Patent ID: 9546616
Date: 2017-01-17
CPC Classifications: F02D,F02M,Y02T

Claim:
1. A fuel supply system for an internal combustion engine, comprising: a fuel pump capable of pumping fuel from a fuel tank to the internal combustion engine; a motor driving the fuel pump; a pressure sensor configured to detect pressure of the fuel pumped from the fuel pump; and a control unit configured to output control signals to the motor, to perform feedback control of duty ratio of the control signals for the motor such that the pressure of the pumped fuel comes close to a predetermined target fuel pressure, to receive information relating to pressure of the fuel discharged from the fuel pump and information relating to an operating condition of the internal combustion engine, to calculate the duty ratio of the control signals such that discharge fuel pressure based on the information relating to the pressure of the fuel discharged from the fuel pump comes close to the predetermined target fuel pressure, to output control signals corresponding to the calculated duty ratio to the motor, to calculate duty lower limit guard value depending on the operating condition of the internal combustion engine based on the information relating to the operating condition of the internal combustion engine, to guard the lower limit value of the duty ratio with the duty lower limit guard value when outputting the control signals corresponding to the calculated duty ratio, and to control the duty lower limit guard value in order to limit an amount of decreases of the duty lower limit guard value in the step-like manner when the duty lower limit guard value decreases.