WO2009044418A1

WO2009044418A1 - Drive train for electric scooters

Info

Publication number: WO2009044418A1
Application number: PCT/IT2007/000699
Authority: WO
Inventors: Antonio Bertini
Original assignee: Oxygen, S.P.A.
Priority date: 2007-10-05
Filing date: 2007-10-05
Publication date: 2009-04-09

Abstract

Drive train for electric scooters comprising an oscillating arm (12), designed to be articulated to the frame (11) of a scooter, and an electronically-controlled electric motor (14) whose stator (14a) is fixed to the oscillating arm (12) and whose rotor (14b) is fixed to the drive wheel (13). The electronic control means (22) of the electric motor (14) are arranged on the oscillating arm (12).

Description

TITLE

DRIVE TRAIN FOR ELECTRIC SCOOTERS

DESCRIPTION Field of the invention The present invention relates to the field of electric scooters, and more precisely concerns a drive train for electric scooters of the type with motor arranged inside the drive wheel.

State of the art As known, the typical structure of an electric scooter is, in its fundamental components, similar to the structure of a scooter with endothermic motor and consists of a central frame - that defines the flat support surface for the user's feet, the seating zone, the front leg-guard shield etc.-, and a rear oscillating arm articulated to the frame, supporting the motor and the drive wheel. Shock absorbing means are located between the oscillating arm and the frame. The assembly formed by the arm with the motor and the wheel is also "drive-train" . A first problem associated with this type of structure is common both to scooters with electric motors and to those with endothermic motors, and it concerns the fact that the mechanical transmission between the motor and the wheel requires constant maintenance in order to avoid problems of malfunctions and breakdowns. The use of a mechanical transmission moreover involves, as is known, power losses in the transmission itself.

With reference to a scooter with an electric motor

(generally a brushless motor) , a second problem is due to the overheating of the electronic control components of the electric motor which are arranged inside the body, or in zones associated with the central frame, such as for example the under- seat space or the front leg-guard shield. Excessive overheating can cause malfunctions of the electronic components. When it is possible, in order to avoid such problems, air inlets have been designed on the body. However, such air inlets are often poorly adapted to the overall stylistic line of the scooter as ideated by the designer.

Other problems are associated to the production steps of the electric scooter. In particular, the type of structure described above requires complicated assembly steps of the motor's oscillating arm, because of, for example, the mechanical transmission that must be mounted with great precision or also the passage of numerous cables connecting the electric motor with the electronic control components of the motor itself.

From this structural complexity there derives a plurality of problems, all concerning the quality control step of the motor, transmission and rear brake group of the scooter, which unavoidably can only be carried out once the scooter has been assembled in all its main components, with the risk of having to completely disassemble the structure if malfunctions are detected.

A solution aimed to resolve some of these problems concerns the use of an electric motor inserted in the drive wheel, with the stator of the motor fixed to the oscillating arm and the rotor fixed to the wheel rim.

Such a solution does not solve all the problems mentioned above, because it eliminates in practice only the mechanical transmission problem. Because of these limited advantages, this solution has not had a large commercial development.

The object of the present invention is to provide a drive train for electric scooters of the type with electric motor inserted in the drive wheel, that allows to solve the problems associated with the overheating of the electronic control components of the electric motor and, at the same time, facilitates the assembly operations of the scooter as well as the quality control steps of several of its components, ensuring a reliability comparable or superior to that of traditional drive train assemblies . Summary of the Invention

This object is achieved with a drive train for electric scooters comprising an oscillating arm, designed to be articulated to the frame of a scooter, and an electronically-controlled electric motor whose stator is fixed to the oscillating arm and whose rotor is fixed to the drive wheel, characterized in that it further comprises electronic control means of said electric motor arranged on said arm.

Brief description of the drawings Further characteristics and advantages of the drive train for electrical scooters according to the present invention will be made apparent from the following description of an embodiment thereof, made as not limiting example with reference to the appended drawings wherein: - figure 1 shows an axonometric view of the rear part of a scooter with the drive train according to the invention; figure 2 shows a cross section of the drive wheel of the drive train of figure 1, sectioned on the rotation axis, with the electric motor outlined in two parts (rotor and stator) ; figure 3 shows an exploded view of the drive train shown in figure 1.

Detailed description of the invention

With reference to the above figures, the central frame of a scooter is identified by the numeral 11 (in figure 1 only the rear portion is shown) . According to the invention, the drive train comprises an oscillating arm 12 articulated to the frame 11, as a support for the assembly formed by the drive wheel 13 with inserted electric motor

14. A shock absorber 15 is located between the oscillating arm and the frame .

The oscillating arm 12 provides for, at a first end, means 16 for the articulation to the frame 11, of known type, and, at a second end, a fixing zone 17 of the arm to the assembly formed by the electric motor 14 and the drive wheel 13, better described further on.

