U.S. patent application number 11/225761 was filed with the patent office on 2007-03-15 for electronic lock for vct phaser.
This patent application is currently assigned to BorgWarner Inc.. Invention is credited to Donald E. Freyburger, Roger T. Simpson, Franklin R. Smith.
Application Number | 20070056538 11/225761 |
Document ID | / |
Family ID | 37671350 |
Filed Date | 2007-03-15 |
United States Patent
Application |
20070056538 |
Kind Code |
A1 |
Simpson; Roger T. ; et
al. |
March 15, 2007 |
Electronic lock for VCT phaser
Abstract
A lock mechanism for a phaser of a variable cam timing system is
actuated by an electromagnetic force. Since the lock mechanism is
not dependent upon engine oil pressure, it is actuatable at any
time from engine startup to engine shutdown. A lock solenoid is
preferably used to actuate a lock pin, which is otherwise urged
toward a lock hole and a locked position by a spring force, to an
unlocked position. The lock solenoid preferably acts on a pin lock
plate that is coupled to the lock pin. A preferred startup method
and a preferred shutdown method are also described.
Inventors: |
Simpson; Roger T.; (Ithaca,
NY) ; Smith; Franklin R.; (Cortland, NY) ;
Freyburger; Donald E.; (Dryden, NY) |
Correspondence
Address: |
BORGWARNER INC.
3850 HAMLIN ROAD
AUBURN HILLS
MI
48326
US
|
Assignee: |
BorgWarner Inc.
Auburn Hills
MI
|
Family ID: |
37671350 |
Appl. No.: |
11/225761 |
Filed: |
September 13, 2005 |
Current U.S.
Class: |
123/90.17 ;
123/90.15; 123/90.18 |
Current CPC
Class: |
F01L 1/3442
20130101 |
Class at
Publication: |
123/090.17 ;
123/090.15; 123/090.18 |
International
Class: |
F01L 1/34 20060101
F01L001/34 |
Claims
1. A variable cam timing phaser for an internal combustion engine
comprising: a housing with an outer circumference for accepting
drive force; a rotor for connection to a camshaft coaxially located
within the housing, the housing and the rotor defining at least one
vane separating a chamber into an advance chamber and a retard
chamber, the rotor being capable of rotation within the housing to
shift the relative angular position of the housing and the rotor;
and a lock mechanism comprising: a lock solenoid; a lock plate in
proximity to the lock solenoid such that the lock plate moves
between a first position when the lock solenoid is in an energized
state and a second position when the lock solenoid is in a
de-energized state; a lock plate spring biasing the lock plate
toward the second position; and a lock pin coupled to the lock
plate for movement therewith; wherein when the lock plate is in the
first position, the lock pin is in an unlocked state such that the
lock pin does not prevent rotation of the rotor within the housing;
and wherein when the lock plate is in the second position, the lock
pin is in a locked state such that the lock pin extends into a lock
hole, thereby preventing rotation of the rotor within the
housing.
2. The variable cam timing phaser of claim 1, wherein the lock pin
is located within the housing in the unlocked state and the lock
hole is located in the rotor.
3. The variable cam timing phaser of claim 2, wherein the lock pin
is located such that the vane is in a mid position when the phaser
is in the locked state.
4. The variable cam timing phaser of claim 2, wherein the lock pin
is located such that the vane is in an end position when the phaser
is in the locked state.
5. The variable cam timing phaser of claim 1, wherein the lock pin
is located within the rotor in the unlocked state and the lock hole
is located in the housing on a side opposite to the lock
solenoid.
6. The variable cam timing phaser of claim 5, wherein the lock pin
is urged toward the lock plate by a lock pin spring opposing the
lock plate spring.
7. The variable cam timing phaser of claim 5, wherein the lock hole
is located such that the vane is in a mid position when the phaser
is in the locked state.
8. The variable cam timing phaser of claim 5, wherein the lock hole
is located such that the vane is in an end position when the phaser
is in the locked state.
9. The variable cam timing phaser of claim 1 further comprising: a
variable force solenoid, wherein the lock solenoid is mounted with
and around the variable force solenoid; and a spool valve actuated
by the variable force solenoid to regulate a position 5 of the
phaser.
