Pump apparatus

摘要

In a pump apparatus of the present invention, a portion of fluid sent to a fluid-sending destination is circulated to a pumping driving chamber on one side of a cylinder through a circulation passage. The pump apparatus includes a switching valve which switches inflow and outflow of the circulated fluid with respect to the pumping driving chamber. The switching valve is connected to a piston rod through a link mechanism, and mechanically carries out the switching operation using a pumping driving force.