BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a main body frame for an electric motorcycle and an electric motorcycle comprising the main body frame.

Description of the Related Art

In the art, electric motorcycles are often developed based on the overall design of combustion engine motorcycles, wherein the frames are retained with only minor adaptations. Respective motorcycle frames are known, which are made from metal tubes which are suitably bent and welded together. Such concept does not take full account of all potential of an electric motorcycle.

Also for an electric motorcycle, the frame has to be sufficiently rigid for coping with extreme situations and needs to have enough strength to sustain impacts to a certain amount, for example caused by falls. To fulfill these requirements, the tubes are usually made from steel such as ChroMoly steel. Steel has a relatively high density of about 7.75 to 8.05 g/cm3. Therefore, a frame made from steel tubes is heavy and adds significantly to the weight of the electric motorcycle.

Such a conventional electric motorcycle is therefore relatively heavy, typically above 100 kg, for instance, 130 kg, and thus difficult to handle, in particular for beginners but also for professionals, for instance, when used for jumps in trial races. Moreover, it is difficult to transport because it cannot be lifted by a single person and a common bicycle rack for transportation by car is not designed for such weight. Therefore, it is desirable to reduce the weight of the electric motorcycle and of its frame, especially the main body frame, as far as possible while maintaining a sufficiently high strength.

Moreover, as mentioned, steel tubes are usually welded together which does not allow to exchange parts. For example, in case of an accident, it can be desirable to replace only a damaged portion of the frame. It may also be desirable to have a motorcycle that allows adaptation to different driving situations, for instance to change the steering head so as to adjust the inclination of the front fork. This is hardly feasible with tubes which are welded together. Furthermore, in order to prevent the frame from becoming overly heavy, the side walls of the tubes are usually made as thin as possible with regard to structural stability. This makes it difficult to removably secure the tubes to each other in a stable manner since the material is too thin to provide a threaded portion of an appropriate length for engaging a screw. The material is also too thin to receive the head of a countersunk head screw.

In addition, the local application of heat during welding can weaken the overall strength of the otherwise suitable materials such that materials for welded frames are undesirably limited, for instance, to specific steels. Furthermore, welding damages a protective anodization.

On the other hand, electric bicycles are known. Electric bicycles usually have a power output of much less than 1 kW, for instance, 250 W, whereas electric motorcycles have a power output of at least 3 kW, usually more than 5 kW, for instance 6 kW. Therefore, electric bicycles require much smaller and lighter battery and motor units than electric motorcycles. Consequently, forces exercised by the masses of these units, for instance, when accelerating, steering, driving on a bumpy road, or jumping, are much smaller and the requirements on the strength of the frame thus much lower than for an electric motorcycle. Hence, electric bicycles can be made relatively light, typically below 25 kg, for instance 13 kg, by having a frame with only a central tubular column. Moreover, an electric bicycle normally has treading pedals as a main power source for driving and the electric motor is only auxiliary. Thus, to allow ergonomic treading, the electric bicycle has to be very thin, especially at the portion where the driver's knees are placed, compared to an electric motorcycle having only an electric motor as a power source.

A frame with only a central tubular column is, however, not suitable for an electric motorcycle with much heavier and larger battery and motor unit. Conventional electric motorcycles therefore have welded-together left and right tubular columns fanning out from a steering head in a rearward direction. This is more stable and provides sufficient space for the motor and battery unit, but increases the weight of the frame as compared to a single central column and also makes the conventional electric motorcycle relatively broad in width. In particular, the diameter of cavities of the tubes also adds to the width of the frame, which typically results in a frame width of more than 30 cm. A broad motorcycle is inconvenient for a person to push and is less ergonomic for requiring a broad knee placement during driving.

In sum, it is desirable, to provide a main body frame for an electric motorcycle that is light in weight and narrow in width while, at the same time, providing enough space for a motor and battery unit and sufficient strength. Moreover, it is desirable to be able to replace parts thereof. And for a corresponding electric motorcycle, it is desirable to have an ergonomic handling as well as a modular design adaptable to different driving situations, such as streets or cross-country, while retaining most parts of the frame with interest to costs.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, a main body frame according to claims1to14is provided.

According to another aspect of the present invention, an electric motorcycle is provided.

The present invention provides improvements to the above described disadvantages of the known art. The main body frame according to the present invention is particularly light in weight and/or narrow in width such that handling of an electric motorcycle with this main body frame is improved. Moreover, the main body frame can be produced without welding, for example by using screws, and preferably allows the motorcycle to be provided with a modular design.

Further features of the present invention will become apparent from the following description of the exemplary embodiments with reference to the attached drawings.