10. The variable cam timing phaser of claim 1 further comprising: a
linear actuator selected from the group consisting of: a) a stepper
motor; b) a vacuum actuator; c) a differential pressure controller;
and d) a regulated pressure controller; and a spool valve actuated
by the linear actuator to regulate a position of the phaser.
11. The variable cam timing phaser of claim 1, wherein the lock pin
and the lock plate are coupled to move together.
12. A method of controlling a variable cam timing phaser having a
housing with an outer circumference for accepting drive force, a
rotor for connection to a camshaft coaxially located within the
housing, a lock solenoid, a lock plate in proximity to the lock
solenoid, a lock plate spring biasing the lock plate toward the
second position, and a lock pin coupled to the lock plate for
movement therewith, during startup of an internal combustion engine
comprising the step of: a) energizing the lock solenoid to move the
lock plate coupled to the lock pin to a position wherein the lock
pin is removed from a lock hole such that the lock pin does not
prevent rotation of the rotor within the housing.
13. The method of claim 12 further comprising the steps of: b)
determining if conditions have been met to move the phaser; and c)
if conditions have been met, energizing a variable force solenoid
to move a spool in a spool valve, thereby moving the phaser.
14. A method of controlling a variable cam timing phaser having a
housing with an outer circumference for accepting drive force, a
rotor for connection to a camshaft coaxially located within the
housing, a lock solenoid, a lock plate in proximity to the lock
solenoid, a lock plate spring biasing the lock plate toward the
second position, and a lock pin coupled to the lock plate for
movement therewith, during shutdown of an internal combustion
engine comprising the step of: a) de-energizing the lock solenoid
to release the lock plate coupled to the lock pin, thereby allowing
the lock pin to extend into a lock hole to prevent rotation of a
rotor within a housing.
15. The method of claim 14 further comprising the step of: b)
moving the phaser to a locked position when the engine is at idle
such that the lock pin is aligned with the lock hole.
16. The method of claim. 14 further comprising the steps of: b)
determining the position of the phaser when the engine is turned
off; and c) moving the phaser to a locked position as the engine is
slowing down such that the lock pin is aligned with the lock hole.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention pertains to the field of variable camshaft
timing phasers. More particularly, the invention pertains to an
electronically actuated lock for a variable camshaft timing
phaser.
[0003] 2. Description of Related Art
[0004] Various mechanisms have been employed with internal
combustion engines to vary the angle between the camshaft and the
crankshaft for improved engine performance or reduced emissions.
The majority of these variable camshaft timing (VCT) mechanisms use
one or more "vane phasers" on the engine camshaft (or camshafts, in
a multiple-camshaft engine). In most cases, the phaser has a rotor
with one or more vanes, mounted to the end of the camshaft,
surrounded by a housing with the vane chambers into which the vanes
fit. The vanes may also be mounted to the housing, and the chambers
may be in the rotor. The housing's outer circumference forms the
sprocket, pulley, or gear-accepting drive force through a chain,
belt, or gears, usually from the camshaft, or from another camshaft
in a multiple-cam engine.
[0005] A variety of lock mechanisms are known in the art for
locking a phaser in a predetermined position. Commonly a lock pin
is biased toward a lock hole by a spring for locking the phaser and
away from the lock hole by engine oil pressure for unlocking the
phaser. Thus, when oil pressure is reduced, such as upon shutdown
of the engine, the lock pin engages the lock hole to lock the rotor
with respect to the housing. On many cam phasers there is a
piston-style lock that uses oil pressure to move the lock pin to
let the phaser actuate. This style of lock mechanism requires oil
pressure to release the lock pin from engagement with the lock hole
and thus may be delayed from releasing after the engine starts
while the oil pressure builds up. Many oil pressure actuated (OPA)
phasers do not unlock at hot engine start up because the oil
pressure is too low for the phaser to be stable or actuate
consistently.
[0006] With the ever increasing need to improve fuel efficiency,
original equipment manufacturers (OEMs) are exploring advanced
combustion strategies that benefit from a cam phaser with an
extended range of motion (>60.degree. ), fast actuation, and
operability immediately after the engine starts. A cam torque
actuated (CTA) phaser utilizes the torsionals of the engine to meet
these needs. In order for the CTA phaser to move, the lock pin must
be able to release prior to the engine pump providing oil to the
phaser.
[0007] One such means for actuating a lock mechanism is an
electromagnetic force. Electromagnetic braking is known in the art.
