JPH05213253A - Motor-operated vehicle of two rear wheels - Google Patents

Abstract

PURPOSE:To provide a motor-operated vehicle of two rear 7 wheels which rationalizes and uniformizes front and rear wheel load distribution through rational arrangement of a mounting device by means of an independent suspension type electric power unit, improves a maneuvering feeling and a riding feeling through reduction of the weight of a spring for rear wheels, improves the layout properties of a mounted apparatus, and improves running stability through lowering of the center of gravity of a vehicle. CONSTITUTION:A right and left independent suspension type electric power unit 16 is arranged to the central lower part of a car body frame 10 in a manner to be capable of swing. Rear wheels 17 are suspended from the rear end part of the electric power unit 16. The electric power unit 16 forms integral structure such that a drive motor 30, reduction gears 31 and 33, and a power transmission mechanism are formed integrally with swing arms 35. Meanwhile, a battery 26 is arranged below a driver seat 19 and between both swing arms 35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear two-wheel electric vehicle applied to small-sized three- and four-wheel vehicles, and more particularly to a rear two-wheel electric vehicle provided with an electric power unit for independently suspending left and right rear wheels.

[0002]

2. Description of the Related Art In a small three-wheeled vehicle, a rigid axle type rear wheel drive system has been considered in order to drive the left and right rear wheels. This rear wheel drive system is equipped with a drive motor, and transmits the rotational drive force from the drive motor to the differential mechanism via a reduction gear mechanism, and drives the left and right rear wheels from this differential mechanism via the rear axle. ing.

This rigid axle type rear wheel drive system has a construction in which a single drive motor drives a differential mechanism via a reduction gear mechanism to simultaneously obtain propulsive forces for the left and right rear wheels.

[0004]

In a small three-wheel vehicle that employs a rear axle drive system of a rigid axle system, a heavy drive motor, reduction gear mechanism, differential mechanism, etc. are designed as an integral rigid body, and It is common to arrange and fix them intensively from the rear side to the rear wheel side. For this reason, the weight is concentrated from the center of the rear wheel to the lower part of the seat, the load acting on the rear wheel is increased, and the unsprung weight of the rear wheel is large, which reduces the road grip and reduces the steering feel. The ride quality was not favorable.

Further, in this small three-wheeled vehicle, since the drive motor, the differential mechanism and the like are concentratedly arranged in the lower rear part of the center of the vehicle body, it is difficult to secure a space for mounting the battery, and the battery mounting place is occupied by the occupant. It interfered with the position of the feet, and there were layout-related difficulties in the placement of the onboard equipment. Furthermore, since there is only one drive motor, a large-capacity motor must be used, resulting in high cost.

The present invention has been made in consideration of the above-mentioned circumstances, and by the electric power unit of the independent suspension system, the mounted equipment is rationally arranged to optimize and equalize the front and rear wheel load distribution. An object of the present invention is to provide a rear two-wheeled electric vehicle that reduces unsprung weight of wheels to improve the steering feeling and the riding comfort.

Another main object of the present invention is to provide an electric vehicle for a rear two-wheel vehicle in which the onboard equipment is rationally arranged to improve the layout and the running stability is improved by lowering the center of gravity of the vehicle. It is in.

Another object of the present invention is to reduce the motor excitation force by a drive motor provided in an electric power unit for independently suspending the left and right rear wheels, and improve the durability and reliability of the motor. To provide an electric vehicle for use.

Still another object of the present invention is to provide a rear two-wheeled electric vehicle capable of increasing the capacity of a battery mounted between swing arms of an electric power unit.

Another object of the present invention is to set the ground height of the drive motor appropriately to lower the center of gravity of the vehicle while improving the cooling performance of the drive motor so that the drive motor interferes with the foot of the operator. An object of the present invention is to provide an electric vehicle for a rear two-wheel vehicle that reliably prevents

Another object of the present invention is to provide a rear two-wheeled electric vehicle which improves the balance of loads on the front and rear wheels and improves the steering stability of the vehicle by lowering the center of gravity.

Still another object of the present invention is to provide an electric vehicle for a rear two-wheel vehicle which can form a swing arm fulcrum which is lightweight and has a large strength by one arm mounting bracket and which is easy to maintain, inspect, disassemble and assemble. is there.

