U.S. patent application number 09/981598 was filed with the patent office on 2003-04-17 for front wheel steering variable control actuator.
Invention is credited to Magnus, Brian J..
Application Number | 20030070867 09/981598 |
Document ID | / |
Family ID | 25528500 |
Filed Date | 2003-04-17 |
United States Patent
Application |
20030070867 |
Kind Code |
A1 |
Magnus, Brian J. |
April 17, 2003 |
FRONT WHEEL STEERING VARIABLE CONTROL ACTUATOR
Abstract
A variable control steering actuator for mechanically adjusting
an angle of the steerable wheel of a motor vehicle includes a
controller, a braking device in operable communication with the
controller, and a clutch device associated with the braking device.
The clutch device is disposed on an input pinion of the steering
shaft. The input pinion is in operable mechanical communication
with the steerable wheel through both the clutch device and the
braking device. A method for mechanically adjusting the angle of
the steerable wheel of the vehicle in order to control the vehicle
includes disengaging the clutch device and rotating the steering
shaft independently of an input from an operator of the vehicle.
The rotation of the steering shaft may be effectuated through a
motor disposed in operable communication with the steering
shaft.
Inventors: |
Magnus, Brian J.;
(Frankenmuth, MI) |
Correspondence
Address: |
EDMUND P. ANDERSON
DELPHI TECHNOLOGIES, INC.
Legal Staff, Mail Code: 480-414-420
P.O. Box 5052
Troy
MI
48007-5052
US
|
Family ID: |
25528500 |
Appl. No.: |
09/981598 |
Filed: |
October 16, 2001 |
Current U.S.
Class: |
180/446 |
Current CPC
Class: |
B62D 5/0478 20130101;
B62D 5/003 20130101; B62D 6/003 20130101; B62D 6/008 20130101; F16D
41/07 20130101 |
Class at
Publication: |
180/446 |
International
Class: |
B62D 005/04 |
Claims
1. A steering system for a motor vehicle, the steering system
comprising: a drive motor; and a steering actuator disposed on a
steering shaft of the motor vehicle and in communication with said
drive motor, said steering actuator being configured to
controllably provide a steering angle to a steerable wheel of the
motor vehicle in response to a sensed yaw rate and lateral
acceleration of the motor vehicle, said steering angle controllably
provided by said steering actuator being independent of a steering
angle input by an operator of the motor vehicle.
2. The steering system of claim 1 wherein said steering actuator
comprises: an arrangement of braking devices and clutches disposed
on said steering shaft, said arrangement of braking devices and
clutches providing mechanical communication and tactile feedback to
said operator of the motor vehicle from said steerable wheel.
3. The steering system of claim 1 wherein control of said steering
angle provided by said steering actuator is effectuated through a
controller disposed in informational communication with said drive
motor.
4. The steering system of claim 1 further comprising a feedback
motor disposed in operable communication with said steering shaft,
said feedback motor being configured to provide resistance to
torque applied to a hand steering device.
5. The steering system of claim 1 wherein the yawed movement of the
motor vehicle is sensed through a yaw angular velocity signal from
a yaw sensor.
6. The steering system of claim 1 wherein the lateral acceleration
of the motor vehicle is sensed through a lateral acceleration
signal from a lateral accelerometer.
7. The steering system of claim 1 wherein said steering angle
provided to said steerable wheel of the motor vehicle is through a
rack and pinion mechanism disposed in operable communication with
said operator of the motor vehicle through said steering shaft.
8. A steering system for compensating for a yaw movement of a motor
vehicle, the system comprising: an operator steering input device;
a steering linkage connecting said operator steering input device
to a steerable wheel of the motor vehicle; a yaw sensor disposed in
the motor vehicle; a controller maintained in operable
communication with said yaw sensor; a drive motor commandable by
said controller, said controller commanding said drive motor in
response to a sensed yaw moment of the motor vehicle; and a
variable steering actuator responsive to input from said drive
motor, said variable steering actuator disposed in said steering
linkage between said steerable wheel and said operator steering
input device.
9. The steering system of claim 8 wherein said drive motor is
configured to provide a steering angle to said steerable wheel that
is independent of an input from an operator of the motor
vehicle.
10. The steering system of claim 8 wherein said steering linkage
connecting said input device to a steerable wheel of the motor
vehicle is a steering shaft.
11. The steering system of claim 8 wherein said variable steering
actuator comprises: a braking device disposed on said steering
linkage; and a clutch device disposed in mechanical communication
with said braking device and said steering linkage, said clutch
device being configured to be variably actuatable in response to a
movement of said braking device.
