Hydraulic control device for automatic transmission

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, and
• a 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;
• a pressure regulating valve that regulates a line pressure;
• a line pressure control valve that supplies a control hydraulic pressure for changing the line pressure to the pressure regulating valve via the cut-off valve;
• and
• a line pressure supply hydraulic fluid passage that supplies the line pressure to the pressure regulating valve via the cut-off valve to maintain the line pressure at a predetermined hydraulic 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 cut-off valve switches between hydraulic fluid passages so that when the valve element is at the second position, the control hydraulic pressure is supplied to the pressure regulating valve and the line pressure is not supplied to the pressure regulating valve through the line pressure supply hydraulic fluid passage, and when the valve element is at the first position, the control hydraulic pressure is not supplied to the pressure regulating valve and the line pressure is supplied to the pressure regulating valve through the line pressure supply hydraulic fluid passage.

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, and
• a 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,
• wherein the automatic transmission includes a predetermined range which is a non-traveling range, and
• when the predetermined range is selected, the valve element is set at the first position, and subsequently, when the line pressure is not detected by the line pressure detector, it is determined that a failure of the cut-off valve has occurred.

A hydraulic control device for an automatic transmission, comprising:

• a cut-off valve having a valve element located at one of a first position and a second position, the first position disabling supply of a hydraulic fluid to a frictional clutch or brake of the automatic transmission, the second position enabling supply of the hydraulic fluid to the frictional clutch or brake;
• and
• a line pressure detector configured to detect a line pressure, the cut-off valve being to control a hydraulic fluid passage so that the line pressure is supplied to the line pressure detector in a case where the valve element is at the first position and so that the line pressure is not supplied to the line pressure detector in a case where the valve element is at the second position,
• 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.