NO20211103A1

NO20211103A1 - Drivenhet for artikkel med hjul

Info

Publication number: NO20211103A1
Application number: NO20211103A
Authority: NO
Inventors: Henrik Karlstad; Atle Stubberud
Original assignee: Smartgroup As
Priority date: 2021-09-16
Filing date: 2021-09-16
Publication date: 2023-03-17

Description

DRIVE UNIT FOR WHEELED ARTICLE

FIELD

The present invention relates generally to a drive unit for a wheeled article, particularly for a wheeled article which is selectably operational in at least manual and powered modes.

BACKGROUND ART

There is a certain need for a manual operation wheeled article capable of switching to a powered operation mode according to circumstances. Such a wheeled article may be a wheelchair, child or baby carrier, child bike, transport trolley, etc.

In the field of wheelchairs, for instance, there are two types of wheelchairs: powered wheelchairs, where propulsion is provided by electric motors; and manually propelled wheelchairs, where the propulsive power is provided either by the wheelchair user or by an attendant pushing the wheelchair. And if the manual operation wheelchair is capable of switching to the powered operation mode according to circumstances, this may provide the potential to dramatically increase the range of activity of manual wheelchair users. With such additional motor power, manual wheelchair users may be able to make trips uphill by means of the powered drive when such trips were too steep for human power. Extension of travel distance may also be expected.

SUMMARY

It is an object of the invention, therefore, to provide a drive unit for a wheeled article, particularly for a multi-mode wheeled article which is selectably operational in at least manual and powered modes. Further objects and advantages of the present invention will be apparent from the detailed description as below.

According to the present invention there is provided a drive unit for a wheeled article, comprising: a first shaft, a first or both ends of which being configured to be connectable with one or more wheels to be driven of the wheeled article; a first electric motor configured to provide torque to the first shaft; and a first clutch arranged in a first torque transmission path between the first electric motor and the first or both ends of the first shaft.

In one embodiment, the first end of the first shaft is configured to be connectable with one of the driven wheels. The drive unit comprises: a second shaft, a first end of which is configured to be connectable with another of the driven wheels; and a second clutch arranged in a second torque transmission path between the first electric motor and the first end of the second shaft.

In another embodiment, the first end of the first shaft is configured to be connectable with one of the driven wheels. The drive unit further comprises: a second shaft, a first end of which is configured to be connectable with another of the driven wheels; a second electric motor configured to provide torque to the second shaft; and a second clutch arranged in a second torque transmission path between the second electric motor and the first end of the second shaft.

It is preferable that axes of the first and second shafts and rotation axes of the first and second electric motors are aligned with each other to form a common axes.

It is more preferable that the drive unit further comprises a housing inside which the first and second electric motors are held in a slidable manner in a direction of the common axis.

It is further preferable that each of the first and second clutches is a dog clutch including a driving member and a driven member, and the first and second clutches are switched between connected and disconnected states in accordance with sliding movements of the first and second electric motors.

Alternatively, the first and second clutches is a ball clutch including a plug member, a socket member for rotatably receiving the plug member, and one or more torque transmission balls for transmitting the torque between the socket member and the plug member when the plug member is fully inserted in the socket member. The first and second clutches are switched between connected and disconnected states in accordance with sliding movements of the first and second electric motors.

It is preferable that the drive unit further comprises an actuator unit configured to simultaneously slide the first and second electric motors with respect to the housing.

It is more preferable that the actuator unit includes a rotation servo motor and a crank mechanism configured to convert a rotational movement of the rotation servo motor into sliding movement of the first and second electric motors with respect to the housing.

Alternatively, the actuator unit includes a hydraulic or pneumatic cylinder, and a link mechanism configured to convert a linear movement of the cylinder into the sliding movement of the first and second electric motors with respect to the housing.

It is preferable that the drive unit further comprises a biasing means for biasing the first and second clutches to be in the disconnected state, and the actuator unit is configured to connect the first and second clutches against the biasing means in the powered mode. The biasing means may include a spring. The spring is preferably a torsion spring which is arranged between the rotation servo motor and the crank mechanism.

It is preferable that the housing includes one or more guide ribs for the first and second electric motors, the guide ribs extending in the direction of the axis.

