FORM 2
The PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION (See Section 10; rule 13)
TITLE OF THE INVENTION A Method For Delivering Power Through A Hybrid Drive And System Thereof
APPLICANTS
TATA MOTORS LIMITED, an Indian Company
Having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
INVENTOR
Mr. Janardhanan Venkatapathi
An Indian national
Of TATA MOTORS LIMITED
An Indian company having its registered office
At Bombay House, 24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
PREAMBLE TO THE DESCRIPTION The following specification described the invention

FIELD OF THE INVENTION
The invention is related to a hybrid drivetrain for a vehicle.
BACKGROUND OF THE INVENTION
Drive systems for vehicles customarily comprise an internal combustion engine as the driving machine and a subsequent transmission. The transmission plays an important role in operating the engine in its efficient regions and also needs to efficiently transmit power to the wheels, resulting in better fuel economy. Conventionally additional motor-generator is used to operate the system and the engine for further efficiency improvement.
SUMMARY OF THE INVENTION
To operate the engine in its efficient region by making the transmission behave closer to CVT, but having more efficiency than a CVT, with help of a motor-generator and an epicyclic unit.
It is proposed to add a compact and an efficient planetary system, a clutch and an electric motor-generator in between an automated manual / automatic transmission and the internal combustion engine.
andandThe said planetary gear drive encompasses the elements like the sun gear, the internal gear, the planet carrier and staged planet gear sets. Of these elements, the internal gear meshes with staged planet secondary set and is connected to the engine, the planet carrier is bound to the transmission, and sun gear meshes with staged planet primary set and is coupled with the electric motor-generator. The electric motor-generator is of four quadrant type. A clutch is introduced for the lockup or bypass of the planetary gear drive. In an additional arrangement, an additional clutch is provided to disconnect the engine from the driveline. In an additional arrangement, a one way clutch or a lock is provided on the engine crank shaft or the input shaft to the planetary or the internal gear to prevent its anticlockwise rotation for start-stop operation or for the Zero-Emission-Vehicle-operation, that is, powering the vehicle by the electric motor, when the internal combustion engine is not turning. A second motor / generator can be connected to the transmission output shaft / wheels to drive the vehicle during the gear shift operation or supports with additional torque during vehicle acceleration,

launch or supports vehicle braking. A battery / electric energy storage device is provided for storing the elctrical energy produced and reuse it when required.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described, by way of example, with reference to the accompanying
drawings in which:
FIG. 1 is a sketch of the drive system according to the present invention.
FIG. 2 is a sketch of saw tooth curve of vehicle, engine and transmission speeds.
FIG. 3 is a sketch of saw tooth curve of vehicle, engine, transmission and motor-generator
speeds, during the launch and drive mode with a stable engine speed and clutch continuously
open.
FIG. 4 is a sketch of the drive system according to the present invention with a support
motor-generator at the output end of the transmission
FIG. 5 is a sketch of the drive system according to the present invention, with a clutch to
decouple the engine from the input driveline.
FIG. 6A and 6B are sketches of the drive system according to the present invention, with a
one way clutch / lock up clutch in the input driveline.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same
FIG. 1 presents a sketch of the arrangement of the invented system. The prime mover engine (100) drives the crank shaft or flywheel (101). The crank shaft or flywheel (101) is connected to torsional damper system (102), which drives the Input shaft (103). The Input shaft (103) is connected to the Internal gear (109). The planet carrier (104) has at least one staged planet gear set (105). The staged planet gear set (105) is having planet primary gear (106) and planet secondary gear (107) which is integral with each other. The planet secondary gear (107) is smaller in diameter and has lesser number of teeth as compared to the planet primary gear (106). The arrangement of having the planet split into two stages helps in reduced size of the planetary, resulting in reduced inertias, weight, raw material, lubricating oil, speeds, centrifugal forces, centrifugal pressures of oil, fuel, balancing issues and improves

