DESC:TECHNICAL FIELD
[0001] The present subject matter relates to a powertrain. More particularly, the present subject matter is a transmission assembly for a powertrain.

BACKGROUND
[0002] Over the last few years, with the induction of new powertrain technologies concomitantly, substantial attention has been paid to compact powertrain delivering optimum power. To this end, much attention has also been paid to the design and development of an engine and a transmission. Typically, the engine and transmission are mounted in the vehicle as a single unit.
[0003] The above information disclosed in this background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The present invention is described with reference to an exemplary embodiment of powertrain. Such a powertrain can be installed in a two or three or multi wheeled vehicle. The same numbers are used throughout the drawings to reference like features and components. Further, the inventive features of the invention are set forth in the appended claims.
[0005] Non-limiting and non-exhaustive embodiments of the invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. It should be appreciated that the following figures may not be drawn to scale.
[0006] Descriptions of certain details and implementations follow, including a description of the figures, which may depict some or all of the embodiments described below, as well as a discussion of other potential embodiments or implementations of the inventive concepts presented herein. An overview of embodiments of the invention is provided below, followed by a more detailed description with reference to the drawings.
[0007] Figure 1a illustrates a partial top view of a powertrain with a localized view, in accordance with an embodiment of the present subject matter.
[0008] Figure 1b illustrates an exploded view of the powertrain, in accordance with an embodiment of the present subject matter.
[0009] Figure 2a illustrates an exploded view of a transmission assembly with localized views, where few parts being omitted from the figure, in accordance with an embodiment of the present subject matter.
[00010] Figure 2b illustrates a perspective view of the transmission assembly, where few parts being omitted form the figure, in accordance with an embodiment of the present subject matter.
[00011] Figure 3a illustrates a rear side view of the transmission assembly showing the axially movable member engaged with the first power assist gear, and a localized top view of the transmission assembly, where few parts are omitted from the figure, in accordance with one example of the present invention.
[00012] Figure 3b illustrates a cut section view of the transmission assembly showing high torque forward driving paths, wherein few parts are omitted from the figure, in accordance with one example of the present invention.
[00013] Figure 4a illustrates a rear side view of the transmission assembly in showing the axially movable member engaged with the second power assist gear, where few parts are omitted from the figure, in accordance with one example of the present invention.
[00014] Figure 4b illustrates a cut section view of the transmission assembly showing a high speed forward driving paths and a top view of the transmission assembly, wherein few parts are omitted from the figure, in accordance with one example of the present invention.

DETAILED DESCRIPTION
[00015] In the following description specific details are set forth to provide a thorough understanding of the embodiments. One skilled in the relevant art will recognize, however, that the techniques described herein can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring certain aspects.
[00016] Generally, for a vehicle, there is wide range of performance criteria which includes quantitative features like top speed, acceleration, gradeability etc. But there are several other aspects related to vehicle performance which includes refinement, drivability or driving pleasure. Therefore, it is always a challenge for design engineers to have a right trade-off between several performance features. Therefore, the power from a prime mover is controlled by a transmission assembly to deliver tractive effort to drive wheels. And all these components, collectively referred as a powertrain assembly, are controlled by the user. However, in relation to the powertrain assembly, the two major components are the prime mover and the transmission assembly. The prime mover plays a dominant role in overall vehicle performance. The prime mover converts available energy either electrical or chemical energy into mechanical power that is usually made at a rotating output shaft. However, power generated from the prime mover when transmitted directly to the drive wheels will lead to inappropriate torque. The direct drive results in uncontrolled speed or sub optimal speed and operating conditions limiting the ability to achieve best prime mover performance i.e. torque and rpm (revolutions per minute). Therefore, the transmission assembly is provided to achieve best vehicle performance and optimal operating conditions as well as to transmit power from the prime mover to the drive wheels of the vehicle. The design of the transmission assembly is critically important because the prime mover is only available over a limited speed range and hence the transmission assembly is critical in transforming it into usable power at the drive wheels.
