U.S. patent application number 09/747729 was filed with the patent office on 2001-10-18 for bearing condition monitor for a vehicle, such as a truck or a trailer.
Invention is credited to Brown, James B. JR., Ehrlich, Donald J., Ehrlich, Rodney P., McCann, Gerard O..
Application Number | 20010030466 09/747729 |
Document ID | / |
Family ID | 22624958 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010030466 |
Kind Code |
A1 |
Ehrlich, Donald J. ; et
al. |
October 18, 2001 |
Bearing condition monitor for a vehicle, such as a truck or a
trailer
Abstract
A system for monitoring bearing health of a wheel of a vehicle,
such as a trailer, is provided. The system is configured to monitor
at least one characteristic relating to the wheel bearings, such as
a temperature, vibrations, and/or proximity. The monitoring system
may be configured to monitor more than one of these characteristics
(i.e., temperature, vibration and proximity) or even all three. The
system is incorporated into a wheel speed sensor. The system may be
incorporated in an anti-lock brake system (ABS) or
electro-pneumatic brake system (EBS). Regardless of which
characteristic is actually monitored by the system and whether the
system is employed with an ABS or EBS, the bearing monitoring
system provides that one or more bearings of a vehicle can be
continuously and automatically monitored in the field.
Inventors: |
Ehrlich, Donald J.;
(Lafayette, IN) ; Ehrlich, Rodney P.; (Monticello,
IN) ; McCann, Gerard O.; (Lafayette, IN) ;
Brown, James B. JR.; (Lafayette, IN) |
Correspondence
Address: |
TREXLER, BUSHNELL, GIANGIORGI,
BLACKSTONE & MARR, LTD.
105 W. ADAMS STREET
CHICAGO
IL
60603
US
|
Family ID: |
22624958 |
Appl. No.: |
09/747729 |
Filed: |
December 22, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60171741 |
Dec 22, 1999 |
|
|
|
Current U.S.
Class: |
303/191 ;
180/271 |
Current CPC
Class: |
F16C 19/548 20130101;
F16C 2326/02 20130101; G01P 3/488 20130101; B60T 8/00 20130101;
G01P 1/026 20130101; G01P 3/487 20130101; B60T 8/329 20130101; F16D
55/227 20130101; B60T 8/171 20130101; F16D 2125/40 20130101; B60G
2204/115 20130101; F16D 2121/24 20130101; G01P 3/443 20130101; F16C
2233/00 20130101; F16C 19/52 20130101; B60W 30/18036 20130101; B60T
17/22 20130101; B60T 2230/08 20130101; F16D 2051/003 20130101; G01M
13/04 20130101; G01M 13/045 20130101 |
Class at
Publication: |
303/191 ;
180/271 |
International
Class: |
B60T 008/32 |
Claims
The invention claimed is:
1. A bearing monitoring system for a vehicle comprising: an axle; a
wheel mounting apparatus surrounding said axle, said wheel mounting
apparatus including at least one bearing; a wheel mounted on said
wheel mounting apparatus; a sensor member mounted on said axle,
said sensor member having a first sensing element mounted thereon
for use in determining the temperature of said at least one
bearing; and circuitry for processing information from said sensor
member regarding the temperature of said at least one bearing and
for performing a function on the vehicle depending on the
information sensed by said first sensing element.
2. A bearing monitoring system as defined in claim 1, wherein said
circuitry is part of an anti-lock brake system or an
electro-pneumatic brake system for the vehicle.
3. A bearing monitoring system as defined in claim 1, wherein said
first sensing element is an application specific integrated
circuit.
4. A bearing monitoring system as defined in claim 1, wherein said
axle including at least two wheel mounting assemblies surrounding
said axle, each said wheel mounting apparatus including at least
one bearing; a wheel mounted on each said wheel mounting apparatus;
a sensor member mounted on each said axle and associated with each
said wheel, each said sensor member having a first sensing element
mounted thereon for use in determining the temperature of said at
least one bearing associated with said respective wheel; the
information from each said sensor member being transmitted to said
circuitry, and wherein said circuitry compares the information from
each said sensor member prior to performing said function.
5. A bearing monitoring system as defined in claim 1, wherein two
axles are provided, said axle including at least two wheel mounting
assemblies surrounding said axle, each said wheel mounting
apparatus including at least one bearing; a wheel mounted on each
said wheel mounting apparatus; a sensor member mounted on each said
axle and associated with each said wheel, each said sensor member
having a first sensing element mounted thereon for use in
determining the temperature of said at least one bearing associated
with said respective wheel; the information from each said sensor
member being transmitted to said circuitry, and wherein said
circuitry compares the information from each said sensor member
prior to performing said function.
6. A bearing monitoring system as defined in claim 1, wherein said
sensor member further includes a second sensing element mounted
thereon for use in determining the vibrations of one or more
elements of the wheel mounting apparatus; and wherein said
circuitry is capable of processing information from said second
sensing element regarding the acceleration of said wheel.
7. A bearing monitoring system as defined in claim 6, further
including a signal wire connected between said sensor member and
said circuitry, wherein said information from said sensor member
regarding the temperature of said at least one bearing and said
information from said sensor member regarding the acceleration of
said wheel are transmitted to said circuitry on said signal
wire.
8. A bearing monitoring system as defined in claim 7, wherein said
sensor member further includes a third sensing element mounted
thereon for use in determining the direction of rotation of said
wheel; and wherein said circuitry is capable of processing
information from said sensor member regarding the direction of
rotation of said wheel, said information from said sensor member
regarding the direction of rotation of said wheel is transmitted to
said circuitry on said signal wire.
9. A bearing monitoring system as defined in claim 7, further
including an element mounted on said wheel mounting apparatus; and
wherein said sensor member further includes a fourth sensing
element mounted thereon for use in determining the proximity of
said element relative thereto by sensing the position of said
element; and wherein said circuitry is capable of processing
information from said fourth sensing element regarding the
proximity of said element, said information from said sensor member
regarding the proximity of said element is transmitted to said
circuitry on said signal wire.
10. A bearing monitoring system as defined in claim 1, further
including an element mounted on said wheel mounting apparatus; and
wherein said sensor member further includes a second sensing
element mounted thereon for use in determining the radial and/or
axial proximity of said element relative thereto by sensing the
radial and/or axial position of said element; wherein said
circuitry is capable of processing information from said sensor
member regarding the radial and/or axial position of said
element.
