Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
BRAKE WEAR MANAGING SYSTEM
FIELD OF THE INVENTION
The present invention relates to systems for managing
brake wear on a vehicle provided with brake assemblies.
BACKGROUND OF THE INVENTION
Brake wear managing systems are particularly
advantageous when provided in heavy vehicles since the weight of such
vehicles makes braking more difficult and potential loss of control more
hazardous than in the case of lighter vehicles, such as for example,
automobiles. Routine inspections of heavy vehicles must therefore be
done more often to ensure the safety of the driver and of the public. The
conventional way to perform the inspection is to visually inspect the brake
assemblies.
Routine inspections are however costly since, a) the
vehicle must be kept off the road during the inspection, b) a mechanic is
required, and c) the wear on one or more brake assemblies can already
be too important, resulting in premature wear of the other brake
assemblies.
A solution has been proposed by Thorn in United States
Patent No. 4,729,214 issued on July 21, 1981 and entitled "Brake Wear
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Indicator". Thorn describes a brake wear indicator comprising a sleeve
that loosely fits over the push rod of the pneumatic actuator of a truck
drum brake assembly. Indicia are calibrated on the exterior surface of the
sleeve whereby the inspector can directly observe the degree of sleeve
travel that corresponds to the push rod travel in the brake assembly.
Thorn's system has many drawbacks. For example, the
person doing the inspection must know when the push rod travel is
unacceptable. This can be seen as a drawback since this visual
inspection is based on subjective criteria. Furthermore, the indication is
difficult to access and cannot be operated while the truck is running.
Finally, since the inspection is based on subjective criteria, it can be
difficult to foresee as to when brake adjustments will be necessary, as well
as to perform diagnostics.
Solutions to some of these drawbacks have been
proposed by Larson et al. in United States Patent No. 5,253,735 issued
on October 19, 1993 and entitled "Apparatus to Sense and Annunciate
Truck Brake Condition". Larson et al.'s apparatus includes two Hall effect
switches that sense the rotation of disks mounted to the S-cam shaft of
the braking system. Sensor data are transmitted to an annunciator
mounted at a distance from the brake assembly. Separate sensing and
annunciating systems are provided for each wheel of the truck.
While some drawbacks of Thorn's system have been
overcome by Larson et al., their apparatus does not allow making any
forecast as to when brake adjustments will be necessary. Furthermore,
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Larson et al.'s system does not directly monitor the push rod. The
measure is taken further from the actuating linkage. That can produce
less reliable measurements.
5 Other problems with brake monitoring systems of the
prior-art include the difficulty to manage brake changes for fleets of
vehicles since they do not allow remote monitoring of vehicles and the fact
they don't provide any visual tool to assess the operating performance of
their sensors to help identify problems of the brake assemblies.
OBJECT OF THE INVENTION
An object of the present invention is therefore to provide
a brake wear managing system free of the above-mentioned drawbacks
of the prior-art.
SUMMARY OF THE INVENTION
More specifically, in accordance with the present
20 invention, there is provided a brake wear managing system for a vehicle
provided with at least one brake assembly, the brake wear managing
system comprising:
at least one sensor assembly including a sensor and a
mounting assembly to secure the sensor to one of at least one brake
25 assembly; each sensor being so configured as to generate a signal
responsive to brake wear; and
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an on-board controller coupled to each sensor; the on-
board controller being configured to receive said signal from each sensor
and to generate brake wear condition signals accordingly.
According to a preferred embodiment of the present
invention, the brake wear managing system further comprises a remote
controller coupled to the on-board controller and being configured to
receive at least one of a) the sensor signals and b) the break wear
condition signals. The remote controller is so configured as to generate
break wear history database.