[00017] Conventionally, in the powertrains, there is a problem of low torque at low speeds. 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 wheels to pull the vehicle, and the powertrain may not be able to provide the same. Further, moving at low speeds with less torque results in loss of fuel economy or range. Whereas, at higher speeds, a predetermined transmission ratio restricts speed at which the vehicle can travel and hence results in loss of fuel economy or range. Therefore, the powertrain may not be able to provide sufficient torque and the prime mover may get stalled / switched off. Hence, a trade-off between torque requirement and fuel economy or range is a difficult challenge since at higher torque requirements, the fuel economy or range drops which is undesirable. In this regard, there are various transmission mechanisms with many modes of switching like manual or automatic are known in the art.
[00018] The manual transmission system allows driver to select different speed ratio or gear ratio manually. Hence some special skill of driving is required to operate this type of gear box. Specifically in dense traffic conditions. The manual transmission system has different types which includes sliding mesh type transmission assembly, constant mesh type transmission assembly. All these types are known in the arts.
[00019] The sliding mesh type transmission assembly comprises gearing on a main shaft which are configured to move right or left for meshing them with suitable gears on a counter shaft for obtaining different gear ratio. In this sliding mesh type transmission assembly, the gears are meshed by sliding because of which precise level of skill is required to operate this kind of gear box and there are high chances of wear and tear of gears. This kind of transmission assembly typically encompasses spur type gears owing to which during gear shifting the engagement probability is very poor accompanied by noise which irritates the driver and passengers. Additionally, it requires more effort to change the gear. Due to these inherent disadvantages there are more chances of failure since gear tooth while sliding has to bear more impact loading and recurrent changing of gears increases the probabilities of gear failure which results in poor durability and life compared to other type of transmission assembly known in the art. Despite, inherent disadvantages of the sliding mesh type transmission assembly these are preferred due to high efficiency and low cost, so it is challenge for the automobile players to design gear teeth of high stability, durability under fluctuating load albeit same may be achieved by implementing high strength gears which are undesirably costly.
[00020] Further, the manual transmission constant mesh is an improvement over the sliding-mesh type transmission assembly. The constant mesh type transmission assembly configured to have gearing installed on a main shaft, a lay shaft and a clutch shaft which are in continuous mesh with each other. The shifting of gear is obtained by a sliding of clutch member i.e. dog clutches over the splined main shaft in order to obtain torque output. Yet the shifting operation of gear is accompanied by noise and is not smooth because of the difference in speed or rpm of the lay shaft, main shaft and clutch shaft at the time of shifting. Moreover, it is less efficient as compare to other type of transmission assemblies known in the art as the user requires tremendous skill to operate this type of transmission system.
[00021] More specifically, the high impact force acts on edges of the lugs during high torque operating conditions while shifting gears. This leads in plastic deformation also known as rounding-off of the edges of the lugs on a gear face. Importantly, over a period of time, due to the blended edges of the gear lugs the gear slip problem occurs. The gear slip occurs because the force along the axis of the gear is higher, and a gear locking mechanism fails to maintain the gears at its position. In addition to the above, it is observed that with increased installed load of locking mechanism increases the gear shifting effort significantly. This leads to hard gear shifting.
[00022] To this end, there is a need to provide a transmission assembly for a powertrain that will meet the common requirements of the vehicle including compact size, low weight, low cost, high reliability, while overcoming all the above problems & other problems of the known art. The aforementioned disadvantages of the prior arts are solved by the present invention which provides an improved transmission assembly. The transmission assembly is advantageously used striving to meet customer expectations by providing a low cost and safe vehicle.
[00023] According to one embodiment, it is an object of the present invention to provide a transmission assembly for a powertrain, which is compact, and light in weight, durable, and being configured to provide optimum power.
[00024] According to one embodiment, it is yet another object of the present invention to provide a transmission assembly having a gear shifting mechanism able to effectively lock the gears including dog clutch in position without increasing gear shifting effort.
[00025] According to the present subject matter to attain the above-mentioned objectives, in one aspect of the invention a transmission assembly for a powertrain of a two or three or four wheeled vehicle and a method of controlling a transmission assembly for the powertrain is disclosed.
[00026] As per an aspect of a transmission assembly for a powertrain. The transmission assembly comprising a housing assembly, and a power assist gear assembly. The power assist gear assembly includes one or more power assist gears, a mode switch assembly, and a mode switch lock assembly. The power assist gears being enclosed by said housing assembly. The mode switch assembly being operatively connected to said power assist gear assembly to switch between a first mode and a second mode to provide optimum power based on user’s inputs. The first mode being configured to provide plurality of high torque forward driving paths having predetermined gear ratio. The said second mode being configured to provide plurality of high speed forward driving paths having predetermined gear ratios. The mode switch lock assembly being supported by said housing assembly and being operatively connected to said mode switch assembly to lock user’s selected mode.
