Swing Arm Structure for Saddle-Type Electric Vehicle and Saddle-Type Electric Vehicle Thereof

FIELD OF THE INVENTION

[001] The present invention relates to saddle-type electric vehicle. More particularly, relates to a swing structure for the saddle-type electric vehicle.

BACKGROUND OF THE INVENTION [002] Typically, in saddle-type electric vehicle, a hub motor is commonly located in a rear wheel of vehicle. In such electric vehicle, a motor casing or a powertrain casing act as a swing arm for the vehicle.

[003] In conventional electric vehicles, a powertrain casing RH and a cover transmission is constructed to store oil required for lubrication of components in the powertrain, which includes a gear drive and shafts. However, as volume of the casing and the transmission cover is filled with oil, sealing of the assembly becomes critical as each corner may cause leaking of oil. To ensure sealing a gasket can be provided or increase number of bolts, which increases the number of components and wastage of oil. [004] Further, due to higher volume of oil within the powertrain casing, churning losses are higher, inherently affecting efficiency of the vehicle. Also, a chain drive that connects the motor and the rear wheel, is also required to be wet due to the oil filled within the powertrain casing and transmission cover. As such, dry chain-drive option is not present in the conventional electric vehicle. Moreover, components like sprocket are not required to be dipped in oil constantly as this may cause unwanted resistance for the sprocket movement because of oil, which adds onto the churning losses of the vehicle.

[005] Additionally, oil present within the casing adds onto unsprung mass of the vehicle, which worsens the structural and vibrational strength of the electric vehicle, which is undesirable. Moreover, during maintenance where powertrain casing is required to be opened, oil wastage will be more as higher volume of oil is needed to be scrapped. As an example, if an operator is required to tighten the belt or replace the sprocket, the operator has to open the cover and then replace, which leads to also wastage of oil.

[006] In view of the above, there is a need for a swing arm structure for the saddle-type electric vehicle, which addresses one or more limitations stated above.

SUMMARY OF THE INVENTION

[007] In one aspect, a swing arm structure for a saddle type electric vehicle is disclosed. The swing arm structure includes a casing adapted to enclose an electric motor and a transmission assembly. The casing has a first end pivotally coupled to a frame member of the vehicle and a second end adapted to support a rear axle. The transmission assembly has a drive gear coupled to a motor shaft of the electric motor and a driven gear coupled to the rear axle. The drive gear and the driven gear are coupled to each other via an endless transmission drive for transferring motive force from the electric motor to the rear axle. An oil chamber is defined in the casing, wherein the oil chamber is adapted to encompass the drive gear for lubrication.

[008] In an embodiment, a transmission cover is adapted to be mounted onto a peripheral surface of the casing. The transmission cover is adapted to cover the electric motor and the transmission assembly.

[009] In an embodiment, a cover member is adapted to engage along periphery of the oil chamber. The cover member is adapted to cover the oil chamber.

[010] In an embodiment, the cover member includes an intermediate cover member mountable onto the oil chamber. The intermediate cover member has a slot for enabling extension of the endless transmission drive from the drive gear to the driven gear.

[011] In an embodiment, the endless transmission drive is one of a chain drive and a belt drive.

[012] In an embodiment, the electric motor is enclosed at a front portion of the casing. [013] In an embodiment, the casing is defined with an L-shaped profile for supporting the rear axle on one of a right side and a left side of the vehicle.

[014] In an embodiment, the drive gear is disposed proximal to the first end and the driven gear is disposed proximal to the second end.

[015] In another aspect, the straddle-type electric vehicle is disclosed. The vehicle includes a frame member and the swing arm structure. The structure includes the casing adapted to enclose the electric motor and the transmission assembly. The casing has the first end pivotally coupled to the frame member of the vehicle and the second end adapted to support the rear axle. The transmission assembly has the drive gear coupled to the motor shaft of the electric motor and the driven gear coupled to the rear axle. The drive gear and the driven gear are coupled to each other via the endless transmission drive for transferring motive force from the electric motor to the rear axle. The oil chamber is defined in the casing, wherein the oil chamber is adapted to encompass the drive gear for lubrication.

BRIEF DESCRIPTION OF THE DRAWINGS

[016] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.

Figure 1 is a perspective view of a saddle-type electric vehicle, in accordance with an embodiment of the present invention.

Figure 2 is a perspective view of the saddle-type electric vehicle, in accordance with an embodiment of the present invention.

Figure 3 is an exploded view of a swing arm structure of the vehicle, in accordance with an embodiment of the present invention.

Figure 4 is an exploded view of the swing arm structure of the vehicle, in accordance with an embodiment of the present invention.

Figure 5 is a schematic view of a casing of the swing arm structure, in accordance with an embodiment of the present invention.

Figure 6 is a schematic view of the casing of the swing arm structure, x in accordance with an embodiment of the present invention.

Figure 7 is a schematic view of the casing of the swing arm structure, in accordance with an embodiment of the present invention.

Figure 8 is a top sectional view of the casing of the swing arm structure, in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[017] Various features and embodiments of the present invention here will be discernible from the following further description thereof, set out hereunder.

