U.S. patent application number 09/681954 was filed with the patent office on 2001-10-18 for vehicle wheel suspension arrangement.
Invention is credited to Zetterstrom, Sigvard.
Application Number | 20010030400 09/681954 |
Document ID | / |
Family ID | 20413903 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010030400 |
Kind Code |
A1 |
Zetterstrom, Sigvard |
October 18, 2001 |
Vehicle wheel suspension arrangement
Abstract
An arrangement for the suspension of a wheel of an automotive
vehicle is disclosed. The wheel is connected to a propulsion device
for driving the vehicle and a braking device for braking each
individual wheel. The invention has sensors for detecting at least
the angular steering displacement of the vehicle required by the
vehicle driver, two steering link arms fitted between said body and
attachment points in the wheel, positioned on both sides of an
imaginary vertical line running through the center of the wheel,
and a control unit for processing signals from the sensors and for
actuating the steering link arms for adjustment of the wheel in
response to the signals and the current operating state of the
vehicle. Through the invention, an improved, integrated wheel
suspension unit for automotive vehicles is provided, particularly
allowing dynamic wheel alignment adjustment and adjustment of the
angular steering displacement of each individual wheel of the
vehicle.
Inventors: |
Zetterstrom, Sigvard;
(Hakenaset, SE) |
Correspondence
Address: |
TRACY W. DRUCE
KILPATRICK STOCKTON LLP
11130 SUNRISE VALLEY DRIVE
SUITE 300
RESTON
VA
20191-4329
US
|
Family ID: |
20413903 |
Appl. No.: |
09/681954 |
Filed: |
June 29, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09681954 |
Jun 29, 2001 |
|
|
|
PCT/SE99/02476 |
Dec 23, 1999 |
|
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Current U.S.
Class: |
280/5.51 ;
280/124.1 |
Current CPC
Class: |
B60G 3/20 20130101; B60K
7/0007 20130101; B60G 2200/10 20130101; B62D 6/04 20130101; B60G
2204/62 20130101; B62D 7/159 20130101; B60G 7/006 20130101; B60G
2202/40 20130101; B60K 17/046 20130101; B62D 17/00 20130101; B60K
2007/0092 20130101; B62D 7/1509 20130101; B60G 2200/462 20130101;
B60K 2007/0038 20130101 |
Class at
Publication: |
280/5.51 ;
280/124.1 |
International
Class: |
B60G 017/01 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 29, 1998 |
SE |
9804592-5 |
Claims
1. An arrangement for the suspension of a wheel of a vehicle,
comprising: a propulsion device connected to said wheel for driving
the vehicle, a braking device for braking each individual wheel,
sensors for detecting at least an angular steering displacement of
the vehicle required by the vehicle driver, at least two steering
link arms fitted between a vehicle body and attachment points in
said wheel and positioned on both sides of an imaginary vertical
line running through the center of said wheel, and a control unit
for processing signals from said sensors and for actuating said
steering link arms for adjustment of said wheel in response to said
signals and the current operating state of the vehicle.
2. The arrangement according to claim 1, said propulsion device
further comprising an electrical motor arranged in association with
said wheel.
3. The arrangement according to claim 2 wherein said braking device
is integrated into said electrical motor.
4. The arrangement according to claim 3 further comprising an
additional sensor indicating a degree of application of said
braking device required by the vehicle driver.
5. The arrangement according to claim 1 further comprising
additional sensors for detecting the force acting upon each wheel
and for detecting the level of the wheel in relation to the vehicle
body.
6. The arrangement according to claim 1, said steering link arms
further comprising an electrically actuated axial motor including a
displaceable rod connected to said wheel.
7. The arrangement according to claim 1 further comprising a
further link arm fitted between said wheel and another attachment
point on the body, said link arm comprising a torsion spring unit
for control of a level setting of said wheel and for an anti-roll
function of said wheel.
8. The arrangement according to claim 7, said torsion spring unit
further comprising an electro-rheological fluid for active control
of a spring force with which said link arm acts upon said
wheel.
9. The arrangement according to claim 7 further comprising a
control lever connected between said body and said further link
arm, wherein said control lever is operable for preloading the
spring force of said further link arm.
10. A vehicle comprising an arrangement according to claim 1.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation patent application of International
Application No. PCT/SE99/02476 filed Dec. 23, 1999 that designates
the United States. The full disclosure of said application, in its
entirety, is hereby expressly incorporated by reference into the
present application.
BACKGROUND OF INVENTION
[0002] 1. Technical Field
[0003] The present invention relates to a vehicular wheel
suspension arrangement comprising a wheel connected to propulsion
device for driving the vehicle, and a brake for braking each
individual wheel. More specifically, the invention relates to a
wheel suspension arrangement having one or more sensors for
detecting at least the angular steering displacement of a vehicle
required by the vehicle driver, at least two steering link arms
fitted between the vehicle body and attachment points in the wheel,
and a control unit for processing signals from the sensors and for
actuating the steering link arms for adjustments of the wheel in
response to the signals and the current operating state of the
vehicle. The invention is particularly intended for use as an
integrated wheel suspension unit for steering, propulsion and
braking of the respective wheel of an automotive vehicle.
