Cross-Reference to Related Applications

This Patent Application claims priority from Italian Patent Application No . 102022000004520 filed on March 9 , 2022 the entire disclosure of which is incorporated herein by reference .

Technical Field

The present invention relates to a hybrid drive system for a pedal vehicle , and therefore is preferably applicable to a bicycle .

Background Art

Pedal vehicles , such as a bicycle , are used increasingly as transport system both for leisure purposes and for reasons of necessity, such as for transporting goods , above all in the city .

In order to be able to ride for increasingly long distances or up steep hills , hybrid drive systems for bicycles are known .

Examples of these hybrid drive systems are disclosed in the publications WO2020221491 Al or EP2423032 Bl , which respectively disclose the use of electric machines configured as electric motors to supply torque in pedal assist mode or generators to generate electrical energy that can be stored in energy storage means , such as electric batteries .

However, these known systems are not yet versatile in order to supply, in a wide torque range , suf ficient driving torque and, on the other hand, to optimally manage the generation of electrical energy in regenerative mode .

Therefore , there is the need to solve the technical problems with respect to the prior art systems as indicated above . The obj ect of the present invention is to satis fy the needs set forth above in an optimal and economical way .

Summary of the Invention

The aforesaid obj ect is achieved by a hybrid drive system and a bicycle as claimed in the appended claims .

Brief Description of the Drawings

For a better understanding of the present invention a preferred embodiment is described below, by way of nonlimiting example and with reference to the accompanying drawings , wherein :

• Fig . 1 is a schematic view of a hybrid drive system for bicycle according to a first embodiment of the invention;

• Fig . 2 is a schematic view of a hybrid drive system for bicycle according to a second embodiment of the invention;

• Fig . 3 is a schematic view of a hybrid drive system for bicycle according to a third embodiment of the invention;

• Figs . 4 and 5 illustrate flow diagrams illustrating respective control methods of the hybrid drive system in two di f ferent operating conditions .

Detailed Description of the Invention

The accompanying figures illustrate a hybrid drive system 1 for a bicycle (not illustrated) comprising a pedal shaft 2 rigidly connected to a pair of pedals 3 suitable to be moved by a driver of the bicycle by means of muscle force , an electric machine 4 and a transmission 5 operatively interposed between the pedal shaft 2 and the electric machine 4 . Therefore , the pedal shaft 2 extends coaxial to the pedal axis identi fied as A in the accompanying drawings .

The bicycle further comprises , as known, a rear wheel 6 , not illustrated, connected by means of the transmission 5 to the pedal shaft 2 and to the electric machine 4 and a front wheel , not illustrated, normally carried idle by a frame of the bicycle . The electric machine 4 is configured to act as electric motor , supplying torque by means of the transmission 5 to the pedal shaft 2 and to the rear wheel 6 or to act as electric generator, receiving torque by means of the transmission 5 from the rear wheel 6 .

For this purpose , the hybrid drive system 1 and/or the bicycle comprise electrical energy storage means 7 electrically connected to the electric machine 4 and configured to supply or store electrical energy . These storage means 7 can be one or more electric batteries .

The hybrid drive system 1 and/or the bicycle further comprise an electronic unit 8 electrically connected to the electric machine 4 and comprising processing means suitable to control operation of the electric machine 4 as detailed below .

In the embodiment of Fig . 1 , the transmission 5 comprises a first and a second support shaft 11 , 12 produced coaxial to the pedal shaft 2 and carried, respectively, one integral in rotation with the pedal shaft 2 , for example by means of a torsional coupling 17 , and the other rotating freely with respect to it , for example through rolling means 18 such as bearings .

The transmission 5 further comprises a third support shaft 13 of axis B, parallel to the axi s A, operatively interposed between the electric machine 4 and the first and second coaxial support shafts 11 , 12 .