It is more preferable that each of the first and second motors includes one or more grooves for receiving the respective guide ribs, the grooves extending in the direction of the common axis.

It is preferable that the drive unit further comprises a first rotation braking device for the first shaft and/or a second rotation braking device for the second shaft.

It is more preferable that the first rotation braking device is arranged between the first clutch and the one end of the first shaft, and the second rotation braking device is arranged between the second clutch and the one end of the second shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

The principle of the invention will now be more fully described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a is a schematic view of a wheelchair drive system comprising a drive unit according to an embodiment of the present invention;

FIG. 2 is a is a schematic view of a wheelchair drive system comprising a drive unit according to another embodiment of the present invention;

FIG. 3 is a is a schematic view of a wheelchair drive system comprising a drive unit according to yet another embodiment of the present invention;

FIG. 4 is a is a schematic view of a wheelchair drive system comprising a drive unit according to yet another embodiment of the present invention;

FIG. 5 is a perspective view of a drive unit according to the embodiment shown in FIG. 4;

FIG. 6 is a perspective view of the drive unit of FIG. 5 with a cover removed for exposing the inside;

FIG. 7A is a perspective view of a part of the drive unit of FIG. 5 illustrating a crank mechanism of an actuator unit;

FIG. 7B is a front view of the crank mechanism of FIG. 7A;

FIG. 8 is a perspective view of a part of the drive unit of FIG. 5 illustrating a biasing means arranged between a servo motor and the crank mechanism;

FIG. 9 is a cross-sectional view of the drive unit of FIG. 5, along a plane perpendicular to the axis of the drive unit;

FIG. 10A is a cross-sectional view of the drive unit of FIG. 5, along the axis of the drive unit, illustrating disconnected states of clutches;

FIG. 10B is a cross-sectional view of the drive unit of FIG. 5, along the axis of the drive unit, illustrating connected states of the clutches;

FIG. 11 is a perspective view of a part of another exemplary drive unit comprising ball clutches, according to the present invention,

FIG. 12A is a cross-sectional view of the ball clutch of FIG. 11, illustrating the disconnected state thereof; and

FIG. 12B is a cross-sectional view of the ball clutch of FIG. 11, illustrating the connected state thereof.

DETAILED DESCRIPTION

The present invention is directed to a drive unit for a multi-mode wheeled article which is selectably operational in at least manual and powered modes. The wheeled article, however, may have additional modes such as a torque assist mode in which one or more electric motors is used to assist human power moving the wheeled article. It should also be understood that the drive unit of the present invention is not limited to the wheelchair application, and may also be applied to other wheeled articles such as a child or baby carrier, child bike, transport trolley, tricycle, handbike, other mobility items and the like.

With reference to FIGS. 1 to 4, four exemplary drive units 10A-10D of the present invention are respectively shown. As can be seen, the wheelchair has four wheels: two caster wheels Fa, Fb at the front and two larger main wheels Ra, Rb at the rear. The rear wheels Ra, Rb may be provided with hand-rims which are slightly smaller in diameter than tyres of the rear wheels Ra, Rb. This is by way of example only, and any form of the wheels would benefit from the enclosed disclosure. Furthermore, the following disclosure generally provides torque to the rear wheels Ra, Rb – again, this is by example only and the torque can be sent to any desired driven wheel, or set of driven wheels.

The drive unit 10A shown in FIG. 1 includes: a first shaft 12a, both ends of which are configured to be connectable with the respective rear wheels Ra, Rb of the wheelchair; a first electric motor 14a configured to provide torque to the first shaft 12a; and a first clutch 16a arranged in a first torque transmission path from the first electric motor 14a to both ends of the first shaft 12a. The first clutch 16a may be configured with one or more gears which transmit the torque from the first electric motor 14a to the first shaft 12a. The gear as the clutch may be slidable in the direction of the axis of the first shaft 12a to engage or disengage with the other gear of the gear set. Alternatively, the first clutch 16a may be configured with a switchable or selectable one-way clutch that can hold torque or allow freewheel in one or both directions. Another exemplary clutch is a dog clutch (FIG. 6) or a ball clutch (FIGS. 11 and 12). The clutches in this embodiment and those described below will allow for the selective connection of the respective electric motor 14a and/or 14b to the respective wheel Ra, Rb when in powered mode for the wheelchair and will also disconnect the respective electric motor 14a, 14b from the respective wheel Ra, Rb when in manual mode for the wheelchair.

