U.S. patent application number 16/022042 was filed with the patent office on 2018-10-25 for low friction switching roller finger follower for high valve lift.
This patent application is currently assigned to Eaton Corporation. The applicant listed for this patent is Eaton Corporation. Invention is credited to Edwin Scott Brownell, James E. McCarthy, JR., Nikhil Saggam.
Application Number | 20180306072 16/022042 |
Document ID | / |
Family ID | 59225179 |
Filed Date | 2018-10-25 |
United States Patent
Application |
20180306072 |
Kind Code |
A1 |
Brownell; Edwin Scott ; et
al. |
October 25, 2018 |
LOW FRICTION SWITCHING ROLLER FINGER FOLLOWER FOR HIGH VALVE
LIFT
Abstract
A switching roller finger follower for valve actuation comprises
a pair of outer arms comprising an axle mounting. A bridge portion
joins the pair of outer arms. A latch assembly comprises a ferrule.
The ferrule is configured to reciprocate in a latch recess. An
inner arm is pivotably mounted to a main axle and comprises a
bearing rotatably mounted to a bearing axle. The bearing is
configured to transfer forces from a cam lobe to the inner arm. A
catch on the inner arm is configured to latch against the lip when
the ferrule is in a first position. The catch can pivot past the
ferrule when the ferrule is in a second position.
Inventors: |
Brownell; Edwin Scott;
(Marshall, MI) ; McCarthy, JR.; James E.;
(Kalamazoo, MI) ; Saggam; Nikhil; (Pune,
IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Eaton Corporation |
Cleveland |
OH |
US |
|
|
Assignee: |
Eaton Corporation
Cleveland
OH
|
Family ID: |
59225179 |
Appl. No.: |
16/022042 |
Filed: |
June 28, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/US2016/068140 |
Dec 21, 2016 |
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16022042 |
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62271391 |
Dec 28, 2015 |
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62279976 |
Jan 18, 2016 |
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62349983 |
Jun 14, 2016 |
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62350621 |
Jun 15, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01L 1/2405 20130101;
F01L 2800/00 20130101; F01L 1/185 20130101; F01L 2001/467 20130101;
F01L 2305/00 20200501; F02D 13/023 20130101; F01L 2001/186
20130101; F01L 1/08 20130101; F01L 13/0036 20130101; Y02T 10/12
20130101; F01L 2820/01 20130101 |
International
Class: |
F01L 13/00 20060101
F01L013/00; F01L 1/08 20060101 F01L001/08; F01L 1/18 20060101
F01L001/18; F01L 1/24 20060101 F01L001/24 |
Goverment Interests
GOVERNMENT RIGHTS STATEMENT
[0002] This invention was made with Government support under
Agreement No. DE-EE0005981, awarded by the US Department of Energy.
The US Government has certain rights in the invention.
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 2016 |
IN |
201611029817 |
Claims
1. A switching roller finger follower for valve actuation,
comprising: a pair of outer arms configured to transfer forces from
a pair of outer cam lobes, the pair of outer arms comprising
respective axle mountings; a bridge portion joining the pair of
outer arms, the bridge portion comprising a first spring seat
opposite a second spring seat, and a latch recess between the first
spring seat and the second spring seat; a latch assembly comprising
a ferrule, the ferrule configured to reciprocate in the latch
recess; a main axle mounted in the respective axle mountings; an
inner arm pivotably mounted to the main axle, the inner arm
comprising: an inner bearing axle comprising portions extending
through the inner arm; an inner bearing rotatably mounted to the
inner bearing axle, the inner bearing configured to transfer forces
from a cam lobe to the inner arm; and a catch on the inner arm, the
catch configured to latch against the ferrule when the ferrule is
in a first position, the catch configured to pivot past the ferrule
when the ferrule is in a second position; and a first spring
mounted to the first spring seat and a second spring mounted to the
second spring seat, wherein the first spring and the second spring
are biased between the bridge portion and the portions of the inner
bearing axle extending through the inner arm, wherein the inner
bearing axle is between the bridge portion and the axle
mounting.
2. The switching roller finger follower of claim 1, wherein each
arm of the pair of outer arms further comprises: a wall portion
comprising a projection, an axle mounting, and a bearing axle
opening; and a slider pad extending perpendicular to the wall
portion, the slider pad configured to transfer forces from a cam
lobe to the respective outer arm.
3. The switching roller finger follower of claim 1, wherein each
arm of the pair of outer arms comprises an outer rotatable
bearing.
4. The switching roller finger follower of claim 1, wherein the
latch assembly further comprises a hydraulic fluid port, the
ferrule in fluid communication with the hydraulic fluid port.
5. The switching roller finger follower of claim 4, wherein the
ferrule further comprises a fluid recess.
6. The switching roller finger follower of claim 1, wherein the
ferrule is configured to reciprocate in the latch recess in
response to hydraulic fluid pressure.
7. (canceled)
8. (canceled)
9. The switching roller finger follower of claim 1, wherein each
respective slider pad is in the shape of an arcuate tab, and each
respective slider pad extends like a shelf from an upper edge of
the outer arm.
