Hydraulic pressure control device for an automatic transmission

A hydraulic pressure control device for an automatic transmission comprising:

• a plurality of linear solenoid valves each of which adjusts a hydraulic pressure outputted from an oil pump and outputs an adjusting pressure in response to a current applied to the linear solenoid valve;
• a plurality of control valves each connected to a respective one of the linear solenoid valves to output a control pressure in response to the adjusting pressure outputted from the respective linear solenoid valve;
• a plurality of friction engaging elements each of which is engaged or disengaged depending on the control pressure applied thereto to produce a plurality of gear stages of the automatic transmission depending on different combinations of engaged and disengaged conditions of the friction engaging elements;
• a plurality of shift valves each connected to one of the control valves to switch the friction engaging elements to which the control pressure is applied depending on the hydraulic pressure applied to the shift valves;
• a plurality of ON-OFF solenoid valves each connected to one of the shift valves to control application of the hydraulic pressure to each of the shift valves through energized and deenergized conditions of the ON-OFF solenoid valves;
• and
• a control unit which controls application of current to each of the linear solenoid valves and the ON-OFF solenoid valves;
• the control unit controlling the adjusting pressure applied to each of the control valves and the control pressure applied to each of the friction engaging elements by controlling the hydraulic pressure applied to each of the shift valves;
• the control unit establishing a plurality of shift patterns producing gear stages by different combinations of energized or deenergized conditions of at least some of the ON-OFF solenoid valves;
• the plurality of shift patterns including one shift pattern producing at least two gear stages and a different shift pattern producing at least two gear stages, with one of the gear stages in the one shift pattern being the same as one of the gear stages in the different shift pattern, one of the control valves applying control pressure to one of the friction engaging elements during the one shift pattern and applying control pressure to a different friction engaging element during the another shift pattern;
• the control unit establishing during transfer from the one shift pattern to the another shift pattern an intermediate shift pattern during which control pressure from the one control valve to the one friction engaging element is prevented.

A method of shifting an automatic transmission comprising:

• supplying control pressure from a plurality of control valves to a plurality of friction engaging elements to effect engagement and disengagement of different combinations of the friction engaging elements and produce a plurality of different gear stages;
• establishing one shift pattern that includes at least one gear stage;
• transferring to a different shift pattern that includes a gear stage different from the one gear stage;
• prohibiting application of control pressure from one of the control valves to one of the friction engaging elements during transfer from the one shift pattern to the different shift pattern when the one control valve applies control pressure to the one friction-engaging element under the one shift pattern and applies control pressure to another friction engaging element different from the one friction engaging element under the different shift pattern.