Hydraulic pressure control device for an automatic transmission

A hydraulic pressure control device for an automatic transmission in which control pressure is applied to and drained from a plurality of friction elements to produce various gear stages, comprising:

• a linear solenoid valve connected to a pump to adjust hydraulic pressure from the pump and produce an outputted hydraulic pressure;
• a control valve fluidly connected to the linear solenoid valve to receive the outputted hydraulic pressure from the linear solenoid valve and generate the control pressure to be applied to at least a first one of the friction elements and a second one of the friction elements, the control valve including a control port from which the control pressure is outputted, a first feed back port receiving control pressure and a second feed back port receiving control pressure;
• a shift valve fluidly connected to the control valve to receive the control pressure from the control valve, said shift valve including a movable valve main body, a first shift port connected to the first friction element, a second shift port connected to the second friction element, and a control pressure adjusting port connected to the second feed back port of the control valve;
• an ON-OFF solenoid valve connected to the shift valve to move the valve main body between a first position in which the hydraulic pressure is applied to the first friction element and is prevented from being applied to the second friction element and the control pressure is supplied to the first feed back port of the control valve while being prevented from being supplied to the second fee back port of the control valve, and a second position in which the hydraulic pressure is applied to the second friction element and is prevented from being applied to the first friction element and the control pressure is supplied to the second feed back control port of the control valve by way of the control pressure adjusting port and to the first feed back port of the control valve.

A method of controlling hydraulic pressure in an automatic transmission in which control pressure is applied to and drained from each of a plurality of friction elements to produce various gear stages, comprising:

• producing one gear stage by supplying control pressure from a control valve to a first one of the friction elements by way of a shift valve while preventing control pressure from being supplied to a second one of the friction elements by way of the shift valve;
• producing a different gear stage by supplying control pressure from the control valve to the second friction element by way of the shift valve while preventing control pressure from being supplied to the first friction element by way of the shift valve;
• and
• the control pressure supplied to the second friction element during the different gear stage being less than the control pressure supplied to the first friction element during the one gear stage.