11. A bearing monitoring system as defined in claim 1, further
including an element mounted on said wheel mounting apparatus;
wherein said sensor member further includes a second sensing
element mounted thereon for use in sensing vibrations of one or
more elements of the wheel mounting apparatus and a third sensing
element mounted thereon for use in determining the radial and/or
axial proximity of said element relative thereto by sensing the
position of said element; and wherein said circuitry is capable of
processing information from said sensor member regarding the
vibrations of one or more elements of the wheel mounting apparatus
and said circuitry is capable of processing information from said
sensor member regarding the radial and/or axial position of said
element.
12. A bearing monitoring system as defined in claim 1, wherein said
sensor member further includes a second sensing element mounted
thereon for use in determining the speed of rotation of said wheel;
and wherein said circuitry is capable of processing information
from said second sensing element regarding the speed of said
wheel.
13. A bearing monitoring system as defined in claim 12, further
including an exciting element mounted on said wheel mounting
apparatus; and wherein said second sensing element determines the
speed of rotation of said wheel by sensing said exciting
element.
14. A bearing monitoring system for a vehicle comprising: an axle;
a wheel mounting apparatus surrounding said axle, said wheel
mounting apparatus including at least one bearing; a wheel mounted
on said wheel mounting apparatus; a sensor member mounted on said
axle, said sensor member having a first sensing element mounted
thereon for use in sensing vibrations of one or more elements of
the wheel mounting apparatus; and circuitry for processing
information from said sensor member regarding the vibrations of one
or more elements of said wheel mounting apparatus and for
performing a function on the vehicle depending on the information
sensed by said first sensing element.
15. A bearing monitoring system as defined in claim 14, wherein
said circuitry is part of an anti-lock brake system or an
electro-pneumatic brake system for the vehicle.
16. A bearing monitoring system as defined in claim 14, wherein
said first sensing element is a silicon micromachined integrated
circuit.
17. A bearing monitoring system as defined in claim 14, wherein
said axle including at least two wheel mounting assemblies
surrounding said axle, each said wheel mounting apparatus including
at least one bearing; a wheel mounted on each said wheel mounting
apparatus- a sensor member mounted on each said axle and associated
with each said wheel, each said sensor member having a first
sensing element mounted thereon for use in sensing vibrations of
one or more elements of each said wheel mounting apparatus; the
information from each said sensor member being transmitted to said
circuitry, and wherein said circuitry compares the information from
each said sensor member prior to performing said function.
18. A bearing monitoring system as defined in claim 14, wherein two
axles are provided, each said axle including at least two wheel
mounting assemblies surrounding said axle, each said wheel mounting
apparatus including at least one bearing; a wheel mounted on each
said wheel mounting apparatus; a sensor member mounted on each said
axle and associated with each said wheel, each said sensor member
having a first sensing element mounted thereon for use in
determining the acceleration of said wheel by sensing vibrations of
one or more elements of each said wheel mounting apparatus; the
information from each said sensor member being transmitted to said
circuitry, and wherein said circuitry compares the information from
each said sensor member prior to performing said function.
19. A bearing monitoring system as defined in claim 14, wherein
signals accumulated by said first sensing element are processed in
said sensor member.
20. A bearing monitoring system as defined in claim 14, wherein
signals accumulated by said first sensing element are processed by
said circuitry.
21. A bearing monitoring system as defined in claim 14, wherein
said sensor member further includes a second sensing element
mounted thereon for use in determining the speed of rotation of
said wheel; and wherein said circuitry is capable of processing
information from said sensor member regarding the speed of said
wheel.
22. A bearing monitoring system as defined in claim 14, further
including an exciting element mounted on said wheel mounting
apparatus; and wherein said second sensing element determines the
speed of rotation of said wheel by sensing said exciting
element.
23. A bearing monitoring system as defined in claim 14, further
including an element mounted on said wheel mounting apparatus; and
wherein said sensor member further includes a second sensing
element mounted thereon for use in determining the radial and/or
axial proximity of said element relative thereto by sensing the
position of said element; and wherein said circuitry is capable of
processing information from said second sensing element regarding
the radial and/or axial position of said element.
24. A bearing monitoring system for a vehicle comprising: an axle;
a wheel mounting apparatus surrounding said axle, said wheel
mounting apparatus including at least one bearing; a wheel mounted
on said wheel mounting apparatus; an element mounted on said wheel
mounting apparatus; a sensor member mounted on said axle, said
sensor member having a first sensing element mounted thereon for
use in determining the radial and/or axial proximity of said
element relative thereto by sensing the radial and/or axial
position of said element relative to said first sensing element;
and circuitry for processing information from said sensor member
regarding the radial and/or axial proximity of said element and for
performing a function on the vehicle depending on the information
sensed by said first sensing element.
25. A bearing monitoring system as defined in claim 24, wherein
said circuitry is part of an anti-lock brake system or an
electro-pneumatic brake system for the vehicle.
26. A bearing monitoring system as defined in claim 24, wherein
said wheel mounting apparatus includes a hub cap and wherein said
element is an exciting element mounted on said hubcap which
surrounds said sensor member.
27. A bearing monitoring system as defined in claim 24, wherein
said wheel mounting apparatus includes a hub cap and wherein said
element is mounted on said hubcap and extends into said sensor
member.
28. A bearing monitoring system as defined in claim 24, wherein
said axle includes at least two wheel mounting assemblies
surrounding said axle, each said wheel mounting apparatus including
at least one bearing; a wheel mounted on each said wheel mounting
apparatus; a sensor member mounted on each said axle and associated
with each said wheel, each said sensor member having a first
sensing element mounted thereon for use in determining the radial
and/or axial proximity of said element relative thereto by sensing
the position of said element associated with said respective wheel
relative to the respective first sensing element; the information
from each said sensor member being transmitted to said circuitry,
and wherein said circuitry compares the information from each said
sensor member prior to performing said function.
29. A bearing monitoring system as defined in claim 24, wherein two
axles are provided, each said axle including at least two wheel
mounting assemblies surrounding said axle, each said wheel mounting
apparatus including at least one bearing; a wheel mounted on each
said wheel mounting apparatus; a sensor member mounted on each said
axle and associated with each said wheel, each said sensor member
having a first sensing element mounted thereon for use in
determining the radial and/or axial proximity of said element
relative thereto by sensing the position of said element associated
with said respective wheel relative to the respective first sensing
element; the information from each said sensor member being
transmitted to said circuitry, and wherein said circuitry compares
the information from each said sensor member prior to performing
said function.
30. A bearing monitoring system as defined in claim 24, wherein
said sensor member further includes a second sensing element
mounted thereon for use in determining the speed of rotation of
said wheel; and wherein said circuitry is capable of processing
information from said second sensing element regarding the speed of
said wheel.
31. A bearing monitoring system as defined in claim 30, wherein
said element is an exciting element; and wherein said second
sensing element determines the speed of rotation of said wheel by
sensing said exciting element.
