U.S. patent application number 10/860982 was filed with the patent office on 2005-10-20 for methods and apparatus for receiving excessive inputs in a vct system.
This patent application is currently assigned to BorgWarner Inc.. Invention is credited to Ekdahl, Earl, McCabe, Thomas, Taylor, Danny R..
Application Number | 20050229879 10/860982 |
Document ID | / |
Family ID | 34934966 |
Filed Date | 2005-10-20 |
United States Patent
Application |
20050229879 |
Kind Code |
A1 |
McCabe, Thomas ; et
al. |
October 20, 2005 |
METHODS AND APPARATUS FOR RECEIVING EXCESSIVE INPUTS IN A VCT
SYSTEM
Abstract
A method that provides increased flexibility to measure dynamic
range of a rotating system is provided. The method includes the
steps of: providing a first rotating member; providing a second
rotating member suitably engaged to the first rotating member;
providing a set of sensors disposed to sense variations in
characteristics along a circumference of the first member and the
second member respectively; providing a controller for receiving
information sensed by the sensors; determining a rate of rotation
of the rotating members; selectively using the sensed information
thereby at different rate of rotation different amount of the
sensed information is used.
Inventors: |
McCabe, Thomas; (Ithaca,
NY) ; Taylor, Danny R.; (Freeville, NY) ;
Ekdahl, Earl; (Ithaca, NY) |
Correspondence
Address: |
BORGWARNER INC.
3850 HAMLIN ROAD
AUBURN HILLS
MI
48326
US
|
Assignee: |
BorgWarner Inc.
Auburn Hills
MI
|
Family ID: |
34934966 |
Appl. No.: |
10/860982 |
Filed: |
June 4, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60562452 |
Apr 15, 2004 |
|
|
|
Current U.S.
Class: |
123/90.15 ;
123/90.16 |
Current CPC
Class: |
F01L 2800/00 20130101;
F01L 2820/041 20130101; F01L 2820/042 20130101; Y10T 137/86389
20150401; F01L 1/024 20130101; F01L 1/022 20130101; F01L 2001/0537
20130101; Y10T 137/86405 20150401; F01L 1/344 20130101 |
Class at
Publication: |
123/090.15 ;
123/090.16 |
International
Class: |
F01L 001/34 |
Claims
1. (canceled)
2. (canceled)
3. (canceled)
4. (canceled)
5. (canceled)
6. (canceled)
7. (canceled)
8. (canceled)
9. (canceled)
10. A method of altering the quantity of information sent to a
controller at various engine speeds comprising the steps of: a)
sensing at least one protrusion having a first leading edge and a
second trailing edge on a circumference of a first rotating member;
b) sensing at least one protrusion having a first leading edge and
a second trailing edge on a circumference of a second rotating
member attached to the first rotating member; c) generating a first
signal representing the protrusion of the first rotating member; d)
generating a second signal representing the protrusion of the
second rotating member; e) sending the first signal and the second
signal to a controller; f) determining a rate of rotation of the
first rotating member and the second rotating member and generating
a phase difference between the first rotating member and the second
rotating member using the first signals and the second signals
generated; g) comparing the phase difference between the first
rotating member and the second rotating member to a fixed phase
measurement; h) altering the phase difference between the first
rotating member and the second rotating member; i) comparing the
rate of rotation to a threshold rate of rotation at which either
the leading edge or the trailing edge is reported; and j)
determining whether the threshold rate of rotation has been
reached; wherein when the threshold rate of rotation has been
reached, a first signal and a second signal are generated for
either the leading edge or the trailing edge of the protrusions of
the first rotating member and the second rotating member.
11. The method of claim 10, wherein the first rotating member is
the camshaft and the second rotating member is the crankshaft.
12. The method of claim 10, wherein the threshold rate of rotation
is at high engine speeds.
13. A method of altering the quantity of information sent to a
controller at various engine speeds comprising the steps of: a)
sensing a first plurality of teeth on a circumference of a first
rotating member; b) sensing a second plurality of teeth on a
circumference of a second rotating member attached to the first
rotating member; c) generating a first signal representing the
first plurality of teeth of the first rotating member; d)
generating a second signal representing the second plurality of
teeth of the second rotating member; e) sending the first signal
and the second signal to a controller; f) determining the rate of
rotation of the first rotating member and the second rotating
member and generating a phase difference between the first rotating
member and the second rotating member using the first signals and
the second signals generated; g) comparing the phase difference
between the first rotating member and the second rotating member to
a fixed phase measurement; h) altering the phase difference between
the first rotating member and the second rotating member; i)
comparing the rate of rotation to a threshold rate of rotation at
which the first plurality of teeth and the second plurality of
teeth are sensed and the first signal and the second signal are
generated for at least one tooth sensed and skipped for at least
one other tooth sensed of the first rotating member and the second
rotating member; and j) determining whether the threshold rate of
rotation has been reached; wherein when the threshold rate of
rotation has been reached, the first plurality of teeth and the
second plurality of teeth are sensed and a first signal and a
second signal are generated for at least one tooth and skipped for
at least one other tooth of the first rotating member and the
second rotating member.
14. The method of claim 13, wherein the first rotating member is
the camshaft and the second rotating member is the crankshaft.
15. The method of claim 13, wherein the threshold rate of rotation
is at high engine speeds.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application claims an invention which was disclosed in
Provisional Application No. 60/562,452, filed Apr. 15, 2004, and
entitled "METHODS AND APPARATUS FOR RECEIVING EXCESSIVE INPUTS IN A
VCT SYSTEM The benefit under 35 USC .sctn.119(e) of the United
States provisional application is hereby claimed, and the
aforementioned application is hereby incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The invention pertains to the field of VCT systems. More
particularly, the invention pertains to methods including interrupt
switching and tooth skipping for receiving excessive inputs in a
VCT system.
BACKGROUND OF THE INVENTION
[0003] The performance of an internal combustion engine can be
improved by the use of dual camshafts, one to operate the intake
valves of the various cylinders of the engine and the other to
operate the exhaust valves. Typically, one of such camshafts is
driven by the crankshaft of the engine, through a sprocket and
chain drive or a belt drive, and the other of such camshafts is
driven by the first, through a second sprocket and chain drive or a
second belt drive. Alternatively, both of the camshafts can be
driven by a single crankshaft powered chain drive or belt drive.
Engine performance in an engine with dual camshafts can be further
improved, in terms of idle quality, fuel economy, reduced emissions
or increased torque, by changing the positional relationship of one
of the camshafts, usually the camshaft which operates the intake
valves of the engine, relative to the other camshaft and relative
to the crankshaft, to thereby vary the timing of the engine in
terms of the operation of intake valves relative to its exhaust
valves or in terms of the operation of its valves relative to the
position of the crankshaft.
