WO2021152620A1

WO2021152620A1 - Multispeed transmission for a vehicle

Info

Publication number: WO2021152620A1
Application number: PCT/IN2021/050075
Authority: WO
Inventors: Chandrakant Harne Vinay; Pattabiraman V; Gnanakotaiah Gutti; Puspha Priya K; Ajay Kumar MK; Vishnukumar KUDUVA SHANTHULAL; Vignesh V; Varalakshmi R
Original assignee: Tvs Motor Company Limited
Priority date: 2020-02-01
Filing date: 2021-01-24
Publication date: 2021-08-05
Also published as: MX2022009188A; CN115038895A; PE20221710A1

Abstract

The present invention related to the powertrain (100) having multispeed transmission assembly (200), wherein said multispeed transmission assembly (200) comprises high torque system and low torque system. The powertrain (100) having multispeed transmission assembly (200) ensures efficient transmission accompanied by less noise and smooth gear shift operation. The multispeed transmission assembly (200) configured to have compact layout and less weight is operable by gear shift and select assembly (205).

Description

MULTISPEED TRANSMISSION FOR A VEHICLE

TECHNICAL FIELD

[0001] The present subject matter relates to a powertrain. More particularly, the present subject matter relates to a multispeed transmission assembly.

BACKGROUND

[0002] In automobiles torque and speed are important parameters, which can vary as per different segment of the vehicle; likewise the vehicles are designed by keeping these two parameters in mind. It is always a challenge for the automobile manufactures to have appropriate balance between both torque and speed, likewise to achieve different speed at varying loads similarly different torque at different loads. However, a trade-off between torque requirement and fuel economy is difficult as during higher torque requirements the fuel economy drops. Further, power generated from the prime mover when transmitted directly to drive wheel will lead to inappropriate torque because direct drive results in uncontrolled speed or sub optimal speed, and poor engine performance i.e. torque vs. engine rpm (revolutions per minute) performance. Therefore, to get best vehicle performance and to ensure optimal operating conditions the power is transmitted from the prime mover to drive wheel of the vehicle typically through a transmission or gear box. The gear box provides the various kind of gear ratio as per user requirement. The gearbox is like a machine having controlled application enclosing various gears of different sizes, shafts etc.. The gear box has a multiple gear ratio with ability to switch between various speeds. There are many modes of switching like manually or automatically. Automatic transmission system and manual transmission system implemented in multi-wheel vehicles are known in art. But, introducing automatic transmission systems in compact layout of vehicles is difficult in view of the adverse impacts viz. size, layout space, cost, weight, number of parts to accommodate the additional transmission components such as clutch, gear trains and one way clutches. On the other hand the manual transmission allow driver to select different speed ratio or gear ratio manually which requires specific skills to operate. Hence, the trade-off between efficiency and cost is critical aspect for the automobile players as the critical issues involved in the design of the transmission system are to consider improving efficiency, better operability and reduce transmission losses and at the same time retain its attractive features of low cost and easy drivability. Furthermore the design should be so compact such that it will not affect the layout as well as package in available space. So it is always a challenge for the automobile designer of a compact vehicle to design a gear box which is efficient, effective & compact meeting various challenges outlined above and at same time be less costly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0003] The detailed description is described with reference to the accompanying figures. The same numbers are used throughout the drawings to reference like features and components.

[0004] Fig. 1 is a top view of a powertrain (100) as per preferred embodiment of the present invention.

[0005] Fig. 2 illustrates the perspective view of the powertrain (100) and local cut section view of gear lock mechanism of the multi-speed transmission assembly as per preferred embodiment of the present invention.

[0006] Fig. 3 illustrates the top cut section view of the multi speed transmission assembly showing high torque forward driving path as per preferred embodiment of the present invention.

[0007] Fig. 4 illustrates the top cut section view of the multi speed transmission assembly showing low torque forward driving path as per preferred embodiment of the present invention.

[0008] Fig 5 illustrates the side cut section of the powertrain (100) where few parts are omitted as per preferred embodiment of the present invention.

[0009] Fig. 6 illustrates the exploded of the reduction device (210) and decoupling device (211) and local side cut section view of the powertrain (100) where few parts are omitted. [00010] Fig. 7 illustrates a flowchart showing the steps of a gear selection method applied by the control system of powertrain (100). DETAILED DESCRIPTION

