Background of the Invention Widely manufactured and used motorcycles have the following construction and functioning. The drive means is comprised in a main frame which also holds the front wheel assembly typically as a telescopic front fork (or swing arm), the rear wheel as- sembly typically with a swing arm construction, the riding seat, the fuel tank and other auxiliary assemblies. The rear wheel is typically the driven wlieel and the front wheel is the steered wheel. The drive means, typically an Otto-motor is in driving connec- tion with the rear wheel through a mechanical clutch, a mechanical gear (transmission) an endless chain or a toothed belt or a cardan shaft. While cornering with the motorcycle the necessary centripetal force for keeping the motorcycle on the curve is provided by banking the motorcycle towards the centre of the curve. The cross section of the tires on the wheels is normally rounded similar to a half-circle maintaining substantially the same contact area with the ground even during cornering when the motorcycle is tilted. As a result of this known tire construction the contact area of the tire which is necessary to transmit forces is very little, not more than a few cm.

The conventional motorcycles are due to the above construction features very instable vehicles. They belong to the most dangerous transport means and a relatively safe driving requires much practice and a high level driving knowledge.

Many attempts have been made in order to overcome the above drawbacks, a large

number of patents discloses improved or basically new motorcycle constructions.

Such motorcycles are for example described in the patent specifications US 5,060,749 and in US 4,984,650.

These documents describe motorcycles with a main frame connected to the rear wheel assembly and including a drive means. The tire on the rear wheel is flat and wide and thus it prevents the banking of the main frame and maintains an upright position of the rear wheel with the flat and wide tire and the main frame with the drive means during cornering and so provides a larger contact area between the rear wheel and the ground and a higher level of stability. In these constructions the main frame is connected with a subframe through a rotating shaft. The subframe is connected to the front wheel as- sembly, the driving seat, the fuel tank and other auxiliary assemblies. The connecting shaft has a nearly horizontal position along the longitudinal axis of the vehicle. In a cornering situation the subframe and all connected parts incline for providing the nec- essary centripetal force while the main frame and the connected parts remain in a ver- tical position.

These constructions have the following drawbacks and deficiencies: -only the rear wheel provides for a higher stability than usual, the front wheel has a narrow round profile and inclines during cornering.

-the drive means (motor, transmission, etc) are connected to the main-during cor- nering not banking-frame. As a result, a heavy part of the vehicle (with a relatively high centre of mass) is not banking while cornering, so the banking part will have to be inclined much more in order to compensate the inertness of the not banking part.

Such constructions may therefore not provide substantially improved cornering facili- ties compared with conventional motorcycles.

-the connecting shaft between the main frame and the subframe enables an inclination or banking of the subframe while cornering which is different from conventional mororcycles, because the connecting shaft is necessarily not in the ground plane but it is positioned higher which results in an angular force acting on the wheels laterally which reduces the driving stability of the vehicle.

US 5,107,950 discloses an improvement of the above discussed motorcycle construc- tions by describing a vertically cornering front wheel. The above discussed two other

drawbacks are not solved by this construction either. A further disadvantage is that the cornering parameters of the motorcycle and thus the stability of the vehicle are con- trolled and set by an electronic unit. This electronic unit (special computer) calculates the controlled cornering parameters (e. g. wheel cornering angle) on the basis of meas- ured values (speed, tilting angle, steering arm position, etc) and sets the controlled values automatically (with the help of servo motors). As a result the spontaneous be- haviour of the vehicle and the control of the driver are decreased or eliminated. The electronic unit can not be prepared for every case encountering in practice and there- fore such a vehicle can not provide the required security despite of its difficulty.

The object of the present invention is to overcome the disadvantages and drawbacks of the known constructions and to provide a new motorcycle construction which makes it possible to use tires with significantly larger ground contact area on both wheels, thereby improving as well the accelerating and deceleration characteristic as the cornering characteristic and also the general stability of the vehicle in each work- ing condition is improved.