[00027] As per an embodiment, wherein said power assist gears includes a pair of first and second idler gears, a first power assist gear and a second power assist gear, wherein said first and second idler gears being operatively connected to said first and second power assist gears.
[00028] As per an embodiment, wherein said power assist gears includes an axially movable member, said axially movable member being installed between said first power assist gear and said second power assist gear.
[00029] As per an embodiment, wherein said axially movable member being installed on a splined portion of a final drive gear to selectively engage with said first and second power assist gears through said mode switching assembly.
[00030] As per an embodiment, wherein said mode switch assembly includes one or more transverse rods, one or more shifting rods, one or more fork shifting springs, one or more shifting forks, wherein one of said shifting fork being connected to one of said transverse rod and said transverse rod being supported by a mount structure.
[00031] As per an embodiment, wherein one of said fork shifting spring being wrapped around said transverse rod and said fork shifting spring being disposed of between said mount structure and said shifting fork.
[00032] As per an embodiment, wherein said shifting rod includes a locking arm, and a shifting arm, said locking arm disposed above said shifting arm at a predetermined angle (A) to each other when viewed in an up-down direction.
[00033] As per an embodiment, wherein an upper end portion of said shifting fork being configured to have a protrusion, said protrusion being positioned between a couple of limbs of said shifting arm, said limbs defines a substantially U-shaped structure of said shifting arm.
[00034] As per an embodiment, wherein said locking arm being configured to have an opening, said opening being configured to receive a leg of said shifting rod spring such that the bottom coiled surface of said shifting rod spring rests on upper surface of said locking arm.
[00035] As per an embodiment, wherein said shifting rod spring being positioned between said locking arm and a top cover, said top cover being attached to the housing assembly.
[00036] As per an embodiment, wherein said locking arm being configured to have a locking ramp.
[00037] As per an embodiment, wherein said mode switch lock assembly includes a stopper pin, and a pre-compressed elastic member, said stopper pin being configured to have an upper collar and a lower collar.
[00038] As per an embodiment, wherein an upper end of said stopper pin being configured to have an oval shape, and said upper end being in contact with a bottom surface of said locking arm.
[00039] As per an embodiment, wherein said mode switch lock assembly being supported by said mount structure, said mount structure being attached to said housing assembly.
[00040] As per an embodiment, wherein said mount structure being configured to have a first protrusion, said first protrusion having an opening, said opening being configured to receive said stopper pin.
[00041] As per an embodiment, wherein said mode switch lock assembly includes a pre-compressed elastic member, said pre compressed elastic member being disposed between said upper collar and an upper surface of said first protrusion.
[00042] As per an embodiment, wherein said housing assembly includes a Housing LH , a Housing RH, and a Housing cover RH.
[00043] The present subject matter is further described with reference to accompanying figures. It should be noted that the description and figures merely illustrate principles of the present subject matter. Various arrangements may be devised that, although not explicitly described or shown herein, encompass the principles of the present subject matter. Moreover, all statements herein reciting principles, aspects, and examples of the present subject matter, as well as specific examples thereof, are intended to encompass equivalents thereof.
[00044] The foregoing disclosure is not intended to limit the present disclosure to the precise forms or particular fields of use disclosed. As such, it is contemplated that various alternate embodiments and/or modifications to the present disclosure, whether explicitly described or implied herein, are possible in light of the disclosure. Having thus described embodiments of the present disclosure, a person of ordinary skill in the art will recognize that changes may be made in form and detail without departing from the scope of the present disclosure. Thus, the present disclosure is limited only by the claims.
