초록 ▼

To make it possible to maintain speeds during failures in an automatic transmission that does not have exclusive friction elements corresponding to the attainment of each speed. The hydraulic control apparatus of an automatic transmission, provided with control means 71-74 for supplying regulated pr

To make it possible to maintain speeds during failures in an automatic transmission that does not have exclusive friction elements corresponding to the attainment of each speed. The hydraulic control apparatus of an automatic transmission, provided with control means 71-74 for supplying regulated pressure to each of the hydraulic servos 81-84 that are first through fourth friction elements to which hydraulic pressure is supplied from the oil path L1, and provided with switching valves (1)-(5) for cutting off the supply of hydraulic pressure to friction elements other than the friction elements that engage in each speed, on the upstream side of the supply paths L31, L32, L10, L11 and L12. Each switching valve is switched by hydraulic pressure (C1-C3, B1 pressures) regulated by the control means that achieve regulated pressure operating conditions during failures, and selective application of signal pressure (Sol, SolB, SoIC pressures) output by the control means as operating means. In a speed that has been attained, the supply path to friction elements that are not to be engaged is cut off. Through this, even during failures the regulated pressure action of the control means corresponding to friction elements that are not to be engaged is ineffective, so the speed that has been attained is fixed.

대표청구항 ▼

1. A hydraulic control apparatus for an automatic transmission, of the type of hydraulic control apparatus provided with a plurality of friction elements and hydraulic servos for operating such, wherein a plurality of speeds can be achieved by engaging at least two friction elements at a time out of

1. A hydraulic control apparatus for an automatic transmission, of the type of hydraulic control apparatus provided with a plurality of friction elements and hydraulic servos for operating such, wherein a plurality of speeds can be achieved by engaging at least two friction elements at a time out of said plurality of friction elements, the hydraulic control apparatus provided with a switching means for cutting off hydraulic control to the friction elements other than the friction elements engaged in order to achieve each speed within said plurality of speeds, whereinsaid plurality of speeds includes a third speed which, from among the friction elements, engages at least the first and third friction elements and disengages the second friction element, a fourth speed which engages the first and second friction elements and disengages the third friction element, and a fifth speed which engages the second and third friction elements and disengages the first friction element; and, said switching means includes a first switching valve which cuts off hydraulic control to said first friction element by applying, as a signal pressure, hydraulic pressure to the third friction element engaged in at least said third and fifth speeds and the second friction element engaged in said fifth speed, and a second switching valve that cuts off hydraulic control to said third friction element by applying, as a signal pressure, hydraulic pressure to the first friction element engaged in said third and fourth speeds and the second friction element engaged in said fourth speed.