The drive unit 10A may further include a rotation braking device 18a. Any know brake system may be used. One example braking device 18a is a disc brake system having a disc and a brake calliper. The brake calliper incorporates one or more brake pads that are hydraulically or electrically driven and pressed against the disc to generate a frictional force. An alternative braking device may be configured to press one or more brake pads (not shown) directly against the surface of the first shaft 12a. Another braking device may be an eddy-current brake system. In this sense, the first electric motor 14a may be employed as the eddy-current braking means. To this end, the first electric motor (generator) may be switched to a regeneration mode. The generated electricity may be used to charge a battery 20.

As shown in FIG. 2, the drive unit 10B according to the second embodiment of the invention includes: a first shaft 12a, a first end of which is configured to be connectable with one Ra of the rear wheels Ra, Rb; a second shaft 12b, a first end of which is configured to be connectable with the other Rb of the rear wheels Ra, Rb; a first electric motor 14a configured to provide torque to both the first and second shafts 12a, 12b; a first clutch 16a arranged in a first torque transmission path between the first electric motor 14a and the first end of the first shaft 12a; and a second clutch 16b arranged in a second torque transmission path between the first electric motor 14a and the first end of the second shaft 16b.

In this embodiment, since each transmission path includes a clutch 16a, 16b, the rear wheels Ra, Rb may be independently driven by independently connecting/disconnecting the first and second clutches 16a, 16b. This contributes to a smaller turning radius for the wheelchair, even with only one electric motor 14a. Any clutch as described in relation to the embodiment of FIG. 1 may be used with the embodiment of Fig. 2.

The drive unit 10B may include a first rotation braking device 18a and a second rotation braking device 18b. It is preferable that the first braking device 18a is arranged between the first end of the first shaft 12a and the first clutch 16a, and the second braking device 18b is arranged between the first end of the second shaft 12a and the second clutch 16b. As such, the first and second rotation braking devices 18a, 18b are respectively arranged downstream of the first and second clutches 16a, 16b in the first and second torque transmission directions. This ensures that the braking torques generated in the first and second braking devices 18a, 18b are transmitted to the rear wheels Ra, Rb, even in the state that the first and second clutches 16a, 16b are disconnected in the manual mode. Any brake system as described in relation to the embodiment of FIG. 1 may be used with the embodiment of Fig. 2.

As shown in FIG. 3, the drive unit 10C according to the third embodiment of the invention includes: a first shaft 12a, a first end of which is configured to be connectable with one Ra of the rear wheels Ra, Rb; a second shaft 12b, a first end of which is configured to be connectable with the other Rb of the rear wheels Ra, Rb; a first electric motor 14a configured to provide torque to the first shaft 12a; a second electric motor 14b configured to provide torque to the second shaft 12b; a first clutch 16a arranged in a first torque transmission path between the first electric motor 14a and the first end of the first shaft 12a; and a second clutch 16b arranged in a second torque transmission path between the second electric motor 14b and the first end of the second shaft 12b.

In this embodiment, since the drive unit includes two electric motors 14a, 14b for the respective torque transmission paths, the rear wheels Ra, Rb may be independently driven from each other by independently controlling the first and second electric motors 14a, 14b. This contributes a smaller turning radius for the wheelchair.

Further, since the two independently controllable motors 14a, 14b are provided in this embodiment, and by controlling these motors independently from one another in the clutch connected state, there is no need to switch the clutches16a, 16b for the independent driving of the rear wheels Ra, Rb, resulting in quick and timely operation thereof.

Any clutch as described in relation to the embodiment of FIG. 1 may be used with the embodiment of Fig. 3.

