Fluid controller

A fluid controller comprising:

• a block-like main body having a fluid inflow passage, a fluid outflow passage and a concave portion open upward;
• and a diaphragm pressed against or moved apart from an annular valve seat arranged within the concave portion of the main body so as to open and close the fluid passages, wherein
• the concave portion is formed into a shape including a large-diameter portion close to the opening and a small-diameter portion connected to a lower side of the large-diameter portion via a step portion, and the fluid controller is further provided with a flow path forming disk fitted to the concave portion,
• the flow path forming disk includes a large-diameter cylinder portion fitted to the large-diameter portion of the concave portion in a fluid tight manner, a small-diameter cylinder portion having an outer diameter smaller than an inner diameter of the small-diameter portion of the concave portion and having a lower end received by a bottom surface of the concave portion, and a coupling portion coupling a lower end portion of the large-diameter cylinder portion and an upper end portion of the small-diameter cylinder portion and received by the step portion of the concave portion, and
• a peripheral edge portion of the diaphragm is fixed to an upper end portion of the large-diameter cylinder portion of the flow path forming disk, a valve seat is provided in the upper end portion of the small-diameter cylinder portion of the flow path forming disk, an inner annular space of the large-diameter cylinder portion is formed by an inner periphery of the large-diameter cylinder portion of the flow path forming disk, the diaphragm, the valve seat and a top surface of the coupling portion of the flow path forming disk, a plurality of through holes communicating an outer annular space of the small-diameter cylinder portion formed between the small-diameter cylinder portion of the flow path forming disk and a peripheral surface of the small-diameter portion of the concave portion with an inner annular space of the large-diameter cylinder portion are formed in a coupling portion of the flow path forming disk, any one of the fluid inflow passage and the fluid outflow passage is communicated with a lower end of the small-diameter cylinder portion of the flow path forming disk, and the other is formed so as to be communicated with the outer annular space of the small-diameter cylinder portion.