PH12018000438A1 - An electric vehicle - Google Patents

Abstract

The present invention provides an electric vehicle comprising a chassis including a rear frame portion; an electric motor as prime mover connected to said chassis and to a rear drive transmission system; an electric battery module for powering the electric motor comprising at least one battery and its frame structure mounted to the chassis; wherein a portion of said electric motor is disposed below the rear frame portion of the chassis, such location of the portion of the electric motor being convenient to enable cooling, conveniently ram air cooling.

Description

[037] Fig. 15(a) shows a side view of the motor transmission assembly and its relationship to the rear frame portion of the electric vehicle of Figs. 1(a) and 1(b) with a protective guard for the electric motor.

[038] Fig. 15(b) shows a bottom view of the motor transmission assembly and its relationship to the rear frame portion of the electric vehicle of Figs. 1(a) and 1(b) with a protective guard for the electric motor.

[039] Fig. 16(a) shows an orthogonal view of the protective guard shown in Figs. 13 and 15.

[040] Fig. 16(b) shows an orthogonal view of the protective guard shown in Figs. 13 and 15 as a separate component.

[041] Fig. 17 shows a bottom view of the motor transmission assembly, its mounting locations and the protective guard.

[042] Fig. 18 shows a detail of the connection of the motor transmission assembly to the protective guard.

[043] Fig. 19 shows a side view of the protective guard mounted with an additional protective guard.

[044] Fig. 20 shows an orthogonal view of a power train for the electric vehicle of Figs. 1(a) and 1(b) using a first form of belt drive.

[045] Fig. 21 shows an orthogonal view of a power train for the electric vehicle of Figs. 1(a) and 1(b) using a second form of belt drive.

[046] Fig. 22 shows an orthogonal view of the relationship between the motor transmission assembly as shown in Figs. 1 to 10.

[047] Fig. 23 shows a side view of the motor transmission assembly as shown in Fig. 22.

[048] Fig. 24 is a detail view of a bottom portion of the motor transmission assembly shown in Figs. 22 and 23.

[049] Fig. 25 is a detail orthogonal view of the center distance adjuster included in the motor transmission assembly as shown in Figs. 22 to 23.

[050] Fig. 26 illustrates a transmission system according to Fig. 3 to 25 is utilized in a four wheeled vehicle.

DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION

[051] 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 anti-roll bar 90 is provided in the applicant's co- pending Indian provisional application 201721045778, incorporated herein by reference.

[052] A driver sits at the front of the electric vehicle 10 on front seat 12 and a rear seat 14 is available for seating of passengers. A target number of passengers is 2 or 3. A further passenger could join the driver on the front seat 12. Both seats 12 and 14 are of bench style though other configurations could be adopted if required. The driver steers electric vehicle 10 through handlebar 15.

[053] Electric vehicle 10 has an electric motor 20 and transmission system 80 powered by an electric power module 22 comprising two or three batteries 24 arranged in rows separated by a clearance space 24a as shown in Fig. 2. Electric battery module 22 is positioned to the rear of the vehicle 10 above the electric motor 20 and transmission system 80, a position which provides a convenient position for routing the wire harness.

[054] 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.

[055] Electric motor 20 includes a rear wheel drive transmission and detail of the relationship between transmission and rear wheels 82 is conveniently shown in Figs. 1 to 15. 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.

[056] Electric battery module 22 is located below a luggage compartment 188, located under the rear roof portion 10B of the electric vehicle 10 which demonstrates compactness as space remains available even with a change from an internal combustion engine prime mover to an electric motor prime mover. Electric battery module 22 includes a protective frame structure 23. Batteries 24 are separated by a space 24a to allow convective air heat transfer away from the electric battery module 22.

[067] Junction box 25 is connected external to and to the rear of frame structure 23 and, in this position, it does not require any further special supporting structure.

Junction box 25 is a housing for electrical connections connected to batteries 24 and other components which protects the connections from any external impacts, dust, water, dirt and so on. Further description of the electric battery module 22, protective frame structure 23, charger unit and vehicle control unit (VCU) 100 are as described in the Applicant's co-pending Indian provisional patent application 201721045778 incorporated herein by reference.

