CLIAMS:1. A drive train (100) for a hybrid vehicle, the drive train (100) comprising:
an input shaft (102) selectively engageable with at least one of an engine (200) and an electric motor (300);
a planetary gear assembly (150) mounted on the input shaft (102), wherein the planetary gear assembly (150) is configured to provide variable gear ratio to wheels (502) of the vehicle, the planetary gear assembly (150) comprises:
a sun gear (103) fixed to the input shaft (102);
a ring gear (105) mounted concentric to the sun gear (103), wherein the ring gear (105) is configured to selectively engage with the input shaft (102);
a plurality of planet gears (104) provided in between the sun gear (103) and the ring gear (105), wherein the plurality of planet gears (104) are in meshing engagement with the sun gear (103) and the ring gear (105) and are configured to rotate and revolve around the sun gear (103); and
a planet carrier (106) comprising a first end and a second end, wherein the first end of the planet carrier (106) is pivotally connected to the plurality of planet gears (104), and second end of the planet carrier (106) is coupled to an output shaft (107);
wherein, the planet carrier (106) is configured to transmit the power from the planetary gear assembly (150) to the output shaft (107).

2. The drive train (100) as claimed in claim 1 comprises of a first clutching mechanism (110) provisioned in between the engine (200) and the input shaft (102).

3. The drive train (100) as claimed in claim 2, wherein the first clutching mechanism (110) is configured to selectively engage the input shaft (102) with the engine (200).

4. The drive train (100) as claimed in claim 1, wherein the variable gear ratio includes a first gear ratio and a second gear ratio.

5. The drive train (100) as claimed in claim 1 comprises of at least one braking mechanism (130) to selectively inhibit rotation of the ring gear (105).

6. The drive train (100) as claimed in claim 1, wherein the planetary gear assembly (150) provides a first gear ratio when rotation of the ring gear (105) is inhibited by at least one braking mechanism (130).

7. The drive train (100) as claimed in claim 1 comprises of a second clutching mechanism (120) provisioned in between the ring gear (105) and the input shaft (102) to selectively engage the ring gear (105) with the input shaft (102).

8. The drive train (100) as claimed in claim 1, wherein the planetary gear assembly (150) provides a second gear ratio when the ring gear (105) is engaged with the input shaft (102) by a second clutching mechanism (120).

9. The drive train (100) as claimed in claim 1, wherein the electric motor (300) is connected to a power source.

10. The drive train (100) as claimed in claim 9, wherein the power source is electric battery.

11. The drive train (100) as claimed in claim 1 comprises of a torque converter (with normally closed lock up clutch) unit (600) provisioned in between the engine (200) and the input shaft (102).

12. The drive train (100) as claimed in claim 1, wherein the torque converter unit (600) is configured to provide torque amplification to the input shaft (102).

13. The drive train (100) as claimed in claim 1, wherein the electric motor (300) is configured to restore energy in the power source during vehicle braking.

14. The drive train (100) as claimed in claim 1, wherein the engine (200) is configured to drive the electric motor (300) when the vehicle is stationary.

15. The drive train (100) as claimed in claim 1, wherein the input shaft (102) is driven by the electric motor (300) when the vehicle speed is lesser than a predetermined speed.

16. The drive train (100) as claimed in claim 1, wherein the input shaft (102) is driven by the combination of the electric motor (300) and the engine (200) when vehicle speed is higher than a predetermined speed.

17. The drive train (100) as claimed in claims 15 and 16, wherein predetermined speed of the vehicle ranges from 0 kilometre per hour to 50 kilometre per hour.

18. The drive train (100) as claimed in claim 1, wherein the input shaft (102) is driven by the engine (200) when energy level in the power source is lesser than a predetermined limit.

19. The drive train (100) as claimed in claim 1 comprises of an air-conditioning compressor (400) coupled to the input shaft (102).

20. The drive train (100) as claimed in claim 19, wherein the air-conditioning compressor (400) is driven by at least one of engine (200) and electric motor (300).

21. The drive train (100) as claimed in claim 1, wherein a first clutching mechanism (110), a second clutching mechanism (120), and a braking mechanism (130) are interfaced with a control unit.

22. A hybrid vehicle comprising a drive train (100) as claimed in claim 1.
,TagSPECI:TECHNICAL FIELD
The present disclosure generally relates to a field of automotive engineering. Particularly, but not exclusively the disclosure relates to hybrid vehicle. Further, embodiments of the present disclosure disclose a drive train of the hybrid vehicle.