[0013]

According to the present invention, there is provided an electric vehicle for two-wheeled rear wheels according to the present invention.
As described above, a left and right independent suspension type electric power unit is swingably provided in the lower center of the vehicle body frame, and a rear wheel is suspended at the rear end of each electric power unit, and the electric power unit includes a drive motor, a speed reducer and a power transmission. While the mechanism is integrally provided with the swing arm to form an integrated structure, a battery is arranged between the swing arms below the seat.

In order to solve the above-mentioned problems, in the two-wheeled electric vehicle according to the present invention, as described in claim 2, the power transmission mechanism is a shaft drive mechanism having a drive shaft, Pass this drive shaft into the square pipe of the swing arm,
As described in claim 3, the electric power unit is provided with a drive motor in front of the swing arm, and the motor shaft center of the drive motor is located below the center of the longitudinal axis of the swing arm. As described above, the reduction gear device has the primary reduction gear mechanism provided on the output side of the drive motor and the secondary reduction gear mechanism provided on the output side of the power transmission mechanism, and the electric power unit uses the fulcrum to the body frame as the center of gravity of the drive motor. It is located near.

Further, in the rear two-wheel electric vehicle according to the present invention, the arm mounting bracket is provided at the lower center of the vehicle body frame as described in claim 5, and the swing arm fulcrum forming portions are formed on both sides of the arm mounting bracket. The left and right independent suspension type electric power units are swingably provided at the swing arm fulcrum formation portion, and the rear wheels are suspended at the rear end portions of the respective electric power units.

[0016]

In this rear two-wheel electric vehicle, the left and right independent suspension type electric power units for suspending the rear wheels are swingably provided at the lower center of the body frame, and each electric power unit includes a drive motor, a speed reducer, and a power transmission mechanism. Since it is integrated with the swing arm and configured as an integrated structure, the mounted equipment can be arranged with a reasonable degree of freedom, and the front and rear wheel load distribution can be optimized and equalized. Since the suspension type electric power unit does not concentrate the load near the rear wheel side, the unsprung weight of the rear wheel is reduced, and the road surface grip force is improved in combination with the improvement of the front and rear wheel load balance. Feeling and riding comfort are improved.

In addition, an independent suspension type electric power unit is swingably provided at the lower center of the vehicle body,
While improving the layout of the equipment arrangement, the center of gravity of the vehicle can be lowered, and the running stability can be improved.

On the other hand, by providing each drive motor to the electric power unit, the rear wheel drive force can be shared by a plurality of drive motors, and the motor excitation force of each drive motor can be reduced, thus improving the durability and reliability of the motor. Can be made

Further, the space between the swing arms of the left and right electric power units is widened, and the battery is mounted between the swing arms, so that the battery installation space can be widened and the capacity of the battery can be increased.

Furthermore, the arm mounting bracket is provided at the lower center of the vehicle body, and the swing arm fulcrum forming portions projecting laterally are provided on both sides of the mounting bracket, which facilitates the installation of the electric power unit and facilitates maintenance.
Easy inspection, assembly and disassembly.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of an electric vehicle for rear two wheels according to the present invention will be described below with reference to the accompanying drawings.

The rear two-wheel electric vehicle according to the present invention is applied to a saddle-ride type three- and four-wheel vehicle for running on uneven terrain and a straddle-type or seat-type three- and four-wheel vehicle. 1 to 3 show an example in which the rear two-wheeled electric vehicle of the present invention is applied to a scooter type electric three-wheeled vehicle.

This scooter type electric tricycle includes an underbone type vehicle body frame 10, and a front fork 11 is provided at a front end portion of the vehicle body frame 10. The front wheel 12 is supported at the lower end of the front fork 11,
The front wheel 12 is steered by a steering wheel 13.

A subframe 15 is fixed to the lower center of the vehicle body frame 10 or is supported by a rubber bush or the like in a float type, and independent suspension type electric power units 16 and 16 are paired from the outside to the left and right. It is provided so that it can swing. Each electric power unit 16,
Rear wheels 17, 17 are respectively supported at the rear ends of 16. The swing of the electric power unit 16 is buffered by a pair of left and right buffer units 18 interposed between the rear end of the electric power unit 16 and the rear portion of the vehicle body frame 10.

A seat seat 19 is attached to the upper center of the body frame 10 to form a seat portion, and a space between the seat seat 19 and the front portion of the body frame 10 is deeply curved into a U-shape so as to be stepped. A board 20 is mounted, and a leg shield 21 is provided in front of the step board 20. The rear portion of the vehicle body frame 10 is covered with a rear cowling 22 which also serves as a rear cover. The rear cowling 22 is continuous from the step board 20 to the rear.