[00011] Various features and embodiments of the present invention here will be discernible from the following further description thereof, set out hereunder. According to an embodiment, a powertrain includes electric motor or internal combustion (IC) engine as prime mover to propel the vehicle. Such powertrain is installed in multi -wheeled vehicle. It is contemplated that the concepts of the present invention may be applied to other types of vehicles employing the similar transmission within the spirit and scope of this invention. Further "front" and "rear", and "left" and "right" referred to in the ensuing description of the illustrated embodiment refer to front and rear, and left and right directions as seen from a rear portion of the powertrain and looking forward. Furthermore, a longitudinal axis (Y-Y’) unless otherwise mentioned, refers to a front to rear axis relative to the powertrain, while a lateral axis (C-C’) unless otherwise mentioned, refers generally to a side to side, or left to right axis relative to the powertrain. [00012] However it is contemplated that the disclosure in the present invention may be applied to any vehicle without defeating the spirit of the present subject matter. The detailed explanation of the constitution of parts other than the present invention which constitutes an essential part has been omitted at suitable places. [00013] The powertrain is functionally connected to a drive wheel of the vehicle, which provides the forward motion to the vehicle. Typically, the internal combustion (IC) engine comprises a cylinder block includes a cylinder bore, a piston reciprocating in the cylinder bore, a cylinder head located above the cylinder block and a combustion chamber interposed between the cylinder head and the cylinder block. During operation of the internal combustion (IC) engine, the burning of air fuel mixture occurs in the cylinder block. The forces generated due to combustion of air fuel mixture is transferred to a piston which is capable of reciprocating inside the cylinder block, and this reciprocating motion is transferred to rotary motion of the crankshaft though a connecting rod by the slider crank mechanism. The cylinder head comprises intake valve and exhaust valve which control the intake of air fuel mixture inside the combustion chamber, and controls the exit of exhaust gases after combustion respectively. The exhaust gases include harmful emissions of hydrocarbons, carbon monoxide and nitrogen oxides into the atmosphere. To address these issues of harmful pollutants led to many innovations aiming to reduce the carbon gas emissions. Thus, OEMs and customers are being driven down a path to reduce carbon dioxide emissions by electrifying the drivetrain in that they have the capability to propel vehicles while leaving space inside the vehicles to allow large enough battery packs to give adequate range. Hence, the investment and market viability of the electrical vehicle are growing in a wide range also because of high costs of fossils based fuel. The alternative means for transportation includes electric vehicles. The electric vehicles uses traction motor as prime mover where typically a centrally mounted traction motor delivering traction torque through a gearbox to propel the vehicle is known in the art. But still it has its own inherent disadvantages like overall decrease in drivetrain efficiency when compared to the drivetrain losses for the equivalent vehicle fitted with direct drives. The direct drives lead to reduction of part count which includes elimination of heavy differential, gearbox etc. The direct drive is implemented due to the advantage of compact space. Thus, direct drive such as wheel hub motor is one of the promising configuration in automotive electrification. Further, in-wheel hub motor drives are relatively new entrants in the rapidly developing variable speed drive market. They are inherently variable speed drives featuring simple construction but at the same time the inherent disadvantage of in-wheel motors is limited torque delivery to drive wheel independently. In order to get desired torque the size of in-wheel motor should be increased which leads to undesirable increase in size of wheel assembly. Further, there is trade off by moving the drivetrain mass from the sprung to the unsprung mass as well as availability of space. This increased unsprung mass is often challenged with increased unsprung mass/sprung mass ratio which can potentially result in dangerous and uncomfortable vehicles. Moreover, direct drives require highly complex control elements and at the same time difficult to control. Furthermore, controlling direct drives needs complex algorithm to meet different driving conditions like cornering but albeit at a cost. [00014] In order to overcome aforesaid issues, it is known in the art to implement the electric powertrain with single speed reduction. However single speed reduction ratio can be either designed & calibrated for maximum torque or max speed requirement. When designed for the torque requirement as primary objective, speed requirements are compromised; further if speed requirement is also tried to address, that requires more current drawn from the battery which affects the mile-range of the vehicle as the current drawn for meeting the speed requirement is high. For example, when the vehicle is climbing a gradient on the road or heavy load is to be pulled there is requirement of a lot of torque at the drive wheel to pull the vehicle, and the single stage transmission system may not be able to provide sufficient torque and the prime mover may get switched off. In case the prime mover is configured to draw more current to augment torque, it may lead to thermal run-away of the systems in a chain & consequential multiple failure. Further it can also lead to more heat generation in the prime mover which requires additional capacity of cooling systems. Enhancing capacity of the cooling system not only adds to cost but also adds weight and reduce the mile range of the vehicle because cooling fans draws considerable amount of current from the batteries. Overall the design challenge becomes an endless moving target to achieve & a trade-off becomes imminent. Designing a system with a right trade-off & selecting the factors to trade-off is where lies the challenge for a design engineer.

[00015] A trade-off between torque requirement and fuel economy/ mile range is difficult as at higher torque requirements, the fuel economy/ mile range drops due to rapid battery drainage. Lower torque trade-off can lead to poor vehicle drivability performance & may not be liked by the end user. Thus, the critical issues involved in the design of the transmission system are to consider improving efficiency, beter operability and reduce transmission losses and at the same time retain its atractive features of low cost and easy drivability while still being compact in size & using low number of components. In order to address these issues, various kind of gear box/ transmission assemblies are implemented which provide variable gear ratio as per user requirement. The gear box known in art have a multiple gear ratio with ability to switch between various speeds. There are many modes of switching like manually or automatically. The manual transmission system which allow driver to select different speed ratio or gear ratio manually like H - shift mechanism etc. But this requires some special skill of driving to operate this type of gear box and it becomes more complex to shift gears when the vehicle has an electric drive train. Specifically, in traffic conditions from high gear to low gear.

[00016] An automatic transmission is an option but it can adversely affect the vehicle’s mechanical efficiency, fuel consumption, and overall cost. It can accommodate the range of vehicle needs and can operate smoothly. In this regard, there are many transmission mechanisms known in art. But the existing multispeed transmission assemblies have drawbacks wherein additional components are introduced causing layout constraints in the design. Such additional components include the introduction of a new transmission stage in the existing transmission like gear train mechanism and multiple centrifugal clutches. This requires complete overhaul of the powertrain layout and involves extensive research and development as well as considerable investment to design a powertrain. Automatic transmissions also increases the cost of the vehicle extensively. Further, changes in powertrain layout affects its space occupied in the vehicle and hence involves complete redesign of chassis frame structure to support the powertrain and change its disposition. Moreover, the change in design leads to increase in the size of the powertrain which consequentially leads to more cost, complex machinability of intrinsic parts & multiple adverse effects.

