read only,
random access, hard drive, etc.) executing one or more software or
firmware programs or routines, combinational logic circuit(s),
sequential logic circuit(s), input/output circuit(s) and devices,
appropriate signal conditioning and buffer circuitry, and other
components to provide the described functionality. The control
module 16 may have a set of control routines executed to provide
the desired functions. Routines are executed, such as by a central
processing unit, and are operable to monitor inputs from sensing
devices and other networked control modules, and execute control
and diagnostic routines to control operation of actuators. Routines
may be executed based on events or at regular intervals.
[0022] The internal combustion engine 14 includes an engine block
18 defining a plurality of cylinders 20A, 20B, 20C, and 20D. In
other words, the engine block 18 includes a first cylinder 20A, a
second cylinder 20B, a third cylinder 20C, and a fourth cylinder
20D. Although FIG. 1 schematically illustrates four cylinders, the
internal combustion engine 14 may include more or fewer cylinders.
The cylinders 20A, 20B, 20C, and 20D are spaced apart from each
other but may be substantially aligned along an engine axis E. Each
of the cylinders 20A, 20B, 20C, and 20D is configured, shaped and
sized to receive a piston (not shown). The pistons are configured
to reciprocate within the cylinders 20A, 20B, 20C, and 20D. Each
cylinder 20A, 20B, 20C, 20D defines a corresponding combustion
chamber 22A, 22B, 22C, 22D. During operation of the internal
combustion engine 14, an air/fuel mixture is combusted inside the
combustion chambers 22A, 22B, 22C, and 22D in order to drive the
pistons in a reciprocating manner. The reciprocating motion of the
pistons drives a crankshaft (not shown) operatively connected to
the wheels (not shown) of the vehicle 10. The rotation of the
crankshaft can cause the wheels to rotate, thereby propelling the
vehicle 10.
[0023] In order to propel the vehicle 10, an air/fuel mixture
should be introduced into the combustion chambers 22A, 22B, 22C,
and 22D. To do so, the internal combustion engine 14 includes a
plurality of intake ports 24 fluidly coupled to an intake manifold
(not shown). In the depicted embodiment, the internal combustion
engine 14 includes two intake ports 24 in fluid communication with
each combustion chamber 22A, 22B, 22C, and 22D. However, the
internal combustion engine 14 may include more or fewer intake
ports 24 per combustion chamber 22A, 22B, 22C, and 22D. The
internal combustion engine 14 includes at least one intake port 24
per cylinder 20A, 20B, 20C, 20D.
[0024] The internal combustion engine 14 further includes a
plurality of intake valves 26 configured to control the flow of
inlet charge through the intake ports 24. The number of intake
valves 26 corresponds to the number of intake ports 24. Each intake
valve 26 is at least partially disposed within a corresponding
intake port 24. In particular, each intake valve 26 is configured
to move along the corresponding intake port 24 between an open
position and a closed position. In the open position, the intake
valve 26 allows inlet charge to enter a corresponding combustion
chamber 22A, 22B, 22C, or 22D via the corresponding intake port 24.
Conversely, in the closed position, the intake valve 26 precludes
the inlet charge from entering the corresponding combustion chamber
22A, 22B, 22C, or 22D via the intake port 24.
[0025] As discussed above, the internal combustion engine 14 can
combust the air/fuel mixture once the air/fuel mixture enters the
combustion chamber 22A, 22B, 22C, or 22D. For example, the internal
combustion engine 14 can combust the air/fuel mixture in the
combustion chamber 22A, 22B, 22C, or 22D using an ignition system
(not shown). This combustion generates exhaust gases. To expel
these exhaust gases, the internal combustion engine 14 defines a
plurality of exhaust ports 28. The exhaust ports 28 are in fluid
communication with the combustion chambers 22A, 22B, 22C, or 22D.
In the depicted embodiment, two exhaust ports 28 are in fluid
communication with each combustion chamber 22A, 22B, 22C, or 22D.
However, more or fewer exhaust ports 28 may be fluidly coupled to
each combustion chamber 22A, 22B, 22C, or 22D. The internal
combustion engine 14 includes at least one exhaust port 28 per
cylinder 20A, 20B, 20C, or 20D.
[0026] The internal combustion engine 14 further includes a
plurality of exhaust valves 30 in fluid communication with the
combustion chambers 22A, 22B, 22C, or 22D. Each exhaust valve 30 is
at least partially disposed within a corresponding exhaust port 28.