BACKGROUND
It is known that most of the vehicles are propelled by Internal Combustion (I.C) engines in which a fuel is burnt in the presence of air. A fuel is basically a combustible substance comprising hydrocarbons and capable of releasing large amount energy in the form of heat. In other words, the chemical energy stored in the fuel can be converted into thermal energy by burning it in the presence of air. This chemical process is called combustion. The heat released by combustion of fuel is utilized to run the engine which in turn drives wheels of the vehicle, providing a thrust to vehicle in forward and reverse directions. Thus, an I.C engine can be considered as a power plant which converts chemical energy of the fuel into thermal energy used to power drive wheels of the vehicle. I.C engines have been preferred mode of power source which were used to propel vehicles, for all these years, and still continue to be for coming years. This is because, power developed inside an engine by burning small quantity of fuel is considerably high and has potential to keep the vehicle in motion for a longer time. However, there are some undesirable issues with I.C engines such as emission of harmful gases including but not limiting to NOX, CO, CO2 and lead particles. These exhaust gases not only pose a threat to human and animal health, but also have significant adverse effects on biosphere as a whole and on various levels of atmosphere. Considerable efforts are being made for years to reduce concentration of these gases in exhaust of vehicles. However, with the number of vehicles increasing day by day, reduction in quantity of exhaust gases being let into atmosphere to safe/permissible levels has been a great challenge. In addition to hydrocarbon emissions, I.C engines also require frequent maintenance in terms of cooling, lubrication and timely replacement of few parts to ensure their long term operability. This is another major concern associated with usage of I.C engines which needs to be taken care of from time to time, for its proper functioning.

In recent past, vehicle manufacturers have shifted their focus to develop an engine which emits exhaust gases within safe/permissible limits. Parallelly, focus has also been laid on developing vehicles which do not make use of an I.C engine, but make use of alternate power sources such as electricity, wind, solar and the like. With the usage of these alternate power sources to drive vehicles, problems associated with emission of exhaust gases can be completely eliminated, as no hydrocarbon fuel is burnt. In addition, the vehicles operated by electric power do not require extra attention for maintenance unlike the conventional I.C engine driven vehicles. These vehicles make use of one or more electric motors to power drive wheels, and the electric motors are connected to a power source such as one or more batteries. Alternatively, the electric motor can also switch to a generator mode so that it generates electricity and charges the battery, when battery state of charge (hereinafter referred to as SOC) goes below a minimum value. Thus, it can be said that the electric motor is integrated with generator (i.e. capable of operating as generator at one instant and as a motor at another instant) so that it drives the vehicle by consuming power from the battery, and conversely, charges the battery whenever need arises. If vehicle is to be propelled by solar or wind power, a solar panel or a wind turbine is used to increase battery SOC.

However, there are also few limitations associated with electrically operated vehicles such as limited operability of battery over course of time (i.e. limited shelf life), requirement of two or more batteries, preferably batteries connected in series which provide more power to the motors to meet high accelerating condition (cruising range) of the vehicle, and also to keep vehicle in motion for a long time. Again, with incorporation of two or more batteries in the vehicle, the compactness reduces and weight increases. Since electric motors do not provide sufficient torque to propel the vehicle, an increase in weight owing to increase in number of batteries is not desirable. Another problem linked with usage of batteries is its limited capacity to operate under an overload state. To overcome the problems associated with both engine propelled and electrically propelled vehicles, the vehicle manufacturers developed a new type of vehicle by incorporating few features of engine operated vehicles and few features of electrically propelled vehicles. This new vehicle was named “hybrid vehicle” and was powered both by I.C engines and electric motors. Though these vehicles significantly improve fuel economy and reduce exhaust gas emission, there are number of limitations associated with them such as increase in overall size, weight and operating cost, owing to requirement of two or more electric motors and batteries. In addition, to provide different gear ratios, complex gear arrangements and CVTs (Continously Variable Transmission) are used which again increases cost of operation. Also, these vehicles use air-conditioning units whose power requirement is entirely met by batteries, which again increased overall size and weight of the vehicles.

In light of foregoing discussion, it is necessary to develop an improved drive train for a hybrid vehicle, to overcome one or more limitations stated above.

SUMMARY OF THE DISCLOSURE
The one or more drawbacks of conventional drive trains as described in the prior art are overcome and additional advantages are provided through the system as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be a part of the claimed disclosure.

In one non-limiting embodiment of the present disclosure, there is provided a drive train for a hybrid vehicle. The drive train comprises an input shaft selectively engageable with at least one of an engine and an electric motor. A planetary gear assembly is mounted on the input shaft, wherein the planetary gear assembly is configured to provide variable gear ratio to wheels of the vehicle. The planetary gear assembly comprises a sun gear fixed to the input shaft, a ring gear mounted concentric to the sun gear, wherein the ring gear is configured to selectively engage with the input shaft, and a plurality of planet gears provided in between the sun gear and the ring gear. The plurality of planet gears are in meshing engagement with the sun gear and the ring gear and are configured to rotate and revolve around the sun gear. Further, the planetary gear assembly comprises a planet carrier comprising a first end and a second end, wherein the first end of the planet carrier is pivotally connected to the plurality of planet gears, and second end of the planet carrier is coupled to an output shaft. The planet carrier is configured to transmit the power from the planetary gear assembly to the output shaft.

In an embodiment of the present disclosure, a first clutching mechanism is provisioned in between the engine and the input shaft. The first clutching mechanism is configured to selectively engage the input shaft with the engine.

In an embodiment of the present disclosure, the variable gear ratio includes a first gear ratio and a second gear ratio.

