Valve for water flow control

A valve comprising:

• an actuation assembly including a drive device configured to generate a driving force, a needle shaft connected, at one end thereof, to the drive device to receive the driving force from the drive device and perform linear motion, a needle nut coupled to the drive device and having an empty space through which the needle shaft passes, so as to guide the linear motion of the needle shaft, and a valve disc coupled to an opposite end of the needle shaft;
• a body coupled with the actuation assembly and having a valve opening inside, the valve opening being selectively opened or closed as the valve disc, which is inserted into the body in which water flows, performs linear motion,
• wherein the needle shaft includes a small-diameter part of which distal end is inserted into a center hole formed inside the body so that the motion of the needle shaft along a reference direction is guided by the center hole and a large-diameter part which has a larger diameter than that of the small-diameter part, wherein the small-diameter part extends along the reference direction from the large-diameter part,
• wherein the valve disc is coupled to the small-diameter part, configured to face the reference direction, further protrude beyond the needle nut along the reference direction, and have a convex shape along the reference direction, and the valve disc is formed such that an effective region of a flow passage formed between a periphery of the valve opening and an outer surface of the valve disc that is most adjacent to the periphery of the valve opening is formed like a side surface of a truncated cone when the valve disc performs the linear motion along the reference direction,
• wherein the small-diameter part is configured to pass through the valve disc, and
• wherein the actuation device further includes a buffer ring coupled to the small-diameter part and disposed between the valve disc and the large-diameter part.