Power tool motor braking using magnetically susceptible fluid

Patent metadata

Field	Value
Publication number	US-12418216-B2
Application number	US-202318451171-A
Country	US
Kind code	B2
Filing date	Aug 17, 2023
Priority date	Aug 19, 2022
Publication date	Sep 16, 2025
Grant date	Sep 16, 2025

Abstract

Systems and methods for braking a power tool motor using a magnetically susceptible fluid. One power tool includes a housing, a motor within the housing, a drive train coupled to the motor, a magnetically susceptible fluid located within the drive train, and an inductor within the housing and configured to introduce a magnetic field to the magnetically susceptible fluid. An electronic controller is connected to the motor and to the inductor and is configured to receive a signal to initiate a braking process, generate, in response to the initiation of the braking process, a control signal for the inductor, and provide the control signal to the inductor to control a viscosity of the magnetically susceptible fluid located within the drive train.

First claim

What is claimed is:

1. A power tool comprising:
a housing;
a motor within the housing;
a drive train coupled to the motor;
a magnetically susceptible fluid located within the drive train;
an inductor within the housing and configured to introduce a magnetic field to the magnetically susceptible fluid; and
an electronic controller including a memory and an electronic processor, the electronic controller connected to the motor and to the inductor, the electronic controller configured to:
receive a signal to initiate a braking process,
generate, in response to the signal to initiate the braking process, a control signal for the inductor, and
provide the control signal to the inductor to control a viscosity of the magnetically susceptible fluid located within the drive train.

2. The power tool of claim 1 , wherein the drive train includes:
one or more gears, wherein the magnetically susceptible fluid is configured to lubricate the one or more gears when in a non-magnetized state.

3. The power tool of claim 1 , wherein the viscosity of the magnetically susceptible fluid is proportional to a strength of the magnetic field.

4. The power tool of claim 1 , wherein the magnetically susceptible fluid is a magneto-rheological fluid including a plurality of magnetizable particles.

5. The power tool of claim 4 , wherein the electronic controller is further configured to:
provide the control signal to the inductor to magnetize the plurality of magnetizable particles.

6. The power tool of claim 1 , wherein the electronic controller is further configured to:
determine whether the motor has braked to a stop; and
stop, in response to the motor being braked to a stop, providing the control signal to the inductor.

7. The power tool of claim 1 , wherein the electronic controller is further configured to:
receive, from an external device, one or more braking parameters; and
generate the control signal for the inductor based on the one or more braking parameters.

8. The power tool of claim 7 , wherein the one or more braking parameters include at least one selected from a group consisting of a minimum viscosity of the magnetically susceptible fluid, a maximum viscosity of the magnetically susceptible fluid, a braking force applied by the magnetically susceptible fluid, and an amount of time to provide the control signal to the inductor.

9. A method for braking a power tool, the method comprising:
receiving a signal to initiate a braking process to brake a motor, wherein the motor is coupled to a drive train;
generating, in response to the signal to initiate the braking process, a control signal for an inductor, the inductor configured to introduce a magnetic field to a magnetically susceptible fluid within the drive train; and
providing, during the braking process, the control signal to the inductor to control a viscosity of the magnetically susceptible fluid within the drive train.

10. The method of claim 9 , further comprising:
lubricating, with the magnetically susceptible fluid, one or more gears within the drive train.

11. The method of claim 9 , wherein the magnetically susceptible fluid is a magneto-rheological fluid including a plurality of magnetizable particles, and the method further comprising:
providing the control signal to the inductor to magnetize the plurality of magnetizable particles.

12. The method of claim 9 , further comprising:
determining whether the motor has braked to a stop; and
stopping, in response to the motor being braked to a stop, providing the control signal to the inductor.

13. The method of claim 9 , further comprising:
receiving, from an external device, one or more braking parameters; and
generating the control signal for the inductor based on the one or more braking parameters.

14. The method of claim 13 , wherein the one or more braking parameters include at least one selected from a group consisting of a minimum viscosity of the magnetically susceptible fluid, a maximum viscosity of the magnetically susceptible fluid, a braking force applied by the magnetically susceptible fluid, and an amount of time to provide the control signal to the inductor.

15. A power tool comprising:
a housing;
a trigger;
a motor within the housing;
a drive train coupled to the motor;
a magnetically susceptible fluid located within the drive train;
an inductor within the housing and configured to introduce a magnetic field to the magnetically susceptible fluid;
an electronic controller including a memory and an electronic processor, the electronic controller connected to the trigger, the motor, and the inductor, the electronic controller configured to:
drive, in response to actuation of the trigger, the motor,
initiate, in response to de-actuation of the trigger, a braking event, and
provide, during the braking event, current to the inductor to control a viscosity of the magnetically susceptible fluid located within the drive train.

16. The power tool of claim 15 , wherein the drive train includes:
one or more gears, wherein the magnetically susceptible fluid is configured to lubricate the one or more gears when in a non-magnetized state.

17. The power tool of claim 15 , wherein the magnetically susceptible fluid is a magneto-rheological fluid including a plurality of magnetizable particles.

18. The power tool of claim 17 , wherein the electronic controller is further configured to:
provide the control signal to the inductor to magnetize the plurality of magnetizable particles.

19. The power tool of claim 15 , wherein the electronic controller is further configured to:
receive, from an input device, one or more braking parameters; and
generate the control signal for the inductor based on the one or more braking parameters.

20. The power tool of claim 19 , wherein the one or more braking parameters include at least one selected from a group consisting of a minimum viscosity of the magnetically susceptible fluid, a maximum viscosity of the magnetically susceptible fluid, a braking force applied by the magnetically susceptible fluid, and an amount of time to provide the control signal to the inductor.

Assignees

• Milwaukee Electric Tool Corp

Inventors

• Fieldbinder Douglas R
• Bhatt Nikita

Classifications

• H02K7/145

  Hand-held machine tool · CPC title

• F16D57/002 Primary

  comprising a medium with electrically or magnetically controlled internal friction, e.g. electrorheological fluid, magnetic powder · CPC title

• H02P3/04

  Means for stopping or slowing by a separate brake, e.g. friction brake or eddy-current brake · CPC title

• F16H57/0495

  with fixed gear ratio · CPC title

• H02K7/116

  with gears · CPC title