12. The steering system of claim 11 wherein said variable actuation
of said clutch device is effectuated by said drive motor in
response to informational communication maintained between said yaw
sensor, said controller, and said drive motor.
13. A variable control steering actuator for mechanically adjusting
an angle of the steerable wheel of a motor vehicle disposed on a
steering shaft of the motor vehicle, the steering actuator
comprising: a controller; a braking device disposed on the steering
shaft, said braking device being in operable communication with
said controller; and a clutch device associated with said braking
device, said clutch device being disposed on an input pinion of the
steering shaft, said input pinion being in operable mechanical
communication with the steerable wheel through said clutch device
and said braking device.
14. The steering actuator of claim 13 wherein said braking device
comprises: a first brake disposed on the steering shaft; and a
second brake disposed adjacent said first brake on the steering
shaft.
15. The steering actuator of claim 14 wherein said clutch device
comprises: a first clutch disposed on said input pinion and being
mechanically communicable with said first brake, said first clutch
being configured to allow for the axial rotation of said input
pinion and the steering shaft in a first direction; and a second
clutch disposed adjacent said first clutch on said input pinion and
being mechanically communicable with said second brake, said second
clutch being configured to allow for the axial rotation of said
input pinion and the steering shaft in a second direction.
16. The steering actuator of claim 13 wherein said operable
communication between said controller and said braking device is
maintained through an assembly comprising: a drive motor disposed
in operable communication with said controller; a worm axially
rotatably disposed on a rotor shaft of said drive motor; and a ring
gear disposed on a surface of the steering shaft to which said
braking device is communicably attached, said ring gear being in
mechanical communication with said worm.
17. A method for compensating for yawed movement of a motor
vehicle, comprising: evaluating an input from a yaw rate sensor;
determining a desired wheel angle of the motor vehicle, said
desired wheel angle being indicative of a wheel angle
characteristic of an optimum amount of stability possible to the
motor vehicle under the conditions to which the motor vehicle is
subjected; and adjusting an existing wheel angle of a steerable
wheel of the motor vehicle in accordance with said optimum amount
of stability to correspond with said desired wheel angle.
18. The method of claim 17 wherein said adjusting of said existing
wheel angle of said steerable wheel is effectuated through a system
of clutches and brakes disposed on a steering shaft of the motor
vehicle.
19. The method of claim 18 wherein said adjusting of said existing
wheel angle of said steerable wheel comprises: disengaging a first
braking device of said system of clutches and brakes from a first
clutch of said system of clutches and brakes; and rotating said
steering shaft in an axial direction in accordance with said
determined desired wheel angle.
20. The method of claim 19 wherein said rotating of said steering
shaft is effectuated through a drive motor disposed in operably
mechanical communication with said steering shaft.
21. The method of claim 19 further comprising: re-engaging said
first braking device of said system of clutches and brakes with
said first clutch of said system of clutches and brakes.
22. A method of mechanically adjusting an angle of a steerable
wheel of a motor vehicle to control the motor vehicle, the method
comprising: disengaging a clutching device disposed between an
input pinion of a steering shaft and an output portion of said
steering shaft; and rotating said steering shaft independently of
an input from an operator of the motor vehicle.
23. The method of claim 22 wherein said rotating of said steering
shaft is effectuated through a drive motor disposed in operably
mechanical communication with said steering shaft.
24. The method of claim 22 further comprising: re-engaging said
clutching device.
25. The method of claim 22 wherein the angle of the steerable wheel
is increased relative to a body of the motor vehicle.
26. The method of claim 22 wherein the angle of the steerable wheel
is decreased relative to a body of the motor vehicle.
27. The method of claim 22 wherein said disengagement of said
clutching device is effectuated through the release of a brake.
Description
BACKGROUND
[0001] Motor vehicle handling instabilities are generally a
function of a combination of the yaw rate and lateral acceleration
of the motor vehicle and the motor vehicle speed. Such
instabilities may result in an oversteer or an understeer condition
being experienced by the vehicle. The encounter of the motor
vehicle with such a condition generally provides less than optimal
handling of the motor vehicle.
[0002] Various arrangements for compensating for oversteer and
understeer of motor vehicles have been attained by relating the yaw
behavior of the motor vehicle to the braking function. One
particular arrangement involves the comparison of a vehicle yaw
angular velocity required value and an actual vehicle yaw angular
velocity of the motor vehicle. In such an arrangement, the required
value and the actual yaw rate are measured, and the difference is
minimized through the application of independent braking.
