Claims:1. An electric vehicle comprising:
a chassis;
an electric motor as prime mover connected to said chassis and connected to a transmission system using a belt or a chain drive for transmitting power wherein; the transmission system is provided within a transmission housing;
an electric battery module for powering the electric motor comprising at least one battery;
wherein the position of the electric motor is adjustable using a centre distance (CD) adjuster mechanism wherein a provision for mounting of said CD adjuster mechanism is provided integral in a transmission housing.

2. An electric vehicle as claimed in claim 1 wherein; the position of electric motor is adjusted using the CD adjuster to change the centre distance between a motor shaft and a first intermediate shaft of transmission system which in turn adjust the tension in the belt drive.

3. An electric vehicle as claimed in claim 1 wherein; one end the electric motor is swingably mounted at a pivot point on the transmission housing and the other end of electric motor is mounted at other location on the transmission housing with the CD adjuster mechanism.

4. An electric vehicle as claimed in claim 3 wherein; the CD adjuster mechanism comprises a set of nut and bolts used to adjustably fix the motor position on the transmission housing such that the bolt is loosen using nut to swing the motor about the pivot point to adjust the position of the motor & belt tension.

5. An electric vehicle as claimed in claim 4 wherein; the CD adjuster mechanism comprises at least one slot on the transmission housing used to fix the motor using a motor fixing bolt wherein; the motor fixing bolt is inserted into said slot through an adjustment bolt such that the position of adjustment bolt is adjusted using a set of nuts which in turn moves the motor fixing bolt inside said slot thereby allowing swinging of the motor about the pivot point in order to adjust the motor position.
.

6. An electric vehicle as claimed in claim 5 wherein; the adjustment bolt is mounted substantially parallel to the CD of the belt drive.

7. An electric vehicle as claimed in claim 5 wherein; the adjustment bolt is mounted through a flange connected to the transmission housing and the position of adjustment bolt is locked and/or adjusted using the set of nuts mounted against the surface of said flange.

8. An electric vehicle as claimed in claim 5 wherein; the pivot point and slot on the transmission housing are provided with a negative taper on its surface which causes the motor to be mounted inclined towards opposite side of belt drive in order to compensate for motor shaft deflection.

9. An electric vehicle as claimed in claim 1 wherein; the electric motor is connected to the transmission system using a belt drive to deliver power to a first intermediate shaft of the transmission system wherein; the first intermediate shaft is connected to a second intermediate shaft which is further connected to a differential assembly using a set of gear pair.

10. An electric vehicle as claimed in claim 9 wherein; the gear pair comprises a set of helical gears having contact ratio increased by increasing helix angle up to 17.5 deg. and reducing module up to 1.5 while maintaining the face width of the gear constant.

11. An electric vehicle as claimed in claim 10 wherein; the gear pair include a damping mechanism so as to reduce noise and vibrations.

12. An electric vehicle as claimed in claim 9 wherein; the transmission and differential assembly is provided inside an integral transmission housing.

13. An electric vehicle as claimed in claim 1 wherein; the transmission housing is formed of two separate halves connected to each other.

14. An electric vehicle as claimed in claim 1 wherein; the transmission housing is provided with an integral flange having a plurality of mounting options enabling mounting of the motor transmission assembly at different orientations based on space availability of various types of vehicles.

15. An electric vehicle as claimed in claim 1 wherein; the vehicle is a compact vehicle including two, three and four wheel/ quadricycle vehicles. , Description:The invention comprises an improvement in, or a modification of, the invention claimed in the specification of the main patent applied for “An Electric Vehicle” having application number 201721045779 filed on 20-Dec-2017.

FIELD OF THE INVENTION
[001] This invention relates to electric vehicles and more particularly to motor and transmission positioning within electric vehicles.

BACKGROUND TO THE INVENTION
[002] A strong trend to electric vehicle manufacture and use is now becoming evident as concerns with climate change and availability of fossil fuels become evident. Electric vehicles include a number of batteries including a large number of electric cells. The number of batteries required for an application is driven largely by the required vehicle range. At the present time, readily available batteries remain bulky and this may limit their use particularly where desired vehicle range conflicts with small vehicle size.