The third support shaft 13 , in particular, is operatively connected to the electric machine 4 by means of a transmission module 14 . Advantageously, the transmission module 14 comprises a first gearwheel 14 ' carried integral in rotation with the further support shaft 13 and a second gearwheel 14 ' ’ integral in rotation with an operating shaft 4' of the electric machine 4.

In more detail, the second gearwheel 14' ’ has a smaller pitch diameter than the first gearwheel 14' . The first gearwheel 14' can be connected to the further support shaft 13 by means of a bidirectional selective joint 15.

In particular, the bidirectional selective joint 15 is configured to allow coupling of the first gearwheel 14' , in both directions of rotation, on the third support shaft 13 or to maintain it idle on it.

The second support shaft 12, in particular, is operatively connected to the rear wheel 6 by means of a transmission module 16. Advantageously, the transmission module 16 comprises a first gearwheel 16' carried integral in rotation with the second coaxial shaft 12 and a second gearwheel 16' ’ integral in rotation with a shaft 6' operatively connected to the rear wheel 6.

In more detail, the second gearwheel 16' ' has a smaller pitch diameter than the first gearwheel 16' . The first gearwheel 16' can be produced integral with the second support shaft 12.

The transmission 5 further comprises a plurality of gearwheels 21, 22, 23, 24 meshing between the three support shafts 11, 12 and 13 as described in greater detail below.

In particular, the first support shaft 11 comprises a plurality of gearwheels 21, for example three gearwheels 21' , 21' ' , 21' ' ' carried integral with the first support shaft 11.

The second support shaft 12 comprises a plurality of gearwheels 22, for example three gearwheels 22' , 22' ’ , 22' ' ' carried integral with the second support shaft 12 .

The third support shaft 13 comprises a first plurality of wheels 23 , for example three gearwheels 23 ' , 23 ' ' , 23 ' ' ' , configured to mesh respectively with the gearwheels 21 and a second plurality of wheels 24 , for example three gearwheels 24 ' , 24 ' ' , 24 ' ' ' , configured to mesh respectively with the gearwheels 22 .

In particular, the first plurality of wheels 23 is connected to the third support shaft 13 by means of a freewheel gear shi ft mechanism 25 configured to selectively couple one between the wheels 23 and the support shaft 13 (maintaining the remaining wheels idle ) only when the torque is supplied to the gearwheels 23 by the gearwheels 22 and to allow free rotational support of this when the torque is supplied by the gearwheels 23 to the gearwheels 22 . As various embodiments of freewheel gear shi ft mechanism are known, they will not be described in further detail .

In particular, the second plurality of wheels 24 is connected to the third support shaft 13 by means of a gear shi ft mechanism 26 configured to selectively couple one between the wheels 24 and the support shaft 13 in both directions of rotation of the shaft 13 , while the remaining wheels are idle . In particular, the wheels 24 can be coupled, when selected by the gear shi ft mechanism 26 , by means of a bidirectional j oint , not further described being per se a known mechanism .

In the embodiment of Figs . 2 and 3 , the transmission 5 comprises a first support shaft 12 ' produced coaxial with the pedal shaft 2 and carried in a rotationally free way with respect to it , for example through rolling means 18 such as bearings . The transmission 5 further comprises a second and a third support shaft 11' , 13' of respective axes B and C, parallel to the axis A, operatively interposed between the electric machine 4 and the first support shaft 12' .

The third support shaft 13' , in particular, is operatively connected to the electric machine 4 by means of a transmission module 14. Advantageously, the transmission module 14 comprises a first gearwheel 14' carried integral in rotation with the further support shaft 13 and a second gearwheel 14' ’ integral in rotation with an operating shaft 4' of the electric machine 4.

In more detail, the second gearwheel 14' ' has a smaller pitch diameter than the first gearwheel 14' . The first gearwheel 14' can be connected to the further support shaft 13' by means of a bidirectional selective joint 15.

The first support shaft 12' , in particular, is operatively connected to the rear wheel 6 by means of a transmission module 16. Advantageously, the transmission module 16 comprises a first gearwheel 16' carried integral in rotation with the first support shaft 12' and a second gearwheel 16' ’ integral in rotation with a shaft 6' operatively connected to the rear wheel 6.

