The fluid control valve is arranged between an upstream side flow channel and a downstream side flow channel and controls or opens or closes a flow rate of a fluid flowing in the flow channel. For example, an arrangement shown in Patent Document 1 is known as a fluid control valve that controls a flow rate of a gas used for, for example, a semiconductor process.
The fluid control valve shown in Patent Document 1 has an arrangement that toric bottom formed grooves (hereinafter also called first bottom formed grooves) that are in communication with the upstream side flow channel and toric bottom formed grooves (hereinafter also called second bottom formed grooves) that are in communication with the downstream side flow channel are arranged alternatively in multiple layers on a valve seat surface (or a seating surface).
A valve inner flow channel that is arranged on the valve body member or the valve seat member and that is in communication with the upstream side flow channel and the downstream side flow channel is arranged on the bottom formed groove, and the valve inner flow channel is connected to a bottom surface of the bottom formed groove so that a communication bore is formed.
Then, in a state that the seating surface and the valve seat surface are attached, communication between the opening of the first bottom formed groove and the opening of the second bottom formed groove is blocked so as to be in a closed state wherein the upstream side flow channel and the downstream side flow channel are not connected. In a state that the seating surface is separated from the valve seat surface, the opening of the first bottom formed groove is in communication with the second bottom formed groove through a gap between the seating surface and the valve seat surface so as to be in an open state wherein the upstream side flow channel is connected to the downstream side flow channel.
The flow rate flowing in the fluid control valve depends on a separated distance between the seating surface and the valve seat surface assuming that there is no other bottleneck in the flow channel. More strictly speaking, a value achieved by multiplying a total length of a projection formed between the first bottom formed groove and the second bottom formed groove by the above-mentioned separated distance equals a cross-sectional area of the flow channel to be controlled, which represents a valve open degree, and therefore the flow rate flowing in the fluid control valve depends on the valve open degree.
Then, if the bottom formed grooves are formed in multiple layers, since the total length of the projection can be made longer compared with a case that the bottom formed groove is singular, it is possible to shorten the separated distance between the seating surface and the valve seat surface in order to secure the same cross-sectional area of the flow channel, thereby to promote downsizing of the actuator that drives the valve body member. Conversely if the separated distance between the seating surface and the valve seat surface is the same as that of a conventional arrangement, the cross-sectional area of the flow channel increases, thereby to enable increase of the flow rate or reduction of the pressure loss.
According to the above-mentioned principle, it will do well to arrange as many of the bottom formed grooves as possible.