[003] For example, small vehicles which currently operate using liquid and gaseous hydrocarbon fuels could advantageously be shifted to electric motor prime movers to reduce emissions. An initial trend to reduced emission prime movers has involved transition from petrol operated engines to gaseous fuelled engines, for example of the LPG or CNG type. This has reduced emissions. However, proposed changes in regulations, for example in India, is driving a shift to electrically powered vehicles. The timeline for such shift is short and there are obvious difficulties in reconfiguring a vehicle fleet to operate with electric motors. Vehicle re-design and re-configuration of manufacturing plants for electric vehicle manufacture is a potentially time consuming and costly exercise. Yet it is desirable to meet directives/focus set by the Government of various countries.

[004] A key issue in vehicle re-design is the challenge of maintaining a basic vehicle structure the same as, or at least similar to, current vehicle structure to aid the manufacturing transition and maintain customer acceptance whilst packaging the batteries. This is a particular issue for smaller vehicles and does not need to be addressed, at least to the same extent, as for four wheeler electric cars as produced. Compact packaging is typically a requirement and if the compact packaging could be done in a way that allows other advantages and functionality, for example motor cooling, to be done cost effectively, this would be a useful advantage.

[005] Most commonly, an electric vehicle comprises at least one battery to supply an electric power to the prime mover which is an electric motor. The electric motor is generally provided with a transmission system which is further connected to wheels of the vehicle for transmitting power. The electric motor provides a torque to the transmission system using a belt drive. As the belt tends to loose over a period of time, the centre distance between a motor drive pulley and a driven pulley of the transmission system needs to be adjusted for maintaining desired tension in the belt. The available systems to adjust the CD are bulky and complex which consumes more space due to use of additional brackets. Hence the available systems are not convenient for the centre distance (CD) adjustment especially in case of compact vehicle where limited space is available. Also the available system consume more time for CD adjustment.

[006] It is an object of the present invention to provide an electric vehicle design which enables convenient packaging of a motor and transmission and other components which also supports for a compact layout

[007] Another object of the present invention is to provide a convenient and compact mechanism for adjusting the belt tension in the belt drive.

SUMMARY OF THE INVENTION
[008] With this object in view, the present invention provides an electric vehicle comprising:
a chassis;
an electric motor as prime mover connected to said chassis and connected to a transmission system using a belt or a chain drive for transmitting power wherein; the transmission system is provided within a transmission housing;
an electric battery module for powering the electric motor comprising at least one battery mounted to the chassis;
wherein a portion of said electric motor is disposed below the chassis, such that the position of the electric motor is adjustable using a centre distance (CD) adjuster mechanism wherein; a provision for mounting the CD adjuster mechanism is provided integral in the transmission housing. .

[009] The belt drive provided with a Centre Distance (CD) adjuster to maintain or adjust the drive belt tension. The CD adjuster provides a convenient way to adjust the centre distance between the motor drive pulley and driven pulley of the transmission system. The electric motor is swingably mounted onto the transmission housing at a pivot point while at other location the electric motor is mounted via CD adjuster mechanism having mounting provision integral in the transmission housing.

[010] The transmission housing is preferably formed by joining two separate halves with each other. Each half comprising a slot, preferably an elongated slot or U-shaped slot such that when joined together, a through slot is formed in the transmission housing. One end of the motor is fitted into said slot preferably using a motor fixing bolt and nut. The motor is fitted at the slot by inserting a motor fixing bolt which goes through the holes provided on a motor casing and through the said slot. The motor fixing bolt is locked using a washer and nut at its other end. Further an adjustment bolt is provided (also known as I-bolt) which is an used to adjust the position of motor. The adjustment bolt portion mat be provided with a head portion having a through hole. The head portion of the adjustment bolt is abutted against the motor casing and other end is fixed or adjusted using a set of nuts provided on transmission housing. The motor fixing bolt is inserted through the adjustment bolt and further goes through the hole on motor casing and through the slot on transmission housing in order to fix the motor position. As per an exemplary embodiment, the other end of adjustment bolt is inserted through a flange mounted on the transmission housing. The position of adjustment bolt is fixed or adjusted using a set of nuts which are fixed against a surface of flange. Adjustment bolt is provided substantially parallel to the CD of the belt drive. This helps in avoiding loosening of adjustment bolt and set of nuts.