The drive unit may include a first rotation braking device 18a and a second rotation braking device 18b. It is preferable that the first braking device 18a is arranged between the first end of the first shaft 12a and the first clutch 16a, and the second braking device 18b is arranged between the first end of the second shaft 12b and the second clutch 16b. As such, the first and second rotation braking devices 18a, 18b are respectively arranged downstream of the first and second clutches 16a, 16b in the first and second torque transmission directions. This ensures that the braking torques generated in the first and second braking devices 18a, 18b are transmitted to the rear wheels Ra, Rb, even in the state that the first and second clutches 16a, 16b are disconnected in the manual mode. Any brake system as described in relation to the embodiment of FIG. 1 may be used with the embodiment of Fig. 3.

As shown in FIG. 4, the drive unit 10D according to the fourth embodiment of the invention includes: a first shaft 12a, a first end of which is configured to be connectable with one Ra of the rear wheels Ra, Rb; a second shaft 12b, a first end of which is configured to be connectable with the other Rb of the rear wheels Ra, Rb; a first electric motor 14a configured to provide torque to the first shaft 12a; a second electric motor 14b configured to provide torque to the second shaft 12b; a first clutch 16a arranged in a first torque transmission path between the first electric motor 14a to the first end of the first shaft 12a; and a second clutch 16b arranged in a second torque transmission path between the second electric motor 14b and the first end of the second shaft 12b. The first and second shafts 12a, 12b and the first and second electric motors 14a, 14b are arranged on the same axis, i.e., in a coaxial manner. This provides a compact driving unit as compared with the arrangement shown in FIG. 3. Also, as with the drive unit 10C of FIG. 3, since the drive unit 10D includes two separate electric motors 14a, 14b for the respective torque transmission paths, the rear wheels Ra, Rb may be driven independently from each other by independently controlling the first and second electric motors 14a, 14b. This contributes to a smaller turning radius for the wheelchair. Further, since the two independently controllable motors 14a, 14b are provided in this embodiment, and by controlling these motors independently from one another in the clutch connected state, there is no need to switch the clutches 16a, 16b for the independent driving of the rear wheels Ra, Rb, resulting in quick and timely operation thereof.

Any clutch as described in relation to the embodiment of FIG. 1 may be used with this arrangement.

The drive unit 10D may include a first rotation braking device 18a and a second rotation braking device 18b. It is preferable that the first braking device 18a is arranged between the first end of the first shaft 12a and the first clutch 16a, and the second braking device 18b is arranged between the first end of the second shaft 12a and the second clutch 16b. As such, the first and second rotation braking devices 18a, 18b are respectively arranged downstream of the first and second clutches 16a, 16b in the first and second torque transmission directions from the respective electric motor 14a, 14b. This ensures that the braking torques generated in the first and second rotation braking devices 18a, 18b are transmitted to the rear wheels Ra, Rb, even in the state that the first and second clutches 16a, 16b are disconnected in the manual mode. Any brake system as described in relation to the embodiment of FIG. 1 may be used with the embodiment of Fig. 4.

With reference again to FIGS. 1 to 4, each drive unit 10A-10D may further include a control unit (computer unit) 22 configured to control the operation of the first electric motor 14a and/or the second electric motor 14b and/or the first rotation braking device 18a and/or the second rotation braking device 18b and/or the first clutch 16a and/or the second clutch 16b. The control unit 22 may include a suitable controller or microprocessor configured to control the actuation of the respective elements in the drive unit upon operation of a human interface 24, such as a joystick controller mounted on the wheelchair. Any known human interface 24 is appropriate to allow the user to control the operation of the wheelchair. The control unit 22 may include a read-only memory (ROM) which is configured to store various programs to control the respective elements in the drive unit, and a random-access memory (RAM) which is configured to temporarily store computation results. The control circuit 22 may further include a communication section configured to communicate with the joystick controller, or the like, via a suitable communication interface. Wired or any suitable wireless communication technology such as Bluetooth® or Wi-Fi may be used.

Additionally or alternatively, one or more mobile computers such as a smart phone in association with a suitably programmed, installed application (software), and/or one or more remote controllers may be used as the human interface to control the drive unit. The remote controller may be operated by an attendant of the wheelchair user.