10. The switching roller finger follower of claim 1, wherein each
arm of the pair of outer arms comprise a bearing axle opening, and
wherein the bearing axle reciprocates in the bearing axle openings
when the inner arm pivots on the main axle.
11. (canceled)
12. A variable valve lift assembly, comprising the switching roller
finger follower of claim 1, and further comprising: a valve
coupling mounted to the main axle; a valve stem mounted to the
valve coupling; a pair of normal lift cam lobes aligned to transfer
forces to respective outer arms; and a high lift cam lobe
comprising a larger diameter portion than the normal lift cam
lobes, the high lift cam lobe positioned between the pair of normal
lift cam lobes and further configured to transfer forces to the
bearing, wherein the normal lift cam lobes and the high lift cam
lobe are eccentric lobes mounted to a cam rail for rotation against
the switching roller finger follower.
13. The variable lift valve assembly of claim 12, wherein: when the
latch assembly is in a latched condition, the catch on the inner
arm is latched against the ferrule, the ferrule is in the first
position, and the high lift cam lobe pushes the switching roller
finger follower a first distance; and when the latch assembly in in
an unlatched condition, the ferrule is unlatched from the catch,
the ferrule is in the second position, the high lift cam lobe
pushes the bearing to pivot the catch past the lip, and the normal
lift cam lobes push on respective outer arms to move the switching
roller finger follower a second distance; and the second distance
is less than the first distance.
14. The variable lift valve assembly of claim 12, wherein: when the
latch assembly is in a latched condition, the catch on the inner
arm is latched against the ferrule, the ferrule is in the first
position, and the high lift cam lobe pushes the switching roller
finger follower a first duration; and when the latch assembly in in
an unlatched condition, the ferrule is unlatched from the catch,
the ferrule is in the second position, the high lift cam lobe
pushes the bearing to pivot the catch past the lip, and the normal
lift cam lobes push on respective outer arms to move the switching
roller finger follower a second duration; and the second duration
is less than the first duration.
15. The variable lift valve assembly of claim 12, wherein the latch
assembly further comprises a hydraulic fluid port, and the ferrule
is in fluid communication with the hydraulic fluid port, and
wherein the assembly further comprises a hydraulic lash adjuster
mounted in fluid communication with the hydraulic fluid port.
16. The variable valve lift assembly of claim 12, wherein the
ferrule is configured to reciprocate within the latch recess within
one revolution of the cam rail to switch the switching roller
finger follower between a normal lift valve profile and a high lift
valve profile.
17. A method of actuating the switching roller finger follower of
claim 1, comprising: aligning a pair of normal lift cam lobes to
selectively transfer forces to respective outer arms; and aligning
a high lift cam lobe to transfer forces to the bearing, the high
lift cam lobe comprising a larger diameter portion than the normal
lift cam lobes, the high lift cam lobe positioned between the pair
of normal lift cam lobes; rotating the normal lift cam lobes and
the high lift cam lobe on a cam rail, wherein the high lift cam
lobe is configured to push the bearing more than the normal lift
cam lobes push the respective outer arms.
18. The method of claim 17, further comprising: reciprocating the
ferrule in the latch recess, wherein: when the latch assembly is in
a latched condition, the catch on the inner arm is latched against
the ferrule, the ferrule is in the first position, the normal lift
cam lobes do not contact the outer arms, and the high lift cam lobe
pushes the bearing of the switching roller finger follower; and
when the latch assembly is in an unlatched condition, the ferrule
is unlatched from the catch, the ferrule is in the second position,
the high lift cam lobe pushes the bearing to pivot the catch past
the lip, and the normal lift cam lobes push on respective outer
arms to move the switching roller finger follower less than the
high lift cam lobe; and performing a late intake valve closing
event when the latch assembly is in a latched condition.
19. (canceled)
20. (canceled)
21. (canceled)
22. (canceled)
23. (canceled)
24. (canceled)
25. (canceled)
26. The switching roller finger follower of claim 1, wherein each
arm of the pair of outer arms comprises: a first wall portion
comprising a first bearing axle opening; a second wall portion
comprising a second bearing axle opening; an outer bearing axle
mounted across the first bearing axle opening and the second
bearing axle opening; and an outer bearing mounted on the outer
bearing axle configured to transfer forces from a cam lobe to the
respective outer arm.
27. The switching roller finger follower of claim 26, wherein the
inner bearing axle protrudes into the second wall portion of each
arm of the pair of outer arms.
28. The switching roller finger follower of claim 26, wherein each
second wall portion includes a guide recess to receive and guide
the inner bearing axle.
29. The switching roller finger follower of claim 26, wherein the
inner bearing axle extends into a plane of each second wall
portion.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of International
Application No. PCT/US2016/068140 filed Dec. 21, 2016, which claims
the benefit of priority of U.S. Provisional Patent Application No.
