U.S. patent application number 09/726057 was filed with the patent office on 2002-05-30 for steering column differential angle position sensor.
Invention is credited to Lin, Yingjie, Nicholson, Warren Baxter, Thomson, Steven Douglas.
Application Number | 20020065592 09/726057 |
Document ID | / |
Family ID | 22713070 |
Filed Date | 2002-05-30 |
United States Patent
Application |
20020065592 |
Kind Code |
A1 |
Lin, Yingjie ; et
al. |
May 30, 2002 |
STEERING COLUMN DIFFERENTIAL ANGLE POSITION SENSOR
Abstract
A steering column differential angle position sensor includes an
upper flux shutter and a lower flux shutter. Each flux shutter
forms a plurality of similarly shaped openings that are equally
spaced radially around the shutters. A receiver coil and a
transmitter coil are coaxially aligned with the shutters. A hollow
housing surrounds the shutters and the coils. The transmitter coil
provides a magnetic field around the shutters and the receiver coil
is used to sense changes in the magnet flux reaching the receiver
coil due to differential motion of the flux shutters. Accordingly,
a microprocessor electrically coupled to the sensor determines the
torque on a steering column that is mechanically coupled to the
sensor using a signal output by the sensor representing the change
in flux reaching the receiver coil.
Inventors: |
Lin, Yingjie; (El Paso,
TX) ; Nicholson, Warren Baxter; (El Paso, TX)
; Thomson, Steven Douglas; (El Paso, TX) |
Correspondence
Address: |
MARGARET A. DOBROWITSKY
DELPHI TECHNOLOGIES, INC.
Legal Staff, Mail Code: 480-414-420
P.O. Box 5052
Troy
MI
48007-5052
US
|
Family ID: |
22713070 |
Appl. No.: |
09/726057 |
Filed: |
November 29, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60193304 |
Mar 30, 2000 |
|
|
|
Current U.S.
Class: |
701/41 ;
701/42 |
Current CPC
Class: |
G01L 3/101 20130101;
G01L 5/221 20130101; B62D 6/10 20130101; G01D 5/2053 20130101; G01L
3/105 20130101 |
Class at
Publication: |
701/41 ;
701/42 |
International
Class: |
B63G 008/20 |
Claims
1. A sensor for measuring differential angular displacement between
a first shaft segment and a second shaft segment, comprising: a
first flux shutter coupled to the first shaft segment, the first
flux shutter forming a plurality of openings; a second flux shutter
coupled to the second shaft segment and coaxially aligned with the
first flux shutter, the second flux shutter forming a plurality of
openings; at least one transmitter coil energizable to provide a
magnetic field around the flux shutters; and at least one receiver
coil sensing a change in the magnetic flux reaching the receiver
coil when the flux shutters move relative to each other, the sensor
outputting a signal representative of the differential angular
orientation of the flux shutters.
2. The sensor of claim 1, further comprising: a housing surrounding
the coils and the flux shutters.
3. The sensor of claim 2, further comprising: a torsion bar
mechanically coupling the first shaft and the second shaft.
4. The sensor of claim 2, wherein the housing defines a vertical
axis and the flux shutters are disposed within the housing
perpendicular to the axis.
5. The sensor of claim 1, wherein the receiver coil is surrounded
by a first flux concentrator and the transmitter coil is surrounded
by a second flux concentrator.
6. The sensor of claim 1, further comprising: at least one
reference target coaxially aligned with the flux shutters; and at
least one reference coil coaxially aligned with the flux shutters,
the reference coil and reference target being used to compensate
for changes in the sensor caused by temperature changes.
7. A power steering control system comprising: a microprocessor; a
power source; and a steering column differential angle position
sensor electrically coupled to the microprocessor, electrically
coupled to the power source and mechanically coupled to a steering
column, the differential angle position sensor transmitting a
signal to the microprocessor representing a differential angular
displacement between a first flux shutter and a second flux
shutter.
8. The power steering control system of claim 7, further
comprising: a vehicle control system connected to the
microprocessor.
9. The power steering control system of claim 7, wherein the
steering column differential angle position sensor comprises: a
first flux shutter coupled to a first steering shaft segment, the
first flux shutter forming a plurality of openings; a second flux
shutter coupled to a second steering shaft segment and coaxially
aligned with the first flux shutter, the second flux shutter
forming a plurality of openings; at least one transmitter coil
coaxially aligned with the flux shutters, the transmitter coil
being energized to provide a magnetic field around the flux
shutters; and at least one receiver coil coaxially aligned with the
flux shutters, the receiver coil sensing a change in the magnetic
field when the flux shutters move relative to each other, the
sensor outputting a signal representative of the differential
angular orientation of the flux shutters.
