Electro-pneumatic brake system |
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| 申请号 | US3734571D | 申请日 | 1972-01-25 | 公开(公告)号 | US3734571A | 公开(公告)日 | 1973-05-22 |
| 申请人 | WESTINGHOUSE AIR BRAKE CO; | 发明人 | COCCIA R; | ||||
| 摘要 | Digital application and release brake control signals generated by an electronic operating unit in accordance with the difference between a desired retardation signal and the available dynamic brake effort are provided to control a pair of thyristors in an a.c. control circuit for energizing one or the other of separate field windings of a torque motor, the output shaft of which drives a pneumatic relay valve device between application, lap and release positions, accordingly. The output of the relay valve provides friction brake effort sufficient to compensate for the inability of the dynamic brake to satisfy the desired level of ratardation called for. A pneumatic means of controlling the relay valve device independent of the torque motor is available to assure friction braking in the event the torque motor drive fails. | ||||||
| 权利要求 | 1. A brake control system for a railway vehicle having brake units for producing friction brake effort on said vehicle and an electronic brake control unit to which a brake command signal is applied, said command signal being compared with a feedback signal representative of the degree of dynamic brake effort effective on said vehicle to provide an error signal, in accordance with which error signal friction brake application and release control signals are derived, wherein the improvement comprises the combination of: a. relay valve means operable from a lap position to an application position in which fluid pressure communication is established between a source of fluid pressure and said brake units and to a release position in which fluid pressure communication is established between said brake units and atmosphere, b. a torque motor for driving said relay valve means, said torque motor including a pair of opposing field windings energization of a respective one of which effects operation of said motor to drive said relay valve means to said application or said release position, and c. a torque motor control circuit including: i. a source of electrical energy, ii. said pair of torque motor field windings, and iii. switch means operative responsive to said application and release control signals for controlling current flow between said source of electrical energy and one or the other of said field windings. 2. A brake control system, as recited in claim 1, wherein said source of electrical energy comprises transformer means for coupling an a.c. input signal from a primary winding to a pair of secondary windings thereof, each of said secondary windings being connected in series with a separate one of said pair of field windings. 3. A brake control system, as recited in claim 2, wherein said torque motor control circuit further comprises: a. said switch means comprising first and second thyristors each having a respective one of said application and release control signals connected to a gate input thereof to control conduction of said thyristors, and b. rectifier means associated with each of said secondary windings for supplying to said thyristors a d.c. signal the amplitude of which periodically establishes a reverse biased condition thereat in accordance with the polarity transition of said a.c. signal to provide for terminating current flow to one or the other of said field windings via the conducting one of said thyristors following loss of said application or release control signal at the gate input of the conducting thyristor. 4. A brake control system, as recited in claim 1, further including means for providing a feedback signal to said electronic control unit representative of friction brake effort on said vehicle for modifying said error signal accordingly. 5. A brake control system, as recited in claim 1, wherein said relay valve means comprises: a. an actuating valve assembly having means for connecting the output shaft of said torque motor to said valve assembly to effect actuation thereof in opposite directions from said lap positions to said application and release positions in accordance with energization of one or the other of said pair of field windings, b. spring means for constraining said valve assembly in said lap position in the absence of an actuating force thereon, and c. a poppet valve element arranged in cooperative relationship with a first annular valve seat formed at the end of a stem of said actuating valve assembly to control fluid pressure communication between said brake units and atmosphere and a second annular valve seat formed concentric with said first valve seat by the bore in which said stem operates to thereby control fluid pressure communication between said brake units and said source of fluid pressure. 6. A brake control system, as recited in claim 5, further comprising: a. said actuating valve assembly including a differential piston abutment having formed on opposite sides thereof a control chamber subject to a fluid pressure control signal and a balancing chamber subject to fluid pressure effective at said brake units, said actuating valve assembly being operable between said application and release positions in accordance with the pressure differential across said piston abutment; and b. means for normally establishing fluid pressure equalization between said control chamber and said balancing chamber to prevent actuation of said valve assembly by said differential piston abutment and for interrupting fluid pressure equalization between said control chamber and said balancing chamber in response to application of said fluid pressure control signal to provide actuation of said valve assembly by said differential piston abutment. 7. A brake control system, as recited in claim 6, wherein said means for connecting the output shaft of said torque motor to said valve assembly includes said spring means. 8. A brake control system, as recited in claim 6, wherein said means for connecting the output shaft of said torque motor to said valve assembly comprises: a. a spring seat member engageable with the torque motor output shaft for axial displacement in accordance with opposite directions of rotation of said output shaft, and b. said spring means including: i. a first spring acting on said piston abutment to urge said valve assembly to said release position, ii. a second spring disposed between said piston abutment and said spring seat member to urge said valve assembly to said application position in opposition to said first spring, and iii. a third spring acting on said spring seat member in opposition to said second spring to maintain said first and said second springs in a state of compression in the absence of an actuating force on said piston assembly. |
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