On the other hand, the electric power units 16 provided in the lower central part of the vehicle body frame 10 are provided as a pair on the left and right, and the battery holder device 25 is installed between the paired electric power units 16 and 16. The battery 26 is mounted on the. The battery holder device 25 has a frame holder assembly 27 that is fixed by the lower central part of the vehicle body frame 10 and the upper part thereof, and the battery 26 is installed on the support frame (or support plate) of the frame holder assembly 27. ..

Further, a pair of left and right electric power units 1
Since 6 and 16 are symmetrically configured, the right electric power unit will be representatively described below.

The electric power units 16 and 16 are shown in FIG.
Further, as shown in FIG. 5, an electric drive motor 30, a primary reduction mechanism 31 that reduces the rotational drive force from the drive motor 30, and a power transmission mechanism that transmits the reduced rotational drive force to the rear wheel 17 side. 32 and a secondary reduction mechanism 33 that reduces the rotational driving force transmitted to the swing arm 35 are integrally fixed to the swing arm 35 to form an integrated structure. The secondary reduction mechanism 33 projects outward from the secondary reduction mechanism 33. The rear wheel 17 is supported by the rear axle 36.

Drive motor 30 of electric power unit 16
Is provided below the front side of the primary reduction mechanism 31 so as to project forward in the horizontal direction. The drive motor 30 is divided into an electric motor unit 30a and a rotation sensor unit 30b, and the rotation sensor unit 30b is located in front of the electric motor unit 30a. The drive motor 30 is provided in each electric power unit 16 and is composed of a plurality of motors, so that the motor capacity can be reduced and the size thereof can be reduced. The minimum ground height H of the drive motor 30 is, for example, about 90 mm.

The primary reduction mechanism 31 for reducing the rotational driving force from the drive motor 30 has a gear box 37 supported by the vehicle body frame 10. The gear box 37 is made of a light metal such as aluminum or a metal material made of a light alloy, and has a mounting hole (swing fulcrum) 38 to the vehicle body frame 0 side as shown in FIGS. It is composed of a box housing 37a and a front housing 37b which are integrated as possible, and has a gear chamber 3 inside.
9 are defined. A primary reduction gear mechanism 31, such as a helical gear mechanism, is housed in the gear chamber 39.

The swing arm 35 of the electric power unit 16 is integrally attached to the gear box 37 of the primary reduction mechanism 31 by bolting or the like. As shown in FIGS. 8 and 9, the swing arm 35 is formed of a square pipe in a square tube shape and extends rearward. On the other hand, mounting plates 40 also serving as reinforcements are fixed to both ends of the arm.
Via one end of the gearbox 37 of the primary reduction mechanism 31
The other end is fixed to the gear box 41 of the secondary reduction mechanism 33. The reduction gears 31 and 33 form a transmission gear of the reduction gear transmission.

As shown in FIG. 9, the cross section of the swing arm 35 is formed in a vertically long rectangular cross section in which the vertical direction is longer than the horizontal direction, and the drive shaft mechanism as the power transmission mechanism 32 is inserted through the inside of the swing arm 35. It is supposed to be done. This drive shaft mechanism has a drive shaft 44 that transmits the rotational driving force of the primary reduction gear mechanism 31 to the secondary reduction gear mechanism 33. The driven gear 45 of the primary reduction mechanism 31 is axially mounted on the front end of the drive shaft 44, and the drive gear 4 of the secondary reduction mechanism 33 is mounted on the rear end thereof.
6 is mounted. Drive shaft 44 is bearing 4
The oil seal 4 is rotatably supported by 7, 48.
The shaft is liquid-tightly sealed by 9,50.

The secondary reduction mechanism 33 is a reduction gear mechanism that reduces the rotational driving force transmitted via the drive shaft mechanism 32, converts the driving direction by 90 degrees, and transmits it to the rear axle 36. For example, a bevel gear mechanism. Composed.

As shown in FIG. 5, the secondary reduction mechanism 33 has a gear box 41 made of light metal such as aluminum or a light metal which is integrated by bolting so as to be divided into three parts. This gear box 41 has an inner box 41a also serving as a box cover shown in FIGS. 10 (A) and 10 (B) and FIG. 11 (A).
The center box 41b shown in (B) and FIG. 12 (A)
An outer box 41c shown in (B) is provided, and a gear chamber 52 is liquid-tightly defined therein. This gear room 52
A drive shaft 46 axially mounted on the drive shaft 44 and a driven gear 53 axially mounted on the rear axle 36 shown in FIG. 13 are housed and meshed with each other so as to be substantially orthogonal to each other.

