FUEL PRESSURE WAVEFORM ACQUISITION DEVICE

PROBLEM TO BE SOLVED: To provide a fuel pressure waveform acquisition device for extracting with high accuracy a pressure waveform caused by a target injection which is one of injections of a second stage or later of multistage injections, from waveforms detected at the time of multistage injection.SOLUTION: A fuel injection system includes a fuel injection valve 10 which injects fuel from an injection hole 11b and a fuel pressure sensor 20 which detects the change in fuel pressure generated inside a high pressure pipeline 43. An ECU 30 acquires a pressure waveform detected by the fuel pressure sensor 20 during performing a multistage injection as a waveform detected at the time of multistage injection, memorizes a model waveform, which is used as a standard of the pressure waveform when an injection that is preceding an target injection is performed without performing the target injection when any one of injections of a second stage or later of an injection is considered as the target injection among multistage injections, and extracts the pressure waveform resulting from the target injection by deducting the model waveform from the detected waveform at the multistage injection. The ECU 30 corrects the model waveform used for the extraction by a ratio according to a maximum injection rate in the injection of the preceding stage.