In an embodiment of the present disclosure, at least one braking mechanism is configured to selectively inhibit rotation of the ring gear. Further, the planetary gear assembly provides a first gear ratio when rotation of the ring gear is inhibited by at least one braking mechanism.
In an embodiment of the present disclosure, a second clutching mechanism is provisioned in between the ring gear and the input shaft to selectively engage the ring gear with the input shaft. Further, the planetary gear assembly provides a second gear ratio when the ring gear is engaged with the input shaft by the second clutching mechanism.

In an embodiment of the present disclosure, the electric motor is connected to a power source and the power source is electric battery.

In an embodiment of the present disclosure, a torque converter unit is provisioned in between the engine and the input shaft. The torque converter unit is configured to provide variable torque ratio to the input shaft.
In an embodiment of the present disclosure, the electric motor is configured to restore energy in the power source during vehicle braking.

In an embodiment of the present disclosure, the engine is configured to drive the electric motor when the vehicle is stationary.

In an embodiment of the present disclosure, the input shaft is driven by the electric motor when the vehicle speed is lesser than a predetermined speed and the input shaft is driven by the combination of the electric motor and the engine when vehicle speed is higher than a predetermined speed. The predetermined speed of the vehicle ranges from 0 to 50 kilometre per hour.

In an embodiment of the present disclosure, the input shaft is driven by the engine when energy level in the power source is lesser than a predetermined limit.

In an embodiment of the present disclosure, an air-conditioning compressor coupled to the input shaft. The air-conditioning compressor is driven by at least one of engine and electric motor.

In an embodiment of the present disclosure, a first clutching mechanism, a second clutching mechanism, and a braking mechanism are interfaced with a control unit.

It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the disclosure.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
The novel features and characteristics of the disclosure are set forth in the appended description. The disclosure itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:

FIG. 1 illustrates the schematic view of a topology of a hybrid vehicle with drive train, according to an embodiment of the present disclosure.

FIG. 2 illustrates planetary gear assembly along with first and second clutching mechanisms and a braking mechanism in the hybrid vehicle, according to an embodiment of the present disclosure.

FIG. 3 illustrates schematic front view of torque converter unit incorporated in the drive train of hybrid vehicle, according an embodiment of the present disclosure.

FIGS. 4A, 4B, 4C and 4D illustrate various modes of operation drive train in the hybrid vehicle, according to some embodiments of the present disclosure.

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION
The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the claims of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the scope of the disclosure as set forth in the appended claims. The novel features which are believed to be characteristic of the disclosure, both as to its assembly and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.

To overcome one or more limitations stated in the background, the present disclosure provides a drive train of a hybrid vehicle. The hybrid vehicle is essentially a two way powered vehicle which derives power from an Internal Combustion (I.C) engine as well as from an electric motor. When power from both engine and electric motor is used to propel the vehicle, the mode is called “hybrid mode”, and when vehicle is driven by motor alone, the mode is called “pure electric mode”. The mode at which the vehicle is to be run is decided based on whether the vehicle requires more speed or torque or both, which is brought about by drive train and other associated mechanisms of vehicle.

Hybrid vehicles are classified into parallel configuration and series configuration hybrid vehicles. The classification is made based on location of power sources (i.e. engine and battery) with respect to longitudinal axis of the vehicle. In parallel configuration, engine and electric motor are placed such that speed available at the transmission shaft (i.e. propeller shaft) are identical and torque transmitted from engine and electric motor add up i.e. resultant or net power at transmission shaft will be sum of powers transmitted by engine and electric motor. In series configuration, motor is not integrated with generators but is placed as separate unit in the vehicle with battery present in between them. In addition, engine is mechanically disconnected from drive wheels so that drive wheels are powered entirely by electric motor, by consuming power either from generator or from battery or a combination of both. When battery SOC goes below a minimum value, electricity produced by generator restores charge in the battery. Thus in series hybrid configuration, battery serves as primary power source to rotate drive wheels via motor, and generator serves as secondary or auxiliary source of power.

Hybrid vehicles, as described above, are capable of running in three different drive modes i.e. hybrid mode, engine mode and pure electric mode, depending on speed and load conditions. If the vehicle is to be propelled on a plain/flat road with moderate speed, the mode is switched to pure electric mode. During pure electric mode, engine operation is isolated from the drive train and power required to drive wheels of the vehicle is entirely supplied by electric motor operated by batteries. On the other hand, when vehicle is to be propelled on elevated planes or on paths where drive wheels require more torque to propel the vehicle, the transmission is changed to hybrid mode. During hybrid mode, power from I.C engine as well as from electric motor is supplied to drive wheels, owing to the fact that pure electric mode alone will not be able to provide sufficient torque to propel the vehicle on such elevated planes. Similarly, if vehicle is to be driven in cruising speeds/high accelerating conditions on a plane/flat road, the transmission is again shifted to hybrid mode. This changeover from pure electric mode to hybrid mode and vice versa is effected through the transmission system or drive train of the hybrid vehicle, which is explained in detail with reference to figures and referral numerals in forthcoming paragraphs of the detailed description. Further, the drive train is also configured to operate in an engine mode, where drive wheels of the vehicle are powered entirely by the engine.

