Electronic braking for a power tool having a brushless motor

Patent metadata

Field	Value
Publication number	US-2017234484-A1
Application number	US-201715429821-A
Country	US
Kind code	A1
Filing date	Feb 10, 2017
Priority date	Feb 12, 2016
Publication date	Aug 17, 2017
Grant date	—

Abstract

A power tool is provided including a housing, a brushless direct-current (BLDC) electric motor disposed inside the housing, power switches disposed between a power supply and the electric motor and including high-side switches and low-side switches, and a control unit configured to control a switching operation of the power switches to operate the electric motor and electronically brake the motor by simultaneously activating the high-side switches or the low-side switches to stop the rotation of the motor upon detection of a condition prompting the braking of the motor. The control unit is configured to detect the condition that prompts the braking of the electric motor, set a braking profile for braking the electric motor based on the detected condition, and execute braking of the electric motor using the braking profile.

First claim

1 . A power tool comprising:
a housing; a brushless direct-current (BLDC) electric motor disposed inside the housing; a plurality of power switches disposed between a power supply and the electric motor, the plurality of power switches including a plurality of high-side switches and a plurality of low-side switches; and a control unit configured to control a switching operation of the plurality of power switches to operate the electric motor and electronically brake the motor by simultaneously activating the plurality of the high-side switches or the plurality of low-side switches to stop the rotation of the motor upon detection of a condition prompting the braking of the motor, wherein the control unit is configured to: detect the condition that prompts the braking of the electric motor, set a braking profile for braking the electric motor based on the detected condition, and execute braking of the electric motor using the braking profile.

2 . The power tool of claim 1 , wherein the control unit is configured to execute braking of the electric motor using a first braking profile when detecting a first condition, and using a second braking profile when detecting a second condition, wherein the first braking profile is configured to stop the rotation of the motor faster than the second braking profile

3 . The power tool of claim 2 , wherein the first condition is a pinch condition, and the second condition is a motor stop or fault condition.

4 . The power tool of claim 2 , wherein the first profile comprises a hard braking profile wherein the control unit activates the three high-side switches or the three low-side switches simultaneously to apply braking force to the motor throughout substantially the entire length of the braking.

5 . The power tool of claim 4 , wherein in the execution of hard braking profile, the control unit activates the high-side switches within a first braking period and low-side switches within a second braking period, and introduces a small delay period between the first and second braking periods.

6 . The power tool of claim 2 , wherein the second profile comprises a soft braking profile wherein, during a braking cycle, the control unit activates the three high-side switches or the three low-side switches simultaneously during a braking period, and deactivates all the plurality of power switches during a coasting period following the braking period.

7 . The power tool of claim 6 , wherein a duty cycle of the braking period within the braking cycle is less than or equal to 95%.

8 . The power tool of claim 6 , wherein the control unit is configured detect a rotational speed of the motor and set a duty cycle of the braking period within the braking cycle as a function of the rotational speed of the motor.

9 . The power tool of claim 1 , wherein the braking profile comprises a first braking segment followed by a second braking segment.

10 . The power tool of claim 9 , wherein the control unit executed hard braking to apply a first braking force to the motor during the first braking segment, and executes soft braking to apply to a second braking force to the motor during the second braking segment, wherein the second braking force is less than the first braking force.

11 . The power tool of claim 10 , wherein the control unit is configured to monitor a rotational speed of the motor and switch from the first braking segment to the second braking segment when the rotational speed of the motor falls below a predetermined threshold speed.

12 . The power tool of claim 9 , wherein the control unit executed soft braking to apply a first braking force to the motor during the first braking segment, and executes hard braking to apply to a second braking force to the motor during the second braking segment, wherein the first braking force is less than the second braking force.

13 . A power tool comprising:
a housing; a brushless direct-current (BLDC) electric motor disposed inside the housing; a plurality of power switches disposed between a power supply and the electric motor, the plurality of power switches including a plurality of high-side switches and a plurality of low-side switches; and a control unit configured to control a switching operation of the plurality of power switches to operate the electric motor and electronically brake the motor by simultaneously activating the plurality of the high-side switches or the plurality of low-side switches to stop the rotation of the motor upon detection of a condition prompting the braking of the motor, wherein the control unit is configured to execute hard braking having a first braking force on the motor within a first braking segment, and apply soft braking having a second braking force on the motor within a second braking segment, wherein the first braking force is greater than the second braking force.

14 . The power tool of claim 13 , wherein when executing soft braking, during a braking cycle, the control unit activates the three high-side switches or the three low-side switches simultaneously during a braking period, and deactivates all the plurality of power switches during a coasting period following the braking period.

15 . A power tool comprising:
a housing; a brushless direct-current (BLDC) electric motor disposed inside the housing; a plurality of power switches disposed between a power supply and the electric motor, the plurality of power switches including a plurality of high-side switches and a plurality of low-side switches; and a control unit configured to control a switching operation of the plurality of power switches to operate the electric motor, wherein the control unit is configured to: allow the electric motor to coast by deactivating the plurality of power switches, monitor voltage across a bus line between the power supply and the plurality of power switches, and execute weak motoring of the electric motor if the voltage across the bus line exceeds an upper voltage threshold until the voltage across the bus line is at a nominal value.

Assignees

• Black & Decker Inc

Inventors

• Vanko John C
• Coates Marcell E
• Nace Daniel F
• Velderman Matthew J
• Kelly Sean M
• Goble James E

Classifications

• H02P6/24

  Arrangements for stopping · CPC title

• H02K7/145

  Hand-held machine tool · CPC title

• B24B23/028

  Angle tools · CPC title

• F16P7/02 Primary

  by causing the machine to stop on the occurrence of dangerous conditions therein (devices in bearings affected by abnormal conditions F16C) · CPC title

• H02P29/0241

  the fault being an overvoltage · CPC title