[011] When user wants to adjust the CD of belt drive, the motor fixing bolt is loosen and the position of adjustment bolt is adjusted using nuts. This causes the motor fixing bolt to move upward or downward inside the slot which in turn swings the motor about the pivot point. This causes the change in centre distance of belt drive which helps in adjusting the tension. Therefore, need of any separate brackets for mounting arrangement for CD adjuster mechanism is completely eliminated as the provision for mounting CD adjuster mechanism is provided as an integral part of the transmission housing which helps in reducing the number of extra parts and avoiding problems associated with extra brackets. Also the CD adjuster mechanism is compact and consumes no extra space and therefore it is very useful in a compact vehicle layout. Also, the CD adjustment can be done quickly.

[012] If the drive belt is required to be removed for any purpose such as maintenance, it is possible to first reduce the CD thereby allowing easy removal and insertion of the drive belt. The CD adjuster mechanism may be suitably provided with a scale to judge the tension in the belt in order to avoid over tensioning or loosening of belt. Similarly, when more drive belt tension is required, the electric motor position can be adjusted such that the CD of the drive belt increases which induces more tension in the drive belt.

[013] Power train for an electric vehicle, includes transmission assembly, for example a single speed transmission assembly having belt, helical gears and differential mechanism, which provides two stage reduction as described below. In a preferred embodiment, the electric motor is mounted directly on the transmission system which has differential mechanism, desirably with an integral casing/housing for the transmission and differential mechanism. Such a mounting of the power train assembly consumes less space and so provides the advantage of compactness.

[014] Preferably, the transmission system comprises a first intermediate shaft to which power is delivered from a shaft of the electric motor through a suitable drive for example a belt or chain drive. A belt drive is preferred. A toothed belt is more preferably used for transmitting the motive power than a normal belt which has more slip and which would cause reduction in transmission efficiency. A toothed belt has comparatively higher efficiency. The first intermediate shaft is connected to a second intermediate shaft for transmitting the power using a gear mechanism which forms a two stage reduction transmission system. A helical gear set, conveniently a pair, is used for first and second reduction stage. A gear pair of 2nd stage reduction is used with a differential assembly for the rear mounted power train. Overall size of the power train assembly is significantly less than for a comparable power output internal combustion engine and transmission assembly. Alternatively, the transmission arrangement can also be provided with a single speed single stage transmission system as described in the applicant’s co-pending Indian main application 201721045779 the contents of which are hereby incorporated herein by reference. .

[015] In order to reduce noise and vibration and provide smooth transmission, helical gears are desirably used as a final stage of the above mentioned gear drive. Helical angle of gears may be increased and the module of gear which is a ratio of a reference circle or pitch circle of the gear to the number of gear teeth is reduced. Face width of the gear is optimised so that the gear engage smoothly and reduce noise. The contact ratio of the helical gears is also increased. Preferably, low module gears are used, each gear having module up to 1.5 with pressure angle of 17.5 deg. The gears also desirably include a damping mechanism so as to further reduce noise and vibrations.

[016] The proposed power train assembly comprising motor, transmission and differential results in a very compact arrangement. The differential mechanism is conveniently connected to the two rear wheels through drive shafts to transmit the power to the wheels.

[017] During operation, the motor shaft gets deflected due to the forces applied by the belt drive on the shaft. Any deflection in the shaft causes frequent loosening of the belt drive. In order to compensate for the shaft deflection the surface of motor mounting points i.e. pivot point and slot is provided with negative taper which causes the motor to be mounted slightly inclined towards opposite side of the belt drive. Therefore, even though the motor shaft gets deflected, since the motor is mounted inclined towards the opposite side, the deflection gets compensated. This helps in reducing the problem of belt loosening due to motor shaft deflection. The angle of inclination of motor is selected based on the angle of shaft deflection during operation.

[018] The motor transmission assembly is mounted to a rear frame portion of the chassis of the vehicle, desirably so that the motor is swingable. According to a preferred embodiment, the rear frame portion is made from a plurality of longitudinal members connected to each other by cross frame member/s. The rear frame is mounted on the chassis of the vehicle and fixed at suitable locations using connectors such as nuts/bolts. Alternatively, the rear frame portion may be welded to the vehicle chassis. The bottom part of the rear frame portion has a mounting arrangement for fixing one end of the motor transmission assembly to it. Preferably, a flange is provided on the integral housing of the transmission and differential which is fixed to the said mounting arrangement of rear frame portion. The other part of the motor transmission assembly is fixed on the cross-member of the vehicle chassis using a mounting bracket. The motor transmission assembly is fixed using rubber isolators at both of the above mentioned locations to minimise the transfer of vibrations to the chassis and vice versa. As per one of the embodiments, the upper part of the rear frame portion is also conveniently utilized for mounting the electrical batteries along with its frame structure. Therefore, the rear frame portion is advantageously utilized for fixing both electrical batteries and the motor transmission assembly to the chassis of the vehicle which allows a compact arrangement. However the battery may be positioned at front portion of vehicle or central location based on the available space and type of vehicle.