The drive train of hybrid vehicle essentially comprises of an I.C engine, which is first source of power used to propel the vehicle, and an electric motor, which serves as second source of power and capable of operating in conjunction with the I.C engine as well as independent of it. The electric motor is powered by power supply units such as one or more batteries. Generally, electric motor also reversibly operates as generator to restore energy in the power supply unit. This is because, with the consumption of battery power to run the vehicle in pure electric mode and hybrid mode, battery SOC comes below a minimum value so that it will no longer be able to power electric motor, thereby arises the need to restore energy (or charge) in it. Since in hybrid vehicles much of focus is laid on reducing weight and increasing compactness, the motor is either integrated with generator or configured such that it reversibly operates as electric generator. Further, the motor can operate in two different modes – a first mode called starter motor mode and a second mode called traction motor mode. The starter motor serves the purpose of providing starting torque to the engine during cranking, which is very much necessary during transition from pure electric mode to hybrid mode. In the second mode i.e. traction motor mode, it provides power to drive wheels of the vehicle. In either mode, the motor consumes power from power sources such as batteries. The drive train also comprises of a planetary gear assembly configured to provide variable gear ratio between the power plants (engine and electric motor) and the drive wheels of hybrid vehicles, through an input shaft. The planetary gear assembly is mounted on the input shaft and comprises of a sun gear and a ring gear which are concentric with each other and capable of rotating about a common axis. The sun gear rotates with the input shaft, while the annular gear rotates with the input shaft as well as independent of the input shaft. A plurality of planet gears are provided in between the ring gear and the sun gear. The plurality of planet gears are in meshing engagement with sun gear on one side and with ring gear on other side. The plurality of planet gears are carried by a planet carrier which supports revolving movement of the planet gears. In addition, the planet gears are capable of rotating about their own axes. Variable gear ratios are achieved through a second clutching mechanism and a braking mechanism. A first gear ratio is achieved by inhibiting the rotation of ring gear by the braking mechanism, so that rotation of sun gear revolves planet gears and therefore the planet carrier. The planet carrier, which is coupled to an output shaft, transfers power to it. The output shaft in turn transmits this power to drive wheels through differential. Similarly, a second gear ratio is transmitted by engaging the ring gear with the input shaft so that ring gear and sun gear rotate with same angular speed. This causes planet gears and the planet carrier to rotate with same speed as that of sun and ring gears, which subsequently rotates the output shaft. The output shaft transfers this power to drive wheels corresponding to a second gear ratio. The drive train also comprises a torque converter unit, an air conditioning unit, a drive train and wheel axle-differential assembly which will be reflected in subsequent paragraphs of detailed description.

Use of terms such as “comprises”, “comprising”, or any other variations thereof in the description, are intended to cover a non-exclusive inclusion, such that a setup system, device or method that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a mechanism proceeded by “comprising… a” does not, without more constraints, preclude the existence of other elements or additional elements in the mechanism.

Reference will now be made to a drive train of a parallel configuration hybrid vehicle, and is explained with the help of figures. The figures are for the purpose of illustration only and should not be construed as limitations on the mechanism. Wherever possible, referral numerals will be used to refer to the same or like parts.

FIG. 1 is an exemplary embodiment of the disclosure which illustrates schematic view of a drive train in the hybrid vehicle. The drive train (100) essentially comprises of an engine (200) which is the power plant of the vehicle, and intended to impart necessary torque to drive wheels (502). The engine (200) also serves as an auxiliary power generating unit which restores energy in power source which drives an electric motor (300). The engine (200) as is well known to a person skilled in the art, comprises of at least one piston (not shown) which reciprocates in a cylinder under explosive pressure of combustion gases, and a crankshaft (not shown) capable of rotating and connected to at least one piston via at least one connecting rod (not shown) and crank (not shown). The rotary motion of crankshaft produces torque and speed (altogether power) to rotate drive wheels (502) of the vehicle, causing propulsion of vehicle in forward and reverse direction. In an embodiment of the present disclosure, the engines include but not limiting to single cylinder and multicylinder gasoline and diesel engines. Transmission of power from engine (200) to drive wheels (502) takes place through transmission system of the vehicle, and can be considered as intermediate power delivering unit between the engine (200) and drive wheels (502). The transmission system drives wheel axles (501) through an intermediate gear train called differential (500). In other words, axles (501) are interconnected through a differential gear train (500). In an exemplary embodiment of the disclosure, the differential gear train (500), as is well known, comprises of a pair of side gears mounted on the pair of axles (left and right axles), and positioned such that they are faced opposite to each other, with axes of the right and left axles co-inciding. An annular gear, also called crown gear (not shown) is placed adjacent (concentrically) to one of the side gears on an axle (501) and can rotate independent of rotation of the axle (501). The annular gear meshes with driving gear mounted on outermost shaft of the transmission system, and thereby transmits power to drive the axles (501). Further, the side gears are inter-connected by two or more pinions (spider gears) (not shown) whose axes are perpendicular to the co-inciding axes of the axles (501). When annular gear rotates, the pinions start revolving about co-inciding axes of the axles (501) which in turn cause rotation of the differential side gears, thereby providing required power to rotate the axles (501) of the vehicle. The rotation of axles provides a thrust to the vehicle, which propels the vehicle in forward and reverse direction. In an embodiment of the present disclosure, the axles of the vehicle includes but not limiting to semi-float axle and full float axles. The differential mechanism explained above is with respect to rear wheel drive type hybrid vehicles, and the same should not be construed as only possible configuration. A person skilled in the art may vary the configuration depending on the type of drive of the vehicle, and is not in any way limiting the scope of the disclosure.

