“TRANSMISSION GROUP FOR MOTOR VEHICLES COMPRISING A REVERSE GEAR

AND RELATED MOTOR VEHICLE”

FIELD OF APPLICATION

[001] The present invention relates to a transmission group for motor vehicles comprising a reverse gear, and a related motor vehicle.

BACKGROUND ART

[002] As is known, motor vehicles, with particular reference to motorcycles, normally are not provided with reverse gear.

[003] The result is that they are rather difficult to maneuver in reverse gear because they are heavy and difficult to be moved, especially if the driver is straddling the saddle.

[004] It is also inconvenient to dismount from the saddle to manually push the motor vehicle; moreover, this operation is complicated if there is a passenger on the motor vehicle as well.

[005] The operation of manually pushing is almost impossible if the motor vehicle is not on a perfectly smooth or flat ground.

[006] In order to obviate these drawbacks, certain motorcycles, especially heavy ones, are provided with reverse gear due to a gear change solution which is very similar to those in use in the automotive field. Such solutions however are expensive and necessarily require the use of a gear transmission. Therefore, they are not applicable to motorcycles which use a variator transmission. Known solution are disclosed by FR3024971A1 and US5193634. OVERVIEW OF THE INVENTION

[007] The need is therefore felt to solve the drawbacks and limitations mentioned in reference to the prior art.

[008] Such a need is met by a transmission group for motor vehicles according to claim 1 , and by a motor vehicle according to claim 16.

DESCRIPTION OF THE DRAWINGS

[009] Further features and advantages of the present invention will become more comprehensible from the following description of preferred and non-limiting embodiments thereof, in which:

[0010] figure 1 depicts a front view of a transmission group according to an embodiment of the present invention;

[0011] figure 2 depicts a front view, on the inner side, of the closing carter of the transmission group in figure 1 ;

[0012] figure 3 depicts a partially exploded perspective view of the carter in figure 2; [0013] figure 4 depicts a perspective view of a control bushing of the transmission group according to the present invention;

[0014] figure 5 depicts a further perspective view of the control bushing in figure 4, from a different angle;

[0015] figure 6 depicts a perspective view of a driven transmission bushing completed with a transmission group according to an embodiment of the present invention;

[0016] figure 7 depicts a perspective view of the driven transmission bushing in figure 6, from a different angle;

[0017] figures 8 and 9 depict views of the control and driven bushings, respectively, in engaged and disengaged configuration;

[0018] figure 10 depicts a perspective view of the control and driven bushings in axial position of transmission and reverse gear actuated;

[0019] figure 11 depicts a perspective view of the control and driven bushings in axial position of motion transmission and reverse gear not actuated;

[0020] figure 12 depicts a perspective view of the control and driven bushings in axial position of motion transmission and reverse gear actuated;

[0021] figure 13 depicts a perspective view of the control and driven bushings in axial safety position to prevent the actuation of reverse gear.

[0022] The elements or parts of elements common to the embodiments described below will be indicated using the same numerals.

DETAILED DESCRIPTION

[0023] With reference to the aforesaid drawings, an overall diagrammatic view of a transmission group for motor vehicles according to the present invention is indicated as a whole by numeral 4.

[0024] For the purposes of the present invention, it is worth noting that the term motorcycle means any motor vehicle having at least two wheels, i.e. a front wheel and a rear wheel. Therefore, three-wheel motorcycles also fall under such a definition, such as for example two paired and steered wheels on the front axle, and one driving wheel on the rear axle, but also motorcycles comprising one steered wheel on the front axle and two driving wheels on the rear axle. Finally, the so-called motor vehicle having two wheels at the front axle and two wheels at the rear axle also fall under the definition of motorcycle.

[0025] The transmission group 4 for motor vehicles comprises a drive wheel axle 8 operatively connected to a main transmission (not shown), and operationally connectable, via the main transmission, to an internal combustion engine for forward travel of the motor vehicle.

[0026] For example, the main transmission may be a transmission of belt or chain type, and even of gear cascade type and the like. [0027] Preferably, the main transmission is of the continuously variable transmission ratio type, also referred to as CVT or variator type.

[0028] The transmission group 4 comprises an auxiliary electric motor 12 for reversing the motor vehicle. For the purposes of the present invention, the type of electric motor used is not identified; obviously, the power of the electric motor is to be congruent with the mass and type of vehicle on which it is mounted.

[0029] The auxiliary electric motor 12 is preferably arranged on the opposite side of the main transmission, with respect to the drive wheel axle 8.

