Power train of five-speed automatic transmission for vehicle

A power train for an automatic transmission, comprising:

• a compound planetary gear unit including a first ring gear, a first and second sun gear, first pinion gears in a gearing relationship with said first sun gear, second pinion gears in a gearing relationship with said first pinion gears and said second sun gear, a first planetary carrier for said first and second pinion gears, and a first ring gear in a gearing relationship with said first pinion gears;
• a second transmission unit operationally connected to said compound planetary gear unit;
• an input shaft supplying power from an engine;
• a first one-way clutch connected between said first planetary carrier and a housing of said automatic transmission;
• a first friction element selectively operationally connecting said first sun gear and said input shaft to establish a first forward speed ratio in cooperation with said first one-way clutch;
• a second one-way clutch connected to said second sun gear;
• a second friction element selectively operationally connecting said second one-way clutch to said housing of said automatic transmission to establish a second forward speed ratio;
• and
• a third friction element selectively connecting said first planetary carrier to said input shaft to establish a third forward speed ratio.

A power train for an automatic transmission, comprising:

• a compound planetary gear unit including a first ring gear, a first and second sun gear, first pinion gears in a gearing relationship with said first sun gear, second pinion gears in a gearing relationship with said first pinion gears and said second sun gear, a first planetary carrier for said first and second pinion gears, and a first ring gear in a gearing relationship with said first pinion gears;
• a second transmission unit operationally connected to said compound planetary gear unit;
• an input shaft supplying power from an engine;
• a first one-way clutch connected to said first sun gear;
• a second one-way clutch connected to said second sun gear;
• and
• a third one-way clutch connected between said first planetary carrier and said housing of said automatic transmission;
• a first friction element selectively operationally connecting said first one-way clutch and said input shaft to establish a first forward speed ratio wherein said first and third one-way clutches are engaged;
• and
• a second friction element selectively operationally connecting said second one-way clutch to said housing of said automatic transmission to establish a second forward speed ratio wherein said third one-way clutch is disengaged and said first and second one-way clutch are engaged.