[019] As a further embodiment, the rear frame portion may be fully integrated with the vehicle chassis and may be provided with suitable mounting provisions for motor/ transmission and battery while manufacturing the chassis.

[020] The transmission housing is desirably provided with an integral flange having a plurality of mounting options/provisions enabling mounting of the motor transmission assembly onto the chassis of various types of vehicles such as three wheeled or four wheeled vehicle having different layouts. The mounting provisions can be used selectively as per required orientation and packaging requirements of motor and transmission for a particular vehicle. For example, transmission system with two stage occupies more space compared to the transmission system with single stage. Considering the space constraints in vertical and longitudinal direction, the transmission assembly may be rotated by appropriate angle and fixed using the suitable mounting provision on the integral flange in order to accommodate the complete drive assembly in a compact space.

[021] The CD adjuster mechanism is advantageously used for better orientation of electric motor such that the maximum surface of the motor is exposed to ram air. The CD adjuster mechanism also provides better flexibility in terms of packaging the motor in the compact space as the motor position may be adjusted for better fitment. Similarly, the motor position may be minutely adjusted using the CD adjuster mechanism in achieving a better orientation which has minimum impact from external environmental problems such as due to water, mud, stones etc. Therefore, the CD adjuster is used as a multi-purpose mechanism.

[022] Advantageously, the other details of electric motor-transmission drive assembly as described in applicant’s co-pending application for main invention having application no 201721045779 are incorporated herein by reference.

[023] Similarly an electric power module may be configured as described in the applicant’s co-pending Indian provisional application 201721045778 and 201721046004, the contents of which are hereby incorporated herein by reference.

[024] The vehicle is intended to be a compact vehicle which can be used for commuter applications, such vehicle at least including three and four wheel vehicles. Such compact vehicles would have similar manufacturing costs and design to hydrocarbon fuelled vehicles currently available to the marketplace. The motor-transmission assembly can also be made such that it acts as a single package transmission which can be easily fitted on any vehicle for example a three or four wheeled vehicle/ quadri-cycle.
BRIEF DESCRIPTION OF THE DRAWINGS
[025] The electric vehicle of the present invention may be more fully understood from the following description of preferred embodiments thereof, made with reference to the accompanying drawings in which:

[026] Fig. 1(a) is a partial side view of an electric vehicle according to a first embodiment of the present invention.

[027] Fig. 1(b) is an orthogonal view cutaway view showing the relationships between the electric power module, the chassis and other elements of the electric vehicle shown in Fig. 1(a).

[028] Fig. 2 is a detail front orthogonal view of the chassis and indicating mounting of one part of the motor transmission assembly of the electric vehicle to the chassis.

[029] Fig 3 is a further orthogonal view showing the relationship between the rear frame portion, the motor transmission assembly and the rear wheels of the electric vehicle shown in Figs. 1(a) and 1(b).

[030] Fig. 4 is an isometric view of the chassis, motor transmission assembly according to second embodiment of present invention.

[031] Fig. 5 illustrates the details of transmission system according to preferred embodiment of present invention.

[032] Fig. 6(a) represents a perspective view of a left hand half of transmission housing according to preferred embodiment of present invention.

[033] Fig. 6(b) represents a perspective view of a right hand half of transmission housing according to preferred embodiment of present invention

[034] Fig. 7 represents a perspective view of mounting details of motor on transmission assembly at pivot point according to preferred embodiment of present invention.

[035] Fig. 8 represents a perspective view of mounting details of motor on transmission assembly according to preferred embodiment of present invention.

[036] Fig. 9 represents a perspective view of CD adjuster mechanism and mounting details of motor on transmission assembly according to preferred embodiment of present invention.

[037] Fig. 10 represents another perspective view of CD adjuster mechanism and mounting details of motor on transmission assembly according to preferred embodiment of present invention.

