PISTON TYPE FLUID PUMP

PURPOSE:To improve lubrication efficiency by enabling repeated feeding of lubricant stored in a circular recess formed in the innercircumferential edge at the lower end opening of cylinder while opening upward to the outercircumference of piston section through plunging of an annular projection of piston. CONSTITUTION:An annular recess 12c is provided at the lower end opening of a cylinder liner 12 while an annular projection 21b is provided on the piston section 21 of piston 20 to be plunged repeatedly into said recess 12c when sliding. Consequently, engine oil sucked into the cylinder section 12a through suction of piston 20 and adhered to the innercircumference of cylinder liner 12 will store in said recess 12c then provided through function of said projection 21b to an annular recess 21a in the piston section 21, O-ring 23, piston ring 24, etc.. As a result, lubrication effect at the sliding section between the cylinder section 12a and piston section 21 is improved to prevent deterioration of liquid-tightness of pump chamber R1 while abrasion of piston ring 24 is reduced to improve the durability.