controllability of the transmission. The planet primary gear (106) meshes with the sun gear (108), while the planet secondary gear (107) meshes with the internal gear (109). The sun gear (108) is connected to the motor-generator (111). The planet carrier (104) is connected to the input shaft (112) of the transmission (113). The clutch (110) can couple and decouple the sun gear (108) with the Input shaft (103) by closing and opening the clutch (110) respectively, thereby locking and unlocking the planetary system. In an alternate arrangement, a clutch similar to clutch (110) can couple and decouple the planet carrier (104) with the Internal gear (109) / Input shaft (103) by closing and opening the clutch respectively, thereby locking and unlocking the planetary system. In an another alternate arrangement, a clutch similar to clutch (110) can couple and decouple the planet carrier (104) with the sun gear (108) by closing and opening the clutch respectively, thereby locking and unlocking the planetary system.
Referring to FIG. 1, when the clutch (110) is opened, the engine is directly driving only the Input shaft (103) and the sun gear (108) can have same or different speed as that of the engine (100). In this condition the motor-generator (111) and hence the speed of the sun gear (108) is maintained very low or zero by controlling the motor-generator. This will result in the speed of the Planet carrier (104) and hence the speed of the transmission input shaft (112) becoming less than the speed of the engine (100) to have a lower speed of transmission output. 'R' is the ratio of speed of the engine (100) to the speed of transmission input shaft (112) in the above mentioned situation, that is when the speed of the sun gear (108) is zero and the clutch (110) is open. In actual operation, it is advisable to operate the motor-generator (111) at speeds slightly above zero (for example 100 rpm) that is clockwise (same direction as engine), or slightly below zero (for example -100 rpm) that is counterclockwise, for purposes of supplementing the engine power or charging the battery respectively and also for efficient operation of the system. The planetary gear ratio and hence the ratio R should be such that while operation of the transmission in a particular gear, will result in a drive ratio (ratio of engine output speed to transmission output speed) which is in between the ratios of the current gear and next lower gear of the transmission. For example, when the transmission is in 2" gear, the transmission output speed will become closer to a speed in between the 2" gear and the 1st gear speeds, because of the ratio R. In clutch closed condition, the transmission output speed would be equal to 2" gear speed, because the speeds of the motor-generator, the engine and the transmission input shaft are same in clutch closed condition. In effect if a 6 speed transmission is used, the effective speeds available with this arrangement is

12 speeds. These multiple gear ratio options can help in operating the engine in its efficient regions like a CVT.
Referring to FIG. 2, which shows the example of engine speeds versus vehicle speeds for various gears, open / close conditions of clutch and speeds of the motor-generator. The clutch open condition with sun gear speed controlled will result in ratios lco, 2co, 3co etc. and clutch closed condition will result in ratios lc, 2c, 3c etc. The multiple ratio steps (1c, lco, 2c, 2co, 3c, 3co, ....etc.) result in operating of the engine in efficient region. The fuel efficiency is achieved by operating the engine in efficient region and the clutch open/close conditions with sun gear speed control will manage the required drive ratios. Whereas in the conventional systems with limited drive ratios, the engine needs to work in larger speed ranges to achieve drivability, which will affect fuel economy. The efficient engine operating speed range in this example is between 1450 to 1800 rpm. The engine efficient operating speed range can be determined by engine performance characteristics. Further, the operating range of engine can be modified to user selective operating modes such as sporty, normal and economy to set engine efficient operating speed accordingly for each case.
Referring to FIG 1 and 2 in clutch open state, it is further possible to shift the engine operation to its further efficient regions by having the motor-generator rotate in clockwise direction that is a direction same as the engine rotation. This would improve the fuel economy depending on the engine specific fuel consumption map.
Referring to FIG 1 and 2 in clutch open state, the motor-generator can supplement engine power by having the motor-generator rotate in clockwise direction that is a direction same as the engine rotation. This would further improve the fuel economy.
When the vehicle is being driven with the clutch in open, for the aid of the driving or accelerating and coasting or decelerating of the vehicle, the power and hence the torque on the motor-generator is controlled along with the fuelling control of the engine.
When there is a need to close the clutch, the engine and the motor-generator speeds are made to rapidly approach the transmission input shaft speed, so that the clutch can be closed and the motor-generator can be relieved and the system works in a traditional way - This happens in an extremely short time and without torque interrupt.

