Transmission for vehicle

1. A transmission for a vehicle, comprising:

a first planetary gear set, a second planetary gear set, a third, planetary gear set, and a fourth planetary gear set each including three rotary elements; and

a plurality of friction members,

wherein the first planetary gear set includes: a first rotary element connected to an input shaft; a second rotary element operating as a selectively-fixed element and selectively connected with a third rotary element of the third planetary gear set; and a third rotary element connected with a second rotary element of the second planetary gear set,

the second planetary gear set includes: a first rotary member operating as a fixed element;

the second rotary element selectively connected to an output shaft; and a third rotary element selectively connected with a third rotary element of the fourth planetary gear set,

the third planetary gear set includes: a first rotary element connected with a first rotary element of the fourth planetary gear set; a second rotary element connected to an input shaft; and a third rotary element selectively connected to a second rotary element of the fourth planetary gear set and the third rotary element of the fourth planetary gear set,

the fourth planetary gear set includes the second rotary element connected to an output shaft, and

the friction members are connected to at least one or more of the rotary elements of the planetary gear sets and control rotation of the rotary elements.

2. The transmission of claim 1 , wherein in the first planetary gear set, the first rotary element is a first sun gear, the second rotary element is a first carrier, and the third rotary element is a first ring gear,

in the second planetary gear set, the first rotary element is a second sun gear, the second rotary element is a second carrier, and the third rotary element is a second ring gear,

in the third planetary gear set, the first rotary element is a third sun gear, the second rotary element is a third carrier, and the third rotary element is a third ring gear, and

in the fourth planetary gear set, the first rotary element is a fourth sun gear, the second rotary element is a fourth carrier, and the third rotary element is a fourth ring gear.

3. The transmission of claim 2 , wherein the second rotary element of the first planetary gear set is connected to and disconnected from a transmission case by a third clutch, and

the second rotary element of the first planetary gear set and the third rotary element of the third planetary gear set are connected to and disconnected from each other by a fourth clutch.

4. The transmission of claim 2 , wherein the first rotary element of the second planetary gear set is connected to a transmission case,

the second rotary element of the second planetary gear set is connected to and disconnected from the output shaft by a first clutch, and

the third rotary element of the second planetary gear set and the third rotary element of the fourth planetary gear set are connected to and disconnected from each other by a fifth clutch.

5. The transmission of claim 2 , wherein the third rotary element of the third planetary gear set and the second rotary element of the fourth planetary gear set are connected to and disconnected from each other by a second clutch, and

the third rotary element of the third planetary gear set and the third rotary element of the fourth planetary gear set are connected to and disconnected from each other by a sixth clutch.

6. The transmission of claim 2 , wherein the first planetary gear set, the second planetary gear set, the third planetary gear set, and the fourth planetary gear set are sequentially arranged in an axial direction.

7. The transmission of claim 1 , wherein the friction members include:

a first clutch disposed for connecting and disconnecting the second rotary element of the second planetary gear set and the output shaft;

a second clutch disposed for connecting and disconnecting the third rotary element of the third planetary gear set and the second rotary element of the fourth planetary gear set;

a third clutch disposed for connecting and disconnecting the second rotary element of the first planetary gear set and a transmission case;

a fourth clutch disposed for connecting and disconnecting the second rotary element of the first planetary gear set and the third rotary element of the third planetary gear set;

a fifth clutch disposed for connecting and disconnecting the third rotary element of the second planetary gear set and the third rotary element of the fourth planetary gear set; and

a sixth clutch disposed for connecting and disconnecting the third rotary element of the third planetary gear set and the third rotary element of the fourth planetary gear set.

8. A transmission for a vehicle, comprising:

a first planetary gear set, a second planetary gear set, a third planetary gear set, and a fourth planetary gear set each including three rotary elements;

an input shaft connected to a first rotary element of the first planetary gear set and a second rotary element of the third planetary gear set;

a first shaft connecting a second rotary element of the first planetary gear set, a third clutch, and a fourth clutch;

a second shaft connecting a third rotary element of the first planetary gear set, a second rotary element of the second planetary gear set, and a first clutch;

a third shaft connecting a third rotary element of the third planetary gear set, a second clutch, the fourth clutch, and a sixth clutch;

a fourth shaft connecting a third rotary element of the second planetary gear set and a fifth clutch;

a fifth shaft connecting a third rotary element of the fourth planetary gear set, the fifth clutch, and the sixth clutch;

a sixth shaft connecting a first rotary element of the third planetary gear set and a first rotary element of the fourth planetary gear set;

an output shaft connecting a second rotary element of the fourth planetary gear set, the first clutch, and the second clutch; and

a transmission case connected with a first rotary element of the second planetary gear set and the third clutch.

9. The transmission of claim 8 , wherein the first clutch is disposed for connecting and disconnecting the second shaft and the output shaft,

the second clutch is disposed for connecting and disconnecting the third shaft and the output shaft,

the third clutch is disposed for connecting and disconnecting the first shaft and the transmission case,

the fourth clutch is disposed for connecting and disconnecting the first shaft and the third shaft,

the fifth clutch is disposed for connecting and disconnecting the fourth shaft and the fifth shaft, and

the sixth clutch is disposed for connecting and disconnecting the third shaft and the fifth shaft.

10. The transmission of claim 9 , wherein the first clutch is disposed for connecting and disconnecting the second rotary element of the second planetary gear set and the output shaft,

the second clutch is disposed for connecting and disconnecting the third rotary element of the third planetary gear set and the second rotary element of the fourth planetary gear set,

the third clutch is disposed for connecting and disconnecting the second rotary element of the first planetary gear set and the transmission case,

the fourth clutch is disposed for connecting and disconnecting the second rotary element of the first planetary gear set and the third rotary element of the third planetary gear set,

the fifth clutch is disposed for connecting and disconnecting the third rotary element of the second planetary gear set and the third rotary element of the fourth planetary gear set, and

the sixth clutch is disposed for connecting and disconnecting the third rotary element of the third planetary gear set and the third rotary element of the fourth planetary gear set.