CH628294A5 - Method and device for detecting sliding or slipping of the wheels of two axles of a rail vehicle - Google Patents

Abstract

The device comprises electromagnetic tachometric sensors (26, 27) each mounted on an axle of a railway carriage. The tachometric signals are applied to a detector (30 to 78) which compares the angular speeds of the axles and indicates slipping or sliding when the difference in speed exceeds a preset value. The signal from the detector may be used for instigating a corrective action at the traction motors or the braking system. An auxiliary circuit detecting the acceleration of one of the axles allows the device to detect synchronous slipping of the wheels of all the axles. <IMAGE>

Description

** ATTENTION ** start of the DESC field may contain end of CLMS **.

CLAIMS 1. Method for detecting slippage or slipping of the wheels of two axles of a railway vehicle, characterized in that it consists: performing a first pulse count at a frequency proportional to the angular speed of the first axle, performing a second pulse count at a frequency proportional to the angular speed of the second axle, to reset the two counts normally as soon as one of them has reached the end of its counting, and compare the two counts at the time of reset to detect a slip or slip situation.

2. Method according to claim 1, characterized in that the end of the first count is fixed at a first predetermined value and the end of the second count at a second predetermined value greater than the first, and a slip or a slip is detected each once the second count has reached the end of its count before the first has come to the end of its own.

3. Device for implementing the method according to one of claims 1 or 2, characterized in that it comprises: two tachometric sensors associated with the two axles to provide digital signals representative of the angular speed of each axle, and a detector comprising a first counter receiving the signal from the first tachometer sensor and providing an output signal when it has received a first predetermined number of pulses, a second counter receiving the signal from the second tachometer sensor and providing a second output signal when it has received a second predetermined number of pulses greater than the first, a lockable bistable memory having a first input connected to the output of the first counter and a second input connected to the output of the second counter, the application of a signal to the first input determining a normal state of the memory which corresponds to an absence slip or slip of the axle wheels, and the application of a signal to the second input determining an abnormal state of the memory which indicates either a slip of the wheels of the second axle, or a slip of the wheels of the first, and reset circuits of the two counters when one or the other has reached its predetermined number of pulses.

4. Device according to claim 3 for a railway vehicle having at least two bogies with at least two axles each, characterized in that it comprises: a first tachometer sensor associated with a first axle carried by the first bogie to supply a digital signal representing the angular speed of the first axle, a second tachometer sensor associated with a second axle carried by the first bogie to supply a digital signal representing the angular speed of the second axle, a third tachometer sensor associated with a third axle carried by the second bogie to supply a digital signal representing the angular speed of the third axle, a fourth tachometer sensor associated with a fourth axle carried by the second bogie to supply a digital signal representing the angular speed of the fourth axle, a first detector receiving the signals from the first and fourth tachometric sensors to detect a predetermined speed difference between the first and fourth axles, a second detector receiving the signals from the second and third tachometric sensors to detect a predetermined speed difference between the second and third axles, a third detector receiving the signals from the third and first tachometric sensors to detect a predetermined speed difference between the third and first axles, a fourth detector receiving the signals from the fourth and second tachometric sensors to detect a predetermined speed difference between the fourth and second axles, a first logic circuit receiving the outputs of the first and second detectors to indicate a situation of slipping of the wheels of the second bogie or of slipping of the wheels of the first bogie, a second logic circuit receiving the outputs of the third and fourth detectors to indicate a situation of slipping of the wheels of the first bogie or of slipping of the wheels of the second bogie.

5. Device according to claim 4, characterized in that it comprises an additional circuit for detecting a simultaneous synchronous sliding of the wheels of the two bogies, said circuit comprising: a converter connected to the output of one of the tachometric sensors to provide a signal representing the deceleration of the axle and a level detector connected to the output of the converter for detecting a minimum deceleration level, the output of the level detector being connected to an input of one of the logic circuits.

6. Device according to claim 5, characterized in that the converter comprises a frequency-level conversion circuit providing an analog signal representative of the angular speed of the axle and a circuit for differentiating said analog signal providing a deceleration signal of the 'axle.