Other objects, advantages and features of the present
invention will become more apparent upon reading of the following non-
restrictive description of preferred embodiments thereof, given by way of
example only with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the appended drawings:
20 Figure 1 is a schematic top plan view of a brake
monitoring system according to a first embodiment of the present
invention, as mounted on a trailer truck;
Figure 2 is a perspective partially sectional view of a
brake assembly onto which a brake monitoring system according to a first
embodiment of the present invention is to be mounted;
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Figure 3 is a schematic side elevational view illustrating
the operation of the brake assembly of Figure 2;
5 Figure 4 is a sectional side elevational view of the air
drums of the brake assembly of Figure 2;
Figure 5 is a perspective view of a sensor assembly of
the brake monitoring system of Figure 2; and
Figure 6 is a schematic top plan view of a brake
monitoring system according to a second embodiment of the present
invention, as mounted on a trailer truck
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to Figure 1 of the appended drawings, a brake
wear managing system 10 according to a first embodiment of the present
invention will be described.
The brake wear managing system 10 comprises a
plurality of sensor assemblies 12A-12H, an on-board controller 14 and a
remote controller 16.
In order to better describe the sensor assemblies 12A-
12B, the configuration and the principle of operation of a brake assembly
18 onto which each of the sensor assemblies 12A-12B is to be mounted
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will first be described by referring to Figure 2 to Figure 5 of the appended
drawings.
As commonly known by a person well versed in the art,
5 the brake assembly 18 is mounted to one of the axles 22 of a truck 24 (in
dashed line on Figure 1 ). A wheel (not shown) is mounted to the axle 22
via a drum brake 28, fixedly mounted to a disk 26 via bolts (not shown) or
other securing elements.
10 The brake action is actuated by the rotation of an S-cam
expander 30 that pushes a pair of brake shoes 32 onto the internal
surface of the drum brake 28. When no forces are applied to rotate the S-
cam expander 30, the brake shoes 32 are pulled away from the drum
brake 28 by two biasing springs 34.
Rotation (arrows 36 and 36' on Figure 3) of the S-cam
expander 30 is actuated by an air cylinder 38 (see Figure 4) having a push
rod 40 that is mechanically connected to the S-cam expander 30 via a
lever 42 and a brake camshaft 44. The push rod 40 has a longitudinal
20 axis 46. The lever 42 and the camshaft 44 transfer the longitudinal
movement of the push rod 40 along axis 46 (arrows 48 and 48' on Figure
3 and Figure 4) in a rotational movement (see respective arrows 36 and
36') of the S-cam expander 30 about a rotational axis 50. It is to be noted
that the push rod 40 is secured to the lever 42 via a yoke 51 and a bolt 52.
As can be seen from Figure 4, the air cylinder 38
contains diaphragms 54, that uses the air pressure (illustrated by arrows
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56 in Figure 3) behind the diaphragm 54 to produce a linear driving force
pushing the push rod 40, that is secured to the diaphragms 54, in the
direction of arrow 48'. When the pressure is released in the air cylinder
38, springs 58 (Figure 4) pull back the push rod 40 in the direction of arrow
48.
Since the braking action is caused by the contact
between the brake shoes 32 and the internal surface of the drum brake 28
and that this contact is indirectly triggered by air pressure onto the
diaphragms 54, any wear of parts or loosening between the diaphragms
54 and the brake shoes 32 can cause failure of the braking action, when
the push rod 40 maximum stroke has been reached.
As will appear obvious to someone skilled in the art,
15 loosening of the mechanism of a drum brake assembly 18 will usually
result in travel of its push rod 40. Measurement of the position of the push
rod 40 can thus allow the assessment of brake wear and therefore of
possible failure of the braking action.
20 Turning now to Figure 5 of the appended drawings,
sensor assemblies 12A-12H will now be described. Since the sensor
assemblies 12A-12H are identical and for concision purposes, only the
sensor assembly 12A will be described hereinbelow.
25 The sensor assembly 12A includes a mounting assembly
58, a sensor 60 and a sensor electronic circuit 62 (see Figure 1 ).
