ELECTRIC VEHICLE

Abstract

An electric vehicle (10) comprising: a frame (11); an electric battery module (24) comprising at least one battery connected to the frame; an electric motor (20) receiving power from the battery module (24); a transmission system (80) provided with a transmission casing (208B); said electric motor (20) is closely coupled to the transmission system (80) and is mounted on the transmission casing (208B); and a rear wheel (84) receiving power from the electric motor (20) through the transmission system (80) and said rear wheel (84) is connected to the frame using a rear suspension system; wherein the rear wheel (84) is connected to the frame (11) using said casing (208B) forming a part of the rear suspension system.

Claims

1-13. (canceled)

14. An electric vehicle comprising: a frame; an electric battery module including at least one battery connected to the frame; an electric motor receiving power from the electric battery module; a transmission system closely coupled to the electric motor; and a rear wheel receiving power from the electric motor through the transmission system, wherein the electric motor and the transmission system are located on a same side of the rear wheel, and further wherein the rear wheel is connected to the frame using a swing arm, the swing arm: functioning as a transmission casing by encompassing the transmission system and forming an integral part of the transmission system; having a provision for externally mounting the electric motor towards an opposite side of transmission system; and extending horizontally such that one end of the swing arm mounts on the rear wheel and the other end is pivotally mounted on the frame forward of a rear wheel to form a structural element of a suspension system of the vehicle.

15. An electric vehicle as claimed in claim 14, wherein the transmission system and the electric motor are closely coupled such that the transmission system and the electric motor are mounted within dimensions of rear wheel.

16. An electric vehicle as claimed in claim 14, wherein the transmission system is a single speed, multi stage transmission, further wherein the transmission system and the electric motor are closely coupled such that an input shaft of the transmission system is connected to an output shaft of the electric motor through a first gear pair, and the input shaft of the transmission is further connected to an output shaft of the transmission system through a second gear pair, and further wherein the output shaft of the transmission system is connected to the rear wheel of the vehicle for transmitting the torque.

17. An electric vehicle as claimed in claim 14, wherein the swing arm is connected to the frame at a first pivot joint forward of the rear wheel and to the second pivot joint at a rear axle of the rear wheel such that the swing arm pivots vertically, to allow the rear suspension system to absorb shocks from bumps in the road.

18. An electric vehicle as claimed in claim 14, wherein the suspension system includes at least one shock absorber mounted at the transmission casing.

19. An electric vehicle as claimed in claim 14, wherein the transmission system uses a chain or belt drive to transmit the power from the electric motor to the rear wheel.

20. An electric vehicle as claimed in claim 16, wherein the transmission system includes an input gear supported at both ends by bearings in a transmission housing and the input gear of the first gear pair is coaxially mounted on the electric motor output shaft such that the electric motor output shaft and the transmission input gear connection lies within the transmission input gear length.

21. An electric vehicle as claimed in claim 16, wherein the transmission system is provided in a transmission housing and the electric motor is provided in a motor housing, wherein both the transmission housing and the motor housing are separate and connected to each other such that an electric motor output shaft including an input gear is supported at four or more locations through bearings, and further wherein two locations are present in the motor housing and two other locations are present in the transmission housing.

22. An electric vehicle as claimed in claim 16, wherein the transmission system and the electric motor are provided in a common integral housing such that an electric motor output shaft including an input gear is supported through bearings at three or more locations, and further wherein two locations are ends of the electric motor output shaft and a third location is at an intermittent location of the electric motor output shaft.

23. An electric vehicle as claimed in claim 16, wherein the first gear pair includes an input gear mounted on an electric motor output shaft using a bolt, and further wherein the bolt is meshed with internal threads provided on an inner part of the electric motor output shaft and a bush is mounted in a gap created between the bolt and an inner surface of input gear.

24. An electric vehicle as claimed in claim 14, wherein the transmission casing is provided with a cover to direct airflow towards the electric motor.

25. An electric vehicle as claimed in claim 14, wherein the electric battery module is mounted centrally and below a rear frame portion.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0023] The electric vehicle of the present disclosure may be more fully understood from the following description of preferred embodiments thereof, made with reference to the accompanying drawings in which:

[0024] FIG. 1 is a partial isometric view of an electric vehicle according to a first embodiment of the present disclosure.

[0025] FIG. 2 is a partial side view of the electric vehicle of FIG. 1.

[0026] FIG. 3 is a first detail side view projected from FIG. 3 showing vehicle control unit, motor transmission assembly and shock absorber in relation to the rear frame portion of the electric vehicle of FIG. 1.

[0027] FIG. 4 is a second detail side view projected from FIG. 3 showing the battery, vehicle control unit and shock absorber.

[0028] FIG. 5 is a schematic side section view of the rear portion of the electric vehicle of FIG. 1.