[0030] The auxiliary electric motor 12 in turn may be coaxial with the drive wheel axle 8.

[0031] The auxiliary electric motor 12 and the auxiliary transmission 24 are preferably supported by a closing carter 26 of the transmission group (4), which can be applied to a main body (27) of the transmission group (4) containing the main transmission.

[0032] The transmission group 4 further comprises a control bushing 16 and a transmission driven bushing 20.

[0033] The control bushing 16 is driven in rotation by said auxiliary electric motor 12; the kinematic connection may be direct, or preferably an auxiliary transmission 24 may be provided, comprising gear, chain and/or belt return means.

[0034] The transmission driven bushing 20, in turn, is operatively connected to the drive wheel axle 8 of the motor vehicle.

[0035] The control bushing 16 is configured to centrifugally engage the transmission driven bushing 20 when the auxiliary motor 12 is on and drives in rotation the control bushing 16.

[0036] Thereby, the centrifugal engagement between the two bushings 16, 20 occurs only after the auxiliary electric motor is actuated.

[0037] The mutual arrangement between the two bushings 16, 20 may be variable; preferably, for the purposes of the overall containment of the volumes, the control bushing 16 and the transmission driven bushing 20 are coaxial with the drive wheel axle 8 and rotatable with the latter around an axis of rotation X-X during reversing.

[0038] In detail, the control bushing 16 supports centrifugal clutch masses 28 comprising engaging driving teeth 32 configured to engage, in a radially extracted condition, corresponding abutments 36 of the transmission driven bushing 20 so as to rotate the control bushing 16 and the transmission driven bushing 20 together.

[0039] The centrifugal clutch masses 28 are preferably hinged on rotation pivots 40 angularly evenly spaced with respect to the axis of rotation X-X.

[0040] For example, three centrifugal clutch masses 28 with related rotation pivots 40 angularly spaced by 120° may be used.

[0041] According to an embodiment, said rotation pivots 40 are arranged parallel to the axis of rotation X-X. [0042] According to a further possible embodiment, the centrifugal clutch masses are guided by radial guides (not shown) which guide the extracting movement thereof to engage the corresponding abutments 36 of the transmission driven bushing 20 under the action of the centrifugal force.

[0043] Regardless of the type of guide provided, the centrifugal clutch masses 28 are preferably provided with return springs 44 which are sized to recall the driving teeth 32 in a retracted position to disengage the abutments 36 when the auxiliary electric motor 12 is deactivated and no longer drives the control bushing 16 in rotation.

[0044] According to an embodiment, the control bushing 16 is provided with a synchronization plate 48 which supports and connects the centrifugal clutch masses 28 together, thus synchronizing the radial position thereof with respect to the axis of rotation X- X.

[0045] For example, the synchronization plate 48 is provided with slots 52; each slot 52 in turn slidably engages a guide pin 56 which is integral with each centrifugal clutch mass 28.

[0046] The radial extraction movement of the centrifugal clutch masses 28 can be synchronized due to the synchronization plate so that the engagement with each corresponding abutment 36 occurs simultaneously: thereby, the engagement uniformity is ensured and overloading the individual pairs of driving teeth 32 and abutments 36 is avoided.

[0047] The use of centrifugal clutch masses 28 is per se a first form of safety against the accidental actuation of the reverse gear given that, if the control bushing 16 does not reach given rotation conditions, the engagement with the transmission driven bushing 20 cannot take place.

[0048] According to a possible embodiment, the transmission group 4 is provided with a centrifugal safety system 60 associated with the transmission driven bushing 20 which prevents the reverse gear from being actuated during forward travel.

[0049] In particular, the centrifugal safety system 60 comprises a plurality of safety centrifugal masses 64, rotatably connected to the transmission driven bushing 20 and configured to axially move the abutments 36 of the transmission driven bushing 20 so as to prevent the engagement of the driving teeth 32 when the axle of the transmission driven bushing 20 rotates over a second rotation speed threshold.

[0050] According to a possible embodiment, the safety centrifugal masses 64 are hinged with respect to safety pivots 68 arranged in tangential direction, on a plane perpendicular to the axis of rotation X-X.

[0051] The safety centrifugal masses 64 comprise a front nose 72 coupled to a front abutment 76 of the transmission driven bushing 20 so as to axially move the transmission driven bushing 20, thus rotating around the safety pivots 68. [0052] In order to allow this axial movement, according to a possible embodiment, the transmission driven bushing 20 is mounted to an axial groove 84 which is coaxial with the axis of rotation X-X and is rotationally integral with the drive wheel axle 8.