The gear box 41 rotatably supports the rear axle 36 with bearings 54 and 55, while keeping the inside of the gear chamber 52 liquid-tight by an oil seal 56.
The rear axle 36 projects outward from one side of the gear box 41, and a spline portion 57 is formed on the projecting portion. The rear wheel 17 is rotatably and integrally mounted on the spline portion 57.

In this way, the electric power unit 16 includes the drive motor 30, the primary reduction mechanism 31, and the power transmission mechanism 3.
2. The secondary deceleration mechanism 33 is integrally attached to the swing arm 35, and is configured as an integrated (integrated) structure as a whole.
The electric power units 16 and 16 forming a pair on the left and right are formed in an independent suspension system in which they swing independently, and the left and right electric power units 16 and 16 suspend the left and right rear wheels 17 and 17 independently.

At this time, in the electric power units 16 and 16 for independently suspending the left and right rear wheels 17 and 17, the swing arm 35 has a vertically elongated rectangular cross section as shown in FIG. Since the drive shaft 44 that constitutes the transmission mechanism 32 is passed through, the space between the left and right swing arms 35, 35 can be widened within the legally limited left and right rear wheels 17, 17 width. For this reason, the storage space for the battery 26 mounted between the left and right swing arms 35 becomes large, and the battery 26 having a large capacity can be installed in this storage space. Further, since the electric power unit 16 uses a rectangular tube having a wider width in the bending stress direction acting on the swing arm 35, the bending strength is increased, which is advantageous in strength.

As the swing arm 35 of the electric power unit 16, an arm frame 35A having a C-shaped cross section may be used instead of the rectangular pipe shown in FIG. 14, or a circular cross section may be used. In the case of a circular cross section, it is more preferable that the space-corresponding portion of the battery storage portion is flattened so that the vertical direction is vertically long.

Further, in the drive motor 30 of the electric power unit 16, as shown in FIGS. 1, 3 and 4, the motor axis is the longitudinal axis of the swing arm 35 (the shaft of the drive shaft 44 constituting the power transmission mechanism 32). Since it is arranged below the axis) (in the ground direction), the drive motor 30 can be laid out without interfering with the rear lower part of the occupant's foot (heel), and a reasonable layout is possible.

The drive motor 30 can be installed so as to be balanced left and right so that the ground height H is an appropriate height, and the drive motor 30 which is a heavy object is set so as to have the lowest ground height of the scooter type electric tricycle. As a result, the center of gravity of the electric tricycle can be lowered, and traveling stability is improved. Further, since the drive motor 30 is exposed to the lower side of the vehicle, traveling wind directly hits it, the cooling performance of the motor can be improved, and the maintainability such as replacement of the drive motor 30 becomes good.

Further, in the electric power unit 16 of the left and right independent suspension system, the drive motor 30 is the component having the largest weight, and the center of gravity G of the drive motor 30 is brought to the swing fulcrum P of the electric power unit 16 at a low position. Therefore, the equivalent unsprung weight of the rear wheel can be reduced, and the riding comfort can be improved.

As in the conventional electric three-wheeled vehicle, when the drive motor, the speed reducer, and the differential mechanism are centrally arranged and integrally formed and the unsprung weight of the rear wheel is achieved, the unsprung weight is obtained. However, while the riding comfort becomes uncomfortable due to the increase in the driving force, the strength of related supporting parts such as the drive motor must be increased. Therefore, the unsprung weight is further increased, and since the drive motor is also an unsprung part, it is required to use the drive motor in consideration of vibration resistance, and there is a problem in durability.

However, these problems can be solved by positioning the center of gravity G of the heavy drive motor 30 near the swing fulcrum P of the electric power unit 16, while reducing the equivalent unsprung weight. The vibration resistance and durability of the drive motor 30 can be improved. Further, the reduction of the unsprung weight of the rear wheel 17 improves the grip force on the tire road surface.

