To provide a hydraulic pressure control apparatus capable of transmitting power from a power source to a pump impeller regardless of the kind of failure occurring in a hydraulic power transmission having an impeller clutch.
The hydraulic pressure control apparatus for the hydraulic power transmission includes a multi-plate impeller clutch 13a capable of separating a pump impeller 12 from the power source, wherein the impeller clutch 13a performs engagement by supplying hydraulic pressure to a hydraulic pressure chamber R3. The apparatus further includes a control valve 34 for controlling the hydraulic pressure to be supplied to the hydraulic pressure chamber R3, a fail valve 31 disposed in oil passages 24, 33 between the hydraulic pressure chamber R3 and the control valve 34 for selectively connecting the hydraulic pressure chamber R3 and the control valve 34 or the hydraulic pressure chamber R3 and a hydraulic supply source (Sec pressure), and an electronic control portion 36 controlling operations of the control valve 34 and the fail valve 31. The hydraulic pressure chamber R3 is connected to the hydraulic pressure source (Sec pressure) when at least one of the control valve 34, the fail valve 31, and the electronic control portion 36 fails.