In order to get back to the clutch open mode, the motor-generator is made to apply a torque on the sun gear and then the clutch is opened, so that there is no torque interrupt in the driveline.
For a short burst acceleration request while the clutch is open and in an adequate battery situation, the engine and the motor-generator speeds are made to rapidly approach the transmission input shaft speed, when the clutch is closed and the motor-generator assists the engine for vehicle acceleration.
For a short burst acceleration request while the clutch is open and in an inadequate battery situation, a gear downshift is done. Post the downshift the vehicle is driven with the clutch open, if it is found that the driver is still pressing hard the accelerator.
When the clutch is closed, the motor-generator can assist the engine or the brakes by pumping in or drawing out high torques from the driveline.
During vehicle deceleration while the clutch is closed, when the engine speed approaches its idle speed and while the transmission is in 1st gear, the clutch is opened and the motor-generator is controlled for further reduction in vehicle speed requirements.
When the driver is accelerating or decelerating the engine, while in vehicle launch mode by engine and the driver is also applying the vehicle brakes, or in a condition when the vehicle is stationary and the vehicle brakes are applied and the transmission is in a gear and the clutch is open, the engine acceleration or deceleration is assisted by the motor-generator. This is because of the high reflected inertia of the motor-generator felt at the engine and also fuel efficiency.
Referring to FIG lthe method of running the engine at efficient speed with the assistance of motor -generator is explained with help of FIG. 3. It is desirable to run the vehicle, partly by the engine without sweeping the engine across its inefficient speed ranges with the motor-generator (IMG) supplying a significant portion of the power requirement of the vehicle. The graph of FIG. 3 describes such a situation depicting the speeds of the engine, motor-generator (IMG), transmission input shaft and the vehicle. The clutch is open throughout this mode of operation. While the engine speed is not varied much, the transmission input shaft speed and hence the vehicle speed is changed mainly because of changes in motor-generator (IMG)

speed. The gear shifting is also done to further bring about changes in vehicle speed. The speed synchronization for gear shift is done by the motor-generator. The engine speed can additionally be varied when quicker synchronization is needed. The motor-generator normally operates in a speed band B which is in clockwise direction (direction same as the engine) for better fuel economy. The operation of the motor-generator is out of this speed band B only during launch and when the vehicle is stationary.
If the battery is low or if the transmission gear ratio steps are large then the motor-generator would also work in a speed band, which has partial operation of the motor-generator in the clockwise direction and partial operation in counter clockwise direction.
For vehicle launch operation and gear shift operation when the clutch is open, the following sequence of steps are followed
1. Engine speed is is not varied much.
2. If a gear change is needed, then

a) The Torque on the motor-generator is reduced significantly.
b) The current gear is disengaged.
c) The motor-generator speed is varied to change the transmission input shaft speed for synchronization to the next gear. The engine speed can additionally be varied for aiding synchronization when needed.
d) The next gear is engaged.
3. The motor-generator speed and torque is varied for vehicle acceleration and
deceleration. The engine can additionally be used by varying its speed and
torque for aiding quicker acceleration and deceleration of the vehicle.
In the above step 2.c and step 3, the motor-generator operates in a speed band as explained above, i.e in a band B which is in clockwise direction (direction same as the engine) for better fuel economy. The operation of the motor-generator is out of this speed band B only during launch and when the vehicle is stationary.
If the battery is low or if the transmission gear ratio steps are large then the motor-generator would also work in a speed band, which has partial operation of the motor-generator in the clockwise direction and partial operation in counter clockwise direction.
Referring to FIG. 4, presents a sketch of the arrangement of the invented system. The prime mover engine (100) drives the crank shaft or flywheel (101). The crank shaft or flywheel

