Kickback control methods for power tools

Patent metadata

Field	Value
Publication number	US-10981267-B2
Application number	US-201816170836-A
Country	US
Kind code	B2
Filing date	Oct 25, 2018
Priority date	Oct 26, 2017
Publication date	Apr 20, 2021
Grant date	Apr 20, 2021

Abstract

Kickback control methods for power tools. One power tool includes a movement sensor configured to measure an angular velocity of the housing of the power tool about the rotational axis. The power tool includes an electronic processor coupled to the switching network and the movement sensor and configured to implement kickback control of the power tool. To implement the kickback control, the electronic processor is configured to control the switching network to drive the brushless DC motor, receive measurements of the angular velocity of the housing of the power tool from the movement sensor, determine that a plurality of the measurements of the angular velocity of the housing of the power tool exceed a rotation speed threshold, and control the switching network to cease driving of the brushless DC motor in response to determining that the plurality of the measurements of the angular velocity exceed the rotation speed threshold.

First claim

We claim:

1. A power tool comprising:
a housing having a motor housing portion, a handle portion, and a battery interface;
a brushless direct current (DC) motor within the motor housing portion and having a rotor and a stator, wherein the rotor is configured to rotationally drive a motor shaft about a rotational axis;
a switching network electrically coupled to the brushless DC motor;
a movement sensor configured to measure an angular velocity of the housing of the power tool about the rotational axis;
an orientation sensor configured to measure an orientation of the power tool with respect to gravity; and
an electronic processor coupled to the switching network, the orientation sensor, and the movement sensor and configured to implement kickback control of the power tool, wherein, to implement the kickback control, the electronic processor is configured to:
control the switching network to drive the brushless DC motor,
receive measurements of the angular velocity of the housing of the power tool from the movement sensor,
determine that a plurality of the measurements of the angular velocity of the housing of the power tool exceed a rotation speed threshold, and
control the switching network to cease driving of the brushless DC motor in response to determining that the plurality of the measurements of the angular velocity exceed the rotation speed threshold,
determine an initial orientation of the power tool based on information received from the orientation sensor,
determine the rotation speed threshold based on the initial orientation of the power tool,
determine a second orientation of the power tool based on information received from the orientation sensor that indicates that the orientation of the power tool has changed from the initial orientation, and
determine an adjusted value for the rotation speed threshold based on the second orientation of the power tool.

2. The power tool of claim 1 , wherein the electronic processor is configured to:
receive the measurements of the angular velocity of the housing of the power tool from the movement sensor at predetermined time intervals; and
determine that the plurality of measurements of the angular velocity of the housing of the power tool within a predetermined time period exceed the rotation speed threshold.

3. The power tool of claim 1 , wherein the electronic processor is configured to:
determine whether each measurement of the angular velocity exceeds the rotation speed threshold;
increment a counter for each measurement of the angular velocity that is determined to exceed the rotation speed threshold;
determine that the counter exceeds a counter threshold; and
control the switching network to cease driving of the brushless DC motor in response to determining that the counter exceeds the counter threshold.

4. The power tool of claim 3 , wherein the electronic processor is configured to:
determine that the counter is greater than zero; and
decrement the counter for each measurement of the angular velocity that is determined to be below the rotation speed threshold.

5. The power tool of claim 3 , further comprising a transceiver electrically coupled to the electronic processor and configured to communicate with an external device;
wherein the electronic processor is configured to receive, via the transceiver, at least one of the group consisting of the rotation speed threshold and the counter threshold from the external device, wherein a value of the at least one of the group consisting of the rotation speed threshold and the counter threshold is selected via a user input on the external device.

6. The power tool of claim 1 , further comprising a transceiver electrically coupled to the electronic processor and configured to communicate with an external device;
wherein the electronic processor is configured to receive, via the transceiver, an instruction indicating whether to implement the kickback control of the power tool, wherein the instruction is generated based on a user input on the external device.

7. The power tool of claim 1 , further comprising a trigger configured to be actuated to cause the power tool to drive the brushless DC motor;
wherein the electronic processor is further configured to
determine a position of the trigger based on an amount of actuation of the trigger,
control the switching network to drive the brushless DC motor in proportion with the position of the trigger,
determine that the position of the trigger has changed and indicates that the trigger is being released but remains partially actuated, and
in response to determining that the position of the trigger has changed and indicates that the trigger is being released but remains partially actuated, implement an exaggerated release of the trigger by controlling the switching network to cease driving of the brushless DC motor.

8. A power tool comprising:
a housing having a motor housing portion, a handle portion, and a battery interface;
a brushless direct current (DC) motor within the motor housing portion and having a rotor and a stator, wherein the rotor is configured to rotationally drive a motor shaft about a rotational axis;
a switching network electrically coupled to the brushless DC motor;
a movement sensor configured to measure an angular velocity of the housing of the power tool about the rotational axis;
an orientation sensor configured to measure an orientation of the power tool with respect to gravity; and
an electronic processor coupled to the switching network, the orientation sensor, and the movement sensor and configured to implement kickback control of the power tool, wherein, to implement the kickback control, the electronic processor is configured to:
control the switching network to drive the brushless DC motor,
receive measurements of the angular velocity of the housing of the power tool from the movement sensor, and
control the switching network to cease driving of the brushless DC motor in response to determining that a measurement of the measurements of the angular velocity exceeds a rotation speed threshold and determining that a power tool characteristic exceeds a kickback threshold,
determine an initial orientation of the power tool based on information received from the orientation sensor,
determine at least one of the rotation speed threshold and the kickback threshold based on the initial orientation of the power tool,
determine a second orientation of the power tool on information received from the orientation sensor that indicates that the orientation of the power tool has changed from the initial orientation, and
determine an adjusted value for the at least one of the rotation speed threshold and the kickback threshold based on the second orientation of the power tool.

9. The power tool of claim 8 , wherein the power tool characteristic is a second measurement of the measurements of the angular velocity of the housing of the power tool from the movement sensor and the kickback threshold is the rotation speed threshold.

10. The power tool of claim 8 ,
wherein the power tool characteristic is at least one of the group consisting of a motor current, a roll position of the power tool, and a position of a trigger of the power tool, and
wherein at least one selected from the group of the rotation speed threshold and the kickback threshold is based on a direction of rotation of the brushless DC motor.

11. The power tool of claim 8 , wherein the electronic processor is configured to:
receive the measurements of the angular velocity of the housing of the power tool from the movement sensor at predetermined time intervals; and
determine that the measurement of the angular

Assignees

• Milwaukee Electric Tool Corp

Inventors

• Abbott Jonathan E
• Obermann Timothy R
• Dey Iv John S
• Suhr Benjamin R
• Ryer Richard A
• Merget Maxwell L
• Fieldbinder Douglas R

Classifications

• B25D16/00 Primary

  Portable percussive machines with superimposed rotation {, the rotational movement of the output shaft of a motor being modified to generate axial impacts on the tool bit (combined percussion and rotary drilling adapted for earth drilling E21B6/00)} · CPC title

• B25F5/00

  Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for · CPC title

• H02K7/145

  Hand-held machine tool · CPC title

• B25D2250/201

  for speed, e.g. drilling or percussion speed · CPC title

• H02K7/003

  Couplings; Details of shafts (means for mounting rotors on shafts H02K1/28) · CPC title