SUMMARY
[0003] A variable control steering actuator for mechanically
adjusting an angle of the steerable wheels of a motor vehicle and a
method for compensating for an oversteer or understeer condition in
the operation of a motor vehicle are described herein. The variable
control steering actuator includes a controller, a braking device
in operable communication with the controller, and a clutch device
associated with the braking device. The clutch device is disposed
on an input pinion of the steering shaft. The input pinion is in
operable mechanical communication with the steerable wheel through
both the clutch device and the braking device.
[0004] The method for mechanically adjusting an angle of the
steerable wheels of the motor vehicle in order to control the motor
vehicle includes disengaging the clutch device disposed between the
input pinion and the upper portion of the steering shaft and
rotating the steering shaft independently of an input from an
operator of the motor vehicle. The rotation of the steering shaft
may be effectuated through a drive motor disposed in operable
communication with the steering shaft and in informational
communication with the controller.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a schematic representation of a power steering
system of a motor vehicle.
[0006] FIG. 2 is a schematic representation of a steering shaft of
a motor vehicle incorporating a variable control steering
actuator.
[0007] FIG. 3 is a cross sectional view of a portion of a variable
control steering actuator showing a braking device engaged with a
clutch.
[0008] FIG. 4 is a cross sectional view of a portion of a variable
control steering actuator showing a braking device disengaged from
a clutch.
[0009] FIG. 5 is a cross sectional view of a portion of a
clutch.
[0010] FIG. 6 is a side cross sectional view of a portion of a
clutch.
DETAILED DESCRIPTION
[0011] Referring to FIG. 1, a power steering system incorporable
into a motor vehicle is shown generally at 10. Power steering
system 10 comprises a system for the stability control of the motor
vehicle and a conventional rack and pinion steering mechanism,
shown generally at 12. Rack and pinion steering mechanism 12
includes a toothed rack 14 and an output pinion (shown below with
reference to FIG. 2) disposed on an end of a steering shaft, shown
generally at 16. The output pinion is housed within a gear housing
18. A hand steering device 20 is accessible by an operator (not
shown) of the motor vehicle and is disposed on an end of steering
shaft 16 opposite the end on which the output pinion is disposed.
Hand steering device 20 may be a steering wheel, as is shown. Upon
rotation of hand steering device 20, steering shaft 16 rotates to
turn the output pinion. Rotation of the output pinion causes the
lateral translation of toothed rack 14 thereacross, which in turn
moves tie rods 22 (only one of which is shown), each of which move
steering knuckles 24 (only one of which is shown), thereby
effectuating the movement of at least one steerable wheel 26 to
steer the motor vehicle.
[0012] Stability control of the motor vehicle is provided to power
steering system 10 through a drive motor 28 and a variable control
steering actuator, shown generally at 50, disposed on steering
shaft 16 and in operable communication with drive motor 28. In
addition to providing the stability control, variable control
steering actuator 50 provides for an infinitely variable steering
ratio of the motor vehicle. Drive motor 28 may be electrically
powered. A controller 30 disposed in informational communication
with drive motor 28 receives input signals from various sensors
operably mounted in the motor vehicle and provides an output signal
32 to the power assist actuator. The input signals to controller 30
include a vehicle velocity signal 34 from a vehicle velocity sensor
(not shown), a steering shaft angle signal 36 from a first
rotational position sensor 38, a steering pinion gear angle signal
44 from a second rotational position sensor 42, a yaw angular
velocity signal 40 from a yaw rate sensor (not shown), and a
lateral acceleration signal from a lateral accelerometer (not
shown). Controller 30 receives vehicle velocity signal 34, yaw
angular velocity signal 40, the lateral acceleration signal,
steering shaft angle signal 36, and steering pinion gear angle
signal 44. Upon an analysis and quantification of signals 34, 36,
40, 44, a transducer portion (not shown) of controller 30 derives
output signal 32, which ultimately effectuates the manipulation of
power steering system 10 through drive motor 28 by autonomously
changing the angle of the steerable wheels 26, thereby maintaining
the stability of the motor vehicle, beyond which an oversteer or
understeer condition may be experienced. A feedback motor 29 is
disposed in operable communication with upper part of steering
shaft 16 on the input side of variable control steering actuator
50. Controller 30 derives output signal 47, which effectuates the
manipulation of steering shaft 16 to provide resistance to the
torque applied to hand steering device 20 by the operator when
variable control steering actuator 50 is actuated. Such resistance
provides a simulated road feel to the operator that mimics the road
feel experience by the motor vehicle but is not transferred to the
operator due to the operation of variable control steering actuator
50.