[0004] 2. Background Information
[0005] In association with vehicles such as passenger cars, various
types of suspension systems are used for the wheels and axles. Such
wheel suspensions are arranged for allowing attachment and
resilient suspension of the vehicle wheels, in turn, enhancing the
comfort of the vehicle passengers and the road holding
characteristics and service life of the vehicle.
[0006] A multitude of different types of wheel suspension are
known. These suspensions are found in systems having, for example,
rigid or split wheel axles that may be supplemented as required by
spring members, shock absorbers and other components. In addition,
force-absorbing link arms connecting the vehicle wheels to its body
and anti-roll bars for reduction of excessive rolling motions of
the vehicle are often utilized.
[0007] Further, vehicles are normally designed with the vehicle
motive wheel axles connected to an engine such as a conventional
gasoline or diesel combustion engine. The connection between the
wheel axles and the engine is arranged via a gearbox and mechanical
transmission devices. Furthermore, the vehicle wheels are provided
with braking devices such as conventional disc or drum brakes,
actuated by depression of the vehicle brake pedal. In this way, the
brake devices at the wheels are actuated via a hydraulic brake line
system.
[0008] Also, vehicles are normally provided with a steering device
intended for giving the wheels a certain angular steering
displacement when the driver is turning the vehicle steering wheel.
The steering gear may have an input shaft with the steering wheel
connected to it, the input shaft transmits the steering wheel
movements to a pinion that in turn transmits the movements to a
rack. The rack movements are then transferred to the vehicle wheels
for steering the vehicle. This type of steering gear may be
complemented by a servo power device having a hydraulic cylinder
with a piston arranged on the steering rack. In this way, more
power is applied onto the rack when turning the steering wheel.
[0009] The equipment described above for propulsion, wheel
suspension, braking and steering is based on well-proven principles
that are frequently used today in automotive vehicle design.
Although these principles define a well functioning technique, they
exhibit certain limitations. For example, fitting all the
components mentioned above (i.e. engine, gearbox; transmission,
spring arrangement, anti-roll bars, brakes, steering, etc.) into a
relatively small space in the vehicle may prove to be a problem.
Furthermore, there may be difficulty in securely and cost
effectively interconnecting a large number of functions associated
with the wheel suspension system. Specifically, there may exist a
requirement for a high degree of integration of vehicle functions
for suspension and propulsion of the respective wheel.
SUMMARY OF INVENTION
[0010] The present invention provides an improved vehicle wheel
suspension arrangement, which could particularly be utilized as an
integrated wheel suspension unit with functions primarily for
steering, and preferably also for propulsion and braking, of each
individual vehicle wheel. This is achieved by means of an
arrangement as disclosed below.
[0011] The invention is comprised of an arrangement for an
automotive vehicle wheel suspension in which a wheel is connected
to both a propulsion device for driving the vehicle, and a braking
device for braking of the individual wheel. The invention has one
or more sensors for detecting at least the angular steering
displacement of the vehicle required by the vehicle driver. Two
steering link arms are fitted between the vehicle body and
attachment points in the wheel, positioned on both sides of an
imaginary vertical line running through the center of the wheel.
Furthermore, the invention has a control unit for processing
signals from the sensors and actuating the steering link arms for
adjustment of the wheel in response to the signals and the current
operating state of the vehicle.
[0012] The invention provides a number of advantages compared to
conventional wheel suspension systems. Primarily, it should be
noted that the invention constitutes a highly integrated wheel
suspension arrangement allowing individual adjustment of steering
displacement and wheel alignment of the respective wheels of a
vehicle. In this way, individual steering of each vehicle wheel is
allowed. Furthermore, a vehicle comprising the arrangement
according to the invention can be designed without any conventional
steering gear and/or steering column.
[0013] The invention is preferably arranged in connection with a
computer-based control unit having software functions for dynamic
adjustment of wheel alignment, in particular, the "camber" angle
and the "toe-in" angle of each respective wheel. In this manner a
vehicle constructed according to the invention can be designed
without any conventional mechanical wheel alignment requirements.
Furthermore, a vehicle equipped with the arrangement according to
the invention may have a "joystick" or similar control device,
thereby replacing the conventional steering wheel.
[0014] According to a preferred embodiment, the invention may
include a propulsion device in the form of an electric motor,
integrally arranged with each individual wheel. As such, the
vehicle may be designed without a conventional combustion engine,
gearbox or drive shaft connecting the individual wheel with the
propulsion device found on the vehicle chassis. Further, no
mechanical connections have to be fitted at the factory, which in
turn simplifies and reduces the cost of production.
[0015] According to a preferred embodiment of the invention, a
braking device is provided that is integrated into the electrical
motor. This design removes the need for any conventional drum or
disc brake arrangement.