[00017] So, it is always a challenge for the automobile designer to design a powertrain which is more efficient, effective & compact meeting various challenges outlined above and at same time be less costly. The trade-off between efficiency and cost is critical aspect for the automobile manufacturers. At the same time the design should be so compact which will adversely require major change in layout of a vehicle.

[00018] A powertrain having multispeed transmission assembly is proposed in the present subject matter in order to alleviate one or more drawbacks highlighted above & other known drawbacks in the art.

[00019] It is therefore an aspect of the invention to provide a powertrain having multispeed transmission assembly which assures good engagement during gear shifting.

[00020] It is another aspect of the invention to provide a powertrain having multispeed transmission assembly which assures smooth gear shifting operation with less noise and vibration.

[00021] It is yet another aspect of the invention to provide a powertrain having multispeed transmission assembly which is compact in design, has less number of parts, does not require complex controls, is ease to use, provides desired drivability and of less weight.

[00022] It is another aspect of the invention to provide a powertrain having multispeed transmission assembly enclosing standardised parts which reduces part count and cost.

[00023] It is an aspect of the present invention to provide a powertrain having multispeed transmission assembly which is easier to operate and increases the driver comfort.

[00024] It is yet another aspect of the present invention to provide a powertrain having multispeed transmission assembly with low cost, high efficiency, good control throughout the entire speed range including grade ability.

[00025] The present subject matter relates to powertrain having multispeed transmission assembly. The multispeed transmission assembly includes at least one high torque system and at least one low torque system wherein said multispeed transmission assembly operable by a gear shift and select assembly. [00026] As per an aspect of the present subject matter, a Multispeed Transmission Assembly (MTA) is configured with an input shaft which is adapted to have involute splines at one of its end to fixedly couple with the prime mover. The prime mover includes traction motor or IC engine. The high torque system comprises a first drive gear installed on input shaft assembly engaged with a first driven gear, said first driven gear movably installed on the drive shaft assembly. The first driven gear configured to have projected lugs or slots to engage with the corresponding slot or lug of the axially movable member. Further, the low torque system comprises a second drive gear installed on input shaft assembly engaged with a second driven gear, said second driven gear movably installed on the drive shaft assembly. The second driven gear configured to have projected lugs or slots to engage with the corresponding slot or lug of the axially movable member. [00027] Further, the Gear Shift-And-Select (GSAS) assembly includes at least one actuator, at least one reduction device, said reduction device is detachably attached to a decoupling device DC, at least one gear shift shaft, said gear shift shaft attached to at least one gear shift fork. The gear shift fork adapted to have sensing elements near to both the ends. The actuator operatively connected to the decoupling device through the reduction device.

[00028] The Torque Reduction Device (TRD) comprises at least one sun gear, said sun gear is integrated at one end of the actuator, at least one carrier configured to receive at least three planet gears, a ring gear having an inner portion with plurality of gear teeth, said inner portion of the ring gear meshed with the planet gears, and at least three fastening members. The carrier is assembled to a torque receiving portion of the decoupling device by inserting a plurality of fasteners through holes in carriers and torque receiving member. The reduction device ensures that desired reduction ratio is achieved to complete the gear shifting operation, further the decoupling device is provided to decouple the actuator and output shaft if the torque at output shaft exceeds the predetermined value. The decoupling device comprises a torque delivery member, said torque delivery member transmitting the torque to a gear shift fork & a friction element preloaded by a basing means. The friction element maintains predetermined angular relationship with the torque delivery member and torque receiving member during predetermined operating conditions. The torque receiving member is configured to have an inner periphery surface and an outer periphery surface. The torque receiving member has tubular portion extending from inner periphery surface to the outer periphery surface. The inner periphery surface of the torque receiving member configured to have indents to make predetermined angular relationship with the friction members during predetermined operating conditions. Further, the biasing member is adapted to have cap at one of its ends. The biasing member being inserted into an inner tubular peripheral surface of torque receiving member. The outer periphery surface of the torque receiving member is covered by the cover. The cover provides base portion to the end cap of the biasing member. Further the torque receiving member is fixedly attached to the output shaft. The output shaft of decoupling device configured to have worm gear profile. The worm gear profile is provided on at least a portion of the output shaft. The worm gear engages with the rack provided on gear shift fork. Hence the worm and rack mechanism cause the fork to shuttle. Further position sensors are positioned on both sides of gear shift fork which senses the gear shift fork position through sensing elements and provides signal to the controller, wherein controller based on inputs, causes the actuator to change the direction of rotation with respect to current gear shift fork position for changing gear from high torque system to low torque system.

[00029] As under normal operative conditions the friction members makes a predetermined angular relationship with both torque receiving member and torque delivery member. But during gear shifting operation, when the torque is increased at the output shaft may be due to false engagement, then at predetermined r.p.m (rotation per minute) the friction members moves outwardly due to torsional force and position themselves in the indents provided on the inner peripheral surface of the torque receiving member, which results into slipping of friction members over torque delivery member. Thus, no torque is transmitted to the gear shift fork hence torque is limited to predetermined value.

[00030] The decoupling device limits the torque but also avoids the reversal torque coming to the actuator. Furthermore, the decoupling device ensures safe gear shift operation during gear change by interrupting the transmission of power when the torque exceeds the predetermined torque value and it automatically re-engages the output shaft to the actuator. The present invention about a Multispeed Transmission Assembly (MTA) includes GSAS (Gear Shift And Select) & TRD (Torque Reduction Device) technology delivering a HTS (High Torque System) & LTS (Low Torque System) transmission overcoming all of the problem cited earlier & other problems known in art.

