| 摘要 |
PURPOSE:To automatically control the feed of magnetic fluid in accordance with the change detected in density of magnetic flux, by burying magnetic detector elements in an annular pole block which comes close to a fine annular projection on which magnetic flux is concentrated. CONSTITUTION:A drop of seal pressure resistance in a shaft seal gap due to the reduction of magnetic fluid 1 is detected by manetic detector elements 7 as a density of magnetic flux. A signal in compliance with the differential value of the detection is sent to a discriminator 8 so as to regain the density of magnetic flux under a normal state of sealing, and a motor 9 is actuated. Then a rack and pinion 6a is pushed downward to feed an adequate amount of magnetic fluid 1 from a supplier 6 through a hole 6c to a shaft seal gap between an annular projection 4 on the external circumference of a rotational shaft 3 and a pole block 2, 2a. As the seal pressure resistance in the shaft seal gap is reset to the normal level through make-up of the magnetic fluid 1, the detector elements 7 detect the normally restored density of magnetic flux and the motor 9 is interrupted. |