[0004] Consideration of information disclosed by the following U.S.
Patents, which are all hereby incorporated by reference, is useful
when exploring the background of the present invention.
[0005] U.S. Pat. No. 5,002,053 describes a VCT system within the
field of the invention in which the system hydraulics includes a
pair of oppositely acting hydraulic cylinders with appropriate
hydraulic flow elements to selectively transfer hydraulic fluid
from one of the cylinders to the other, or vice versa, to thereby
advance or retard the circumferential position on of a camshaft
relative to a crankshaft. The control system utilizes a control
valve in which the exhaustion of hydraulic fluid from one or
another of the oppositely acting cylinders is permitted by moving a
spool within the valve one way or another from its centered or null
position. The movement of the spool occurs in response to an
increase or decrease in control hydraulic pressure, P.sub.C, on one
end of the spool and the relationship between the hydraulic force
on such end and an oppositely direct mechanical force on the other
end which results from a compression spring that acts thereon.
[0006] U.S. Pat. No. 5,107,804 describes an alternate type of VCT
system within the field of the invention in which the system
hydraulics include a vane having lobes within an enclosed housing
which replace the oppositely acting cylinders disclosed by the
aforementioned U.S. Pat. No. 5,002,053. The vane is oscillatable
with respect to the housing, with appropriate hydraulic flow
elements to transfer hydraulic fluid within the housing from one
side of a lobe to the other, or vice versa, to thereby oscillate
the vane with respect to the housing in one direction or the other,
an action which is effective to advance or retard the position of
the camshaft relative to the crankshaft. The control system of this
VCT system is identical to that divulged in U.S. Pat. No.
5,002,053, using the same type of spool valve responding to the
same type of forces acting thereon.
[0007] U.S. Pat. Nos. 5,172,659 and 5,184,578 both address the
problems of the aforementioned types of VCT systems created by the
attempt to balance the hydraulic force exerted against one end of
the spool and the mechanical force exerted against the other end.
The improved control system disclosed in both U.S. Pat. Nos.
5,172,659 and 5,184,578 utilizes hydraulic force on both ends of
the spool. The hydraulic force on one end results from the directly
applied hydraulic fluid from the engine oil gallery at full
hydraulic pressure, P.sub.S. The hydraulic force on the other end
of the spool results from a hydraulic cylinder or other force
multiplier, which acts thereon in response to system hydraulic
fluid at reduced pressure, P.sub.C, from a PWM solenoid. Because
the force at each of the opposed ends of the spool is hydraulic in
origin, based on the same hydraulic fluid, changes in pressure or
viscosity of the hydraulic fluid will be self-negating, and will
not affect the centered or null position of the spool.
[0008] U.S. Pat. No. 5,289,805 provides an improved VCT method
which utilizes a hydraulic PWM spool position control and an
advanced control method suitable for computer implementation that
yields a prescribed set point tracking behavior with a high degree
of robustness.
[0009] In U.S. Pat. No. 5,361,735, a camshaft has a vane secured to
an end for non-oscillating rotation. The camshaft also carries a
timing belt driven pulley which can rotate with the camshaft but
which is oscillatable with respect to the camshaft. The vane has
opposed lobes which are received in opposed recesses, respectively,
of the pulley. The camshaft tends to change in reaction to torque
pulses which it experiences during its normal operation and it is
permitted to advance or retard by selectively blocking or
permitting the flow of engine oil from the recesses by controlling
the position of a spool within a valve body of a control valve in
response to a signal from an engine control unit. The spool is
urged in a given direction by rotary linear motion translating
means which is rotated by an electric motor, preferably of the
stepper motor type.
[0010] U.S. Pat. No. 5,497,738 shows a control system which
eliminates the hydraulic force on one end of a spool resulting from
directly applied hydraulic fluid from the engine oil gallery at
full hydraulic pressure, P.sub.S, utilized by previous embodiments
of the VCT system. The force on the other end of the vented spool
results from an electromechanical actuator, preferably of the
variable force solenoid type, which acts directly upon the vented
spool in response to an electronic signal issued from an engine
control unit ("ECU") which monitors various engine parameters. The
ECU receives signals from sensors corresponding to camshaft and
crankshaft positions and utilizes this information to calculate a
relative phase angle. A closed-loop feedback system which corrects
for any phase angle error is preferably employed. The use of a
variable force solenoid solves the problem of sluggish dynamic
response. Such a device can be designed to be as fast as the
mechanical response of the spool valve, and certainly much faster
than the conventional (fully hydraulic) differential pressure
control system. The faster response allows the use of increased
closed-loop gain, making the system less sensitive to component
tolerances and operating environment.
[0011] U.S. Pat. No. 5,657,725 shows a control system which
utilizes engine oil pressure for actuation. The system includes A
camshaft has a vane secured to an end thereof for non-oscillating
rotation therewith. The camshaft also carries a housing which can
rotate with the camshaft but which is oscillatable with the
camshaft. The vane has opposed lobes which are received in opposed
recesses, respectively, of the housing. The recesses have greater
circumferential extent than the lobes to permit the vane and
housing to oscillate with respect to one another, and thereby
permit the camshaft to change in phase relative to a crankshaft.
The camshaft tends to change direction in reaction to engine oil
pressure and/or camshaft torque pulses which it experiences during
its normal operation, and it is permitted to either advance or
retard by selectively blocking or permitting the flow of engine oil
through the return lines from the recesses by controlling the
position of a spool within a spool valve body in response to a
signal indicative of an engine operating condition from an engine
control unit. The spool is selectively positioned by controlling
hydraulic loads on its opposed end in response to a signal from an
engine control unit. The vane can be biased to an extreme position
to provide a counteractive force to a unidirectionally acting
frictional torque experienced by the camshaft during rotation.
[0012] U.S. Pat. No. 6,547,434 shows a multi-position variable
camshaft timing system actuated by engine oil. Within the system, a
hub is secured to a camshaft for rotation synchronous with the
camshaft, and a housing circumscribes the hub and is rotatable with
the hub and the camshaft and is further oscillatable with respect
to the hub and the camshaft within a predetermined angle of
rotation. Driving vanes are radially disposed within the housing
and cooperate with an external surface on the hub, while driven
vanes are radially disposed in the hub and cooperate with an
internal surface of the housing. A locking device, reactive to oil
pressure, prevents relative motion between the housing and the hub.
A controlling device controls the oscillation of the housing
relative to the hub.
