JPS5490601A - Pump pressure control system - Google Patents

Abstract

PURPOSE: To reduce the fluctuation of pressure at the changing of the number of pumps by providing a switching speed setter and a switching circuit to switch between the output of switching speed setting and the instruction of presure control for increasing or decreasing the revolutions of a variable pump by a fixed number at the changing of the number of pumps.

CONSTITUTION: When discharge is reduced under Q₁₁, a pump number setter 8 is operated to open a switch S₁ and close a switch S₃ in a switching circuit 11. By this operation, a speed setter SR₂ is rapidly shifted from a curve A₄ to a curve A₃ by giving a number of revolutions N₃ for example. Consequently, the driving point is shifted from B₅ to B₁, and the pressure difference is reduced from P₁₄ to P₁₁. After a constant speed pump P₂ is stopped, the switch S₃ is opened again and the switch S₁ is closed for returning to a pressure system. Thus, the fluctuation of pressure can be reduced by controlling speed by a fixed number of revolutions by means of a speed setting signal from a switching speed setter 10 for corresponding to a standard speed previously adjusted to the pump characteristics at the changing of the number of pumps.

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