System for monitoring the temperature of wheel bearings in railroad cars

[0001] This application claims priority to my provisional application 60/550,432 filed Mar. 8, 2004, which by this reference is incorporated herein.

[0002] The instant invention relates generally to systems for detecting defects in wheel bearings of railroad car due to overheating by monitoring the temperature of such bearings.

[0003] Overheating of wheel bearings in railroad cars can lead to serious accidents if not noticed before major damage occurs. The Office of Safety Analysis of the Federal Railroad Administration reports that during the period between January and November 2003 there have been 1,477 train accidents attributable to equipment defects and failures. In fact, 180 of such incidents were directly related to bearing or breaks failures (See “Federal Railroad Administration, 2003 Report on Train Accidents due to Equipment Failures”). Such accidents are especially dangerous when they involve passenger carriages and freight cars carrying hazardous cargo, such as explosives and nuclear waste.

[0004] A system for detection of overheating in wheel bearings, aside of its value as a means for preventing accidents, injuries and deaths, would also allow for rail cars' maintenance schedule to be implemented in a timely fashion—an opportunity for cost-saving.

[0005] Federal Railroad Administration's “Rolling Stock program” places emphasis on the development and improvement of equipment defect detection via wayside and onboard systems. Such systems promote early defect detection and help prevent derailments due to equipment failure. They also permit condition-based maintenance of car and locomotive components.”(See “Federal Railroad Administration, Railroad Research and Development Program, Section 4.3 Rolling Stock and Components”)

[0006] The advent of inexpensive and reliable sensors, microprocessors and electronics makes such automated systems for detection of overheating practical and cost-effective.

[0007] It is a feature of he present invention to provide an on-board system for railroad cars and carriages, which detects and provides signals that alert responsible personnel to incidents of bearing overheating and identify the location of the overheated bearings.

[0008] The system provided by the invention improves heretofore-proposed systems such as disclosed in U.S. Pat. Nos. 3,629,572; 3,697,744; 3,731,087; 3,812,343; and 4,659,043, which include the wayside systems relying on detection of infrared signatures from overheated bearings. The present invention provides an on-board system, which is continuously operating thereby enabling real time detection of bearing failures due to lack of lubrication or mechanical defects as evidenced by overheating. The wayside IR detectors also frequently suffer from poor sensitivity; are widely spaced so that they may not detect an overheated bearing in time to prevent an accident; are not responsive to scanning bearings of cars wherein several (say, three) different sizes of wheels are employed; are prone to falsely respond to sources of IR radiation other than the car bearings.

[0009] FIG. 1 is a block diagram of a system for detection of overheating in wheel bearings of railroad cars in accordance with the invention.

[0010] FIG. 2 is a block diagram of another embodiment of the system for detection of overheating in wheel bearings of railroad cars in accordance with the invention.

[0011] FIG. 3 is a block diagram of a central monitoring station for the system depicted in FIG. 2.

[0012] With reference to FIG. 1, temperature sensors 10, 11, 12, and 13 are installed in close proximity to the bearings of each of the wheels of a railroad car or carriage. Railroad cars usually have four axles and eight wheels, however, only the sensors for four wheels are shown; the sensors for all eight wheels are identical. The sensors generate electrical signals analog to the temperature of these bearings. The signals are amplified by the amplifiers 14, 15, 16, and 17 and passed on to a multiplexer module 26, which contains a solid state switching circuit that continuously cycles, serially selecting inputs from amplifiers 14, 15, 16, and 17 and directing the signals from these inputs to the output 28. The cycling is controlled by the clock signals from the module 30 via line 27.

[0013] Module 30 is an A/D converter that converts the signals analog to the bearing temperature into digital data. Module 30 also contains a digital clock and a circuit for imparting a string of code that identifies the bearing where the information originates. The digital data comprise information on the temperature of the bearings and the bearing I.D. code. The data from module 30 (consisting of four groups of temperature readings and accompanying codes) are fed into the comparator module 33. This module contains a microprocessor or logic programmed to temporarily store several consecutive temperature readings from each bearing and compute the average temperature values of these readings. The module 33 continuously compares the magnitudes of the averaged temperature data from the four sensors 10, 11, 12, and 13 with the temperature data from each sensor for each cycle of four groups of temperature data and generates an overheating alarm signal if and when it determines that the temperature data from one of the bearings indicates that the temperature exceeds by a preset limit value the average temperature from all four or just the other three bearings. As a result, false alarms are prevented that could be generated in hot weather conditions raising the temperature in all wheel bearings; the effects of any spurious signals are also suppressed. Module 33 also attaches the I.D. code generated in the module 30 corresponding to the overheated bearing to any alarm signal, thus identifying the specific bearing, which is overheating.

