Power transmission apparatus of hybrid vehicle

1. A power transmission apparatus for a vehicle using an engine and a motor-generator as a power source, the power transmission apparatus comprising:

a first shaft fixedly connected to the engine;

a second shaft selectively connectable to the first shaft and fixedly connected to the motor-generator;

a third shaft mounted on a same axis as the first shaft and selectively connectable to the second shaft;

a fourth shaft formed as a hollow shaft and mounted without rotational interference with the third shaft in an external circumference of the third shaft;

a fifth shaft which is mounted in parallel with one of the first, second, third and fourth shafts and is gear-engaged with the third shaft and the fourth shaft to output torque transmitted from the third shaft and the fourth shaft;

a sixth shaft mounted in parallel with one of the first, second, third, fourth and fifth shafts and gear-engaged with the fourth shaft to output torque transmitted from the fourth shaft;

a planetary gear set including a first rotation element, a second rotation element, and a third rotation element, and one rotation element among the first rotation element, the second rotation element and the third rotation elements is fixedly connected to the second shaft, the other rotation element among the first rotation element, the second rotation element and the third rotation elements is selectively connectable to a transmission housing, and another rotation element among the first rotation element, the second rotation element and the third rotation elements is fixedly connected to the fourth shaft; and

four gear trains forming an external gear connection between the first, second, third, fourth, fifth and sixth shafts.

2. The power transmission apparatus of claim 1 ,

wherein the planetary gear set is a single pinion planetary gear set, and

wherein the one rotation element among the first rotation element, the second rotation element and the third rotation elements is the third rotation element, the other rotation element among the first rotation element, the second rotation element and the third rotation elements is the first rotation element, and the another rotation element among the first rotation element, the second rotation element and the third rotation elements is the second rotation element.

3. The power transmission apparatus of claim 2 , wherein the first rotation element, the second rotation element and the third rotation element are a sun gear, a planet carrier, and a ring gear, respectively.

4. The power transmission apparatus of claim 2 ,

wherein the first rotation element is selectively connectable to the transmission housing by a brake;

wherein the second rotation element is fixedly connected to the fourth shaft; and

wherein the third rotation element is fixedly connected to the second shaft.

5. The power transmission apparatus of claim 1 , further including two clutches selectively connecting one shaft of the first, second, third, fourth, fifth and sixth shafts to another shaft of the first, second, third, fourth, fifth and sixth shafts, and a brake selectively connecting the other rotation element of the first, second and third rotation elements and the transmission housing.

6. The power transmission apparatus of claim 5 , wherein the two clutches include:

a first clutch mounted between the first shaft and the second shaft; and

a second clutch mounted between the second shaft and the third shaft,

wherein the other rotation element among the first rotation element, the second rotation element and the third rotation elements is the first rotation element, and

wherein the brake is mounted between the first rotation element of the planetary gear set and the transmission housing.

7. The power transmission apparatus of claim 1 , wherein the four gear trains include:

a first gear train including a first drive gear fixed to the third shaft, and a first driven gear mounted without rotational interference with the fifth shaft in an external circumference of the fifth shaft and gear-engaged with the first drive gear;

a second gear train including a second drive gear fixed to the third shaft, and a second driven gear mounted without rotational interference with the fifth shaft in an external circumference of the fifth shaft and gear-engaged with the second drive gear;

a third gear train including a third drive gear mounted without rotational interference with the fourth shaft in an external circumference of the fourth shaft, and a third driven gear fixedly mounted on the fifth shaft and gear-engaged with the third drive gear; and

a fourth gear train including a fourth drive gear fixed to the fourth shaft, and a fourth driven gear mounted without rotational interference with the sixth shaft in an external circumference of the sixth shaft and gear-engaged with the fourth drive gear.

8. The power transmission apparatus of claim 7 , further including:

three synchromesh selectively connecting the first, second, and fourth driven gears and second and third drive gears to the fourth, fifth and sixth shafts,

wherein the three synchromesh including:

a first synchromesh configured to selectively connect one of the first and second driven gears to the fifth shaft;

a second synchromesh configured to selectively connect the third drive gear and the fourth shaft, or selectively connect the third shaft and the fourth shaft; and

a third synchromesh configured to selectively connect the fourth driven gear and the sixth shaft.