In more detail, the second gearwheel 16' ’ has a smaller pitch diameter than the first gearwheel 16' . The first gearwheel 16' can be produced integral with the first support shaft 12' .

The transmission 5 further comprises a plurality of gearwheels 22, 31, 32 meshing between the three support shafts 11' , 12' and 13' as described below in more detail.

In particular, the first support shaft 12' comprises a plurality of gearwheels 22, for example three gearwheels 2.2.' , 22' ' , 22' ' ' carried integral with the second support shaft 12' .

The second and the third support shaft 11' , 13' each comprise a plurality of wheels 32, 31, for example three gearwheels 32' , 31' , 32' ' , 31' ' , 32' ' ' , 31' ' ' , configured to mesh respectively with the gearwheels 22.

In particular, each wheel 32, 31 is connected to the respective shaft 11' , 13' by means of a gear shift mechanism 26 configured to selectively couple one between the wheels 32, 31 with the respective shaft 11' , 13' while the remaining wheels are idle. In particular, the gear shift mechanism 26, comprises a bidirectional joint, not further described being per se a known mechanism.

According to the embodiment of Fig. 2, the second and the third connection shaft 11' , 13' are operatively connected by means of a transmission module 30 operatively interposed between them and the pedal shaft 2.

In particular, the transmission module 30 comprises a first gearwheel 30a integral with the pedal shaft 2 and respective gearwheels 30b' each carried by the second and by the third connection shaft 11' , 13' . In particular, the gearwheel 30a has a smaller pitch diameter than the gearwheels 30b' .

In particular, the gearwheels 30b' are carried by means of a freewheel mechanism 27 configured to make the gearwheel 30b integral with the respective shaft 11' , 13' only when the torque is supplied by the gearwheel 30a integral with the pedal shaft 2 to the gearwheel 30b' and to make the gearwheel 30b' idle when the torque is supplied by the latter towards the gearwheel 30a integral with the pedal shaft 2. According to the embodiment of Fig. 3, the second and the third connection shaft 11' , 13' are operatively connected by means of respective gears 34, 35 operatively interposed between each of these and the pedal shaft 2.

In particular, each transmission module 34, 35 comprises a first gearwheel 34' , 35' integral with the pedal shaft 2 and a gearwheel 34' ' , 35' ' each carried by the second and by the third connection shaft 11’ , 13' . In particular, the first gearwheels 34' , 35' have a smaller diameter than the second gearwheels 34' ' , 35' ’ .

In particular, the gearwheels 34' ’ , 35' ’ are carried by means of a freewheel mechanism 27 configured to make the gearwheel 34' ' , 35' ’ integral with the respective shaft 11’ , 13' only when the torque is supplied by the first gearwheel 34' , 35' and to make the gearwheel 34' ' , 35' ’ idle when the torque is supplied by the latter towards the first gearwheel 34' , 35' .

The aforesaid gear shift mechanisms 25, 26 can also be electrically connected to the electronic unit 8 that controls actuator means (not illustrated) to allow coupling of a specific gearwheel operatively connected thereto. Alternatively, the gear shift mechanisms 25, 26 can be actuated manually by the user of the bicycle, for example by means of a mechanical control system.

Moreover, the bicycle comprises, not illustrated, braking control means such as levers, that can be pressed by the user and configured to regulate braking of the bicycle by means of the electric machine 4, as described below, and/or by means of mechanical braking systems, of known type, configured to impart a braking torque to the rear wheel 6. The bicycle further comprises sensor means , not illustrated, configured to :

• detect the state of charge of the storage means 7

• speed sensor means , for example encoder or Hall sensors , configured to detect the speed of the shafts 2 , 11 , 11 ' , 12 , 12 ' , 13 , 13 ' ;

• sensor means configured to detect the selection of an operating mode of the bicycle between pedal assist , regenerative braking, pedalling during charging or none of these , such as a push button, a display or a lever ;

• position sensor means configured to detect the actuation of braking control means .