(101) is connected to torsional damper system (102), which drives the Input shaft (103). The Input shaft (103) is connected to the Internal gear (109). The planet carrier (104) has at least one staged planet gear set (105). The staged planet gear set (105) is having planet primary gear (106) and planet secondary gear (107) which is integral with each other. The planet secondary gear (107) is smaller in diameter and has lesser number of teeth as compared to the planet primary gear (106). The planet primary gear (106) meshes with the sun gear (108), while the planet secondary gear (107) meshes with the internal gear (109). The sun gear (108) is connected to the motor-generator (111). The planet carrier (104) is connected to the input shaft (112) of the transmission (113). The clutch (110) can couple and decouple the sun gear (108) with the Input shaft (103) by closing and opening the clutch (110) respectively, thereby locking and unlocking the planetary system. In an alternate arrangement, a clutch similar to clutch (110) can couple and decouple the planet carrier (104) with the Internal gear (109) by closing and opening the clutch respectively, thereby locking and unlocking the planetary system. In an another alternate arrangement, a clutch similar to clutch (110) can couple and decouple the Internal Gear (109) with the sun gear (108) by closing and opening the clutch respectively, thereby locking and unlocking the planetary system. The additional motor-generator (400) drives the transmission output / the vehicle wheels (401). The additional motor / generator (400) drives the transmission output / vehicle wheels (401) during the gear shift operation and supports with additional torque during vehicle acceleration, launch and supports vehicle braking. Thus the additional motor-generator (400) aids in gear shifting without power interruption, by driving the vehicle momentarily during gear shift operation.
and
If it is necessary to decouple the engine from the drive line the scheme in FIG. 5 is preferred.
Referring to FIG. 5, presents a sketch of the arrangement of the invented system. The prime mover engine (100) drives the crank shaft or flywheel (101). The crank shaft or flywheel (101) is connected to torsional damper system (102), which drives the Input shaft (103). The Input shaft (103) is connected to the Internal gear (109). The planet carrier (104) has at least one staged planet gear set (105). The staged planet gear set (105) is having planet primary gear (106) and planet secondary gear (107) which is integral with each other. The planet secondary gear (107) is smaller in diameter and has lesser number of teeth as compared to the planet primary gear (106). The planet primary gear (106) meshes with the sun gear (108), while the planet secondary gear (107) meshes with the internal gear (109). The sun gear (108)

is connected to the motor-generator (111). The planet carrier (104) is connected to the input shaft (112) of the transmission (113). The clutch (200) can couple and decouple the Input shaft (103) with the torsional damper (102), thereby connecting and disconnecting respectively the Input shaft (103) from the engine (100). The clutch (201) can couple and decouple the sun gear (108) with the Internal gear (109) / Input shaft (103) by closing and opening the clutch (201) respectively, thereby locking and unlocking the planetary system. In an alternate arrangement, a clutch similar to clutch (201) can couple and decouple the planet carrier (104) with the Internal gear (109) / Input shaft (103) by closing and opening the clutch respectively, thereby locking and unlocking the planetary system. In an another alternate arrangement, a clutch similar to clutch (201) can couple and decouple the planet carrier (104) with the sun gear (108) by closing and opening the clutch respectively, thereby locking and unlocking the planetary system. After keeping open the clutch (200) and closing the clutch (201), the vehicle can be launched by the engine (100) by gradually closing the clutch (200). In another method, after keeping open the clutch (200) and closing the clutch (201), the vehicle can be launched by the motor-generator (111), while the engine (100) can be on or off. In another method, after keeping open the clutch (200) and closing the clutch (201), the vehicle can be launched both by the motor-generator (111) and the engine (100) by gradually closing the clutch (200).
Referring to FIG. 6, presents a sketch of the arrangement of the invented system. The prime mover engine (100) drives the crank shaft or flywheel (101). The crank shaft or flywheel (101) is connected to torsional damper system (102), which drives the Input shaft (103). The Input shaft (103) is connected to the Internal gear (109). The planet carrier (104) has at least one staged planet gear set (105). The staged planet gear set (105) is having planet primary gear (106) and planet secondary gear (107) which is integral with each other. The planet secondary gear (107) is smaller in diameter and has lesser number of teeth as compared to the planet primary gear (106). The planet primary gear (106) meshes with the sun gear (108), while the planet secondary gear (107) meshes with the internal gear (109). The sun gear (108) is connected to the motor-generator (111). The planet carrier (104) is connected to the input shaft (112) of the transmission (113). The clutch (110) can couple and decouple the sun gear (108) with the Input shaft (103) by closing and opening the clutch (110) respectively, thereby locking and unlocking the planetary system. A one way clutch (301) connects the crank shaft (101) / Input shaft (103) / internal gear (109) and a stationary housing (300). The one way clutch (301) can also be a friction clutch or dog clutch or a simple lock. When it is needed to