62/271,391 filed on Dec. 28, 2015, U.S. Provisional Patent
Application No. 62/279,976 filed on Jan. 18, 2016, U.S. Provisional
Application No. 62/349,983 filed on Jun. 14, 2016, U.S. Provisional
Patent Application No. 62/350,621 filed on Jun. 15, 2016, and
Indian Patent Application No. 201611029817 filed on Aug. 31, 2016,
the contents of which are incorporated herein by reference in their
entireties.
FIELD
[0003] This application provides a variable valve actuation
switching roller finger follower for late intake valve closing.
BACKGROUND
[0004] Variable valve actuation refers to manipulating the timing
of valve action with respect to engine cylinders. A cylinder of an
engine has a reciprocating piston. An intake valve controls when
the cylinder is open to intake a charge, and an exhaust valve
controls when the cylinder is open to exhaust a spent charge.
Techniques include early intake valve closing (EIVC) and late
intake valve closing (LIVC). "Early" and "Late" are with respect to
a normal Otto cycle valve closing timing, which is near bottom dead
center of piston travel.
[0005] Another technique deactivates the valve motion altogether,
resulting in a "lost motion." Examples of mechanisms for cylinder
deactivation can be seen in WO 2014/071373, and related
applications, assigned to the present applicant. The mechanisms of
WO 2014/071373 are used for implementing either a valve lift event
or a cylinder deactivation event. The rocker arm can either actuate
a valve, or accommodate "lost motion" during a cylinder
deactivation event.
[0006] Trying to use such a rocker arm for alternative variable
valve lift actuations is problematic, because there are two valve
lift heights to accommodate when trying to provide both normal lift
and one of EIVC or LIVC. Early intake valve closing (EIVC) can
achieve some success using the prior art mechanisms. EIVC is a "low
lift" event.
[0007] Late intake valve closing (LIVC) is a "high lift" event.
Trying to use the cylinder deactivation rocker arm of WO
2014/071373 for LIVC results in a high friction, energy-losing
event, as the LIVC event takes place on the sliding interface, and
the normal lift event takes place on the rolling interface. The
fuel savings benefits of LIVC are negated by the friction losses.
Merely reversing the rolling and sliding events on the mechanism of
FIGS. 53 & 77 of WO 2014/071373 does not sufficiently solve the
dual goals of a high lift event with low loss parameters. The prior
art arrangement is for deactivation, and not for low and high lift
events. And, the design of FIG. 99 of WO 2014/071373 accommodates
only a single cam lobe. The single cam lobe design works for the
embodiment of FIG. 99 of WO 2014/071373 because the valve lift
event is designed for a single height and the other event is a "no
lift" event during cylinder deactivation. Thus, the prior art does
not adequately provide a mechanism for providing two valve lift
events of differing heights with simultaneous low friction losses
on the cam rail.
[0008] What is needed is a variable valve lift assembly that
provides two different valve lift heights with low actuation
losses.
SUMMARY
[0009] The methods, devices, and assemblies disclosed herein
overcome the above disadvantages and improves the art by way of a
switching roller finger follower for valve actuation.
[0010] In a first aspect, the switching roller finger follower can
comprise a pair of outer arms are configured to transfer forces
from a pair of outer cam lobes. The pair of outer arms comprise
respective axle mountings. A bridge portion joins the pair of outer
arms. The bridge portion comprises a first spring seat opposite a
second spring seat, and a latch recess between the first spring
seat and the second spring seat. A latch assembly comprises a
ferrule, and the ferrule is configured to reciprocate in the latch
recess. A main axle is mounted in the respective axle mountings. An
inner arm is pivotably mounted to the main axle. The inner arm
comprises an inner bearing axle comprising portions extending
through the inner arm. An inner bearing is rotatably mounted to the
inner bearing axle. The inner bearing is configured to transfer
forces from a cam lobe to the inner arm. A catch can be on the
inner arm. The catch can be configured to latch against the ferrule
when the ferrule is in a first position. The catch can be
configured to pivot past the ferrule when the ferrule is in a
second position. A first spring can be mounted to the first spring
seat and a second spring can be mounted mounted to the second
spring seat, wherein the first spring and the second spring are
biased between the bridge portion and the portions of the inner
bearing axle extending through the inner arm. The inner bearing
axle is between the bridge portion and the axle mounting.
[0011] A switching roller finger follower according to another
aspect can comprise a pair of outer arms comprising a wall portion
comprising a projection, an axle mounting, and a bearing axle
opening. A slider pad extends perpendicular to the wall portion,
the slider pad configured to transfer forces from a cam lobe to the
respective outer arm. A bridge portion joins the pair of outer
arms, the bridge portion comprises a respective spring seat
adjacent each wall portion. A latch recess is in fluid
communication with a fluid port. The bearing axle opening is
between the bridge portion and the axle mounting. A latch assembly
comprises a ferrule, the ferrule comprises a lip. The ferrule is
configured to reciprocate in the latch recess. A main axle is
mounted in the axle mounting. An inner arm is pivotably mounted to
the main axle and comprises a bearing rotatably mounted to a
bearing axle. The bearing axle extends through the bearing axle
openings in the outer arms, and the bearing is configured to
transfer forces from a cam lobe to the inner arm. A catch on the
inner arm is configured to latch against the lip when the ferrule
is in a first position. The catch is configured to pivot past the
ferrule when the ferrule is in a second position. A respective
spring is mounted to a respective spring seat and is biased between
a respective projection and the bearing axle so as to bias the
bearing axle towards the slider pad.