[00045] In the foregoing specification, the disclosure has been described with reference to specific embodiments. However, as one skilled in the art will appreciate, various embodiments disclosed herein can be modified or otherwise implemented in various other ways without departing from the spirit and scope of the disclosure. Accordingly, this description is to be considered as illustrative and is for the purpose of teaching those skilled in the art the manner of making and using various embodiments of the disclosure. It is to be understood that the forms of disclosure herein shown and described are to be taken as representative embodiments. Equivalent elements, materials, processes or steps may be substituted for those representatively illustrated and described herein. Moreover, certain features of the disclosure may be utilized independently of the use of other features, all as would be apparent to one skilled in the art after having the benefit of this description of the disclosure. Expressions such as “including”, “comprising”, “incorporating”, “consisting of”, “have”, “is” used to describe and claim the present disclosure are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural.
[00046] Further, various embodiments disclosed herein are to be taken in the illustrative and explanatory sense, and should in no way be construed as limiting of the present disclosure. All joinder references (e.g., attached, affixed, coupled, connected, etc.) are only used to aid the reader's understanding of the present disclosure, and may not create limitations, particularly as to the position, orientation, or use of the systems and/or methods disclosed herein. Therefore, joinder references, if any, are to be construed broadly. Moreover, such joinder references do not necessarily infer that two elements are directly connected to each other.
[00047] Additionally, all numerical terms, such as, but not limited to, “first”, “second”, “third”, “primary”, “secondary”, “main” or any other ordinary and/or numerical terms, should also be taken only as identifiers, to assist the reader's understanding of the various elements, embodiments, variations and/or modifications of the present disclosure, and may not create any limitations, particularly as to the order, or preference, of any element, embodiment, variation and/or modification relative to, or over, another element, embodiment, variation and/or modification.
[00048] It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application. Additionally, any signal hatches in the drawings/figures should be considered only as exemplary, and not limiting, unless otherwise specifically specified.
[00049] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The invention will be described taking a five speed transmission assembly as an example through the specification.
[00050] Figure 1a illustrates a partial top view and a localized view of a powertrain (100), in accordance with an embodiment of the present subject matter. Figure 1b illustrates an exploded view of the powertrain (100), in accordance with an embodiment of the present subject matter. For sake of brevity, Figure 1a and Figure 1b will be discussed together. A frontward direction is indicated by an arrow F, and a rearward direction indicated by an arrow R. The powertrain (100) is extending from the front direction F to the rear direction R. The powertrain (100) includes a transmission assembly (101), and a housing assembly (102). The transmission assembly (101) includes a power assist gear assembly (103), a mode switch assembly (104), and a mode switch lock assembly (105). The power assist gear assembly (103) includes one or more power assist gears (104A, 104B, 104C, 104D).The power assist gears (104A, 104B, 104C, 104D) being enclosed by said housing assembly (102). Further, the mode switch assembly (104) being operatively connected to said power assist gear assembly (103) to provide optimum power based on user’s inputs. Furthermore, the mode switch lock assembly (105) being supported by said housing assembly (102) and being operatively connected to said mode switch assembly (104) to lock user’s selected mode. The housing assembly (102) includes a Housing LH (102L), a Housing RH (102R), and a Housing cover RH (102RC).
[00051] Figure 2a illustrates an exploded view of the transmission assembly (101) with localized views, where few parts being omitted from the figure, in accordance with an embodiment of the present subject matter. Figure 2b illustrates a perspective view of the transmission assembly (101), where few parts being omitted form the figure, in accordance with an embodiment of the present subject matter. For sake of brevity, Figure 2a and Figure 2b will be discussed together. The power assist gears (104A, 104B, 104C, 104D) includes a pair of first and second idler gears (104A, 104B). The idler gears (104A, 104B) being rotatably supported by the Housing RH (102R) (as shown in figure 1b) and the Housing cover RH (102RC) (as shown in figure 1b) through the roller bearings (209). As per an embodiment, the second idler gear (104B) being configured to have internal splines (104BA). The internal splines (104BA) being configured to receive the external splines (104AA) provided on the first idler gear (104A). As per an alternative embodiment, the first and second idler gears (104A, 104B) being integrated as a single unit. The idler gears (104A, 104B) being operatively connected to a first power assist gear (104C) and a second power assist gear (104D). An axially movable member (104E) being installed between said first power assist gear (104C) and said second power assist gear (104D). More specifically, the axially movable member (104E) being installed on a splined portion (201A) of a final drive gear (201) to selectively engage with said first and second power assist gears (104C, 104D) through said mode switching assembly (104). As per an embodiment, the axially movable member (104E) being configured to have one or more lugs. The lugs being configured to engage with slots provided in the first and second power assist gears (104C, 104D). As per alternative embodiment, the axially movable member (104E) being configured to have slots. The slots being configured to receive lugs provided on the first and second