SYSTEM FOR CONTROLLING THE AUTOMATIC BRAKES OF A RAILWAY VEHICLE, BY MEANS OF ELECTRICAL SIGNAL TRANSMISSION

Abstract: A system for controlling the automatic brake of a railway vehicle includes a main pneumatic line (P), a general pneumatic line (G), and a self-regulating device for controlling the supply and discharge of the general line through a control lever (13). The device includes a relay valve (8) and solenoid valves (4,5,7), and pressure transducers (9,10) connected to an electronic unit (11) which controls the functions of the device by comparing electrical reference signals corresponding to the various positions of the control lever with comparison signals from the pressure transducers. Luminous indicators (22) are provided which are connected to the electronic control unit for signalling the pressure drops in the general pneumatic line in normal running conditions, during brake release, and during checks in conditions of isolation.

Description: The subject of the present invention is a system for controlling the automatic brake of a railway vehicle, particularly a locomotive, including a main pneumatic line for supplying compressed air from a source, a general pneumatic line connected to a distributor, and a self-regulating device including a series of actuators for controlling the supply and discharge of the general line through a control lever arranged to assume a series of different positions which correspond to the different functions of the device and each of which has a corresponding electrical reference signal. More particularly, the invention relates to a control system of the type defined in the main claim of Italian patent application No. 67282-A/85 in the name of the same Applicant. This system comprises, in brief, a circuit having the first inlet connected to the main line and a second inlet connected to the general line, and incorporates: a relay valve which controls communication between the two inlets and whose operating chamber is connected to the main line through a solenoid supply valve, a first pressure transducer associated with the relay valve, a first solenoid discharge valve for reducing the pressure in the general line through the relay valve, a second solenoid discharge valve which controls communication between the operating chamber of the relay valve and a discharge, a normally-open, on-off solenoid valve which controls communication between the main line and the relay valve, a second pressure transducer sensitive to the pressure drop in the general line, and an electronic control unit to which are sent the electrical reference signals corresponding to the different positions of the control lever, as well as electrical signals provided by the first and second pressure transducers for comparison with these electrical reference signals. This control unit is connected to the solenoid valves and is arranged to carry out, in the manner made clear in the above-mentioned Italian Application No. 67282-A/85, the functions of supply and discharge, of boosting and of discharging overloads in the general line, of small-magnitude brake releases, and of discrimination between the initial loading conditions, of leakages in the general line, and of operation of the alarm signal when the control lever is in the positions corresponding to the functions of running and overloading and of braking. The present invention constitutes an improvement of the system according to the application 67282-A/85 and, in particular, has the object of increasing the operating capacity, while improving the operational efficiency. According to the invention, this object is achieved by virtue of the fact that the second pressure transducer is connected directly to the general line, and that it further includes luminous indicator means operatively connected to the electronic control unit of the device and arranged to be activated thereby to provide an indication when the transducer detects pressure drops in the general pneumatic line which do not correspond to that required in the positions of the control lever relating either to the functions of running and overload and of braking, or to the function of brake release, as well as that of isolation for checking of any leakages in the general line. By virtue of this concept, an appreciable extension of the operating capacity of the system is obtained, together with more complete control of the operation of the braking circuit. On the one hand, this is made possible by virtue of the manner of the connection between the second transducer and the general line, which is direct according to the invention but was effected near the relay valve in the version according to application 67282-A/85, with consequent delays and the impossibility, in practice, of detecting leakage in the general line during brake release. On the other hand, the presence of luminous indicator means enables indications relating to any leakages in the general line to be provided clearly and immediately. According to another aspect of the invention, the electronic control unit is arranged, when the control lever is placed in the brake-release position, to send to the operating chamber of the relay valve by means of the solenoid supply valve an overpressure proportional to the pressure difference established by the lever between the pressure in the operating chamber and the pressure in the general line, the electronic unit being arranged to limit the maximum value of the overpressure and to reduce its magnitude progressively and automatically until the forces acting on the diaphragms of the relay valve are in equilibrium; the differential established is such as to ensure the maximum supply to the general pneumatic line without causing simultaneous boosting relative to the value established by the control lever. In the case of railway vehicles provided with electropneumatic braking circuits including electropneumatic valve units these may, to advantage, be controlled directly by the electronic control unit by means of the electrical signals sent thereto by the first pressure transducer. The invention will now be described with reference to the appended drawing, provided purely by way of non-limiting example, which shows a diagram of the system for controlling the automatic brake of a railway vehicle according to the invention. This diagram shows, in effect, a part of an automatic brake control system installed in a locomotive provided with two identical driving cabs. The system comprises essentially a main line P for supplying compressed air and connected to a braking pipe, a general line G connected to a distributor of known type and not illustrated, and a self-regulating device including a ducted