10. The system of claim 9, wherein the sensor further comprises: a
housing surrounding the coils and the flux shutters.
11. The system of claim 9, further comprising: a torsion bar
mechanically coupling the first steering shaft and the second
steering shaft.
12. The system of claim 10, wherein the housing defines a vertical
axis and the flux shutters are disposed within the housing
perpendicular to the axis.
13. The system of claim 9, wherein the receiver coil is surrounded
by a first flux concentrator and the transmitter coil is surrounded
by a second flux concentrator.
14. The system of claim 9, wherein the sensor further comprises: at
least one reference target coaxially aligned with the flux
shutters; and at least one reference coil coaxially aligned with
the flux shutters, the reference coil and reference target being
used to compensate for changes in the sensor caused by temperature
changes.
15. A method for controlling a power steering system comprising the
acts of: installing a first flux shutter on a first steering shaft
segment; installing a second flux shutter on a second steering
shaft segment; sensing a differential angular position between the
first flux shutter and the second flux shutter; and generating a
signal representing the differential angular position.
16. The method of claim 15, further comprising the act of:
processing the signal to determine a torque on a steering column
based on the differential angular position.
17. The method of claim 15, further comprising the act of: sending
a signal representing the torque on the steering column to a
control system.
Description
RELATED APPLICATIONS
[0001] The present application claims priority from provisional
U.S. patent application serial No. 60/193,304, filed Mar. 30,
2000.
TECHNICAL FIELD
[0002] The present invention relates to steering column torque
sensors.
BACKGROUND OF THE INVENTION
[0003] Power assisted steering is a standard motor vehicle
equipment feature. It happens that in order for a typical power
steering control system to properly operate, a steering column
torque sensor must be included in the system to close the control
loop. Torque sensors, such as resistance strip/strain gauge
sensors, capacitance sensors, eddy-current sensors, magneto-elastic
sensors, and transformer/strain gauge sensors, have been provided
to determine the torque on the steering column. However, these
sensors lack the sensitivity required for many of the present power
steering control systems. Moreover, these sensors are extremely
sensitive to changes in temperature and have limited
durability.
[0004] The present invention has recognized the above-mentioned
prior art drawbacks, and has provided the below-disclosed solutions
to one or more of the prior art deficiencies. More specifically,
the present invention understands that for reliability, durability,
and sensitivity reasons, a non-contact torque sensor can be used to
measure torque on a rotating shaft.
SUMMARY OF THE INVENTION
[0005] A sensor for measuring differential angular displacement
between a first shaft segment and a second shaft segment includes a
first flux shutter that is coupled to the first shaft segment and a
second flux shutter that is coupled to the second shaft segment.
The second flux shutter is coaxially aligned with the first flux
shutter, and the first flux shutter and the second flux shutter
form a plurality of openings. The sensor also includes at least one
transmitter coil that is energizable to provide a magnetic field
around the flux shutters and at least one receiver coil that senses
a change in the magnetic flux that reaches the receiver coil when
the flux shutters move relative to each other. The sensor outputs a
signal representative of the relative angular orientation of the
flux shutters.
[0006] In a preferred embodiment, a housing surrounds the coils and
the flux shutters. Preferably, a torsion bar couples the first
shaft and the second shaft. Moreover, the housing defines a
vertical axis and the flux shutters are disposed within the housing
perpendicular to the axis. In the preferred embodiment, the
receiver coil is surrounded by a first flux concentrator and the
transmitter coil is surrounded by a second flux concentrator. The
sensor further includes at least one reference target coaxially
aligned with the flux shutters and at least one reference coil
coaxially aligned with the flux shutters. The reference coil and
reference target are used to compensate for changes in the sensor
caused by temperature changes.
[0007] In another aspect of the present invention, a power steering
control system includes a microprocessor, a power source, and a
steering column differential angle position sensor. The steering
column differential angle position sensor is electrically coupled
to the microprocessor, electrically coupled to the power source and
mechanically coupled to a steering column. The position sensor
transmits a signal to the microprocessor that represents an angular
displacement between a first flux shutter and a second flux
shutter.
[0008] In yet another aspect of the present invention, a method for
controlling a power steering system includes installing a first
flux shutter on a first steering shaft segment and installing a
second flux shutter on a second steering shaft segment. In this
aspect of the present invention, the method also includes sensing a
differential angular position between the first flux shutter and
the second flux shutter and generating a signal representing the
differential angular position.
[0009] The present invention will now be described, by way of
example, with reference to the accompanying drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a perspective view of a steering column;
[0011] FIG. 2 is a cross-sectional view of a steering column
differential angle position sensor as seen in box 2 in FIG. 1;
[0012] FIG. 3 is a top plan view of the upper flux shutter;
[0013] FIG. 4 is a block diagram representing a vehicle steering
control system.