[0013] U.S. Pat. No. 6,250,265 shows a variable valve timing system
with actuator locking for internal combustion engine. The system
comprising a variable camshaft timing system comprising a camshaft
with a vane secured to the camshaft for rotation with the camshaft
but not for oscillation with respect to the camshaft. The vane has
a circumferentially extending plurality of lobes projecting
radially outwardly therefrom and is surrounded by an annular
housing that has a corresponding plurality of recesses each of
which receives one of the lobes and has a circumferential extent
greater than the circumferential extent of the lobe received
therein to permit oscillation of the housing relative to the vane
and the camshaft while the housing rotates with the camshaft and
the vane. Oscillation of the housing relative to the vane and the
camshaft is actuated by pressurized engine oil in each of the
recesses on opposed sides of the lobe therein, the oil pressure in
such recess being preferably derived in part from a torque pulse in
the camshaft as it rotates during its operation. An annular locking
plate is positioned coaxially with the camshaft and the annular
housing and is moveable relative to the annular housing along a
longitudinal central axis of the camshaft between a first position,
where the locking plate engages the annular housing to prevent its
circumferential movement relative to the vane and a second position
where circumferential movement of the annular housing relative to
the vane is permitted. The locking plate is biased by a spring
toward its first position and is urged away from its first position
toward its second position by engine oil pressure, to which it is
exposed by a passage leading through the camshaft, when engine oil
pressure is sufficiently high to overcome the spring biasing force,
which is the only time when it is desired to change the relative
positions of the annular housing and the vane. The movement of the
locking plate is controlled by an engine electronic control unit
either through a closed loop control system or an open loop control
system.
[0014] U.S. Pat. No. 6,263,846 shows a control valve strategy for
vane-type variable camshaft timing system. The strategy involves an
internal combustion engine that includes a camshaft and hub secured
to the camshaft for rotation therewith, where a housing
circumscribes the hub and is rotatable with the hub and the
camshaft, and is further oscillatable with respect to the hub and
camshaft. Driving vanes are radially inwardly disposed in the
housing and cooperate with the hub, while driven vanes are radially
outwardly disposed in the hub to cooperate with the housing and
also circumferentially alternate with the driving vanes to define
circumferentially alternating advance and retard chambers. A
configuration for controlling the oscillation of the housing
relative to the hub includes an electronic engine control unit, and
an advancing control valve that is responsive to the electronic
engine control unit and that regulates engine oil pressure to and
from the advance chambers. A retarding control valve responsive to
the electronic engine control unit regulates engine oil pressure to
and from the retard chambers. An advancing passage communicates
engine oil pressure between the advancing control valve and the
advance chambers, while a retarding passage communicates engine oil
pressure between the retarding control valve and the retard
chambers.
[0015] U.S. Pat. No. 6,311,655 shows multi-position variable cam
timing system having a vane-mounted locking-piston device. An
internal combustion engine having a camshaft and variable camshaft
timing system, wherein a rotor is secured to the camshaft and is
rotatable but non-oscillatable with respect to the camshaft is
described. A housing circumscribes the rotor, is rotatable with
both the rotor and the camshaft, and is further oscillatable with
respect to both the rotor and the camshaft between a fully retarded
position and a fully advanced position. A locking configuration
prevents relative motion between the rotor and the housing, and is
mounted within either the rotor or the housing, and is respectively
and releasably engageable with the other of either the rotor and
the housing in the fully retarded position, the fully advanced
position, and in positions therebetween. The locking device
includes a locking piston having keys terminating one end thereof,
and serrations mounted opposite the keys on the locking piston for
interlocking the rotor to the housing. A controlling configuration
controls oscillation of the rotor relative to the housing.
[0016] U.S. Pat. No. 6,374,787 shows a multi-position variable
camshaft timing system actuated by engine oil pressure. A hub is
secured to a camshaft for rotation synchronous with the camshaft,
and a housing circumscribes the hub and is rotatable with the hub
and the camshaft and is further oscillatable with respect to the
hub and the camshaft within a predetermined angle of rotation.
Driving vanes are radially disposed within the housing and
cooperate with an external surface on the hub, while driven vanes
are radially disposed in the hub and cooperate with an internal
surface of the housing. A locking device, reactive to oil pressure,
prevents relative motion between the housing and the hub. A
controlling device controls the oscillation of the housing relative
to the hub.
[0017] U.S. Pat. No. 6,477,999 shows a camshaft that has a vane
secured to an end thereof for non-oscillating rotation therewith.
The camshaft also carries a sprocket that can rotate with the
camshaft but is oscillatable with respect to the camshaft. The vane
has opposed lobes that are received in opposed recesses,
respectively, of the sprocket. The recesses have greater
circumferential extent than the lobes to permit the vane and
sprocket to oscillate with respect to one another. The camshaft
phase tends to change in reaction to pulses that it experiences
during its normal operation, and it is permitted to change only in
a given direction, either to advance or retard, by selectively
blocking or permitting the flow of pressurized hydraulic fluid,
preferably engine oil, from the recesses by controlling the
position of a spool within a valve body of a control valve. The
sprocket has a passage extending therethrough the passage extending
parallel to and being spaced from a longitudinal axis of rotation
of the camshaft. A pin is slidable within the passage and is
resiliently urged by a spring to a position where a free end of the
pin projects beyond the passage. The vane carries a plate with a
pocket, which is aligned with the passage in a predetermined
sprocket to camshaft orientation. The pocket receives hydraulic
fluid, and when the fluid pressure is at its normal operating
level, there will be sufficient pressure within the pocket to keep
the free end of the pin from entering the pocket. At low levels of
hydraulic pressure, however, the free end of the pin will enter the
pocket and latch the camshaft and the sprocket together in a
predetermined orientation.
[0018] United States published patent application No. 20030230264
teaches a method for compensating for variable cam timing of an
internal combustion engine is provided. The method includes: a)
providing a periodical crank pulse signal; b) providing a
periodical cam pulse signal; c) determining a segment, wherein the
internal combustion engine speed induces a volatile change upon
Zphase values; d) dividing the segment into sub-segments; and e)
calculating Zphase values of a plurality of points within the
sub-segments.
SUMMARY OF THE INVENTION
[0019] A method that provides increased flexibility to measure
dynamic range of a rotating system is included herein.
[0020] In a apparatus having to rotating members rotating in
substantial unison with each other via a coupling means such as a
timing belt or chain, a controller disposed to receive updates from
a set of sensors sensing a characteristic of the a circumference of
each of the rotating members, a method is provided for increasing
the number of updates at lower rotational speeds, and decrease the
number of updates at higher rotational speeds.
[0021] A set of Input-Capture Methods for Embedded Control VCT
Systems is provided whereby an optimal amount of information
generated from a set of sensors is feed to a controller.
[0022] A method and apparatus are provided such that a flexible
means for updating rates of information feed to embedded
microprocessor(s) are provided.