Disclosure of the Invention In order to achieve this object the present invention provides a motorcycle where the banking frame is connected to the base frame by means of arcuate guide rails along a circle arc with a central point laying on or below the section line defined by the central longitudinal plane of the wheels and the ground.

Such a construction has the advantage of maintaining the unchanged upright angular position relative to the ground of both (front and rear) wheels while cornering or while driving on an inclined ground. This enables the use of tires with large contact area on each wheel, which provides not only higher acceleration (deceleration) or cornering speed values but also improves the overall traffic safety of the motorcycles as one of the most dangerous vehicles. Compared to the prior art constructions the driving sta- bility is increased also by the fact that rotation axis of the banking frame is not above the ground level but in the ground plane-like it is the case with conventional motor- cycles-or slightly below the ground plane.

According to one aspect of the invention the guide rails are attached to base frame and the banking frame is connected to the guide rails with rollers attached to the banking frame. It may be apparent to those skilled in the art that the location of the guiding rails and of the rollers may be changed in order to achieve the object of the invention.

Such a construction requires only a little number of moving parts which reduces the failures and increases the lifetime of the construction.

According to another aspect of the invention the base frame is provided with a front and a rear pair of guide rails, where the upper guide rails are connected to two rollers and the lower guide rails are connected to three rollers. In an equivalent embodiment the base frame is provided with a front guide rail and a rear guide rail with three roll- ers connected to the upper part of the guide rails and two rollers connected to the lower part of the guide rails.

In a preferred embodiment most of the mass determining parts are positioned on the banking frame. In such embodiments the motor and a part of the transmission chain are positioned on the banking frame.

In a further preferred embodiment the banking frame comprises a hydraulic pump which is connected to the motor and which is part of the transmission chain, and the base frame comprises a hydromotor which is connected to the hydraulic pump and a driving chain-gear which is driven from the axle of the hydromotor is connected to a driven chain-gear positioned on the at least one driven wheel.

These constructions are advantageous because the banking of the motorcycle during cornering or on an inclined ground offsets the mass centre of the vehicle in such a way that the resulting force line crosses all the time the contact area between the wheels and the ground and therefore no additional moment of rotation is generated which would decrease the driving stability.

The driving stability can be further improved by applying a gyroscope (14) which may be positioned on the banking frame.

Brief description of the drawings The invention and further preferred embodiments will be described more detailed with reference to the accompanying drawing where Fig. 1 is a top view and a side view of a motorcycle construction according to the invention, Fig. 2 is a schematic drawing of one embodiment of the guiding rail used in the in- vention, Fig. 3 is a schematic drawing of another embodiment of the guiding rail used in the invention, Fig. 4 is a schematic drawing for showing the connection between the guiding rails positioned on the base frame and the rollers positioned on the banking frame, Fig. 5 is a back view of the motorcycle construction according to the invention dur- ing cornering, Fig. 6 is a schematic drawing showing another possible driving arrangement of the motorcycle construction according to the invention and Fig. 7 is a schematic drawing showing a possible steering assembly of the motorcycle construction according to the invention.

Description of the preferred embodiments A one track example of the motorcycle construction according to the invention can be seen in Fig. 1. The steered front wheel 3 and the driven rear wheel 6 are connected to a main or base frame 1 through a front wheel assembly or support 4 and a rear wheel assembly or support. The kind of the wheel support depends on the actual implemen- tation. Without going into further details, a suitable support for the invention is for example a swing arm support. The disc wheels are wide and can hold tires with a rec- tangular profile Lj and thus they have a large contact area with the ground. As shown in Fig. 1 the front wheel 3 is undevided and the rear wheel 6 is devided but the inven- tion is not limited to such a wheel arrangement. As it may be apparent to those skilled in the art, the motorcycle structure according to the invention may also comprise a divided front wheel and an undivided rear wheel, two undivided wheels, two divided wheels or even two independent front and two independent rear wheels. On the base