[00031] The aforesaid and other advantages of the present subject matter would be described in greater detail in conjunction with the figures & embodiment in the following description. Further the prime mover includes “traction motor” or “IC engine” or “propulsive means” to propel the vehicle which is generally known in the art. Further the actuator includes electric motor or shift motor. Moreover the word “housing” is used interchangeably for gear box.

[00032] Figure 1. Illustrates the top view of powertrain (100) configured to have multispeed transmission assembly (200) for a vehicle. Typically, in a multi wheeled vehicle the powertrain (100) is located below the rear seat assembly (not shown) at a lower rear portion of the vehicle. The powertrain (100) comprises a prime mover (101) and a multispeed transmission assembly (200) (as shown in fig. 2) enclosed in a housing (104) which is attached to prime mover (101) through an adopter (102). The adopter (102) brings the flexibility of using prime mover (101) of various capacities in order to characterize & calibrate the vehicle to meet various requirements and needs according to the usage pattern of user and / or market segment application. The powertrain (100) is supported by and attached to the chassis frame structure (not shown) of the vehicle. The multispeed transmission assembly forms a part of the powertrain (100) and is mounted so as to be disposed on right or left of the vehicle. As per preferred embodiment the multispeed transmission assembly (200) (as shown in fig. 2) is disposed on left side of the powertrain (100) extending in lateral direction (C-C’) Further in an alternative embodiment the multispeed transmission assembly (200) (as shown in fig. 2) disposed on right side of the powertrain (100) extending in lateral direction (C-C’) The powertrain (100) is detachably mounted on chassis frame structure (not shown) through at least three point mounting (103F, 103RL, 103RR) using mount structures (not shown). The three point mounting (103F, 103RL, 103RR) includes one at front side (103F) of the powertrain (100) to support the housing (104) enclosing multispeed transmission assembly and two mounting points (103RL, 103RR) at rear side of the powertrain (100) to support the prime mover (101) and the gear box (104) respectively.

[00033] Figure 2 illustrates the perspective view of the powertrain (100) and local cut section view of a gear lock mechanism. The powertrain (100) comprises a multispeed transmission assembly (200) which is operable through gear shift and select assembly (205). The gear shift and select assembly (205) comprises at least one actuator (212) coupled with at least one decoupling device (211) through at least one reduction device (210). Further, the gear shift and select assembly (205) comprises at least one gear shift shaft (208), said gear shift shaft (208) attached to at least one gear shift fork (207). The decoupling device (211) gets the drive from actuator (212) with a reduction of r.p.m (rotation per minute) by reduction device (210). The output shaft (217) of decoupling device (211) is configured to have a worm gear profile (209) on at least a portion. The gear shift fork (207) has a rack profile (401) (as shown in figure 4) in proximity to an upper end and an opening near the upper end through which the gear shift shaft (208) extends. The worm gear profile (209) engages with the rack profile (401) (as shown in figure 4) provided on a gear shift fork (207). Hence the worm and rack mechanism makes the gear shift fork (207) to move to and fro which leads to change of system from high torque system to low torque system. Further, a pair of position sensors (206) are positioned on both sides of gear shift fork (207) which senses the gear shift fork (207) position and provides signal to controller (not shown), wherein controller based on inputs causes the actuator (212) to rotate in predetermined direction with respect to current gear shift fork (207) position for changing the mode from high torque system to low torque system or vice versa. The gear shift shaft (208) configured to have at least two grooves (216H, 216L) to lock the gears in position through gear lock mechanism. The gear lock mechanism includes a ball (216) preloaded by a spring (215). The spring (215) adapted to have an adjustable end cap (214) at the top to adjust the preload conditions as per user requirement. Further the gear shift shaft (208) adapted to have dampers (213) on both sides of the gear shift fork (207) to dampen the shock during gear shifting operation. The multispeed transmission assembly (200) includes at least one high torque transmission system and at least one low torque transmission system. The high torque transmission includes high torque input gearing and high torque output gearing. The high torque input gearing engaged with high torque output gearing. The high torque input gearing includes at least one drive gear (203a) installed on an input shaft assembly (201). The input shaft assembly (201) adapted to have involute splines (201a) at one of its end to fixedly couple with the prime mover (101) (as shown in fig. 1). The high torque output gearing includes at least one driven gears (204a) movably installed on a drive shaft assembly (202). The drive shaft assembly (202) is disposed parallel and alongside the input shaft assembly (201). Furthermore, the low torque system comprises low torque input gearing and low torque output gearing. The low torque input gearing is engaged with low torque output gearing. The low torque input gearing includes at least one drive gear (203b) installed on an input shaft assembly (201). The low torque output gearing includes at least one driven gear (204b) movably installed on a drive shaft assembly (202).