power assist gears (104C, 104D). The mode switch assembly (104) includes one or more transverse rod (202), one or more shifting rod (203), one or more torsion springs (204), one or more shifting fork (205). The shifting fork (205) being operatively connected to said transverse rod (202). The transverse rod (202) being supported by a mount structure (206). The mount structure is attached to Housing RH (102R) (as shown in figure 1b). As per an embodiment, one of said fork shifting spring (210) being wrapped around said transverse rod (202). The fork shifting spring (210) is a torsional spring. The fork shifting spring (210) being disposed between said mount structure (206) and said shifting fork (205). The shifting rod (203) includes a locking arm (203A), and a shifting arm (203B). The locking arm (203A) disposed above said shifting arm (203B) at a predetermined angle (A) to each other when viewed in up-down direction (Up-Dw). The pre-determined angle (A) ranges from 15 to 50 degrees. An upper end portion of said shifting fork (205) being configured to have a protrusion (205A). The protrusion (205A) being positioned between a couple of limbs (203BL, 203BR) of said shifting arm (203B). The limbs (203AL, 203AR) defines a substantially U-shaped structure of said shifting arm (203B). The locking arm (203A) being configured to have an opening (203AA). The opening (203AA) being configured to receive a leg (204A) of a shifting rod spring (204) such that bottom coiled surface of said shifting rod spring (204) rests on upper surface of said locking arm (203A). The shifting rod spring (204) being positioned between said locking arm (203A) and a top cover (208). The top cover (208) being attached to the housing assembly (102). As per an embodiment, the top cover (208) being attached to the Housing cover RH (102RC). The said locking arm (203A) being configured to have a locking ramp (203AB). The mode switch lock assembly (105) includes a stopper pin (105A), and a pre-compressed elastic member (207). The stopper pin (105A) being configured to have an upper collar (105AA) and a lower collar (105AB). An upper end (105AA) of said stopper pin (105A) being configured to have an oval shape. The upper end (105AC) being in contact with a bottom surface of said locking arm (203A). The mode switch lock assembly (105) being supported by said mount structure (206). The mount structure (206) being attached to said housing assembly (102). The mount structure (206) being configured to have a first protrusion (206A). The first protrusion (206A) having an opening (206AA). The opening (206AA) being configured to receive said stopper pin (105A). The pre-compressed elastic member (207) disposed between said upper collar (105AA) of the stopper pin (105A) and an upper surface (105AB) of said first protrusion (206AA).
[00052] Figure 3a illustrates a rear side view of the transmission assembly (101) showing the axially movable member (104E) engaged with the first power assist gear (104D), and a localized top view of the transmission assembly (101), where few parts are omitted from the figure, in accordance with one example of the present invention. Figure 3b illustrates a cut section view of the transmission assembly (101) showing the high torque forward driving paths (1-1T, 2-2T, 3-3T, 4-4T, 5-5T), wherein few parts are omitted from the figure, in accordance with one example of the present invention. For sake of brevity, figure 3a and figure 3b will be discussed together. As per an embodiment, the transmission assembly (101) includes a five speed transmission assembly. The user can select the primary drive gears (not shown) through a gear shift mechanism (not shown) known in the art. After selecting primary drive gear. The user, based on vehicle operating conditions need to switch between the first mode or a second mode. As per an embodiment, the first mode i.e. high torque mode being activated when the hand lever (301) is shifted to a position B by the user. As per alternative embodiment, a control unit (not shown) automatically switches between the first mode and the second mode based on powertrain operating conditions. The user can prefer the first mode when running the vehicle is in loaded conditions or based on different road/environmental conditions. During shifting of the hand lever (301) towards a position B, an inner wire (302) of the cable attached to the lever arm (303) being pulled, thereby rotates the shifting rod (203) in a first direction as the lever arm (303) is positioned on the top end portion of the shifting rod (203). As per an embodiment, the first direction being a clockwise direction when the shifting rod (203) viewed from the bottom. The rotation of the shifting rod (203) results in the angular displacement of the shifting arm (203B). Importantly, when the user operates the hand lever (301), the rotation of the shifting rod (203) releases the stopper pin (105A) to move in an upward direction (Up) due to the pre-compressed elastic member (207). The shifting arm (203B) being configured and positioned at the predetermined angle A below the locking arm (203A) such that initial few degrees of rotation of the shifting rod (203) will not move the shifting fork (205). However, the stopper pin (105A) being released to move upwards as the locking arm (203A) integrated to the shifting rod (203) being displaced. Beyond few degrees of rotation of the shifting rod (203), the limbs of the shifting arm (203B) pushes the shifting fork (205) in a predetermined direction. This action moves the axially movable member (104E) to engage with the first power assist gear (104C). As per an embodiment, the predetermined direction includes left side direction (L) when viewed from the top of the transmission assembly (101). Under this condition, the power being transferred from the second power assist gear (104D) to the first power assist gear (104C) through the pair of an idler gears (104A, 104B). Further, the corresponding power from said first power assist gear (104C) to the final drive gear (201) through said axially movable member (104E) to establish the first mode. As per an embodiment, the first mode includes five high torque forward driving paths (1-1T, 2-2T, 3-3T, 4-4T, 5-5T) providing gear ratios ranging from 50 to 6.