[0016] Additionally, according to the embodiment there is a further
link arm connected between the respective wheel and the vehicle
body. The link arm is provided with a torsion spring unit for
controlling a level adjustment of the wheel and for an anti-roll
function of the wheel. In this way an advantage is achieved since
the vehicle does not require the provision of any conventional,
mechanical anti-roll bar.
[0017] Further advantageous embodiments of the invention are
provided in the following detailed description.
BRIEF DESCRIPTION OF DRAWINGS
[0018] The invention will be described in further detail below,
with reference to a preferred embodiment example and the appended
drawings, in which:
[0019] FIG. 1 illustrates a partial, cross-sectional side view, of
an arrangement according to the present invention from the front of
a wheel;
[0020] FIG. 2 illustrates a perspective view of how the arrangement
according to the invention could be arranged in practice on a
vehicle; and
[0021] FIG. 3 illustrates a block diagram of the structure of the
invention.
DETAILED DESCRIPTION
[0022] As required, detailed embodiments of the present invention
are disclosed herein; however, it is to be understood that the
disclosed embodiments are merely exemplary of the invention that
may be embodied in various and alternative forms. The figures are
not necessarily to scale, some features may be exaggerated or
minimized to show details of particular components or processes.
Therefore, specific structural and functional details disclosed
herein are not to be interpreted as limiting, but merely as a basis
for the claims and as a representative basis for teaching one
skilled in the art to variously employ the present invention.
[0023] FIG. 1 shows a partial, cross-sectional side view of an
arrangement according to the present invention. According to a
preferred embodiment, the arrangement is utilized as a wheel
suspension unit for an automotive vehicle, which preferably, but
not necessarily, consists of a passenger car. The figure shows in
principle how this wheel suspension unit according to the invention
could be arranged at one of the four wheels of such a vehicle.
Corresponding wheel suspension units would then preferably be
provided for all wheels of the vehicle in question.
[0024] Referring to FIG. 1, the wheel 1 is conventionally arranged
for rotation about an imaginary axis 2, and comprises a tire 3 and
a hub 4. The hub 4 is rotationally suspended by means of a wheel
bearing comprising an inner ring 5, which in turn is connected to
the hub 4 via a flange 6, extending radially in relation to the
axis 2. In a known manner, a number of wheel studs (not shown) may
be inserted through the flange 6 and screwed tight into
corresponding holes (not shown) in a surface of the inner ring 5
facing the flange 6. To this end, the flange 6 of the hub 4 is
provided with threaded holes (not shown) for such wheel studs.
[0025] The wheel bearing mentioned above also comprises an outer
ring 7 extending around the inner ring 5, and ball bearings 8
arranged between the inner ring 5 and the outer ring 7.
[0026] The invention further comprises a propulsion device
integrated into the wheel 1, preferably consisting of an electric
motor 9. The motor 9 has an armature 10 provided with motor coils
(not shown) and is fixedly attached to the outer ring 7. The motor
9 additionally may have a rotor 11 enclosed by the armature 10. The
rotor 11 rotates in relation to the outer ring 7 of the wheel
bearing. The outer ring 7 is thus stationary. To this end, the
outer ring 7 is designed like an annular sun gear having external
teeth meshing with a multitude of planetary gears 12 arranged
around the circumference of the outer ring 7. The number of
planetary gears 12 is preferably three, of which two can be seen in
FIG. 1.
[0027] FIG. 1 illustrates the invention in principle, and in a
somewhat simplified form. In practice, the armature 10 should be
connected to a separate component in the form of a hub carrier (not
shown), which would then be bolted to the armature 10.
[0028] The planetary gears 12 should be located around the outer
ring 7 at substantially the same pitch diameter as the
above-mentioned wheel studs. Furthermore, each planetary gear 12 is
rotationally supported on a planet carrier stud 13 impacted into a
hole in the hub flange 6. To this end, the inner ring 5 of the
wheel bearing is provided with through holes for passage of the
respective planet carrier stud 13.
[0029] The rotor 111 is connected to each planetary gear 12 via a
ring gear 14. This ring gear 14 is provided with internal teeth for
meshing with the corresponding teeth of the respective planetary
gear 12. The gear 14 is also provided with external splines for
non-rotating connection with the rotor 11 by means of a press fit.
The ring gear 14 is furthermore supported in relation to the outer
ring 7 of the wheel bearing, more specifically, against the outside
of the outer ring 7. This is indicated in FIG. 1 by further ball
bearings 15. Thus, the outer ring 7 of the wheel bearing defines an
inner race for the ring gear 14 of the planetary gear
transmission.
[0030] The armature 10 is connected to two steering link arms 16.
Only one steering link arm is shown in FIG. 1. According to what
will be described in detail below, the steering link arms 16 define
activation members functioning to provide dynamic wheel alignment
adjustment of the wheel 1 depending upon the current operating
state of the vehicle and the wheel 1. Examples of wheel alignment
angles that might be considered for adjustment are the "toe-in"
angle, i.e., an angle between the longitudinal axis of the vehicle
and an imaginary plane along the wheel 1, and the "camber" angle,
i.e., the angle of inclination of the wheel 1 in relation to an
imaginary plane extending perpendicularly to an underlying roadway.