[058] Electric motor 20 includes a rear wheel drive transmission system for providing drive from the electric motor 20 to rear wheels 82. Electric motor 20 has a portion located below the rear frame portion 11a of chassis 11 to enable ram air cooling during operation of the electric vehicle 10. As was explained above, ram air cooling involves cooling by direct airflow over the electric motor 20 with the velocity of the cooling airflow being related to the speed of the electric vehicle 10 as well as cooling by directing the flow of air towards heated surface of motor 20 using louvers (not shown) where provided in the protective cover 95.

[059] Electric motor 20 and the transmission system 80 are mounted together, through mounting bracket 225, 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. 3 to 10 and 12 to 14, 22 and 23. 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 (not shown) enabling mounting of the motor transmission assembly onto the chassis of various types of vehicles.

[060] 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. As shown, rear frame portion 11a is made from a plurality of longitudinal members 11b connected to each other by a cross frame member 11c. The rear frame portion 11a is mounted on the chassis 11 of electric vehicle and fixed at four suitable locations 11d using nuts/bolts (not shown). Alternatively, the rear frame portion may be welded to the vehicle chassis. 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. The bottom part of the rear frame portion 11a has a first mounting arrangement 110 for fixing one end of motor transmission assembly 208. As shown, a flange 88 is provided on the integral housing 81 of transmission system 80 and differential mechanism 86 which is fixed to the rear frame portion 11a. The other end of the motor transmission assembly 208 is fixed on the cross-member 150 of the vehicle chassis 11 using a mounting bracket 125 that includes a structural member 190 extending below electric motor 20 to provide the requisite support. The motor transmission assembly 208 is fixed using rubber isolators 110 at both of the above mentioned mounting locations to minimise the transfer of vibrations to the chassis 11 and the rest of the electric vehicle 10 and vice versa. The mounting of the motor transmission assembly 208 enables sufficient ventilation for ram air cooling yet provides acceptable protection as well.

[061] The upper part 11aa of the rear frame portion 11a of chassis 11 is utilized for mounting, via the protective frame structure 23, the electrical batteries 24. Further description of the protective frame structure 23 and battery arrangement therein is provided in the Applicant's co-pending Indian Provisional Application 201721045778, incorporated by reference. Therefore, the rear frame portion 11a is utilized for fixing protective frame structure 23, its electrical batteries 24 and motor transmission assembly 208 to the chassis 11 of the vehicle which allows a compact arrangement, through use of some of the ground clearance space while also assisting ram air cooling.

[062] According to another embodiment of present invention, the rear frame 11a is made of two longitudinal members 11b and a rear cross member 11c is connected to the chassis 11 as illustrated in Fig. 7 to 10. The two longitudinal members 11b may be connected to the chassis 11 using nut/bolts or may be welded to the chassis 11. As an alternative the two longitudinal members 11b may be provided as an integral part of chassis 11. The rear cross member 11c is provided with mounting arrangement 110 for fixing the flange 88 of the transmission and differential housing 81. The rear cross member 11c is connected to the chassis using brackets (911 and 905). The bracket 911 is welded onto the chassis 11 and another bracket 905 is welded on the rear cross member 11c. These two brackets are connected to each other using rubber isolators 915. The rubber isolator helps in restricting the vibrations of the motor-transmission assembly 208 being transferred to the chassis 11. The other end of the motor- transmission assembly 208 is connected to the cross-member 150 of the vehicle chassis 11 using a mounting bracket 125 as explained in the previous embodiment above. In summary, the rear frame portion according to this embodiment comprises mainly a rear cross member 11c is used for mounting motor-transmission assembly 208 and the two longitudinal member 11b has no role in mounting of motor-transmission assembly 208 as against the previous embodiment explained above.