9. A power transmission for a vehicle using an engine and a motor-generator as a power source, the power transmission apparatus comprising:

a first shaft fixedly connected to the engine;

a second shaft selectively connectable to the first shaft and fixedly connected to the motor-generator;

a third shaft mounted on a same axis as the first shaft and selectively connectable to the second shaft;

a fourth shaft formed as a hollow shaft and mounted without rotational interference with the third shaft in an external circumference of the third shaft;

a fifth shaft which is mounted in parallel with one of the first, second, third and fourth shafts and is gear-engaged with the third shaft and the fourth shaft to output torque transmitted from the third shaft and the fourth shaft;

a sixth shaft mounted in parallel with one of the first, second, third, fourth and fifth shafts and gear-engaged with the fourth shaft to output torque transmitted from the fourth shaft;

a planetary gear set including a first rotation element, a second rotation element, and a third rotation element, and one rotation element among the first rotation element, the second rotation element, and the third rotation element is fixedly connected to the second shaft, the other rotation element among the first rotation element, the second rotation element, and the third rotation element is selectively connectable to a transmission housing, and another rotation element among the first rotation element, the second rotation element, and the third rotation element is fixedly connected to the fourth shaft;

three friction elements connecting one shaft of the first, second, third, fourth, fifth and sixth shafts to another shaft of the first, second, third, fourth, fifth and sixth shafts, and selectively connecting the other rotation element of the first, second and third rotation elements and the transmission housing; and

four gear trains forming an external gear connection between the first, second, third, fourth, fifth and sixth shafts.

10. The power transmission apparatus of claim 9 ,

wherein the planetary gear set is a single pinion planetary gear set, and

wherein the one rotation element among the first rotation element, the second rotation element and the third rotation elements is the third rotation element, the other rotation element among the first rotation element, the second rotation element and the third rotation elements is the first rotation element, and the another rotation element among the first rotation element, the second rotation element and the third rotation elements is the second rotation element.

11. The power transmission apparatus of claim 10 , wherein the first rotation element, the second rotation element and the third rotation element are a sun gear, a planet carrier, and a ring gear, respectively.

12. The power transmission apparatus of claim 10 , wherein

the first rotation element is selectively connectable to the transmission housing by a brake;

the second rotation element is fixedly connected to the fourth shaft; and

the third rotation element is fixedly connected to the second shaft.

13. The power transmission apparatus of claim 9 , wherein the three friction elements include:

a first clutch mounted between the first shaft and the second shaft; and

a second clutch mounted between the second shaft and the third shaft,

wherein the other rotation element among the first rotation element, the second rotation element and the third rotation elements is the first rotation element, and

a brake mounted between the first rotation element of the planetary gear set and the transmission housing.

14. The power transmission apparatus of claim 9 , wherein the four gear trains include:

a first gear train including a first drive gear fixed to the third shaft, and a first driven gear mounted without rotational interference with the fifth shaft in an external circumference of the fifth shaft and gear-engaged with the first drive gear;

a second gear train including a second drive gear fixed to the third shaft, and a second driven gear mounted without rotational interference with the fifth shaft in an external circumference of the fifth shaft and gear-engaged with the second drive gear;

a third gear train including a third drive gear mounted without rotational interference with the fourth shaft in an external circumference of the fourth shaft, and a third driven gear fixedly mounted on the fifth shaft and gear-engaged with the third drive gear; and

a fourth gear train including a fourth drive gear fixed to the fourth shaft, and a fourth driven gear mounted without rotational interference with the sixth shaft in an external circumference of the sixth shaft and gear-engaged with the fourth drive gear.

15. The power transmission apparatus of claim 14 , further including:

three synchromesh selectively connecting the first, second, and fourth driven gears and second and third drive gears to the fourth, fifth and sixth shafts,

wherein the three synchromesh including:

a first synchromesh configured to selectively connect one of the first and second driven gears to the fifth shaft;

a second synchromesh configured to selectively connect the third drive gear and the fourth shaft, or selectively connect the third shaft and the fourth shaft; and

a third synchromesh configured to selectively connect the fourth driven gear and the sixth shaft.