In particular, each exhaust valve 30 is configured to move along
the corresponding exhaust port 28 between an open position and a
closed position. In the open position, the exhaust valve 30 allows
the exhaust gases to escape the corresponding combustion chamber
22A, 22B, 22C, or 22D via the corresponding exhaust port 28. The
vehicle 10 may include an exhaust system (not shown) configured to
receive and treat exhaust gases from the internal combustion engine
14. In the closed position, the exhaust valve 30 precludes the
exhaust gases from exiting the corresponding combustion chamber
22A, 22B, 22C, or 22D via the corresponding exhaust port 28.
[0027] As discussed in detail below, intake valve 26 and exhaust
valve 30 can also be generally referred to as engine valves 66
(FIGS. 3-4) or simply valves. Each valve 66 (FIGS. 3-4) is
operatively coupled or associated with a cylinder 20A, 20B, 20C, or
20D (shown in FIG. 2). Accordingly, the valves 66 (FIGS. 3-4) are
configured to control fluid flow (i.e., air/fuel mixture for intake
valves 26 and exhaust gas for exhaust valve 30 to the corresponding
cylinder 20A, 20B, 20C, or 20D. The valves 66 operatively coupled
to the first cylinder 20A can be referred to as first valves. The
valves 66 operatively coupled to the second cylinder 20B can be
referred to as second valves. The valves 66 operatively coupled to
the third cylinder 20C can be referred to as third valves. The
valves 66 operatively coupled to the fourth cylinder 20D can be
referred to as fourth valves.
[0028] As shown in FIG. 2, the engine assembly 12 further includes
a valvetrain system 32 configured to control the operation of the
intake valves 26 and exhaust valves 30. Specifically, the
valvetrain system 32 can move the intake valves 26 and exhaust
valves 30 between the open and closed positions based at least in
part on the operating conditions of the internal combustion engine
14 (e.g., engine speed). The valvetrain system 32 includes one or
more camshaft assemblies 33 substantially parallel to the engine
axis E. In the depicted embodiment, the valvetrain system 32
includes two camshaft assemblies 33. One camshaft assembly 33 is
configured to control the operation of the intake valves 26, and
the other camshaft assembly 33 can control the operation of the
exhaust valves 30. It is contemplated, however, that the valvetrain
system 32 may include more or fewer camshaft assemblies 33.
[0029] In addition to the camshaft assemblies 33, the valvetrain
assembly 32 may include a plurality of actuators 34A, 34B, 34C,
34D, such as solenoids, in communication with the control module
16. Note that two additional actuators (not shown) may be
implemented for the exhaust lobe on second cylinder and for the
exhaust lobe on the third cylinder. The actuators 34A, 34B may be
electronically connected to the control module 16 and may therefore
be in electronic communication with the control module 16. The
control module 16 may be part of the valvetrain system 32. In the
depicted embodiment, the valvetrain system 32 includes first,
second, third, and fourth actuators 34A, 34B, 34C, 34D. The first
actuator 34A is operatively associated with the first and second
cylinders 20A, 20B and can be actuated to control the operation of
the intake valves 26 of the first and second cylinders 20A, 20B.
The second actuator 34B is operatively associated with the first
and second cylinders 20A, 20B and can be actuated to control the
operation of the intake valves 26 of the first and second cylinders
20A, 20B. The third and fourth actuators 34C and 34D is operatively
associated with the third and fourth cylinders 20C and 20D and can
be actuated to control the operation of the intake valves 26 of the
third and fourth cylinders 20C and 20D. The fifth actuator 34E is
operatively associated with the second cylinder 20B and can be
actuated to control the operation of the exhaust valves 30 of the
second cylinder 20B. The sixth actuator 34F is operatively
associated with the third cylinders 20C and can be actuated to
control the operation of the exhaust valves 30 of the third
cylinders 20C. The actuators 34A, 34B, 34C, 34D, 34E, 34F and
control module 16 may be deemed part of the camshaft assembly
33.
