Power train of hybrid vehicle

Disclosed is a power train of a hybrid vehicle that includes a first, second and third planetary gear sets each having first, second and third elements; a first motor generator connected with the first element of the second planetary gear set and the first element of the third planetary gear set; a second motor generator connected with the first element of the first planetary gear set; an engine connected with the second element of the second planetary gear set and the second element of the third planetary gear set; an output shaft connected with the second element of the first planetary gear set and the third element of the second planetary gear set; a brake selectively restraining rotation of the third element of the first planetary gear set; and a clutch selectively engaging/disengaging the third element of the first planetary gear set with the third element of the third planetary gear set.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based on, and claims priority from, Korean Application Serial Number 10-2008-0054518, filed on Jun. 11, 2008, the disclosure of which is hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to a power train of a hybrid vehicle, particularly a power train of a hybrid vehicle that uses an internal combustion engine and a motor generator driven by electricity as a power source providing a driving force to driving wheels.

BACKGROUND ART

Hybrid vehicles using an engine and a motor generator reduce the fuel consumption on the basis of a technology that uses, as a driving force, power from a motor generator having relatively good low-velocity torque characteristics at a low velocity and uses power from an engine having relatively good high-velocity torque characteristics at a high velocity. Further, as the hybrid vehicles do not generate exhaust gas while being driven by only the motor generator, it is environment-friendly. Techniques for reducing fuel consumption with a simpler configuration have been proposed.

SUMMARY

Embodiments of the present invention provide a power train of a hybrid vehicle having simple configuration, high power performance, and reduced weight and fuel consumption, while being easily equipped in the vehicle.

A power train of a hybrid vehicle includes a first planetary gear set, a second planetary gear set, a third planetary gear set, a first planetary gear set, a second planetary gear set, and a clutch. The second planetary gear set includes three elements. The third planetary gear set includes three elements. The two of the three elements are directly connected with two elements of the second planetary gear set and connected with a first motor generator and an engine. The first planetary gear set includes three elements. One of the three elements is connected with an output shaft, and another element is connected with a second motor generator. The other element of the three is directly connected with one of the elements of the second planetary gear set and the third planetary gear set other than the elements connected with the first motor generator and the engine and is intermittently connected with the other one of the elements of the second planetary gear set and the third planetary gear set other than the elements connected with the first motor generator and the engine. The brake selectively fixes the element of the first planetary gear set other than the elements connected with the output shaft and the second motor generator. The clutch can intermittently connect the element of the first planetary gear set connected with the brake to any one of the elements of the second planetary gear set and the third planetary gear set other than the elements connected with the first motor generator and the engine.

Preferably, the first motor generator and the engine are each connected with the two elements of the second planetary gear set and the third planetary gear set, which are directly connected to each other. The output shaft is connected with an element of the first planetary gear set directly connected with an element of the second planetary gear set. The clutch intermittently connects the element of the first planetary gear set with the element of the third planetary gear set.

Preferably, the first planetary gear set is a single-pinion type planetary gear set including a first sun gear connected with the second motor generator, a first carrier connected with the output shaft, and a first ring gear connected with the brake and the clutch. The second planetary gear set is a single-pinion type planetary gear set including a second sun gear connected with the first motor generator, a second carrier connected with the engine, and a second ring gear connected with the first carrier of the first planetary gear. The third planetary gear set is a double-pinion type planetary gear set including a third sun gear connected with the first motor generator, a third carrier connected with the engine, and a third ring gear connected with the first ring gear of the first planetary gear set through the clutch.

The planetary gear sets are coaxially arranged in parallel in the order of the first planetary gear set, the second planetary gear set, and the third planetary gear set. The first motor generator is connected with the second planetary gear set through the third planetary gear set. The second motor generator is connected with the first planetary gear set. The engine is connected with the third planetary gear set through the second planetary gear set, passing through between the first planetary gear set and the second planetary gear set. The output shaft is connected with the second planetary gear set through the first planetary gear set.

