WO2005059503A1

WO2005059503A1 - Wheel slip detection system for railway vehicles

Info

Publication number: WO2005059503A1
Application number: PCT/KR2004/003234
Authority: WO
Inventors: Young-Guk Kim; Seog-Won Kim; Chan-Kyoung Park; Jin-Yong Mok; Young-Jae Han
Original assignee: Korea Railroad Research Institute
Priority date: 2003-12-19
Filing date: 2004-12-10
Publication date: 2005-06-30
Also published as: KR100583269B1; CN1898543A; CN100538313C; KR20050062956A

Abstract

Awheel slip detection system for determining whether a railway vehicle slips is provided. The system includes rotational speed detectors (230, 240, 330 and 340) for detecting rotational speeds of front and rear wheel sets (202, 204, 302 and 304) of test and neighboring wheel trucks (200 and 300) of the railway vehicle, an air pressure meter (400) for detecting an air pressure applied to brake a brake disc (236) on the front wheel set 202 of the test wheel truck (200), an A/D converter (460) for converting the detection signals into digital signals, and a data collector (500) for determining whetherthe test wheel truck slips, based on the digital signals. The system can easily determine whether the railway vehicle slips when a braking force is applied, simply by measuring the rotational speeds using the rotational speed detectors and measuring the air pressure using the air pressure meter.

Description

Description WHEEL SLIP DETECTION SYSTEM FOR RAILWAY VEHICLES Technical Field

[1] The present invention relates to a wheel slip detection system for railway vehicles, and more particularly to a wheel slip detection system capable of determining whether or not a railway vehicle slips, based on both the rotational speeds of wheel sets of the railway vehicle and the air pressure of a brake cylinder for applying a mechanical braking force.

[2] Background Art

[3] Since the wheels of railway vehicles and rails, on which the railway vehicles travel, are generally made of steel, the coefficient of friction between the wheels and the rails is low.

[4] If a mechanical braking force applied to a railway vehicle to brake the vehicle is greater than the friction between the rails and the wheels, the railway vehicle may slip on the rails with the wheels stopped, thereby abrading and damaging part of the wheels.

[5] That is, since railway vehicle wheels and rails are made of steel, they have a low frictional coefficient, and thus the friction between the wheels and the rails is low. If the railway vehicle slips on the rails due to the friction being lower than the braking force, the rails and the wheels are abraded and damaged, which reduces the comfort of the passengers and the safety of railway vehicles.

[6] An electronic brake control unit in the railway vehicle performs anti-skid control to prevent the slip. If the anti-skid control is normally activated, the railway vehicle is prevented from slipping, but otherwise the railway vehicle slips. Thus, there is a need to determine whether or not the railway vehicle slips.

[7] Disclosure of Invention Technical Problem

[8] Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a wheel slip detection system for railway vehicles, which can easily check whether or not a railway vehicle slips when a braking force is applied, simply by measuring the air pressure of a brake cylinder and the rotational speeds of wheel sets of a test wheel truck, which is a subject of slip monitoring, and a neighboring wheel truck adjacent thereto of the railway vehicle.

[9] It is another object of the present invention to provide a wheel slip detection system for railway vehicles, which can determine whether or not an electronic brake control unit in a railway vehicle normally activates anti-skid control based on the check as to whether or not the railway vehicle slips when a braking force is applied, so that the rails are prevented from being damaged by decreasing the speed of the railway vehicle if it is determined the anti-skid control is not normally activated.

