| 摘要 |
PURPOSE:To detect the freezing in a feed and discharge pipe in advance by providing a piezoelectric oscillator which transmits vibrations to the freezable liquid in a heat-conductive container and detects the freezing state of the freezable liquid from variation in resonance characteristics. CONSTITUTION:The metallic heat-conductive container 2 which has a space 3 for forming a reservoir for water as the freezable liquid is so formed that the temperature of the feed and discharge pipe 5 is easy to conductor. The metallic container 2 is made of aluminum or copper; and the piezoelectric oscillator 1 which contacts the water in the container 2 is provided on one outside surface and a radiation fin 4 which improves cooling effect is provided on the other outside surface. The metallic container 2 as a freezing detection part is fixed to the outer periphery of the feed and discharge pipe 5 with a freezable liquid injection port 6 up, and water is injected into the space 3 separately from the water in the paper and discharge pipe 5. The diezoelectric oscillator 1 is formed by sticking a piezoelectric element 12 inside the closed end part 13 of a metallic outside pipe 11 so that the oscillator enters flexural oscillations when the piezoelectric element 12 is driven. |
