Patent ID: 7846053
Filing Date: 2010-12-07
Classification: F16H

Abstract:
1. A hydraulic control system of an eight-speed automatic transmission for a vehicle for controlling a first clutch at first, second, third, and forth forward speeds and an L range, a second clutch operated at fourth, fifth, sixth, seventh, and eighth forward speeds, a third clutch operated at the third and fifth forward speeds and a reverse speed, a fourth clutch operated at the sixth forward speed, a first brake operated at the second and seventh forward speeds, and a second brake operated at the eighth forward speed and the L range, the hydraulic control system comprising: a first clutch control portion that provides a first supply of a D range pressure to the first clutch, the first supply of the D range pressure being controlled by a first pressure control valve and a first pressure switching valve by a control of a first proportional control valve; a second clutch control portion that provides a second supply of the D range pressure to the second clutch via a first fail-safe valve, the second supply of the D range pressure being controlled by a second pressure control valve and a second pressure switching valve by a control of a second proportional control valve; a third clutch control portion that provides a first supply of a line pressure to the third clutch, the first supply of the line pressure being controlled by a third pressure control valve and a third pressure switching valve by a control of a third proportional control valve, a second supply of the line pressure to the third pressure control valve being controlled by a fourth pressure switching valve by a control of a fourth proportional control valve; a first brake control portion that provides a third supply of the D range pressure to the first brake, the third supply of the D range pressure being controlled by the fourth pressure control valve and the fourth pressure switching valve by a control of the fourth proportional control valve, a fourth supply of the D range pressure to the fourth pressure control valve being controlled by the third pressure switching valve by a control of the third proportional control valve; a second brake control portion that provides a third supply of the line pressure or a supply of an R range pressure to the second brake via a second fail-safe valve, the third supply of the line pressure being controlled by a fifth pressure control valve and a fifth pressure switching valve by a fifth proportional control valve, a fourth supply of the line pressure to the fifth pressure control valve being controlled by a sixth pressure switching valve by a control of a sixth proportional control valve, and the R range pressure being supplied from a manual valve to the second fail-safe valve through a switching valve; and a fourth clutch control portion that provides a fifth supply of the D range pressure to the fourth clutch via a third fail-safe valve, the fifth supply of the D range pressure being controlled by a sixth pressure control valve and the sixth pressure switching valve by a control of the sixth proportional control valve, and a sixth supply of the D range pressure to the sixth pressure control valve being controlled by the fifth pressure switching valve by a control of the fifth proportional control valve.