Injector having structure for controlling nozzle needle

An injector comprising:

• an elongated base body;
• an injection hole, which penetrates through a wall of the base body to inject fuel;
• a nozzle chamber, which is directly communicated with the injection hole on an upstream side of the injection hole in the base body and is supplied with pressurized fuel;
• a nozzle needle, which is located in the nozzle chamber and is driven to enable and disable injection of the fuel through the injection hole;
• a nozzle needle back pressure chamber, which is formed adjacent to a base end of the nozzle needle in the base body and is supplied with pressurized fuel to exert a back pressure of the nozzle needle for urging the nozzle needle toward the injection hole;
• a release passage, which is formed in the base body to release the pressure of the nozzle needle back pressure chamber to an external low pressure source;
• a control valve chamber, which is located in an intermediate part of the release passage in the base body;
• a first control valve, which is located in the control valve chamber and is driven to connect and disconnect between the nozzle needle back pressure chamber and the low pressure source;
• and
• a valve drive means for driving the first control valve, wherein the valve drive means is a hydraulic valve drive means that includes:
• a hydraulic pressure passage, which is formed in the base body, such that the hydraulic pressure passage is supplied with pressurized fuel and applies the pressurized fuel to the first control valve as control hydraulic fluid for driving the first control valve;
• a second control valve, which is driven to control a flow of the fuel in the hydraulic pressure passage;
• and
• an actuator, which drives the second control valve.