[038] Fig. 11 represents a side view of CD adjuster mechanism and mounting details of motor on transmission assembly according to preferred embodiment of present invention.

[039] Fig. 12(a) represents a schematic view of motor-transmission assembly illustrating deflection of shaft.

[040] Fig. 12(b) represents a schematic view of comparison of deflection of shaft caused by belt drive.

[041] Fig. 13 represents a detail view of mounting points used for mounting motor on transmission housing according to preferred embodiment of present invention.

[042] Fig. 14 represents a schematic view of comparison of deflection of shaft caused by belt drive according to preferred embodiment of present invention.

[043] Fig. 15 represents a graphical representation of shaft deflection against gradually increasing load of belt drive according to preferred embodiment of present invention

[044] Figs. 16 show orthogonal views of the motor transmission assembly and its relationship to the chassis of the electric vehicle of Figs. 1(a) and 1(b) the electric motor.

[045] Fig. 17 illustrates a transmission system according to Fig. 1 to 11 is utilized in a four wheeled vehicle.

DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION
[046] Referring now to Figs 1(a) and 1(b), there is shown an electric vehicle 10 suitable for use as a commuter vehicle and having a chassis 11 with a rear frame portion 11a. The chassis 11 is essentially the same as for both electric and internal combustion engine vehicle types. Differences in the structure of the electric vehicle 10 are essentially dictated by the requirement that the vehicle be electrically powered. The electric vehicle 10 is a three wheeler including a pair of rear wheels 82 and front wheel 84. Rear wheels 82 are provided with a suspension system, including trailing arms 92 and a shock absorber 93 provided on each of the trailing arms 92 of both the rear wheels 82. An anti-roll bar 90 is fixed onto the trailing arms 92 using suitable connecting structure. Further description of the electric vehicle is explained in detail in the main invention filed by the applicant having application number 201721045779 incorporated herein by reference. Further description of the electric battery module 22, protective frame structure 23, anti-roll bar 90, charger unit and vehicle control unit (VCU) 100 are as described in the Applicant’s co-pending Indian provisional patent application 201721045778 and 201721046004 incorporated herein by reference.

[047] Electric motor 20 has a rating of 7kW to 10 kW (though this rating is dictated by application) and is controlled by vehicle control unit (VCU) 100. Batteries 24 are of conventional design each with 48 volt rating connected in parallel so deliverable voltage is 48 volts. Electric motor 20 includes a transmission and detail of the relationship between transmission and rear wheels 82 is conveniently shown in Figs. 1 to 4. Electric motor 20 has a portion located below the rear frame portion 11a, and inboard, to enable ram air cooling during operation of the electric vehicle 10 as explained in the main invention having application number 201721045779 incorporated herein by reference.
[048] Electric motor 20 is connected to the transmission system 80 for providing drive from the electric motor 20 to rear wheels 82. Electric motor 20 and the transmission system 80 are mounted together, to form a motor transmission assembly 208 which is fixed to chassis 11 and chassis portion 11a by suitable mounts such as rubber soft mounts 110 in order to prevent transfer of vibrations and noise to chassis portion 11a and the chassis 11 and electric vehicle 10 generally. Mounting arrangements are most conveniently illustrated in Figs. 2 to 4. As the transmission system 80 could also be used in other vehicles requiring a different orientation of transmission system to chassis 11, the transmission housing 81 is provided with an integral flange 88 having a plurality of mountings points (819) enabling mounting of the motor transmission assembly at different orientations onto the chassis of various types of vehicles.

[049] The motor transmission assembly 208 is mounted to the rear frame portion 11a and chassis 11 of the electric vehicle 10 in a manner that allows the electric motor 20 to be swingable. The rear frame portion 11a of the chassis and related mounted arrangement as explained in the main invention having application number 201721045779 incorporated herein by reference.

[050] The transmission 80, as is typical for an electric vehicle, includes a single speed two stage power train assembly having a drive belt 91, a pair of helical gears 935, 940 and differential mechanism 86, which provides two stage reduction as described with the help of fig. 5 below. The electric motor 20 is mounted directly on the transmission system 80 comprising the differential mechanism 86. The differential mechanism 86 is conveniently connected to the two rear wheels 82 through drive shafts 83 to transmit power to the rear wheels 82 and not front wheel 84.