[018] Figure 1 illustrates a schematic view of a saddle-type electric vehicle 200, in accordance with an embodiment of the present invention. As an example, the saddle-type electric vehicle 200 is a scooter type vehicle. The vehicle 200 includes an electric motor 202 (shown in Figure 4) and a transmission assembly 204 (shown in Figure 8) that is disposed behind a floorboard 218 and below a seat assembly 220 and/or a storage bin (not shown). The vehicle 200 has a front wheel 222, a rear wheel 224 and a frame member (not shown).

[019] A head pipe (not shown) connects to the frame member. The head pipe supports a steering shaft (not shown) and a front suspension 226 attached to the steering shaft through a lower bracket (not shown). The front suspension 226 supports the front wheel 222. The upper portion of the front wheel 222 is covered by a front fender 228 mounted to the front suspension 226. In an embodiment, the front fender 228 is movable along with the front wheel 222, during travel over undulations on a road surface. A handlebar 230 is fixed to upper bracket (not shown) and can rotate about the steering shaft for turning the vehicle 200. A headlight 232 and an instrument cluster 234 (shown in Figure 2) is arranged on an upper portion of the head pipe.

[020] Further, a rear suspension 236 (shown in Figure 2) is provided to the rear wheel 224 for dampening the vibrations induced during travel of the vehicle 200 over undulations on the road surface. A taillight unit 238 (shown in Figure 2) is disposed at the end of the vehicle 200 and at the rear of the seat assembly 220. A grab rail 240 is also provided for facilitating grip and/or balance to a rider on the vehicle 200 during movement. The rear wheel 224 is arranged below the seat assembly 220 and adapted to receive the motive force from the electric motor 202. The transmission assembly 204 transfers the drive force from the electric motor 202 onto the rear wheel 224 for movement the vehicle 200. In an embodiment, the driving force of the electric motor 202 is transmitted through an endless transmission drive 212 (shown in Figure 3). In an embodiment, the endless transmission drive 212 may be a chain drive or a belt drive. A rear fender 242 (shown in Figure 2) is disposed above the rear wheel 224.

[021] Referring to Figures 3-8 in conjunction with Figures 1 and 2, a swing arm structure 100 for the vehicle 200 is depicted. The swing arm structure 100 includes a casing 102 having a first end 102a pivotally coupled to the frame member of the vehicle 200 and a second end 102b adapted to support a rear axle 216 (shown in Figure 8). In an embodiment, the first end 102a is the end positioned towards a center portion of the vehicle 200 and the second end 102b is the end positioned at a rear portion of the vehicle 200. In an embodiment, the first end 102a of the casing 102 is provided with one or more mounting provisions 112 (shown in Figure 3) for enabling pivotal mounting with the frame member. The mounting provisions 112 engage onto either side (not shown) of the frame member for the pivotal mounting, in the present embodiment, the first end 102a of the casing 102 is mounted to a downtube (not shown) that extends downwardly from a main tube (not shown) of the frame member. The casing 102 is adapted to enclose the electric motor 202 and the transmission assembly 204. In other words, the swing arm structure 100 acts as an enclosure for the electric motor 202 and the transmission assembly 204. In an embodiment, the electric motor 202 is enclosed at a front portion or proximal to the first end 102a of the casing 102, so that the electric motor 202 is positioned below the seat assembly 220.

[022] Further, the transmission assembly 204 is mounted behind the electric motor 202. The transmission assembly 204 includes a drive gear 206 coupled to a motor shaft 208 of the electric motor 202 and a driven gear 210 (shown in Figure 5) coupled to the rear axle 216. As such, the drive gear 206 is disposed proximal to the first end 102a of the casing 102 and the driven gear 210 is disposed proximal to the second end 102b of the casing 102. The drive gear 206 and the driven gear 210 are coupled to each other via the endless transmission drive 212 for transferring motive force from the electric motor 202 to the rear axle 216. The rear axle 216 is coupled to the rear wheel 224, and thus the motive force received from the electric motor 202 drives the rear wheel 224 and in-turn the vehicle 200.

[023] In an embodiment, as shown in Figures 3 and 4, the casing 102 is a two-part structure, wherein the two-part structure includes the casing 102 (which can be a left-hand (LH) part and a transmission cover 214 (which can be a right-hand (RH) part). The transmission cover 214 is adapted to engage with a peripheral surface of the casing 102, thereby covering the electric motor 202 and the transmission assembly 204. The casing 102 and the transmission cover 214 upon assembly may form a housing for enclosing the electric motor 202 and the transmission assembly 204. In an embodiment, the engagement between the transmission cover 214 and the peripheral surface of the casing 102 is via conventionally known techniques such as snap-fit mechanism or a fastening mechanism or any other means as per design feasibility and requirement. In the present embodiment, snap-fit mechanism is employed for engaging the transmission cover 214 with the casing 102.

[024] In an embodiment, the drive gear 206 and the driven gear 210 may be provided with suitably gears or gear trains, according to transmission requirement of the vehicle 200. In other words, the gear ratios of the drive gear 206 and the driven gear 210 can be altered as per design feasibility and requirement of the vehicle 200.