[0029] FIG. 6 is a partial side view of the rear portion of the electric vehicle of FIG. 1.

[0030] FIG. 7(a) is a schematic partial rear left hand side view showing the motor-transmission position for the electric vehicle of FIG. 1.

[0031] FIG. 7(b) is a schematic partial rear right hand side view showing the suspension system for the electric vehicle of FIG. 1.

[0032] FIG. 7(c) is a schematic partial left hand side isometric view showing the suspension system for the electric vehicle of FIG. 1.

[0033] FIG. 7(d) shows a detail from FIG. 7(c) showing the motor transmission assembly which also forms part of the suspension system of the electric vehicle of FIG. 1.

[0034] FIG. 8 is an isometric view showing the motor-transmission assembly for the electric vehicle of FIG. 1.

[0035] FIG. 9 is a schematic layout of the transmission system included within the motor-transmission assembly of FIG. 8.

[0036] FIG. 10 is a schematic view of layout of transmission system provided with integral housing according to one of the embodiments of present disclosure.

[0037] FIG. 11a represents a schematic view of the transmission system with silent bush according to one of the embodiments of present disclosure.

[0038] FIG. 11b represents a detailed schematic view of the transmission system of FIG. 11a

DETAILED DESCRIPTION

[0039] Referring now to FIGS. 1 and 2, there is shown an electric vehicle 10 suitable for use as a commuter vehicle and having a frame 11 having a head tube 12, a front portion 14 and a rear frame portion 13. The electric vehicle 10 is a two-wheeler scooter including a front wheel 82 and rear wheel 84. Rear wheel 84 is provided with a rear mudguard 84A and a swing arm suspension system described further below with a single shock absorber 94. Scooter 10 is shown mounted on a stand 176 of conventional form.

[0040] The driver, who may sit on seat 103, steers electric vehicle 10 through handlebar 15 which includes brakes and horn 15A. The driver is protected by front panel or guard 160 and front mudguard 170 and may comfortably place feet on floorboard 71.

[0041] Electric vehicle 10 has an electric motor 20 and transmission system 80 are closely coupled and forming an integrated motor-transmission assembly 208, powered by an electric battery module 24 comprising a single battery as shown in FIGS. 1 to 4. Electric battery module 24 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.

[0042] Electric motor 20 has a rating of 4 kW to 10 kW (though this rating is dictated by application) and is controlled by vehicle control unit (VCU) 100. Electric battery module 24 including at least one battery 24 each with 48-volt rating provides electric power to motor 20. Electric battery module 24 is located below the seat 103 and the luggage compartment 105, of the scooter 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 24 includes a protective frame structure 23.

[0043] Battery module 24 requires to be securely connected to the rear frame portion 13 and a number of locking means, in the form of nut and bolt fasteners, are used for this purpose.

[0044] Scooter 10 includes a frame 11 as mentioned above and this frame structure, which supports the electric battery module 24 and the motor-transmission assembly 208 along with further vehicle components. Frame 11 is described in the

[0045] Applicant's co-pending Indian Patent Application, filed under application number 201 821 0471 88 dated 13 Dec. 2018 and is therefore no further described here. It may be noted, however, that the electric battery module 24 is a relatively heavy vehicle component. For scooter 10, a substantially equal weight distribution along the length of the scooter 10 is highly desirable to enable a driver to balance weight distribution in order to balance the scooter 10 during driving. To that end, the electric battery module 24 is located centrally along the width of the scooter 10, at a central lower location along the length of the scooter 10 below rear portion of the frame 13. This central lower position of the battery module 24 relative to scooter 10 effectively defines the centre of gravity (CG) of the scooter 10. Such CG location helps in improving driving stability, handling and overall efficiency of the scooter 10.

[0046] Referring to FIGS. 3 to 7(d), scooter 10 is provided with a rear mono-suspension i.e. only one shock absorber 94 on the motor-transmission system 20/80 side of scooter 10 as most load is on this side. Shock absorber 94 is desirably of the SNS type as described in Indian Patent No. 695/MUM/2005, is used to provide rear suspension to reduce cost. Shock absorber 94 is located at the rear of scooter 10 rather than at its centre.

[0047] The motor 20 and transmission 80 are closely coupled and mounted within dimensions of the rear wheel 84 as specifically shown in FIG. 7(a). This helps in a compact packaging without hampering the overall length of the vehicle and also provides good aesthetic. The motor-transmission casing 208B forms a structural element of the rear suspension system. Motor-transmission casing 208B acts as a swing arm since it is pivotally mounted both to a mounting bracket portion 133, connecting with a tube 13 of frame 11, at pivot joint 198 forward of the rear wheel 84 and to shock absorber 94 at a pivot joint 209. The shock absorber has a fixed mounting to mounting bracket 194 connected to a rear tube 13C of the rear frame portion 13. Such mounting allows the motor-transmission assembly 208 to vertically pivot in the manner of a swing arm. As scooter 10 moves along a road, the shock absorber 94 spring element is variably placed into tension and compression, the motor-transmission casing 208B correspondingly pivoting as a swing arm absorbing shocks from bumps in the road. Also, the transmission casing 208B absorbs the shocks & braking torque and hence there is no need to provide any separate member to take counter breaking torque. The cost and weight of a dedicated swing arm is thereby avoided.