frame 1 there is also a chain-gear 12 for driving directly the wheels 6 and a hydromo- tor 11 for driving the chain-gear 12. The chain-gear 12 associated with the base frame 1 and the chain-gear 13 associated with the driven wheel 6 are connected with each other through a driving chain (not shown). The base frame 1 is connected to banking frame 2 which is holding the parts defining a substantial part of the vehicle mass. Ac- cording to this, the banking frame 2 comprises a motor 16 and a hydraulic pump 10 forming part of the driving chain, a driver's (and passanger's) seat, a steering means 7, a fuel tank, and other auxiliary parts. The hydraulic pump 10 positioned on banking frame 2 and the hydromotor 11 positioned on the base frame 1 are connected with each other by flexible pipes (not shown). The footsteps (not shown) are typically ar- ranged on the banking frame 2 but it is also possible to arrange the footsteps on the base frame 1. In order to further improve the driving stability, a gyroscope may also be arranged on the banking frame 2.

A rotating and rigid connection between the base frame 1 and the banking frame 2 can be achieved by guiding rails 8 associated with the base frame 1 and rollers 9 attached rotatably to the banking frame 2. The position of the guide rails 8 and the rollers 9 can be reversed.

Fig. 2 shows an embodiment, where a pair of circularly curved front and rear guide rails 8 are attached to the base frame 1. These are the front upper guide rail 8ef, the front lower guide rail 8ea, the rear upper guide rail 8hf and the rear lower guide rail 8ha. The pairs of front and rear guide rails 8 are formed equally. The central point of the upper and lower arcuated guide rails is a common circle arc centre point. These common centre points are on or below the intersection line, on the axis Tfv in the drawing, defined by the central longitudinal plane of the wheels and the ground plane.

In this embodiment the upper guide rails 8ef, 8hf are associated with two rollers 9 and the lower guide rails 8ea, 8ha are associated with three rollers 9. The guiding surface of the guide rails 8 is V-shaped or similarly formed and the rollers of a predetermined geometry fit exactly into the guiding surface which ensures that the banking frame 2 guided by the two pairs of guide rails 8 relative to the base frame 1 can not move other than only around the axis Tfv. The construction according to the invention and shown in the drawing enables a banking of up to approximately 45 degree. In this embodi- ment the main load-bearing member is the lower guide rail, and the upper guide rail is

responsible for the exact position of the banking frame 2 (and for protecting the banking frame from tilting from the lower rail). In this construction the appropriate bearing of the rollers and the fine finishing of the guiding surfaces results in a nearly forceless free movment of the banking frame on the desired curve. Limiting stops (not shown) provide for keeping the banking frame 2 within a security angular range. A further advantage of this construction is that it can withstand bending moments re- sulting from higher load by providing an appropriate rigidity of the two part frame structure. In this construction the base frame 1 and the banking frame 2 are connected to each other vertically at two positions preventing the vertical parts of the base frame 1 from being bent in a front or back direction and also preventing the base frame from being bent along its longitudinal axis due to the load of the vehicle. As a result the longitudinal part of the base frame may be weaker and lighter.

Fig. 3 shows an alternative embodiment with a base frame 1 comprising only one front and one rear guide rail 8. In this embodiment the guide rails 8 are supported by three upper rollers 9 and two lower rollers 9. The rotation angle (e. g. 45 degrees in both directions) of the banking frame 2 is limited by end stops (not shown). The rota- tion angle and the length of the guiding rails is selected so that the guiding rails are supported at least by three rollers at a time. The advantage of this embodiment is the simpler construction.

Fig. 4 as an enlarged side view of Fig. 2 shows the connection of the base frame 1 and the banking frame 2 through rollers 9 and a pair of guide rails 8.

Besides this connection through guiding rails other mechanical or hydraulic guiding connections can be used for connecting the two frame parts.