[10] Technical Solution

[11] In accordancewith the present invention, the above and other objects can be accomplished by the provision of a wheel slip detection system of a railway vehicle, the system comprising first and second rotational speed detectors provided on outer portions of front and rear wheel sets of a test wheel truck of the railway vehicle, respectively, the first and second rotational speed detectors producing two respective pulse signals according to rotation of the front and rear wheel sets of the test wheel truck; third and fourth rotational speed detectors provided on outer portions of front and rear wheel sets of a neighboring wheel truck of the railway vehicle adjacent to the test wheel truck, respectively, the third and fourth rotational speed detectors producing two respective pulse signals according to rotation of the front and rear wheel sets of the neighboring wheel truck; first to fourth Frequency to Voltage (F V) converters for receiving the four pulse signals from the first to fourth rotational speed detectors and converting the received pulse signalsinto four analog voltage pulse signals, respectively; an air pressure meter for measuring an air pressure applied to a cylinder in a brake assembly for braking a brake disc of the front and rear wheel sets of the test wheel truck; an Analog-to-Digital (A/D) converter for receiving the four analog voltage pulse signals from the first to fourth F V converters, converting the received analog voltage pulse signals into four digital pulse signals, receiving an analog air pressure measurement signal from the air pressure meter, and converting the received analog air pressure measurement signal into a digital air pressure measurement signal; and a data collector for receiving the four digital pulse signals and the digital air pressure measurement signal from the A/D converter, calculating four rotational speeds of the front and rear wheel sets of the test and neighboring wheel trucks based on the four digital pulse signals, setting the largest of the four rotational speeds as a reference rotational speed, determining whether or not the difference between the rotational speed of the front or rear wheel set of the test wheel truck and the reference rotational speed is less than an acceptable limit, and determining whether or not a braking force is applied to the test wheel truck, based on the digital air pressure measurement signal received from the A/D converter, thereby determining whether or not the test wheel truck slips.

[12] Preferably, the data collector comprises a power supply for supplying DC power; a power switch for turning ombff the power supply; a memory for storing an operating system for initializing the system and an application program for calculating the four rotational speeds based on the four digital pulse signals and calculating the air pressure in the cylinder based on the digital air pressure measurement signal; a controller for receiving power from the power supply as the power switch is turned on, and activating the operating system and the application program stored in the memory for receiving the four digital pulse signals and the digital air pressure measurement signal from the A/D converter, calculating the four rotational speeds of the front and rear wheel sets of the test and neighboring wheel trucks based on the four digital pulse signals, setting the largest of the four rotational speeds as the reference rotational speed, determining whether or not the difference between the rotational speed of the front or rear wheel set of the test wheel truck and the reference rotational speed is less than the acceptable limit, and determining whether or not a braking force is applied to the test wheel truck, based on the digital air pressure measurement signal received from the A/D converter, thereby determining whetheror not the test wheel truck slips; and a display for displaying a travel speed and a travel distance of the test wheel truck, calculated by the controller.

[13] Preferably, the display includes a liquid crystal display.

[14] Preferably, the data collector further comprises an interface unit for transferring the air pressure and the rotational speeds of the front and rear wheel sets of the test wheel truck, calculated by the controller, to an external device.

[15] Preferably, the data collector further comprises a key input unit for inputting commands to the controller.

[16] Preferably, the controller calculates and stores the four rotational speeds and the air pressure in the memory.

[17] Preferably, the first pulse detector comprises a disc-shaped pulse generation gear provided on the front wheel set of the test wheel truck at an outer portion of the front wheel set, the gear having a number of teeth spaced at predetermined intervals so as to rotate as the front wheel set rotates; and a prosmity switch provided near the teeth to produce a pulse signal according to movement of the teeth of the front wheel set as the front wheel set rotates.

[18] Preferably, the wheel slip detection system further comprises a signal amplifier for amplifying a weak analog air pressure measurement signal output from the air pressure meter by a predetermined gain to produce a practically usable signal.

[19] Advantageous Effects

[20] It is possible to easily check whether or not a railway vehicle slips when a braking force is applied, simply by measuring rotational speeds of front and rear wheel sets of test and neighboring wheel trucks of the railway vehicle using rotational speed detectors provided on the front and rear wheel sets, and measuring air pressure in a brake cylinder using an air pressure meter provided on the brake cylinder.

[21] It is also possible to determine whether or not an electronic brake control unit in a railway vehicle normally activates anti-skid control based on the check as to whether or not the railway vehicle slips when a braking force is applied, so that the rails are prevented from being damaged by decreasing the speed of the railway vehicle if it is determined that the anti-skid control is not normally.

[22] Brief Description of the Drawings

[23] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[24] Fig. 1 is a diagram illustrating rotational speed detectors in a wheel slip detection system for railway vehicles according to the present invention, which are provided on wheel sets of a railway vehicle to detect the rotational speeds of the wheel sets;

[25] Fig. 2 is a diagram illustrating an air pressure meter in the wheel slip detection system according to the present invention, which is provided on a brake assembly of a railway vehicle to measure the brake air pressure;

[26] Fig. 3 is a block diagram illustrating a wheel slip detection system for railway vehicles according to the present invention;

[27] Fig. 4 is a flow chart illustrating how the wheel slip detection system according to the present invention operates;

[28] Fig. 5 is a graph illustrating changes in the rotational speeds when anti-skid control is normally activated; and

[29] Fig. 6 is a graph illustrating changes in the brake air pressure when the anti-skid control is normally activated.