Additionally, each steering link arm 16 is functioning to provide a
dynamic adjustment of an angular steering displacement of the wheel
1, depending upon both driver intent during driving and the current
operating state of the vehicle and the wheel 1. For adjustment of
the wheel 1, each steering link arm 16 is provided with a
displaceable rod 17 that can be actuated to be both extended out of
and withdrawn into the respective steering link arm 16, indicated
by an arrow in FIG. 1. The rod 17 is then actuated by a drive
member, preferably in the form of an electric axial motor, that is
an integral component in each steering link arm 16 (not shown in
detail in FIG. 1). The rod 17 is rotationally connected to the
armature 10 via a pivoting joint 18. Preferably, the attachment of
the respective rod 17 is made by means of a rubber bushing, as the
angles concerned are normally relatively small. Alternatively, the
attachment of the respective rod 17 could be made via a ball
joint.
[0031] The electric axial motor is a known type of drive member and
will not be described in detail here. As explained below, the
respective axial motor can be actuated by means of a computer-based
control unit for adjustment of the wheel alignment and the required
steering displacement of each individual wheel.
[0032] Each steering link arm 16 is fastened to the vehicle body 19
via additional attachment points 20 (of which only one attachment
point is shown in FIG. 1). Preferably, each attachment point 20
includes a rubber bushing.
[0033] According to the embodiment, the arrangement according to
the invention comprises a braking device in the form of a brake
actuator 21 arranged at the armature 10. Also, the brake actuator
21 preferably comprises an electric, linear axial motor, which
functions upon actuation to act upon a displaceable brake rod 22,
which in turn abuts against a pivoting member 23 that is suspended
in the armature 10. Upon actuation of the brake actuator 21, the
brake rod 22 causes the member 23 to pivot forcing a brake shoe 24
against an internal cylindrical surface of the rotor 11. The brake
shoe 24 is provided with a brake lining manufactured from a
material exhibiting a high friction against the interior surface of
the rotor 11. As such, a drum brake function is achieved enabling
the rotor 11 to be braked. According to what will be explained
below, this function may be actuated through depressing a brake
pedal located in the vehicle.
[0034] During operation of the engine 9 and therefore rotation of
the wheel 1, the planetary gearing in the hub is used for
increasing the rotational speed of the rotor 11 to about twice that
of the wheel. In this way, the torque requirement during propulsion
by the engine 9 can be reduced, which is an advantage. The
planetary gears 12 roll against the stationary outer ring 7. The
respective carrier studs 13 of the planetary gears 12 are arranged
in the inner ring 5 of the bearing, rotating at about half the
speed of the rotor 11. Through the aid of the planetary gearing,
only about half of the force of the stepped-up rotor 11 is required
during propulsion or braking of the wheel 1 versus if the rotor 11
had been fixedly arranged directly onto the hub of the wheel 1.
[0035] Further, according to one embodiment, the armature 10 is
connected to a second link arm in the form of a level link arm 25
that is pivotally mounted to the armature 10 in a similar fashion
as the steering link arms 16 mentioned above, via a further
attachment point 26 in the form of a rubber bushing or,
alternatively, a ball joint. The level link arm 25 functions to
provide level regulation and anti-roll of the wheel 1. To this end,
the level link arm 25 comprises an integral torsion spring unit 27,
which in turn is arranged around a through axle 28, thereby
defining an attachment into the vehicle body 19, preferably
extending substantially in the longitudinal direction of the
vehicle. The torsion spring unit 27 is preferably made of rubber or
a material having similar resilient properties. The attachment to
the body 19 is preferably realized through rubber bushings (not
shown), whereby the wheel 1 can be provided with a required
rigidity in the transversal and longitudinal directions. In doing
so, good performance regarding sound and vibration insulation in
the vehicle is provided.
[0036] Through a suitable adaptation of the material properties and
the construction of the torsion spring unit 27, a level control of
the wheel 1 is provided, that is, a control of the setting of the
vertical position of the wheel 1 in relation to the body 19.
Furthermore, with the aid of the torsion spring unit 27, the level
link arm 25 will function like an anti-roll bar for the cushioning
of excessively large rolling motions of the vehicle. In order to
optimize the road-holding properties of a vehicle, the stiffness of
the torsion spring unit 27 may be tuned to achieve a good anti-roll
function.
[0037] In order to simply and efficiently optimize the anti-roll
function of the torsion spring unit 27 to a current operating state
of the vehicle, the unit 27 might be based on the use of an
electro-rheological fluid. According to a known technique, such a
fluid can be used in resilient elements whereby a relatively high
electrical tension is applied over a certain amount of
electro-rheological fluid to influence its viscosity. In this way,
the torsion spring unit 27 can be utilized for an electrically
controlled, active cushioning.
