| 主权项 |
1. A hydraulic control device for an automatic transmission, comprising:
a plurality of engagement mechanisms; a plurality of planetary gear mechanisms that achieve a predetermined shift stage according to a combination of engagement and release of the engagement mechanisms, the engagement mechanisms including
a mechanical clutch or brake that fixes one of rotational elements of the planetary gear mechanisms to a casing of the automatic transmission according to a rotation direction of the rotational element, anda frictional clutch or brake that achieves a shift stage in combination with the mechanical clutch or brake; a cut-off valve having a valve element which is located at any one of a first position and a second position, the first position disabling supply of a hydraulic fluid to the frictional clutch or brake, the second position enabling supply of the hydraulic fluid to the frictional clutch or brake; and a line pressure detector that detects a line pressure, wherein the cut-off valve switches between hydraulic fluid passages so that when the valve element is at the first position, the line pressure is supplied to the line pressure detector, and when the valve element is at the second position, the line pressure is not supplied to the line pressure detector, and wherein the hydraulic control device determines a failure of the cut-off valve has occurred in a case where the line pressure detector does not detect the line pressure after the valve element is positioned at the first position. |