[30] Best Mode for Carrying Out the Invention

[31] Fig. 1 illustrates rotational speed detectors in a wheel slip detection system for railway vehicles according to the present invention, which are provided on wheel sets of a railway vehicle to detect the rotational speeds of the wheel sets. As shown in Fig. 1, test and neighboring wheel trucks 200 and 300 of a railway vehicle, which support a vehicle body 100 of the railway vehicle, include two front wheel sets 202 and 302 and two rear wheel sets 204 and 304, each wheel set including wheels 210a and 210b and axles 220, as with general wheel trucks. The test and neighboring wheel trucks 200 and 300 are each equipped ith various feature devices such as a device for reducing vibrations caused by the wheels 210a and 210b and rails, and a device for braking the railway vehicle.

[32] The test wheel truck is used to test whether or not the railway vehicle slips, and the neighboring wheel truck 300, which is adjacent to the test wheel truck 200, is used to determine whether or not the difference between the rotational speed of the front or rear wheel set 202 and 204 of the test wheel truck 200 and a reference rotational speed exceeds an acceptable limit. According to the present invention, in order to detect the wheel rotational speed of a railway vehicle, first and second rotational speed (or frequency) detectors 230 and 240 are provided on the front and rear wheel sets 202 and 204 of the test wheel truck 200, and third and fourth rotational speed detectors 330 and 340 are provided on the front and rear wheel sets 302 and 304 of the neighboring wheel truck 300.

[33] The first to fourth rotational speed detectors 230, 240, 330 and 340, which are provided on the wheel sets 202, 204, 302 and 304 at outer portions thereof, include pulse generation gears 232, 242, 332 and 342, and prosmity switches 234, 244, 334 and 344, respectively.

[34] In more detail, the accuracy of the travel speed detection depends on the number of teeth spaced at predetermined intervals on the pulse generation gears 232, 242, 332 and 342, each of which is in the shape of a disc. In order to increase the accuracy of the travel speed detection, the pulse generation gears 232, 242, 332 and 342 need to have as many teeth as possible.

[35] The prosmity switches 234, 244, 334 and 344 are provided near the teeth of the pulse generation gears 232, 242, 332 and 342. The prosmity switches 234, 244, 334 and 344 emit light and generate pulse signals according to light reflected from the teeth of the pulse generation gears 232, 242, 332 and 342 which rotate as the wheel sets 202, 204, 302 and 304 rotate.

[36] The pulse signals generated from the prosmity switches 234, 244, 334 and 344 are subjected to various conversion processes, which will be described later, and are finally used to calculate the rotational speeds of the wheel sets 202, 204, 302 and 304 in a data collector.

[37] Fig. 2 is an enlarged view of the front wheel set 202 of the test wheel truck 200. As shown in Fig. 2, two brake discs 236 are coupled to the axle 220 and are spaced at a predetermined interval between the wheels 210a and 210b of the front wheel set 202 of the test wheel truck 200. A brake assembly 250 is provided to apply a braking force to the brake discs 236. The brake assembly 250 receives compressed air generated from an air tank 260 through a duct 270.

[38] The brake assembly 250 includes brake pads 252a and 252b for holding both sides of the brake disc 236, and a brake cylinder 254 for providing braking power to the brake pads 252a and 252b.

[39] The compressed air generated from the air tank 260 is supplied to the cylinder 254 through the duct 270, and the cylinder 254 then actuates the pads 252a and 252b to hold the brake discs 236, thereby braking the wheels 210a and 210b.

[40] An air pressure meter 400 is provided between the air tank 260 and the brake assembly 250 to measure an air pressure applied from the air tank 260 to the brake as sembly 250. The air pressure meter 400 includes a pressure-to-voltage converter that uses a strain gauge to measure the air pressure. The strain gauge, which is provided in the air pressure meter, converts a deformation caused by a change in the air pressure into an electricity value (for example, mV).

[41] If the braking force applied to the front wheel set 202 of the test wheel truck 200 is smaller than the friction between the wheels 210a and 210b and the rails, the braking works normally, but otherwise the test wheel truck 200 slips, abrading the wheels 210a and 210b. The abrasion damages the rails and reduces the comfort of passengers and the safety of the railway vehicle.