7. Device according to claim 6, characterized in that the frequency-level converter comprises a monostable delivering pulses of constant width and a circuit for integrating the output of the monostable to produce an analog signal representative of the angular speed of the axle.

8. Device according to claim 6, characterized in that the pulses delivered by the monostable are amplified before being applied to the integration circuit.

9. Device according to claim 8, characterized in that the integration circuit comprises at least one cell with resistivity.

The present invention relates to a method and a digital device for measuring and comparing the speed of rotation of two axles of a railway vehicle for detecting a slip or slippage of the wheels.

In railways, adapting the braking power to the grip of the axles is an essential factor in the safety, comfort and longevity of the equipment, both on fast suburban lines and on main lines. For power cars, it is also necessary to measure the traction force as a function of grip, because the slip causes rapid wear of the track and the wheels. In recent years, the need to optimize the braking of trains has led to studying various systems for protection against slipping and locking of the wheels when braking. To be effective, such a system must react as quickly as possible to an abnormal slowdown in the rotation of the wheels by reducing the braking force so as to quickly restore a normal situation.

A number of prior art systems use analog components and circuits for speed detection and correction of slip or slip of the axles. US Patent No. 3,867,647 describes a system of this type which works satisfactorily. However, digital or digital techniques have a number of advantages in terms of noise immunity and speed of response.

The method according to the invention is defined by claim 1 and the device for its implementation by claim 3. According to one embodiment of the method, a result is obtained after a given number of tachometric pulses, that is to say i.e. after a short time when the speed is high, after a proportionately longer time when the speed is low. One embodiment of the invention is applicable to the detection of slipping and slippage of the wheels of a powerplant equipped with two bogies with two axles.

Although there may be speed differences between the two

axles of the same bogie, braking is usually set for both axles at the same time. So, if a speed difference is detected between the axles of the same bogie, nothing happens. However, if there is a speed difference between the pairs of axles of the two bogies, The braking intensity is momentarily reduced on the axles which slip. This global regulation by bogie is due to the fact that the brake cylinder is common to the two axles on each side of the bogie. By measuring and comparing the speeds of the axles during successive time intervals, the device of the invention allows more precise detection of the slip and slippage of the wheels.

The accompanying drawings show by way of example an embodiment of the subject of the invention.

Fig. 1 is a partial perspective view of a fast multiple unit which can be equipped with the device of the invention.

Fig. 2 is a logic diagram of a slip or slip detection device.

Fig. 3 is a logic diagram of a preferred embodiment of the slip and slip detection device.

Fig. 4 is an electrical diagram of the output circuits of the device of the invention, connected to use circuits.

Fig. 5 is an electrical diagram of a circuit for using the speed signal for controlling auxiliary use circuits.

Fig. 6 is an electrical diagram of a preferred form of the frequency-level converter of the device of the invention.

Fig. 1 illustrates a fast self-propelled car of conventional design for serving suburban lines. The car 20 comprises two driving bogies 21 and 22 with two axles each rolling on a track 23. Each bogie can be equipped with one or more traction motors (not shown). Tachometric sensors 24, 25, 26 and 27 are associated with the different axles of the car to provide pulsed signals whose frequency is representative of the speed of rotation of the axle. These tachometric signals are transmitted by shielded cables to a processing unit 28 which is mounted inside the car. Fig. l only allows you to see the cable 29 which connects the sensor 24 to the unit 28, but it is obvious that the other sensors are connected to the unit 28 by similar cables. Each sensor 24-27 is mounted so as to detect variations in magnetic flux caused by the movement of the teeth of the pinion of the traction motor or of an intermediate wheel, in the case of a two-stage gearbox, or in a special housing, in the case of a gearbox with one floor. Each sensor supplies a large number of pulses per revolution of the wheel and its low level output is transmitted to the processing unit 28.

The logic diagram in fig. 2 illustrates an elementary form of differential slip detector. The signals from the tachometric sensors 26 and 27 associated with the axles of the bogie 22 are transmitted by shielded cables 29 to input circuits 30 and 32 which ensure the amplification and the shaping of the tachometric pulses.

These pulses are then applied to a differential slip detector consisting of two binary counters 34 and 36, three logic gates 48, 58 and 74, and a lockable memory 52.