In U.S. Pat. No. 4,754,727, several brake mechanisms are shown for
providing a retarding force, including several electromagnetic
brake configurations. U.S. Pat. No. 5,031,585 shows a wet brake
mechanism electromagnetically actuated for retarding phase changes.
In U.S. Pat. Nos. 6,250,265, 6,382,155, and 6,883,479, a locking
plate is electromagnetically actuated for locking a VCT phaser.
However, none of these patents use an electromagnetic force to
actuate a lock pin.
[0008] In many situations a lock pin mechanism for a phaser is
preferable over a locking plate mechanism or a braking mechanism.
Therefore, there is a need in the art for a lock pin mechanism that
is not dependent upon engine oil pressure.
SUMMARY OF THE INVENTION
[0009] The lock mechanism for a phaser of a variable cam timing
system is actuated by an electromagnetic force. Since the lock
mechanism is not dependent upon engine oil pressure, it is
actuatable at any time from engine startup to engine shutdown. A
lock solenoid is preferably used to actuate a lock pin, which is
otherwise urged toward a lock hole and a locked position by a
spring force, to an unlocked position. The lock solenoid preferably
acts on a pin lock plate that is coupled to the lock pin. A
preferred startup method and a preferred shutdown method are also
described.
[0010] The variable cam timing phaser for an internal combustion
engine includes a housing with an outer circumference for accepting
drive force, a rotor for connection to a camshaft coaxially located
within the housing, and a lock mechanism. The housing and the rotor
define at least one vane separating a chamber into an advance
chamber and a retard chamber. The rotor is capable of rotation
within the housing to shift the relative angular position of the
housing and the rotor. The lock mechanism includes a lock solenoid,
a lock plate in proximity to the lock solenoid, a lock plate spring
biasing the lock plate toward the second position, and a lock pin
coupled to the lock plate for movement therewith. The lock plate
moves between a first position when the lock solenoid is in an
energized state and a second position when the lock solenoid is in
a de-energized state. When the lock plate is in the first position,
the lock pin is in an unlocked state such that the lock pin does
not prevent rotation of the rotor within the housing. When the lock
plate is in the second position, the lock pin is in a locked state
such that the lock pin extends into a lock hole, thereby preventing
rotation of the rotor within the housing.
[0011] In one embodiment, the lock pin is located within the
housing in the unlocked state and the lock hole is located in the
rotor. In this embodiment, the lock pin may be located such that
the vane is in a mid position when the phaser is in the locked
state or such that the vane is in an end position when the phaser
is in the locked state.
[0012] In another embodiment, the lock pin is located within the
rotor in the unlocked state and the lock hole is located in the
housing on a side opposite to the lock solenoid. Preferably, the
lock pin is urged toward the lock plate by a lock pin spring
opposing the lock plate spring. In this embodiment, the lock hole
may be located such that the vane is in a mid position when the
phaser is in the locked state or such that the Vane is in an end
position when the phaser is in the locked state.
[0013] In a preferred embodiment, the phaser further includes a
variable force solenoid, wherein the lock solenoid is mounted with
and around the variable force solenoid and a spool valve actuated
by the variable force solenoid to regulate a position of the
phaser.
[0014] In another embodiment, the phaser further includes a linear
actuator and a spool valve actuated by the linear actuator to
regulate a position of the phaser. The linear actuator is
preferably a stepper motor, a vacuum actuator, a differential
pressure controller, or a regulated pressure controller.
[0015] The lock pin and the lock plate are preferably coupled to
move together.
[0016] A method of controlling a variable cam timing phaser during
startup of an internal combustion engine includes energizing the
lock solenoid to move the lock plate coupled to the lock pin to a
position wherein the lock pin is removed from a lock hole such that
the lock pin does not prevent rotation of the rotor within the
housing. The. method preferably further includes determining if
conditions have been met to move the phaser, and if conditions have
been met, energizing a variable force solenoid to move a spool in a
spool valve, thereby moving the phaser.
[0017] A method of controlling a variable cam timing phaser during
shutdown of an internal combustion engine includes de-energizing
the lock solenoid to release the lock plate coupled to the lock
pin, thereby allowing the lock pin to extend into a lock hole to
prevent rotation of a rotor within a housing. In one embodiment,
the method further includes moving the phaser to a locked position
when the engine is at idle such that the lock pin is aligned with
the lock hole. In another embodiment, the method further includes
determining the position of the phaser when the engine is turned
off and moving the phaser to a locked position as the engine is
slowing down such that the lock pin is aligned with the lock
hole.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 shows a schematic cross section of an
electromechanical lock mechanism of the present invention in an
unlocked state.
