Electric working machine

Patent metadata

Field	Value
Publication number	US-10350720-B2
Application number	US-201715478691-A
Country	US
Kind code	B2
Filing date	Apr 4, 2017
Priority date	Apr 20, 2016
Publication date	Jul 16, 2019
Grant date	Jul 16, 2019

Abstract

An electric working machine comprises a motor, a switch, a drive device, a brake device, and a failure determiner. The switch is configured for operation by a user, has an on-state and an off-state. The drive device is configured to drive the motor in response to the switch being placed in the on-state. The brake device is configured to control deceleration of the motor to a stopped state in response to the switch being placed in the off-state. The failure determiner is configured to monitor deceleration of the motor during controlled deceleration and to determine whether the brake device has failed based on the monitored deceleration.

First claim

What is claimed is:

1. An electric working machine, comprising:
a motor;
a switch configured for operation by a user, the switch having an on-state and an off-state;
a drive device configured to drive the motor in response to the switch being placed in the on-state;
a brake device configured to control deceleration of the motor to a stopped state in response to the switch being placed in the off-state; and
a failure determiner configured to monitor deceleration of the motor during controlled deceleration and to determine whether the brake device has failed based on the monitored deceleration.

2. The electric working machine according to claim 1 , wherein the failure determiner is further configured to determine whether the brake device has failed based on whether the monitored deceleration falls outside a specified range of values.

3. The electric working machine according to claim 1 , wherein the failure determiner is further configured to notify the user whether the brake device has failed.

4. The electric working machine according to claim 1 , wherein the failure determiner is further configured to notify the user in the event the failure determiner determines that the brake device has failed.

5. An electric working machine comprising:
a motor;
a drive device configured to drive the motor;
a brake device configured to generate braking force to stop rotation of the motor when driving of the motor by the drive device is finished; and
a failure determiner configured to detect deceleration of the motor when the driving of the motor by the drive device is stopped and to determine whether the brake device has failed based on the deceleration.

6. The electric working machine according to claim 5 , wherein the failure determiner is configured to determine that the brake device has failed when the deceleration of the motor exceeds a specified maximum value.

7. The electric working machine according to claim 5 , wherein the failure determiner is configured to determine that the brake device has failed when the deceleration of the motor falls below a specified minimum value.

8. The electric working machine according to claim 5 , wherein the failure determiner is configured to notify a user of failure of the brake device when the brake device is determined to have failed.

9. The electric working machine according to claim 5 , wherein the failure determiner is configured to disable the drive device not to drive the motor when brake device is determined to have failed.

10. The electric working machine according to claim 5 , wherein the failure determiner is configured to allow the drive device to drive the motor for a specific period of time when the brake device is determined to have failed, and disable the drive device not to drive the motor after the specific period of time passes.

11. The electric working machine according to claim 5 , wherein the failure determiner is configured to sample number of revolutions of the motor at specific intervals and to detect the deceleration of the motor based on a difference between a most recent sampling result and a sampling result a specified period of time before.

12. A method for operating an electric working machine having a motor and a switch configured for operation by a user, the switch having an on-state and an off-state, the method comprising:
driving the motor in response to the switch being placed in the on-state;
controlling deceleration of the motor to a stopped state in response to the switch being placed in the off-state;
monitoring deceleration of the motor during controlled deceleration; and
determining whether the brake device has failed based on the monitored deceleration.

13. The method according to claim 12 , wherein determining whether the brake device has failed is based on whether the monitored deceleration exceeds a maximum value.

14. The method according to claim 12 , wherein determining whether the brake device has failed is based on whether the monitored deceleration is below a minimum value.

15. The method according to claim 12 , wherein determining whether the brake device has failed is based on whether the monitored deceleration falls outside a predetermined range of values.

16. The method according to claim 12 , further comprising notifying the user whether the brake device has failed.

17. The method according to claim 12 , further comprising notifying the user in the event that the brake device has failed.

18. The method according to claim 12 , further comprising disabling the motor in the event that the brake device has failed.

19. The method according to claim 12 , further comprising disabling the motor after a pre-determined period of time, in the event that the brake device has failed.

20. The method according to claim 12 , further comprising:
sampling the number of rotations of the motor at periodic intervals; and
monitoring deceleration based on the sampled numbers of rotations for the periodic intervals that are the most-recent and second most-recent intervals.

Assignees

• Makita Corp

Inventors

• Nakamoto Akihiro

Classifications

• H02P25/14

  Universal motors (H02P25/12 takes precedence) · CPC title

• H02P7/295

  of the kind having one thyristor or the like in series with the power supply and the motor · CPC title

• H02P3/18

  for stopping or slowing an AC motor · CPC title

• G01R31/343 Primary

  in operation · CPC title

• B23Q11/0085

  by determining whether the machine tool is in a dangerous configuration · CPC title