[0013] Referring now to FIG. 2, steering shaft 16 is shown in
greater detail. Steering shaft 16 comprises an upper control shaft
46, the variable control steering actuator as shown generally at
50, and a lower steering shaft 52. Upper control shaft 46 is
connected at one end thereof to the hand steering device. An
opposing end of upper control shaft 46 is in mechanical
communication with a first end of lower steering shaft 52 through
variable control steering actuator 50, and a second end of lower
steering shaft 52 is in mechanical communication with the output
pinion, shown at 58, which is in operable communication with
toothed rack 14 of rack and pinion steering mechanism 12. A housing
60 is disposed over lower steering shaft 52 to support lower
steering shaft 52 and output pinion 58 in general. Bearings 62 are
disposed between housing 60 and lower steering shaft 52 to
facilitate the rotation of lower steering shaft 52.
[0014] Lower steering shaft 52 includes a ring gear 64 disposed
concentrically about an outer surface thereof. Ring gear 64 is
configured, positioned, and dimensioned to provide operable
communication between variable control steering actuator 50, lower
steering shaft 52, and drive motor 28 through a worm 66 disposed on
the rotor shaft of drive motor 28. Ring gear 64 and worm 66 define
a worm/worn gear interface configured to include forward-drive and
reverse-drive efficiency sufficient to allow for back-driveability
of steering shaft 16.
[0015] Variable control steering actuator 50 is defined by an
arrangement of one-way clutches 82a, 82b and correspondingly
associated braking devices 70a, 70b. The configuration of variable
control steering actuator 50 provides for the variable transmission
of torque between upper control shaft 46 and lower steering shaft
52. The incorporation of the dual one-way clutches 82a, 82b and
associated braking devices 70a, 70b enable the torque to be
generated in exclusively opposing angular directions.
[0016] Referring now to FIGS. 3 through 6, the componentry of the
variable control steering actuator is shown in detail. In FIGS. 3
and 4, one of the braking devices is shown generally at 70a. The
other braking device is substantially similar in construction.
Although braking device 70a is depicted as being of a particular
configuration, it should be understood that any braking device
capable of providing braking action to the steering shaft may be
incorporated into the variable control steering actuator. Braking
device 70a comprises a brake shoe 72 pivotally mounted to an inner
surface 74 of upper shaft 52. The mounting of brake shoe 72 to
inner surface 74 is effectuated through the use of at least one
link pin 76. A contact surface 78 of brake shoe 72 is dimensioned
to substantially correspond to a contact surface 80 of a clutch
(shown generally at 82a) for which braking device 70a radially
provides braking force. A brake actuating device 84 is disposed in
mechanically operable communication with at least one link pin 76
to effectuate the movement of brake shoe 72 between a position
wherein brake shoe 72 is "locked" or engaged with a corresponding
clutch 82a, as is shown in FIG. 3, or wherein brake shoe 72 is
disengaged from its corresponding clutch 82a, as is shown in FIG.
4.
[0017] In FIGS. 5 and 6, one of the clutches is shown in detail
generally at 82a. The other clutch is substantially similar in
construction. Although clutch 82a is depicted as being of a
particular configuration, it should be understood that any clutch
device capable of providing clutch action to the steering shaft may
be incorporated into the variable control steering actuator. Clutch
82a is configured to be a one-way clutch device capable of
providing axial rotation of input pinion 46 and the upper steering
shaft in one direction only when the braking device is engaged. As
shown in FIG. 5, clutch 82a comprises an outer ring 86 and an inner
ring 88. Inner ring 88 is disposed concentrically and rotatably on
the outside diameter of upper control shaft 46. Sprags 90 are
pivotally mounted between outer ring 86 and inner ring 88 such that
upon movement of one of the rings about the other, sprags 90 either
catch the surface of inner ring 88 and lock between outer ring 86
and inner ring 88 or are dragged across the surface of inner ring
88. A sprag ring 92, which is punched with through-holes about the
circumference thereof, may be concentrically mounted between inner
ring 88 and outer ring 86, and sprags 90 may be disposed within the
through-holes disposed in sprag ring 92 to maintain spaced
intervals between sprags 90. Retaining elements 94 are disposed
laterally adjacent to the arrangement of sprags 90 to aid sprag
ring 92 in maintaining lateral alignment of sprags 90 within the
arrangement of rings 86, 88, 92. As shown, retaining element 94 is
a garter spring.
[0018] Referring now to FIG. 6, a tangential cutaway view of an
edge of clutch 82a is shown. Outer ring 86 and inner ring 88 are
maintained at a fixed interval d from each other. Bearings 96 are
disposed between outer ring 86 and inner ring 88 to facilitate the
rotational motion of rings 86, 88 about each other.