plate R which also functions as a support and is provided with connectors for the connection of the lines and two control units C₁, C₂ situated in the driving cabs of the vehicle. The ducted plate R has a first inlet connected to the main line P through a normally-open isolation valve 1, and is connected at 2 to the general line G through the two control units C₁, C₂. Communication between the valve 1 and the inlet 2 is controlled through a relay valve 8 whose operating chamber is connected to the main line P through a line in which a solenoid supply valve 3 is inserted. The operating chamber of the relay valve 8 is also connected to a solenoid discharge valve 4 and to a solenoid discharge valve 5 through an isolating valve unit 15. The unit 15 is normally arranged in such a position as to keep communication open between the relay valve 8 and the solenoid valve 5. Communication between the inlet of the relay valve 8 and the main line P is controlled by means of an on-off solenoid valve 7 which is illustrated in the de-energised condition in the diagram, as are the solenoid valves 3, 4 and 5. The inlet of the relay valve 8 is also connected to the main line P through a by-pass circuit 21 of reduced section arranged in parallel with the solenoid on-off valve 7. Two transducers are indicated 9 and 10, of which the first, in accordance with one aspect of the invention, is connected directly to the general line G and the other is connected to the operating chamber of the relay valve 8. The two transducers 9 and 10 are arranged to send electrical signals indicative of the pressures detected to an electronic control unit 11 which controls the solenoid valves 3 and 4 in response to control signals from the two units C₁ and C₂ and the solenoid valve 7 in response to the signals from the transducer 9. Each of the control units C₁, C₂ includes a control lever arranged to assume a series of different positions which correspond to the different functions of the system, which will be described below, and each of which has a corresponding electrical reference signal generated, for example, by a potentiometer, not illustrated, associated with the lever. This signal is sent to the electronic control unit 11. The control units C₁, C₂ further include two mechanically operated valves 16, 17 for cutting off the general line G and have the respective functions of isolation and rapid discharge of this line. According to another aspect of the invention, a luminous indicator 22 is associated with each control unit C₁, C₂ and is connected to the electronic control unit 11 for activation thereby in the manner specified below. The circuit also includes a device, generally indicated 6, for repetition of the signals in the locomotive, which is integrated in the system and comprises a double-solenoid valve 18 with bistable control connected on one side to the operating chamber of the relay valve and on the other side to a discharge solenoid valve 19 and a pressure switch 20 whose function is to switch the bistable solenoid valve 18 to connect or disconnect the repetition device. The valve unit 15 connects the circuit R to two four-way isolating valves 12 (one for each cab) to activate or de-activate respective controls of the direct brake 16 through a direct brake line F. Finally, two emergency devices are indicated 14, one for each cab, which are normally isolated from the circuit R by the valve unit 15. The device described above is of the self-regulating type and is provided with control logic based on the comparison carried out by the electronic unit 11 between the reference signals corresponding to the various positions of one or other of the levers 13 and the response signals coming from the pressure transducers 10 and 9. The electronic unit 11 provides for the control of the operation of the various solenoid valves of the valve whose function is, in practice, that of piloting the high-capacity and highly sensitive relay valve 8 which is required to carry out the supply and discharge of the general line G. The various functions carried out by the system in correspondence with the various positions assumed by one or other of the control levers 13 are described in detail in the Italian patent application No. 67282-A/85, already cited, which may be referred to for brevity. Only additional or alternative functions obtained by means of the present invention will be described below. In particular, the functions of isolation, boosting, running, initial gradual braking, full braking and gradual maximum braking, rapid braking, as well as the particular functions of protection against partial overloads and incorrect operation, automatic closure of the shoes and automaticemergency braking are achieved identically to those described in the aforesaid application No. 67282-A/85. As far as the function of "gradual brake release" is concerned, which is obtained by moving the control lever 13 from any braking position into the "running" position, as described in application No. 67282-A/85, the reference signal generated by the execution of this movement is compared by the electronic unit 11 with that provided by the transducer 10. The initial disparity causes energisation of the solenoid valve 3 which supplies the operating chamber of the relay 8, causing the general line to be recharged to the value set by means of the control lever 13. In order to obtain appreciable reductions in the brake-release time, the electronic control unit 11 is arranged in such a way that the chamber of the relay 8 receives, through the solenoid supply valve 3, an overpressure proportional to the difference in pressure established by the control lever 13 between the pressure in the operating chamber 8 and the pressure in the general line G. The electronic unit 11 is arranged to limit the maximum value of this overpressure, as well as automatically to reduce its magnitude progressively as it gradually approaches the preset threshold. Furthermore, the timing achieved by the electronic unit 11 in the case of large brake releases, by means of the control circuit described with reference to Figure 3 of the application No. 672872-A/85, is arranged to achieve a set time of about 30 seconds in the case of brake releases with a rise in the general line of 3.3 bars to 4.5 bars. The luminous indicators 22, which remain de-activated during the initial gradual braking stage, are lit during the "initial loading" stage due to the drop in pressure detected by the transducer 9 within the general line G when the main valve of the locomotive is opened. The indicators 22 are subsequently switched off when the differential established between the reference value and that of the pressure in