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.

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.

Claims

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.