[025] In an embodiment, the casing 102 is defined with an L-shaped profile (as shown in Figure 3), for supporting the rear axle 216 on one of a right side and a left side of the vehicle 200. Such a construction reduces the material usage while also enhancing aesthetic appeal of the vehicle 200.

[026] Further, an oil chamber 104 is defined in the casing 102 (as shown in Figure 7), such that the oil chamber 104 encompasses the drive gear 206 (as shown in Figure 7) for lubrication. The oil chamber 104 is defined by extending a rim surface 104a (as shown in Figure 7) from a base surface 114 (as shown in Figure 7). In an embodiment, the rim surface 104a is mounted onto the base surface 114 to form the oil chamber 104 within the casing 102. In the present embodiment, the oil chamber 104 encompasses the drive gear 206 along with a gear 244 (as shown in Figure 3) coupled to the motor shaft 208. Such a construction, isolates the oil chamber 104 from rest of the volume of the casing 102, thereby mitigating the need for filling the volume of the casing 102 with oil. Additionally, oil from the oil chamber 104 is also transferred to the entire transmission assembly 204 via the endless transmission drive 212, thereby ensuring lubrication even with reduced quantity of oil within the casing 102. Moreover, the requirement of sealing the entire casing 102 is prevented, thereby making the construction of the casing 102 simple, while ensuring reduced maintenance.

[027] In an embodiment, the oil chamber 104 is defined with a profile having the rim surface 104a that is adjacent to the outer diameters of the driver gear 206 and the gear 244, thereby conforming to a cone shaped profile.

[028] Further, a cover member 106 (as shown in Figure 3) is provided onto the oil chamber 104, for providing ingress protection to the oil chamber 104. The cover member 106 is adapted to engage along periphery of the oil chamber 104, thereby covering the oil chamber. The cover member 106 may be provided with a gasket member (not shown) for ensuring suitable sealing and/or ingress protection to the oil chamber 104. In an embodiment, the cover member 106 is mounted directly onto the oil chamber 104. In another embodiment, the cover member 106 is mounted onto the oil chamber 104 via an intermediate cover member 108 (shown in Figure 5). In other words, the cover member 106 includes the intermediate cover member 108, through which the cover member 106 is mounted onto the oil chamber 104. Further, for enabling extension of the endless transmission drive 212 between the drive gear 206 to the driven gear 210, the intermediate cover member 108 is defined with a slot 110. The slot 110 allows connection between the drive gear 206 to the driven gear 210 via the endless transmission drive 212, thereby ensuring transfer of motive force between the drive gear 206 to the driven gear 210 even when with the oil chamber 104.

[029] In an embodiment, the slot 1 10 is defined on an outer surface of the intermediate cover member 108 facing towards the driven gear 210. In an embodiment, the dimensions of the slot 1 10 is selected as per requirement.

[030] In an embodiment, the volume of the oil chamber 104 may be combination of the rim surface 104a, the base surface 114 (shown in Figure 7) of the casing 102 over which the rim surface 104a is defined and the cover member 106. As such, dimensions and configuration of the oil chamber 104 are selected based on the dimensions and configuration of the rim surface 104a and the cover member 106.

[031] In an embodiment, each of the casing 102, the cover member 106, the rim surface 104a, the intermediate cover member 108 are made of a metallic material, or a non-metallic material or a composite material, as per design feasibility and requirement.

[032] In another embodiment, dimensions and configuration of each of the casing 102, the cover member 106, the rim surface 104a, the intermediate cover member 108 is selected as per design feasibility and requirement.

[033] Advantageously, the present disclosure provides the swing arm structure 100 that provides an oil chamber 104 within the casing 102 that encloses the electric motor 202 and the transmission assembly 204. Such a construction, isolates the oil chamber 104 from rest of the volume of the casing 102, thereby mitigating the need for filling the volume of the casing 102 with oil. Also, oil from the oil chamber 104 is transferred to the entire transmission assembly 204 via the endless transmission drive 212 as per requirement, thereby ensuring lubrication even with reduced quantity of oil within the casing 102. Moreover, due to reduced volume of oil in the transmission assembly 204, churning losses in the vehicle 200 are drastically reduced, making the vehicle 200 more efficient. Further, the requirement of sealing the entire casing 102 is prevented, thereby making the construction of the casing 102 simple, while ensuring reduced maintenance. Additionally, due to separation of the oil chamber 104 from the casing 102, the requirement of draining and/or replacing oil for maintenance work such as adjustment of endless transmission drive 212 is prevented.

[034] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.

Reference Numerals

100 - Swing arm structure

102 - Casing

102a - First end of casing

102b - Second end of casing - Oil chamber a - Rim surface of oil chamber- Cover member - Intermediate cover member- Slot - Mounting provisions - Base surface of casing - Saddle-type electric vehicle - Electric motor - Transmission assembly - Drive gear - Motor shaft - Driven gear - Endless transmission drive - Transmission cover - Rear axle - Floorboard - Seat assembly - Front wheel - Rear wheel - Front suspension - Front fender - Handlebar - Headlight - Instrument cluster - Rear suspension - Taillight unit - Grab rail - Rear fender - Gear