Fuel injector and fuel injection system

A fuel injection system intended for use in a multi-cylinder internal combustion engine for supplying each of the cylinders with fuel under a high pressure, comprising:

• a fuel injection pump for discharging a predetermined amount of fuel,
• a plurality of fuel injectors one of which is provided at each corresponding cylinder to retain under a high pressure fuel supplied from said fuel injection pump and to inject the high pressure fuel, each fuel injector comprising:
• a fuel pressure control chamber and an accumulator, which temporarily retains fuel, and a path leading into the fuel pressure control chamber and accumulator to which fuel is fed intermittently under pressure from a fuel source, comprising;
• a housing having formed therein a nozzle hole to inject fuel out of the accumulator;
• a piezo actuator accommodated in said housing, defining said fuel pressure control chamber and expanding and contracting in accordance with a voltage applied thereto, thereby changing the volume of said fuel pressure control chamber;
• a needle valve, of a type which opens and closes responsive to an applied pressure provided reciprocally movably within said housing and which, receiving pressure from said fuel pressure control chamber and accumulator, opens or blocks communication between said accumulator and said nozzle hole;
• and
• check valve means for normally closing communication between said path and said fuel pressure control chamber and between said path and said accumulator and for opening communication according to pressure in said path and/or in said fuel pressure control chamber;
• the arrangement being such that fuel supplied from said fuel source passes through said path and is fed under pressure into said fuel pressure control chamber and accumulator via said check valve;
• said needle valve blocking communication between said accumulator and nozzle hole when said piezo actuator expands to increase fuel pressure within said fuel pressure control chamber, and opening communication between said accumulator and said nozzle hole when said piezo actuator contracts to decrease the fuel pressure in said fuel pressure control chamber
• thereby allowing fuel to be injected from
• said nozzle hole;
• a fuel pipe-line divided at a half-way point thereof into a number of branches corresponding to the number of cylinders of the internal combustion engine, having one end thereof connected to the discharge port of said fuel injection pump and each branched end thereof connected to each fuel injector,
• means of pressure control, provided at the half-way point of said fuel pipe-line to increase/decrease fuel pressure in the fuel pipe line, and
• means of opening each said fuel injector to inject high pressure fuel.