[051] The shaft 206 of electric motor 20 is connected with a first intermediate shaft 810 of the transmission 80 using a belt drive 91. The first intermediate shaft 810 also acts as input shaft of the transmission 80. The first intermediate shaft 810 is in connection with second intermediate shaft 860 through a gear pair 935. The second intermediate shaft 860 is further connected to the differential mechanism 86 using a second gear pair 940. Both first and second intermediate shaft are supported at two ends with the help of bearings 890. A helical gear set 935 and 940, conveniently a pair, is desirably used for first and second stage reduction with the differential mechanism 86. A helical gear set 935, 940 is selected in order to reduce noise and vibration and provide smooth transmission. Overall size of this power train assembly is significantly less than for an internal combustion engine and transmission assembly.. The power is delivered to the wheels 82 of the vehicle through differential 86 and drive shafts 83.

[052] Helical angle of helical gears may be increased and the module of gear reduced maintaining the face width of the gear constant so that the gears engage smoothly and reduce noise. The contact ratio of the helical gears 117 is also increased. Preferably, low module gears are used, each gear 117 having module up to 1.5 with pressure angle of 17.5 deg. The helical gears 117 also include a damping mechanism so as to further reduce noise and vibrations. This arrangement reduces angle of the drive shafts 83 and enables a lower position for the transmission system 80 than in conventionally fuelled and internal combustion engine equipped vehicles.

[053] Referring further to the belt drive 91, the belt drive 91 is here advantageously provided with a Center Distance (CD) adjuster 301, as shown in Figs. 6(a) to 11 to maintain the drive belt 91 tension. The CD adjuster 301 provides a convenient way to adjust the center distance between the motor drive pulley mounted on motor shaft 206 and driven pulley 802 of the transmission system 80. Adjustment between 1.5 and 5mm is possible here but this range may be selected differently. As described above, the electric motor 20 is swingably mounted onto the transmission housing 80 via a CD adjuster mechanism 301. The electric motor 20 is swingably fixed at pivot point 208A such that the electric motor 20 is capable to swing about pivot point 208A.

[054] According to preferred embodiment of present invention, the transmission housing 81 comprises two halves i.e. left hand half 81A and right hand half 81B coupled with each other using nut & bolts 837 to form a hollow space there between which is further used to accommodate the transmission assembly 80. The housing 81 acts as an integral housing for transmission 80 and differential 86 assembly. As shown, a flange 88 is provided on the integral housing 81 of transmission system 80 and differential mechanism 86. The flange 88 of the transmission housing 81 is provided with plurality of mounting points 819 enabling mounting of the motor transmission assembly 208 onto the chassis of the vehicle. At least one of the mounting point 208A is also used for swingably mounting the motor 20 directly on the transmission housing 81 such that the position of motor may be adjustable about said mounting point 208A.

[055] Both the halves 81A, 81B of transmission housing 81 has a slot 815, preferably an elongated or U-shaped slot such that when two halves 81A, 81B are joined a through slot 815 is created in the transmission housing 81 which is used to fix the other portion of motor 20 to the transmission housing 81. The motor 20 is fixed using nut-bolt assembly such that the motor 20 is movable inside the slot 815 to adjust its position. The motor casing 232 having holes 232A which corresponds to the slot 815 on the transmission housing 81. The motor 20 is fitted at the slot 815 by inserting a motor fixing bolt 303 which goes through the holes 232A provided on motor casing 232 and the slot 815 and locked using a washer 238 and nut 248. The motor fixing bolt 303 is further connected to an I-bolt which is an adjustment bolt 305. A flange 892 fixed to the transmission housing 81 with help of threaded bolts 892B. The flange 892 has a provision for inserting the adjustment bolt 305 using a set of nuts 305A which are fixed against a surface of flange 892.

[056] When a user wants to adjust the CD of belt drive 91, the motor fixing bolt 303 is loosen and the adjustment bolt 305 is adjusted using nuts 305A. This causes the motor fixing bolt 303 to move upward or downward inside the slot 815 which in turn rotates the motor 20 about the pivot point 208A. This causes the change in centre distance of belt drive 91 which helps in adjusting the tension. Adjustment bolt 305 is provided substantially parallel to the CD of the belt drive 91. This helps in avoiding loosening of adjustment bolt 305 and set of nuts 305A. Therefore, the complete provision for mounting CD adjuster mechanism 301 is provided as integral part of the transmission housing 81 thereby eliminating a need of any separate brackets or mounting arrangement. This eliminates the problems related to use of bracket such as the brackets gets deformed during use or the bolt assembly may get loose during operation. Also this helps in reducing the number of extra parts. Also the CD adjuster mechanism is compact and consumes no extra space and therefore it is very useful in a compact vehicle layout.