[063] The rear drive transmission 80, as is typical for an electric vehicle, includes a single speed power train assembly having a drive belt 91, helical gears 935 and differential mechanism 86, which provides two stage reduction as described with the help of fig. 11 below. The electric motor 20 is mounted directly along with the transmission system 80 on 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. The transmission, integrated with differential mechanism 86, is mounted along the centre longitudinal axis

C of the electric vehicle as shown in Figs. 5, 6, 14(b) and 15(b). It will be observed that left and right hand positioning of the electric motor 20 or transmission system 80 relative to longitudinal axis C is possible. Drive shafts 83 on both left and right hand side of the differential mechanism 86 have substantially equal length. This allows interchangeability of drive shafts 83 on right and left side. It eliminates the need to manufacture two drive shafts of different dimensions on right and left side thereby saving manufacturing cost.

[064] A helical gear set 935, conveniently a pair, is desirably used for second stage reduction with the differential mechanism 86. A helical gear set 935 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. It will be understood that the transmission system 80 can also be provided without a belt drive. The output shaft 205 of the electric motor 20 could also be directly engaged with the intermediate shaft 810 to transmit the power to the differential mechanism 86 using a gear drive. The power of the motor 20 is delivered to the intermediate shaft 810 of the transmission system 80, the shaft 810 is connected to the helical gear pair 935 which is further connected to the differential assembly 86. The power is delivered to the wheels 82 of the vehicle through differential 86 and drive shafts 83.

[065] 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.

[066] Referring further to the position of electric motor 20 below the rear frame portion 11a of the chassis 11, such positioning in the ground clearance exposes the electric motor 20 to external impacts; as well as water, mud or any foreign material which may clog or cause damage to the electric motor 20. A protective cover or guard 95, conveniently of polymer such as polypropylene (though metals and composites could also be used subject to weight considerations), may therefore be provided as shown in

Figs. 12 to 19. Such protective guard 95 is conveniently connected to the motor support member 190 with the assistance of the further bracket 95D. As shown in fig. 18 which is a sectional side view illustrating the mounting of guard 95 on the motor support member 190. Preferable the protective guard 95 is bolted using bolt 95C onto the motor support member 190. The protective guard 95 is configured to reduce obstacles to air flow which could reduce overheating of the electric motor 20. As shown in Fig. 14a and 15a, the hottest part of the electric motor 20 — the upper portion 20a — is left open without any covering elements. In this case, air is allowed to flow over the surface of the upper portion 20a of the electric motor 20 to achieve ram air cooling. Side portions and bottom portions of electric motor 20 are protected by protective guard 95 from any external impacts or ingress of water, mud or any foreign material. Further, there is high possibility of water entry from the front side of the motor 20 while travelling during rainy season hence an additional protective cover 95a is provided on the front side of the motor 20 as shown in Fig. 19. The cover 95a is designed in a boat type shape which minimises the possibility of water entry from front side. The height of the cover 95a is kept maximum. Any water entering into the cover will flow down from bottom of the cover 95c thereby preventing the possibility of water remaining in the cover for longer time. The additional protective cover 95a may be provided as an integral part of the protective guard/ cover 95. Additionally the protective guard 95 may include louvers (not shown) which directs the air towards the hot surface 20a of motor 20. With the help of louvers, additional cooling can be achieved.

[067] 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. 22 to 25 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 206 and driven pulley 802 of 16 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 by mounting bracket 225 such that the electric motor 20 is swingably fixed at one location 208A. Mounting bracket 225 is fixed to the transmission system side 80 for holding the electric motor 20 fixed at a certain position and comprises a sleeve adjuster 302 and an adjustment bolt 303. This arrangement allows the swingable adjustment of electric motor position which in turn controls the CD for drive belt 91. Therefore, when a user wants to adjust the CD of belt drive 91, the adjustment bolt 303 can simply be adjusted to adjust the electric motor 20 position to change the CD of the drive belt 91. 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. Similarly, when more drive belt 91 tension is required, the electric motor 20 position can be adjusted such that the CD of the drive belt 91 increases which induces more tension in the drive belt 91.

[068] 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. The application of the above described transmission system is applied in a four wheeled vehicle 600 as illustrated in Fig. 26. 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.

[069] 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.

Dated this on 7*" December, 2018

For Bajaj Auto Limited

Milind Joshi

Sr. Manager (R&D)

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AN ELECTRIC VEHICLE

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 smali 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] Itis 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.