[0019] Referring to FIGS. 2 through 6, the operation of variable
control steering actuator 50 is described. As stated above,
variable control steering actuator 50 comprises two clutches 82a,
82b and corresponding associated braking devices 70a, 70b. Clutches
82a, 82b are oriented to allow for free movement of steering shaft
16 in opposing angular directions. During normal operation of the
steering of the motor vehicle (i.e., situations in which enhanced
steering angle control is not required by the motor vehicle),
braking devices 70a, 70b each engage their corresponding clutches
82a, 82b. Because braking devices 70a, 70b are fixedly mounted to
inner surface 74 of upper shaft 52 and are in intermittent
mechanical communication with clutches 82a, 82b, which are in turn
disposed in mechanical communication with input pinion 46, tactile
feedback is maintained between the road wheels and the operator of
the motor vehicle through lower steering shaft 54, upper steering
shaft 52, the engagement of braking devices 70a, 70b and clutches
82a, 82b, input pinion 46, and the hand steering device. When both
braking devices 70a, 70b are engaged, sprags 90 of each clutch 82a,
82b engage or "lock" between their respective outer rings 86 and
inner rings 88. Sprags 90 of the first clutch 82a provide a
resistance to the turning of the hand steering device in a
"locking" direction that is typical of a normal steering operation
while sprags 90 of the second clutch 82b are at rest. Upon reversal
of the direction of the hand steering device during normal
operation, the sprags 90 of the second clutch 82b engage and
provide a resistance to the turning of the hand steering device in
the opposing locking direction, while the sprags 90 of the first
clutch 82a are at rest. When rotating the hand steering device in
either direction during normal operation, a turning ratio in which
the amount that the hand steering device is rotated corresponds to
the amount that the output pinion 58 is rotated in a one-to-one
ratio. The steerable wheels are thereby rotated in direct relation
to the fixed gear ratio of rack 14 and pinion 58.
[0020] Upon detection of an error of the desired vehicle dynamics
in relation to the actual vehicle dynamics, variable control
steering actuator 50 actuates to minimize the error. Such
conditions are indicated by feedback received from yaw rate and
lateral accelerometer sensors and the vehicle velocity sensor
through the controller. For enhanced steering angle control, one
braking device 70a is disengaged in response to a signal from the
controller, thereby causing its corresponding clutch 82a to
disengage. During such disengagement, sprags 90 of the
corresponding clutch 82a disengage from inner ring 88 or "unlock."
Upon such unlocking, rotation of the hand steering device in its
corresponding direction has limited or no effect on the angling of
the steerable wheels. Upon the unlocking of sprags 90, a signal
from the yaw rate sensors and the vehicle velocity sensor through
the controller causes drive motor 28 to operate to rotate the
engaged clutch 82a in its appropriate direction, thereby rotating
steering shaft 16. Manual rotation of the hand steering device in
an opposing direction would meet with the resistance of drive motor
28. Because the torque generated manually is less than the amount
of torque generated by drive motor 28, the manual resistance is
overcome by the torque of drive motor 28.
[0021] Depending upon the magnitude of the signal, drive motor 28
may add road wheel angle to the steerable wheels beyond the road
wheel angle commanded by the operator. Likewise, drive motor 28 may
subtract road wheel angle from the steerable wheels in the event
that the operator utilizes the steering to overcompensate for a yaw
condition. During such an addition or subtraction, the effect of
the rotation of lower steering shaft 52 by drive motor 28 in the
appropriate direction is transparent to the operator. In
particular, through the disengagement of one of the clutches and
its associated brake, additional or subtracted road angle is used
to correct the caused yaw movement of the motor vehicle. Because
one of the clutches and its associated brake remain engaged,
however, mechanical communication is maintained through the
steering linkage connecting the hand steering device and the
steerable wheels, thereby allowing tactile feedback to be
maintained between the operator and the surface of the road. The
transparency of such an operation further enables variable control
steering actuator 50 to allow for an infinite variable ratio to be
realized between the hand steering wheel and the steerable wheels.
Upon interruption of the signal from the sensors to drive motor 28,
which may be caused by a sensed correction of yaw movement from the
yaw sensors, the disengaged braking device 70a re-engages its
corresponding clutch 82a and normal steering operation is
resumed.
[0022] While preferred embodiments have been shown and described,
various modifications and substitutions may be made thereto without
departing from the spirit and scope of the invention. Accordingly,
it is to be understood that the present invention has been
described by way of illustration and not limitation.
* * * * *