The oscillating arm 12 consists of an elongated box formed by two concaved shells 18a and 18b shaped in a corresponding manner and facing one another in order to define an inner housing 19. The shells are preferably constituted by aluminium castings. In particular, the inner shell (that is the shell nearest the drive wheel 13) is indicated with 18a, while the more external shell is indicated by 18b. The inner shell 18a has load-bearing functions . Between the corresponding edges of the two shells 18a and 18b, a gasket 20 is arranged. The mutual locking of the two shells occurs by means of a suitable number of fastening screws 21, of which only some are represented in the figures. According to the invention, the electronic control means of the electric motor 14, such as two electronic circuit boards 22 (sketched as a whole in the figures) , are arranged in the inner housing 19 of the rear oscillating arm 12.

A first circuit board is involved in the conversion of the electric power -accumulated in the traction batteries or generated by a power source- in electric power suitable for feeding the electric motor. A second circuit board computes the data coming from the sensors and from the scooter controls in order to act on the first circuit board. Moreover, this second board controls the communications between the electronic components. The two circuit boards can be integrated in a single board.

The zone of the oscillating arm 12, identified by the numeral 17, to which the electric motor 14 and drive wheel 13 assembly is fixed, consists of a cavity 23, whose axis is substantially parallel to the coupling direction of the two shells 18a and 18b; in this cavity a support body 24 of the electric motor 14 is inserted and locked.

In particular, the cavity 23 is defined by two coaxial cylindrical bushes 25a and 25b respectively obtained on the two shells 18a and 18b at the fixing area 17.

The external bush 25b has a closing cover 26, fixed to the edges of the same bush 25b, with the interposition of a further gasket 27, by means of screws 28. Between the edge of the support body 24 of the electric motor 14 inserted in the cavity 23, and the cover 26, substantially in correspondence with the external bush 25b, room is defined for the housing of first connectors 29a connecting the wires coming from the electronic circuit board 22 with the wires coming from the electric motor 14. Second connectors, identified by the numeral 29b

(outlined in figure 3) , connect the electronic circuit board 22 with the wiring coming from the central frame 11 (for the connection with the motor controls) .

The electric motor 14 is a brushless motor and includes a stator 14a and a rotor 14b (in figure 2 these two parts are schematised, for the sake of simplicity, as if they were formed from single-piece bodies) . The support body 24 projects from the stator 14a; such body 24 consists of a tubular portion integrally coupled with the inner bush 25a. The rotor 14b is fixed inside the wheel rim 13a of the wheel 13 by means of screws 13b (outlined in figure 2 through its axis) . Obviously, the wheel rotates integrally with the rotor.

The support body 24 is locked in the inner bush 25a by clamp means. Such clamp means consists of a through slit 24a formed in the side of the inner bush 25a; the slit 24a is parallel to the axis of the same inner bush. Screws 24b are inserted in complementary holes in the inner bush 25a at the opposite faces of the slit 24a, thus resulting in a clamping action of opposite parts of the bush 25a on the support body 24 by means of the screws 24b. A gasket 24c is inserted in the slit.

Advantageously, on the portion of the rotor 14b outside the wheel rim, a braking disc 31 of the rear disc brake system of the scooter is fixed by screws 30. Said braking disc 31 is coaxial with the axis of the electric motor 14 and therefore consists of a circular ring that coaxially encircles the support body 24. The hydraulic actuator of the rear disc brake system is fixed to the bottom of the inner shell 18a and is identified by the numeral 32. The clasp brake (not indicated in the figures) , is positioned at the support fork 33 fixed to the inner shell 18a. The provision of room on the oscillating arm for the arrangement of the electronic control means of the motor leads to a series of advantages, among which one of the more important is the improvement of the thermal dissipation of the same means. In fact, the electronic circuit boards that control the motor are one of the parts of the scooter which heat up most, due to the power losses on the electronic components. Therefore removing the heat of such components is one of the fundamental factors for the correct working of the scooter. Integrating all the electronics in one area of the scooter such as the rear oscillating arm, which is outside the body of the scooter and in direct contact with the outside air, allows a very efficient removal of the generated heat, thus reducing possible scooter working problems.

Although with a less effective results, the arrangement of the electronic control means of the motor on the oscillating arm in principle can be provided for example by inserting such electronics in a box which is subsequently fixed outside the arm, and not inside the arm (as indicated in the description of the preferred embodiment) .

The positioning of the electronic control means of the electric motor inside the oscillating arm involves a decrease in the amount of wiring (both in number and length) with respect to the case where the electronics are arranged on the central frame of the scooter. This reduces to a minimum the possibility of errors during the wiring step and reduces the losses along the wires. Moreover, the positioning of the electronic control means of the electric motor inside of the rear oscillating arm allows simplifying the quality control step. In fact, the quality control step of the entire "drive-train" can be made before the mounting on the scooter: the drive- train can be tested away from the assembly line before the assembling step to the scooter, considerably simplifying the operations and reducing the possible disassembly in case of malfunction detection. In the same quality control step it is possible to verify the functioning of the brake group and the testing of the brake pads.