launch and drive the vehicle purely by the motor (111) and also using the planetary gears for motor torque multiplication or speed reduction, while the engine (100) is stationary, this one way clutch or friction clutch (301) at the engine crank.shaft (101) / Input shaft (103) / internal gear (109) prevents the crank shaft (101) / Input shaft (103) / internal gear (109) from rotating anticlockwise direction so as to aid the motor (111) to launch and drive the vehicle for zero emission operation.
The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

We Claim:
A method for delivering power to the driven wheels of a vehicle through a vehicle drive system having a planetary system coupled to a driving engine output shaft, a first motor-generator coupled to the sun gear of the said planetary system, a transmission coupled between said planetary system and said driven wheels, a clutch configured to selectively lock the planetary gear system, to bypass the planetary system function, comprising the steps of;
a) selectively operating the clutch to lock or unlock the planetary gear system,
b) operating the motor-generator in clock wise or anti-clock wise direction in clutch open condition,
c) controlling the speed of the motor-generator predominantly in a predetermined band (B) or in predetermined speed close zero in clutch open condition.

2. The method as claimed in claim 1, wherein the internal gear of the planetary system is coupled to the driving engine output shaft and the planet carrier of the planetary system is connected to the transmission, wherein the motor-generator is operating in the band (B) predominantly in clockwise direction whereby the motor-generator (IMG) supplying a significant portion of the power requirement of the vehicle.
3. The method as claimed in claim 2 wherein a change in the transmission gear comprising further steps of

a) reducing the torque on the motor-generator,
b) disengaging the current gear of the transmission,
c) controlling the motor-generator speed to change the transmission input shaft speed for synchronization to the next gear,
d) engaging the next gear of the transmission.
4. The method as claimed in claim 1 wherein the internal gear of the planetary system is
coupled to the driving engine output shaft and the planet carrier of the planetary system is
connected to the transmission, wherein in the clutch open condition the motor generator is
operated at close to zero to achieve a drive ratio of the system in-between the current
transmission gear ratio and the next lower ratio of the transmission.

5. The method as claimed in any one of the preceding claims 1,2, and 4 wherein said motor-generator speed is depended on the efficiency of the motor-generator and the drive system.
6. The method as claimed in any one of the preceding claims wherein the engine speed can additionally be varied for aiding synchronization of the transmission gears.

7. The method as claimed in claim 1 further comprising a step of; loading the motor-generator before opening the clutch.
8. The method as claimed in any one of the preceding claims wherein a second motor-generator drives the transmission output / the vehicle wheels.
9. The method as claimed in any one of the preceding claims wherein the planet gear includes a planet primary gear and a planet secondary gear.