[0038] In order to further enhance the level control function and
anti-roll function of the invention, the level link arm 25 may
preferably be connected to a control lever 29 including an
additional electrical axial motor (not shown). The control lever 29
includes a rod 30 that can be actuated by this axial motor for
displacement back and forth, as indicated by an arrow in FIG. 1.
The rod 30 is pivotally suspended in a link rod 31, which in turn
is fixedly attached to the shaft 28 to which the torsion spring
unit 27 is fastened. Further, the control lever 29 is pivotally
mounted to the vehicle body 19 via an additional pivoting joint 32.
In this manner, the control lever 29 may be utilized for providing
a certain preload to the torsion spring unit 27, which is provided
by means of appropriate operation of the link rod 31. Through this,
a variable level retention of each wheel 1 is enabled. Besides
this, an active "anti-lift" and "anti-dive" function of the vehicle
is enabled, i.e., the tendency of the vehicle body to lift at the
rear and at the front, during braking and acceleration can be
efficiently counteracted. Furthermore, in this way rigidity against
"rolling" motions of the vehicle is achieved, i.e., tendencies of
unwanted rotation around the longitudinal axis of the vehicle is
counteracted.
[0039] According to the invention, the torsion spring unit 27 is
provided with a variable preloading device. In case the torsion
spring unit 27 consists of a rubber spring, this preloading device
could comprise a rotating inner sleeve (not shown). The level
control is then achieved by rotation of the inner sleeve, whereby
the force at the end of the link arm 25 connected to the wheel 1
can be increased or decreased.
[0040] As such, the level link arm 25 transfers a resilient force
from the torsion spring unit 27. It may also transfer an anti-roll
force from the torsion spring unit 27 and its preloading device,
which may take place dynamically, e.g., while driving through
curves. Furthermore, the level link arm 25 transfers a
level-controlling force from the torsion spring unit 27 and its
preloading device, which best takes place in connection with a load
change of the vehicle.
[0041] According to the description below, the arrangement is
provided with a number of sensors for various parameters defining
the current operating state of the vehicle and its wheels. These
sensors (not shown in FIG. 1) are used for controlling the steering
link arms 16, the level link arm 25 and the control lever 29.
[0042] FIG. 2 illustrates from a perspective view one embodiment of
how the arrangement according to the invention could be arranged in
practice. As illustrated, two steering link arms 16,16" are
fastened to the body 19 through at least two rubber bushings 20,
20". The steering link arms 16, 16" are substantially identical in
shape and are pivotally attached via rods 17,17", respectively, to
attachment points 18,18" in the armature 10, arranged along
substantially the same horizontal plane. More particularly, the
steering link arms 16, 16" are attached on each side of an
imaginary vertical line 33 running through the center point of the
wheel 1. The steering link arms 16, 16" are further attached below
an imaginary horizontal line 34 running substantially in parallel
with the underlying roadway and through the center point of the
wheel 1. However, the invention is not limited to this location of
the steering link arms 16,16", but may be attached above the
horizontal line 34.
[0043] Referring to FIG. 2, the torsion spring unit 27 is arranged
around the axle 28, which is in turn connected to the vehicle
chassis 19 as explained above. The link rod 31 is also fastened to
the axle 28. The link rod 31 can thus be actuated by the control
lever 29 and its associated rod 30 for controlling the
level-regulation and anti-roll functions of the torsion spring unit
27. FIG. 2 illustrates a practical embodiment in which the link rod
is arranged extending in a direction away from the wheel 1, as an
alternative to what is shown in FIG. 1, where the link rod 31 is
shown extending in a direction towards the wheel 1. Thus, both of
these alternatives are conceivable within the scope of the
invention.
[0044] The attachment of the two steering link arms 16,16", the
level link arm 25 and the control lever 29 is made to the vehicle
body 19 as discussed above. Referring to FIG. 2, that part of the
body 19 to which the attachment is made preferably consists of a
frame-like member 35 serving as a dedicated attachment component.
This member 35 facilitates assembly of the arrangement onto a
vehicle. Through the frame element 35, the retaining of the
components as one single unit is also enabled. Furthermore, the
frame element 35 makes it possible to reduce the requirements for
accurate tolerances of the attachment points against the body.
[0045] Preferably, the two steering link arms 16,16" are
symmetrically arranged on the individual wheel of the vehicle. This
allows for the use of identical wheel suspension units in the
respective corners of the vehicle.
[0046] FIG. 3 shows in the form of a block diagram how the
arrangement could be arranged and utilized in a vehicle. Here, the
arrangement is utilized as an integrated wheel suspension unit for
electrical control of propulsion, angular alignment, steering and
braking of each individual wheel of the vehicle. Preferably, four
substantially identical wheel suspension units are used for each
respective wheel of the vehicle. Each wheel may then be controlled
independently of the others with respect to torque and wheel
alignment.
[0047] The invention is based upon the two steering links 16,16"
being controlled by a computer-based control unit 36, which
functions in receiving a number of signals from a corresponding
number of sensors. In this embodiment, the invention has a first
sensor 37 that generates a signal corresponding to the driver's
requirement for the angular steering displacement, or the steering
wheel angle of the vehicle. Such a sensor 37 may be an integrated
angle sensor in a conventional steering wheel or alternatively, may
be comprised as part of a "joystick" or similar steering control
device. Regardless of the embodiment used, a signal from this first
sensor 37 corresponding to the driver's steering commands is fed to
the control unit 36.