32. A bearing monitoring system for monitoring a bearing of a wheel
of a vehicle, said bearing monitoring system comprising: brake
mechanisms; circuitry in operable communication with said brake
mechanisms; wheel speed sensors in communication with said
circuitry, said circuitry configured to operate said brake
mechanisms depending on what is sensed by said wheel speed sensors;
and at least one bearing sensor configured to monitor at least one
characteristic at least generally relating to the bearing, said
characteristic being at least one of a temperature proximate the
bearing, vibrations of one or more elements of said wheel mounting
apparatus and proximity of a rotating element of the wheel.
33. A bearing monitoring system as defined in claim 32, wherein
said circuitry comprises a pneumatic control module in operable
communication with said brake mechanisms and an electronic control
module in communication with said pneumatic control module, said at
least one bearing sensor and said wheel speed sensors in
communication with said electronic control module.
34. A bearing monitoring system as defined in claim 32, further
comprising an electronic circuit assembly, said electronic circuit
assembly including said bearing sensor and at least one of said
wheel speed sensors.
35. A bearing monitoring system as defined in claim 32, wherein
said at least one bearing sensor comprises a plurality of sensors
including a first sensor configured to sense a temperature
generally proximate the bearing, a second sensor configured to
monitor vibrations of one or more elements of said wheel mounting
apparatus, and a third sensor configured to monitor the proximity
of the rotating element of the wheel.
36. A bearing monitoring system as defined in claim 35, further
comprising an electronic circuit assembly, said electronic circuit
assembly including said first, second and third sensor and at least
one of said wheel speed sensors.
37. A bearing monitoring system as defined in claim 32, wherein
said at least one bearing sensor is configured to monitor at least
one of a radial and axial position of the rotating member of the
wheel.
38. A bearing monitoring system as defined in claim 32, wherein
said at least one bearing sensor comprises at least one magnetic
field sensor configured to monitor a magnetic feature relating to
the bearing.
39. A bearing monitoring system as defined in claim 32, wherein
said bearing monitoring system is configured to monitor a plurality
of bearings, and comprises at least one bearing sensor associated
with each bearing, wherein said circuitry is configured to receive
information from each of the bearing sensors and compare the
information.
Description
[0001] This application claims the priority of provisional
application Ser. No. 60/171,741, filed on Dec. 22, 1999, and
entitled "Sensing System For a Trailer Wheel".
BACKGROUND OF THE INVENTION
[0002] This invention is generally directed to a bearing monitoring
system for a vehicle, such as a trailer or a truck. The bearing
monitoring system is provided in combination with a wheel speed
sensor.
[0003] Wheel bearing failure is a serious occurrence for trucks,
trailers and for all wheeled vehicles. A seized bearing can result
in the complete loss of a wheel, including both rims and tires.
After the wheel separates from the vehicle, the potential for
catastrophic damage is present as the wheel may strike other
vehicles or stationery objects. Loss of control of the vehicle
itself may also result.
[0004] On trailers, both oil and grease lubrication systems are
used and correct lubrication plays an important role in continued
safe bearing operation. For both oil and grease, the lubrication
system can fail. For oil, a seal failure can result in significant
oil loss and eventual disruption of the lubricating oil film. For
grease, the bearing may not have been packed properly to begin
with.
[0005] An advantage with grease is that, even after seal failure, a
major leakage still does not occur. In contrast, with oil,
significant leakage occurs. This cause loss of lubricant and the
oil may contaminate other components. Contaminated brake linings in
particular can result in poor and/or unbalanced braking.
[0006] Grease, however, has the disadvantage that the grease cannot
really be inspected without removing the hubcap, and ideally the
entire hub assembly. In contrast, with oil, a sight glass in the
hubcap allows confirmation that oil is present to the correct
level.
[0007] It is desirable to have some means of monitoring the
integrity of the bearing system, especially for grease
applications. This enables the monitoring the presence of lubricant
directly. Alternatively, the monitoring means can monitor bearing
behavior and provide a warning to the operator if the bearings
showed signs of operating without the appropriate lubrication, or
if this is not possible, at least provide prior warning of
impending failure.
[0008] If the bearing is starved of lubrication, rapid wear occurs
which eventually results in bearing failure. Also, bearing
temperatures increase. Characteristic vibrations tend to occur as
oil films break down and metal to metal contact occurs.
[0009] These effects can potentially be used to provide warning
before actual failure.
[0010] In some cases, warning can be provided even before
appreciable wear has occurred. By restoring proper lubrication, the
bearing system can be put back into service without component
replacement. In other cases, however, the warning will be in
advance of actual failure but would still require component
replacement.
[0011] Either is a significant advantage for trucks and trailers.
Avoidance of in service bearing failure, even if component
replacement is required, is a great advantage. Not only is safety
increased but fleets can potentially move to a maintenance
on-demand system. With current practice, wheel hubs and bearings
are normally serviced after a given mileage or service time. Wheel
ends with lubrication and bearings systems intact and capable of
many more miles are dismantled just because of the maintenance
schedule. Extending maintenance intervals results in a direct
economic advantage. Extending maintenance intervals also has
secondary benefits in that for any maintenance operation, there is
always the chance that something gets broken or is reassembled
incorrectly. Quality control of field operations can rarely be as
effective as the quality systems in place at vehicle assembly
plants.
[0012] Providing the monitoring function economically is important
to achieve mainstream acceptance in the trucking industry. Wiring
harnesses which connect to temperature, acceleration and/or
proximity sensors are expensive. Also, electronics to process the
information and provide warning for the driver and/or maintenance
personnel adds additional expense.
[0013] The present invention provides a bearing monitoring system
for a vehicle, such as a trailer or a truck. Features and
advantages of the present invention will become apparent upon a
reading of the specification in combination with a study of the
drawings.
OBJECTS AND SUMMARY OF THE INVENTION
[0014] A general object of the present invention is to provide a
bearing monitoring system for a vehicle, such as a trailer or a
truck.
[0015] An object of the present invention is to provide a bearing
monitoring system for a vehicle, such as a trailer or a truck which
is provided in combination with a wheel speed sensor.