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The mounting assembly 58 is configured to mount the
sensor 60 to the push rod 40 for movement in unison.
A V-plate 64, present on most trucks, is used to mount
the air cylinder 38 to the axle 22. The V-plate 64 has a first portion 66
secured to the air cylinder 38 and a second portion 68 secured to one of
the axles 22 of the vehicle 24. The second portion 68 includes an
aperture 70 for the passage of the push rod 40.
10 The mounting assembly 58 includes an S-shaped
bracket 72 and a sensor-securing nut in the form of a universal joint 74.
The universal joint 74 is mounted to one of the air drum's 38 mounting
bolts and is centered about a longitudinal axis 76 generally parallel to the
push rod 40.
The bracket 72 has a central flat portion 78 and first and
second opposite perpendicular end portions 80 and 82. The first end
portion 80 includes an integral ring 84 so configured and sized to snugly
fit on the push rod 40. Of course, a fastener (not shown) may also be
20 used to secure the ring 84 to the rod 40. The second end portion 82
includes an aperture (not shown) to receive a portion of the sensor 60 as
will be described hereinebelow.
The bracket 72 and the universal joint 74 are so
25 advantageously configured and sized as to facilitate the installation of
the
sensor 60 near the push rod 40. The use of one the air drum's mounting
bolts also facilitates the installation on the sensor assembly 12. Indeed,
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these mounting bolts are usually and easily accessible.
It has also been found that the displacement of the push
rod 40 has a small vertical component due to rotational movement of the
lever 42. The use of the universal joint 74 is therefore advantageous
since it allows the sensor 60 to follow the movement of the push rod 40 in
more than one direction. The measurements taken by the sensor 60 is
therefore more reliable. Its lifetime also increases.
10 It is to be noted that the bracket 72 and the other parts
of the mounting assembly 58 can have other configurations without
departing from the spirit of the present invention.
The sensor 60 includes a cylindrical hollow body 86
15 having a large portion 88 and two narrow end portions 90 and 92,
corresponding respectively to the proximal end 94 and the distal end 96
of the cylindrical hollow body 86. The cylindrical hollow body 86 includes
a cylindrical bore 87. The bore 87 is generally centered about the
longitudinal axis 76.
The sensor 60 further includes a sliding rod 98 having a
proximate end 100. The rod 98 is so coaxially and slidably mounted in the
bore 87 as to reciprocate. An expansible cover 102 is provided to protect
the slip joint between the sliding rod 98 and the hollow body 86. The
25 sensor 60 also includes a cylindrical magnet 104 so fixedly mounted to the
sliding rod 98 as to be in the large portion 88 of the hollow body 86, and
a linear Hall effect sensor 106 mounted to the inner surface of the large
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portion 88 of the hollow body 86. The large portion 88 allows sufficient
space for the cylindrical magnet 104 and the Hall effect sensor 106. As
will appear obvious to a person skilled in the art, the Hall effect sensor 106
is magnetically coupled with the cylindrical magnet 104.
5
The narrow end portion 90 of the hollow body 86 is
fixedly connected to the first portion 66 of the V-plate 64 via the universal
joint 74. The proximate end 100 of the sliding rod 98 is fixedly mounted to
the second end portion 82 of the bracket 72.
Since the sliding rod 98 of the sensor 60 is fixedly
connected to the push rod 40 via the bracket 72 and since the sensor 60
is generally parallel to the push rod 40, a longitudinal movement of the
push rod 40 infers a longitudinal movement to the sliding rod 98 of the
sensor 60 and to the cylindrical magnet 104 mounted thereto. As will be
explained hereinbelow, the Hall effect sensor 106 measures this
movement and generates a signal accordingly. The sensor, according to
a preferred embodiment of the present invention, allows measurement of
longitudinal movement of the push rod in the order of 1/100 of an inch
(about 0.25 mm).