[0012] The switching roller finger followers disclosed herein can
be used in a variable valve lift assembly and can be used in
methods of actuating valves.
[0013] Additional objects and advantages will be set forth in part
in the description which follows, and in part will be obvious from
the description, or may be learned by practice of the disclosure.
The objects and advantages will also be realized and attained by
means of the elements and combinations particularly pointed out in
the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a view of a switching roller finger follower.
[0015] FIG. 2 is a view of a switching roller finger follower
coupled to cam lobes.
[0016] FIG. 3 is a view of a switching roller finger follower
having a normal lift event.
[0017] FIG. 4 is a view of a switching roller finger follower in a
high lift event.
[0018] FIG. 5 is a cross-section view of a switching roller finger
follower in a variable valve lift assembly.
[0019] FIGS. 6 & 7 are views of an alternative switching roller
finger follower.
[0020] FIG. 8 comprises explanatory lift profiles.
[0021] FIG. 9 is a flow diagram for a method of switching between
normal lift and high lift valve actuation utilizing a switching
roller finger follower.
DETAILED DESCRIPTION
[0022] Reference will now be made in detail to the examples which
are illustrated in the accompanying drawings. Wherever possible,
the same reference numbers will be used throughout the drawings to
refer to the same or like parts. Directional references such as
"left" and "right" are for ease of reference to the figures.
[0023] The disclosure provides a variable valve lift assembly with
two different valve lift heights and low actuation losses. A
section of a cam rail 240, part of a cam assembly 200, is shown
having three lobes 210, 220, 230. Normal lift event lobes 210, 220
are eccentric and designed to press on slider pads 610, 620 of
switching roller finger follower 100. High lift event lobe 230 is
also eccentric and designed to press on bearing 300. When an
internal latch assembly 951 is unlatched, the normal lift event
occurs, shown in FIG. 3. When the internal latch assembly 951 is
latched, as by catching lip 975 of ferrule 970 against catch 350 of
inner arm 310, a high lift event occurs, also shown in FIG. 4. The
high lift event can correspond to a late intake valve closing
(LIVC) event.
[0024] FIG. 1 shows a switching roller finger follower 100. An
inner arm 310 is pivotably coupled to a pair of outer arms 600 via
a main axle 500 mounted to axle mountings 650 in the outer arms.
The main axle 500 also couples to a valve coupling 400. The outer
arms 600 are joined by a bridge portion 690. The outer arms 600
each comprise a wall portion 670 comprising an axle mounting 650
and a bearing axle opening 640. A slider pad 610 extends
perpendicular to the wall portion 670. The slider pad 610 can be
arcuate. The slider pad 610 can be in the shape of a tab, and
extend like a shelf from an upper edge of the outer arm 600. The
slider pad 610 can be proximal and above the bearing axle opening
640. The bearing axle opening can be located between the bridge
portion 690 and the axle mounting 650. The slider pad 610 can also
be located between the bridge portion 690 and the axle mounting
650. The inner arm 310 pivots between the outer arms 600, and the
inner arm 310 can latch to the outer arm assembly inside of the
variable valve lift assembly. This protects the latching function
from events that can interfere with the inner arm motion.
[0025] Inner arm 310 is coupled to a bearing 300 mounted via an
inner surface 340 on rollers 330 on a bearing axle 320. The bearing
axle 320 can protrude through opening 640 of outer arm 600 wall
portion 670. Bearing axle 320 can include a "dog bone" shape to
catch against a spring arm 715 of a spring 710. Spring 710 biases
spring arm 717 against a projection 615 on the bridge portion 690
or wall portion 670 of outer arm 600. Projection 615 can be, for
example, a ledge. a portion of a protruding surface of a groove, or
other surface feature. Spring 710 coils around a spring seat 617 on
bridge portion 690. Spring seat 617 is adjacent wall portion 670. A
cap 800 secures spring 710 on spring seat 617. Spring arm 715 is
biased to push bearing axle 320 towards slider pad 610, and thus
towards cam rail 240, and in to contact with high lift cam lobe
230. Slider pad 610 can have a shelf-like configuration to extend
from wall portion 670 while providing space for bearing axle 320 to
reciprocate underneath. Spring arm 715 can move in a plane parallel
to the wall portion 670, and beneath the slider pad 610, so that
the spring 710 does not protrude past the slider pad 610. This
optimizes packaging space. A mirror image arrangement for spring
720 is on the opposite side of switching roller finger follower
100.