DESCRIPTION OF AN EMBODIMENT OF THE INVENTION
[0014] Referring initially to FIG. 1, a motor vehicle steering
column is shown and generally designated 10. FIG. 1 shows that the
steering column includes an upper steering shaft 12 and a lower
steering shaft 14 connected by a torsion bar 16. As shown in FIG.
1, the upper steering shaft 12 is connected to a steering wheel 18.
The lower steering shaft 14 is connected to a rack and pinion (not
shown) or other steering mechanism coupled to the wheels of a
vehicle. It is to be appreciated that the steering column
differential angle position sensor, described below, is installed
along the steering column 10 at the junction of the upper and lower
steering shafts 12, 14, i.e., around the torsion bar 16 in the area
indicated by dashed box 2.
[0015] Referring to FIG. 2, a steering column differential angle
position sensor is shown and generally designated 20. FIG. 2 shows
that the steering column differential angle position sensor 20
includes a hollow, toroidal housing 22 that, in a preferred
embodiment, is manufactured from a non-ferromagnetic material.
Within the housing 22 and circumscribing the upper steering shaft
12, is a generally disk-shaped receiver coil 24 closely surrounded
by an upper flux concentrator 26. As shown in FIG. 2, the sensor 20
also includes a solid, preferably metal, generally disk-shaped
reference target 28 sandwiched between a generally disk-shaped
transmitter coil 30 and a generally disk-shaped reference coil 32.
The transmitter coil 30, reference target 28, and reference coil 32
are closely surrounded by a lower flux concentrator 34 and
circumscribe the lower steering shaft 14. Preferably, the upper and
lower flux concentrators 26, 34 are manufactured from a high
permeability soft magnetic material which allows the concentrators
26, 34 to contain and concentrate the magnetic flux from the coils
24, 30, 32. In a preferred embodiment, the coils 24, 30, 32 are
made using printed circuit or bonded coil technology.
[0016] Continuing to refer to FIG. 2, a generally disk-shaped upper
flux shutter 36 and a generally disk-shaped lower flux shutter 38
are disposed within the sensor housing 22. Preferably, the upper
flux shutter 36 and lower flux shutter 38 are manufactured from a
high permeability soft magnetic material. FIG. 2 shows that the
upper flux shutter 36 is rigidly affixed to the upper steering
shaft 12 and rotates with the upper steering shaft. Conversely, the
lower flux shutter 38 is rigidly affixed to the lower steering
shaft 14 and, accordingly, rotates therewith. It may now be
appreciated that any torque on the upper steering shaft 12 will
turn the upper flux shutter 36 relative to the lower flux shutter
38. As shown in FIG. 2, a printed circuit board 40 is also disposed
within the sensor housing 22.
[0017] FIG. 2 shows that the flux shutters 36, 38 are installed
within the housing 22 such that they are parallel to each other and
parallel to the coils 24, 30, 32. As shown in FIG. 2, the steering
shafts 12, 14 define an axis 42 and the sensor 20 is installed
around the steering shafts 12, 14 such that the internal components
of the sensor 20, e.g., the coils 24, 30, 32 and flux shutters 36,
38, are perpendicular to the axis 42. Moreover, the flux shutters
36, 38 and the coils 24, 30, 32 are coaxially aligned with each
other within the housing along the axis 42.
[0018] Referring now to FIG. 3, the upper flux shutter 36 is shown.
FIG. 3 shows that the upper flux shutter 36 is formed with a
plurality of equally sized and shaped openings 44 that are equally
radially spaced around the flux shutter 36. It is to be appreciated
that the size and shape of the shutter openings 44 can be altered
depending on the measurement range of the sensor 20 and the
transfer function of the magnetic circuit formed by the coils 24,
30, 32. It is also to be appreciated that the lower flux shutter 38
(not shown in FIG. 3) includes the same number of openings as the
upper flux shutter 36.
[0019] Preferably, the centers of the openings 44 formed by the
flux shutters 36, 38 are placed the same distance from the centers
of the flux shutters 36, 38 and are equally radially spaced around
the flux shutters 36, 38. However, in a preferred embodiment, the
openings formed by one of the flux shutters 36, 38, e.g., the lower
flux shutter 36, are relatively smaller than the openings 44 formed
by the upper flux shutter 38 to compensate for any unwanted
transverse motion of the lower flux shutter 36 relative to the
upper flux shutter 38.
[0020] Without any torque applied to the torsion bar 16, the
openings 44 formed by the upper flux shutter 36 and the openings 44
formed by the flux shutter 38 are approximately fifty percent (50%)
overlapped. At zero torque, approximately fifty percent (50%) of
the total possible open area of the flux shutters 36, 38 between
the transmitter coil 30 and the receiver coil 24 is available.