[00034] Figure 3 illustrates the top cut section view of the powertrain having multispeed transmission assembly showing gear shifting operation for the high torque system i.e. high torque input gearing to high torque output gearing where few parts are omitted from the fig. 2 as per preferred embodiment of the present invention. The gear shift fork (207) (as shown in fig. 2) is defined by a couple of limbs that define therein a U-shaped opening which extends on opposite sides of the appropriate axially movable member (302) and which turn interiorly for a short distance at the extremities to enter a groove (302G) around the central portion of the associated axially movable member (302). Further, the gear shift fork (207) (as shown in fig. 2) extends upwardly from the axially movable member (302) and thus axially movable member (302) may be shifted axially on drive shaft assembly (202) as desired by applying an appropriate force to the upper end of the associated gear shift fork (207) (as shown in fig. 2). [00035] The high torque system includes a first drive gear (203a) installed on input shaft assembly (201) engaged with a first driven gear (204a). The first driven gear (204a) is movably installed on the drive shaft assembly (202). The input shaft assembly (201) and drive shaft assembly (202) is supported by bearings (300, 301) at it’s both ends. The first driven gear (204a) configured to have slots (303a) to engage with the high torque lugs projection (302H) of axially movable member (302) selectively. In high torque system the axially movable member (302) projected lugs (302H) engages with the slots of the first driven gear (204a) where the first driven gear (204a) is in continuous mesh with the first drive gear (203a), Thus provide high torque forward driving path (HTP).

[00036] Figure 4 illustrates the top cut section view of the powertrain having multispeed transmission assembly (200) showing gear shifting operation for the low torque system i.e. low torque input gearing to low torque output gearing where few parts are omitted from the fig. 2 as per preferred embodiment of the present invention. The low torque system comprises a second drive gear (203b) installed on input shaft assembly (201) engaged with a second driven gear (204b). The second driven gear (204b) movably installed on the drive shaft assembly (202). The second driven gear (204b) configured to have slots (303b) to engage with the low torque lugs projection (302L) of axially movable member (302) selectively. Further, in low torque system the axially movable member (302) having projected slots (303b) engages with the slots of the second driven gear (204b) where the second driven gear (204b) is in mesh with the second drive gear (203b), thus provide low torque forward driving path (LTP).

[00037] In an alternative embodiment the first driven gear (204a) configured to have projected lugs to engage with the corresponding slot of the axially movable member (302) and second driven gear (204b) configured to have projected lugs to engage with the corresponding slot of the axially movable member (302). Further the slots or lugs can be provided alternatively, as the first driven gear (204a) configured to have slots to engage with the corresponding lug (302) of the axially movable member (302) and second driven gear (204b) configured to have projected lugs to engage with the corresponding slot (302L) of the axially movable member (302).

[00038] In yet another embodiment, first driven gear (204a) configured to have lugs to engage with the corresponding slots of the axially movable member (302) and second driven gear (204b) configured to have slots to engage with the corresponding lugs of the axially movable member (302).

[00039] Figure 5 illustrates the side cut section of the powertrain (100) where few parts are omitted. The gear shift and select assembly (205) includes reduction device (210) which is attached to decoupling device (211). The reduction device (210) having planetary gear system that ensures optimum speed and torque is transferred from actuator (212) to output shaft (217). The actuator (212) configured to have an actuator shaft (403), said actuator shaft (403) adapted to have external splines (403a) at one of its end to rotate planetary gears system of the reduction device (210). The external splines (403a) of actuator (212) are connected to planetary gears system and function as sun gear. As the actuator (212) rotates, output shaft (217) rotates with predetermined r.p.m (rotation per minute) as specified by planetary gear system ratio of reduction device (210). The output shaft (217) is supported by bearing (402) at one of its ends. The position sensors (206) mounted on both the sides of the gear shift fork (207) determine the position of gear shift fork (207) & inform user whether powertrain is in high torque system or low torque system. For this purpose the gear shift fork (207) is adapted to have sensing elements (404) on both sides. The position sensors (206) detect the gear shift shaft (207) position through sensing elements (404) and sends input to the control unit (not shown). Further, the control unit (not shown) based on various critical parameters and user input change the mode. When user changes the mode by using mode switch from low torque system to high torque system based on requirement, the position sensors (206) sends signal to the controller (not shown) where controller commands the actuator (212) to change the direction of rotation. As the actuator (212) rotates in clockwise direction, it makes the gear shift fork (207) move forward through worm and rack mechanism (209, 401) and engages the axially movable member (302) (as shown in fig. 3) with first driven gear (204a) (as shown in fig. 3).Thus vehicle is shifted to high torque mode where high torque system become operational and required high torque forward path is achieved. Furthermore, when user changes the mode using mode switch from high torque system to low torque system based on requirement the position sensors (206) sends signal to the controller (not shown), where controller (not shown) commands the actuator (212) to change the direction of rotation in counter clockwise direction which moves the gear shift fork (207) backwards through worm and rack mechanism (209, 401) and engages the axially movable member (302) (as shown in fig. 3) with second driven gear (204b) (as shown in fig. 3). Moreover, as and when the gear shifting operation completes, actuator (212) is turned off by the controller (not shown). Whenever a gearshift is demanded, the controller (not shown), based on user inputs, switches ON the actuator (212). Thus, the rotation direction of actuator (212) is predefined based on the required gearshift demand. The actuator (212) is allowed to rotate for the predetermined duration required to complete the gear shift operation.

[00040] Figure 6 illustrates the exploded of the torque reduction device (210) and decoupling device (211) and local side cut section view of the powertrain (100) where few parts are omitted for brevity. The actuator (212) (as shown in fig. 2) is attached to the decoupling device (211) through reduction device (210). The reduction device (210) comprises at least one carrier (508) configured to receive at least three planet gears (509), a ring gear (511) having an inner portion with plurality of gear teeth (511a) wherein said plurality of gear teeth (511a) of the ring gear (511) mesh with the planet gears (509). The actuator (212) (as shown in fig. 2) functions as sun gear to rotate the planetary gear system of the reduction device (210). The carrier (508) of the reduction device (210) assembled with a torque receiving member (504) of the decoupling device (211) by inserting a plurality of fastening members (510) through holes in carriers (508) and torque receiving member (504). Further the decoupling device (211) comprises torque receiving member (504) which is transmitting the torque to a torque delivery member (505), a friction member (506) preloaded by a biasing member (500), said friction member (506) maintains predetermined angular relationship with the torque delivery member (505) and torque receiving member (504) during predetermined operating conditions. The biasing means (500) includes springs.

