Hydraulic control device for automatic transmission

A hydraulic control device for an automatic transmission that has a primary pulley that includes a primary fixed sheave and a primary movable sheave, a secondary pulley that includes a secondary fixed sheave and a secondary movable sheave, and an endless belt wound as interposed between the primary fixed sheave and the primary movable sheave and wound as interposed between the secondary fixed sheave and the secondary movable sheave, the automatic transmission being configured such that a winding diameter of the belt around the secondary pulley is larger than a winding diameter of the belt around the primary pulley when a primary pressure for varying a position of the primary movable sheave in an axial direction and a secondary pressure for varying a position of the secondary movable sheave in the axial direction are equal to each other, the hydraulic control device comprising:

• a primary pressure control valve that has a first valve element and that regulates the primary pressure for varying the position of the primary movable sheave in the axial direction by varying a position of the first valve element in accordance with operation of a first electromagnetic actuator;
• a secondary pressure control valve that has a second valve element and that regulates the secondary pressure for varying the position of the secondary movable sheave in the axial direction by varying a position of the second valve element in accordance with operation of a second electromagnetic actuator;
• and
• a fail-safe valve that varies the position of the second valve element such that the secondary pressure is reduced such that the winding diameter of the belt around the secondary pulley and the winding diameter of the belt around the primary pulley are equal when the first electromagnetic actuator and the second electromagnetic actuator become inoperable.