| 摘要 |
An EOT unit on a railcar is equipped with a microprocessor controlled regulating valve system to control pressure within the brake pipe. The system includes a microprocessor unit, a pressure transducer, a regulating valve device and an electropneumatic control mechanism. The microprocessor receives from the transducer an electrical signal indicative of actual brake pipe pressure and from the locomotive a brake command signal indicative of desired brake pipe pressure. The microprocessor issues electrical control signals to the mechanism when the brake command signal requires either a service brake application or an emergency brake application. The regulating valve device defines a primary passage, a branch passage, an exhaust passage, and an elongated valve bore in which a diaphragm operated piston is located above an elongated valve stem. The valve stem features two valves with the first located between the primary and exhaust passages and the second between the exhaust and branch passages. The primary and branch passages communicate with the brake pipe, and all of the passages communicate with the bore. Responsive to a control pressure provided by the mechanism to a volume above the diaphragm, the piston moves the valve stem within the bore to the extent dictated by that control pressure. For a service control pressure, the piston opens only the first valve to the extent dictated by that service control pressure. For an emergency control pressure, the piston fully opens the first and second valves to reduce the pressure in the brake pipe at an emergency rate. |