The tachometric signal from the electromagnetic sensor 27 is transmitted by a line 38 to the input of a counter 34 which is preferably a conventional binary counter with six stages. An ET48 gate is connected to some of the outputs 42, 43, 44 and 46 of the counter 34 so as to detect the binary number 60. The gate 48 has a fifth input which directly receives the tachometric pulses by a line 40 not passing through the counter 34. These pulses ensure the synchronization of the operation of door 48 with the tachometric pulses of axle No 1. When the counter 34 reaches the number 60, door 48 applies an output signal to a reset door 58 and to the input for setting S of the lockable memory 52 which can be a flip-flop of type D.

In this normal state, the memory 52 excites an output line 54 to indicate the absence of differential slip. At the same time, the output of the AND gate 48 is transmitted by the gate 58 to two lines 60 and 62 which lead to the reset (reset) inputs of the two counters 34 and 36. The reset of the counter 34 makes the signal disappear. exit doors 48 and 58.

In the absence of slippage or slippage, the counter 34 associated with axle No 1 and the counter 36 associated with axle No 2 must simultaneously reach the value 60. Another AND gate 74 is connected to certain outputs stages of the counter 36 to detect the number 62. When this number is reached, the gate 74 applies a signal to the reset gate 58 and to the reset input R of the lockable memory 52. The change of state from memory 52, a differential slip signal appears on a second output line 78. In addition, the signal from gate 74 is transmitted through gate 58 to lines 60 and 62 to simultaneously reset counters 34 and 36, as for an output from gate 48. It is obvious that the numerical values 60 and 62 are not given as examples only and depend essentially on the characteristics of the application and the system.

As long as the two axles of the bogie rotate at the same speed, the counters 34 and 36 reach the number 60 at the same time and the output of the AND gate 48 maintains the memory 52 in normal state. The two counters are furthermore reset before the counter 36 has reached the value 62. On the other hand, if the axle No2 turns significantly faster than the axle No 1, the counter 36 reaches the value 62 and the gate 74 causes a change of state of memory 52 to indicate a situation of differential sliding. This differential slip can be due to a slip of the No 2 axle or to a slip of the No I axle when braking.

Such an elementary detector is however not capable of signaling the opposite situation where the axle No I rotates faster than the axle No 2. For this, it suffices to use a second detector identical to that of FIG. 2, except that the tachometric signal of the axle No 2 is applied to the counter 34 and that of the axle No 1 is applied to counter 36.

It is desirable that the same system can detect both the slip of the driving axles and the slip of the wheels when braking. Such a system can be implemented with four elementary detector circuits in the case of a four-axle car of the type described above.

Fig. 3 illustrates such a system using four detectors of the type of that of FIG. 2. The upper part of the figure schematically represents the drive train 20 whose axles are numbered from 1 to 4, the axles I and 2 forming part of the bogie B and the axles 3 and 4 forming part of the bogie A. It goes without saying that , for other equipment with different numbers of axles, the speed comparison method will require certain obvious adaptations for a specialist.

The system of fig. 3 therefore uses four elementary detectors of the type of that of FIG. 2 bearing the references 80, 85, 89 and 93.

For the detection of slippage and slippage of the various axles, the tachometric signals must be applied two by two to the different detectors. Thus, the detector 80 receives a first input 82 from the axle sensor No 1 and a second input 84 from the axle sensor No 4. The second detector 85 receives, on a first input line 86, the tachometric signal from axle No 2 and, on a second input line 88, the signal from axle No 3. Detectors 80 and 85 provide differential slip outputs on lines 98 and 100 which lead to an AND-NO gate 102.

Thus, the output of door 102 indicates a slip of the third or fourth axle, that is to say of the bogie A. The normal outputs of the detectors 80 and 85 can be used for monitoring, but are not necessary for detection of slippage or slippage.

