PURPOSE: To enable an off-quantity oil containing highly hard impurities to be used, by coating a machine-finished surface of a plunger of a jerk type injection pump with a highly hard material such as TiC or the like, and then applying a highly hard material to abutting surfaces of rotating and driving flanges for example by welding, plating or the like.
CONSTITUTION: A plunger 3 is coated with a highly hard material such as TiC by chemical vacuum deposition, and after a highly hard material is applied to the two surfaces 321 of a rotating flange 32 that abut against the fork section 61 of a pinion 6 by brazing, welding or plating, the surfaces are coated with the same highly hard coating material. Thus as the plunger surfaces are coated with a highly hard material such as TiC or the like, if there are hard foreign matters in a fuel, the surfaces are hardly damaged. Further as the coating by vacuum deposition can be made very thin, if the accuracy of the stock has been increased, lapping or the like after the vacuum deposition is unrequired, or if lapping is carried out, since its period is short, a plunger having highly hard surfaces can be obtained inexpensively.
TAKAISHI TATSUO
NOUTOMI HIROSHI
YAMAGUCHI HARUO