The functioning of the motorcycle structure of the present invention will be described in connection with a cornering example referring to the transmission (Fig. 5). During cornering the base frame stays in an upright (perpendicular to the ground) and the tires keep full contact with the ground (are not inclined). The banking frame 2 is rotatably connected to the base frame so that it can be tilted (together with all connected parts) by the driver towards the centre of the curve in order to keep the vehicle in the curve.

The banking frame 2 rotates around an imaginary axis Tfv (Fig. 1) which in this ex-

ample is an axis on the ground in the central longitudinal plane of the vehicle (section line defined by the central longitudinal plane of the motorcycle and the ground plane).

As a result the banking frame 2 can be tilted in the same way as the conventional mo- torcycles can be tilted. According to this the resulting force generated by the banking frame upon cornering acts on the ground in the symmetry plane of the base frame. In alternative embodiments it is also possible to provide a banking frame generating a resulting force which acts not exactly in the symmetry plane of the base frame but with a little offset to one side where the acting point is always within the contact area between the tires and the ground.

The motorcycle construction according to the invention and described above provides for an increased cornering stability on the basis of the following.

The stability of the banking frame is achieved by the banking upon cornering towards the curve centre. If the practical implementation requires, the stability of the banking frame may be further increased by provided it with a rotating mass positioned in a suitably selected plane, which can be for example a gyroscope 14. Such a gyroscope 14 substitutes the stabilising effect of the rotating wheels (gyroscope effect) of a con- ventional motorcycle. This gyroscope may be driven (e. g. by an electric motor) inde- pendently from the motorcycle drive and therefore the stabilising effect of this gyro- scope is also speed independent and scaleable (it is capable of holding the banking frame in an upright position even if it has already stopped).

The stability of the base frame is achieved by the following features. During cornering the resulting force of the banking part acts on the ground along the axis Tfv and the contact area of the wide and flat tires remains unchanged thereby preventing the base frame from tilting. The gravity keeps the base frame in an upright position. It is also possible that by lowering the gravity centre of the base frame the maximum of the centripetal acceleration is increased without any stabilising effect of the resulting force of the banking frame in order not to tilt upon cornering. Nevertheless, it is of less practical importance because of the resulting force being much higher than the gravity force of the base frame.

During travelling the rotating wheels acting like a gyroscope stabilise the base frame.

This gyroscopic effect of the motorcycle according to the invention may be much more significant than the gyroscopic effect of a conventional motorcycle caused by the wheels because the wheels according to the invention have the same radius but are significantly wider thus having a greater mass and angular momentum According the these particulars the stability of the motorcycle construction according to the invention may be much higher compared to conventional motorcycles when cornering or travelling straight forward.

The driving system of the motorcycle construction according to the invention has to fulfil the following criteria.

-it has to carry our all movement actions (acceleration, high speed driving, decelera- tion, kinematic and torque changes, etc.) of the motorcycle construction according to the invention, -it has to accomplish the transmission of the driving between the banking and the base frame, <BR> <BR> <BR> <BR> -it should not decrease the stability of the motorcycle construction according to the invention (it should not exert any rotating moment to the banking or the base frame along the longitudinal axis).

A driving system meeting the above criteria can be implemented in different ways.

The following example is a hydraulic implementation but it is also possible to use other, e. g. mechanical or electrical constructions.

According to an aspect of the inventions it is possible to connect one (or more little) hydraulic pump (s) 10 to the driving axle of the motor 16 (through a fix transmission, or other arrangements like a switching means, a differential gear or in the most simple case directly). The pressure generated by the hydraulic pump 10 may be conducted by flexible hydraulic pipes (not shown) to the base frame 1. On the base frame 1 there is one or more (in the shown embodiment two) hydromotors 11 which converts the high pressure hydraulic stream into rotational movement in order to enable for the wheel 6 to be driven by a simple chain transmission. In the shown embodiment according to Fig. 1 the driven wheel 6 is represented by a divided wheel consisting of two parts

having a common axis of rotation with a chain gear 13 being positioned in the middle between the divided wheel parts.

