Switching unit, hydraulic machine and power generating apparatus

摘要

A switching unit (30,46) is for switching pressure in a pressure-switching target chamber (24). The switching unit includes a spool valve (40,48) including a first chamber (34,140); a second chamber (36,142); and a spool (38,144) including a first pressure-receiving surface (42,146) formed so as to receive hydraulic pressure of the first chamber and a second pressure-receiving surface (44,148) formed so as to receive hydraulic pressure of the second chamber, the second pressure-receiving surface having an area smaller than that of the first pressure-receiving surface. The spool valve is configured to switch the hydraulic pressure of the first chamber between pressure P 2 which is higher than pressure in the low pressure oil line and pressure P 1 which is lower than the pressure P 2 , while maintaining the hydraulic pressure of the second chamber at the pressure P 2 , so that the spool is moved and the pressure in the pressure-switching target chamber is switched.