When viewed as an electric three-wheeled vehicle as a whole, independent suspension type electric power units 16 and 16 are symmetrically provided in the lower center of the body frame 10, and each electric power unit 16 and 16 has a drive motor 30 and a primary reduction mechanism. Since the weight of 31 is near the center position of the vehicle body, front and rear wheels 1
The load portion acting on Nos. 2 and 17 can be optimized and equalized to improve the load balance, and the steering stability as a vehicle becomes good. Especially, the ease of riding in the low speed range is improved.

In the embodiment, the scooter type electric three-wheeled vehicle has been described. However, when the scooter type two-wheeled vehicle is applied, the unsprung weight can be reduced and the same effect can be obtained.

Further, in the embodiment, the drive motor 30 is set in front of the swing fulcrum P of the electric power unit 16 of the left and right independent suspension type.
If the center of gravity G of 0 is located near the swing fulcrum, the drive motor 30 can be set behind the swing fulcrum P. In this case, the drive motor 30 may be of a vertical type, and a bevel gear mechanism may be adopted as the primary reduction mechanism 31 instead of the helical gear mechanism. Further, instead of adopting the shaft drive mechanism as the power transmission mechanism, a chain mechanism or a belt mechanism may be used.

16 to 18 show another embodiment of the scooter type electric tricycle.

In the scooter type electric tricycle shown in this embodiment, the electric power units 16 and 16 are attached to the vehicle body frame 1.
The support structure for supporting 0 is basically different from that of the electric tricycle shown in the embodiment, and other configurations are substantially the same. Therefore, the same reference numerals are given and description thereof will be omitted.

In the scooter type electric tricycle shown in FIGS. 16 to 18, the arm mounting bracket 60 is attached to the lower center of the body frame 10. This arm mounting bracket 60
Is fixed to the rear end of the main frame 10a of the body frame 10 in a cantilever manner, or is attached to the rear end of the main frame 10a around the fulcrum so that it can swing, for example, several degrees to several tens of degrees. Good.

The arm mounting bracket 60 extends rearward and upward from the lower central portion of the vehicle body frame 10, and a swing arm fulcrum forming portion 61 projecting to both sides is integrally formed at the rear end portion thereof. The electric power units 16, 16 are swingably and detachably supported from the outside on the swing arm fulcrum formation portion 61.

The arm mounting bracket 60 is supported in a cantilever shape from the lower center of the vehicle body frame 10 to the rear upper side, and has swing arm fulcrums forming portions 61 projecting outwardly on both sides at its rear end. By supporting the electric power units 16, 16 of the left and right independent suspension system in a swingable manner on 61, it is possible to sufficiently secure the inter-wheel (tread) between the left and right rear wheels 17, 17, and at the same time, the left and right electric power units 16, A battery mounting space can be secured between the 16 swing arms 35.

The number of the arm mounting bracket 60 mounted on the vehicle body frame 10 may be one, and the swing arm fulcrum forming portion 61 can be composed of one rod or pipe, and can form a swing arm fulcrum that is lightweight and has high strength. .. Further, since the left and right electric power units 16, 16 can be easily attached to and detached from the arm mounting bracket 60, maintenance, disassembly, inspection and assembly of the electric power units 16, 16 can be facilitated.

[0053]

As described above, in the two-wheeled electric vehicle according to the present invention, the left and right independent suspension type electric power units are swingably provided at the lower center of the body frame, and the rear end portions of the electric power units are provided. Suspend the rear wheel,
Since the electric power unit has a drive motor, a speed reducer and a power transmission mechanism which are integrally provided with the swing arm to have an integrated structure, the mounted equipment can be rationally arranged with a degree of freedom, and the front and rear wheel load distribution can be improved. It is possible to optimize and equalize, and because the independent suspension type electric power unit does not concentrate the load near the rear wheel side, the unsprung weight of the rear wheel is reduced and the load balance between the front and rear wheels is reduced. Combined with the improvement of, the road surface grip is improved and the driving feeling and riding comfort are improved.

In addition, an independent suspension type electric power unit is swingably provided at the lower center of the vehicle body,
While improving the layout of the equipment arrangement, the center of gravity of the vehicle can be lowered, and the running stability can be improved.

On the other hand, by providing each drive motor to the electric power unit, the rear wheel drive force can be shared by a plurality of drive motors, and the motor excitation force of each drive motor can be reduced, thus improving the durability and reliability of the motor. Can be made

Furthermore, by widening the swing arms of the left and right electric power units and mounting the battery between the swing arms, the battery installation space can be increased and the capacity of the battery can be increased.