Since the sensor 60 is positioned near the brake
assembly 18, it is subjected to adverse conditions, such as corrosion, road
hazards, cold and hot temperatures, etc. As will appear obvious to
25 someone skilled in the art, the sensor 60 has been designed to withstand
such adverse conditions while providing accurate readings. Indeed, the
hollow body 86 and the sliding rod 98 of the sensor 60 are preferably
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made of brass for its mechanical strength and low coefficient of friction,
and also because it does not affect the magnetic field produced by the
cylindrical magnet 104 and therefore the reading of the Hall effect sensor
106.
The hollow body 86 is advantageously covered by
UHMW (Ultra High Molecular Weight) material, such as UHMW
polyethylene, to protect the sensor 60 from abrasion or impact. For the
same reason and also to insulate the slip joint between the sliding rod 98
and the hollow body 86, the expansible cover 102 is advantageously
made of neoprene.
The cylindrical hollow body 86 includes a conduit 108 to
allow passage of a wire 110 connecting the linear Hall effect sensor 106
to the sensor electronic circuitry 62 (see Figure 1 ).
In a preferred embodiment of the present invention, each
sensor 60 is connected to a sensor electronic circuit 62.
20 The sensor electronic circuitry 62 includes a micro
controller, a memory chip, a communication chip and a tell tale Hall effect
sensor (not shown). These components are neither restrictive nor
essential, and other components producing globally the same results
described hereinbelow can also be used.
The micro controller is configured to collect the signal
generated by the Hall effect sensor 106 and to correct this signal. For
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example, the micro controller corrects the voltage for temperature using
the readings from the tell tale Hall effect sensor. An adjusted polynomial
equation is also used to transform the corrected voltage signal to a push
rod position value.
The micro controller is also advantageously programmed
to take readings at intervals defined by pre-determined criteria.
The memory chip can advantageously store values that
are to be used either by the sensor 60, the on-board controller 14 or the
remote controller 16. For example, each memory chip can be
programmed with different brake wear thresholds or sensor parameters.
The micro controller can also advantageously detect
other problems in the brake assembly 18, such as pressure drop in the air
drums 38 and also generate an alarm accordingly by analyzing the
previously stored values.
As will appear obvious to a person skilled in the art, the
fact that the micro-controller is programmable gives flexibility to the brake
wear managing system 10.
To protect the sensor electronic circuitry from vibration,
abrasion or impact, the sensor electronic circuitry is advantageously
covered with a sealant such as epoxy adhesive,
According to a most preferred embodiment of the
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present invention, two junction boxes 112, one for the front wheels,
another for the rear wheels, are used to relay signals from each sensor
electronic circuit 60 to the on-board controller 14. These junction boxes
112 are optional.
Sensor signals, in the form of push rod position values,
are then transferred to the on-board controller 14 by the communication
chip via the junction boxes 112. Conventional data cables 114 and 116
respectively connect each sensor 60 to one of the junction boxes 112 and
the two junction boxes 112 to the on-board controller 14. Other
connecting means, such as a radio emitter and a radio receiver can also
be used for these data connections. The on-board controller 14 is
configured to receive the signals from each sensor 12.
The number and location of the junction boxes 112 may
vary without departing from the spirit of the present invention.
The on-board controller 14 is advantageously located in
the tractor unit 118 of the truck 24 and more specifically on the control
board (not shown) thereof. The driver of the truck can therefore see the
on-board controller 14 while he is driving.
The on-board controller 14 has a display 120, a plurality
of program buttons 122 and ports (not shown) to connect the electrical
wires 116 coming from the junction boxes 112.
The display 120 may take many forms from a display
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monitor, a LCD (Liquid Crystal Device) screen to simple indicator lights.
The display 120 can be replaced or supplemented by
another output device such as an audio alarm. Conventional display and
5 audio alarm are believed well known in the art and will not be described
in further detail herein.