The detectors 80 and 85 are also sensitive to a sliding of the first two axles of the bogie B during braking. Such a sliding gives rise to an output of the AND-NON gate 102. The output line 104 of the gate 102 is provided with an inverter 106 to change the polarity of the signal and controls a relay 108 which is connected to ground in 110. The relay 108 is energized in the event of slipping of the bogie A or sliding of the bogie B. As will be seen below, in the description of FIG. 4, that the excitation of the relay 108 signaling a slip or slip situation can be used by other circuits to reduce the traction force or the braking intensity on the bogie concerned.

It is also necessary to detect the slippage of the bogie B and the sliding of the bogie A. This is the role of the third and fourth detectors 89 and 93. The detector 89 receives, on a line 90, the tachometric signal from the axle No 3 and , on a line 92, the tachometric signal of the axle No 1. Under these conditions, the detector 89 provides a signal on its output line 112 when the first axle slips or when the third axle slips.

The fourth detector 93 receives, on a line 94, the tachometric signal from the axle No 4 and, on a line 96, the tachometric signal from the axle No 2. Thus, the detector 93 provides a signal on its output line 114 when the fourth axle slips or when the second axle slips. We see that the output lines 112 and 114 are connected to an AND-NO gate 116 which provides at its output 118 a signal of slippage of the bogie B or of sliding of the bogie A. The line 118 is provided with an inverter 120 which changes the polarity of the signal before applying it to a second relay 122 connected to ground at 124. Relay 122 is excited by an active output from gate 116 which represents either a slippage of bogie B, or a sliding of bogie A .We will see below that the contacts of relay 122 can be inserted in use circuits which are not part of the present invention. These circuits control the traction motors and the braking system.

The detection system of fig. 3 provides a slip / slip indication if there is a predetermined speed difference between two of the vehicle axles, but the possibility of simultaneous slip of the four axles rotating at the same speed cannot be excluded. To take this possibility into account, the system in fig. 3 includes a device for detecting the acceleration of one of the axles. If the speed variation exceeds a predetermined value, a level detector emits a slip / slip signal.

More specifically, the speed sensor signal from the axle sensor No 2 taken on line 96 of the fourth detector is applied by a line 126 to a frequency-level converter 128. The output of this converter represents the analog angular speed of the second axle which is differentiated by a circuit 130 producing an acceleration signal . The output of the differentiator 130 is applied to a level detector 132 which reacts only above a predetermined acceleration threshold. For example, the trigger threshold can be set to a value corresponding to a speed variation of 13 km / h per second, which can only result from slipping or slipping of the wheels. The signal from the detector 132 is applied to a third input of the AND gate 116 which excites the relay 122, as described above. In the case of a deceleration greater than 13 km / h per second, the excitation of the relay 122 can be used to reduce the braking intensity on the bogie A. As soon as the axles of the bogie A start to accelerate, the synchronism of the slip disappears and one of the detectors 80 or 85 provides an output exciting the relay 108. This relay can then acting on a bogie B brake reducer

Fig. 4 shows part of the system of FIG. 3, and more particularly the circuits which are associated with the AND-NON gate 102 or 116, that is to say the inverter 106 or 120 and the relay 108 or 122. To the relay are connected circuits which allow the correction slippage or slip for each of the bogies and can inhibit braking. In particular, a signal is emitted if the indication of skating or sliding lasts for a predetermined time.

In fig. 4, the AND-NON gate 102 or 116 receives the slip signals by lines 136 and 138 which represent the input lines in FIG. 3. The inverter 106, 120 includes a variable resistor 142 which determines the basic polarization of an inverter transistor 144. The collector of the transistor is connected to the coil 146 of the relay 108 or 122. The other terminal of the coil 146 is connected to one of the plates of a capacitor 148, the second plate of which is grounded.

A first set of contacts 158 of the relay controls the use circuits not forming part of the device of the invention, for example braking control circuits. These circuits need the detection signals of the device of the invention, as well as other information concerning the traction motors and the braking system to regulate their actions so as to avoid slipping and slipping. The coil 146 of the relay is energized when the transistor 144 becomes conductive. The duration of the excitation of the relay depends on the time that the capacitor 148 takes to discharge below the holding voltage of the coil. The relays 108 and 122 include a second set of contacts comprising a mobile contact 152 and fixed contacts 154 and 156. When the contact 152 touches the contact 154, it connects a source of potential + E to the resistor 150 and to the capacitor ' 148. As long as the transistor 144 is not conducting, the capacitor 148 charges at a sufficiently high potential to allow the excitation of the relay 108 or 122 - under the effect of an output pulse of the inverter 106 or 120.

