Discharge valve device, flush water tank device, and flush toilet

A discharge valve device provided in a flush water tank configured to supply flush water to a flush toilet, the discharge valve device comprising:

• a valve body configured to open and close a discharge opening provided in a bottom of the flush water tank;
• an actuation shaft including a lower end provided with the valve body, the actuation shaft being configured to open and close the discharge opening by moving up and down the valve body;
• a water storage cylinder configured to store a part of flush water in the flush water tank, the water storage cylinder including an outlet port configured to cause flush water in the water storage cylinder to flow outside of the water storage cylinder, the actuation shaft being inserted into the water storage cylinder in a vertical direction;
• and
• a float disposed in the water storage cylinder, the float being configured to cause buoyancy obtained by the flush water in the water storage cylinder to act on the actuation shaft,
• wherein when the float lowers with a decrease in water level in the water storage cylinder, the actuation shaft and the valve body are configured to be lowered in conjunction with the float and then the valve body is configured to close the discharge opening,
• during a period from when the valve body opens to when the valve body closes, either flushing mode of a large flushing mode or a small flushing mode is selectively performed, in the large flushing mode the flush water in the flush water tank is supplied from the discharge opening to the flush toilet in a first flush water amount, and in the small flushing mode the flush water is supplied in a second flush water amount smaller than the first flush water amount, and
• the water storage cylinder or the float is configured to change a lowering speed of the float with the decrease in water level in the water storage cylinder depending on the selected large flushing mode or small flushing mode,
• wherein a first total outflow amount of the flush water in the water storage cylinder flowing out from the outlet port to the flush water tank in the large flushing mode is larger than a second total outflow amount of the flush water in the water storage cylinder flowing out from the outlet port to the flush water tank in the small flushing mode.