[0016] Briefly, and in accordance with at least one of the
foregoing objects, an embodiment of the present invention provides
a bearing monitoring system for monitoring a bearing of a wheel of
a vehicle, such as a truck or a trailer. The bearing monitoring
system is configured to monitor at least one characteristic
relating to the wheel bearings, such as a temperature generally
proximate the bearings, vibrations of one or more elements of the
wheel mounting apparatus, and/or the proximity of a rotating
element of the wheel. The monitoring system may be configured to
monitor more than one of these characteristics (i.e., temperature,
vibration and proximity) or even all three. The bearing monitoring
system is incorporated into a wheel speed sensor. The bearing
monitoring system may be incorporated in an anti-lock brake system
(ABS) or electro-pneumatic brake system (EBS). Regardless of which
characteristic is actually monitored by the system and whether the
system is employed with an ABS or EBS, the bearing monitoring
system provides that one or more bearings of a vehicle can be
continuously and automatically monitored in the field.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The organization and manner of the structure and operation
of the invention, together with further objects and advantages
thereof, may best be understood by reference to the following
description, taken in connection with the accompanying drawings,
wherein like reference numerals identify like elements in
which:
[0018] FIG. 1 is a block diagram of a prior art anti-lock brake
system;
[0019] FIG. 2 is a side elevational view of a trailer and a partial
side elevational view of a tractor on which the ABS or EBS which
incorporates the features of the present invention is used;
[0020] FIG. 3 is a block diagram of an anti-lock brake system (ABS)
or an electro-pneumatic brake system (EBS) which incorporates the
features of the present invention;
[0021] FIG. 4 is a partial cross-sectional view of a wheel mounting
apparatus which includes a wheel speed sensor which incorporates
the features of the invention;
[0022] FIG. 5 is an enlarged section of FIG. 4;
[0023] FIG. 6 is a perspective view of a portion of the wheel speed
sensor;
[0024] FIG. 7 is an enhancement circuit which is used in the
present invention;
[0025] FIG. 8 is a partial cross-sectional view of an alternate
wheel mounting apparatus which includes a wheel speed sensor which
incorporates the features of the invention;
[0026] FIG. 9 is an electronic schematic of an implementation of
the present invention; and
[0027] FIG. 10 is a schematic of the wheel speed sensor and
ABS.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT
[0028] While the invention may be susceptible to embodiment in
different forms, there is shown in the drawings, and herein will be
described in detail, a specific embodiment with the understanding
that the present disclosure is to be considered an exemplification
of the principles of the invention, and is not intended to limit
the invention to that as illustrated and described herein.
[0029] The present invention provides a bearing monitoring system
for monitoring the health of a bearing 34, 36 of a wheel of a
vehicle 26, such as a truck or a trailer. The bearing monitoring
system is configured to monitor at least one characteristic related
to the bearings 34, 36, such as a temperature generally proximate
the bearings 34, 36, vibrations of one or more elements of the
wheel mounting apparatus 24, and/or the proximity of a rotating
element of the wheel. The monitoring system may be configured to
monitor more than one of these characteristics (i.e., temperature,
vibration and proximity) or even all three. The bearing monitoring
system may be incorporated in an anti-lock brake system (ABS) or
electro-pneumatic brake system (EBS). Regardless of which
characteristic is actually monitored by the bearing monitoring
system and whether the bearing monitoring system is employed with
an ABS or EBS, the bearing monitoring system provides that one or
more bearings 34, 36 of the vehicle 26 can be continuously and
automatically monitored in the field. The bearing monitoring system
of the present invention is provided in a wheel speed sensor
20.
[0030] The specifics of the physical parameters of the sensor 20 is
described in copending patent application Serial No. (Not Yet
Assigned), filed on Dec. 21, 2000, entitled "Axle End Wheel Sensor
For A Truck Or A Trailer". The specifics of the wheel speed and
direction sensing by the sensor 20 is described in co-pending
patent application Ser. No. (Not Yet Assigned), filed on Dec. 21,
2000, entitled "Anti-Lock Brake System For A Truck Or A Trailer,
Including Back-up Alarm And/or Lamps". Each of these patent
applications claim the priority of provisional application Ser. No.
60/171,741 upon which the present application claims priority. Each
disclosure of these patent applications are commonly owned by the
assignee herein and are incorporated herein in their entirety. The
sensor 20 is provided in an apparatus 24 for mounting a wheel on
the trailer 26.
[0031] A block diagram an anti-lock brake system (ABS) or an
electro-pneumatic brake system (EBS) for a trailer 26 in accordance
with the present invention is shown in FIG. 3. The present
invention provides a wheel sensing arrangement which provides
information to a controller, such as an electronic control module
(ECM). Power (12 Volts) to the ECM is supplied from pin 7 of the
J560 connector 18 between the tractor 16 and the trailer 26. The
ECM controls a pneumatic control module (PCM) which controls the
brake mechanism on the trailer 26. The ECM also controls the
function of a system, such as a warning system in the cab of the
tractor 16 which is used to alert the operator, as described
herein. The ECM of the ABS or EBS signals the PCM of the ABS or EBS
to modify air pressure level at the brake chambers. The braking
level is controlled so that the wheels continue to rotate, or at
least rotate most of the time, even during heavy braking. The
overall process is described in detail in numerous patents and in
the pending U.S. patent application Ser. No. 09/306,921, which is
commonly owned by the assignee herein and which is incorporated by
reference.
[0032] The wheel mounting apparatus 24 generally includes the axle
22, a wheel hub assembly 28 and a brake mechanism. The brake
mechanism is of known construction and as such is not described in
detail herein.
[0033] The axle 22 is fixedly mounted on the body of the trailer 26
by suitable means and is formed from a hollow tube (only one end of
which is shown in FIG. 4). The ends of the hollow axle 22 have a
thread form on the exterior surface thereof. The inner surface of
each end of the axle 22 has a portion 30 which has an increased
inner diameter relative to an inner diameter of a central portion
of the axle 22. The axle 22 is formed from a suitable strong rigid
material.
[0034] The wheel hub assembly 28 is mounted on the end of the axle
22 and generally surrounds the axle 22. The wheel hub assembly 28
includes a wheel hub 32, a plurality of inner bearings 34, a
plurality of outer bearings 36, and a metal hub cap 38. The wheel
hub 32 is attached to the brake drum by suitable known means, such
as bolts.
[0035] The inner and outer bearings 34, 36 are mounted between the
wheel hub 32 and the axle 22 by respective bearing cups 40 and
bearing cones 42 and allow for rotation between the fixed axle 22
and the rotating wheel hub assembly 28 and the brake mechanism. The
outer bearings 36 are mounted in the portion 33 such that the
bearing cups 40 abut against a shoulder formed by the portion 33.
This precisely mounts the outer bearings 36 on the axle 22. The
inner and outer bearings 34, 36 are mounted at locations which are
spaced apart from each other along the length of the axle 22 such
that a cavity 44 is provided between the wheel hub 32, the axle 22
and the bearings 34, 36. A bath of oil or semi-fluid synthetic
grease is contained within the cavity 44. The bearings 34, 36 are
lubricated by the bath of oil or semi-fluid synthetic grease
contained therewithin.