[0048] The first sensor 37 is preferably provided with a unit for
feedback of a force that provides a resistance or a movement of the
steering control device corresponding to the steering displacement
of the vehicle wheels. As an example, such a feedback force might
be provided an electrical motor arranged in the steering control
device. In this way the driver is given the feeling of a mechanical
connection between the steering wheel and the wheels.
[0049] Further, there is a second sensor 38 in the form of a force
sensor arranged in connection with each wheel of the arrangement.
This second sensor 38 is connected to the control unit 36 and emits
a signal corresponding to a measurement of the force from the
underlying roadway acting on the respective wheel. Such a force
sensor 38 is preferably arranged as close to each wheel as possible
and would, for example, consist of a strain gauge sensor fitted in
the wheel bearing discussed above. This sensor can be used for
detecting transversal forces acting on the wheel, allowing the
rolling resistance to be minimized by an appropriate alignment
setting of the wheel. The force sensor 38 can also be used for
detecting longitudinal forces acting upon the wheel, i.e., forces
acting in the longitudinal direction of the vehicle.
[0050] Furthermore, there is a third sensor 39 in the form of a
position sensor arranged in connection to each wheel. This third
sensor 39 emits to the control unit 36 a signal corresponding to a
measurement of the wheel level in relation to the body (i.e., the
vehicle ground clearance). The sensor may also be utilized for
detecting the roll angle of the vehicle (that is, to what degree
the vehicle is rotating around its longitudinal axis). The
suspension movement sensor 39 is preferably arranged between the
upper link arm 25 and the body 19 (compare FIG. 1).
[0051] With the signals emitted from at least the first sensor 37,
preferably also the second and third sensors 38, 39, to the control
unit 36, an appropriate setting of steering displacement and wheel
alignment of each wheel can be performed in response to the current
operating conditions of the vehicle. To achieve this, the control
unit 36 includes a data storage memory containing tables that
depending on different input data from the first sensor 37, second
sensor 38 and third sensor 39, calculates output values for control
of the function of the steering link arms 16,16". For example, the
signal from the first sensor 37 is utilized for the adjustment of a
required angular steering displacement of each wheel.
[0052] The invention can be utilized for actively controlling the
wheel alignment (e.g., the camber and toe-in angles) in order to
optimize these in response to current operating conditions of the
vehicle. For example, current transversal forces on the wheels,
wheel positions, and other operating parameters of the vehicle,
such as its speed and fuel consumption, can then be considered. The
invention can be used for providing optimum fuel economy, by
continuously optimizing the wheel alignment thereby minimizing the
rolling resistance of each wheel. The invention can also be used,
e.g., to counteract the influence of side wind against the vehicle
with a wheel alignment adjustment and a steering displacement that
is adapted to the least possible drag resistance. This will also
positively influence the fuel consumption. In this case, the
control unit 36 aligns the wheels so as to minimize the transversal
forces acting upon each individual wheel, those forces in turn
being detected by the force sensors 38. Further, the transversal
stability of the vehicle can be adapted through a continuous
adjustment of the camber angle of each wheel. Such a function may,
for example, be used by the driver to select by a suitable control
member, if an active or a more comfortable driving style is
preferred. Depending on the driving style selected and fed to the
control unit 36, the corresponding wheel settings can be set.
Furthermore, for continuous level regulation and control of the
anti-roll function, a control of the above control levers 29 may be
utilized.
[0053] Preferably, the system also comprises a fourth sensor 40 in
the form of a brake sensor. This sensor 40 is preferably arranged
in connection with a brake pedal (not shown) in the vehicle with
signals from the brake sensor 40, the brake actuator 21 can be
applied when the driver wishes to brake the vehicle. The invention
can also be used for applying the wheel brakes by
non-driver-induced braking actions, which may occur when anti-spin
and ABS functions are required in the vehicle. Preferably, the
functions of the respective brake actuators 21 and the respective
electrical motors 9 are coordinated during this type of control of
propulsion and braking of the wheels.
[0054] Other kinds of sensors may be of interest for detecting the
current driving conditions of the vehicle and its wheels. For
example, a fifth sensor in the form of an accelerometer 41 may be
used for feeding a signal corresponding to the current vehicle
acceleration to the control unit 36. Further, there may be a sixth
sensor 42 connected to the control unit 36, for indicating the
driver's throttle actuation for controlling the torque of the
individual electrical motors.
[0055] As discussed above, the invention functions in controlling
the wheel alignment and angular steering displacement of the
individual wheels. Furthermore, the control unit 36 functions in
response, for example, to a measurement of the driver's throttle
actuation, which could be detected by the sixth sensor 42 as a
position sensor for a throttle pedal, to control the motor in each
individual wheel so as to obtain an intended speed of the vehicle.