[00053] Figure 4a illustrates a rear side view of the transmission assembly (101) in showing the axially movable member (104E) engaged with the second power assist gear (104D), where few parts are omitted from the figure, in accordance with one example of the present invention. Figure 4b illustrates a cut section view of the transmission assembly (101) showing a high speed forward driving paths (1-1S, 2-2S, 3-3S, 4-4S, N-NS) and a top view of the transmission assembly (101), wherein few parts are omitted from the figure, in accordance with one example of the present invention. The second mode being activated when the hand lever (301) is shifted to a position A by the user. The second mode provides high speed and user can prefer said mode during vehicle unloaded condition or based on environmental/ road conditions. When user shifts the hand lever (301) from the position B towards the position A, the shifting rod (203) rotates in a second direction to reach its initial position. The second direction is opposite to the first direction. Importantly, the shifting fork spring (210) being preloaded when the first mode being selected by the user, therefore the shifting fork (205) and the axially movable member (104E) being pushed back by the shifting fork spring (210) to engage the axial movable member (104E) with the second power assist gear (104D). When the shifting rod (203) being rotates back to its original position, the locking arm (203A) on the shifting rod (203) pushes down the stopper pin (105A) with its locking ramp (203AB). The locking arm (203A) locks the stopper pin (105A) in its position to restrict the unintended movement of the shifting fork (205). Under this condition, the axial displacement of the shifting fork (205) being arrested by the stopper pin (105A). More specifically, the stopper pin (105A) held in position by the locking arm (203A) to avoid any undesired displacement of the shifting fork (205). At this stage, the hand lever (301) at the user’s end being locked and held in position until the user desires to change the other mode. The power being transferred from the second power assist gear (104D) to the final drive gear (201) through said axially movable member (104E) to establish the second mode. As per an embodiment, the second mode provides five high speed forward driving paths (1-1S, 2-2S, 3-3S, 4-4S, N-NS) providing gear ratios ranging from 40 to 5.
[00054] According to the above architecture, one of the primary efficacies of the present invention is the optimum torque and better acceleration being provided in the required zone. As per an embodiment, ten forwards driving paths being established within small compact powertrain.
[00055] According to the above architecture, one of the primary efficacies of the present invention is the improved durability of the gear train as the mode shift lock assembly avoids undesired displacement of the shifting fork thereby eliminates gear lip due to axial thrust on the gear lugs or due to road load vibrations.
[00056] According to the above architecture, one of the primary efficacies of the present invention is the flexibility to switch between high torque mode and high speed mode improves the vehicle performance as user can select the modes based on powertrain operating conditions or environmental/ road conditions.