[0023] A method and apparatus for selecting information generated
by a set of associated pulse wheels amongst a pool of accessible
information are provided.
[0024] A method that provides increased flexibility to measure
dynamic range of a rotating system is included in which no existing
hardware needs to be changed and only method suitable for applying
computer program product to a machine is altered to optimize the
selection of information for a microcontroller at a plurality of
engine speeds.
[0025] Accordingly, a method is provided which includes the steps
of: providing a first rotating member; providing a second rotating
member suitably engaged to the first rotating member; providing a
set of sensors disposed to sense variations in characteristics
along a circumference of the first member and the second member
respectively; providing a controller for receiving information
sensed by the sensors; determining a rate of rotation of the
rotating members; selectively using the sensed information thereby
at different rate of rotation different amount of the sensed
information is used.
BRIEF DESCRIPTION OF THE DRAWING
[0026] FIG. 1 shows a feedback loop for a VCT control system.
[0027] FIG. 2 shows one of the embodiments of the control law in
FIG. 1.
[0028] FIG. 3 shows a schematically showing of the structure of a
variable cam timing (VCT) apparatus installed in a four-valve
engine.
[0029] FIG. 4 shows a pair of different tooth wheels.
[0030] FIG. 5 shows a hysteresis band around a speed point.
[0031] FIG. 6 shows a tooth wheel of the present invention.
[0032] FIG. 7A shows a tooth wheel with a first index (tooth) of
the present invention.
[0033] FIG. 7B shows FIG. 7A shows a tooth wheel with a second
index (missing tooth) of the present invention.
[0034] FIG. 8 shows a flowchart of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0035] This section includes the descriptions of the present
invention including the preferred embodiment of the present
invention for the understanding of the same. It is noted that the
embodiments are merely describing the invention. The claims section
of the present invention defines the boundaries of the property
right conferred by law.
[0036] Referring to FIG. 1, a feedback loop 10 which may be
suitable for the present invention is shown. It is noted that the
present invention can be applicable to other structures as well.
The control objective of feedback loop 10 is to have a spool valve
in a null position. In other words, the objective is to have no
fluid flowing between two fluid holding chambers of a phaser (not
shown) such that the VCT mechanism at the phase angle given by a
set point 12 with the spool 14 stationary in its null position.
This way, the VCT mechanism is at the correct phase position and
the phase rate of change is zero. A control computer program
product which utilizes the dynamic state of the VCT mechanism is
used to accomplish the above state.
[0037] The VCT closed-loop control mechanism is achieved by
measuring a camshaft phase shift .theta..sub.0 16, and comparing
the same to the desired set point 12. The VCT mechanism is in turn
adjusted so that the phaser achieves a position which is determined
by the set point 12. A control law 18 compares the set point 12 to
the phase shift .theta..sub.0 16. The compared result is used as a
reference to issue commands to a solenoid 50 to position the spool
14. This positioning of spool 14 occurs when the phase error (the
difference between set point r 12 and phase shift 50) is
non-zero.
[0038] The spool 14 is moved toward a first direction (e.g. right)
if the phase error is negative (retard) and to a second direction
(e.g. left) if the phase error is positive (advance). It is noted
that the retarding with current phase measurement scheme gives a
larger value, and advancing yields a small value. When the phase
error is zero, the VCT phase equals the set point 12 so the spool
14 is held in the null position such that no fluid flows within the
spool valve.
[0039] Camshaft and crankshaft measurement pulses in the VCT system
are generated by camshaft and crankshaft pulse wheels 52 and 54,
respectively. As the crankshaft (not shown) and camshaft (also no
shown) rotate, wheels 52, 54 rotate along with them. The wheels 52,
54 possess teeth which can be sensed and measured by sensors
according to measurement pulses generated by the sensors. The
measurement pulses are detected by camshaft and crankshaft
measurement pulse sensors 52a and 54a, respectively. The sensed
pulses are used by a phase measurement device 26. A measurement
phase difference is then determined. The phase between a cam shaft
and a crankshaft is defined as the time from successive
crank-to-cam pulses, divided by the time for an entire revolution
and multiplied by 360 degree. The measured phase may be expressed
as .theta..sub.0 16. This phase is then supplied to the control law
18 for reaching the desired spool position. A controller 10 may be
defined as comprising control law 18 and phase measurement 26.
Furthermore, controller 10 may have access to memory 28, which is
used storing data and instructions. Memory 28 may be either
internal to the controller 10, or alternatively external to the
controller 10.
[0040] A control law 18 of the closed-loop 10 is described in U.S.
Pat. No. 5,184,578 and is hereby incorporate herein by reference. A
simplified depiction of the control law may be shown in FIG. 2.
Measured phase 26 is subjected to the control law 18 initially at
block 30 wherein a Proportional-Integral (PI) process occurs. PI
process is the sum of two sub-processes. The first sub-process
includes amplification; and the second sub-process includes
integration. Measured phase is further subjected to phase
compensation at block 32, where control signal is adjusted to
increase the overall control system stability before it is sent out
to drive the actuator, in the instant case, a variable force
solenoid.
[0041] Referring to FIG. 3, a schematically showing of the
structure of a variable cam timing (VCT) apparatus installed in a
four-valve engine 40 mounted to a suitable vehicle (not shown) is
shown, the engine 40 is provided with an intake cam shaft 41, an
exhaust cam shaft 42, a first phaser 43 (hereinafter referred to
simply as "first VCT") as a second actuating mechanism mounted to
the intake cam shaft 41, a crank shaft 45, a second variable valve
timing mechanism (not shown hereinafter referred to simply as
"second VCT") as a first actuating mechanism mounted to the cam
shaft 42, and the like.
[0042] The engine 40 has a cylinder block (not shown), a cylinder
head (also not shown) securely laid on the cylinder block, and an
oil pan (not shown) fixed to a lower side of the cylinder block.
The oil pan stores oil therein, which is supplied to various
portions of the engine 40 as lubricating oil and is also supplied
to the aforementioned VCT's 43, as hydraulic control fluid. The
cylinder block includes a plurality of cylinders 50 (only one
shown) each having a combustion chamber 50a. The crank shaft 45 is
rotatably supported by the cylinder block and a bearing cap (not
shown). Each of the cylinders 50 has a piston 51 therein, which is
connected to the crank shaft 45 via a connecting rod 52. In
accordance with the combustion of air/fuel mixture in the
combustion chamber 50a, the piston 51 moves in up-and-down
directions, whereby the crank shaft 45 rotates.
[0043] The cylinder head includes a plurality of intake valves 53
and exhaust valves 54 corresponding to the respective cylinders 50.