This type of control will not be described in detail here. However,
it should be noted that the brake arrangement is preferably
functioning in such a way that regenerative braking by the
respective electrical motor is performed before friction braking
via the brake shoe 24 is initiated.
[0056] Further, a seventh sensor 43 for transmitting a measurement
of the rotational speed of each wheel may be connected to the
control unit 36. In this manner, the invention can be used
(particularly at high vehicle speeds) for optimization of the wheel
alignment in order to provide a high degree of stabilization of the
vehicle. This seventh sensor 43 may be used for calculation of the
vehicle speed and the rotational changes of the individual wheels.
Based upon signals from the seventh sensor 43, for example, a
driving or a braking force may be applied to an individual wheel in
case an anti-spin and/or ABS function is required. Furthermore,
such signals can be used for registering the road friction during
slippery conditions.
[0057] In order to enable exact control of the steering link arms
16, 16", these components are preferably each provided with a
position sensor 44 and 45 for transmitting signals to the control
unit 36 that correspond to a measurement of the position of each
rod 17, 17" of the steering link arms 16, 16", i.e., a measurement
defining how far each rod 17, 17" has been extended out of its
associated steering link arm 16, 16". Preferably, the control lever
29 is also provided with a corresponding position detector 46 that
in like manner, sends a signal to the control unit 36 corresponding
to a measurement of the current position of the rod 30 associated
with the control lever 29.
[0058] Other sensors may also be utilized in connection with the
invention. For example, transversal accelerometers (at the front
and rear of the body) can be used for detecting the momentary
transversal acceleration of the vehicle. Furthermore, a yaw angle
sensor may be used for detecting the vehicle body rotational
movement as seen from above, i.e., for detecting any skidding
tendencies of the vehicle. Also, air speed sensors may be used at
the front corners of the vehicle for indicating air drag and wind
direction. Signals from such sensors could then be used for
controlling the alignment of the individual wheels of the vehicle
in a suitable way during travel, thereby minimizing drag.
[0059] Consequently, the invention can be used for individual
settings of angular steering displacement and wheel alignment for
each wheel of a vehicle. Following, it will be explained how the
invention can be used during various operating conditions of a
vehicle.
[0060] The camber angle of each wheel influences the transversal
stability of the vehicle. In order to set a suitable camber angle
of a given wheel, a set point for the angle may be calculated using
the level positions at the right and left hand sides of the
vehicle. As such, a signal from the first sensor 37, indicating the
steering displacement of the vehicle steering wheel, and a signal
from the second sensor 38, indicating the transversal force acting
on the wheels, are also considered. Preferably, a signal indicating
the transversal acceleration acting on the body is also utilized.
If, for example, the elevation is the same for the right and left
sides of the vehicle, the selected steering wheel position
corresponds to driving straight ahead, and the transversal forces
on the wheels and the transversal acceleration is substantially
zero, one can assume that the vehicle is driven straight ahead
without any inclination in relation to the horizontal plane. If
this is the case, the steering link arms 16, 16" can be adjusted to
make the camber angle for each wheel somewhat negative, resulting
in good vehicle transversal stability. A negative camber angle is
defined as the top of the wheel being somewhat inclined towards the
vehicle.
[0061] As the wheel moves resiliently in and out over road
obstacles without any turning of the steering wheel and transversal
acceleration occurring that affects the vehicle, the steering link
arms 16, 16" do not have to be activated for adjustment of the
wheel camber angles. If, on the other hand, the elevation is
different for the right and left side vehicle wheels at the same
time as the steering wheel is turned and the vehicle is subjected
to transversal acceleration, corresponding to the car entering a
curve, then the camber angle is preferably adjusted so as to place
the wheel theoretically vertical relative to the roadway.
[0062] Further, the toe-in angle of each wheel can be adjusted with
the aid of a measurement of the transversal forces on the wheel
according to what is being detected by the second sensor 38. Here,
the fact that the transversal wheel forces should be minimized in
order to achieve the lowest possible rolling resistance is
considered. Preferably, signals from the first sensor 37, the yaw
angle sensor, and the transversal accelerometers would also be
utilized during this kind of adjustment.
[0063] Furthermore, the invention can be used to make the vehicle
run level during curve negotiation. In this case, the steering
wheel angle sensor 37, level sensor 39 and preferably a speed
sensor for each wheel is utilized. During this operating state, the
control unit 36 is used to calculate what degree the control lever
29 should be activated for preloading the torsion spring unit 27 in
order to make the car run substantially level when driving through
a curve.
[0064] When driving with a side wind against the vehicle body, the
invention can be used for counteracting the force acting upon the
vehicle. In a strong side wind, the force sensors 38 at the wheels
are affected without the body being influenced by any transversal
acceleration while the steering wheel is in a position
corresponding to driving straight ahead. As long as such a
transversal force exists, the respective steering link arms 16, 16"
are controlled in such a way that the wheels at the front and rear
are steering so as to make the car still run straight ahead yet
slightly diagonally (a so-called "dog walk"), i.e., the body is
turned somewhat into the wind. The wheel force sensors, the body
yaw angle sensor and the transversal accelerometers will respond to
side wind changes, gusts of wind and during overtaking, which
quickly changes the incoming force of the side wind. The control
unit may then function in initiating a quick counter-steering of
the wheels to minimize yaw and drift.