The first planetary gear set, in the lever analysis diagram, is arranged on a first straight line in the order of an element connected with the second motor generator, an element connected with the output shaft, and an element connected with the brake. The second planetary gear set, in the lever analysis diagram, is arranged on a second straight line in the order of an element connected with the output shaft, an element connected with the engine, and an element connected with the first motor generator. The third planetary gear set, in the lever analysis diagram, is arranged on the second straight line in the order of an element connected with the engine, an element connected with the first planetary gear set through the clutch, and an element connected with the first motor generator, in which when the clutch is engaged, the first straight line and second straight line make a single straight line.

The elements of the planetary gear sets are arranged on the second straight line in the order of the element of the second planetary gear set connected with the output shaft, the element of the second planetary gear set and the element of the third planetary gear set connected with the engine, the element of the third planetary gear set connected with the first planetary gear set through the clutch, the element of the second planetary gear set and the element of the third planetary gear set connected with first motor generator.

The power train of a hybrid vehicle according to the invention has a simple configuration, high power performance, and reduced weight and fuel consumption, while being easily equipped in the vehicle. In particular, since an engine mode that makes it possible to drive the vehicle using only engine to reduce the fuel consumption at constant high-velocity driving, the fuel consumption in long time driving on a highway can be reduced.

DETAILED DESCRIPTION

Embodiments of the invention are described hereafter in detail with reference to the accompanying drawings, but theses embodiments are just examples and can be achieved in various modifications by those skilled in the art. Therefore, the present invention is not limited to the embodiments.

Referring toFIG. 1, a power train of a hybrid vehicle includes: a second planetary gear set5including three elements; a third planetary gear set7including three elements two elements of which are directly connected with two elements of the second planetary gear set5and connected with a first motor generator1and an engine3; a first planetary gear set13including three elements one element of which is connected with an output shaft11, another element of which is connected with a second motor generator15, and the other element of which is directly connected with one of the elements of the second planetary gear set5and the third planetary gear set7other than the elements connected with the first motor generator1and the engine3and is intermittently connected with the other one; a brake17that selectively fixes the element of the first planetary gear set13other than the elements connected with the output shaft11and the second motor generator15; and a clutch9that intermittently connects the element of first planetary gear set13connected with the brake17to any one of the elements of the second planetary gear set5and the third planetary gear set7other than the elements connected with the first motor generator1and the engine3.

That is, the power train includes the three planetary gear sets5,7,13, one clutch9, and one brake17such that it can transmit/receive power to/from the two motor generators1,15, and receives power from the engine3and outputs shifted power through the output shaft11.

The first motor generator1and the engine3are each connected with the two elements of second planetary gear set5and the third planetary gear set7, which are directly connected to each other. The output shaft11is connected with an element of the first planetary gear set13directly connected with an element of the second planetary gear set5.

That is, the first motor generator1is connected with one element of the third planetary gear set7and one element of the second planetary gear set5. The engine3is connected with one element of the second planetary gear set5and one element of the third planetary gear set7. Further, the output shaft11is connected with one element of the first planetary gear set13and one element of the second planetary gear set5.

The first planetary gear set13is a single-pinion type planetary gear set, in which a first sun gear is connected with the second motor generator15, a first carrier is connected with the output shaft11, and a first ring gear is connected with the brake17and the clutch9.

The second planetary gear set5is a single-pinion type planetary gear set, in which a second sun gear is connected with the first motor generator1, a second carrier is connected with the engine3, and a second ring gear is connected with the first carrier of the first planetary gear set13.

The third planetary gear set7is a double-pinion type planetary gear set, in which a third sun gear is connected with the first motor generator1, a third carrier is connected with the engine3, and a third ring gear is connected with the first ring gear of the first planetary gear set13through the clutch9.

In this embodiment, the planetary gear sets are coaxially arranged in the order of the first planetary gear set13, the second planetary gear set5, and the third planetary gear set7. The first motor generator1is connected with the second planetary gear set5through the third planetary gear set7. The second motor generator15is connected with the first planetary gear set13. The engine3is connected with the third planetary gear set7through the second planetary gear set5, passing through between the first planetary gear set13and the second planetary gear set5. The output shaft11is connected with the second planetary gear set5through the first planetary gear set13.