[00041] The torque receiving member (504) configured to have an inner periphery surface (504a) and an outer periphery surface (504b) is configured with a tubular portion extending from inner periphery surface (504a) to the outer periphery portion (504b). Further, the inner periphery (504a) of the torque receiving member (504) configured to have plurality of indents (504c) to make predetermined angular relationship with the friction member (506) during predetermined operating conditions. Furthermore, the torque delivery member (505) configured to have plurality of indents (505a) to make predetermined angular relationship with the friction member (506) during predetermined operating conditions. The biasing member (500) is adapted to have end cap (501) at one of its ends, wherein said biasing member (500) is inserted into inner tubular peripheral portion (507) of torque receiving member (504). The outer periphery surface (504b) of the torque receiving member (504) is covered by the cover (512), wherein said cover (512) provide a base support portion to the end cap (501) of the said biasing member (500). The torque delivery member (505) is fixedly attached to the output shaft (217) which is configured to have worm gear profile (209) which is in mesh with the rack profile (401) (as shown in fig. 4) provided on the gear shift fork (207). A shim (502) and circlip (503) are installed on output shaft (217) to lock the friction member (506) inside the decoupling device (211).

[00042] Figure 7 illustrates a flowchart showing the steps of a gear selection method applied by the control system of multispeed transmission assembly (200). The controller unit (not shown) is disposed in optimum location to minimize the length of various connecting conductors, and also the impact of the temperatures and general conditions of environment. Further the mode switch (not shown) is disposed within ergonomic reach of the user like as for instance near the instrument panel of the vehicle, furthermore many of the logic functions known in the art may be implemented through the use of a suitably programmed controller unit (not shown). The user manually gives input through mode switch (not shown) based on which gear shift control starts (SI), wherein controller unit (not shown) detects user input and measures a value of at least one parameter related to vehicle, value of at least one parameter includes a gear shift fork (207) position, a vehicle speed, a state of charge of battery, output torque at the drive shaft assembly and other vehicle driving information. As per preferred embodiment the controller unit (not shown) detects whether the powertrain (100) is in high torque system or low torque system using inputs from position sensors (206) (S2). Further controller unit (not shown) synchronizes the speed of the vehicle to a predetermined synchronizing speed (S3), wherein to match the rpm (revolution per minute) of input shaft assembly (201) and drive shaft assembly (202). The predetermined synchronizing speed includes the maximum synchronous speed difference of less than 2 % between drive shaft assembly (202) and input shaft assembly (201) (S4). At the same time, controller unit (not shown) activates the gear shift and select assembly (205) by causing an actuator (212) to rotate in predetermined direction (S5). For high torque system the actuator (212) rotates in clockwise direction (S6A) and for low torque system the actuator (212) rotates in counter clock wise direction (S6B). As the actuator (212) is adapted to engage with the gear shift fork (207), the actuator (212) moves the gear shift fork (207) in a predetermined direction. For high torque system the gear shift fork (207) moves towards the high torque output gearing, whereas for low torque system the gear shift fork (207) moves towards the low torque output gearing. Furthermore, controller unit (not shown) controls the engaging gear shift fork (207) to produce an initial engagement force on the axially movable member (302), thereby moving the gear shift fork (207) and axially movable member (302) towards the selected gear installed on the drive shaft assembly (202). Hence in high torque system the powertrain (100) shifted is to predetermined gear ratio when the lug or slots of axially movable member (302) engage with slots or lug of driven gears (204a) installed on drive shaft assembly (202) (S7A). whereas in low torque system the power train is shifted to predetermined gear ratio when the lug or slots of axially movable member (302) engage with slots or lug of driven gears (204b) installed on drive shaft assembly (202) (S7B).The controller unit (not shown) gets input of at least one parameter related to vehicle. The value of at least one parameter includes a gear shift fork (207) position, a vehicle speed, a state of charge of battery, output torque at the drive shaft assembly (202) and other vehicle driving information. As per preferred embodiment the controller unit (not shown) detects whether the powertrain (100) is in high torque system or low torque system using inputs from position sensors (206) deactivates the gear shift and select assembly (205) which includes actuator (212) and at the same time deactivates the speed synchronization control (S8). This resumes the torque from the prime mover (101) (S9).

[00043] The powertrain having multispeed transmission assembly ensures smooth engagement of gears accompanied by less noise during gear shifting as the gear shift and select assembly comprises decoupling device which limits the torque due to slippage of friction element on torque delivery member of the reduction device and hence avoids the struggle which user experience generally in traffic conditions from high gear to low gear. Further the operator can change the mode using mode switch and can operate the vehicle either in high torque mode or low torque mode, which leads to less fatigue to the operator as compare to the manual gear shifting operation accompanied by more noise and also requires special skills to shift the gears.

