PURPOSE: To set an optimum injection rate as well as to make improvements in killing noises of an engine and its vibration characteristic, by installing a device, which detects fuel injection start timing upon detecting a mechanical vibration in an injection system, and another device which detects the ignition timing of injection fuel.

CONSTITUTION: An injection start timing signal out of a fuel injection start timing detecting device 17 and an ignition timing signal out of an ignition timing detecting device both are fed to a control circuit 22. An injection quantity controller 26, an injection timing controller 27 and an injection rate controller 28 are each connected to the control circuit 22 via drive circuits 23W25. Thus, an injection rate for an ignition delay period is controlled according to a state of ignition delay time so that the injection rate can be set to its optimum one and, what is more, noises in a Diesel engine and its vibration characteristic are largely improvable.