| 摘要 |
PROBLEM TO BE SOLVED: To heighten pressure reducing responsiveness of common rail pressure and improve NOx in exhaust gas by providing a solenoid valve opened when designated time elapses in the condition where the common rail pressure is higher than the targer pressure in the midway of a pressure relief pipe communicated with a fuel tank connected to a common rail. SOLUTION: A common rail 4 retaining high pressure fuel connects a high pressure pipe 9 branching off the common rail 4 to an injector 6. In the case where the engine rotating speed is lowered while fuel is not injected from the injector 6, when designated time elapses in the condition where the common rail pressure P is higher than the target pressure, a solenoid valve 18 is opened according to an opening and closing signal 19 from a control unit 13. Whereupon, some of fuel in the common rail 4 is let escape to a fuel tank 2 through a pressure relief pipe 17 to decrease the common rail pressure P. Thus, the amount of time until the common rail pressure P amounts to the target pressure is reduced to heighten the responsiveness, and NOx or the like in exhaust gas can be improved. |