[00044] Further, multispeed transmission assembly operable through gear shift and select assembly is provided with the sensing means and position sensor which are positioned on both the ends of the gear shift fork the requisite information is displayed to the operator through display unit to show that whether the vehicle is in high torque mode or low torque mode. This critical information is important for user to take decision while driving. Furthermore, the feature of lug and slot leads to use of standardised gear shifting parts as well as less cost. Furthermore, the present subject matter increases the mile range of the vehicle as the transmission system is now operated at an optimal performance curve of torque vs rpm leading to less current being drawn from the battery during various operating conditions of the vehicle. [00045] The powertrain having multispeed transmission assembly ensures more driver comfort as there is no clutch and hence issues like the double declutching is avoided and tremendous skill required to change gears is avoided at the driver end. The present invention is explained with an embodiment of a 2-speed ratio transmission but can be extended to more than two speed as part of multispeed transmission assembly.

[00046] While the present invention has been shown and described with reference to the foregoing preferred embodiments, likewise the prime mover can be IC Engine, Further instead of mode switch there can be various gear shift means like gear shift lever in various shift pattern which is generally known in the art, Furthermore the friction members includes balls or roller so it will be apparent to those skilled in the art that changes in form, connection, and detail may be made therein without departing from the spirit and scope of the invention.

[00047] Furthermore, the powertrain having multispeed transmission assembly as per preferred embodiment is two speed gear box but it includes three, four or five speed gear multispeed as it will be apparent to those skilled in the art that changes in form, connection, and detail may be made therein without departing from the spirit and scope of the invention. List of reference numerals

100 Powertrain 104 Housing/Gearbox

101 Prime mover/ Traction 200 Multispeed transmission motor/IC Engine assembly

102 Adopter 35 201 Input shaft assembly 103 at least three mounting 201a Involute profiles points 202 Drive shaft assembly

103F Front Mounting points 203a First drive gear 103RF Feft side Rear Mounting 203b Second drive gear points 40 204a First driven gear 103RR Right side Rear Mounting 204b Second driven gear points 205 Gear shift and select 403 Actuator shaft assembly 30 403a External splines on actuator

206 Position sensor shaft

207 Gear shift fork 404 Sensing elements

208 Gear shift shaft 500 Biasing member/ Spring

209 Worm gear profile 501 End cap

210 Reduction device 35 502 Shim

211 Decoupling device 503 Circlip

212 Actuator 504a Inner peripheral surface of

216 Ball Torque receiving member

216H, 216L at least two grooves 504 Torque receiving member

215 Spring 40 504b Outer peripheral surface of

214 Adjustable cap torque receiving member

213 Dampers 504c Plurality of Intends on

217 Output shaft torque receiving member 300, 301 Bearing 505a Plurality of Intends on

302 Axially movable member 45 torque delivery member 302H Lug on to engage with first 505 Torque delivery member driven gear 506 Friction member

302L Lug to engage with second 507 Inner tubular periphery driven gear surface

302G Grooves in axially movable 50 508 Carrier member 509 Planet gears

303a Slots in first driven gear 510 Plurality of fastening 303b Slots in second driven gear members

401 Rack profile 511 Ring gear

402 Bearing to support output 55 511a Plurality of gear teeth shaft 512 Cover

Claims

We Claim:

1. A powertrain (100) comprises: a prime mover (101); a housing (104) enclosing a multispeed transmission assembly (200); said multispeed transmission assembly (200) operatively connected to the prime mover (101), said multispeed transmission assembly (200) includes, at least one high torque system, and at least one low torque system operable by a gear shift and select assembly (205). to selectively engage at least one of the torque system to deliver torque to the output shaft.

2. The powertrain (100) as claimed in claim 1, wherein said high torque system comprises high torque input gearing and high torque output gearing, said high torque input gearing engaged with high torque output gearing.

3. The powertrain (100) as claimed in claim 1, wherein said high torque input gearing includes at least one drive gear (203a) installed on an input shaft assembly (201), said drive gear (203a) is engaged with a driven gear (204a).

4. The powertrain (100) as claimed in claim 1, wherein said high torque output gearing includes at least one driven gear (204a) movably installed on a drive shaft assembly (202), said driven gear (204a) configured to have slots or lugs to engage with the lug projection or slots of axially movable member (302) selectively.

5. The powertrain (100) as claimed in claim 1, wherein said low torque system comprises low torque input gearing and low torque output gearing, said low torque input gearing engaged with the low torque output gearing.

6. The powertrain (100) as claimed in claim 1, wherein said low torque input gearing includes at least one drive gear (203b) installed on an input shaft assembly (201), said drive gear (203b) is engaged with a driven gear (204b).

7. The powertrain (100) as claimed in claim 1, wherein said low torque output gearing includes at least one driven gear (204b) movably installed on a drive shaft assembly (202), said driven gear (204b) configured to have slots or lugs to engage with the lugs projection or slots of axially movable member (302) selectively.

8. The powertrain (100) as claimed in claim 2, wherein said high torque system comprises: a first drive gear (203a) installed on input shaft assembly (201) engaged with a first driven gear (204a), said first driven gear (204a) movably installed on the drive shaft assembly (202).

9. The powertrain (100) as claimed in 8, wherein said first driven gear (204a) configured to have slots (303a) to engage with the corresponding lug (302H) of the axially movable member (302).

10. The powertrain (100) as claimed in claim 5, wherein low torque system comprises: a second drive gear (203b) installed on input shaft assembly (201) with a second driven gear (204b), said second driven gear (204b) movably installed on the drive shaft assembly (202).

11. The powertrain (100) as claimed in claim 10, wherein said second driven gear (204b) configured to have slots (303b) to engage with the corresponding lug (302L) of the axially movable member (302).

