Hydraulic control apparatus for automatic transmission

A hydraulic control apparatus for an automatic transmission, comprising:

• a plurality of friction engagement elements;
• a plurality of hydraulic servos engaging and disengaging respectively the plurality of friction engagement elements;
• hydraulic pressure supply means for generating a predetermined hydraulic pressure, and supplying the predetermined hydraulic pressure to the hydraulic servo of a predetermined friction engagement element selected in correspondence to a gear stage to be achieved;
• a switching valve including:
• a first input section where the predetermined hydraulic pressure generated by the hydraulic pressure supply means is inputted;
• a second input section where a second hydraulic pressure, other than the predetermined hydraulic pressure generated by the hydraulic pressure supply means, is inputted;
• a third input section where the predetermined hydraulic pressure generated by the hydraulic pressure supply means is provided for switching over the switching valve;
• and
• an output section for selectively outputting the predetermined hydraulic pressure inputted to the first input section and the second hydraulic pressure inputted to the second input section to the hydraulic servo of the predetermined friction engagement element;
• and
• valve switching means for further switching over the switching valve, so that the first input section and the output section are in communication and substantially no hydraulic pressure is supplied to the hydraulic servo of the predetermined friction engagement element at a time when the switching valve is in a state wherein the predetermined hydraulic pressure is not provided to the third input section and the second input section and the output section are in communication.

A hydraulic control apparatus for an automatic transmission, comprising:

• a plurality of hydraulic servos engaging and disengaging respectively a plurality of friction engagement elements;
• a solenoid and a control valve combination that supplies the hydraulic servo of a predetermined friction engagement element selected in correspondence to a gear stage to be achieved with a first hydraulic pressure;
• and
• an apply control valve that supplies a predetermined hydraulic servo with a second hydraulic pressure other than the first hydraulic pressure supplied by the solenoid and the control valve combination, in the case that the solenoid and the control valve combination is put in a failed state where the solenoid and the control valve combination can not supply the hydraulic servo of the predetermined friction engagement element with the first hydraulic pressure, and for not supplying the predetermined hydraulic servo with the second hydraulic pressure, in the case that the solenoid and the control valve combination is put in a substantially not supplied state where the solenoid and the control valve combination does not supply the hydraulic servo of the predetermined friction engagement element with the first hydraulic pressure.

A hydraulic control apparatus for an automatic transmission, comprising:

• a plurality of friction engagement elements;
• a plurality of hydraulic servos engaging and disengaging respectively the plurality of friction engagement elements;
• a first solenoid and control valve combination that supplies a predetermined hydraulic pressure, and supplying the predetermined hydraulic pressure to the hydraulic servo of the predetermined friction engagement element selected in correspondence to a gear stage to be achieved;
• a switching valve including:
• a first input section where the predetermined hydraulic pressure supplied by the first solenoid and control valve combination is inputted;
• a second input section where a second hydraulic pressure, other than the predetermined hydraulic pressure, supplied by a second solenoid and control valve combination, is inputted;
• a third input section where the predetermined hydraulic pressure generated by the first solenoid and control valve combination is inputted for switching over the switching valve;
• and
• an output section for selectively outputting the predetermined hydraulic pressure inputted to the first input section and the second hydraulic pressure inputted to the second input section to the hydraulic servo of the predetermined friction engagement element;
• and
• a valve switching solenoid that further switches over the switching valve, so that the first input section and the output section are in communication and substantially no hydraulic pressure is supplied to the hydraulic servo of the predetermined friction engagement element at a time when the switching valve is in a state wherein the predetermined hydraulic pressure is not input to the third input section and the second input section and the output section are in communication.