[0026] Because bearing 300 can rotate (roll) around bearing axle
320, should the high lift cam lobe 230 frictionally drag against
bearing 300, it can rotate, and dissipate drag losses. This
prevents harm to the engine and the cam rail 240 and ensures the
high valve lift event occurs in a low-force fuel economy cycle,
such as LIVC.
[0027] In order to accommodate the normal and high lift cam lobes
210, 220, 230, the slider pads 610, 620 and bearing 300 must be
designed to respect that if too much friction occurs with respect
to the cam rail 240, the friction can negate the fuel economy
benefits of the LIVC event by placing too much lossy resistance
against the cam rail 240. So, the slider pads 610, 620 and
associated normal lift cam lobes 210, 220 cannot be too wide. But,
if the slider pads 610, 620 and bearing 300 are too narrow, there
is high axial stack up of tolerances, issues with thermal growth,
and the chance of mis-alignment between the cam lobes and switching
roller finger follower surfaces, which can lead to engine failure.
Also, poor design results in not enough force transfer from the cam
rail to the switching roller finger follower to actuate the valve.
So, the widths of the slider pads 610, 620 and bearing 300 must be
wide enough to transfer forces from the normal and high lift cam
lobes 210, 220, 230, yet not so wide as to deleteriously resist
motion of the cam lobes, yet not so narrow as to elude
manufacturability. Other design considerations include the bearing
300 and slider pads 610, 620 withstanding the contact stresses
conveyed by the cam lobes 210, 220, 230, and designing the slider
pads in light of deflection that can occur due to the shelf-like or
tab shape portion extending out from the wall portion 670.
[0028] Contrasting against the drag and friction issues is spacing:
the slider pads 610, 620 and bearing 300 cannot be so wide, nor the
lobes so wide, that packaging constraints are not met. If the
switching roller finger follower 100 cannot fit in its packaging
space over the engine valves, the part goes unused, and so the
widths of the slider pads 610, 620 and bearing 300 must be kept
narrow.
[0029] The inner arm 310 and outer arm 600 also must be
sufficiently sturdy, yet conform to packaging requirements.
[0030] To incorporate all of these variables, a narrow bearing 300
seats in narrow inner arm 310 to accommodate the high lift event
lobe 230, which is always spinning pressed against the bearing 300.
Outer arm 600 includes slider pads 610, 620. The slider pads 610,
620 can comprise a coating to reduce friction losses, and the
normal lift event lobes 210, 220 slide against the slider pads 610,
620 to push the outer arm 600, and the valve, in a normal valve
lift operation (power event). As shown by comparing FIGS. 3 &
4, the high lift event lobe 230 is always in contact with bearing
300, while the normal lift event lobes 210, 220 can pass over the
slider pads 610, 620 during a high lift event.
[0031] When a normal lift event is selected, the lip 975 is
withdrawn towards the latch recess 977 and the catch 350 can pivot
past the lip 975. This "lost motion" set-up can be accomplished by
applying hydraulic pressure to internal port 695 to a level that
the pressure on the ferrule 970 overcomes the spring force of
spring 960. The high lift event lobe 230 pushes the bearing 300
down between the outer arm 600. The inner arm 310 provides a "lost
motion" function, preventing the high lift event lobe 230 from
transferring its valve lift height LH to the valve attached to
valve coupling 400. The high lift event is "lost" when the inner
arm 310 moves in the unlatched condition. The normal lift lobes
210, 220 press on the slider pads 610, 620 to lift the valve.
[0032] When the high lift event is selected, the ferrule 970 is in
a normally latched position, and the inner arm 310 catch 350 is
latched to lip 975 of ferrule 970. Low hydraulic pressure to
internal port 695 permits the spring force of spring 960 to push
the ferrule 970 outward. The lip 975 extends out away from the
latch recess 977. The inner arm 310 is latched to the outer arm
600. The inner arm 310 cannot move down between the outer arm 600.
So, when the high lift event lobe 230, which is longer by a lift
height LH than the normal lift event lobe, presses on the bearing
300, the inner arm 310 and outer arm 600 move together, giving the
highest, longest valve lift event. The catch on the inner arm is
thus configured to latch against the lip when the ferrule is in a
first position, and configured to pivot past the ferrule when the
ferrule is in a second position.
[0033] The outer arms 600 are joined by a bridge portion 690
flanked by projections 615, 625. Projections are designed to bias
respective springs 710, 720, yet avoid contact with normal lift cam
lobes 210, 220. Bridge portion 690 includes a latch recess 977
which receives internal latch assembly 951 for hydraulic control of
latching action. The latch assembly 951 can be electrically
actuated, but hydraulic actuation is illustrated. Frit 950 can
interface with a hydraulic line and an actuatable valve via port
955. A spring 960 biases ferrule 970 towards the latched
position.