[0036] The hub cap 38 surrounds the end of the axle 22 and prevents
the oil or grease from leaking out of the end of the wheel hub
assembly 28. The hub cap 38 includes a circular outer end wall 46,
a first side wall 48, a second side wall 50, a third side wall 52
and an inner end wall 54. The walls 46, 48, 50, 52, 54 are
integrally formed with each other. The first side wall 48 is
generally perpendicular to the outer end wall 46 and has a first
end connected to the outer end wall 46 and tapers from its first
end to its second, larger end. The second side wall 50 has a first
end connected to the second end of the first side wall 48 and
tapers from its first end to its second, larger end. The third side
wall 52 has a first end connected to the second end of the second
side wall 50 and tapers from its first end to its second, larger
end. The inner end wall 54 is annular and is generally
perpendicular to the third side wall 52 and has a first end
connected thereto and extends outwardly therefrom. The inner end
wall 54 is parallel to the outer end wall 46. A plurality of
apertures are provided through the inner end wall 54 through which
the hub cap 38 is attached to the end of the wheel hub 32 by
suitable means, such as bolts 56.
[0037] The third side wall 52 has an end portion 55 which extends
past the inner end wall 54. When the hub cap 38 is mounted on the
wheel hub 32, the end portion 55 seats within the portion 33 of the
wheel hub 32 and abuts against the cones 40 of the outer bearings
36. This locates the hub cap 38 precisely on the wheel hub 32 and
on the axle 22.
[0038] A washer 58 is mounted on the threaded end of the axle 22
and bears against the bearing cones 42 of the outer bearings 36. An
inner adjusting nut is 60 threaded onto the threaded end of the
axle 22 and bears against the washer 58. The adjusting nut 60 is
locked onto the axle 22 by threading an outer jam nut 62 on the
threaded end of the axle 22. The adjusting nut 60 is used to
properly position the outer bearings 36. The washer 58, the inner
adjusting nut 60 and the outer jam nut 62 are proximate to the
third side wall 52 of the hub cap 38. The washer 58, the inner
adjusting nut 60 and the outer jam nut 62 do not completely fill
the space between the axle 22 and the hub cap 38 such that a space
is formed therebetween. It is to be understood that other
components can be threaded on the end of the axle 22 to properly
position the outer bearings 36.
[0039] A freeze plug 64 sits within and fills the end portion 30 of
the axle 22. The freeze plug 64 has a circular central portion 66
and an annular skirt 68 which depends therefrom. The skirt 68
tightly engages with the inner surface of the end portion 30 of the
axle 22. A central aperture 70 and a second aperture (not shown)
therethrough which is offset from the central aperture 70 are
provided through the central portion 66 of the freeze plug 64. A
grommet (not shown) is provided within the second aperture. The
freeze plug 64 prevents oil or grease from entering into the axle
22 and prevents debris from going from within the axle 22 outwardly
therefrom.
[0040] The sensor 20 includes a sensor member 72 which is mounted
in the end of the axle 22 and is spaced from the freeze plug 64.
The sensor member 72 includes a plastic body 76 which extends
partially into the end of the axle 22 and extends outwardly
therefrom, and a plastic cover 78 which covers the section of the
body 76 which extends outwardly from the end of the axle 22. The
cover 78 is suitably secured to the body 76. A recess is formed
between the body 76 and the cover 78. A central aperture 80 is
provided through the body 76 and the cover 78 and aligns with the
central aperture 70 through the freeze plug 64. A plurality of
L-shaped vents 81 are provided through the periphery of body 76 to
provide an air passageway from the space between the freeze plug 64
and the body 76 and the space between the sensor member 72 and the
hub cap 38.
[0041] The body 76 of the sensor member 72 is fastened to the axle
22 by a bolt 82 which is mounted in the central aperture 80 through
the body 76. The bolt 82 threads with the central aperture 70
through the freeze plug 64. The thread form in the freeze plug 64
may be pre-tapped or may be generated using a thread forming
bolt.
[0042] The central aperture 80 in the body 76 allows for the
possibility of an air passage through the body 76 if a hollow bolt
82 is utilized as shown. This allows for the incorporation of a
central tire inflation (CTI) in the present system. CTI systems
automatically keep tires inflated by passing air from a compressed
air reservoir mounted on the trailer 26 to the tires. One possible
implementation of a CTI system with the present invention passes
air through a tube in the hollow axle 22, then through a swivel
connection with a rotating seal to air fittings on the outside of
the hub cap 38. The air is then piped to the inflation valves for
the tires. A suitably designed hollow bolt 82 allows for the air to
pass from the tube in the hollow axle 22 to the rotating seal in
the hub cap 38. The sensor member 72 of the present invention
allows for CTI but does not economically penalize the majority of
applications where CTI is not used.
[0043] To protect the bearings 36, 38, the entire axle end area is
sealed from moisture, dirt and other contaminants. Suitable venting
is provided so that the seals within the wheel mounting apparatus
24 are not subjected to excessive pressure buildup. Depending on
the wheel end construction, different methodologies may be used
which use suitable vents in the hub cap 38, seals and/or the freeze
plug 64. The sensor member 72 of the present invention is
compatible with all such approaches. Consequently, the periphery of
the body includes the L-shaped venting slots 81 such that pressure
on both the front and back of the sensor member 72 remains
equalized. As for a conventional wheel end construction, venting
and sealing are controlled by the hub cap, freeze plug and bearing
seals. It should be noted that, depending on the application and
the method of lubrication of the bearings, all parts of the sensor
member 72 may be subject to oil splash. The design and material of
the sensor member 72 of the present invention allows for operation
in this environment.
[0044] An electronic circuit assembly 84 is provided between the
body 76 and the cover 78 of the sensor member 72. The electronic
circuit assembly 84 includes a printed circuit board 86 mounted on
the body 76 by suitable means such that the printed circuit board
86 is positioned between the body 76 and the cover 78 of the sensor
member 72. Wires 90 extend from the printed circuit board 86
through the grommet in the freeze plug 64, through the hollow axle
22 to a current supplying controller 92. The controller 92 is
preferably the ECM of the ABS or EBS of the trailer 26. If desired,
a second controller can be provided.
[0045] Wheel speed sensing elements 94, 96 are provided on the
printed circuit board 86 in the form of an application specific
integrated circuit (ASIC) 88. The preferred embodiment of the
present invention uses "active" technology.
[0046] The wheel speed sensing elements 94, 96 are preferably a
pair of hall effect semiconductor elements. The hall effect
semiconductor elements 94, 96 can be soldered to the printed
circuit board 86 at the outermost end thereof and at spaced
locations from each other. Preferably, however, the hall effect
semiconductor elements 94, 96 are located on the same silicon chip.
