Power transmission system of hybrid electric vehicle

1. A power transmission system of a hybrid electric vehicle that uses an engine and first and second motor/generators as power sources, comprising:

an engine power delivery module transmitting power of the engine directly to the first motor/generator as driving power for generating electricity and selectively transmitting the power of the engine as driving power for driving the vehicle; and

a motor power delivery module disposed in parallel with and independently from the engine power delivery module, and directly transmitting power of the second motor/generator as driving power for driving the vehicle,

wherein the engine power delivery module comprises:

a first input shaft directly connected to the engine and receiving the power of the engine;

a planetary gear set including a sun gear directly connected to the first motor/generator, a planet carrier directly connected to the first input shaft, and a ring gear directly connected to a transmission housing to transmit power of the first shaft to the first motor/generator with a rotation speed of the first input shaft being increased whenever the engine operates;

an intermediate shaft directly connecting the sun gear with the first motor/generator to transmit the power of the first input shaft to the first motor/generator; and

a first output shaft disposed in parallel with the first input shaft and selectively and operably connecting the first input shaft with a differential apparatus through a clutch, and

wherein the first input shaft is provided with a first drive gear fixedly disposed on a rear end thereof and meshed with a first driven gear fixedly disposed on the first output shaft.

2. The power transmission system of claim 1 , wherein the intermediate shaft is a hollow shaft and is disposed at a radial exterior of and concentrically with the first input shaft, and the planetary gear set and the first motor/generator are disposed respectively at a radial exterior of both end portions of the intermediate shaft.

3. The power transmission system of claim 2 , wherein the planetary gear set is disposed at a rear end portion of the intermediate shaft and the first motor/generator is disposed at a front end portion of the intermediate shaft.

4. The power transmission system of claim 3 , wherein the planetary gear set is a single pinion planetary gear set.

5. The power transmission system of claim 1 , wherein the first output shaft is provided with the first driven gear disposed on a first end portion of the first output shaft, and a first output gear meshed with a final reduction gear of the differential apparatus and fixedly disposed on a second end portion of the first output shaft.

6. The power transmission system of claim 1 , wherein the clutch is disposed on the first input shaft.

7. The power transmission system of claim 1 , wherein the clutch is disposed on the first output shaft.

8. The power transmission system of claim 1 , wherein the motor power delivery module comprises:

a second input shaft disposed in parallel with the first input shaft and receiving power of the second motor/generator; and

a second output shaft disposed in parallel with the second input shaft, receiving the power of the second input shaft and transmitting the power of the second input shaft to the differential apparatus.

9. The power transmission system of claim 8 , wherein the second input shaft is provided with a second drive gear outputting power of the second input shaft and fixedly disposed on a front end portion thereof.

10. The power transmission system of claim 9 , wherein a second driven gear meshed with the second drive gear is fixedly disposed on a first end portion of the second output shaft, and a second output gear meshed with a final reduction gear of the differential apparatus is fixedly disposed on a second end portion of the second output shaft.

11. A power transmission system of a hybrid electric vehicle that uses an engine and first and second motor/generators as power sources, comprising:

an engine power delivery module including a first input shaft directly connected to the engine to receive power of the engine, a planetary gear set including a sun gear directly connected to the first motor/generator, a planet carrier directly connected to the first input shaft, and a ring gear directly connected to a transmission housing to transmit power of the first shaft to the first motor/generator with a rotation speed of the first input shaft being increased whenever the engine operates, an intermediate shaft directly connecting the sun gear with the first motor/generator to transmit the power of the first input shaft to the first motor/generator, and a first output shaft disposed in parallel with the first input shaft and selectively and operably connecting the first input shaft with a differential apparatus through a clutch; and

a motor power delivery module including a second input shaft disposed in parallel with the first input shaft and receiving power of the second motor/generator, and a second output shaft disposed in parallel with the second input shaft, receiving power of the second input shaft and transmitting the power of the second input shaft to the differential apparatus,

wherein the first input shaft is provided with a first driven gear fixedly disposed on a rear end of the first input shaft and meshed with a first drive gear fixedly disposed on the first output shaft.

12. The power transmission system of claim 11 , wherein the intermediate shaft is a hollow shaft and is disposed at a radial exterior of and concentrically with the first input shaft, and the planetary gear set and the first motor/generator are disposed respectively at a radial exterior of both end portions of the intermediate shaft.

13. The power transmission system of claim 12 , wherein the planetary gear set is disposed at a rear end portion of the intermediate shaft and the first motor/generator is disposed at a front end portion of the intermediate shaft.

14. The power transmission system of claim 13 , wherein the planetary gear set is a single pinion planetary gear set.

15. The power transmission system of claim 11 , wherein the clutch is disposed on the first input shaft or the first output shaft.