SUMMARY OF THE INVENTION

[006] With this object in view, the present invention provides an electric vehicle comprising: a chassis including a rear frame portion; an electric motor as prime mover connected to said chassis and to a rear drive transmission system; an electric battery module for powering the electric motor comprising at least one battery and its frame structure mounted to the chassis; wherein a portion of said electric motor is disposed below the rear frame portion of the chassis, such location of the portion of the electric motor being convenient to enable cooling, conveniently ram air cooling. Ram air cooling involves cooling by a direct airflow stream (related to the velocity of the vehicle) flowing over the electric motor as well as cooling achieved by directing ram airflow towards heated part of motor.

[007] However, such position of a portion of the electric motor below the rear frame portion of the chassis and partly in the ground clearance exposes the electric motor to external impacts; as well as water, mud or any foreign material which may clog or cause damage to the electric motor. A protective cover or guard may therefore be provided, conveniently being connected to the electric motor. Such protective cover or guard is configured to reduce/avoid obstacles to ram air flow which could cause overheating of the electric motor. The protective cover or guard may be designed to force and/or guide cooling air flow. Preferably, the hottest part of the electric motor — the upper portion in the preferred disposition of the electric motor — is left open without any covering elements. In this case, air is allowed to flow over the surface of the upper portion of the electric motor to achieve cooling. The side portions and bottom portions of the electric motor are covered using said protective cover or guard thus protecting the bottom and the side portions of the electric motor from any external impacts or ingress of water, mud or any foreign material.

[008] The transmission, for an electric vehicle, includes a power train assembly, for example a single speed power train 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 along with the transmission system on the 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.

[009] Preferably, the transmission system comprises an intermediate shaft to which power is delivered from an output shaft of the electric motor through a suitable 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 and noise related problems. A toothed belt has comparatively higher efficiency and low noise. In such case, a toothed belt is used as a primary reduction. A gear mechanism is desirably used for second stage reduction. A helical gear set, conveniently a pair, is used for 2nd stage reduction 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 without a belt drive. The output shaft of the electric motor can also be directly engaged with the intermediate shaft to transmit the power to the differential mechanism using a gear drive.

[010] 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 an reference circle or pitch circle of the gear to the number of gear teeth reduced maintaining the face width of the gear constant 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.

[011] 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. The motor, transmission and differential are desirably positioned such that the length of the differential drive shafts on the left side and right side of the differential mechanism are substantially equal. This allows interchangeability of shafts on the right and left side. Also it eliminates the need to manufacture two different shafts of different dimensions on right and left side thereby saving the manufacturing cost.

[012] The motor transmission assembly is mounted to the 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.

[013] 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.

[014] The transmission housing is desirably provided with an integral flange having a plurality of mounting options 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.

[015] Advantageously, the 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.

[016] 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 four wheeled vehicle/ quadri-cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

[017] 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:

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

[019] 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).

[020] Fig. 2 is a detail view showing the relationship between the electric power module, motor transmission assembly and the chassis proximate the rear wheel in Fig. 1(b).

[021] Fig. 3(a) is a schematic side view showing the relationship between a rear frame portion and other portions of the chassis of the electric vehicle shown in Figs. 1 and 2.

[022] Fig. 3(b) is a detail front orthogonal view of the rear frame portion of Fig. 3(a) and indicating mounting of one part of the motor transmission assembly of the electric vehicle to the rear frame portion.

[023] Fig. 3(c) is a detail further orthogonal view of the rear frame portion of Figs. 3(a) and 3(b) and indicating mounting of one part of the motor transmission assembly of the electric vehicle to the rear frame portion.

[024] Fig 4(a) 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).

[025] Fig. 4(b) is a detail from Fig. 4(a) showing a rear mounting of the motor transmission assembly to the rear frame portion.

[026] Fig. 5 is a plan view showing one arrangement for the rear frame portion, motor transmission assembly and rear wheels of the electric vehicle of Figs. 1(a) and 1(b).

[027] Fig. 6 is a plan view showing a further arrangement for the rear frame portion, motor transmission assembly and rear wheels of the electric vehicle of Figs. 1(a) and 1(b).

