PURPOSE: To prevent the occurrence of cavitation and improve pump efficiency by controlling a pump so as to apply waved driving voltage for making the control of the return motion of a plunger possible to a solenoid driving the plunger of the pump.
CONSTITUTION: When a solenoid 2 is turned on, attractive force generated between a fixed core 4 and an armature 3 moves a piston (plunger) 4 downward against a spring 5. Liquid in a pressure chamber 11 is therefore pressurized to be discharged through a delivery valve 13. In this pump, sinusoidal wave driving voltage is applied to the solenoid 2 through a driver 21 on the basis of a sinusoidal wave signal generated by a sinusoidal wave generator 20. Thus the solenoid 2 is turned on with sinusoidal wave current lagging somewhat in its phase to cause the magnetic force of the solenoid 2 to move a piston 4 downward in the case of the increasing current, and on the other hand, its attractive force decreased gradually to slowly return the piston 4 in the case of the decreasing current.
UMEZAWA MICHIO
HORIIE MASANORI
IWASAKI KYUHACHIRO
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