Thanks to the new structure of drive train the line assembly is much easier and faster for the operator. This is due to the fact of having made the drive-train an integrated component externally preassembled from the assembly line.

The particular structure thus obtained facilitates the assembly and disassembly of the electronic control means of the motor, because they comprise only two electric connectors for the connection to the scooter's electrical system and two connectors for the connection to the motor (one for signal transmission and one for power transmission) . In particular, access to the connectors of the electronic control means to the motor is facilitated by the presence of a dedicated opening (closed by a cover) present on the external shell, thus assisting the disengagement of the wheel-motor assembly from the oscillating arm without having to disassemble the electronic control means from the scooter. Locking the stator of the electric motor in the rear oscillating arm is made extremely simple by the presence of the clamp means . The fact that the main electronics of the scooter is available in an easily accessible location ensures that inspection in case of failure can easily take place. In - S - fact it is sufficient to only unscrew the fastening screws of the external shell of the oscillating arm, without having to disassemble other parts of the frame.

Moreover, the fact of having integrated the control electronic means of the motor directly in the oscillating arm ensures that the drive train can be easily associated with different scooter frames.

Variants and/or changes may be made to the drive train according to the present invention without departing from the scope of the invention as set forth in the following claims.

Where any of the characteristics and techniques described in any of the claims are followed by reference signs, these have been included for the purpose of providing examples simply to increase the clarity of the claims and consequently, they have no limiting effect on the interpretation of each element they identify

Claims

1. Drive train for electric scooters comprising an oscillating arm (12) , designed to be articulated to the frame (11) of a scooter, and an electronically controlled electric motor (14) whose stator (14a) is fixed to said oscillating arm (12) and whose rotor (14b) is fixed to the drive wheel (13) , characterized in that it further comprises electronic control means (22) of said electric motor (14) arranged on said oscillating arm (12) .

2. Drive train for electric scooters, according to claim 1, characterized in that said electronic control means (22) of said electric motor (14) are arranged inside a housing (19) defined in said oscillating arm (12) .

3. Drive train for electric scooters, according to claim 2, characterized in that said oscillating arm (12) consists of a box formed by two concave shells (18a, 18b) shaped in a corresponding manner and facing one another to define said inner housing (19) in which said electronic control means (22) of the electric motor (14) are arranged, said electronic means (22) being associated with at least one first connector (29a) for the connection to the wiring coming from the electric motor (14) and at least one second connector (29b) for the connection, by means of wiring coming from the frame (11) of the scooter, with the electrical system of the scooter to which the drive train is articulated.

4. Drive train for electric scooters, according to one or more of the previous claims, characterized in that at one end of said oscillating arm (12) , a through cavity (23) is defined, in which is inserted and locked a support body (24) of the electric motor (14) integral with the stator (14a) of the same motor (14) , said cavity (23) having an opening towards the outside closed by a cover (26) , between the free end of said support body (24) and said cover (26) room being defined in which at least one connector (29a) is housed, said connector (29a) connecting said electronic means (22) with the wiring coming from the electric motor (14) .

5. Drive train for electric scooters, according to claims 3 and 4, characterized in that said cavity (23) is extended along an axis substantially parallel to the coupling direction of said two shells (18a, 18b) and consists of two coaxial cylindrical bushes (25a, 25b) respectively obtained on said two shells (18a, 18b) , said support body (24) of the electric motor (14) being inserted and locked in the bush (25a) nearest the drive wheel (13) .

6. Drive train for electric scooters, according to claim 4 or 5, characterized in that clamping means for locking said support body (24) are arranged in said cavity (23) .

7. Drive-train for electric scooters, according to claim 6, characterized in that said clamping means comprises a through slit (24a) formed in the side of said inner bush (25a) , said slit (24a) being parallel to the axis of the inner bush (25a) itself, screw means (24b) are inserted in complementary holes in said inner bush (25a) at the opposite faces of said slit (24a) providing for a clamping action of opposite parts of the inner bush (25a) on said support body (24) through said screw means (24b) .

8. Drive train for electric scooters, according to one or more of the previous claims, characterized in that on the portion of the rotor (14b) of the electric motor (14) outside the wheel rim of the drive wheel (13) , a braking disc (31) is fixed, said braking disc (31) being designed to form part of the rear brake disc system of the scooter, said braking disc (31) being coaxial with the rotation axis of the electric motor (14) , the clasp brake of the disc brake system being joined to the more internal shell (18a) of said oscillating arm (12) .

9. Drive train for electric scooters, according to one or more of the previous claims, characterized in that said shells (18a, 18b) are constituted by aluminium castings.

10. Drive train for electric scooters, according to one or more of the previous claims, characterized in that said electronic control means of the motor comprise at least one electronic circuit board.