However, when a torque is applied to the upper steering shaft 12
and friction such as tire to road friction is present on the lower
shaft 14, the torsion bar 16 twists at a predetermined spring rate.
The twisting of the torsion bar 16 creates a differential angle
between the flux shutters 36, 38 which changes the open area
through the flux shutters 36, 38. The direction of applied torque,
either clockwise or counter-clockwise, is also of interest. When a
torque is applied in one direction on the upper shaft 12, the open
area through the flux shutters 36, 38 will increase from fifty
percent (50%) to near one hundred percent (100%). On the other
hand, when a torque is applied to the upper shaft 12 in the
opposite direction, the open area through the flux shutters 36, 38
decreases from fifty percent (50%) to near zero percent (0%). As
the area through the flux shutters 36, 38 increases, the amount of
flux reaching the receiver coil 24 increases, and as such, the
voltage present across the receiver coil 24 increases. Likewise, as
the area through the flux shutters 36, 38 decreases, the voltage
across the receiver coil 24 decreases. The change in voltage at the
receiver coil 24 is used to determine the differential angle
between the upper flux shutter 36 and the lower flux shutter 38.
Moreover, the direction of motion between the flux shutters 36, 38
can be determined.
[0021] By knowing the differential angle between the upper flux
shutter 36 and the lower flux shutter 38 the angle of twist between
the top and bottom of the torsion bar 16 can be determined. As is
known in the art, by knowing the torsional spring rate and the
angle of twist, the torque acting on the torsion bar during
steering can be determined and a steering control system can
compensate accordingly.
[0022] Thus, by energizing the transmitter coil 30 to create a
magnetic field around the flux shutters 36, 38 and using the
receiver coil 24 to sense changes in the flux caused by relative
motion between the upper and lower flux shutters 36, 38, a torque
on the steering column 10 that is mechanically coupled to the
sensor 20 can be determined by a microprocessor, described below.
As intended herein, the reference coil 32 and reference target 28
are used to provide a reference output that varies due to
temperature changes in the flux shutters 36, 38 and coils 24, 30.
The reference sensor output is used to compensate the main sensor
output due to temperature effects.
[0023] Referring now to FIG. 4, a block diagram representing a
steering system is shown and designated 50. FIG. 4 shows that the
steering system 50 includes the steering column differential angle
position sensor 20, which is electrically coupled to a
microprocessor 52 via electrical line 54. FIG. 4 also shows that
the steering column differential angle position sensor 20 is
electrically coupled to a power source 56 via electrical line 58
and mechanically coupled to the steering column 10 as described
above.
[0024] Accordingly, the microprocessor 52 processes the signals
sent from the sensor 20 to determine a steering column 10 torque
based on the differential angular positions of the upper and lower
flux shutters 36, 38. The microprocessor 52 can then control a
vehicle control system 60 using the steering column 10 torque
signal.
[0025] It is to be appreciated that the receiver coil 24 and the
reference coil 32 may include a capacitor across the terminals of
each coil 24, 32 to resonate these coils 24, 32 at the frequency of
the transmitter coil 30 and produce higher voltages in the receiver
coil 24 and reference coil 32.
[0026] With the configuration of structure described above, it is
to be appreciated that the steering column differential angle
position sensor 20 provides a relatively sensitive, relatively
compact, and relatively durable means for determining the torque on
a steering column 10 based on the change in magnetic flux reaching
the receiver coil 24 due to the relative position of the upper flux
shutter 36 and the lower flux shutter 38.
[0027] While the particular steering column differential angle
position sensor 20 as herein shown and described in detail is fully
capable of attaining the above-described objects of the invention,
it is to be understood that it is the presently preferred
embodiment of the present invention and thus, is representative of
the subject matter which is broadly contemplated by the present
invention, that the scope of the present invention fully
encompasses other embodiments which may become obvious to those
skilled in the art, and that the scope of the present invention is
accordingly to be limited by nothing other than the appended
claims, in which reference to an element in the singular is not
intended to mean "one and only one" unless explicitly so stated,
but rather "one or more." All structural and functional equivalents
to the elements of the above-described preferred embodiment that
are known or later come to be known to those of ordinary skill in
the art are expressly incorporated herein by reference and are
intended to be encompassed by the present claims. Moreover, it is
not necessary for a device or method to address each and every
problem sought to be solved by the present invention, for it is to
be encompassed by the present claims. Furthermore, no element,
component, or method step in the present disclosure is intended to
be dedicated to the public regardless of whether the element,
component, or method step is explicitly recited in the claims. No
claim element herein is to be construed under the provisions of 35
U.S.C. section 112, sixth paragraph, unless the element is
expressly recited using the phrase "means for."
* * * * *