[0048] The mounting arrangements described above also allow the transmission casing 2083 to act as a support member for the rear suspension system. The further pivot joint 209 is provided on the casing 208B itself which helps in securely mounting one end of the shock absorber 94. This option avoids any requirement for providing separate and specialised suspension mounting arrangements thereby helping to reduce complexity and cost.

[0049] Further features of the transmission system 80 which transmits torque from electric motor 20 under the supervision of vehicle control unit 100 are now described with reference to FIG. 9. The transmission system 80 is a single speed or single reduction type transmission. The number of reduction stages in the transmission system 80 may vary based on vehicle requirements. A fixed ratio double stage transmission system 80 with a single pair of input and output gears is used. The motor 20 is closely coupled with the transmission system such that an output shaft 120 of motor 20 is proximate to the input shaft of transmission system 80 and connected to transfer the torque generated by the motor 20. The number of reduction stages corresponds to a number of gear pairs. The output shaft 120 of the motor 20 is connected to the input shaft 801 of transmission system through a first gear pair 301, 302. According to one of the embodiment, the output shaft 120 of the motor including input gear 301 is supported at four locations i.e. at both the ends (910 & 940) one end being in motor housing 20A while other end is supported at transmission housing 80A. The output shaft 120 is also supported at middle section using bearings (930,940) provided at motor housing 20A and transmission housing 80A. The input shaft is supported at both ends by bearings, which in turn is supported in transmission housing 80A. The primary input gear 302 is rotatably mounted on the input shaft 801 (integral in this case). The motor output shaft 120 is connected to input gear 301 coaxially by means of internal splines 120A, the arrangement is made such that the motor shaft 120 and input gear 301 connection lies within the input gear length supported by the aforementioned bearings. The input shaft 801 of the transmission system is connected to the output shaft 802 of transmission system 80 through a second gear pair 401, 402. The output shaft 802 is supported at two locations through bearings (402A, 402B). The vehicle centreline (CC) as shown in FIG. 9, passes between bearings at two locations (420A, 402B). The above described transmission & bearing arrangement helps in avoiding uneven forces (even distribution of load) acting on bearing, thereby maximizing bearing life and no extra bearings are needed to support the shaft. Output torque received from the transmission system 80 is then transmitted to the rear wheel 84 of the scooter as the output shaft 802 of transmission system 80 is directly connected to the axle of the rear wheel 84. A suitable drive, such as a belt drive, may be used to transmit the power from motor to wheel.

[0050] According to another embodiment of present disclosure, the transmission system is further improved as shown in FIG. 10. Instead of separately providing motor housing 20A and transmission housing 80A, both the housings are integrated into a single housing 2080. This eliminates the various problems such as noise, difficulty in assembling two different housings with mounting of motor output shaft 120 etc. The motor output shaft 120 is supported at three locations (910, 940 & 1000) instead of four locations, this helps in reducing noise as well as helps in easy assembly. The shaft 120 is supported only at a common single location (1000) in middle location whether both the housings (20A & 80A) are integrated. Both the ends of the motor output shaft 120 are supported at housing 2080 using bearings (910 & 940) as in previous embodiment. In order to restrict any uneven load from acting on bearings (910, 940, 1000) the input gear 301 is clamped with the help of a nut 995. One bearing pair is therefore eliminated thereby reducing complexity & cost.

[0051] The motor output shaft 120 is provided with an input gear 301 as an integral part of the motor output shaft 120. The motor output shaft 120 is provided with teeth on its outer periphery to mesh with an input gear 301 of first gear pair. Due to the backlash provided between the internal teeth of input gear 301 and the teeth of motor output shaft 120 a noise is produced especially due to sudden acceleration or deceleration at low speed level. In order to obviate this noise a silent bush 177 is introduced as illustrated in FIGS. 11a and 11b. The input gear 301 is fitted and fixed on the motor output shaft 120 with a help of a bolt 137 meshed with the internal threads provided on the inner part of the motor output shaft 120. The bush 177 is mounted in gap created between bolt 137 and inner surface of input gear 301. The bush 177 helps in eliminating the problem by absorbing the noise.

[0052] A cover 208A is desirably mounted over the transmission casing 208B to direct air flow towards the motor 20. Such cover 208A, shown schematically in FIG. 7d is typically designed to improve vehicle aesthetics.

[0053] 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 disclosure.