[00057] The above-described embodiments, and particularly any “preferred” embodiments, are possible examples of implementations and merely set forth for a clear understanding of the principles of the invention. 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

100 Powertrain
101 Transmission assembly
102 Housing assembly
102R Housing RH
102RC Housing cover RH
102L Housing LH
103 Power assist gear assembly
104 mode switch assembly
104A, 104B Idler gears
104C, 104D Power assist gears
104E Axially movable member
105 mode switch lock assembly
105A Stopper pin
105AA Upper collar
105AB Lower collar
105AC Upper end
201 Final drive gear
201A Splines over final drive gear
202 Transverse rod
203 Shifting rod
203A Locking arm
203AA Opening in the locking arm
203AB Locking arm
203B Shifting arm
203BL, 203BR Limbs
204 Shifting rod spring
204A Leg of shifting rod spring
205 Shifting fork
206 Mount structure
206A Protrusion
206AA Opening in the protrusion
207 pre compressed Elastic member
,CLAIMS:1. A transmission assembly (101) for a powertrain (100), said transmission assembly (101) comprising
a housing assembly (102);
a power assist gear assembly (103), said power assist gear assembly (103) includes
one or more power assist gears (104A, 104B, 104C, 104D),
wherein said power assist gears (104A, 104B, 104C, 104D) being enclosed by said housing assembly (102),
a mode switch assembly (104), said mode switch assembly (104) being operatively connected to said power assist gear assembly (103) to switch between a first mode and a second mode to provide optimum power based on user’s inputs,
wherein said first mode being configured to provide plurality of high torque forward driving paths (1-1T, 2-2T, 3-3T, 4-4T, N-NT) having predetermined gear ratios, and
wherein said second mode being configured to provide plurality of high speed forward driving paths (1-1S, 2-2S, 3-3S, 4-4S, N-NS) having predetermined gear ratios; and
a mode switch lock assembly (105), said mode switch lock assembly (105) being supported by said housing assembly (102) and being operatively connected to said mode switch assembly (104) to lock user’s selected mode.
2. The transmission assembly (101) for a powertrain (100) as claimed in claim 1, wherein said power assist gears (104A, 104B, 104C, 104D) includes a pair of first and second idler gears (104A, 104B), a first power assist gear (104C) and a second power assist gear (104D), wherein said first and second idler gears (104A, 104B) being operatively connected to said first and second power assist gears (104C, 104D).

3. The transmission assembly (101) for a powertrain (100) as claimed in claim 1, wherein said power assist gears (104A, 104B, 104C, 104D) includes an axially movable member (104E), said axially movable member (104E) being installed between said first power assist gear (104C) and said second power assist gear (104D).
4. The transmission assembly (101) for a powertrain (100) as claimed in claim 1, wherein said axially movable member (104E) being installed on a splined portion (201A) of a final drive gear (201) to selectively engage with said first and second power assist gears (104C, 104D) through said mode switching assembly (104).
5. The transmission assembly (101) for a powertrain (100) as claimed in claim 1, wherein said mode switch assembly (104) includes one or more transverse rods (202), one or more shifting rods (203), one or more fork shifting springs (210), one or more shifting forks (205), wherein one of said shifting fork (205) being connected to one of said transverse rod (202) and said transverse rod (202) being supported by a mount structure (206).
6. The transmission assembly (101) for a powertrain (100) as claimed in claim 5, wherein one of said fork shifting spring (210) being wrapped around said transverse rod (202) and said fork shifting spring (210) being disposed of between said mount structure (206) and said shifting fork (205).
7. The transmission assembly (101) for a powertrain (100) as claimed in claim 5, wherein said shifting rod (203) includes a locking arm (203A), and a shifting arm (203B), said locking arm (203A) disposed above said shifting arm (203B) at a predetermined angle (A) to each other when viewed in an up-down direction (Up-Dw).
8. The transmission assembly (101) for a powertrain (100) as claimed in claim 5, wherein an upper end portion of said shifting fork (205) being configured to have a protrusion (205A), said protrusion (205A) being positioned between a couple of limbs (203BL, 203BR) of said shifting arm (203B), said limbs (203AL, 203AR) defines a substantially U-shaped structure of said shifting arm (203B).
9. The transmission assembly (101) for a powertrain (100) as claimed in claim 7, wherein said locking arm (203A) being configured to have an opening (203AA), said opening (203AA) being configured to receive a leg (204A) of said shifting rod spring (204) such that the bottom coiled surface of said shifting rod spring (204) rests on upper surface of said locking arm (203A).