Further, any of the drive units 10A, 10B, 10C, 10D may include one or more torque sensors on the first and/or second shaft 12a, 12b. The detected torque may be used to calculate an assist torque for assisting or compensating the human power of the wheelchair user in the assist mode. In this case, the control unit 22 may be configured to calculate the assist torque and control the first and/or second motor 14a, 14b to generate the assist torque. The assist torque may be equal to or less than the detected torque.

The following details of construction and illustrations are made with reference to the driving device 10D according to the fourth embodiment. However, any feature and part described therein may equally be applied to other embodiments to embody the invention in any of the actual drive units 10A, 10B, 10C, 10D.

FIGS. 5 and 6 illustrate the drive unit 10D according to the fourth embodiment of the invention. The drive unit 10D includes a cover 26 to be fixed to the wheelchair, in particular under the seat of the wheelchair; although any other fixing location as required by the specific wheelchair design can be considered. Inside the cover 26 is a housing 28 slidably holding the first and second electric motors 14a, 14b therein. Each motor 14a, 14b is configured to be able to slide in the direction of the rotation axis thereof. In this example, the rotation axes of the electric motors 14a, 14b and the axes of the first and second shafts 12a, 12b are aligned with each other to form a common axis. Although not shown, one or more battery 20 and/or control unit 22 and/or other elements of the drive unit may be arranged inside the cover 26.

An output shaft of the first electric motor 14a is connected to the first shaft 12a in a torque transmittable manner, and the output shaft of the second electric motor 14b is connected to the second shaft 12b in a torque transmittable manner. The proximal portions of the first and second shaft 12a, 12b are supported by bearing sleeves 30a, 30b which are fixed to the respective axial ends of the cover 26. The distal ends of the first and second shafts 12a, 12b extend beyond the sleeves 30a, 30b for the connection with the rear wheels Ra, Rb. The first and second braking devices 18a, 18b (FIG. 4), where applicable, may be arranged on the extended sections of the first and second shafts 12a, 12b.

The first clutch 16a is arranged on or in the first shaft 12a, and the second clutch 16b is arranged on or in the second shaft 12b. In a non-limiting example, each clutch 16a, 16b is a dog clutch including a driving member 160 and a driven member 161 that face each other in the direction of the axis of the first and second shafts 12a, 12b. The driving member 160 has a set of regularly spaced teeth or protrusions, and the driven member 161 has a set of mating teeth or recesses.

As shown in FIGS. 7 and 8, the drive unit 10D further includes an actuator unit 32 positioned between the first and second electric motors 14a, 14b, as viewed along the axis of the first and second shafts 12a, 12b. The actuator unit 32 is configured to simultaneously slide the first and second electric motors 14a, 14b with respect to the housing 28 toward the respective driven members 161, 161 of the respective clutches 16a, 16b.

In a non-limiting example, the actuator unit 32 includes a rotation servo motor 34, and a crank mechanism 36 configured to convert the rotational movement of the rotation servo motor 34 into the sliding movement of the first and second electric motors 14a, 14b with respect to the housing 28. It is noted that the rotation servo motor 34 is a non-limiting option in the actuator unit 32, other motors may also fulfil the functions thereof. The crank mechanism 36 includes a link 36a attached to the output shaft of the servo motor 34, and two arms 36b, 36c. Each of the two arms 36b, 36c is pivotably attached at respective first ends thereof to the link 36a at respective ends of the link 36a and to the electric motors 14a, 14b at respective second ends. When the servo motor 34 is activated, the first and second electric motors 14a, 14b are pushed by the arms 36b, 36c, via rotation of the link 36, toward the driven members 161, 161 of the clutches 16a, 16b to engage the driving members 160, 160 with the driven members 161, 161, respectively. As such, the first and second electric motors 14a, 14b are torque-transmittably connectable and connected to the wheels of the wheelchair to be driven via the clutches 16a, 16b. The first and second electric motors 14a, 14b may be controlled by the control unit 22 upon the operation of the human interface 24 such as a joystick controller or smart phone, as discussed above. The rotational speeds of the first and second electric motors 14a, 14b may be independently governed to steer the wheelchair.

As an alternative to the servo motor 34 or non-servo motor, although not shown, a hydraulic or pneumatic cylinder may be used. In this case, a link mechanism may be provided to convert a linear movement of the cylinder into the sliding movements of the first and second electric motors 14a, 14b with respect to the housing 28. A parallel link mechanism such as a pantograph mechanism may be used as the link mechanism.