Then, the capacitor 148 discharges through the coil 146, the transistor 144 and the emitter resistance 160 until the point 151 is at a too low potential to maintain the excitation of the coil 146.

It may be desirable to use the system described to indicate that the train is stopped or running at very low speed, this indication being useful for controlling an automatic door locking system. To provide this additional function, the output of the frequency-level converter 128 (fig. 3) -is applied by a line 162 to the auxiliary circuit of fig. 5. The analog speed signal from converter 128 is applied to a threshold detector 164 which is associated with a variable resistor 166 making it possible to set a very low threshold, for example 3 km / h. The output of the detector 164 is amplified by a transistor 168-before being applied to the coil 172 of a relay 169. The other terminal of the coil 172 is connected by a line 170 to a source of potential + E ensuring the bias of the transistor. When the coil 172 is energized, the relay 169 changes state and closes a contact signaling that the train is moving at very low speed: This contact can be inserted in auxiliary use circuits which are not part of the device of the invention.

Fig. 6 schematically represents the frequency-level converter circuit 128 which has been mentioned with reference to FIGS. 3 and 5.

The amplified and shaped pulses of the tachometric sensor are applied to the input line 126. These pulses trigger a monostable 174 which can be a Texas integrated circuit. Instruments type SN 74121N requiring a supply voltage of + si. The output of the monostable is a train of pulses of constant width corresponding to each pulse of the line 126.

This pulse train is applied to a first transistor 178 through an input resistor 176. The collector of transistor 178 is connected to the base of a second transistor 180 through a variable resistor. The bias potential of transistors 178 and 180 is much higher than that of monostable 174, for example -18 V.

Thus, the two transistors 178 and 180 substantially amplify the train of pulses supplied by the monostable 174. The amplified output of transistor 180 appears at its emitter at point 182 from where it is applied to an RC filter made up of resistors 184, 188 and capacitors 186, 190. The role of these two RC stages is to integrate the pulse train supplied by the transistors 178, 180 to convert it into a DC voltage level proportional to the number of pulses received by the monostable 174. From a physical point of view, the number of pulses received by lemonostable 174 corresponds to the speed of the train and the continuous level appearing on the output line 192 is therefore representative of this speed. It is obvious that the circuit of fig. 6 is only one example of a frequency-level converter usable in the device of the invention.

In conclusion, the device of the present invention makes it possible to precisely detect the slippage or the slipping of the wheels of a railway vehicle with a sensitivity all the greater as the speed increases, owing to the fact that the frequency of the tachometric pulses increases proportionally . This increased sensitivity to high speeds is particularly interesting in modern cars for fast trains. The device of the invention applies without difficulty to motor cars and makes it possible to optimize braking and traction power so as to avoid slipping and slipping of the wheels. With auxiliary circuits, the same device makes it possible to control various functions such as locking the doors above a certain speed.

Claims (9)