12. The powertrain (100) as claimed in claim 10, wherein said input shaft assembly (201) adapted to have involute splines (201a) at one of its end to fixedly couple with the prime mover (101).

13. A gear shift and select assembly (205) comprising: at least one actuator (212), at least one reduction device (210), said reduction device (210) is detachably attached to a decoupling device (211), at least one gear shift shaft (208), said gear shift shaft (208) attached to at least one gear shift fork (207), wherein said actuator (212) operatively connected to the decoupling device (211) through the reduction device (210).

14. The gear shift and select assembly (205) as claimed in claim 13, wherein said actuator (212) configured to have actuator shaft (403), said actuator shaft (403) adapted to have external splines (403a) at one of its end to rotate planetary gears system of the reduction device (210).

15. A torque reduction device (210) having planetary gears system comprising: at least one carrier (508) configured to receive at least three planet gears (509), at least three fastening members (510), and a ring gear (511) having inner portion with plurality of gear teeth (511a), said plurality of gear teeth (511a) of the ring gear (511) are in mesh with the planet gears (509).

16. A decoupling device (211) comprising: a torque delivery member (505), said torque delivery member (505) transmitting the torque to a gear shift fork (207), a torque receiving member (504), said torque receiving member (504) connected to the reduction device (210), a friction member (506) preloaded by a biasing member (500), said friction member (506) maintains predetermined angular relationship with the torque delivery member (505) and torque receiving member (504) during predetermined operating conditions.

17. The gear shift and select assembly (205) as claimed in claim 13, wherein said reduction device (210) having carrier (508) is assembled to a torque receiving member (504) of the decoupling device (211) by inserting plurality of fastening members (510) through a holes in the carrier (508) and the torque receiving member (504).

18. The gear shift and select assembly (205) as claimed in claim 17, wherein said torque receiving member (504) configured to have an inner periphery surface (504a) and an outer periphery surface (504b).

19. The gear shift and select assembly (205) as claimed in claim 17, wherein said torque receiving member (504) having tubular portion extending from inner periphery surface (504a) to the outer periphery surface (504b).

20. The gear shift and select assembly (205) as claimed in claim 17, wherein said torque receiving member (504) configured to have plurality of intends (504c) to make predetermined angular relationship with the friction member (506) during predetermined operating conditions.

21. The gear shift and select assembly (205) as claimed in claim 16, wherein said decoupling device (211) having biasing member (500) adapted to have an end cap (501) at one of its ends, said biasing member (500) being inserted into an inner tubular peripheral portion (507) of torque receiving member (504).

22. The gear shift and select assembly (205) as claimed in claim 18, wherein said outer periphery surface (504b) of the torque receiving member (504) is covered by the cover (512), wherein said cover (512) provide base portion to the end cap (501) of the biasing member (500).

23. The gear shift and select assembly (205) as claimed in claim 17, wherein said torque receiving member (504) is fixedly attached to an output shaft (217), said output shaft (217) configured to have worm gear portion (209).

24. The gear shift and select assembly (205) as claimed in claim 13, wherein said gear shift fork (207) has a rack profile (401) in proximity to an upper end and an opening near the upper end through which the gear shift shaft (208) extends.

25. The gear shift and select assembly (205) as claimed in claim 23, wherein said worm gear profile (209) is provided on at least a portion of the output shaft (217), said worm gear profile (209) is in mesh with the rack profile (401) of the gear shift fork (207).

26. The gear shift and select assembly (205) as claimed in claim 13, wherein said gear shift fork (207) is defined by a couple of limbs that define there between a U-shaped opening which extend on opposite sides of the appropriate axially movable member (302) and which turn interiorly for a short distance at the extremities to enter a groove (302G) around the central portion of the associated axially movable member (302).

27. The gear shift and select assembly (205) as claimed in claim 13, wherein said gear shift shaft (208) configured to have at least two grooves (216H, 216L) to lock the gears in position through gear lock mechanism, said gear lock mechanism includes a ball (216) preloaded by a spring (215).

28. The gear shift and select assembly (205) as claimed in claim 27, wherein said spring (215) adapted to have adjustable end cap (214) at the top to adjust the preload conditions as per user requirement.

29. A method of selecting a gear in an multispeed transmission assembly (200) for a vehicle, the multispeed transmission assembly (200) equipped with a mode switch operable by user, the multispeed transmission assembly (200) including an gear shift and select assembly (205) for actuating at least one gear shift fork (207), the gear shift fork (207) adapted to engage an axially movable member (302) with a selected gear installed on a drive shaft assembly (202), the method including the steps of: detecting user input and measuring a value of at least one parameter related to vehicle; synchronizing a rotating speed of the drive shaft assembly (202) and the input shaft assembly (201) until they reach a predetermined rotating speed difference; activating the gear shift and select assembly (205) by causing an actuator (212) to rotate in predetermined direction, said actuator (212) adapted to engage with the gear shift fork (207), moving the gear shift fork (207) in a predetermined direction; engaging gear shift fork (207) to produce an engagement force on the axially movable member (302), thereby moving the gear shift fork (207) and axially movable member (302) towards the selected gear; further effecting the full engagement of the selected gear with the axially movable member (302); measuring a value of at least one parameter related to vehicle; deactivating the gear shift and select assembly (205) based on the at least one vehicle parameter measured.

30. The method of selecting the gear in the multispeed transmission assembly (200) as claimed in claim 30, wherein said value of at least one parameter includes a gear shift fork position, a vehicle speed, a battery state of charge, engine rpm, engine input torque, output torque.