The sensor means are advantageously electrically connected to the electrical unit so as to supply signals indicative of the measurements detected by them .

The bicycle can also comprise dissipator means (not illustrated) , connected to the storage means 7 , configured to dissipate the temperature of these means , preferably passively, such as fins . In this case , the sensor means further comprise temperature sensor means configured to detect the temperature of the dissipator means .

Operation of the first embodiment described is the following .

In a first operating condition, the electric machine 4 acts as electric motor supplying torque by means of the transmission module 14 to the third support shaft 13 coupled by means of the bidirectional selective j oint 15 . The electric machine 4 thus uses electrical energy from the storage means 7 . The torque from the third support shaft 13 is trans ferred by means of the gears 24 , 22 to the second support shaft 12 , which rotates freely on the pedal shaft 2 , and by means of the transmission module 16 to the rear wheel 6 . On the other side , the freewheel gear shi ft device 25 makes the gearwheels 23 idle , in this way releasing the pedal shaft 2 .

In a second operating condition, the electric machine 4 is not connected to the transmission 5 . In particular, the torque is supplied by means of muscle force to the pedals 3 , which rotate the pedal shaft 2 , which carries by means of the connection 17 the gearwheels 21 supported on the first support shaft 11 , which mesh with the gearwheels 22 , one of which is made integral by means of the freewheel gear shift device 25 . There , the torque is transmitted to the wheels 24 by means of the third support shaft 13 which, meshing with the wheels 22 , cause the rotation of the second support shaft 12 , which rotates freely on the pedal shaft 2 and, by means of the transmission module 16 , to the rear wheel 6 . In this condition, the bidirectional selective j oint 15 maintains the wheel 15 ' idle with respect to the third support shaft 13 so that the resistance torque to the shaft 4 ' of the electric machine 4 is not perceived by the user .

In a third operating condition, the electric machine 4 acts as generator . In particular, the rear wheel 6 , by means of the transmission module 16 , causes the rotation of the second support shaft 12 , which rotates freely on the pedal shaft 2 , which carries by means of the connection 17 the gearwheels 21 , which mesh with the gearwheels 22 , one of which is made integral by means of the freewheel gear shi ft device 25 . There , the torque is transmitted to the wheels 24 and from these to the third support shaft 13 , which rotates . In this condition, the bidirectional selective j oint 15 maintains the wheel 15 ' coupled to the third support shaft 13 so that the torque is supplied to the shaft of the electric machine 4 that generates the electrical energy storable in the storage means 7 . Simultaneously, the freewheel mechanism 25 does not allow the transmission of torque from the third support shaft 13 to the first support shaft 11 .

In a fourth operating condition, the electric machine 4 is connected to the transmission 5 . In particular, the torque is supplied by means of muscle force to the pedals 3 , which rotate the pedal shaft 2 , which carries by means of the connection 17 the gearwheels 21 supported on the first support shaft 11 , which mesh with the gearwheels 22 , one of which is made integral by means of the freewheel gear shift device 25 . There , the torque is transmitted to the wheels 24 by means of the third support shaft 13 which, meshing with the wheels 22 , cause the rotation of the second support shaft 12 , which rotates freely on the pedal shaft 2 and, by means of the transmission module 16 , to the rear wheel 6 . In this condition, the bidirectional selective j oint 15 maintains the wheel 15 ' integral with the third support shaft 13 so that by means of muscle force the user can overcome the resistance torque to the shaft 4 ' of the electric machine 4 to allow operation as generator and recharging of the storage means .

Operation of the embodiments of Fig . 2 is the following .