[42] In order to prevent the railway vehicle from slipping when the braking force is larger than the friction, the railway vehicle performs anti-skid control using an electronic brake control unit (not shown). However, there is a need to check whether or not the anti-skid control is normally performed. [43] If the railway vehicle slips, the anti-skid control is performed to reduce the brake air pressure of the cylinder 260 to be less than a preset pressure required for the braking so that the braking force is reduced to be less than the friction, thereby preventing the slip.

[44] Although the description of Fig. 2 has been given only for the front wheel set 202 of the test wheel truck 200, the same principle applies to the rear wheel set 204.

[45] Fig. 3 is a block diagram illustrating a wheel slip detection system for railway vehicles according to the present invention. As shown in Fig. 3, the wheel slip detection system according to the present invention includes first to fourth rotational speed detectors 230, 240, 330 and 340, firstto fourth Frequency to Voltage (F/V) converters 410, 420, 430 and 440, an air pressure meter 400, a signal amplifier 450, an Analog-to-Digital (A/D) converter 460, and a data collector 500.

[46] The first to fourth rotational speeddetectors 230, 240, 330 and 340 include pulse generation gears 232, 242, 332 and 342, and prosmity switches 234, 244, 334 and 344. The pulse generation gears 232, 242, 332 and 342 have a number of teeth that rotate as the wheel sets 202, 204, 302 and 304 rotate. The proximity switches 234, 244, 334 and 344, which are provided on the wheel sets 202, 204, 302 and 304 at outer portions thereof, emit light and generate pulse signals according to the movement of the teeth of the pulse generation gears 232, 242, 332 and 342 as the wheel sets 202, 204, 302 and 304 rotate.

[47] The F/V converters 410, 420, 430 and 440 receive the pulse signals from the first to fourth rotational speed detectors 230, 240, 330 and 340 and convert the received signals into analog voltage signals.

[48] The air pressure meter 400 measures an air pressure applied to a brake assembly 250 for braking brake discs 236 of the wheel sets 202, 204, 302 and 304. The air pressure meter 400 uses a strain gauge to convert a deformation caused by a change in the air pressure of the brake assembly 250 into an electricity value (for example, mV).

[49] The signal amplifier 450 amplifies a weak analog air pressure measurement signal output from the air pressure meter 400 by a predetermined gain to produce a practically usable signal.

[50] The A/D converter 460 converts the analog pulse signals received from the first to fourth rotational speed detectorsinto digital pulse signals, and converts the analog air pressure measurement signal received from the air pressure meter 400 into a digital signal.

[51] The data collector 500 receives the digital pulse signal and the digital air pressure measurement signal from the A/D converter 460, and calculates and stores rotational speeds of the wheel sets 202, 204, 302 and 304 and the air pressure of the brake assembly 250.

[52] Since the data collector 500 itself cannot handle the analog speed detection signals output from the first to fourth rotational speed detectors 230, 240, 330 and 340 and the analog air pressure measurement signal output from the air pressure meter 400, the A/ D converter 460 converts the analog signals into digital data suitable for processing in the data collector 500.

[53] The A/D converter 460 is preferably a multi-channel A/D converter with a sampling rate of lOOkS/s (100,000 samples per second) and a data resolution of 12 bits that correspond to 212.

[54] The data collector 500 includes a power supply510, a power switch 520, a memory 530, a controller 540, a display 550, an interface unit 560, and a key input unit 570.

[55] The power supply 510 supplies DC power to the data collector 500. The power switch 520 turns on and off the DC power output of the power supply 510.

[56] The memory 530 stores an operating system for operating the system, and an application program for receiving pulse signals and calculating rotational speeds of the wheel sets 202, 204, 302 and 304, and receiving and analyzing an air pressure measurement signal.

[57] The controller 540 receives power from the power supply 510 as the power switch 520 is turned on, and initializes the system by activating the operating system stored in the memory 530. The controller 540 receives the digital pulse data and the digital air pressure measurement data output from the A/D converter 460, and calculates rotational speeds of the wheel sets 202, 204, 302 and 304 and analyzes the air pressure of the brake assembly 250 using the application program to determine whether or not the railway vehicle slips.

[58] The display 550 includes a liquid crystal display (LCD) or the like for graphically displaying the calculated rotational speed data and the analyzed air pressure data so that the user can confirm the data with their naked eyes.

[59] The interface unit 560 is used to transfer the rotational speed and air pressure data calculated by the controller 540 and the rotational speed and air pressure data stored in the memory 530 to a specific system such as an external computer.