[0034] An alternative, normally unlatched, arrangement could be
implemented. A spring could alternatively bias the ferrule 970 to
the unlatched position. An internal port 695 in the bridge portion
690 connects a fluid recess 973 in the ferrule 970 to hydraulic
fluid, so as to supply actuation and deactivation forces on the
latching action. For example, selecting appropriate fluid force to
port 955, and selecting an appropriate spring force, can withdraw
the ferrule 970 to the unlatched position. Supplying fluid pressure
to the fluid recess 973 can extend the ferrule 970 to latch the lip
975 against catch 350. The same fluid pressure can be shared with a
hydraulic lash adjuster (HLA) 900 mounted in a cup 979 of bridge
portion 690. Internal ports 911 share fluid pressure from supply
913 with the HLA and internal port 695. Another supply 914 can
interface with an alternate area 912 of the HLA.
[0035] The valve coupling 400 receives a valve stem 410 to actuate
an engine valve. A spring seat 420 can be mounted on the valve stem
410. A portion 430 of the valve stem can be surrounded by a spring
440 for biasing the valve against the engine head. The engine valve
is biased in a lifted position, which closes the cylinder. The
switching roller finger follower 100 is acted on by the cam lobes
110, 120, 130 to open the valve one of two distances, as below. An
overhead cam rail system pushes the valve downward with respect to
the cam lobe, and the valve-opening action is referred to as a
"lift event" in the art, despite that the valve lowers towards the
cylinder in the engine head, and then lifts back via the spring
force of spring 440.
[0036] A variable valve lift assembly, shown in FIGS. 2 & 5,
can comprise the switching roller finger 100. The valve coupling
400 is mounted to the main axle 500. The valve stem 410 is mounted
to the valve coupling 400. A pair of normal lift cam lobes 210, 220
can be aligned to transfer forces to respective slider pads 610,
620 of respective outer arms 600. A high lift cam lobe 230
comprises a larger diameter portion, delineated lift height LH in
FIG. 2, than the normal lift cam lobes. The high lift cam lobe 230
is positioned between the pair of normal lift cam lobes 210, 220
and is further configured to transfer forces to the bearing 300.
The normal lift cam lobes 210, 220 and the high lift cam lobe 230
are eccentric lobes mounted to a cam rail 240 for rotation against
the switching roller finger follower 100.
[0037] When the latch assembly 951 is in a latched condition, the
catch 350 on the inner arm 310 is latched against the lip 975, the
ferrule 970 is in the first position, and the high lift cam lobe
230 pushes the switching roller finger follower 100 a first
distance. The cam lobe is circular about a first portion, but
extends eccentrically at a second portion. The eccentric second
portion has a height. The first distance can be equal to the
distance of the lift height LH plus the height of the segment of
the eccentric portion of the lobe.
[0038] When the latch assembly 951 in in an unlatched condition,
the lip 975 is unlatched from the catch 350, the ferrule 970 is in
the second position, the high lift cam lobe 230 pushes the bearing
300 to pivot the catch 350 past the lip 975, and the normal lift
cam lobes 210, 220 push on respective slider pads 610, 620 to move
the switching roller finger follower 100 a second distance. The cam
lobe is circular about a first portion, but extends eccentrically
at a second portion. The eccentric second portion has a height. The
second distance can be equal to the height of the segment of the
eccentric portion of the lobe. The second distance is less than the
first distance. This means that the valve is open for less time in
a normal lift event than in a high lift event.
[0039] The variable lift valve assembly can be further configured
so that the latch assembly further comprises a hydraulic fluid
port, which can be internal port 695 in communication with port 955
or internal port 695 alone. The ferrule 970 is in fluid
communication with the hydraulic fluid port. A hydraulic lash
adjuster 900 can be mounted in fluid communication with the
hydraulic fluid port.
[0040] An alternative switching roller finger follower 1601 is
shown in FIGS. 6 & 7. Instead of slider pads, the outer arms
1670 comprise rotatable bearings 1630 for interfacing with outer
cam lobes 210, 220. As above, a normal valve lift event can occur
on the outer arms 1670 while a high lift valve event can occur, or
be lost motion on, inner arm 310.
[0041] The pair of outer arms 1670 are mirror images of each other.
Each of the pair of outer arms 1670 comprise an axle mounting 1650.
One of the pair of outer arms comprises a first wall portion 1672
comprising a first bearing axle opening 1671. A second wall portion
1674 comprises a second bearing axle opening. The second wall
portion can comprise a cut-out or other recess for permitting
guiding and pivoting of the bearing axle 320. By including an inner
recess on the second wall portion, the spring arms 1715, 1725 are
less able to walk off the bearing axle 320, because the bearing
axle 320 extends into a plane of the second wall portion 1674.
Spring arms 1715, 1725 are biased against the bearing axle 320, and
spring arms 1717, 1727 are biased against a projection 1615 on
bridge portion 1690.
[0042] The second arm of the pair of outer arms 1670 comprises wall
portions 1676 & 1678. The second arm and first arm of the pair
of outer arms 1670 mirror the corresponding outer arms on the other
side of the inner arm 310. An outer bearing axle 1635 is mounted
across the first bearing axle opening 1671 and the second bearing
axle opening. An outer bearing 1630 is mounted on the outer bearing
axle 1635 and is configured to transfer forces from a cam lobe 210
to the outer arm 1670. The outer bearing 1630 can comprise, for
example, a roller bearing or a rotating wheel.