The drive train (100) further comprises of an electric motor (300) connected to a power source (not shown). The power source supplies power to operate the electric motor (300) as and when required. In an embodiment of the present disclosure, the power source includes but not limiting to an electric battery and an electric grid. The electric motor (300), as described above, is also configured to operate as an electric generator depending on the requirement. Further, the electric motor (300) is configured such that it selectively operates in four different modes- a drive mode, a charging mode, a non-load state and a starter mode. Working of each of these modes is as follows: In first mode, i.e. in drive mode, the electric motor (300) is driven by electric power supplied by the power source and transmits power to the drive train (100) during pure electric mode (shown in FIG. 4A) as well as in hybrid mode (shown in FIG. 4B). In second mode, i.e. in charging mode, the electric motor (300) functions as a generator to generate power which is supplied to power source. In other words, in charging mode, the electric motor (300) operates as a power generating unit producing energy which is used to restore energy level in the power source (as shown in FIG. 4D). In third mode, i.e. in non-load mode, the output shaft of the electric motor (300) is permitted to rotate freely. This mode is rarely used. In last mode, i.e. in starter mode, the electric motor (300) is used to provide starting torque to the engine (200) when transmission is shifted from pure electric mode to hybrid mode (as shown in FIG. 4c). In addition, the direction of rotation of motor (300) can also be changed by means of reverse engagement switches. This is required when vehicle is to be moved in reverse direction. In an embodiment of the present disclosure, the electric motor includes but not limiting to high capacity DC (direct current) motors.

The drive train (100) also comprises of an air-conditioning unit (not shown) which is used to modulate temperature of vehicle cabin, including but not limiting to passenger compartment based on the requirement. The working principle of a conventional air-conditioning unit is well known and is not explained in detail in the detailed description. However, the working principle is explained in brief as follows: the air conditioning unit comprises of a compressor (400), an evaporator (not shown), a blower or a fan (not shown), a condenser (not shown) and an expansion valve (not shown). Of these components, compressor (400) is the unit which consumes power to operate, and hence is connected to engine (200) as well as to the electric motor (300) through input shaft (102). The refrigerant vaporizes by absorbing heat from air, which is used to cool passenger compartment. The conditioned air is circulated back into the passenger compartment by the blower or fan. The refrigerant in vaporized condition is then compressed to high temperature and pressure by the compressor (400) and is circulated into condenser unit, where it condenses by losing heat to atmosphere. It is then allowed to expand to low pressure and temperature in expansion valve, and the cycle repeats. Since compressor (400) unit operates continuously to compress vaporized refrigerant to high temperatures and pressures, it needs power to operate, which is supplied either by the engine (200) or by the motor (300) or combination of engine and the motor. In an embodiment of the present disclosure, air-conditioning compressor includes but not limiting to a reciprocating and centrifugal compressor. If energy level in the power source (battery) is high, the electric motor (300) generates power sufficient to fulfil power requirement of the compressor (400) to operate. If energy level in power source is low, the engine (200) is engaged so that it operates the air-conditioning compressor through transmission and keeps the air-conditioning unit running regardless of the energy level in the power source. Engine can provide power to run air conditioning compressor as well as for electric motor to charge the battery if needed. A/C compressor is connected to the input shaft (102) through a gear. Whenever vehicle is running, input shaft (102) gets the power from power plant (either engine or electric motor or both), which can be used to drive air-conditioning compressor as well.

When vehicle is stationary, planet carrier (106) gets locked through vehicle inertia and wheel braking. Ring gear (105) is allowed to rotate by opening the braking mechanism (130) and second clutching mechanism (120) remains open. If energy level in power source is high, electric motor (300) will run at constant speed and provide the power just sufficient to fulfil air-conditioning compressor (400) power requirement. If energy level in power source is low, engine (200) will be coupled to input shaft (102) by closing the first clutching mechanism (110) and run in IDLE speed control mode to provide the power to run air-conditioning compressor (400). Air-conditioning works in similar way during energy restoring of power source. Lock up clutch (605) of torque converter (600) remains closed when air-conditioning unit is on and vehicle is stationary
FIG. 2 is an exemplary embodiment of the present disclosure which illustrates schematic view of the planetary gear assembly (150) along with first and second clutching mechanisms and a braking mechanism. The planetary gear assembly (150) comprises of an input shaft (102) which is the main shaft designed to transmit power from the power plants, i.e. engine (200), and electric motor (300) to drive wheels. The input shaft (102) is also designed taking into consideration the various types of loadings to which it may be subjected during power transmission. Mainly, the input shaft (102) should have necessary dimensions to withstand torsional moments, especially when it operates in the hybrid mode.