The on-board controller 14 is configured to handle
communications between the remote controller 16 and the sensor
10 assemblies 12A-12H, to generate brake wear condition signals in
response to sensor signals and to display information on the display 120
as will be described hereinbelow.
The on-board controller 14 is also configured to assess
15 the validity of the sensor assemblies 12A-12H signals by analyzing and
cross comparing those signals.
Brake wear condition signals can take many forms from
push rod position values, percentages of threshold, alarm signals to time
20 before brake failure, etc. The brake wear condition signals may
alternatively be analog or digital. Evidently, the on-board controller 14 is
configured to produce such brake wear condition signals in response to
sensor signals.
25 Although, the on-board controller 14 and the sensor
electronic circuitry 62 have been described as two separate components,
it is believed within the reach of someone skilled in the art to incorporate
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these two components into a single assembly configured to perform the
tasks of both the controller 14 and the sensor electronic circuitry 62.
According to the first embodiment of the present
5 invention, the on-board controller 14 further includes an on-board
emitter/receiver (not shown) to exchange information with the remote
controller 16 (see propagated signal 17 in Figure 1).
The remote controller 16 is advantageously in the form
10 of a computer that includes user input devices, such as a keyboard, a
mouse, a touch screen and/or a microphone with voice recognition
software, output devices such as a display monitor, speakers and/or a
printer, a remote emitter/receiver to exchange information from the on-
board controller 14 and storing devices such as RAM (Read Access
15 Memory) or ROM (Read Only Memory) memories, a CD-ROM drive, etc.
Optionally, the remote controller 16 can further be
connected to a network of computers such as the Internet for sharing data
with other controllers or computers.
Alternatively, the remote controller can be in the form of
a laptop computer 124 (see Figure 6), a handheld PC, a palm-size PC or
any other computer system configured to perform the functions described
above.
The on-board and remote emitter/receivers are part of a
conventional wireless communication system, configured to exchange
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information between the on-board controller 14 and the remote controller
16. The emitter/receiver can take many forms including, a radio
transceiver and a wireless phone. Since such conventional wireless
communication systems are believed well known in the art, they will not be
described in further detail herein.
The communication system can advantageously be
connected to a GPS (Global Positioning System) transmission unit (not
shown) to allow monitoring of the geographic position of the vehicle.
Turning now briefly to Figure 6 of the appended
drawings, a second embodiment of the present invention will now be
described. According to this second embodiment of the present invention,
the remote controller 124 is directly connected to the on-board controller
15 14 via a data cable 126. As will appear obvious to a person with ordinary
skills in the art, the above-described remote communication system in this
case not required. When such a cable connection is used between the
remote and on-board controllers 124 and 14 is used, the data is stored in
the on-board controller 14 during normal operation of the vehicle 24 and
transferred to the remote controller 124 during vehicle's inspection and or
repairs.
The principle of operation of the brake managing system
10 will now be described in further detail.
According to the size and configuration of the vehicle 24
onto which the brake managing system 10 is installed, each sensor
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assembly 12 is assigned a network address.
In a preferred embodiment, the remote controller 16 (or
124) is programmed with a graphical user interface to allow the user of the
5 system 50 to visualize the position of each sensor assembly 12A-12H on
a schematic representation of the vehicle 24, knowing its network address.
Different configurations of vehicles are advantageously stored in the
remote controller 16 memory.
Both the on-board and the remote controller 14 and 16
can be used to visualize the travel of all push rods 40 in percentage of
pre-determined thresholds or in absolute distance. If one of the sensor
assemblies 12A-12H is malfunctioning or if the connection is broken, a
corresponding message is sent to the on-board controller 14 and/or
remote controller 16 that can then generate an alarm.
When the driver depresses the brake pedal, each push
rod 40 is pushed in the direction of arrow 48' (Figure 3), as explained
hereinabove. The longitudinal displacement of the push rod 40 is
20 detected by the sensor 60. Since this longitudinal displacement
characterizes the brake wear, the sensor 60 generates a signal responsive
to brake wear. The on-board controller 14 then receives the signals from
each sensor assembly 12. If the on-board controller 14 does not receive
the signal from one of the sensor assemblies 12A-12H, a message is
shown accordingly on the display 120 of the on-board controller 14.