[60] The key input unit 570 is used to input commands for calculating and measuring the rotational speeds and the air pressure in the controller 540.

[61] The data collector 500 is preferably composed of an industrial system, for example, a device or computer including a Pentium 1GHz CPU, a 256 MB RAM, and a 20 GB hard drive.

[62] Using the application program stored in the memory 530, the data collector 500 calculates the air pressure and the rotational speeds based on the air pressure measurement signal output from the air pressure meter 400 and the pulse signals output from the prosmity switches 234, 244, 334 and 344 according to the rotation of the pulse generation gears 232, 242, 332 and 342.

[63] The travel speed of the railway vehicle can be calculated by the following equation:

[64] , 2πr total pu s count speed = x time number of pulses per revolution or

[65] , total pulse count x travel distance per pulse number of pulses per revolution

[66]

[67] In addition, the braking force can be calculated by substituting the air pressure measurement value obtained by the air pressure meter 400 into the following equation. [68] F (braking force) = (P A- F_s)x —xμ

[69] where "P" denotes cylinder pressure (i.e., air pressure in the cylinder), "F " denotes s spring force, "A" denotes cylinder area (i.e., the cross-sectional area of the piston), " i h " denotes caliper ratio, and "μ" denotes the coefficient of friction (of the shoe or pad). [70] Due to the following reason, not only the rotational speeds of the wheel sets 202 and 204 of the test wheel truck 200 but also the rotational speeds of the wheel sets 302 and 304 of the neighboring wheel truck 300 are used to test whether or not the test wheel truck 200 slips. If the test wheel truck 200 slips with both thefront and rear wheel sets 202 and 204 of the test wheel truck 200 fixed, the rotational speeds of the wheels 210a and 210b of the wheel sets 202 and 204 are detected as zero, and therefore any one of the rotational speeds of the wheels 210a and 210b of the wheel sets 202 and 204 cannot be set as a reference rotational speed for calculation of a rotational speed difference, which is described below. Thus, the rotational speeds of the four wheel sets 202, 204, 302 and 304 of both the test wheel truck 200, which is a subject of the slip monitoring, and the neighboring wheel truck 300 are all detected, and the largest of the detected rotational speeds is set as the reference rotational speed. Then, the difference between the reference rotational speed and the rotational speed of the wheels 210a and 210b of the front or rear wheel set 202 or 204 of the test wheel truck 200 is calculated, and it is then determined whether or not the calculated rotational speed difference is less than an acceptable limit.

[71] If the difference betweenthe rotational speed of the front or rear wheel set 202 or 204 of the test wheel truck 200 and the largest of the rotational speeds of the wheel sets 202, 204, 302 and 304 of the test and neighboring wheel trucks 200 and 300, which are calculatedbased on pulse signals output from the first to fourth rotational speed detectors 230, 240, 330 and 340 provided on the wheel sets 202, 204, 302 and 304, exceeds the acceptable limit, it is assumed that the front and rear wheel set 202 or 204 ofthe test wheel truck 200 is slipping, and the brake air pressure of the test wheel truck 200 is reduced to be less than a preset brake air pressure so that the rotational speed difference is reduced to be less than the acceptable limit, under the control of the electronic brake control unit (not shown). Here, if the brake air pressure returns to the preset brake air pressure with the rotational speed difference being higher than the acceptable limit, it is determined that the anti-skid control is not normally performed so that the test wheel truck 200 slips, abrading the wheels 210a and 210b.

[72] In other words, according to the present invention, based on the rotational speeds of the wheel sets 202, 204, 302 and 304 measured using the first to fourth rotational speed detectors 230, 240, 330 and 340, it is determined whether or not the front or rear wheel set 202 or 204 of the test wheel truck 200 slips. Here, if it is assumed that the test wheel truck 200 slips due to the rotation speed difference being higher than the acceptable limit, and a braking force is applied with a brake air pressure under the control of the electronic brake control unit, then the brake air pressure is calculated using air pressure measurement data obtained by the air pressure meter 400, and it is determined whether or not the anti-skid control is normally performed, based on the calculated air pressure.

[73] The operation of the wheel slip detection system for railway vehicles according to the present invention will now be described with reference to Fig. 4.

[74] If the data collector 500 receives power from the power supply 510 as the power switch 520 is turned on, the controller 540 actives the operating system stored in the memory 530, thereby initializing the system (S600). Here, various test information such as a test date and a vehicle number is input to the data collector 500 through the key input unit 570.