As shown in FIG. 2, the planetary gear assembly (150) is mounted on the input shaft (102) so that speed ratio between the input shaft (102) and wheel axles (501) can be varied. A variation in speed ratio also indicates a variation in torque ratio between them. The term speed ratio is defined as ratio of angular speed of the input shaft (102) to the angular speed of wheels axles (501). The variation in speed ratio is achieved by varying the configuration of planetary gear assembly (150), which is usually done by changing degree of freedom of constituting gears in the planetary gear assembly (150). The planetary gear assembly (150) essentially comprises of a sun gear or a solar gear (103) which is fixed to input shaft (102). The sun gear (103) can have only one degree of freedom i.e. it can only rotate along with the input shaft (102). In an embodiment of the present disclosure, the sun gear (103) is fixed to the input shaft (102) by mechanical elements including but not limiting to keys. The sun gear (103) is surrounded by a plurality of planet gears (104) in such a way that the teeth on plurality of planet gears (104) are in meshing engagement with the teeth on sun gear (103). In addition, the plurality of planet gears (104) are configured such that they can rotate about their respective axes well as revolve around the sun gear (103) (i.e. revolve about axis of input shaft (102)). Thus, planet gears (104) have two degrees of freedom. Further, a ring gear (105) is mounted concentrically to the sun gear (103) such that the plurality of planet gears (104) are in meshing engagement with the ring gear (105) on the outer side. In other words, the plurality of planet gears (104) are provisioned in between the sun gear (103) and ring gear (105) such that they mesh with sun gear (103) on one side and ring gear (105) on the other side. The type of meshing engagement between the sun gear (103) and plurality of planet gears (104) is external meshing, i.e. they rotate in opposite direction, while the type of meshing between the planet gears (104) and the ring gear (105) is internal, i.e. they rotate in same direction. The ring gear (105) can rotate independent of the input shaft (102) and can also rotate with the input shaft (102) through an intermediate clutch mechanism. The speed of rotation of each of these gears depends on number of teeth or diameter on each of them. The planetary gear assembly (150) further comprises a planet carrier (106) provided to support the orbiting movement (or revolution) of the plurality of planet gears (104) around the sun gear (103). The planet carrier (106) comprises of a first end which is pivotally connected to the plurality of planet gears (104) and a second end which is connected to an output shaft (107). When plurality of planet gears (104) revolve around the sun gear (103), the planet carrier (106) starts rotating and thereby transmits motion or power to the output shaft (107). The output shaft (107), which is connected to the planet carrier (106), transmits power to the differential (500) so that required torque is available at the differential (500) to drive the axles (501) and therefore to the drive wheels. In an embodiment of the present disclosure, the output shaft (107) is connected to the differential (500) by gearing arrangement including but not limiting to spur gears.

Further, as shown in FIG. 1, a first clutching mechanism (110) is provided in between the input shaft (102) and the engine (200). The first clutching mechanism (110) is configured to selectively engage the input shaft (102) with the engine (200). When the first clutching mechanism (110) is engaged, a connection is established between the engine (200) and the input shaft (102) which causes the rotation of input shaft (102). On the other hand, when clutch (110) is disengaged, the engine (200) is detached or isolated from the input shaft (102). During this condition (i.e. disengaged condition), the engine (200) will not have any influence on the rotation of input shaft (102). The first clutching mechanism (110) is very much necessary when mode of transmission needs to be changed from hybrid to pure electric mode, and vice versa.

The planetary gear assembly (150) is further provided with a second clutching mechanism (120) in between the ring gear (105) and input shaft (102), to selectively engage the ring gear (105) with the input shaft (102). When second clutching mechanism (120) is engaged, the ring gear (105) rotates along with input shaft (102), and when it is disengaged, the ring gear (105) is free to rotate independent of input shaft (102). In addition to this clutching mechanism, a braking mechanism (130) is provided at the periphery of the ring gear (105) to selectively inhibit the rotation of the ring gear (105). The braking mechanism (130) completely arrests the rotational motion of the ring gear (105) upon actuation, and allows rotation of the ring gear (105) when it is not activated. Both second clutching mechanism (120) and braking mechanism (130) are included in the drive train (100) to provide variable gear ratios to the output shaft (107) and in turn to the drive wheels (502) of the vehicle. In an embodiment of the present disclosure, the variable gear ratios include but not limiting to a first gear ratio (hereinafter referred to as FGR) and a second gear ratio (hereinafter referred to as SGR). The FGR is achieved by actuating the braking mechanism (130) so that rotation of the ring gear (105) is completely inhibited. In this condition, the input shaft (102) is rotated only by motor (300) (pure electric mode) or by the combination of both motor (300) and engine (200) (pure hybrid mode). This causes rotation of sun gear (103) which in turn causes revolution of plurality of planet gears (104), with ring gear (105) remaining stationary. The planet carrier (106) rotates with the planet gears (104) and transmits power in accordance with FGR to the output shaft (107). In an embodiment of the present disclosure, the FGR is a high gear ratio. On the other hand, the SGR is achieved by deactivating (or releasing) the braking mechanism (130) and engaging the second clutching mechanism (120) so that ring gear (105) is locked to the input shaft (102). This causes ring gear (105) and the sun gear (103) to rotate with same speed, which causes rotation of planet gears. Planet carrier (106) rotates with subsequently the same speed as that of the sun gear (103) and the ring gear (105), and thereby transmits power or motion to the output shaft (107). This corresponds to second gear ratio SGR of the planetary gear assembly (150). In this way, variable gear ratios are transmitted from the input shaft (102) to the wheels (502) via planetary gear assembly (150). In an embodiment of the present disclosure, the first clutching mechanism (110), the second clutching mechanism (120) and the braking mechanism (130) are interfaced with a control unit including but not limiting to a microprocessor and a microcontroller.