[0014] The alarm signal is input into module 36, which acts as a demultiplexer and causes one of the outputs 37, 38, 39, or 40 corresponding to an overheated bearing to activate one of the LEDs 22,23, 24, or 25. The LEDs are mounted at a convenient location near the carriage or vehicle wheels and are intended to facilitate visual determination of a defective bearing, i.e., which of the bearings had overheated. Other types of signaling devices could also be used instead of LEDs.

[0015] The data from the module 36 are also entered into the transmitting module 42, which transmits via the antenna 44 the alarm signal to a central monitoring station in the locomotive. Alternately the alarm signals can be transmitted via a wire link to the central monitoring station from the terminal 43.

[0016] The system is self-powered to simplify the installation. The magnet core 50 of the solenoid coil 49 in the power generator is suspended on springs 51 and 52 and moves vertically up and down as the carriage or the vehicle moves. As a result, electric current is generated in the coil of the solenoid 49. The current is rectified by the diode 48, used to charge the battery 46 and to pass through the resistor 47 to the zener diode 45, which maintains the voltage at the desired level of, say, five volts. The terminal 53 is connected to terminals 18, 19, 20, 21, 29, 31, 34, 41, and 54 to provide power to the system. Alternately, the system could be powered from the power bus of the railroad car or carriage or other vehicle.

[0017] The temperature sensors may be thermocouples, thermistors, fiber optic temperature sensors, and other types, though thermistors and fiber optic sensors have two advantages over thermocouples in this application in that they do not require a reference (cold) junction and are generally more rugged.

[0018] FIG. 2 depicts another embodiment of the system. Separate but identical modules A, B, C, and D are installed in the proximity of the railroad car or carriage bearings. The railroad cars have four axles and eight wheels, however, only the sensor modules for four wheels are shown; the sensor modules for all eight wheels are identical. Each module is self-contained and self-powered, thus there are no wired connections between the modules, which in some cases may facilitate the installation of the monitoring system.

[0019] Each module comprises temperature sensors 50, 60, 70, and 80, installed in close proximity of the wheel bearings. The analog signals from these sensors are amplified in 51, 61, 71, and 72; then the amplified signals are passed to the A/D converters 52, 62, 72, and 82. The digitized signals are input, respectively, into modules 53, 63, 73, and 83 where a digital code identifying each particular bearing is generated and attached to the signal string. Next, the signals are fed into transceivers 54, 64, 74, and 84, which transmit the data to the central monitoring station depicted in FIG. 3. Modules 54, 64, 74, and 84 also receive signals from the central monitoring station when an overheated bearing is detected. When such a signal is received, modules 54 through 84 activate the respective LEDs 50A, 60A, 70A, and 80A that are situated close to the wheel bearings to provide visual indication of a fault.

[0020] Each module is equipped with a power generator 55-58, 65-68, 75-88, and 85-88, as described with reference to FIG. 1 that provides the electric power to the components of each module A, B, C, and D. If a car or a carriage has more than four wheels, the appropriate number of modules would be installed.

[0021] Referring now to FIG. 3, which shows in a block diagram format the central monitoring station, module 90 is a transceiver which received signals from the remote modules A, B, C, and D of FIG. 2, and transmits signals back to these modules when an overheated bearing is detected, thus activating the appropriate LED. The signals from all remote modules are input via terminal 92 into the control module 94, which temporarily stores and averages the digital signals received from each module and compares these averaged values to each other. If the magnitude of one of the values exceeds a preset level, an alarm is initiated. The alarm is visually displayed on the display module 95 and alarm sound is generated. In addition, the control module 94 sends a signal back to transceiver module 90, which transmits a signal to one of the modules, A, B, C, or D to activate the corresponding LED. Power to the central monitoring station is supplied via terminals 96.