[0043] Bridge portion 1690 is similar to bridge portion 690 above.
Bridge portion 1690 joins the pair of outer arms 1670. Bridge
portion 1690 comprises a first spring seat 617 opposite a
mirror-image second spring seat. Bridge portion 1690 and outer arms
1670 cooperate to form projections 1615 for biasing spring arms
1717 & 1727 of springs 1710 & 1720. Alternative caps 8110
can secure springs 1710 & 1720 to mirror-image spring seats
617. Latch recess 977 for latch assembly 951 is between the first
spring seat 617 and the second spring seat. Ferrule 970 is
configured to reciprocate in the latch recess 977, as detailed
above.
[0044] A main axle 500 is mounted in the pair of axle mountings
1650. Inner arm 310 is pivotably mounted to the main axle 500 and
functions similarly as above. Optional snap rings. C-clips, or the
like 510 can be included to prevent lateral or non-pivoting motion
of the inner arm 310 on the main axle 500. Inner arm 310 is "U"
shaped and comprises extensions 312 & 314 joined by a catch
portion 355. An inner bearing axle 320 extends across the
extensions 312 & 314 and comprises portions extending through
the inner arm 310 and towards the outer arms 1670. A bearing 300 is
rotatably mounted to the inner bearing axle 320 between the
extensions 312 & 314. Bearing 300 can be a roller bearing
configured to transfer forces from a cam lobe 230 to the inner arm
310.
[0045] A catch 350 on catch portion 355 of the inner arm 310 is
configured to latch against the ferrule 970 when the ferrule 970 is
in a first position. The catch 350 can interface with a lip 975, as
described above. Catch 350 is configured to pivot past the ferrule
970 when the ferrule is in a second position.
[0046] A first spring 1710 mounted to the first spring seat 617 and
a second spring 1720 mounted to the second spring seat are biased
between the bridge portion 1690 and the portions of the inner
bearing axle 320 extending through the inner arm 310 so as to bias
the inner bearing axle 320 with respect to the ferrule 970. Biasing
the inner bearing axle 320 in this manner can lift the catch 350
away from the ferrule 970 to make it easier to retract the ferrule
970. Springs 710 & 720 can similarly bias the bearing axle 320
in FIGS. 1-4. The catch 350 has less drag against the lip 975. And,
the inner arm is biased to return to a starting position. Contact
between inner cam lobe 230 and inner bearing 300 can also be
maintained via the spring forces.
[0047] As can be seen, the bearing axle openings for the inner
bearing axle 320 are between the bridge portion 1690 and the axle
mountings 1650. The inner arm 310 pivots inwardly with respect to
the outer arm.
[0048] A method of actuating the switching roller finger follower
100 can be seen in FIG. 9. The method can comprise steps of
aligning a cam assembly 200 with the switching roller finger
follower 100. A pair of normal lift cam lobes 210, 220 selectively
transfer forces to respective slider pads 610, 620 or bearings 1630
of respective outer arms 600, 1670 when a normal lift event is
selected. This is accomplished by rotating the outer normal lift
lobes on outer arms of the roller finger follower, as in step S920.
When a high lift event, which can be a late intake valve closing
event, the method can comprise aligning and rotating a high lift
cam lobe 230 to transfer forces to the bearing 300, as in step
S950. The high lift cam lobe 230 can comprise a larger diameter
portion delineated LH in FIG. 2 than the normal lift cam lobes 210,
220. The high lift cam lobe 230 can be positioned between the pair
of normal lift cam lobes 210, 220. The method can rotate the normal
lift cam lobes 210, 220 and the high lift cam lobe 230 on a cam
rail 240. The high lift cam lobe 230 is configured to push the
bearing 300 a larger distance than the normal lift cam lobes 210,
220 push the respective outer arms 600.
[0049] The method can further comprise reciprocating the ferrule
970 in the latch recess 690. When the latch assembly 951 is in a
latched condition of step S940, the catch 350 on the inner arm 310
is latched against the lip 975, the ferrule 970 is in the first
position, the normal lift cam lobes 210, 220 do not contact
respective slider pads 610, 620, or bearings 1630 and the high lift
cam lobe 230 pushes the switching roller finger follower 100 the
larger distance. When the latch assembly 951 in in an unlatched
condition of step S910, the lip 975 is unlatched from the catch
350, the ferrule 970 is in the second position, the high lift cam
lobe 230 pushes the bearing 300 the larger distance to pivot the
catch 350 past the lip 975, and the normal lift cam lobes 210, 220
push on respective slider pads 610, 620 or bearings 1630 to move
the switching roller finger follower 100 a second distance that is
less than the larger distance. The method can comprise performing a
late intake valve closing event when the latch assembly is in a
latched condition.