It is preferable that the drive unit 10D includes a biasing means for biasing the first and second clutches 16a, 16b to be in the disconnected state. In such a case, the actuator unit 32 is configured to connect the first and second clutches 16a, 16b against the biasing means when the wheelchair is operated in the powered mode, and where applicable in the power assist mode as well. Alternatively, the biasing means may bias the first and second clutches 16a, 16b to be in the connected state.

In the illustrated example, the biasing means includes a torsion spring 38 (FIG. 8) which is arranged on the crank mechanism 36 to withdraw the arms 36b, 36c.

As an alternative to the torsion spring 38, although not shown, one or more tension springs may be provided between the opposing axial ends of the first and second electric motors 14a, 14b. One or more pairs of magnets may also be used for that purpose.

FIG. 9 illustrates a cross section of the drive unit 10D along a plane perpendicular to the axis of the drive unit 10D. The housing 28 for slidably holding the first and second electric motors 14a, 14b can been seen. The housing 28 is held in place within the cover 26. In a preferable example as depicted, the housing 28 includes one or more guide ribs 28a projecting radially inside and extending in the direction of the rotation axis of the motors 14a, 14b. In the non-limiting, illustrated example, four guide ribs 28a are provided at equal intervals in the circumferential direction. Each motor 14a, 14b includes one or more grooves 140 on its outer periphery for receiving the respective guide ribs 28a, each of which extending in the direction of the rotation axis of the motor. This ensures a smooth and stable sliding movement of the electric motor 14a, 14b on one hand, and prevents reactive rotation of the motor shell with respect to the motor shaft on the other hand.

With reference to FIGS. 10A and 10B, the primary operations of the drive unit 10D are illustrated. FIG. 10A shows the manual mode in which the first and second electric motors 14a, 14b are positioned close to each other, with the help of the torsion spring 38 where appropriate, so that the first and second clutches 16a, 16b are held in the disconnected state. The driven wheels Ra, Rb are thus freely rotatable without resistance torque from the electric motors 14a,14b.

In contrast, FIG. 10B shows the powered or power assist mode. In either of these two modes, the actuator unit 32 is activated to simultaneously slide the first and second electric motors 14a, 14b toward the driven members 161, 161 of the clutches 16a, 16b against the bias of the torsion spring 38 where applicable, leading to the first and second clutches 16a, 16b being switched to the connected state for transmittal of torque from the motors 14a, 14b to the driven wheel(s). The driven, in this case rear, wheels Ra, Rb are thus driven with the respective torques from the electric motors 14a, 14b.

Referring now to FIGS. 11 and 12, another version of the clutch is illustrated as an alternative to the dog clutch shown in FIG. 6. This version refers to a ball clutch 16’ that provides a smoother connection than the dog clutch. The ball clutch 16’ includes a plug member 161’, a socket member 160’ for rotatably receiving the plug member 161’, and one or more torque transmission balls 162 for transmitting the torque between the socket member 160’ and the plug member 161’ when the plug member 161’ is fully inserted in the socket member 160’. The balls 162 are retained in cages (recesses) 163 formed in the plug member 161’ so that the balls 162 partially project out of radially outward-facing windows 163a of the cages 163. Each cage 163 also includes an inclined floor 163b which is located so as to face the window 163a and force the ball 162 to partially project out of the window 163a when the plug member 161’ is fully inserted in the socket member 160’. The socket member 160’ includes engaging grooves 164 that come into contact with the respective balls 162 when the balls 162 partially project out of the windows 163a. As such, the plug member 161’ is freely rotatable with respect to the socket member 161’ when the plug member 161’ is partially inserted in, or removed from, the socket member 160’, whereas the plug member 161’ and the socket member 160’ are non-rotatably connected with each other when the plug member 161’ is fully inserted in the socket member 160’ upon the sliding movement of the first and second electric motors 14a, 14b.

Whilst the present invention has been illustrated by the description of example drive unit, the Applicant does not intend to restrict or in any way limit the scope of the appended claims to such detail. Additional modification will also readily appear to those skilled in the art.