Now, referring back to FIG. 1, different modes in which the hybrid vehicle is configured to operate are described as follows:

Hybrid mode (Both engine and electric motor are engaged with input shaft):
When load on the vehicle is high or when vehicle is to be propelled at higher speeds (i.e. above predetermined speed range), both engine (200) and electric motor (300) will drive the input shaft (102) with required speed and torque. During hybrid mode, the first clutching mechanism (110) is engaged so that the engine (200) will remain engaged with the input shaft (102). The gear ratio can be selected by appropriately operating the second clutching mechanism (120) or the braking mechanism (130) depending on whether vehicle is to be propelled at high speed or at low speed. This mode is clearly shown in FIG. 4B (where power transfer is shown by arrow marks)
Pure electric mode (Engine is isolated and electric motor alone is engaged with input shaft):
When energy level in the power source is sufficiently high, and the vehicle runs in pure electric mode upto certain speed and load. During this mode, engine (200) is isolated from the input shaft (102) by disengaging the first clutching mechanism (110). The engine (200) may be switched off during this condition. The gear ratio can be selected by appropriately operating the second clutching mechanism (120) or the braking mechanism (130) depending on whether vehicle is to be propelled at high speed or at low speed. This mode is clearly shown in FIG. 4A (direction of power transfer is shown by arrow marks)

Restoring energy in the power source when vehicle is stationary:
If energy level in the power source is very less, it can be restored when the vehicle is stationary. This can be achieved by engaging the first clutching mechanism (110) so that engine drives the input shaft (102). Simultaneously, the second clutching mechanism (120) and braking mechanism (130) are disengaged, allowing the ring gear (105) to rotate freely. Since vehicle is stationary, the planet carrier (106) cannot rotate and therefore, no power is transmitted to the output shaft (107). Also, since energy level in power source is lesser than predetermined limit, the motor (300) cannot rotate. In this condition, the motor (300) reversibly changes to power generating mode, i.e. functions as a generator (300). The power rendered to the input shaft (102) by the engine (200) is entirely utilized to drive the generator (300) which produces energy which is supplied to the power source, thereby restoring energy level in it. This mode is clearly shown in FIG. 4D (direction of power transfer is shown by arrow marks).

Regenerative braking:
During vehicle braking, the hybrid vehicle enters into regenerative braking mode. The first clutching mechanism (110) will be disengaged so that the engine (200) is detached from transmission. When vehicle is moving in forward direction and suddenly if it is to be stopped, the driver applies brakes on wheels (502) of the vehicle. But the rotation of input shaft (102) will not stop as soon as brake is applied, rather stops after travelling to some distance. This extra rotation of input shaft (102) after brake is applied is utilized in a constructive manner as follows: As soon as the as brake is applied on wheels (502) of the vehicle by pressing the brake pedal, the electric motor (300) changes to generator mode. The input shaft (102) which continues to rotate even after brake is applied is used to drive the generator to produce power, which is stored in the power source. This restores the spent energy in power source and continues until the input shaft (102) comes to rest completely.

Transition from hybrid mode to pure electric mode:
When the vehicle is moving in hybrid mode, and if much speed is not required, the transmission can be changed such that the vehicle changes from hybrid mode to pure electric mode. This is effected through the first clutching mechanism (110) in between the engine (200) and the input shaft (102). The clutch (110) is disengaged so that the engine (200) is detached from the input shaft (102) and it is powered entirely by the electric motor (300). This continues till energy level in power source is sufficient to power the electric motor (300) and more speed is not required.

Transition from pure electric mode to hybrid mode:
If transition from pure electric mode to hybrid mode is desired, the engine (200) is cranked either by a separate starter motor, or by the electric motor (300) (as shown in FIG. 4C) by engaging the first clutching mechanism (110). Once engine (200) starts operating in full fledge, the gear ratio is selected by operating second clutching mechanism (120) or the braking mechanism (130).