[0053] The centrifugal safety system 60 preferably comprises an axial return spring 80 which influences the transmission driven bushing 20 in axial engagement position with the control bushing 16: thereby, in forward travel condition, by acting on the safety centrifugal masses 64, the centrifugal force overcomes the bias of the axial return spring 80 and disengages the control bushing 16 from the transmission driven bushing 20, thus preventing any mechanical actuation of reverse gear.

[0054] When the centrifugal force is reduced, for example because the vehicle is substantially stationary, the engagement between the control bushing 16 and the transmission driven bushing 20 is obtained due to the axial return spring 80, whereby the reverse gear of the vehicle may be actuated by virtue of to the auxiliary electric motor 12.

[0055] The operation of the transmission group according to the present invention is now described.

[0056] As described, the motion transmission system between the control bushing 16 and the transmission driven bushing 20 occurs by centrifugal actuation due to the radial opening of the centrifugal clutch masses 28 which makes the two bushings 16, 20 integral via the ensured contact by the driving teeth 32 of the control bushing 16 and the respective abutments 36 of the transmission driven bushing 20. Said centrifugal actuation occurs by the inertial impulse generated by the actuation of the auxiliary motor 12. Therefore, the centrifugal clutch masses 28 remain in expanded position due to the friction force between the contact surfaces of the clutch masses 28 and of the abutments 36 until the thrust of the auxiliary motor 12 ends and the speed of the control bushing 16 is greater than 160 rpm.

[0057] The disengagement between the control bushing 16 and the transmission driven bushing 20, and therefore of the respective driving teeth 32 and abutments 36, occurs as the action of the auxiliary electric motor 12 ceases due to the contribution of the return springs 44.

[0058] Both the engagement and the disengagement system ensured by the opening/closing of the centrifugal clutch masses 28 occurs simultaneously and synchronously due to the intervention of the synchronization plate 48 which, via the guide pin 56 and slot 52, connect the centrifugal clutch masses themselves.

[0059] An ON/OFF control of the auxiliary electric motor may be obtained with a single rotation direction due to the above-mentioned feature of the engagement/disengagement system between the two bushings 16, 20.

[0060] The centrifugal safety system 60 which does not allow the actuation of reverse gear during normal travel of the vehicle is on the transmission driven bushing 20, and namely when the drive wheel axle 8, which is rotated by the thermal engine, exceeds a given revolution speed.

[0061] As the revolutions of the shaft of the drive wheel axle 8 increase beyond a predetermined value, the safety centrifugal masses 64, which cause the axial position of the transmission driven bushing 20, open, thus causing the bushing itself to axially slide on the axial grooved profile 84, thus bringing it to a disengaged position. When the revolutions of the shaft of the drive wheel axle 8 return below a given predetermined speed, the safety centrifugal masses 64 close due to the action of the axial return spring 80, which returns the transmission driven bushing 20 to the motion transmission position. Said predetermined value or speed preferably is about 350 revolutions per minute.

[0062] As may be appreciated from the above description, the present invention allows the drawbacks introduced in the known art to be overcome.

[0063] In particular, the invention allows the motor vehicle to be moved in reverse gear, while conveniently remaining in the saddle, in a quick and effective manner. The actuation of the reverse gear does not require the use of pedals or levers, like in solutions of gears of known type, hence the user may actuate the reverse gear with the possibility of taking advantage of resting both feet on the ground.

[0064] The transmission group has significantly reduced volumes and may easily be accommodated in the transmission carter without resulting in any modification on the side of the drive shaft.

[0065] Moreover, the transmission group may be applied as add-on or retro-fit device to a pre-existing transmission by simply modifying the closing carter of the group and obviously adding the related electrical connections, electronic controls and the related operating controls to the handle.

[0066] The device is provided with a plurality of safety devices which mechanically and/or electronically avoid the possibility of inadvertently engaging reverse gear in forward travel conditions of the motor vehicle.

[0067] The transmission system of the present invention is simple given that the actuation of reverse gear occurs with an electric device only having ON/OFF control due to a mechanical engagement/disengagement of centrifugal type.

[0068] Advantageously, the actuation system develops on the outer part, on the transmission side, so as to keep the general layout of the engine of the motor vehicle intact.

[0069] Those skilled in the art, aiming at meeting contingent and specific needs, can make several changes and variations to the transmission groups and to the motor vehicles described above, all contained within the scope of the invention, which is defined by the following claims.