[0065] During special operating conditions, such as parking, the
invention could be used for four-wheel steering, facilitating the
maneuvering of the vehicle. Four-wheel steering can be used for
decreasing the turning circle of the vehicle as well as for
enhancing its high-speed stability. For example, a diagonal
movement away from or towards a curb could be performed in
connection with a parking maneuver.
[0066] According to the invention, four-wheel steering may be
automatically activated if required, preferably while driving the
vehicle at a speed below a certain limit (detectable through the
wheel rotational speed sensor 43). When driving at relatively high
speeds, the invention can also be used for steering the rear wheels
somewhat, thereby contributing to a high stability of the
vehicle.
[0067] Another example of an application of the invention is when
the vehicle is heavily loaded and there are requirements for
adapting the height level of the chassis above the roadway in
response to the weight of the load. This level adaptation could be
performed through appropriate control of the control levers 29
mentioned above.
[0068] Other embodiments of the invention may be recognized. For
example, the invention could be achieved using a conventional
engine, e.g., a combustion engine provided in the vehicle chassis
and connected to the vehicle drive wheels via a conventional
mechanical connection. Further, a conventional braking device could
be utilized as an alternative to the above-mentioned electrical
brake. Further, the invention can be utilized in various types of
vehicles, such as passenger cars, trucks and buses.
[0069] The invention in its simplest form can be implemented with
the two steering link arms 16, 16", which are then arranged as
discussed above, that is, fitted between the vehicle body and
attachment points at each wheel, located on both sides of an
imaginary vertical line running through the center of the wheel.
The minimum sensors used by the invention are, in this case, a
sensor for the steering wheel angular displacement required by the
driver. Preferably, the above-mentioned position sensors 44, 45 for
sensing the positions of the rods 17, 17" of the two steering link
arms 16, 16," would also be used. Such an arrangement would allow
control of the angular steering displacement and the wheel
alignment, e.g., the camber angle, of each individual wheel.
[0070] In principle, the electrical devices for propulsion and
braking could be replaced, completely or in part, by hydraulic
power transmission devices (steering link arms, spring, level
control, anti-roll and shock-absorber elements and wheel motors),
without departing from the basic principle of the invention. For
example, the electrical axial motors mentioned above could be
replaced by hydraulic cylinders. In the case of electrical
actuators being used, these should be made self-braking in order to
absorb transversal forces acting on the wheels during driving.
[0071] In case the electrical propulsion is replaced by hydraulic
propulsion, the function of the planetary gear arrangement would
best be reversed in comparison to what has been described above. In
this alternative embodiment, hydraulic motors would be connected to
the planetary gears, doubling the rotational speed of the car
wheels. With hydraulic propulsion, a number of components such as
hydraulic pumps, valves and lines would also be added. The friction
brake mentioned above would however be eliminated, as the hydraulic
motors could be shut off completely, if required, so as to lock the
wheels into a stationary position.
[0072] The above-mentioned braking arrangement could be realized in
various ways. As an example, the brake lining could be arranged to
act on the exterior of the rotor instead of its interior. One
advantage of this arrangement would be that excess frictional heat
generation is avoided in that portion of the rotor acting as a
motor. Alternatively, the rotor might also be arranged so as to
enclose the armature, i.e., the rotor would rotate closest to the
wheel rim, thereby increasing the possibilities for efficient
cooling of the motor.
[0073] The torsion spring unit 27 may be based on, e.g., a rubber
spring or a steel spring.
[0074] According to a further alternative embodiment, the comfort
properties of the vehicle in question may be enhanced by
interconnecting the two steering link arms in such a way that they
follow each other in the vertical direction but are substantially
independent of each other in the horizontal direction.
[0075] Furthermore, the spring rate of the torsion spring unit
could be made progressive, rendering increased spring hardness to a
relatively heavily loaded vehicle.
[0076] According to a further alternative embodiment, the level
link arm could be provided at an extended portion of the armature
10 (a so-called "swan neck"), placing the top attachment point of
the level link arm at a point above the tire. This would provide
longer leverage for absorbing transversal forces on the wheel.
[0077] A parking brake function could further be obtained through
an activation of the electrical brakes, conceivably in combination
with placing all the wheels at an angle relative to each other, or
a "stemming position". This would make the vehicle difficult to
roll and to tow away.
[0078] The torsion spring unit could alternatively be of the
hydro-pneumatic type, allowing also for anti-roll and level control
functions.
[0079] Although the present invention has been described and
illustrated in detail, it is to be clearly understood that the same
is by way of illustration and example only, and is not to be taken
as a limitation. The spirit and scope of the present invention are
to be limited only by the terms of any claims presented
hereafter.
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