The commercially available hydraulic pumps and hydromotors can be dimensioned and selected in order to be used for the invention. A suitable design makes it possible to transmit extreme high power, to use low mass low volume hydraulic parts and more hydraulic pumps and more hydromotors, controllable stream hydraulic pumps and hydromotors, to accomplish automatic or driver-contolled torque-and angular speed transmittion, multistage or continuous automatic torque change, or to provide a simple reverse stage (the stability of the motorcycle allows the reverse stage).

The driving motor, the hydraulic pump, the hydromotor may have alternative posi- tions depending on the actual design. The hydromotor may be positioned for example in the tire volume of the driven wheel thus providing a vehicle with all-wheel drive.

The other hydraulic components (cooler, control, etc) may be located on the banking frame or on the base frame (not shown) in accordance with the special design.

Fig. 6 representatively shows an embodiment of a mechanical transmission located partly on the banking frame 2 and the base frame 1 according to the above criteria.

The motor 16 is provided with a mechanical torque converter or clutch 20 which is connected to a special gear box 19 for transmitting the rotation of the output axle of the clutch 20 to two counterrotating cardan shafts 18 arranged with substantially par- allell longitudinal axis. The other end of the cardan shafts 18 is connected to a trans- mission located on the base frame 1. The transmission 17 transmits the torque of the cardan shafts 18 through chain-gears 21,12 and through an endless chain (not shown) to the driven wheel 6. The transmission 17 located on the base frame 1 is also pro- vided with a differential gear for compensating the angular error of the cardan shafts 18 during cornering due to the inclination angle of the banking frame, which is a dif- ferential gear commonly used in cars or other suitable mechanism. This differential gear may also be built in the gear box 19 located on the banking frame 2.

The following is a detailed description of the function of the above motorcycle con- struction with regard to the cornering primarily. The driving moment of the motor is transmitted by the above mechanism to the driven wheel 6. The driving torque is

transmitted between the banking frame 2 and the base frame 1 by the two counterro- tating cardan shafts divided equally therefore no reaction torque is transmitted to the base frame 1 or the banking frame 2. The cardan shafts 18 are configured to be com- pressed or elongated during cornering and tilting the banking frame towards the centre of the curve in order to compensate the change of the distance of the gear box 19 lo- cated on the banking frame 2 and the transmission 17 located on the base frame. Due to the inclination of the banking frame 2 a positive angular error is caused in one of the cardan shafts 18 relative to its direction of rotation and a negative angular error is caused in the other cardan shaft 18 relative to its direction of rotation. This angular error may be compensated by the transmission 17 located on the base frame 1 with a built in differential gear. Such an arrangement meets all requirements stated above in connection with the motorcycle structure according to the invention.

On the banking frame 2 a conventional steering means 7 is supported by bearings axi- ally. The steering means 7 rotatable by the driver is connected through steel wires or hydraulic transmission to the steered wheel 3 in order to rotate it. The steered wheel 3 may be supported similarly to the wheel support in cars using an axle pinl5. Adjusting a suitable wheel camber angle allows a perfect straightforward running. The vertical axis of the axle pin 15 is positioned in the longitudinal symmetry plane of the steered wheel. The suitable rotation angle has to be set by the driver during cornering. It is an advantageous feature of the conventional motorcycles (due to the wheel camber angle and the wheel angular momentum) that the motorcycle can be directed whithout any rotation of the steering handlebar only through inclining the motorcycle frame, the appropriate wheel angle will be set automatically. Although this"free-hand motorcy- cling"is not enough for a safe driving, it may help the driver to keep the direction while cornering. In a practical implementation it may be necessary to provide the motorcycle according to the invention with a passive or active steering-control or sup- port system.

A possible embodiment of such a steering-control or support system is shown in Fig.