This aids in overall economy and, because of the use of standard
integrated circuit fabrication techniques, relative location can be
controlled. The face of each hall effect semiconductor sensing
element 94, 96 is parallel to the axis of rotation of the axle 22.
It is to be understood that conventional VR sensors can be used
instead of hall effect semiconductor sensing elements 94, 96.
[0047] The second side wall 50 of the hub cap 38 is machined to
provide a recess in which a mounting wheel 75 is located. To secure
the mounting wheel 75 to the inside of the second side wall 50, the
metal second side wall 50 is deformed. This precisely locates the
mounting wheel 75 on the hub cap 38. Because the hub cap 38 is
precisely mounted on the wheel hub 32 and axle 22 as discussed
herein, the mounting wheel 75 is precisely mounted on the wheel hub
32 and axle 22.
[0048] An exciting ring 74 is mounted on the inner surface of the
mounting wheel 75 and is proximate to, but spaced from the hall
effect semiconductor sensing elements 94, 96. Because the mounting
wheel 75 is precisely mounted on the wheel hub 32 and axle 22, the
exciting ring 74 is precisely mounted on the wheel hub 32 and axle
22. The exciting ring 74 and the sensor member 20 are concentric
with each other when mounted. As such, a defined radial gap is
provided between the exciting ring 74 and the hall effect
semiconductor sensing elements 94, 96. The hall effect
semiconductor sensing elements 94, 96 are mounted on the printed
circuit board 86 so as to precisely line up with the exciting ring
74 when the hub cap 38 is mounted on the wheel hub 32.
[0049] Because the face of each hall effect semiconductor sensing
element 94, 96 is parallel to the axis of rotation of the axle 22,
a constant gap is maintained by the bearings 36. Axial movement of
the wheel hub 32 does not have a significant effect and no gap
adjustment is required. The gap is set by design, and gap variation
is directly controlled by the bearings 36. The gap is dependent on
the concentricity of the mounting of the exciting ring 74 within
the hub cap 38.
[0050] In the preferred implementation, the exciting ring 74 is a
multi-pole magnet fabricated using ferrite in a plastic matrix
material. Because the exciting ring 74 is carried on the mounting
wheel 75 mounted inside the hub cap 38, the magnet poles can be
located precisely both circumferentially around the sensor member
72 and radially relative to the sensor member 72. The gap between
the exciting ring 74 and the hall effect semiconductor sensing
elements 94, 96 is radial so that the gap is directly controlled by
the position of the bearings 36 and is not influenced by axial
movement of the wheel hub 32. Alternatively, a stamped, toothed
ring can be used as the exciting ring 74.
[0051] The hall effect semiconductor sensing elements 94, 96 are
spaced apart from each by an integral number of pole pairs or
teeth, depending on the type of exciting ring 74 that is used, plus
or minus approximately ninety degrees.
[0052] To allow for overall optimization of the sensor member 72
and for ABS function or EBS function, when the present invention is
used in an ABS or EBS as described herein, the preferred embodiment
of the exciting ring 74 does not conform to the present industry
standard of one hundred teeth. Instead, the present invention uses
twenty-five pole pairs in the exciting ring 74. These pole pairs
are precisely located so that with use of suitable electronic
resolution enhancement techniques, an information rate equivalent
to fifty pole pairs using standard techniques is achieved.
[0053] FIG. 7 illustrates a circuit which implements this
resolution enhancement technique. Signals A and B originate from
the hall effect semiconductor sensing elements 94, 96. Signals A
and B are input into an XOR gate 99. The resulting waveform is
generated as output C. Other suitable circuits can be used.
[0054] Individual active sensing elements are the preferred sensing
elements for the sensing elements 94, 96 of the present invention.
The chips which implement the Hall effect function are small.
Relative location can be tightly controlled by mounting on the same
printed circuit board. The two hall effect semiconductor elements
94, 96 can be located on the same silicon chip. This aides overall
economy and, because of the use of standard integrated circuit
fabrication techniques, relative location becomes almost a
non-issue. Two integrated circuits can be provided on the silicon
chip, each having a hall effect element thereon.
[0055] A temperature sensing element 100 is provided on the printed
circuit board 86 and may be in the form of an application specific
integrated circuit (ASIC) 102. Numerous implementations of the
temperature sensing element 100 are possible as would be understood
by one of ordinary skill in the art. The temperature sensing
element 100 is used to monitor the temperature of the bearings 34,
36 in the wheel mounting apparatus 24 by measuring the temperature
of the components of the wheel mounting apparatus 24. The
temperature of the bearings 34, 36 will increase under operating
conditions if the bearings 34, 36 are insufficiently lubricated
which occurs when insufficient oil or grease is present in the
chamber 44. The provision of the temperature sensing element 100 in
the electronic circuit assembly 84 is ideal for monitoring the
bearings 34, 36 as the printed circuit board 86 is in close
proximity to the bearings 34, 36.
[0056] The details of an implementation of the sensor electronics
which are used to determine speed, direction and temperature is
shown in FIG. 9. One of ordinary skill in the art could form other
suitable implementations. The circuit as shown in FIG. 9 includes
an integrated circuit 104, integrated circuit 106, resistors 108,
110, 112, and capacitors 114, 116, 118, 120.
[0057] A suitable integrated circuit 104 is an Allegro A3422LKA
integrated circuit. The two hall effect semiconductor elements 94,
96 are embedded on one piece of silicon in the integrated circuit
104 such that the two hall effect semiconductor elements 94, 96 are
spaced a suitable distance for quadrature implementation. The Vcc
pin 1 of integrated circuit 104 is a voltage input. The DIR pin 2
of integrated circuit 104 outputs direction information using
high/low logic. The GND pin 3 of integrated circuit 104 is
connected to ground. The SPD pin 5 of integrated circuit 104
outputs a frequency signal proportional to wheel speed. The SPD pin
5 of integrated circuit 104 implements the resolution enhancement
functionality shown in FIG. 7. Resistor 110 is connected to pin 5.
The EI pin 4 of integrated circuit 104 is connected to ground by
resistor 108.
[0058] Integrated circuit 106 senses the temperature of the
components of the wheel mounting apparatus 24 and provides a
current output which varies with temperature. A suitable integrated
circuit 106 is an AD TMP17 integrated circuit.
[0059] In operation, to determine the speed and direction of
rotation of the wheels, the wheel hub 32, the hub cap 38, the
mounting wheel 75 and the exciting ring 74 rotate relative to the
fixed axle 22 and the sensor member 72 mounted thereon. The
controller 92 supplies electric current to the sensor member 72
through connection J1-1. The sensor member 72 is a current sink.