Further, the cylinder head is provided with intake ports (not
shown) and exhaust ports (not shown) each communicating with the
combustion chamber 50a. Each of the intake ports is connected to an
intake passage (not shown), and each of the exhaust ports is
connected to an exhaust passage (not shown). A throttle valve (not
shown) disposed in an intake passage adjusts the amount of intake
air introduced into the combustion chamber 50a from the intake port
through the intake passage.
[0044] A crank pulley 39 is attached to the crank shaft 45 at its
front end portion (at a left end portion in FIG. 3), and cam
sprockets 60, 68 are attached to the cam shafts 41, 42 respectively
at their front end portions. A timing belt 37 is hung around the
crank pulley 39 and the cam sprockets 60, 68. Accordingly, torque
is transmitted from the crank shaft 45 to the cam sprockets 60, 68
via the crank pulley 39 and the timing belt 37. The torque thus
transmitted to the cam sprockets 60, 68 is further transmitted to
the cam shafts 41, 42.
[0045] The intake and exhaust cam shafts 41, 42 have a plurality of
pairs of cams 57, 58 respectively. The cams 57 or 58 constituting
each pair are spaced apart from each other by a predetermined
distance in the axial direction along the intake or exhaust cam
shaft 41 or 42 respectively. The cams 57, 58 reciprocally drive the
intake and exhaust valves 53, 54 in accordance with the cam shafts
41, 42 respectively. The intake and exhaust valves 53, 54 open or
close the intake and exhaust ports in accordance with reciprocating
movements of the cams 57, 58 respectively.
[0046] At different engine speeds, the crank and cam shafts rotate
with different rates. The sensor wheels attached respectively to
the crank and cam shafts rotate along with the shafts at different
rates. By way of an example, referring back to FIG. 1 camshaft and
crankshaft measurement pulse sensors 22a and 24a sense and generate
pulses based upon the turning and the structure of camshaft and
crankshaft pulse wheels 22 and 24. As can be seen, at lower engine
speeds, less pulses are generate for a fixed time period, such as
one period. A period can be any suitable time interval to delineate
a relationship between the crank pulses and the cam pulses with one
or more cam shaft engaging the crank shaft such as the relationship
shown in FIG. 3. On the other hand, at higher engine speeds, more
pulses are generated for a fixed time period. But the controller
such as an engine control unit (ECU) or a VCT controller are
general designed or disposed in such a way that an optimal number
of pulse information is needed for a predetermined period such as
the fixed time period. In other words, at low engine speeds, the
controller may need more information than the sensors can provide,
or alternatively the sensors may provide about enough information
that the controller requires. This is because the sensors wheels
are turning at the lower rate of revolution. But at high engine
speeds, the sensor wheels are turning at a higher rate of
revolution. Therefore, the sensors may provide more sensed
information than that is required by the controller. As can be
seen, the drawbacks include unnecessary processing time used by the
controller for processing information that is not needed for a VCT
system (at higher engine speeds). On the other hand, at low engine
speeds, not enough information may be generated by the sensors for
suitable controller processing. The present invention provides a
set of methods for reconciling the above dilemma. In other words,
the present invention provides at least one method for providing
about enough information to the controller in such a way that an
optimal amount of information provided to the controller.
Information in the immediate above sentence is defined as
information disposed to be generated by the pulse wheels on at
least two shafts engaged together such as on the cam shaft(s) and
the crank shaft of an internal combustion engine. The optimal
amount of information is defined as the selected amount of
information being selected from information disposed to be
generated by the pulse wheels on the at least two shafts engaged
together by a suitable means such as an engine timing chain.
[0047] The present invention provides Interrupt Switching, which is
a flexible means for updating rates of information feed to a
controller such as a set of embedded microprocessors, thereby
causing the controller to run efficiently. Most microprocessors
have the capability for a user to specify whether it is wanted for
the timer-based interrupts associated therewith to occur on the
rising pulse edges, the falling pulse edges, or both edges, the
present invention provides a method and apparatus for switching the
configuration of the microprocessor such that, at low engine
speeds, more pulses can received; and, on the other hand, at high
engine speed, less pulses amongst a set of selectable pulses are
received. The pulse edges are defined as the pulses associated with
the electrical pulse train such as pulses generated from sensors
being triggered by pulse wheels, the present invention utilizes
pulse wheels with teeth that have large "positive" areas, such that
they are equal to the "negative" areas. It is noted that this
choice equal areas is merely the convenience only, the present
invention contemplates unequal areas between positive and negative
areas.
[0048] Referring to FIG. 4, a first tooth wheel 70 and a second
tooth wheel 72 are provided. First tooth wheel 70 may be a pulse
wheel affixed upon a cam shaft and associated with a cam sensor
such as the sensor 22a of FIG. 1. Similarly, second tooth wheel 72
may be a pulse wheel affixed upon a crank shaft and associated with
a crank sensor such as the sensor 24a of FIG. 1. As stated supra,
we refer to the exemplified situation wherein the simplest
calculations are needed. Therefore, the example chooses first tooth
wheel 70 with 50% of the pulse-period being "positive" and 50%
being "negative" is chosen as shown in the present figure. As can
be seen first tooth wheel 70 possesses four evenly distributed
teeth where the protruding portions or positive area is equal to
the non-protruding portions or negative area circumferentially
speaking. In other words, the arc 74 spanning the circumference of
the first tooth wheel 70 is equal to the arc 76 spanning the
circumference of first tooth wheel 70 as well.
[0049] Similarly, for second tooth wheel 72, 50% of the
pulse-period being "positive" and 50% being "negative" is chosen as
shown in the present figure. As can be seen second tooth wheel 72
possesses four evenly distributed teeth where the protruding
portions or positive area is equal to the non-protruding portions
or negative area circumferentially speaking. In other words, the
arc 78 spanning the circumference of the second tooth wheel 72 is
equal to the arc 80 spanning the circumference of second tooth
wheel 72 as well.
[0050] First tooth wheel 70 may be a pulse wheel affixed upon a cam
shaft. Second tooth wheel 72 may be a pulse wheel affixed upon a
crank shaft. The crank shaft and cam shaft are associated or
engaged together via an engaging means such as a chain (not
shown).
[0051] However, in the present invention it is contemplated that
the distribution of "positive" to "negative" areas does not have to
be equal, nor does the spacing of the teeth need to equally
distributed around the circumference of the pulse wheel. The reason
for trying to achieve near equal "positive" and "negative" spacing
on the pulse wheel in the above example is important in that a more
evenly distributed updates for providing data to the controller is
achieved.
[0052] In the situation where the positive and negative going edges
of the teeth are significantly close together, there is not much
benefit to be gained, because the two updates are so close that
they seem as one to the controller.
