PURPOSE: To suppress inside leakage which is caused by a pressure difference, so as to improve a volumetric efficiency by connecting an auxiliary pump to the suction port side of a gear pump, and interposing a pressure regulator for regulating suction pressure which nearly matches a discharging pressure, between the auxiliary pump and a pressure detector on the suction port side.
CONSTITUTION: In a constant amount detecting device in which a gear pump 5 driven by a motor 6 is interposed on the way of a fluid supplying passage 3 which is laid in form of piping between a liquid reserving tank 1 and a fluid using apparatus 2, an auxiliary pump 7 is interposed on the end part of the tank 1 side of the fluid supplying passage 3. First and second pressure detectors 8, 9 are connected respectively to the suction port 5a side and the discharging port 5b side of the gear pump 5, and a regulator 11 which has a controller 12 attached thereto is interposed upstream from the first pressure detector 8 on the suction port 5a side. In the controller 12, the difference between the detecting values of both pressure detectors 8, 9 is calculated, the regulator 11 is controlled so as to set the difference to be zero value. It is thus possible to prevent inside leakage which is caused by the pressure difference between the discharging port 5b side and the suction port 5a side of the gear pump 5.
TOKI SHINSUKE
FURUTA SATORU