Further, the arm mounting bracket is provided at the lower center of the vehicle body, and the swing arm fulcrum forming portions projecting to the side are provided on both sides of the mounting bracket, so that the electric power unit can be easily mounted and the electric power unit of the electric power unit can be easily mounted. Easy maintenance, inspection, disassembly and assembly.

[Brief description of drawings]

FIG. 1 is an overall side view showing an embodiment in which a rear two-wheel electric vehicle according to the present invention is applied to a scooter type electric three-wheel vehicle.

FIG. 2 is a plan view showing the scooter type electric tricycle shown in FIG.

FIG. 3 is a rear view of the scooter type electric tricycle shown in FIG.

FIG. 4 is a diagram showing an electric power unit mounted on the scooter type electric tricycle of FIG. 1.

5 is a plan sectional view showing a rear side of the electric power unit shown in FIG.

FIG. 6 is a vertical cross-sectional view showing a gear box of a primary reduction mechanism of an electric power unit.

FIG. 7 is a view taken along line VII-VII of FIG.

FIG. 8 is a side view showing a swing arm provided in the electric power unit.

FIG. 9 is a view taken along line IX-IX in FIG.

10A is a diagram showing an inner gear box provided in the secondary reduction mechanism of the electric power unit, and FIG. 10B is a sectional view taken along line XB-XB of FIG. 10A.

11A is a sectional view taken along line XIA-XIA of FIG. 11B, showing a center gear box of the secondary reduction mechanism. FIG. 11B is a view taken along line XIB-XIB of FIG.

12 (A) shows an outer gear box of the secondary reduction mechanism, and is a sectional view taken along line XII A-XII A in FIG. 12 (B), and FIG. 12 (B) is shown in FIG. 12 (A). The figure which follows the XII B-XII B line of an outer gear box.

FIG. 13 is a diagram showing a rear axle supported by a secondary reduction mechanism.

FIG. 14 is a diagram showing an arrangement example of a swing arm of an electric power unit.

15 shows another arrangement shape of the swing arm shown in FIG.

FIG. 16 shows another embodiment of the electric vehicle for rear two wheels according to the present invention, and is an overall side view of a scooter type electric tricycle.

17 is a plan view of the scooter type electric tricycle shown in FIG. 15. FIG.

FIG. 18 is a rear view of the scooter type electric tricycle shown in FIG. 15.

[Explanation of symbols]

 10 Body Frame 12 Front Wheel 15 Subframe 16 Electric Power Unit 17 Rear Wheel 18 Buffer Unit 19 Seat Seat 20 Step Board 25 Battery Holder Device 26 Battery 30 Drive Motor 31 Primary Reduction Mechanism 32 Power Transmission Mechanism 33 Secondary Reduction Mechanism 35 Swing Arm 36 Rear Axle 37 Gear box 41 Gear box 44 Drive shaft 60 Arm mounting bracket 61 Swing arm fulcrum formation part

Claims (5)

[Claims] 1. A left and right independent suspension type electric power unit is swingably provided at a lower center portion of a body frame, and a rear wheel is suspended at a rear end portion of each electric power unit, and the electric power unit is a drive motor, a speed reducer and a power transmission. An electric vehicle for a rear two-wheel vehicle, characterized in that a mechanism is integrally provided with a swing arm to form an integrated structure, and a battery is arranged between both swing arms below a seat. 2. The rear two-wheel electric vehicle according to claim 1, wherein the power transmission mechanism is a shaft drive mechanism having a drive shaft, and the drive shaft is passed through a square pipe of a swing arm. 3. The rear two-wheel electric vehicle according to claim 1, wherein the electric power unit is provided with a drive motor in front of the swing arm, and a motor shaft center of the drive motor is located below a longitudinal axis center of the swing arm. 4. The reduction gear transmission has a primary reduction gear mechanism provided on the output side of the drive motor and a secondary reduction gear mechanism provided on the output side of the power transmission mechanism, and the electric power unit has a fulcrum to the vehicle body frame as the drive motor. The rear two-wheeled electric vehicle according to claim 1, wherein the electric vehicle is located near the center of gravity of the vehicle. 5. An arm mounting bracket is provided at the lower center of the vehicle body frame, and swing arm fulcrum forming portions are projected from both sides of the arm mounting bracket. An electric vehicle for a rear two-wheel vehicle, which is swingably provided and has a rear wheel suspended at a rear end portion of each electric power unit.