The hall effect semiconductor sensing elements 94, 96 sense whether
a north pole or a south pole of the exciting ring 74 is
present.
[0060] If a multi-pole magnet is used as the exciting ring 74, if a
north pole is present, the hall effect semiconductor sensing
elements 94, 96 sink 14 mamps, for example, from the controller 92,
and if a south pole is present, the hall effect semiconductor
sensing elements 94, 96 sink 7 mamps, for example, from the
controller 92. This information is conveyed to another part of the
ASIC 88, to obtain a square wave as the poles are going by. The
controller 92 determines how many times the sensor member 72
switches between 14 mamps and 7 mamps. This change happens one
hundred times every revolution of the wheel. If a toothed wheel is
used as the exciting ring 74 and a tooth is present, the hall
effect semiconductor sensing elements 94, 96 sink 14 mamps, for
example, from the controller 92. On the other hand, if a space is
present, the hall effect semiconductor sensing elements 94, 96 sink
7 mamps, for example, from the controller 92. This information is
conveyed to another part of the ASIC 88, to obtain a square wave as
the poles are going by. The controller 92 determines how many times
the sensor member 72 switches between 14 mamps and 7 mamps. This
change happens one hundred times every revolution of the tire. It
is to be understood that the 14 mamps and 7 mamps values described
herein are nominal. These values could be other nominal values,
such as 12 mamps and 6 mamps, or 10 mamps and 5 mamps.
[0061] The frequency of the change is proportional to the wheel
speed. This information is used by the ABS or EBS to function in a
like manner to how a conventional wheel speed sensor information is
used to slow the trailer 26, if necessary.
[0062] The frequency output on the SPD pin 5 of integrated circuit
104 is implemented using high/low voltage levels. As implemented in
the circuit shown in FIG. 9, this voltage signal is converted into
a two level current signal by the presence of resistor 110. SPD pin
5 pulls current through resistor 110 when SPD pin 5 is low. When
SPD pin 5 is high, current is not pulled through resistor 110. The
interface electronics then senses the current variation. This keeps
the overall wiring interface to three leads, power, ground and
direction. Current pulses in the power lead correspond to the
passage of poles as the exciting ring 74 rotates or to the passage
of teeth if a toothed ring is used. The E1 signal output on pin 4
from the integrated circuit 104 is not required in this application
and is held at ground by resistor 108. The capacitors 114, 116
provide noise suppression.
[0063] The integrated circuit 104 does not output a current, such
that a low is provided, on DIR pin 2 when the trailer 26 is backing
up. The controller 92, which is the ECM of the ABS or EBS, detects
that the integrated circuit 104 is not outputting current and
determines that the trailer 26 is backing up. Because the forward
and reverse wheel speed information is available to the controller
92, the information can be used to provide enhanced functionality
over and above that of ABS or EBS without the forward and reverse
wheel speed information.
[0064] Current is supplied from the ECM through connection J1-1,
flows through integrated circuit 106 and then out to the ECM
through connection J1-3. The ECM completes the current path to
ground and monitors this current.
[0065] The signal is shared with the reverse indication. When
reverse rotation occurs, the DIR output of integrated circuit 104
is pulled low so the current from integrated circuit 104 flows to
ground through resistor 112. The current flow to the ECM (via J1-3)
goes to near zero. This is interpreted by the ECM as an indication
that the trailer 26 is backing up and that the temperature
indication is not available. Because the temperature information
and the direction information are output on the same pin (i.e.
J1-3), the ECM determines what sensor, whether from the
semi-conductor sensing elements 94, 96 or the temperature sensing
element 100, the signal is being sent from. Utilization of
connection J1-3 for both functions is important because extra
wiring and connections are very expensive. The entire sensing
system, including wheel speed sensing, direction sensing and
temperature sensing is implemented with only three wires (i.e.
J1-1, J1-2 and J1-3), thereby generating significant cost savings.
Also, by incorporating the signal processing and warning
electronics into the ECM of the ABS, further savings are achieved
in overall system cost.
[0066] If the bearings 34, 36 heat up to a predetermined amount,
the ECM determines that there is a bearing problem by comparing the
signals received from the temperature sensing element 100 to a
known value, and activates the circuitry to alert the operator that
the bearings 34, 36 need to be serviced. The circuitry can light a
warning light on the trailer 26, a warning light in the cab of the
tractor 16 and/or can send the information to a trailer tracking
system.
[0067] While the practical implementation of this sensor 20 is with
the ABS, the sensor 20 can be used without ABS and with a current
supplying controller. As noted earlier many tractors have power
available on Pin 7 of the auxiliary connector. In all cases, on new
trailers, Pin 7 is connected to the ECM of the ABS or EBS. It
should also be noted that this power supply, under current mandated
requirements, is not required to be dedicated solely to the ABS
function or EBS function.
[0068] An acceleration sensing element 122, such as an
accelerometer, is also provided on the printed circuit board 86 and
may form part of the ASIC 102 or may be a separate integrated
circuit sensing element on the printed circuit board 86. Other
suitable implementations of the acceleration sensing element 122
can be implemented by one of ordinary skill in the art. The
acceleration sensing element 122 senses vibrations of one or more
elements of the wheel mounting apparatus 24 and transmits this
information to the controller 92. The acceleration sensing element
122 may be a silicon micromachined integrated circuit. Because the
printed circuit board 86 is mounted to the body 76 of the sensor 20
and the sensor 20 is mounted to the end of the axle 22, vibrations
of one or more elements of the wheel mounting apparatus 24 with
some attenuation, are transmitted to the acceleration sensing
element 122. The provision of the acceleration sensing element 122
in the electronic circuit assembly 84 is ideal for monitoring the
bearings 34, 36 as the printed circuit board 86 is in close
proximity to the bearings 34, 36.
[0069] As lubrication fails or partially fails and some direct
metal to metal contact occurs between the bearing 34, 36 and the
cups 40 and/or cones 42, some characteristic vibrations occur. The
acceleration sensing element 122 detects these vibrations. The raw
signal is sent to the ECM and the ECM processes the raw signal and
extracts frequency information. The ECM compares this frequency to
known frequencies to determine whether this is an incorrect signal.
If an incorrect signal is determined by the ECM, the ECM determines
that there is a bearing problem and activates the circuitry to
alert the operator that the bearings 34, 36 need to be serviced.