[0053] Lets examine the case of a 4-toothed pulse wheel, 70 with
equally distributed and equally spaced teeth (50%+50%). At low
rotational speeds, the controller is set to trigger on both the
rising and falling edges of the pulse wheel in that information of
both the rising and falling edges can be received and used by the
controller without causing unnecessary hardship for the controller.
In the example of a 4-tooth wheel 70, 8 updates/revolution is
provided to the controller. In the case where we are using logic
within the processor that runs at a fixed frequency, this would
provide more frequent updates, for improved closed-loop control. As
rotational speeds increase, the update rate increases
proportionally, so the controller begins to get a significantly
higher frequency of updates. This, in most cases, is more than what
is required by the processor, and may in fact exceed the resolution
for the capabilities of the computer program products associated
with the controller. In addition, too much of the controller's time
may be require for the handling to handling of these updates.
Therefore, the present invention provides a method and associated
apparatus for switching the controller to trigger only on falling
edges (or rising edges), thereby reducing the number of
updates/rev. by half. The net result is that only 4 updates are
received by the processor in our exemplified case.
[0054] Referring to FIG. 5, at the threshold where the triggering
transition of the triggering between both edges and only falling
edges occurs, any necessary adjustment to the controller
calculations in order to maintain accuracy may be provided. As
shown, the x-coordinate stands for engine speed, and the y
coordinate stands for the number of interrupts where the controller
receives selective information from the sensors.
[0055] In the neighborhood of point 82 only two interrupts occur
for the controller to receive sensed information. A hysteresis band
84 provided around point 82 such that a sufficient margin is
provided for preventing undue switching or toggling between 2
interrupts and 4 interrupts. For example, point 82 may stand for
engine speed at 1,500 RPM. An interrupt switching hysteresis band
of 200 RPM is provided. Line segments 88 denotes the controller
receiving 4 interrupts per crank revolution; and line segments 86
denotes the controller receiving 2 interrupts per crank revolution.
As can be seen, the present invention contemplates using more than
one hysteresis band for some type of engines having a range of
speeds (RPMs).
[0056] The present invention provides interrupt switching that
allows complete shut off (or non-selection) of all eligible
interrupts to the controller that are not needed at higher engine
operating speeds, by working with only falling edges sufficient
information can be provided to the controller without, for example,
the rising edges of the input signal of the sensed information for
inputting into the controller. In other words, the rising edges of
the input signal are not used for interrupting the execution of the
program product for handling by the controller. Thus, in situations
where controller execution and timing are critical, interrupt
switching can provide dynamic range of measurement as well as
efficiency within the controller.
[0057] As an example, in an embedded VCT control system, a 4-tooth
pulse wheel on the camshaft may be chosen, and a 2-tooth pulse
wheel on the crankshaft chosen as well. Both pulse wheels have 50%
spacing of "positive" and "negative" tooth areas, and the teeth are
equally spaced around the circumference of the pulse wheel (as
shown in FIG. 4). Since the camshafts in engines spin 1/2 the speed
of the crankshaft, twice the number of teeth on the camshaft pulse
wheel is used so as to keep the frequency of the pulses between the
crankshaft and the camshaft equal. For phase measurement methods,
refer to U.S. Pat. No. 5,184,578 and U.S. Pat. No. 5,289,805 for
details. Both U.S. Pat. No. 5,184,578 and U.S. Pat. No. 5,289,805
are hereby incorporated herein by reference. At low engine speeds,
the controller is set to trigger interrupts on both the rising and
falling edges so as to provide 4 updates/crank-rev. Above a
predefined speed threshold, the controller is switched to trigger
only on falling edges so as to provide us with 2 updates/crank-rev,
or with two updates per crank revolution. In addition, at the speed
threshold, phase calculations are slightly modified to reflect the
different update rates.
[0058] Controller can be further modified or improved such that
some tooth wheel is wholly ignored by the controller. In other
words, at least one tooth may be totally ignored or skipped. Tooth
Skipping is defined as something involving the use of a pulse wheel
with more teeth than necessary for proper update rate, whereby at
least one tooth is skipped and not used.
[0059] An example would be to have an 8-tooth wheel, which is
disposed to be sensed by a sensor, as well as being disposed to
respond to an interrupt on every tooth. However, it may be
advantageous, within the program product of a controller such as an
embedded processor, to only use the time information from
every-other tooth, which is sufficient for an optimal controller
system, whereby an effective 4-tooth wheel is recognized by the
controller but in fact 8 teeth exist on the wheel.
[0060] The above can be shown be referring to FIG. 6, wherein an 8
tooth pulse wheel 90 is depicted. The teeth on wheel 90 are number
numerically from 1-8. As can be seen, if every other tooth is
skipped, a result may be achieved in which only teeth number 1, 3,
5, and 7 are command by the controller to be sensed by a sensor
92.
[0061] Furthermore, in order to increase the robustness of the
method of the present invention, adding a once/rev or index tooth
(in the form of either an added tooth, or a missing tooth) is
desirable, in that one can keep track of when the start of a new
revolution occurs. This will give us a chance to periodically
verify that we are skipping the correct tooth. This can be shown by
referring to FIGS. 7a-7b, wherein an 8+1 tooth wheel 94 and an 8-1
tooth wheel 96 are depicted.
[0062] Referring to FIG. 7a, an added tooth +1 or the 9.sup.th
tooth is provided as shown.
[0063] Referring to FIG. 7b, a missing tooth is provided by having
the region where the 6.sup.th tooth is located in wheel 94 of FIG.
7a free of any tooth.
[0064] The present inventions incorporates tooth skipping and
interrupt switching into a unitary whole to thereby enable a
controller to achieve an optimal state in controlling a system
having two rotating, engagable members, where each member has
characteristics that can be censored by suitable types of sensors.
Similar to Interrupt Switching, the tooth skipping method of the
present invention can be used to increase the number of updates at
lower rotational speeds, and decrease the number of updates at
higher rotational speeds. This can be beneficial because the
frequency of updates can be matched with the resolution in the
controller, such that the most accurate calculations can be made.
Also, by using a pulse wheel with more teeth than is intended for
counting regarding VCT system, flexibility is provided to try
various schemes of tooth counts. For example, by using a 24-tooth
wheel, you can count 1, 2, 3, 4, 6, 8, 12, or 24 teeth per
revolution. Those combinations all divide evenly into 24. By
changing the number of counted teeth, the dynamic range of
measuring the rotating system is extended because the resolution
within the processor is always optimized in that in a neighborhood
of any different speed the space between the selected teeth can be
optimized.
