초록 ▼

A hydraulic pressure control system for an automatic transmission is capable of reducing the size and simplifying the structure of a lockup controlling hydraulic circuit. An oil pressure output from a solenoid valve acts on an oil pressure chamber. The internal pressure of another oil pressure chamb

A hydraulic pressure control system for an automatic transmission is capable of reducing the size and simplifying the structure of a lockup controlling hydraulic circuit. An oil pressure output from a solenoid valve acts on an oil pressure chamber. The internal pressure of another oil pressure chamber becomes high only in a forward low-speed range and becomes low in all of the other gear shift ranges. The internal pressure of another oil pressure chamber becomes high only in forward ranges and becomes low in neutral and reverse ranges. The valve member moves in accordance with oil pressures applied to the oil pressure chambers to change over oil paths connected to a clutch control oil chamber and a torque converter oil chamber, whereby a lockup clutch assumes one of engaged, slip, and released states. Since an oil pressure signal according to a gear shift range and a vehicular running range is fed to the changeover valve and on the basis of this signal the changeover valve determines whether the engagement of the lockup clutch is to be permitted or inhibited, the circuit of a lockup control unit can be reduced in size and simplified.

대표청구항 ▼

[ What is claimed is:] [1.] A hydraulic pressure control system for an automatic transmission in which a plurality of gear shift ranges are switched over from one to another by coupling and uncoupling each of a plurality of frictional coupling elements provided in the automatic transmission, said hy

[ What is claimed is:] [1.] A hydraulic pressure control system for an automatic transmission in which a plurality of gear shift ranges are switched over from one to another by coupling and uncoupling each of a plurality of frictional coupling elements provided in the automatic transmission, said hydraulic pressure control system comprising:a torque converter;a lockup device, disposed adjacent to said torque converter, for transmitting power from a drive side of said system to said torque converter directly;control means for controlling at least one of a locking oil pressure and an unlocking oil pressure to be applied to said lockup device;forward range detecting means for detecting a forward range of said system;gear shift range detecting means for detecting a gear shift range of said system; anda changeover valve for changing over oil paths connected to said lockup device to bring said lockup device into one of a lock permit state and a lock inhibit state;wherein said changeover valve changes over said oil paths in accordance with oil pressure signals from said control means, said forward range detecting means and said gear shift range detecting means.