10. The transmission assembly (101) for a powertrain (100) as claimed in claim 9, wherein said shifting rod spring (204) being positioned between said locking arm (203A) and a top cover (208), said top cover (208) being attached to the housing assembly (102).
11. The transmission assembly (101) for a powertrain (100) as claimed in claim 9, wherein said locking arm (203A) being configured to have a locking ramp (203AB).
12. The transmission assembly (101) for a powertrain (100) as claimed in claim 1, wherein said mode switch lock assembly (105) includes a stopper pin (105A), and a pre-compressed elastic member (105B), said stopper pin (105A) being configured to have an upper collar (105AA) and a lower collar (105AB).
13. The transmission assembly (101) for a powertrain (100) as claimed in claim 12, wherein an upper end (105AC) of said stopper pin (105A) being configured to have an oval shape, and said upper end (105AC) being in contact with a bottom surface of said locking arm (203A).
14. The transmission assembly (101) for a powertrain (100) as claimed in claim 1, wherein said mode switch lock assembly (105) being supported by said mount structure (206), said mount structure (206) being attached to said housing assembly (102).
15. The transmission assembly (101) for a powertrain (100) as claimed in claim 14, wherein said mount structure (206) being configured to have a first protrusion (206A), said first protrusion (206A) having an opening (206AA), said opening (206AA) being configured to receive said stopper pin (105A).
16. The transmission assembly (101) for a powertrain (100) as claimed in claim 1, wherein said mode switch lock assembly (105) includes a pre-compressed elastic member (207), said pre compressed elastic member (207) being disposed between said upper collar (105AA) and an upper surface (105AB) of said first protrusion (206AA).
17. The transmission assembly (101) for a powertrain (100) as claimed in claim 1, wherein said housing assembly (102) includes a housing LH (102L), a housing RH (102R), and a housing cover RH (102RC).
18. A method of selecting a first mode in a transmission assembly (101), said transmission assembly (101) equipped with a means operable by user, the multispeed transmission assembly (101) including a mode switch assembly (104) for actuating at least one shifting fork (205), the shifting fork (205) adapted to engage an axially movable member (104E) with a selected power assist gear, and a mode switch lock assembly (105), the method including the steps of:
Actuating a lever arm to rotate a shifting rod in a first direction,
Engaging the shifting fork through a shifting arm to produce an engagement force on said axially movable member, thereby moving the shifting fork and said axially movable member towards the first power assist gear, further effecting the full engagement of the first power assist gear with the axially movable member, and
Arresting an axial movement of the shifting fork by a mode switch lock assembly.
19. The method of selecting a first mode in a transmission assembly as claimed in claim 18, wherein said mode switch lock assembly (105) includes a stopper pin (105A), said stopper pin (105A) moves in a upward direction (Up).
20. The method of selecting a first mode in a transmission assembly as claimed in claim 18, further comprising steps of transmitting power from a second power assist gear (104D) to a first power assist gear (104C) through a pair of an idler gears (104A, 104B).
21. The method of selecting a first mode in a transmission assembly (101), as claimed in claim 20, further comprising steps of transmitting corresponding power from said first power assist gear (104C) to a final drive gear (201) through said axially movable member (104E) to establish the first mode.
22. A method of selecting a second mode in a transmission assembly (101), the transmission assembly (101) including a mode switch assembly (104) for actuating at least one shifting fork (205), the shifting fork (205) adapted to engage an axially movable member (104E) with a selected power assist gear, a mode switch lock assembly (105), the method including the steps of:
Actuating a lever arm to rotate a shifting rod in a second direction,
Engaging the shifting fork through a shifting arm to produce an engagement force on an axially movable member, thereby moving the shifting fork and said axially movable member towards second power assist gear, further effecting the full engagement of the second power assist gear with the axially movable member, and
Arresting an axial movement of the shifting fork by a mode switch lock assembly.
23. The method of selecting a second mode in a transmission assembly (101), as claimed in claim , wherein said mode switch lock assembly (105) includes a stopper pin (105A) being in contact with a locking arm (203A), said stopper pin (105A) moves in a downward direction through a locking ramp (203AB).
24. The method of selecting a second mode in a transmission assembly (101), as claimed in claim 22, further comprising transmitting power from a second power assist gear (104D) to a final drive gear (201) through said axially movable member (104E) to establish the second mode.