[0065] As can be seen, the use of an index tooth can aid the method
of tooth skipping because one feature that Tooth Skipping method
does not provide is the ability to shut off extraneous interrupts
going to the microcontroller. Tooth skipping triggers interrupts
into the microcontroller in all cases, however, it requires the
software interrupt handler to acknowledge when an extraneous pulse
has occurred, and it will need to discard that information.
Conversely, it will also need to acknowledge when a needed tooth
occurs, and use it properly in it calculations. Therefore, the
benefit of having an index tooth can be seen here, because the
index can be used to verify that the microcontroller is discarding
the correct tooth. If a synchronization problem occurs, and the
microcontroller does count the wrong tooth, an error will occur
within the calculations.
[0066] The present invention Tooth Skipping further provides
increased flexibility to measure dynamic range of a rotating
system. In the case where we are not concerned with extra
interrupts to the microcontroller, Tooth Skipping can be useful in
development work. In other words, we can experiment with the system
by choosing different sets of teeth on the wheel. For example, if
we have an engine with an 8 tooth wheel on it, but we want to
evaluate the performance of the system with a 4 tooth wheel, we can
skip alternative teeth on the wheel, and the controller will
perform as it would with an actual 4 tooth wheel. Furthermore, the
hardware Interrupt Switching could also apply here, with the same
example: i.e. a 4 tooth wheel with 8 edges, being switched to only
4 edges for testing purposes.
[0067] An example of this applied to embedded control system for
Variable Cam Timing, a 36-tooth wheel is used on the crankshaft,
and an 8-tooth wheel is used on each of the camshafts. There is
also a missing tooth on the crankshaft wheel to provide us with a
once/rev index mark. Working from the 36-tooth crankshaft pulse
wheel, we used Tooth Skipping to achieve an effective 4
pulses/crank-rev. We count 1 tooth, and then skip the following 8
teeth, and repeat, giving us 4 positive counts per revolution. We
do not skip any teeth on the camshaft, in this case. For details on
the phase measurement method, refer to U.S. Pat. Nos. 5,184,578 and
5,289,805. This method of the present invention provides us with
our desired configuration of 4 teeth on the crankshaft, and 8 teeth
on the camshafts. In some recent development work, we have used to
our advantage the ability to count only 2 teeth/rev, or only two
teeth per revolution, and thus we can work with updates at a slower
rate. One advantage using this scheme is that we can work with
different combinations without changing the pulse wheel or
hardware, only working with different method suitable for applying
computer program product to a machine to count different
combinations of teeth.
[0068] Referring to FIG. 8, a flow chart 100 depicting a method
suitable for implementing in a computer product is depicted. The
method includes the providing of a first rotating member 102 and
the providing a second rotating member suitably engaged to the
first rotating member 104, the method further includes the
providing a set of sensors disposed to sense variations in
characteristics along a circumference of the first member and the
second member respectively. A controller is used for receiving
information sensed by the sensors. A determination is made
regarding a rate of rotation of the rotating members. The method
provides selectively using the sensed information thereby at
different rate of rotation different amount of the sensed
information is used.
[0069] A plurality of points each point having a substantial
neighborhood points associated with each of the plurality of points
defines a neighborhood such as a range of rotation rate. The range
of rotation rate may be a set of engine speeds. Therefore, based
upon a determination on the rate of rotation of the members,
different approach can be made to optimally use information by
either feeding the sensed information to the controller and let the
controller determine which part of the information is used, or
alternatively by selecting only that part of the information for
feeding to the controller in that the controller do not need to
process the information that is not required.
[0070] The selectively use some of the characteristics on the
circumference of the first or second members respectively based on
the rate of rotation of the members causes the controller to
process the optimal amount of information. For example, at middle
level rate of rotation, the controller may use only some of the
sensed information in that neither all -possible sensed
information, nor only one type of sensed information are used. The
information may represent just some of the characteristics of the
rotating members such as the rising edge or falling edge of a
sensor wheel, or skipping some of the teeth of the sensor
wheel.
[0071] In another aspect, the selectively use of the sensed
information may include the selection of all the information
representing all the characteristics on the circumference of the
first or second members. For example, at low engine speed, the
controller may need all the information available that can sensed
by the sensors.
[0072] In yet another aspect, the selectively use of the sensed
information may include the selection of only the information
representing one of the characteristics on the circumference of the
first or second members. In other words, the selecting at least one
of the characteristics on the circumference of the first or second
members may be used for higher rates of rotation.
[0073] As can be appreciated, the use of index marks are needed for
improved performance of the present invention (see supra).
Therefore by providing a first index point on the circumference of
the first member, and by providing a second index point on the
circumference of the second member, the controller is disposed to
have a better or more robust disposition in determining the correct
action such as determining whether a tooth the controller thinks is
actually the tooth in the real world.
[0074] In addition, the controller may not need all of the sensed
information. Therefore, if unnecessary inform is provided to the
controller, optimal state may not be achieved. For example, more
time may be wasted by the controller in determining which piece of
information is needed and which is not. Thus, the present invention
contemplates providing the controller with only information that it
needs at various rates of rotation of the members. This may involve
a second low level controller to provided the controller with only
the sensed information that the controller needs.
[0075] Alternatively, the controller may be reprogrammed to
received different subsets of information at different rates of
rotation. In other words, by altering only the computer program
product associated with the controller, no altering of the
associated hardware is required.
[0076] One embodiment of the invention is implemented as a program
product for use with a computer system such as, for example, the
schematics shown in FIGS. 1-2 and described below. The program(s)
of the program product defines functions of the embodiments
(including the methods described below with reference to FIG. 8 and
can be contained on a variety of signal-bearing media. Illustrative
signal-bearing media include, but are not limited to: (i)
information permanently stored on in-circuit programmable devices
like PROM, EPPOM, etc; (ii) information permanently stored on
non-writable storage media (e.g., read-only memory devices within a
computer such as CD-ROM disks readable by a CD-ROM drive); (iii)
alterable information stored on writable storage media (e.g.,
floppy disks within a diskette drive or hard-disk drive); (iv)
information conveyed to a computer by a communications medium, such
as through a computer or telephone network, including wireless
communications, or a vehicle controller of an automobile. Some
embodiment specifically includes information downloaded from the
Internet and other networks. Such signal-bearing media, when
carrying computer-readable instructions that direct the functions
of the present invention, represent embodiments of the present
invention.
[0077] In general, the routines executed to implement the
embodiments of the invention, whether implemented as part of an
operating system or a specific application, component, program,
module, object, or sequence of instructions may be referred to
herein as a "program". The computer program typically is comprised
of a multitude of instructions that will be translated by the
native computer into a machine-readable format and hence executable
instructions. Also, programs are comprised of variables and data
structures that either reside locally to the program or are found
in memory or on storage devices. In addition, various programs
described hereinafter may be identified based upon the application
for which they are implemented in a specific embodiment of the
invention. However, it should be appreciated that any particular
program nomenclature that follows is used merely for convenience,
and thus the invention should not be limited to use solely in any
specific application identified and/or implied by such
nomenclature.