In a first operating condition, the electric machine 4 acts as electric motor supplying torque by means of the transmission module 30 to the third support shaft 13 ' coupled by means of the bidirectional selective j oint 15 . The electric machine 4 thus uses electrical energy from the storage means 7 . The torque is trans ferred from the third support shaft 13 ' by means of the gears 31 or 32 by means of meshing of the gearwheels 22 according to the gear to be selected :

• i f wishing to select a gear corresponding to a gearwheel 31 , then one of these is selected by means of the gear shi ft mechanism 26 and the gearwheels 30b' are idle , so that the torque is not transmitted to the second support shaft 11 ' ; • i f wishing to select a gear corresponding to a gearwheel 32 , then one of these is selected by means of the gear shi ft mechanism 26 and the gearwheels 30b' mesh with the third and the second support shaft 13 ' to allow the flow of torque to the second support shaft 11 ' .

The first support shaft 12 ' is thus rotated according to the coupling indicated above and rotates freely on the pedal shaft 2 and, by means of the transmission module 16 , to the rear wheel 6 .

In a second operating condition, the electric machine 4 is not connected to the transmission 5 . In particular, the torque is supplied by means of muscle force to the pedals 3 , which rotate the pedal shaft 2 , which causes the rotation of the wheel 30a and thus of the wheels 30b' . These cause the rotation of the respective support shaft 11 ' , 13 ' , which causes the rotation of the gearwheels 31 , 32 , which mesh with the gearwheels 22 . One of the gearwheels 31 , 32 is selected to define a desired gear shi ft and thus transmits torque to the gearwheels 22 and thus to the first support shaft 12 ' . The first support shaft 12 ' is therefore rotated according to the coupling indicated above and rotates freely on the pedal shaft 2 and, by means of the transmission module 16 , to the rear wheel 6 . In this condition, the bidirectional selective j oint 15 maintains the wheel 15 ' idle with respect to the third support shaft 13 ' so that the resistance torque to the shaft 4 ' of the electric machine 4 is not perceived by the user .

In a third operating condition, the electric machine 4 acts as generator . In particular, the rear wheel 6 causes the rotation by means of the transmission module 16 of the first support shaft 12 ' , which rotates freely on the shaft 2 . One of the gearwheels 31 , which allows the higher rotation speed of the third support shaft 13 ' , is thus made integral by the gear shift mechanism 26 and, meshing with the gearwheels 22 driven by the first support shaft 12' , rotates the third support shaft 13' . In this condition, the bidirectional selective joint 15 maintains the wheel 15' coupled to the third support shaft 13' so that the torque is supplied to the shaft of the electric machine 4, which generates electrical energy that can be stored in the storage means 7. Simultaneously, the freewheel mechanism 27 maintains the gearwheels 30b idle.

In a fourth operating condition, the electric machine 4 is connected to the transmission 5. In particular, the torque is supplied by means of muscle force to the pedals 3, which rotate the pedal shaft 2, which causes the rotation of the wheel 30a and thus of the wheels 30b' . These cause the rotation of the respective support shaft 11' , 13' , which causes the rotation of the gearwheels 31, 32, which mesh with the gearwheels 22. One of the gearwheels 31, 32 is selected to define a desired gear shift and thus transmit torque to the gearwheels 22 and thus to the first support shaft 12' . The first support shaft 12' is thus rotated according to the coupling indicated above and rotates freely on the pedal shaft 2 and, by means of the transmission module 16, to the rear wheel 6. In this condition, the bidirectional selective joint 15 maintains the wheel 15' integral with respect to the third support shaft 13' so that the muscle force supplied by the driver overcomes the resistance torque to the shaft 4' of the electric machine 4, recharging the storage means.

Operation of the embodiment of Fig. 3 is analogous to that of Fig. 2, with the difference that the functions of the transmission module 30 described above and the related gearwheels 30a, 30b' are actuated by the gears 34, 35 and by the gearwheels 34', 34'', 35', 35' ’ . Therefore, for brevity it will not be described in further detail. According to the operations illustrated above , the present invention thus relates to a method for controlling the electric machine 4 in pedal assist mode and a method for controlling the electric machine 4 in regenerative braking mode, alternatively to each other, or to a standard operation of the bicycle in which the electric machine is disconnected from the transmission 5.