1. Method for detecting slippage or slipping of the wheels of two axles of a railway vehicle, characterized in that it consists: performing a first pulse count at a frequency proportional to the angular speed of the first axle, performing a second pulse count at a frequency proportional to the angular speed of the second axle, to reset the two counts normally as soon as one of them has reached the end of its counting, and compare the two counts at the time of reset to detect a slip or slip situation. 2. Method according to claim 1, characterized in that the end of the first count is fixed at a first predetermined value and the end of the second count at a second predetermined value greater than the first, and a slip or a slip is detected each once the second count has reached the end of its count before the first has come to the end of its own. 3. Device for implementing the method according to one of claims 1 or 2, characterized in that it comprises: two tachometric sensors associated with the two axles to provide digital signals representative of the angular speed of each axle, and a detector comprising a first counter receiving the signal from the first tachometer sensor and providing an output signal when it has received a first predetermined number of pulses, a second counter receiving the signal from the second tachometer sensor and providing a second output signal when it has received a second predetermined number of pulses greater than the first, a lockable bistable memory having a first input connected to the output of the first counter and a second input connected to the output of the second counter, the application of a signal to the first input determining a normal state of the memory which corresponds to an absence slip or slip of the axle wheels, and the application of a signal to the second input determining an abnormal state of the memory which indicates either a slip of the wheels of the second axle, or a slip of the wheels of the first, and reset circuits of the two counters when one or the other has reached its predetermined number of pulses. 4. Device according to claim 3 for a railway vehicle having at least two bogies with at least two axles each, characterized in that it comprises: a first tachometer sensor associated with a first axle carried by the first bogie to supply a digital signal representing the angular speed of the first axle, a second tachometer sensor associated with a second axle carried by the first bogie to supply a digital signal representing the angular speed of the second axle, a third tachometer sensor associated with a third axle carried by the second bogie to supply a digital signal representing the angular speed of the third axle, a fourth tachometer sensor associated with a fourth axle carried by the second bogie to supply a digital signal representing the angular speed of the fourth axle, a first detector receiving the signals from the first and fourth tachometric sensors to detect a predetermined speed difference between the first and fourth axles, a second detector receiving the signals from the second and third tachometric sensors to detect a predetermined speed difference between the second and third axles, a third detector receiving the signals from the third and first tachometric sensors to detect a predetermined speed difference between the third and first axles, a fourth detector receiving the signals from the fourth and second tachometric sensors to detect a predetermined speed difference between the fourth and second axles, a first logic circuit receiving the outputs of the first and second detectors to indicate a situation of slipping of the wheels of the second bogie or of slipping of the wheels of the first bogie, a second logic circuit receiving the outputs of the third and fourth detectors to indicate a situation of slipping of the wheels of the first bogie or of slipping of the wheels of the second bogie. 5. Device according to claim 4, characterized in that it comprises an additional circuit for detecting a simultaneous synchronous sliding of the wheels of the two bogies, said circuit comprising: a converter connected to the output of one of the tachometric sensors to provide a signal representing the deceleration of the axle and a level detector connected to the output of the converter for detecting a minimum deceleration level, the output of the level detector being connected to an input of one of the logic circuits. 6. Device according to claim 5, characterized in that the converter comprises a frequency-level conversion circuit providing an analog signal representative of the angular speed of the axle and a circuit for differentiating said analog signal providing a deceleration signal of the 'axle. 7. Device according to claim 6, characterized in that the frequency-level converter comprises a monostable delivering pulses of constant width and a circuit for integrating the output of the monostable to produce an analog signal representative of the angular speed of the axle. 8. Device according to claim 6, characterized in that the pulses delivered by the monostable are amplified before being applied to the integration circuit. 9. Device according to claim 8, characterized in that the integration circuit comprises at least one cell with resistivity. The present invention relates to a method and a digital device for measuring and comparing the speed of rotation of two axles of a railway vehicle for detecting a slip or slippage of the wheels. In railways, adapting the braking power to the grip of the axles is an essential factor in the safety, comfort and longevity of the equipment, both on fast suburban lines and on main lines. For power cars, it is also necessary to measure the traction force as a function of grip, because the slip causes rapid wear of the track and the wheels. In recent years, the need to optimize the braking of trains has led to studying various systems for protection against slipping and locking of the wheels when braking. To be effective, such a system must react as quickly as possible to an abnormal slowdown in the rotation of the wheels by reducing the braking force so as to quickly restore a normal situation. A number of prior art systems use analog components and circuits for speed detection and correction of slip or slip of the axles. US Patent No. 3,867,647 describes a system of this type which works satisfactorily. However, digital or digital techniques have a number of advantages in terms of noise immunity and speed of response. The method according to the invention is defined by claim 1 and the device for its implementation by claim 3. According to one embodiment of the method, a result is obtained after a given number of tachometric pulses, that is to say i.e. after a short time when the speed is high, after a proportionately longer time when the speed is low. One embodiment of the invention is applicable to the detection of slipping and slippage of the wheels of a powerplant equipped with two bogies with two axles. ** ATTENTION ** end of the CLMS field may contain start of DESC **.