[057] If the drive belt 91 is required to be removed for any purpose such as maintenance, it is possible to first reduce the CD thereby allowing easy removal and insertion of the drive belt 91. The CD adjuster mechanism 301 may be suitably provided with a scale to judge the tension in the belt 91 in order to avoid over tensioning or loosening of belt 91. Similarly, when more drive belt tension is required, the electric motor 20 position can be adjusted such that the CD of the drive belt 91 is increased which induces more tension in the drive belt 91.

[058] During operation the motor shaft 206 gets deflected due to the forces applied by the belt drive 91 on the shaft 206 as shown in Figure 12(a). The comparison of deflection of the shaft (206) under no load condition and loaded condition is illustrated by Fig. 12 (b) which clearly shows the deflection of shaft 206 under loaded condition. The deflection may vary based on the amount of load applied. This can cause a frequent loosening of the belt drive 91. In order to compensate for the shaft deflection the surface of motor mounting points i.e. pivot point 206A and the slot 815 is provided with negative taper which causes the motor to be mounted slightly inclined towards opposite side of the belt drive 91 as shown in Figure 13. As shown in Figure 14 the motor shaft 206 is slightly inclined towards upper side under no load condition whereas under loaded condition or running condition due to the force applied by the belt drive 91 the motor shaft 206 gets deflected and comes to a straight horizontal position as required under ideal condition. Therefore, even though the motor shaft 206 gets deflected, since the motor 20 is mounted inclined, the deflection gets compensated. This helps in reducing the problem of belt loosening due to motor shaft deflection. The angle of inclination of motor 20 is selected based on the angle of shaft deflection during operation. Fig. 15 graphically illustrates the deflection of shaft in degrees against load applied by the belt tension. As the load increases the deflection of the shaft increases. As per an exemplary embodiment, the shaft deflection becomes zero at around 40kg of belt tension if the shaft angle is at around 0.3 degrees towards negative side at initial position and therefore the motor 20 is mounted tiled at same degree by providing a negative taper to the mounting surface as illustrated in Fig. 14. Therefore the mounting surface is provided with negative taper (for ex. of 0.3 degree) so that at nominal belt tension of 40kg the shaft becomes 0.0degree after deflection. This gives the benefit of 0.3 degree at nominal belt tension. The working variation at nominal 60Kg deflection of shaft reaches as high as 0.5 degree in a normal running condition, which is lowered to 0.2 degree according to modified arrangement. The angles may be decided based on the design requirements and actual loading condition.

[059] The fig. 12 represents mounting of motor-transmission assembly 208 on a three wheeled vehicle such that a portion of electric motor 20a is exposed to ram air for cooling the surface of electric motor 20. The CD adjuster mechanism 301 also helps in better orientation of electric motor 20 such that the maximum surface 20a of the motor is exposed to ram air. The CD adjuster mechanism 301 also provides better flexibility in terms of packaging the motor 20 in the compact space as the motor position may be adjusted for better fitment. Similarly, the motor position may be minutely adjusted using the CD adjuster mechanism in achieving a better orientation which has minimum impact from external environmental problems such as due to water, mud, stones etc. Therefore, the CD adjuster 301 is used as a multi-purpose mechanism.

[060] The vehicle is intended to be a compact vehicle which can be used for commuter applications, such vehicle at least including two, three and four wheel vehicles. The application of the above described transmission system is applied in a four wheeled vehicle 600 as illustrated in Fig. 13. The electric vehicle is provided with a battery module 24 used for powering electric motor. The battery module 24 is located centrally of the vehicle below driver and co-driver seat. The details of battery packaging is disclosed in applicant’s another patent application 201721046004, details of which are incorporated herein for reference. The mounting arrangement of the transmission system 208 along with motor 20 remains same as in three wheeled vehicle explained above. The described system may be conveniently utilized in a compact four wheeled vehicle such as quadricycle.

[061] Modifications and variations to the electric vehicle described in the present specification may be apparent to skilled readers of this disclosure. Such modifications and variations are deemed within the scope of the present invention.