the general line, detected by the transducer 9, is cancelled out. If the alarm signal is operated in the "running" and "overload" positions, the change in slope of the discharge curve of the general line G, detected by the pressure transducer 9, causes the luminous indicators 22 to be lit. An identical situation occurs if the alarm signal is operated with the control lever 13 in the braking sector. In fact, in this case, the operation of the alarm signal creates a discrepancy between the value corresponding to the position of the control lever 13 and that detected in the general line by the transducer 9, which causes the electronic unit 11 to activate the indicators 22. It should be stated that, when the emergency signal is operated during braking since the time described above with reference to gradual braking has elapsed, the electronic control unit 11 causes the luminous indicators 22 to be lit and braking must be carried out by the driver. The presence of the luminous indicators 22 further enables an indication to be obtained of any leakages in the general line during the checking stages, when trains are being formed, with the control levers 13 in the "isolation" position. In fact, when both the levers 13 are in the isolation position, the electronic unit 11 memorises the signal provided by the transducer 9, corresponding to the pressure value present in the general line. A simple electronic device, not described but within the capability of an expert in the art, causes this signal to be subtracted according to a predetermined slope. A discrepancy between the signal set and that provided by the transducer 9 causes the luminous indicators 22 to be lit. This function, which can be adjusted according to the requirements of use, is automatically excluded when one of the control levers 13 is moved from the isolation position. A further extension of the operating capacity of the present system relative to that described in application No. 67282-A/85 concerns the use of the electronic control unit 11 for controlling the electropneumatic braking circuit of the vehicle. In fact, it is possible to provide for the direct control of the electropneumatic circuit, through one or more electrical lines 23 connectible to the unit 11, by means of the electrical signals supplied to this electronic unit 11 by the first pressure transducer 10. To advantage, this direct control enables the use of additional control members for piloting the supply and discharge of the solenoid valves to be avoided.

Claims: 1. A system for controlling the automatic brake of a railway vehicle by means of electrical signal transmission, of the type including a main pneumatic line for the supply of compressed air from a source, a general pneumatic line connected to a distributor, and a self-regulating device including a series of actuators for controlling the supply and discharge of the general line through a control lever arranged to assume a series of different positions which correspond to the different functions of the device and each of which has a corresponding electrical reference signal, in which the self-regulating device comprises a circuit (R) having a first inlet (1) connected to the main line (P) and a second inlet (2) connected to the general line (G), and incorporates: a relay valve (8) which controls communication between the two inlets (1, 2) and whose operating chamber is connected to the main line through a solenoid supply valve (3), a first pressure transducer (10) associated with the relay valve (8), a first discharge solenoid valve (4) for reducing the pressure in the general line (G) through the relay valve (8), a second discharge solenoid valve (5) which controls communication between the operating chamber of the relay valve (8) and a discharge, a normally-open, on-off solenoid valve (7) which controls communication between the main line (P) and the relay valve (8), a second pressure transducer (9) which is sensitive to the pressure drop in the general line (G), an electronic control unit (11) to which are sent the electrical reference signals corresponding to the different positions of the control lever, as well as the electrical signals provided by the first and second pressure transducers for comparison with these electrical reference signals, the control unit (11) being connected to the solenoid valve (3, 4, 5, 7) and being arranged to carry out operations of supply and discharge, of boosting and of discharging overloads in the general line, of small-magnitude brake releases, and of discrimination between the initial loading conditions, of leakages in the general line and of alarms when the control lever is in the positions corresponding to the functions of running and overload, as well as of braking, characterised in that the second pressure transducer (9) of the self-regulating device (R) is directly connected to the general line (G), and in that it further includes luminous indicator means (22) operatively connected to the electronic control unit (11) of the device and arranged to be activated thereby to provide an indication when the transducer (9) detects pressure drops in the general pneumatic line (G) which do not conform to the positions of the control lever (13) corresponding either to the functions of running and overload as well as of braking, or to the brake-release function, or to isolation for checking of any leakages in the general line (G). 2. A system according to Claim 1, characterised in that the electronic control unit (11) is arranged, when the control lever (13) is set in the brake-release position, to send to the operating chamber of the relay valve (8) by means of the solenoid supply valve (3) an overpressure proportional to the pressure difference established by the control lever (13) between the pressure in the operating chamber of the relay valve (8) and the pressure in the general line (G), the electronic unit (11) being arranged to limit the maximum value of the overpressure and automatically to reduce its magnitude progressively to the set value of the pressure difference. 3. A system according to Claim 1 or Claim 2, which can be applied to railway vehicles provided with an electropneumatic braking circuit including electropneumatic valve units, characterised in that the electropneumatic valve means are controlled directly by the electronic control unit (11) by means of the electrical signals sent thereto by the first pressure transducer (10) of the device.

Inventors: BORTOT, RENATO, CASADEI, RENATO, RESTORI, ETTORE, SISTO, UGO WABCO WESTINGHOUSE COMPAGNIA FRENI SPA
Applicants: WABCO WESTINGHOUSE COMPAGNIA FRENI S.P.A.
Application year: 1988
Main classification: B60T13
IPC codes: B60T13