The circuitry can light a warning light on the trailer 26, a
warning light in the cab of the tractor 16 and/or can send the
information to a trailer tracking system. Alternatively, the
acceleration signals from the acceleration sensing element 122 can
be processed locally in the printed circuit board 86. The ECM of
the ABS is preferably used to process the raw signal, because the
ECM is comprised of relatively inexpensive electronic hardware, and
because the ECM also allows comparison of signals from two or all
wheels on the trailer 26 as discussed herein.
[0070] Metal proximity sensing elements 124, 126, see FIG. 10, are
provided on the printed circuit board 86 and may form part of the
ASIC 102. Proximity sensing element 124 senses radial proximity of
the wheel mounting apparatus 24 and proximity sensing element 126
senses axial proximity of the wheel mounting apparatus 24. The
proximity sensors 124, 126 measure the instantaneous location of
the hub cap 38 relative to the axle 22 and, as such, can be used to
determine disturbances in the circular trajectory of the rotating
components of the wheel mounting apparatus 24. These disturbances
may result from poor or loose adjustment of the bearings 34, 36 or
the onset of wear in the bearings 34, 36. It should also be noted
that axial free play results from bearing 34, 36 adjustment which
is too loose and which eventually would result in premature wear of
the bearings 34, 36. If there are issues with bearing wear, the
wheel hub 32 will not move in a circular movement.
[0071] If the bearings 34, 36 are loose, axial movement of the
wheel hub 32 occurs. It is to be understood that either of, or both
of, the radial proximity sensing element 124 and the axial
proximity sensing element 126 may be incorporated to help determine
bearing system integrity. Because the body 76 and the cover 78 of
the sensor 20 are constructed of a plastic material, the body 76
and the cover 78 do not have an effect on the metal sensing
proximity sensing elements 124, 126. The provision of the proximity
sensing elements 124, 126 in the electronic circuit assembly 84 is
ideal for monitoring the bearings 34, 36 as the printed circuit
board 86 is in close proximity to the bearings 34, 36.
[0072] An inwardly protruding metal extension 128 which is mounted
on the end wall 46 of the hub cap 38 and extends inwardly along the
axis of rotation of the axle 22.
[0073] The extension 128 has a first portion 130 which is mounted
to the end wall 46 and a second portion 132 which extends
therefrom. The first portion 130 has a larger diameter than the
second portion 132. The second portion 132 of the extension 128
extends into the hollow center of the sensor member 20 and is
monitored by the radial proximity sensing element 124 and/or an
axial proximity sensing element 126. The radial proximity sensing
element 124 and/or the axial proximity sensing element 126 may be a
suitable eddy current or other proximity sensing element along with
the electronic circuit assembly 84. Alternatively, the extension
128 may be mounted in the body 76 of the sensor member 20 and be
wired to the electronic circuit assembly 86.
[0074] The radial sensing element 124 senses the position of the
metal second portion 132 of the extension 128 in that it senses the
distance between the second portion 132 and the radial sensing
element 124. Therefore, the distance between the entire rotating
portion of the wheel mounting apparatus 24 relative to the axle 22
is sensed. The radial sensing element 124 sends this information to
the ECM. The ECM processes this information. If the ECM detects
some change in distance, the ECM activates the circuitry to provide
the warning that the bearings 34, 36 need to be serviced. The
circuitry can light a warning light on the trailer 26, a warning
light in the cab of the tractor 16 and/or can send the information
to a trailer tracking system.
[0075] The axial sensing element 126 senses the position of the
metal first portion 130 of the extension 128 in that it senses the
distance between the first portion 130 and the axial sensing
element 126. Therefore, the distance between the entire rotating
portion of the wheel mounting apparatus 24 relative to the axle 22
is sensed. The axial sensing element 126 sends this information to
the ECM. The ECM processes this information. If the ECM detects
some change in distance, for example 12 thousandths, the ECM
activates the circuitry to provide the warning that the bearings
34, 36 need to be serviced. The circuitry can light a warning light
on the trailer 26, a warning light in the cab of the tractor 16
and/or can send the information to a trailer tracking system.
[0076] The signals from the proximity sensing elements 124, 126 can
processed locally in the printed circuit board 86 or can be fed
back as a raw signal to the ECM. The ECM of the ABS is preferably
used to process the raw signal, because the ECM is comprised of
relatively inexpensive electronic hardware, and because the ECM
also allows comparison of signals from all wheels on the vehicle as
discussed herein.
[0077] Preferably, a sensor member 20 is provided on each wheel of
the vehicle 26. The ECM compares the two (single axle vehicle) or
four (double axle vehicle) temperature, acceleration and/or
proximity signals from all wheels on the vehicle 26 and compares
the signals with each other in the ECM as part of an abnormality
detection routine carried out in the ECM. This is particularly
important with regard to temperature. The ambient temperature
widely varies with the operating environment of the vehicle 26. By
comparing the temperature signals from each wheel, the variation
due to ambient temperature can be ignored. Temperature deviations
due to bearing abnormalities can then be isolated. This approach
can also be important for acceleration or proximity sensing. For
example, on a very smooth road surface, it is possible to be more
sensitive in detection of bearing health. In contrast, on a rough
road surface, it is necessary for the system to be more tolerant of
the severe vibrations generated by the travel over the rough road
to avoid false warning signals. By comparing signals from all
wheels of the vehicle 26, the prevailing normal condition can be
determined, and therefore abnormal deviations can be detected.
[0078] The sensor member 20 utilizes some or all of the wiring to
the ABS. As shown in FIG. 9, the temperature sensing element 100
shares the same signal wire which also provides the direction
signal from the speed sensing elements 92, 94. It is to be noted
that temperature sensing is not active when the trailer 26 is in
reverse.
[0079] The temperature sensing element 100 and the acceleration
sensing element 122 can share the same signal wire (and may also
share the signal wire with the direction sensing elements 92, 94).
Signals from the acceleration sensing element 122 are AC signals,
while signals from the temperature sensing element 100 are slowly
varying DC signals. Thus, the acceleration and temperature signals
can share the same wire and can be separated in the ECM.
[0080] The direction sensing elements 92, 94, the temperature
sensing element 100, the acceleration sensing element 122 and the
proximity sensing elements 124, 126 can also share the same signal
wire. This is dependent on the frequency ranges of the signals
which are usable by the ECM. It is possible to time multiplex these
signals so that they are examined in rotation by the ECM.
[0081] Another implementation (not shown) of this aspect of the
present invention can utilize magnetic field sensors in the
electronic circuit assembly 84 to track the location of the
existing exciting ring 74. A further implementation provides an
additional magnet (not shown) located on the mounting wheel 76.
[0082] While a preferred embodiment of the present invention is
shown and described, it is envisioned that those skilled in the art
may devise various modifications of the present invention without
departing from the spirit and scope of the appended claims.
* * * * *