[0019] FIG. 2 shows the mechanism of FIG. 1 in a locked state.
[0020] FIG. 3 shows a cross section of a first embodiment of the
present invention in an unlocked state.
[0021] FIG. 4 shows the embodiment of FIG. 3 in a locked state.
[0022] FIG. 5 shows a cross section of a second embodiment of the
present invention in an unlocked state.
[0023] FIG. 6 shows the embodiment of FIG. 5 in a locked state.
[0024] FIG. 7 shows an elevated view of lock pin and lock hole
positions of a phaser of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0025] In a preferred embodiment, an electronic coil is mounted on
the outside of the phaser to magnetize a plate coupled to a lock
pin. The coil is stationary and is preferably mounted with and
around a variable force solenoid (VFS) that is used to move the VCT
spool valve. The lock solenoid is energized upon command from an
electronic control unit that also controls the cam phaser solenoid.
Inputs that help determine when to energize the solenoid and
release the lock pin include, but are not limited to, engine speed,
engine temperature, time, exhaust temperature, manifold air
pressure (MAP), and throttle position.
[0026] Referring to FIGS. 1 and 2, a lock mechanism 10 of the
present invention includes a lock solenoid 12, a pin lock plate 14,
a lock pin 16, and a lock hole 18. In an unlocked state, as shown
in FIG. 1, the lock coil 20 of the lock solenoid 12 is energized,
thereby attracting the lock plate 14, which pulls and holds the
lock pin 16 clear of the lock hole, 18, allowing the rotor 28 to
rotate with respect to the housing 24. In a locked state, as shown
in FIG. 2, the lock solenoid 12 is not energized, and a spring 22
force urges the lock pin 16 into the lock hole 18, thereby
preventing the rotor 28 from rotating with respect to the housing
24. In the embodiment shown in FIGS. 1 and 2, the lock pin 16 sits
primarily within the housing 24 of the phaser 26 in an unlocked
state and extends into the lock hole 18, which is located in the
rotor 28, in a locked state. The lock hole 18 is preferably in a
vane of the rotor 28. A camshaft 30 is also shown in FIGS. 1 and 2.
In an alternate embodiment discussed below, the lock pin sits
primarily in the rotor in an unlocked state and extends into a lock
pin hole in the housing in a locked state.
[0027] In a first preferred embodiment of the present invention, as
shown in FIG. 3 in an unlocked state, a lock solenoid 40 is located
annularly around the variable force solenoid (VFS) 42, which is
used to control the position of a spool 44 of a spool valve. The
position of the spool 44 regulates whether the phaser 46 moves
toward an advance position, moves toward a retard position, or
remains in its present position. A solenoid stem 48 extends from
the VFS 42 to actuate the spool 44 in conjunction with an opposing
spool spring 50. The spool valve preferably sits near the end of
the camshaft 52. The lock solenoid 40 preferably has a recessed
surface 54 complementary to and for receiving the lock plate 56
when the electromagnetic coil 58 of the lock solenoid 40 is
energized.
[0028] In this embodiment, the lock pin 60 is located in the
housing 62, when the lock solenoid 40 is energized and the lock
mechanism is in an unlocked state. In this state, the lock pin 60
does not prevent the rotor 64 from rotating with respect to the
housing 62. As shown in FIG. 4, when the lock solenoid 40 is
de-energized, a spring 66 urges the lock pin 60 into the lock hole
68 located in the rotor 64, thereby preventing the rotor 64 from
rotating with respect to the housing 62.
[0029] In a second preferred embodiment of the present invention,
as shown in FIG. 5 in an unlocked state, a lock solenoid 70 is
located annularly around a variable force solenoid 72, which is
used to control the position of a spool 74 of a spool valve. The
position of the spool 74 regulates whether the phaser 76 moves
toward an advance position, moves toward a retard position, or
remains in its present position. A solenoid stem 78 extends from
the VFS 72 to actuate the spool 74 in conjunction with an opposing
spool spring 80. The spool valve preferably sits near the end of
the camshaft 82. The lock solenoid 70 preferably has a recessed
surface 84 complementary to and for receiving the lock plate 86
when the electromagnetic coil 88 of the lock solenoid 70 is
energized.