Engine cranking by electric motor:
In hybrid vehicles, engine (200) can be cranked by electric motor (300) to provide starting torque to it, whenever mode is shifted from pure electric mode to hybrid mode as well as when vehicle is to be driven in pure engine (200) mode. To achieve this, the braking mechanism (130) and second clutching mechanism (120) are disengaged, and gradually the first clutching mechanism (110) is engaged. The electric motor (300) will provide the torque necessary to crank the engine (200).

FIG. 3 illustrates schematic front view of torque converter unit (600) incorporated in the drive train (100) of hybrid vehicle, according an embodiment of the present disclosure. To derive maximum benefit out of hybrid technology, engine (200) is to be run at best efficiency zone. To achieve this, the planetary gear assembly (150) with shallow gear ratios is used. Shallow gear ratios herein refer to gear ratios of the planetary gear assembly (150) which fulfills vehicle speed and torque requirements when it is moving on a plane/flat road, and more particularly when vehicle is moving in hybrid mode. However, shallow gear ratios reduce vehicle gradeability (i.e. ability to drive on elevated roads like hilly areas) and particularly when vehicle is to be driven by engine (200) alone. To overcome this problem, there is a need for a mechanism between engine (200) and transmission which can amplify engine (200) torque. A torque converter (600) is provided between the engine (200) and input shaft (102) to accomplish this. The torque converter (600) serves the purpose of engine (200) torque amplification and helps to achieve desired gradeability. In addition, it also absorbs engine (200) torsional vibrations, helps to crank the engine (200) without jerk when vehicle is in running condition, and facilitates smooth transition from pure electric mode to hybrid mode. It also reduces jerk during gear shifting. In an embodiment of the present disclosure, the torque converter unit (600) includes but not limiting to a hydraulically and electrically operated torque converter unit.

In an exemplary embodiment of the disclosure, a hydraulically operated torque converter unit (600) is provided in the drive train (100) of the hybrid vehicle. The torque converter unit (600) comprises three rotating elements: an impeller (pump) (602), which is mechanically driven by the engine (200) through a shaft (601), a turbine (603) which drives the transmission and the stator (604), which is interposed between the impeller (602) and turbine (603), so that it can alter oil flow returning from the turbine (603) to the impeller (602). The stator (604) is mounted on a one-way clutch (604a), which prevents it from counter-rotating with respect to the prime mover i.e. engine (200), but allows rotation in the forward direction. A lockup clutch (605) is used to couple engine shaft (601) and transmission shaft (606) together to reduce energy losses when torque multiplication is not required. Further, the lock up clutch (601) which is used to engage the engine (200) with the transmission shaft (606) normally remains in closed condition. However, it will be opened during the following events: when engine (200) is being cranked through traction electric motor (300), when transition is made from pure electric mode to hybrid mode, when energy level in power source is very low and vehicle to be driven entirely by engine (200) at low speeds, and when engine (200) torque amplification is required i.e. when vehicle moves on a gradient.

It is to be understood that a person of ordinary skill in the art would design the drive train of any configuration without deviating from the scope of the present disclosure. Further, various modifications and variations may be made without departing from the scope of the present invention. Therefore, it is intended that the present disclosure covers such modifications and variations provided they come within the ambit of the appended claims and their equivalents.

Advantages:
The present disclosure provides a drive train for a hybrid vehicle which provides variable gear ratio in a single planetary gear assembly. This reduces space consumption by the transmission system in the vehicle which increases compactness of the vehicle and reduces overall weight of the system.

The present disclosure provides a drive train for a hybrid vehicle which is capable of generating power when the vehicle is stationary. This energy is restored in the power source and is utilized when vehicle is propelled in pure electric mode.

The present disclosure provides a drive train for a hybrid vehicle which regenerates energy when wheels of the vehicle are applied with brakes. Unlike conventional braking systems which dissipate frictional energy generated during braking in the form of heat to atmosphere, the drive train described in present disclosure converts this frictional energy into electric power which is stored in power source, and is used as and when required.

The present disclosure provides a drive train for a hybrid vehicle with a torque converter unit which provides necessary torque amplification which improves driveability of the vehicle whenever a gradient is encountered (i.e. provides torque to the vehicle enough to propel it on elevated regions).

The present disclosure provides a drive train for a hybrid vehicle in which an air-conditioning compressor is configured to be driven either by electric motor or by the engine. This facilitates the air-conditioning unit to be operated during non-availability of electric power.

Equivalents
With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

TABLE OF REFERRAL NUMERALS

Referral Numerals Description
100 Drive train of hybrid vehicle
200 Engine
300 Electric motor
400 Air-conditioning compressor
500 Differential casing
501 Axles
502 Drive wheels
150 Planetary gear assembly
102 Input shaft
103 Sun gear
104 Planet gears
105 Ring gear
106 Planet carrier
107 Output shaft
110 First clutching mechanism
120 Second clutching mechanism
130 Braking mechanism
600 Torque converter
601 Impeller shaft/Input shaft of torque converter
602 Impeller
603 Turbine
604 Stator
604a One-way clutch for stator
605 Lock up clutch
606 Turbine shaft/Output shaft of torque converter