Shift control apparatus for automatic transmission

A shift control apparatus for an automatic transmission which requires activation of four engagement elements during a shift from a first gear speed to a second gear speed, in which the first gear speed is achieved by engagement of first and second engagement elements and the second gear speed is achieved by engagement of third and fourth engagement elements, wherein the control apparatus comprises shift control means for starting an engagement control of the fourth engagement element after a start of an engagement control including that of activation of the third engagement element and before a start of an engagement of the third engagement element;

• the third and fourth engagement elements are controlled by hydraulic pressures in hydraulic servos therefore, and the engagement control by the shift control means activates the third and fourth engagement elements by supplying the hydraulic pressure to the hydraulic servos therefore;
• the shift control means comprises activation control means for maintaining the hydraulic pressures of the hydraulic servos therefore at a base pressure so as to prevent a start of the engagement of the fourth engagement element for a period after the activation control means activates the fourth engagement element until at least the third engagement element completes engagement;
• and the shift control means maintains the hydraulic pressure of the hydraulic servo for the fourth engagement element at a stand-by pressure immediately before the start of the engagement after completion of the engagement of the third engagement element.

A control apparatus for an automatic transmission which requires activation of four engagement elements during a shift from a first gear speed to a second gear speed, in which the first gear speed is achieved by engagements of first and second engagement elements, a transient gear speed is achieved by engagements of the second engagement element and a third engagement element, and the second gear speed is achieved by engagements of the third engagement element and a fourth engagement element, wherein the control apparatus comprises shift control means for starting an engagement control of the fourth engagement element in the middle of a shift from the first gear speed to the transient gear speed;

• the third and fourth engagement elements are controlled by hydraulic pressures in hydraulic servos therefore, and the engagement control by the shift control means activates the third and fourth engagement elements by supplying the hydraulic pressure to the hydraulic servos therefore;
• the shift control means comprises activation control means for maintaining the hydraulic pressures of the hydraulic servos therefore at a base pressure so as to prevent a start of the engagement of the fourth engagement element for a period after the activation control means activates the fourth engagement element until at least the third engagement element completes engagement;
• and the shift control means maintains the hydraulic pressure of the hydraulic servo for the fourth engagement element at a stand-by pressure immediately before the start of the engagement after completion of the engagement of the third engagement element.