[75] If the initialized data collector 500 is ready to calculate the rotational speeds and travel distances of the wheel sets 202, 204, 302 and 304 of the test and neighboring wheel trucks 200 and 300, the collector 500 determines whether or not the railway vehicle travels. If the railway vehicle does not travel, the system switches to standby mode (S610).

[76] If the railway vehicle travels, rotating the wheel sets 202, 204, 302 and 304, the pulse generation gears 232, 242, 332 and 342 of the first to fourth rotational speed detectors 230, 240, 330 and 340 attached to end portions of the wheel sets 202, 204, 302 and 304 also rotate. As the pulse generation gears 232, 242, 332 and 342 rotate, the teeth of the pulse generation gears 232, 242, 332 and 342 also rotate. As the teeth of the pulse generation gears 232, 242, 332 and 342 rotate, the prosmity switches 234, 244, 334 and 344 installed near the teeth generate pulse signals. The first to fourth F/V converters 410, 420, 430 and 440 receive and convert the pulse signals into analog voltage signals. The A/D converter 460 receives and converts the analog voltage signals into digital pulse signals, which are input to the controller 540 (S620). On the other hand, the air pressure meter 400 measures air pressure in the cylinder, and the signal amplifier 450 amplifies and provides the air pressure measurement signal to the A/D converter 460. The A/D converter 460 converts the air pressure measurement signal into a digital air pressure measurement signal, which is input to the controller 540 (S620).

[77] Using the application program stored in the memory, the controller 540 calculates the rotational speeds of the wheel sets 202, 204, 302 and 304 and the air pressure in the cylinder based on the digital pulse signals and the digital air pressure measurement signal received from the A/D converter 460 (S630).

[78] The controller 540 then determines whether or not the test wheel truck 200 slips in the following manner (S640). First, the controller 540 sets the largest of the four rotational speeds of the wheel sets 202, 204, 302 and 304 as a reference rotational speed. The controller 540 determines whether or not the difference between the rotational speed of the front or rear wheel set 202 or 204 of the test wheel truck 200 and the reference rotational speed is less than an acceptable limit. If the difference between the rotational speed of the front or rear wheel set 202 or 204 and the reference rotational speed exceeds the acceptable limit, the controller 540 assumes that the test wheel truck 200 is slipping, and detects a change in the air pressure in the cylinder to determine whether or not the anti-skid control is activated, thereby deteπriining whether or not the test wheel truck 200 has occurred (S640).

[79] The controller 540 graphically displays the rotational speed of the front or rear wheel set 202 or 204 of the test wheel truck 200 and the brake airpressure change on the display 550, thereby allowing the user to determine whether or not the test wheel truck 200 is slipping (S650).

[80] The calculated rotational speed data of the front or rear wheel set 202 or 204 of the test wheel truck 200 and the calculated brake air pressure data is stored in the memory 530 at a predetermined time or in response to input of a corresponding command through the key input unit 570 (S660).

[81] Figs. 5 and 6 are graphs illustrating changes in the rotational speed and the brake air pressure when the anti-skid control is normally activated, respectively. It can be seen from Figs. 5 and 6 that the brake air pressure in the cylinder 254 is lowered when the rotational speed of the front or rear wheel set 202 or 204 differs from the reference rotational speed, and the brake air pressure in the cylinder 254 changes back to the original preset value if the rotational speed of the front or rear wheel set 202 and 204 becomes equal to the reference rotational speed.

[82] However, if the anti-skid control is not normally activated so that the wheels 210a and 210b are abraded, the brake air pressure in the cylinder 254 is not changed although the rotational speed of the front or rear wheel set 202 or 204 differs from the reference rotational speed.

[83] As apparent from the above description, a wheel slip detection system for railway vehicles according to the present invention has the following features and advantages.

[84] It is possible to easily check whether or not a railway vehicle slips when a braking force is applied, simply by measuring rotational speeds of front and rear wheel sets of test and neighboring wheel trucks of the railway vehicle using rotational speed detectors provided on the front and rear wheel sets, and measuring air pressure in a brake cylinder using an air pressure meter provided on the brake cylinder.

