Patent ID: 7891338

Claim:
A regulating device for a regulating pressure/flow in a fuel injection system of an internal combustion engine, wherein a common rail ( 6 ) of pressurized fuel is supplied by a high-pressure pump ( 7 ) along a delivery pipe ( 8 ), said high-pressure pump ( 7 ) having an intake valve ( 25 ) in communication with a low-pressure pump ( 9 ) and a delivery valve ( 30 ) in communication with said delivery pipe ( 8 ), said high-pressure pump ( 7 ) being operated in synchronism with a motor shaft ( 4 ), and wherein the required fuel pressure of the common rail ( 6 ) is defined by an electronic control unit ( 16 ) as a function of the operating conditions of the engine ( 2 ), said regulating device comprising: a solenoid bypass valve ( 14 ) controlled by said control unit ( 16 ) to drain into a tank ( 11 ) the surplus fuel pumped by said high-pressure pump ( 7 ), said solenoid bypass valve ( 14 ) being fitted to said delivery pipe ( 8 ) downstream of said delivery valve ( 30 ); and valve means ( 31 ) provided between said bypass solenoid valve ( 14 ) and said common rail ( 6 ), said valve means ( 31 ) comprising a first non-return valve ( 32 ) to permit fuel flow from said high-pressure pump ( 7 ) to said common rail ( 6 ) as long as the actual fuel pressure in said common rail ( 6 ) is lower than that in said delivery pipe ( 8 ), and a second non-return valve ( 33 ) located along a pipe ( 34 ) communicating with said delivery pipe ( 8 ) at a first point ( 35 ) upstream from said first non-return valve ( 32 ) and at a second point ( 36 ) downstream from said first non-return valve ( 32 ) to rapidly drain the surplus fuel from said common rail ( 6 ) to said bypass solenoid valve ( 14 ) when said control unit ( 16 ) defines at least a predetermined sharp pressure-reduction threshold (Δp) of the order of 1000 bars in the required fuel pressure of said common rail ( 6 ) when the engine ( 2 ), after being run for a given time at high load is suddenly operated at low load or in neutral; wherein said predetermined sharp pressure-reduction threshold (Δp) is formed by a difference of pressure between the actual fuel pressure in said common rail ( 6 ) and the actual fuel pressure determined by said bypass solenoid valve ( 14 ); and said second non-return valve ( 33 ) opens in response to said predetermined sharp pressure-reduction threshold (Δp) and permits the drainage of said surplus fuel from said common rail ( 6 ) to said delivery pipe ( 8 ) when said difference of pressure exceeds said predetermined sharp pressure-reduction threshold (Δp), said second non-return valve ( 33 ) being loaded by an additional spring ( 37 ) of a force corresponding to said predetermined sharp pressure-reduction threshold (Δp).