[0050] FIG. 9 outlines that a method of actuating a switching
roller finger follower for valve actuation can comprise step S910
for unlatching an inner arm of the roller finger follower for a
normal valve lift event. In step S920, Rotating outer cam lobes on
outer arms of the roller finger follower 100, 1601 permit a normal
valve lift event. With the inner arm 310 unlatched, in step S930,
the inner high lift cam lobe rotates on the inner bearing 300 of
the inner arm 310. The high lift event is lost in the pivoting
motion of the inner arm within the outer arms so that contact
between the normal lift outer lobes 210, 220 and the outer arms 670
& 1670 is maintained. The normal, or low, lift event can be
seen in FIG. 8. The outer diameters of outer cam lobes 220, 210 are
selected so that, as the cam rotates on cam rail 240, the valve
affiliated with valve coupling 400 moves with respect a combustion
cylinder.
[0051] FIG. 8 shows a sample lift profile for a high lift and a low
lift valve event, along with a delta lift profile for illustrating
the difference between the two valve lift events. The profiles are
shown with the cam degrees centered about a zero point. The zero
point corresponds to the peak opening for the high lift event. By
arranging the cam lobes with respect to the engine valves, one can
vary the rocker ratio and extent to which changes in the cam lobe
profile impact valve lift. For example, one can tailor when the
valve opens and closes with respect to a piston in an engine
cylinder reaching top dead center (TDC). For example, the outer cam
lobes 210, 220 can open the valve most fully prior to top dead
center.
[0052] To convert from the normal, low, lift valve actuation to a
high lift valve actuation, the inner arm 310 is latched with
respect to the outer arms 670, 1670 in step S940. The inner high
lift cam lobe 230 having the larger lift height LH rotates on the
inner bearing 300 in step S950. The inner arm 310 and outer arms
are designed with respect to the cam lobes 210, 220, 230 to
maintain a minimum height between the outer arms and the outer cam
lobes when the inner cam lobe 230 is rotating on the inner bearing
300 so that energy is not spent dragging or rolling the outer cam
lobes 210, 220 against the outer arms 1670.
[0053] The valve follows the high lift profile shown in FIG. 8. The
valve opens most fully closer to top dead center, and the valve
opening is said to be "late" with respect to the normal valve lift
event. The duration of time that the valve is open is also longer
in this high lift example, because the inner lobe 230 is designed
to push on the inner bearing 300 earlier in the rotation of the cam
rail 240 than is designed for the normal lift outer lobes 210, 220.
The inner lobe is also designed to push on the inner bearing 300
for a longer period of time than the normal lift outer lobes 210,
220 after the valve opens. The longer duration lift time and higher
valve opening can be achieved by tailoring the eccentricity of the
lift height of the center lobe 230 with respect to the outer lobes
210, 220. The lift height LH can vary around the center lobe 230 to
have a longer duration high lift event and the lift height LH can
vary around the center lobe 230 to have a higher valve opening high
lift event. By varying the eccentricity, it is possible to vary how
long the lobes 210, 220, 230 press on the roller finger follower
before the lobes return to base circle BC. The time the cam spends
on base circle BC can also be chosen so that the switching roller
finger follower can switch between a high lift mode and a normal
lift mode within one revolution of the cam rail. That is, the
ferrule is configured to reciprocate within the latch recess within
one revolution of the cam rail to switch the switching roller
finger follower between a normal lift valve profile and a high lift
valve profile. This permits an engine to operate in high lift mode
on one cylinder intake, then to operate in normal lift mode on the
next intake in the engine stroke cycle. Since the outer lobes 210,
220 have a smaller outer area than the inner high lift lobe 230,
the latching and unlatching of the inner arm 310 is accomplished
within one cam revolution of the outer lobes 210, 220, and
preferably, the latching and unlatching of the inner arm 310 is
completed while the cam lobes 210, 220, 230 are on base circle BC.
The lift height LH formed on the inner cam lobe 230 results in the
peak for the high lift event being greater than the peak for the
low lift event. In the illustrated example of FIG. 8, the high lift
event lifts the valve 1 millimeter (1 mm) higher than the normal
lift event. By way of example, the lift height LH on the cam lobe
can be 2-3 mm, yet this can yield only a 1 mm change in the height
of the valve opening between low lift and high lift. Alternatively,
the lift height ratio can result in the cam lift height LH being
less than the minimum height difference between normal and high
lift events.
[0054] As can be seen from the delta lift line, there is a height
difference between the low lift and high lift events. The high lift
event has more lift than the low lift event. The height difference
can vary throughout the event and can be tailored by the cam lobe
profiles. This technique can be used, for example, to implement
"LIVC," or late intake valve closing. LIVC can be one or both of a
longer duration valve event with respect to a normal lift valve
event, or a higher valve opening event with respect to a normal
lift valve event. FIG. 8 is exemplary, only, and other lift
profiles, lift heights, minimum heights, rocker ratios, degrees of
cam rotation, etc. can be implemented without departing from the
scope of the claims.
[0055] Other implementations will be apparent to those skilled in
the art from consideration of the specification and practice of the
examples disclosed herein. It is intended that the specification
and examples be considered as exemplary only, with the true scope
of the invention being indicated by the following claims.
* * * * *