Patent ID: 6565474
Filing Date: 2003-05-20
Classification: F16H

Abstract:
A hydraulic pressure control device for an automatic transmission in which control pressure is applied to and drained from each of a plurality of friction elements, including a first friction element and a second friction element, to produce various gear stages, the hydraulic pressure control device comprising:adjusting means for adjusting hydraulic pressure from an oil pump to produce an outputted hydraulic pressure; a control valve receiving the outputted hydraulic pressure from the adjusting means for generating the control pressure to be applied to at least some of the friction elements whose magnitude depends on a magnitude of the outputted hydraulic pressure, the control valve including a control port from which the control pressure is outputted, a first feed back port to which the outputted control pressure is adapted to be fed back, and a second feed back port to which the outputted control pressure is adapted to be fed back; a shift valve receiving the control pressure from the control valve and selectively positionable in a first position for applying hydraulic pressure to the first friction element and a second position for applying hydraulic pressure to the second friction element, the shift valve being operated in such a manner that fluid communication between the control port and each of the first and the second feedback ports is controlled to lower the control pressure from the control valve when the shift valve is in the second position relative to the control pressure from the control valve when the shift valve is in the first position; and switching means for switching the shift valve between the first position and the second position.