[0030] With reference to FIG. 3, the camshaft assembly 33 includes
at least one axially movable structure 44 with lobe packs 46A, 46B,
46C, 46D. Though FIG. 3 shows only one axially movable structure
44, it is contemplated that the camshaft assembly 33 may include
more axially movable structures 44. The first and second lobe packs
46A, 46B are operatively associated with one cylinder 20A of the
engine 14 (FIG. 1), while the third lobe pack 46C is operatively
associated with another cylinder 20B of the engine 14. The axially
movable structure 44 may also include more or fewer than four lobe
packs 46A, 46B, 46C, 46D. Regardless of the number of lobe packs,
each axially movable structure 44 may, but not necessarily, have a
single barrel cam 56. Accordingly, the camshaft assembly 33 may
only include one barrel cam 56 for every two cylinders 20A, 20B.
Because the barrel cam 56 interacts with one actuator 34A to move
the axially movable structure 44 relative to the base shaft 35, the
camshaft assembly 33 may only include a single actuator 34A (or
34B) for every two cylinders 20A, 20C. In other words, the camshaft
assembly 33 may have a single actuator 34A for every two cylinders
20A, 20B. With the illustrated control groove configuration, it is
useful to have only two barrel cams 56A and 56B used in conjunction
with corresponding actuators 34A and 34B for every two cylinders
20A, 20B.
[0031] As discussed above, the first, second, third, and fourth
lobe packs 46A, 46B, 46C, 46D each include one group of cam lobes
50. Each group of cam lobes 50 may include a first cam lobe 54A, a
second cam lobe 54B, and a third cam lobe 54C. The first cam lobe
54A may have a first maximum lobe height H1. The second cam lobe
54B has a second maximum lobe height H2. The third cam lobe 54C has
a third maximum lobe height H3. The first, second, and third
maximum lobe heights H1, H2, H3 may be different from one another.
It is understood that while three cam lobes per group 50 are
illustrated in the present non-limiting example, the variable
camshaft 33 of the present disclosure may have two or more cam
lobes per group.
[0032] Referring back to the embodiment depicted in FIG. 3, the
first, second, and third cam lobes 54A, 54B, 54C of the first and
second lobe packs 46A, 46B have different maximum lobe heights, but
the first and second cam lobes 54A, 54B of the third lobe pack 46C
have the same maximum lobe heights. In other words, the first
maximum lobe height H1 may be equal to the second maximum lobe
height H2. Alternatively, the first maximum lobe height H1 may be
different from the second maximum lobe height H2. Accordingly, it
is understood that it is entirely possible for the first, second
and third cam lobes 54A, 54B, 54C to have different lifts on lobe
packs 46A, 46B, 46C, and 46D due different lift heights H1, H2, H3.
Referring back to the figures, the maximum lobe heights of the cam
lobes 54A, 54B, 54C corresponds to the valve lift of the intake and
exhaust valves 26, 30. The camshaft assembly 33 can adjust the
valve lift of the intake and exhaust valves 26, 30 by adjusting the
axial position of the cam lobes 54A, 54C, 54D relative to the base
shaft 35. This can include a zero lift cam profile if desired. The
cam lobes 54A, 54B, 54C of each group of cam lobes 50 are disposed
in different axial positions along the longitudinal axis X.
[0033] With reference to FIGS. 3-4, the lobe packs 46A, 46B, 46C,
46D can move relative to the base shaft 35 between a first position
(FIG. 3), and a second position (FIG. 4) via the shifting pin 64A
or 64B and the control groove 60A defined in barrel cam 56A. To do
so, the barrel cam 56A physically interacts with the actuator 34A
which causes the axially moveable structure 44 to move in direction
210 Similarly, actuator 34B with shifting pin 64C or 64D engage
with the control groove 60B defined in barrel cam 56B which causes
the axially moveable structure to move in the opposite direction
212. As discussed above, the barrel cams 56A, 56B each include a
barrel cam body 58 and defines a control groove 60A, 60B extending
into the barrel cam body 58. The control groove 60A, 60B is
elongated along at least a portion of the circumference of the
respective barrel cam 56A, 56B.
[0034] Referring now to FIG. 5 and FIGS. 6A-6C, the barrel cam 56
of the present disclosure defines a control groove 60 in the barrel
cam 56 as shown. For purposes of the FIGS. 5, 6A-6C, pin 64 may be
either first pin 64A or pin 64B (shown in FIGS. 3 and 4). In the
non-limiting example shown in FIG. 5, various regions of the
control groove 60 are shown. Such regions include: (1) pin
engagement region 62; (2) first shift region 63; (3) balancing
region 66; (4) second shifting region 68; and (5) disengagement
region 70. The camshaft 33 of the present disclosure therefore
includes a barrel cam 56 which may include two shifting
regions--first shift region 63 and second shift region 68. The goal
of the two-step design using two shifting regions is to reduce the
loads 82 imposed on outer wall 86 of the control groove 60 wall
(after the pin 64 travels through the first shifting region 63)
thereby enhancing product durability.