The control method in regenerative braking mode is illustrated in Fig . 4 and comprises the steps of : i ) reading a signal indicating the braking request ; ii ) associating the braking request with a resistance torque to the electric machine to generate a specific current ; iii ) carrying out in parallel the checks in steps iv) -v) iv) if the maximum resistance torque that can be supplied by the electric machine has been reached, supply this maximum value ; v) if the charge limit of the electric batteries has been reached, supply a corresponding maximum resistance value ; vi ) return to step i ) .

The method can also comprise the following step between the steps v) , vi ) : vii ) checking whether it is possible to dissipate the electric charge generated, and if so, return to step v) , otherwise stop braking .

In particular, the association at step ii ) includes an analysis between braking torque that can be supplied by the electric machine 4 in regenerative braking mode and the force requested by the user . I f the force requested is greater than the force that can be supplied by the electric machine 4 , the remaining braking force is supplied mechanically . Clearly, the user could also not request any braking and in this way the regenerative braking would be applicable to a muscle recharging operation of the battery in which it is connected to the electric machine without any request for braking by the user .

The control method in pedal assist mode is illustrated in Fig . 5 and comprises the steps of : i ) reading a signal indicating the pedal assist request ; ii ) associating the speed/torque to the pedal shaft 2 with respect to a torque requested by the user to identify the request for driving torque ; iii ) carrying out in parallel the checks in steps iv) - and v) , vi ) ; iv) if the maximum driving torque that can be supplied by the electric machine has been reached, supply this maximum value ; v) if the discharge limit of the electric batteries has been reached, supply a corresponding maximum driving torque value ; vi ) return to step i ) .

The method can also comprise the following steps between the step v) and the step vi ) : vii ) if the discharge limit of the electric batteries has not been reached, check whether their maximum charge level has been reached; viii ) if the check in step vi ) is positive, checking if it is possible to dissipate the electric charge generated, and i f so, return to step v) , otherwise stop braking .

In particular, the association at step ii ) includes an analysis between torque requested and the torque supplied by the user in order to identify the necessary torque to be imparted by the electric machine 4 . The methods described above can advantageously be stored as instructions in code in the processing means of the electronic unit which is configured to carry out the control steps at a predetermined interval of time , of the order of less than one second, so as to guarantee substantially continuous monitoring of the pedal assist and regenerative braking control .

The electronic unit 8 thus comprises stored threshold values of the measurements involved in the methods of Figs . 4 and 5. Some of these values can, optionally, be variable by the user, such as the minimum charge threshold of the electric batteries .

From the above , the advantages of a hybrid drive system, a bicycle and a related control method according to the invention are evident .

Thanks to the transmission proposed, it is possible to provide a drive system that selectively connects the electric machine to the rear wheel and pedal shaft so as to allow a muscle, pedal assist or regenerative braking mode that is always optimal .

In particular, in muscle mode the electric machine is disconnected in order not to increase the resistance torque .

In regenerative braking mode, the transmission optimizes the input speed to the electric machine so that it is at maximum speed . Likewise, in pedal assist mode, it optimizes the output torque so that it is at the maximum traction value .

Moreover, the arrangement substantially coaxial to the pedal shaft makes it possible to occupy a limited space in an area of the frame having large housing spaces . In this way, it is possible to free the rear wheel , where electric machines for pedal assist are usually located . In this way it is possible to provide a single protective casing for the hybrid drive system so as to protect it from the external environment and increase its useful life, as well as reducing costs and weight .

Finally, it is clear that modifications and variants can be made to the hybrid drive system, bicycle and related control method according to the present invention, without departing from the scope of protection defined by the claims .

For example, the number of gearwheels described to represent the different gear ratios or the number of transmission countershafts can vary . Further, the aforesaid selective j oints , gear shift mechanisms or freewheels can be produced in different ways .

Similarly, the transmission modules can comprise di fferent speed variations to those described .