7. The steered wheel 3 is supported by a vertical axle pin 15, which is connected to directing arms 23 and 24 for rotating the wheel. The directing arms 23 and 24 are connected with a pair of steel wires 25 or with other flexible force transmitting system like a hydraulic transmission which connect the directing arms 23 and 24 located on

the steered wheel with directing arms 27 and 28 located on the banking frame 2 the latter being connected to an output axle of a mechanical transmission 29 driven by an electric servomotor 30. The connection is configured so that a rotation of the directing arms 27 and 28 causes a rotation of the directing arms 23 and 24 in the same sense or direction. In order to achieve such a functioning the directing arms of the same side 23,28 and 24,27 are connected with each other through a steel wire respectively. The directing arms 27 and 27 located on the banking frame 2 are connected with the steering hadlebar 37 controlled by the driver through a slightly flexible connection 36.

The electric servomotor 30 is controlled by a control electronic 33 which is connected with an inclination sensor 31, a speed sensor 32, a directing arm position sensor 34, a differential sensor 35 for sensing the angular difference between the position of the steering handlebar 37 and of the directing arms 27,28. The associated pairs of direct- ing arms are preferably made as a one piece directing arm therefore maintaining a constant angle between the arms.

The functioning of this active steering control and support system is the following.

During travelling the inclination sensor 31 provides signal proportional with the incli- nation angle (divergence from the vertical) of the banking frame, the speed sensor 32 provides a signal responsive to (proportional with) the actual speed of the vehicle, the directing arm position sensor 34 provides signals responsive to the position of the directing arms 27,28 and of the steered wheel 3, the differential sensor 35 provides signals responsive to (proportional with) the small angular difference between the steering handlebar 37 and the directing arms 27,28. From the signals of the speed sensor 32 and the inclination sensor 31 the control electronic 33 calculates a cornering curve and an associated rotation angle of the steered wheel 3 corresponding to the given speed and inclination. This calculated value is compared by the control elec- tronic 33 with the actual value provided by the directing arm position sensor 34. If the rotation angle of the steered wheel 3 is not identical with the calculated value, the control electronic 33 causes the servomotor 30 to rotate in order to decrease the dif- ference as long as the rotation angle of the steered wheel 3 is not identical with the calculated value. While cornering the driver will tilt the banking frame by a desired angle which causes the front wheel 3 to turn at a specific angle according to the banking angle automatically which results in an automatic directing of the vehicle. As a result of this active directing the banking frame is-disregarding the secondary ef-

fects such as a sidewind-always in a balanced condition, e. g. a lateral inclination is prevented. If the driver intends to apart from the automatically selected wheel angle due to any circumstances, it is possible for him to exert a rotating force onto the steering handlebar 37 which has a flexible connection 36 connection to the directing arms 27,28 which will result in a rotation of the directing arms 27,28 which is de- tected by the associated sensor 35 and a signal responsive to this rotation will be led to the control electronic 33 which will in turn actuate the servomotor 30 and thus rotate the steered wheel at a desired angle. In case of a defect of the above described active control system a manual control can be selected by maintaining the mechanical or hydraulic connection between the steering handlebar 37 and the steered wheel 3.

In a further aspect of the invention it may be advantageous in practice to provide a brake system between the base frame 1 and the banking frame 2 which may decelerate the rolling of the rollers 9 in the guide rails (8ef, 8ea, 8hf, 8ha). This banking brake may be activated by the driver or automatically upon specific control signals main- taining thereby an upright position while parking or stopping if the traffic requires so.

Besides a general purpose use in civil transportation the motorcycle structure accord- ing to the invention may be designed or configured to be used under specific condi- tions (such as a racer). As it will be apparent for those skilled in the art, the invention as described above is not limited to the shown examples, therefore it may be used not only in connection with a one track motorcycle construction comprising two wheels but also with two ore more track vehicles comprising three four or more wheels.