[0035] The general idea of the present disclosure is that the
actuator pin 64 will enter the control groove 60 in the pin
engagement region 62 and the lobe pack (and the axially moveable
structure shown schematically as 44) will shift when the pin 64
contacts the `first push wall` 72) at a first entry area 76 and
then travels through the first shift region 63. It is understood
that the first entry area 76 is the area where the engagement
region 62 transitions into the first shift region 63. After
completing travel through the first shift region 63, the pin enters
the balancing region 66 and may impact the outer catch wall 86 in
the balancing region. As shown in FIG. 6B, the thickness 88 of the
outer catch wall 86 is relatively substantial such that the outer
catch wall 86 has a thickness 88 which is greater than the
disengagement catch wall thickness 96. Therefore, the outer catch
wall 86 can withstand the impact loads 82 from the pin 64 after the
pin comes out of the first shift region 63. Accordingly, the
present disclosure provides for a more durable variable
camshaft.
[0036] Accordingly, due to lack of engagement with first push wall
72 and an impact engagement with outer catch wall 86, the pin 64 no
longer experiences any loads. Therefore, the pin 64 becomes
"axially stationary" as the pin 64 travels straight through the
balancing region 66 of the control groove 60. It is understood that
axially stationary means that the actuator pin 64 will no longer be
urged against a sidewall (first push wall 72) of the groove 60
given that the pin 64 is in a region where the control groove 60
has a straight path and the pin 64 is not urged against the first
and second push walls 72, 73 of the control groove 60.
[0037] The actuator pin 64 may then cause the axially moveable
structure to make a second shift further along the base shaft 35
via second shift region 68 within the same groove 60 where the pin
64 again contacts the second push wall 73 at a second entry area 78
and therefore urges the axially movable structure 44 along the base
shaft in second shifting region 68. It is understood that the
second entry area is the area where the balancing region
transitions into the second shift region 68. As the pin 64 travels
through the control groove 60 in the second shift region 68, the
barrel cam 56 and its associated axially movable structure 44 is
moved further along the base shaft 35 until the pin 64 reaches its
final axial location at the in the disengagement region 70 after
engaging with outer disengagement wall 92. Upon progressive travel
of the pin 64 into the disengagement region 70, the pin 64 becomes
axially stationary again given that the pin 64 is no longer urged
against the second push wall 73 and therefore, the pin 64 may be
disengaged from the barrel cam 56 by retraction into the
actuator.
[0038] Given that the pin's movement from the engagement region 62
to the disengagement region 70 is performed in two steps via the
first shift region 63 and the second shift region 68 (shown in
FIGS. 6B and 6C respective), the strain experienced by the barrel
cam 56 due to the actuator pin 64 is reduced due to the increased
thickness 88 of the outer catch wall 86. Moreover, this
configuration of the present disclosure maintains the same width of
the barrel cam while significantly improving durability. It is
understood that packaging issues are critical with respect to
camshafts and therefore, design constraints limit the width of the
barrel cam 56. Accordingly, the barrel cam 56 experiences reduced
the stress on the control groove 60 as well as increased barrel cam
56 durability. It is understood that this two-step configuration
can be applied to all control grooves and may be very effective in
increasing the durability of high mass lobe packs with low
packaging space.
[0039] The detailed description and the drawings or figures are
supportive and descriptive of the disclosure, but the scope of the
disclosure is defined solely by the claims. While some of the best
modes and other embodiments for carrying out the claimed teachings
have been described in detail, various alternative designs and
embodiments exist for practicing the disclosure defined in the
appended claims.
[0040] While at least one exemplary embodiment has been presented
in the foregoing detailed description, it should be appreciated
that a vast number of variations exist. It should also be
appreciated that the exemplary embodiment or exemplary embodiments
are only examples, and are not intended to limit the scope,
applicability, or configuration of the disclosure in any way.
Rather, the foregoing detailed description will provide those
skilled in the art with a convenient road map for implementing the
exemplary embodiment or exemplary embodiments. It should be
understood that various changes can be made in the function and
arrangement of elements without departing from the scope of the
disclosure as set forth in the appended claims and the legal
equivalents thereof.
* * * * *