[028] Fig. 7 is an isometric view of the rear frame portion, motor transmission assembly according to second embodiment of present invention.

[029] Fig. 8 is a plan view of the rear frame portion, motor transmission assembly according to second embodiment of present invention.

[030] Fig. 9 is a cut or sectional view of the rear frame portion, motor transmission assembly according to second embodiment of present invention.

[031] Fig. 10 is a partial view of the rear frame portion according to second embodiment of present invention

[032] Fig. 11 illustrates the details of transmission system according to preferred embodiment of present invention.

[033] Figs. 12(a) and 12(b) respectively show orthogonal views of the motor transmission assembly and its relationship to the rear frame portion of the electric vehicle of Figs. 1(a) and 1(b) without a protective guard for the electric motor.

[034] Figs. 13(a) and 13(b) respectively show orthogonal views of the motor transmission assembly and its relationship to the rear frame portion of the electric vehicle of Figs. 1(a) and 1(b) with a protective guard for the electric motor.

[035] Fig. 14(a) shows a side view of the motor transmission assembly and its relationship to the rear frame portion of the electric vehicle of Figs. 1(a) and 1(b) without a protective guard for the electric motor.

[036] Fig. 14(b) shows a bottom view of the motor transmission assembly and its relationship to the rear frame portion of the electric vehicle of Figs. 1(a) and 1(b) without a protective guard for the electric motor.

Claims (16)

We claim:

1. An electric vehicle comprising: a chassis including a rear frame portion; an electric motor as prime mover connected to said chassis and to a rear drive transmission system; an electric battery module for powering the electric motor comprising at least one battery and its frame structure mounted to chassis; wherein a portion of said electric motor is disposed below the rear frame portion of the chassis, such location of the portion of the electric motor being convenient to enable cooling, conveniently ram air cooling.

2. An electric vehicle as claimed in claim 1 wherein; the electric motor is mounted directly along with the transmission system on a differential mechanism.

3. An electric vehicle as claimed in claim 2 wherein; the transmission and differential mechanism is provided with an integral casing/housing. :

4, An electric vehicle as claimed in claim 2 wherein; the electric motor is swingably mounted on the transmission housing such that the motor position is adjustable which is used to adjust the tension in the belt drive.

5. An electric vehicle as claimed in claim 2 wherein; the transmission housing is desirably provided with an integral flange having a plurality of mounting options enabling mounting of the motor transmission assembly onto the chassis of various types of vehicles.

6. An electric vehicle as claimed in claim 2 wherein; the integral housing is used to fix a part of transmission and differential assembly to a mounting arrangement provided on the rear frame portion using rubber isolators and a other part of the transmission- differential assembly is fixed on a cross-member of the vehicle chassis using a mounting bracket.

7. An electric vehicle as claimed in claim 2 wherein; the differential mechanism is conveniently connected to the two rear wheels through drive shaft to transmit the power to the wheels preferably having same length.

8. 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 an intermediate shaft of the transmission system wherein; the intermediate shaft is connected to a differential assembly using at least a set of gear pair.

9. An electric vehicle as claimed in claim 8 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.

10. An electric vehicle as claimed in claim 9 wherein; the gear pair include a damping mechanism so as to reduce noise and vibrations.

11. An electric vehicle as claimed in claim 1 wherein; the rear frame portion is an integral part of the vehicle chassis and comprises at least a cross member on which the mounting arrangement is provided for mounting the transmission and differential assembly.

12. An electric vehicle as claimed in claim 1 wherein; the electric motor is provided with a protective cover covering at least a bottom and side part of the electric motor.

13. An electric vehicle as claimed in claim 12 wherein; the protective cover is designed to force and/or guide cooling air flow towards electric motor.

14. An electric vehicle as claimed in claim 1 wherein; the electric battery module is mounted either on the rear portion of chassis or central portion of the chassis based on vehicle layout.

15. An electric vehicle as claimed in any of the claim above is a three wheeled vehicle.

16. An electric vehicle as claimed in any of the claim above is a four wheeled vehicle. Dated this on 7*" December, 2018 For Bajaj Auto Limited ri Milind Joshi

Sr. Manager (R&D)