LIST OF REFERENCE NUMERALS

10A-10D Drive unit

12a First shaft

12b Second shaft

14a First motor

14b Second motor

140 Groove

16a First clutch

16b Second clutch

160 Driving member

161 Driven member

16’ Ball clutch

160’ Socket member

161’ Plug member

162 Torque transmission ball

18a First braking device

18b Second braking device

20 Battery

22 Control unit

24 Human interface

26 Cover

28 Housing

28a Guide rib 30a, 30b Bearing sleeve

32 Actuator unit

34 Rotation servo motor 36 Crank mechanism 36a link

36b, 36c Arm

38 Torsion spring

Claims

1. A drive unit for a wheeled article comprising:

a first shaft, a first or both ends of which being configured to be connectable with one or more wheels to be driven of the wheeled article;

a first electric motor configured to provide torque to the first shaft; and

a first clutch arranged in a first torque transmission path between the first electric motor and the first or both ends of the first shaft.

2. The drive unit according to claim 1,

wherein the first end of the first shaft is configured to be connectable with one of the driven wheels,

the drive unit further comprising:

a second shaft, a first end of which is configured to be connectable with another of the driven wheels; and

a second clutch arranged in a second torque transmission path between the first electric motor and the first end of the second shaft.

3. The drive unit according to claim 1,

the drive unit further comprising:

a second shaft, a first end of which is configured to be connectable with the other of the driven wheels;

a second electric motor configured to provide torque to the second shaft; and

a second clutch arranged in a second torque transmission path between the second electric motor and the first end of the second shaft.

4. The drive unit according to claim 3, wherein axes of the first and second shafts and rotation axes of the first and second electric motors are aligned with each other to form a common axis.

5. The drive unit according to claim 3 or 4, further comprising a housing inside which the first and second electric motors are held in a slidable manner in a direction of the common axis.

6. The drive unit according to claim 5, wherein each of the first and second clutches is a dog clutch including a driving member and a driven member, and

wherein the first and second clutches are configured to be switched between connected and disconnected states in accordance with sliding movements of the first and second electric motors.

7. The drive unit according to claim 5, wherein each of the first and second clutches is a ball clutch including a plug member, a socket member for rotatably receiving the plug member, and one or more torque transmission balls for transmitting the torque between the socket member and the plug member when the plug member is fully inserted in the socket member, and

8. The drive unit according to 6 or 7, further comprising an actuator unit configured to simultaneously slide the first and second electric motors with respect to the housing.

9. The drive unit according to claim 8, wherein the actuator unit includes a rotation servo motor and a crank mechanism configured to convert a rotational movement of the rotation servo motor into sliding movement of the first and second electric motors with respect to the housing.

10. The drive unit according to claim 8, wherein the actuator unit includes a hydraulic or pneumatic cylinder, and a link mechanism configured to convert a linear movement of the cylinder into the sliding movement of the first and second electric motors with respect to the housing.

11. The drive unit according to any one of claims 6 to 10, further comprising a biasing means for biasing the first and second clutches to be in the disconnected state,

wherein the actuator unit is configured to connect the first and second clutches against the biasing means in the powered mode.

12. The drive unit according to claim 11, the biasing means includes a spring.

13. The drive unit according to claim 12 depending on claim 9, wherein the spring is a torsion spring which is arranged between the rotation servo motor and the crank mechanism.

14. The drive unit according to any one of claims 5 to 13, wherein the housing includes one or more guide ribs for the first and second electric motors, the guide ribs extending in the direction of the common axis.

15. The drive unit according to claim 14, wherein each of the first and second motors includes one or more grooves for receiving the respective guide ribs, the grooves extending in the direction of the axis.

16. The drive unit according to claim 1 or 2, further comprising a first rotation braking device for the first shaft.

17. The drive unit according to any one of claims 3 to 15, further comprising a first rotation braking device for the first shaft, and a second rotation braking device for the second shaft.

18. The drive unit according to claim 17, wherein the first rotation braking device is arranged between the first clutch and the first end of the first shaft, and the second rotation braking device is arranged between the second clutch and the first end of the second shaft.