| 摘要 |
PURPOSE:To increase high performance by adjustment even when the shape of a fluid entrance is different by forming a gap between an impeller and the chamber wall of a metering chamber and providing a resistance plate which gives resistance to fluid flowing in the metering chamber in the gap. CONSTITUTION:The resistance plate 21 forms the gap S between the impeller 12 and the chamber wall of the chamber 13 and gives resistance to the fluid flowing in the chamber 13 by reducing the external diameter of the impeller 12 to such size that the peripheral speed of the impeller 12 is nearly constant when the flow rate of the water flowing in the metering chamber 13 is constant regardless of the diameters of the fluid entrance 17 and a fluid exit 18. Consequently, the running water which flows in the chamber 13 is disturbed by the plate 21 in a fine or small flow rate area and strikes on the plate and then the impeller 12 to rotate the impeller 12. When the flow rate is large, almost all of the water forms a vortex flow along the chamber wall of the chamber 13 and the vortex flow increases the resistance by striking on the plate 21 to reduce the rotating speed of the impeller 12. The rotating speed of the impeller 12 in the small flow rate area increases greatly as compared with that in the large flow rate area and an instrumental error curve approximates a flat curve, thereby improving instrumental error characteristics, specially, in the fine or small flow rate area.
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