[85] It is also possible to determine whether or not an electronic brake control unit in a railway vehicle normally activates anti-skid control based on the check as to whether or not the railway vehicle slips when a braking force is applied, so that the rails are prevented from being damaged by decreasing the speed of the railway vehicle if it is determined that the anti-skid control is not normally. [86] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Industrial Applicability

[87] The present invention relates toa wheel slip detection system for railway vehicles, and more particularly to a wheel slip detection system capable of deteπriining whether or not a railway vehicle slips, based on both the rotational speeds of wheel sets of the railway vehicle and the air pressure of a brake cylinder for applying a mechanical braking force.

[88]

Claims

[1] A wheel slip detection system of a railway vehicle, the system comprising: first and second rotational speed detectors provided on outer portions of front and rear wheel sets of a test wheel truck of the railway vehicle, respectively, the first and second rotational speed detectors producing two respective pulse signals according to rotation of the front and rear wheel sets of the test wheel truck; third and fourth rotational speed detectors provided on outer portions of front and rearwheel sets of a neighboring wheel truck of the railway vehicle adjacent to the test wheel truck, respectively, the third and fourth rotational speed detectors producing two respective pulse signals according to rotation of the front and rear wheel sets of the neighboring wheel truck; first to fourth Frequency to Voltage (F/V) converters for receiving the four pulse signals from the first to fourth rotational speed detectors and converting the received pulse signals into four analog voltage pulse signals, respectively; an air pressure meter for measuring an air pressure applied to a cylinder in a brake assembly for braking a brake disc of the front and rear wheel sets of the test wheel truck; an Analog-to-Digital (A/D) converter for receiving the four analog voltage pulse signals from the first to fourth F/V converters, converting the received analog voltage pulse signals into four digital pulse signals, receiving an analog air pressure measurement signal from the air pressure meter, and converting the received analog air pressure measurement signal into a digital air pressure measurement signal; and a data collector for receiving the four digital pulse signals and the digital air pressure measurement signal from the A/D converter, calculating four rotational speeds of the front and rear wheel sets of the test and neighboring wheel trucks based on the four digital pulse signals, setting the largest of the four rotational speeds as a reference rotational speed, determining whether or not the difference between the rotational speed of the front or rear wheel set of the test wheel truck and the reference rotational speed is less than an acceptable limit, and determining whether or not a braking force is applied to the test wheel truck, based on the digital air pressure measurement signal received from the A/D converter, thereby determining whether or not the test wheel truck slips.

[2] The system according to claim 1, wherein the data collector comprises: a power supply for supplying DC power; a power switch for turning on f the power supply; a memory for storing an operating system for initializing the system and an application program for calculating the four rotational speeds based on the four digital pulse signals and calculating the air pressure in the cylinder based on the digital air pressure measurement signal; a controller for receiving power from the power supply as the power switch is turned on, and activating the operating system and the application program stored in the memory for receiving the four digital pulse signals and the digital air pressure measurement signal from the A/D converter, calculating the four rotational speeds of the front and rear wheel sets of the test and neighboring wheel trucks based on the four digital pulse signals, setting the largest of the four rotational speeds as the reference rotational speed, determining whether or not the difference between the rotational speed of the front or rear wheel set of the test wheel truck and the reference rotational speed is less than the acceptable limit, and deteπriining whether or not a braking force is appliedto the test wheel truck, based on the digital air pressure measurement signal received from the A/ D converter, thereby deteπriining whether or not the test wheel truck slips; and a display for displaying a travel speed and a travel distance of the test wheel truck, calculated by the controller.

[3] The system according to claim 2, wherein the display includes a liquid crystal display.

[4] The system according to claim 2, wherein the data collector further comprises an interface unit for transferring the air pressure and the rotational speeds of the front and rear wheel sets of the test wheel truck, calculated by the controller, to an external device.

[5] The system according to claim 2, wherein the data collector further comprises a key input unit for inputting commands to the controller.

[6] The system according to claim 2, whereinthe controller calculates and stores the four rotational speeds and the air pressure in the memory.

[7] The system according to claim 1, wherein the first pulse detector comprises: a disc-shaped pulse generation gear provided on the front wheel set of the test wheel truck at an outer portion of the front wheel set, the gear having a number of teeth spaced at predetermined intervals so as to rotate as the front wheel set rotates; and a prosmity switch provided near the teeth to produce a pulse signal according to movement of the teeth of the front wheel set as the front wheel set rotates. [8] The system according to claim 1, further comprising a signal amplifier for amplifying a weak analog air pressure measurement signal output from the air pressure meter by a predetermined gain to produce a practically usable signal.