[0078] The following are terms and concepts relating to the present
invention.
[0079] It is noted the hydraulic fluid or fluid referred to supra
are actuating fluids. Actuating fluid is the fluid which moves the
vanes in a vane phaser. Typically the actuating fluid includes
engine oil, but could be separate hydraulic fluid. The VCT system
of the present invention may be a Cam Torque Actuated (CTA)VCT
system in which a VCT system that uses torque reversals in camshaft
caused by the forces of opening and closing engine valves to move
the vane. The control valve in a CTA system allows fluid flow from
advance chamber to retard chamber, allowing vane to move, or stops
flow, locking vane in position. The CTA phaser may also have oil
input to make up for losses due to leakage, but does not use engine
oil pressure to move phaser. Vane is a radial element actuating
fluid acts upon, housed in chamber. A vane phaser is a phaser which
is actuated by vanes moving in chambers.
[0080] There may be one or more camshaft per engine. The camshaft
may be driven by a belt or chain or gears or another camshaft.
Lobes may exist on camshaft to push on valves. In a multiple
camshaft engine, most often has one shaft for exhaust valves, one
shaft for intake valves. A "V" type engine usually has two
camshafts (one for each bank) or four (intake and exhaust for each
bank).
[0081] Chamber is defined as a space within which vane rotates.
Chamber may be divided into advance chamber (makes valves open
sooner relative to crankshaft) and retard chamber (makes valves
open later relative to crankshaft). Check valve is defined as a
valve which permits fluid flow in only one direction. A closed loop
is defined as a control system which changes one characteristic in
response to another, then checks to see if the change was made
correctly and adjusts the action to achieve the desired result
(e.g. moves a valve to change phaser position in response to a
command from the ECU, then checks the actual phaser position and
moves valve again to correct position). Control valve is a valve
which controls flow of fluid to phaser. The control valve may exist
within the phaser in CTA system. Control valve may be actuated by
oil pressure or solenoid. Crankshaft takes power from pistons and
drives transmission and camshaft. Spool valve is defined as the
control valve of spool type. Typically the spool rides in bore,
connects one passage to another. Most often the spool is located on
center axis of rotor of a phaser.
[0082] Differential Pressure Control System (DPCS) is a system for
moving a spool valve, which uses actuating fluid pressure on each
end of the spool. One end of the spool is larger than the other,
and fluid on that end is controlled (usually by a Pulse Width
Modulated (PWM) valve on the oil pressure), full supply pressure is
supplied to the other end of the spool (hence differential
pressure). Valve Control Unit (VCU) is a control circuitry for
controlling the VCT system. Typically the VCU acts in response to
commands from ECU.
[0083] Driven shaft is any shaft which receives power (in VCT, most
often camshaft). Driving shaft is any shaft which supplies power
(in VCT, most often crankshaft, but could drive one camshaft from
another camshaft). ECU is Engine Control Unit that is the car's
computer. Engine Oil is the oil used to lubricate engine, pressure
can be tapped to actuate phaser through control valve.
[0084] Housing is defined as the outer part of phaser with
chambers. The outside of housing can be pulley (for timing belt),
sprocket (for timing chain) or gear (for timing gear). Hydraulic
fluid is any special kind of oil used in hydraulic cylinders,
similar to brake fluid or power steering fluid. Hydraulic fluid is
not necessarily the same as engine oil. Typically the present
invention uses "actuating fluid". Lock pin is disposed to lock a
phaser in position. Usually lock pin is used when oil pressure is
too low to hold phaser, as during engine start or shutdown.
[0085] Oil Pressure Actuated (OPA) VCT system uses a conventional
phaser, where engine oil pressure is applied to one side of the
vane or the other to move the vane.
[0086] Open loop is used in a control system which changes one
characteristic in response to another (say, moves a valve in
response to a command from the ECU) without feedback to confirm the
action.
[0087] Phase is defined as the relative angular position of
camshaft and crankshaft (or camshaft and another camshaft, if
phaser is driven by another cam). A phaser is defined as the entire
part which mounts to cam. The phaser is typically made up of rotor
and housing and possibly spool valve and check valves. A piston
phaser is a phaser actuated by pistons in cylinders of an internal
combustion engine. Rotor is the inner part of the phaser, which is
attached to a cam shaft.
[0088] Pulse-width Modulation (PWM) provides a varying force or
pressure by changing the timing of on/off pulses of current or
fluid pressure. Solenoid is an electrical actuator which uses
electrical current flowing in coil to move a mechanical arm.
Variable force solenoid (VFS) is a solenoid whose actuating force
can be varied, usually by PWM of supply current. VFS is opposed to
an on/off (all or nothing) solenoid.
[0089] Sprocket is a member used with chains such as engine timing
chains. Timing is defined as the relationship between the time a
piston reaches a defined position (usually top dead center (TDC))
and the time something else happens. For example, in VCT or VVT
systems, timing usually relates to when a valve opens or closes.
Ignition timing relates to when the spark plug fires.
[0090] Torsion Assist (TA)or Torque Assisted phaser is a variation
on the OPA phaser, which adds a check valve in the oil supply line
(i.e. a single check valve embodiment) or a check valve in the
supply line to each chamber (i.e. two check valve embodiment). The
check valve blocks oil pressure pulses due to torque reversals from
propagating back into the oil system, and stop the vane from moving
backward due to torque reversals. In the TA system, motion of the
vane due to forward torque effects is permitted; hence the
expression "torsion assist" is used. Graph of vane movement is step
function.
[0091] VCT system includes a phaser, control valve(s), control
valve actuator(s) and control circuitry. Variable Cam Timing (VCT)
is a process, not a thing, that refers to controlling and/or
varying the angular relationship (phase) between one or more
camshafts, which drive the engine's intake and/or exhaust valves.
The angular relationship also includes phase relationship between
cam and the crankshafts, in which the crank shaft is connected to
the pistons.
[0092] Variable Valve Timing (VVT) is any process which changes the
valve timing. VVT could be associated with VCT, or could be
achieved by varying the shape of the cam or the relationship of cam
lobes to cam or valve actuators to cam or valves, or by
individually controlling the valves themselves using electrical or
hydraulic actuators. In other words, all VCT is VVT, but not all
VVT is VCT.
[0093] 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 are not intended to limit
the scope of the claims, which themselves recite those features
regarded as essential to the invention.
* * * * *