As shown in the lever analysis diagrams ofFIGS. 2 to 6, the first planetary gear set13is arranged on a first straight line19in the order of an element connected with the second motor generator15, an element connected with the output shaft11, and an element connected with the brake17. The second planetary gear set5is arranged on a second straight line21in the order of an element connected with the output shaft11, an element connected with the engine3, and an element connected with the first motor generator1. The third planetary gear set7is arranged on the second straight line21in the order of an element connected with the engine3, an element connected with the first planetary gear set13through the clutch9, and an element connected with the first motor generator1, in which when the clutch9is engaged, the first straight line19makes a single straight line that is synchronized with the second straight line21.

The elements of the planetary gear sets are arranged on the second straight line21in the order of the element of the second planetary gear set5connected with the output shaft11, the element of the second planetary gear set5and the element of the third planetary gear set7connected with the engine3, the element of the third planetary gear set7connected with the first planetary gear set13through the clutch9, and the element of the second planetary gear set5and the element of the third planetary gear set7connected with the first motor generator1.

The operation in each mode of the power train of a hybrid vehicle according to an embodiment of the invention is described hereafter with reference to the lever analysis diagrams ofFIGS. 2 to 6, which shows arrangement of the elements of the planetary gear sets and relative gear ratios of the elements as well.

FIG. 2illustrates an electric vehicle mode driving the vehicle using at least one motor generator while not operating an engine.

In this mode, the brake17is engaged such that the first ring gear is fixed, and the clutch9is disengaged.

As torque is generated by the second motor generator15, power from the second motor generator15is transmitted to the first sun gear of the first planetary gear set13. Since the first ring gear is fixed by the brake17, the power from the second motor generator15is reduced through the first carrier and outputted to the output shaft11.

For illustration purposes, the rotational direction of the output shaft11is defined as a normal direction and the opposite direction is defined as an inverse direction hereafter.

The engine3is stopped and connected with the second carrier of the second planetary gear set5and the third carrier of the third planetary gear set7, such that the first motor generator1rotates in the inverse direction without torque.

FIG. 3illustrates a first hybrid mode, in which the brake17fixes the first ring gear and the clutch9is disengaged, such that first ring gear is disengaged from the third ring gear.

As the first motor generator1that has rotated in the inverse direction in the electric vehicle mode is rotated in the normal direction by torque as shown inFIG. 3, the engine3increases in rotational velocity and can be started and generate torque, and thus power supplied from the second motor generator15and power supplied from the engine3are simultaneously outputted to the output shaft11.

The first motor generator1functions as a generator that provides a reaction force according to the torque of engine3, thereby substantially controlling the shift ratio.

The second motor generator15cannot control the shift ratio because the first ring gear is fixed by the brake17, such that it only functions as a motor that transmits torque to the output shaft11through the first carrier.

FIG. 4illustrates a second hybrid mode that is different from the first hybrid mode, which is achieved by a process involving a change from the lever condition shown inFIG. 3to that shown inFIG. 6.

More specifically, in order to change from the first hybrid mode to the second hybrid mode, the engine3and the first motor generator1are controlled in the first hybrid mode to make the velocity of the third ring gear reach 0 as shown inFIG. 6, and then the clutch9is engaged and the brake17is disengaged.

After all of the first planetary gear set13, the second planetary gear set5, and the third planetary gear set7make a lever on a single straight line by engaging the clutch9as described above and the first ring gear can be rotated by disengaging the brake17, the first motor generator1and the second motor generator15are controlled to meet the condition shown inFIG. 4, thereby achieving the second hybrid mode.

Here, the first motor generator1functions as a motor, rotating in the normal direction, and the second motor generator15functions as a generator, rotating in the inverse direction.

FIG. 5shows an engine mode that can be provided by the power train of the invention.

The engine mode is achieved by controlling the shift ratio in the second hybrid mode such that the velocities of the first ring gear and the third ring gear are 0 as shown in the condition ofFIG. 6, engaging the brake17, and then removing torque of the first motor generator1and the second motor generator15.

Here, the engine3undertakes all of the torque supplied to the output shaft11and an overdrive shift ratio in which the second ring gear connected with the output shaft11rotates at a higher velocity than the second carrier connected with the engine3is achieved.

Therefore, since it is possible to achieve high-velocity traveling at the overdrive shift ratio only using the engine3, without driving the first motor generator1and the second motor generator15, it is possible to reduce a significant amount of fuel consumption especially when a vehicle is traveling at a high speed for a long time.