Drive assistance device for a wheel chair and a wheel chair having a drive assistance device

1. Drive assistance device for a wheel chair, comprising a

drive motor,

a driving wheel,

a sensor means which is adapted to detect a drive force manually induced into said driving wheel, and

a control unit which is adapted to control said drive motor for driving a driving wheel in accordance with a drive assistance degree depending on the drive force manually induced into the driving wheel,

wherein the control unit comprises an anti-rollback operational mode designed to control the drive motor such that an unintended rolling of the driving wheel is avoided.

2. Drive assistance device according to claim 1 , wherein the control unit operates in a normal operational mode in which avoiding of an unintended rolling of the driving wheel is disabled and, alternatively, in said anti-rollback operational mode, in which the drive motor is controlled such that an unintended rolling of the driving wheel is avoided.

3. Drive assistance device according to claim 2 , wherein the normal operational mode comprises a torque control which causes the drive motor for driving the driving wheel to be controlled in dependence on a driving force manually induced in said driving wheel.

4. Drive assistance device according to claim 3 , wherein the anti-rollback mode comprises a rotational frequency control in which the rotational frequency of the driving wheel is controlled.

5. Drive assistance device according to claim 4 , wherein in said anti-rollback operational mode alternatively the torque control or the rotational frequency control is used.

6. Drive assistance device according to claim 5 , wherein the control unit is designed such that a change between torque control and rotational frequency control is effected depending on operational parameters.

7. Drive assistance device according to claim 6 , characterized in that the operational parameters include one or more parameters of the group comprising: rotational frequency of the driving wheel, rotational direction of the driving wheel, magnitude of the driving force manually induced into the driving wheel, direction of the driving force manually induced into the driving wheel, sum of the torque resulting from the driving force manually induced into the driving wheel, and a torque provided by that driving motor in accordance with a drive assistance degree depending on the driving force manually induced into the driving wheel, the torque currently provided by said driving motor, the value of the timer switch.

8. Drive assistance device according to claim 1 , wherein the anti-rollback operational mode can be manually switched on or can be manually switched off or can be manually switched on and off.

9. Drive assistance device according to claim 8 , wherein a plurality of drive assistance degree switches is provided serving to preset different drive assistance degrees and wherein the anti-rollback operational mode can be switched on or off or on and off by one or each of said drive assistance degree switches.

10. Drive assistance device according to claim 9 , wherein the control unit is in the normal operational mode when switched on.

11. Drive assistance device according to claim 9 , wherein the control unit is, when switched on, in the same operational mode in which it had been before it was switched off.

12. Drive assistance device according to claim 1 , wherein a force can be manually induced into the driving wheel via a hand rim.

13. Drive assistance device according to claim 1 , wherein the drive motor is an electric motor.

14. Drive assistance device according to claim 13 , wherein the drive motor and a rechargeable battery and the control unit are housed in the hub of the driving wheel.

15. A wheel chair having the drive assistance device according to claim 1 .