Patent ID: 8215287

Claim:
A fuel supply apparatus for an engine comprising: a plurality of common rails that stores fuel under relatively different pressures; and at least an injector that is connected to the common rails to be independently supplied with the fuel and selectively inject the fuel in any one of the connected common rails; wherein the common rails include a high pressure common rail connected to a pressure pump and a low pressure common rail connected to the high pressure common rail through a passage; wherein a high pressure control valve is disposed in the passage and controllable; wherein a low pressure control valve is disposed in a return passage connecting the low pressure common rail to a fuel tank and controllable; and wherein the injectors are connected to the high pressure common rail and the low pressure common rail to be supplied with the fuel; wherein the injector includes: a housing; a high pressure port formed in the housing and connected with the high pressure common rail; a low pressure port connected to the low pressure common rail; a spill port returning the fuel to the fuel tank through the spill passage; and a valve member received in the housing and controlling communication between the low pressure port and an injection nozzle, communication between the high pressure port and the injection nozzle, and communication between the injection nozzle and the spill port, wherein the valve member includes: a low pressure spool slidable in the housing and having a first low pressure channel that is formed to selectively communicate the low pressure port with the spill port and a second low pressure channel that is formed to communicate the first low pressure channel with the injection nozzle; a high pressure spool slidable in the housing and having a first high pressure channel that is formed to selectively communicate the high pressure port with the spill port and a second high pressure channel to selectively communicate from the first high pressure channel toward the injection nozzle; a first actuator controlling a sliding motion of the low pressure spool in the housing; a second actuator controlling a sliding motion of the high pressure spool in the housing; an intermediate spool of which one end is configured to selectively contact with the low pressure spool to close the second low pressure channel, and of which the other end is engaged with the high pressure spool, the intermediate spool having a constant-communicated channel at the other end thereof to selectively communicate from the second high pressure channel toward the injection nozzle according to the sliding motion of the high pressure spool; a first elastic member that is disposed between the first actuator and the low pressure spool; and a second elastic member that is disposed between the second actuator and the high pressure spool.