Apparatus for controlling fuel injection timing

An apparatus for controlling fuel injection timing, comprising:

• a fuel injection timing control mechanism including a body supporting an input shaft with a first gear secured thereto, an output shaft with a fourth gear secured thereto and an axially movable shaft extending parallel to said input and output shafts and having a second and a third gear secured thereto, said second and third gears being respectively in mesh with said first and fourth gears, at least one of said first and fourth gears being a helical gear;
• a piston-cylinder assembly having a piston rod coupled to said axially movable shaft;
• and
• means for controlling the operation of said piston-cylinder assembly, said means including detector means for directly detecting the phases of said first and fourth gears by monitoring said first and fourth gears, means for obtaining detected phase angle data from the output of said detector means and solenoid-operated valve means controlled according to the difference between reference phase angle data and said detected phase angle data to control the flow of operating fluid into and out of said piston-cylinder assembly, said solenoid-operated valve means including a first and a second three-way solenoid-operated valve each having an inlet port communicated with a hydraulic driving pressure source, said first three-way solenoid-operated valve having a first outlet port communicated with a head side section of said piston-cylinder assembly and a second outlet port communicated with a tank, said second three-way solenoid-operated valve having first outlet port communicated with a rod side section of said piston-cylinder assembly and a second outlet port communicated with said tank.