Fuel injection device

Claim 1

A fuel injection device comprising: (a) injection timing computation means for computing a fuel injection timing according to operating conditions of an internal combustion engine; (b) injection quantity computation means for computing a fuel injection quantity according to the operating conditions of the internal combustion engine; (c) displacement computation means for computing a necessary amount of displacement for a booster piston forcing fuel to a fuel injection nozzle, based on a value computed by said injection quantity computation means; (d) piston driver means for driving said booster piston according to a value computed by said injection timing computation means and a value computed by said displacement computation means; (e) displacement detection means for detecting the displacement of said booster piston; (f) counter means for counting a total number of injection achieved after said fuel injection device is started; (g) monitor signal judgment means for making a judgment when a predetermined period of time has elapsed after the start of fuel injection, so as to determine whether a value detected by said displacement detection means is normal or not; (h) reference displacement memory means for storing a value detected by said displacement detection means when said booster piston has been driven over a period of time corresponding to said computed value of said displacement computation means; (i) maximum value memory means for detecting and storing a maximum value detected by said displacement detection means at each fuel injection; (j) first difference computation means for computing the difference between said value stored in said reference displacement memory means and said value stored in said maximum value memory means; (k) second difference computation means for computing the difference between said value computed by said displacement computation means and a value computed by said first difference computation means; (l) drive signal changeover means for processing a value counted by said counter means and a result of judgment made by said monitor signal judgment means to select one of said value computed by said displacement computation means when said value counted by said counter means is 1, said value computed by said second difference computation means when said value counted by said counter means is more than 2 and said value detected by said displacement detection means is judged normal by said monitor signal judgment means, and said value computed by said displacement computation means when said value counted by said counter means is more than 2 and said value detected by said displacement detection means is judged abnormal by said monitor signal judgment means, and also for outputting the thus selected value to said piston drive means; (m) comparator means for comparing said value detected by said displacement detection means with said value computed by said second difference computation means to determine the largeness of the thus compared values; (n) and operation inhibition means for processing said value counted by said counter means and a result of comparison made by said comparator means to inhibit operation of said piston driver means when said value counted by said counter means is more than 2 and said value detected by said displacement detection means is larger than said value computed by said second difference computation means.