Alternatively, the driver can access information stored by each sensor
assembly 12, by using the program buttons 122 of the on-board
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controller 14.
The on-board controller 14 then compares each push
rod travel with a corresponding predetermined threshold. These two
values are transferred from the micro controller of the sensor assemblies
12A-12H to the on-board controller 14. The on-board controller 14 then
shows on the display 120, for each brake assembly 18, the push rod 40
travel and may trigger an alarm accordingly.
10 The remote controller 16 is configured to be operated in
either two different modes: maintenance mode or operational mode. Each
of these modes can be implemented on a single remote controller or on
two distinct controllers, configured to perform functions as described
hereinbelow.
The maintenance mode is used mainly for the
installation, the verification and maintenance of the sensor assemblies.
More precisely, the maintenance mode allows to program the sensor
assemblies 12A-12H according to pre-determined operating conditions.
The maintenance mode allows the remote controller to
send signals to the sensor assemblies 12A-12H to verify the operating
conditions thereof.
For each sensor assembly 12, a plurality of pushrod
travel thresholds can be programmed. Different thresholds can thus be
programmed to warn the driver or a remote technician at different stages
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of brake wear. The threshold values can be the same for all sensor
assemblies 12A-12H or they can be different.
In a preferred embodiment of the present invention, two
different thresholds can be programmed for each assembly 12. The first
threshold could correspond, for example, to a 134 inch (about 4.45 cm)
push rod 28 travel and the second threshold to a 2 inch (about 5.08 cm)
travel of the rod 28. Two different levels of alarm can be assigned to
those thresholds. The typical push rod 28 travel is about 2 inches (about
6.03 cm).
The operational mode allows to perform the remote
monitoring of the brake assemblies 12A-12H, the computing of brake wear
forecasts, the scheduling of brake maintenance and the dispatching of
vehicles according to a maintenance schedule.
The operational mode also provides visual tools to
assess the operating performance of the sensor assembly 12A-12H and
to help identify problems of the brake assemblies 18.
The operational mode can also be used to stock data
and to use those data to prepare statistical analyses on the brake
assemblies 18, such as the average life span, time to reach a certain wear
percentage, etc.
A brake managing system according to embodiments of
the present invention allows for the creation of historical databases.
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These databases can includes information such as push rod positions in
time, break wear conditions by vehicle, by driver, etc. The databases
could facilitate the detection of recurrent problems.
5 The remote controller 16 can also use the information in
such databases to forecast brake wear, thus optimizing the lifetime of
each brake assembly without risking brake failure. The calculation can
optionally be performed by each micro controller or by the on-board
controller.
Obviously, the remote controller 16 can be configured to
perform only some of the fuctions cited above.
In a preferred embodiment of the present invention, the
controller on-board controller 14 can collect information from the odometer
(not shown) of the vehicle 24. That information can be sent from the
controller to each micro controller to be stored. All the readings done by
the sensor assemblies 12A-12H could then be indexed according to the
mileage of the vehicle. The remote controller 16 could further use those
data to compute forecasts, for example, in function of the mileage.
The two modes of operation of the brake wear managing
system can be implemented by two different remote controllers or by a
single one without departing from the spirit of the present invention.
It is also believed within the reach of someone skilled in
the art to configure the remote controller 16 (or 124) to perform the above-
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mentioned functions.
Even though the preferred embodiment has been
described as one mounted to a truck, a brake wear managing system,
5 according to the present invention, can also be installed on other vehicles
such as buses.
Although the present invention has been described
hereinabove by way of preferred embodiments thereof, it can be modified,
10 without departing from the spirit and nature of the subject invention as
defined in the appended claims.