[0030] In this embodiment, the lock pin 90 is located in the rotor
92, when the lock solenoid 70 is energized and the lock mechanism
is in an unlocked state. In this state, the lock pin 90 does not
prevent the rotor 92 from rotating with respect to the housing 94.
A lock pin spring 96 urges the lock pin 90 away from the lock hole
98 and toward the lock plate 86. As shown in FIG. 6, when the lock
solenoid 70 is de-energized, a lock plate spring 100 urges the lock
plate 86 toward the lock pin 90, pushing the lock pin 90 into the
lock hole 98 located in the housing 94, thereby preventing the
rotor 92 from rotating with respect to the housing 94. Although the
lock mechanism is preferably in a locked state when the lock
solenoid is in a de-energized state and in an unlocked state when
the lock solenoid is in an energized state, an unlocked state when
the lock solenoid is in a de-energized state and a locked state
when the lock solenoid is in an energized state is within the
spirit of the present invention.
[0031] The lock pin hole may be located either in a mid position or
a normal position as shown in FIG. 7, which shows the phaser in an
unlocked position. A rotor 110 is mounted in a housing 112 and on
top of an end plate 114. Sprocket teeth 116 surround the housing
112. The housing 112 includes recesses which are each divided into
a pair of chambers by vanes extending from the rotor 110. A lock
pin is located in one of the vanes on the side facing the end plate
114. In a mid position strategy, the lock pin hole is located such
that in a locked state the vane is located significantly far away
from both sides of the chambers. In a normal strategy, the lock pin
hole is located such that in a locked state the vane is rotated to
one extreme with respect to the housing. In the embodiment of FIG.
3 and FIG. 4, the lock pin hole 118 is in the vane and the lock pin
is in a first position 120 for the mid position strategy and in a
second position 122 in the normal strategy. In the embodiment of
FIG. 5 and FIG. 6, the lock pin 118 is in the vane and the lock pin
hole is in a first position 120 for the mid position strategy and
in a second position 122 in the normal strategy.
[0032] In an embodiment of the present invention, the following
start method is preferably used. During the cranking of the engine
the phaser is preferably locked in mid position, and as soon as the
engine starts the phaser is preferably commanded to move to a new
position for improved emissions or idle stability. The electronic
control unit (ECU) determines if conditions have been met to move
the phaser. If the conditions have been met, the VFS is energized
so that the phaser is allowed to move to a new position. The lock
pin release solenoid is energized to allow the phaser to move to
the new position. This is operated under closed loop control.
[0033] In an embodiment of the present invention, the following
shut down method is preferably used. When the engine is at idle,
the phaser is commanded to the locked position. Then the lock pin
in released and the phaser is locked. The phaser is controlled
under closed loop control to a desired position at idle, and the
lock solenoid is de-energized to allow the lock pin to insert into
the lock hole. This position may be at the positional end stops of
the phaser or in a mid position. The electronic control unit then
verifies that the phaser is at the commanded set point prior to
engine shutdown.
[0034] In another embodiment, the phaser is at a position away from
the locked position, and when the engine is turned off and is.
slowing down, the phaser is commanded to move to the locked
position and the lock pin is released. In this embodiment, it is
preferable to release the lock pin when the key is turned off so
that the lock starts to release when the phaser is moving to the
locked position. Thus, when the phaser reaches the locked position,
the lock pin simply drops into the lock pin hole.
[0035] Although the invention is described and shown in FIG. 3
through FIG. 6 in combination with a variable force solenoid for
controlling the spool valve of the phaser, other controllers
including, but not limited to, a stepper motor, a vacuum actuator,
and a pressure controller such as a differential or a regulated
pressure controller may be used within the spirit of the present
invention.
[0036] The lock mechanism of the present invention may be used with
any system with a lock mechanism including, but not limited to, an
oil pressure actuated (OPA) phaser, a torsion-assist (TA) phaser
and a cam-torque actuated (CTA) phaser within the spirit of the
present invention.
[0037] Accordingly, it is to be understood that the embodiments of
the invention herein described are merely illustrative of the
application of the principles of the invention. Reference herein to
details of the illustrated embodiments is not intended to limit the
scope of the claims, which themselves recite those features
regarded as essential to the invention.
* * * * *