Electric work machine

Patent metadata

Field	Value
Publication number	US-2021069886-A1
Application number	US-202017014012-A
Country	US
Kind code	A1
Filing date	Sep 8, 2020
Priority date	Sep 9, 2019
Publication date	Mar 11, 2021
Grant date	—

Abstract

An electric work machine ( 1; 110; 120; 130 ), such as a power tool, includes a motor ( 11 ) having a rotor, a drive part ( 13 ) that supplies electric currents to drive the motor, a rotational-direction selection part ( 17 ), and a motor-control part ( 14; 31, 32, 40, 50, 60; 14, 40, 60, 73, 80; 14, 60, 91 ). The rotational-direction selection part is configured for manually setting (selecting) the rotational direction of the rotor and outputs first and second setting signals that each indicate the set (selected) rotational direction. The motor-control part controls the drive part such that the rotor rotates in the rotational direction indicated by the first setting signal and/or the second setting signal. In response to a determination that the rotational directions indicated by the first and second setting signals are inconsistent, the motor-control part stops or prevents the drive of the motor.

First claim

1 . An electric work machine comprising:
a motor having a rotor; a drive part configured to drive the motor using electric power supplied from a power supply; a rotational-direction selection part configured to be manipulated by a user to selectively set a rotational direction of the rotor to either a first rotational direction or a second rotational direction and to output a first setting signal and a second setting signal that both indicate the set rotational direction; and a motor-control part configured to control the drive part such that the rotor rotates in the rotational direction indicated by the first setting signal and/or the second setting signal, which have been output from the rotational-direction selection part, and to stop or prevent rotation of the rotor in response to a determination that the rotational direction indicated by the first setting signal and the rotational direction indicated by the second setting signal are inconsistent.

2 . The electric work machine according to claim 1 , wherein the motor-control part is configured to:
receive the first setting signal and the second setting signal that were output from the rotational-direction selection part, control the drive part such that the rotor rotates in the rotational direction indicated by the received first setting signal and/or the received second setting signal, and control the drive part such that the rotation of the rotor is stopped or prevented in response to a determination that the rotational direction indicated by the first setting signal and the rotational direction indicated by the second setting signal are inconsistent.

3 . The electric work machine according to claim 1 , wherein the motor-control part comprises:
a control circuit configured to receive the first setting signal output from the rotational-direction selection part and to control the drive part such that the rotor rotates in the rotational direction indicated by the first setting signal; a determination circuit configured to receive the second setting signal output from the rotation-direction selection part and to determine whether the rotational direction indicated by the second setting signal and an actual rotating direction of the rotor are consistent; and a stop circuit configured to stop or prevent the rotation of the rotor in response to a determination by the determination circuit that there is an inconsistency between the rotational direction indicated by the second setting signal and the actual rotating direction of the rotor.

4 . The electric work machine according to claim 3 , wherein the control circuit is further configured to receive the second setting signal output from the rotational-direction selection part and to control the drive part such that rotation of the rotor is stopped or prevented in response to a determination that the rotational direction indicated by the first setting signal and the rotational direction indicated by the second setting signal are inconsistent.

5 . The electric work machine according to claim 3 , wherein the determination circuit comprises:
a rotational-direction detection circuit configured to detect the actual rotating direction of the rotor; and a determination-execution circuit configured to determine whether the rotational direction indicated by the second setting signal received by the determination circuit and the actual rotating direction detected by the rotational-direction detection circuit are consistent.

6 . The electric work machine according to claim 5 , further comprising:
a position-information output part configured to output rotational-position information corresponding to a rotational position of the rotor; wherein the rotational-direction detection circuit is configured to detect the actual rotational direction based on the rotational-position information output from the position-information output part.

7 . The electric work machine according to claim 5 , wherein:
the control circuit is configured to control the drive part by outputting a drive instruction to the drive part; and the rotational-direction detection circuit is configured to receive the drive instruction, which is supplied by the control circuit to the drive part, and to detect the actual rotating direction of the rotor based on the drive instruction.

8 . The electric work machine according to claim 3 , wherein the motor-control part further comprises:
a rotation-detection circuit configured to detect whether or not the rotor is rotating; and a disabling circuit configured to disable a function that, while rotation of the rotor is not being detected, stops the rotation of the rotor using the stop circuit.

9 . The electric work machine according to claim 8 , further comprising:
a position-information output part configured to output rotational-position information corresponding to the rotational position of the rotor; wherein the rotation-detection circuit is configured to detect, based on the rotational-position information output from the position-information output part, whether or not the rotor is rotating.

10 . The electric work machine according to claim 8 , wherein:
the control circuit is configured to control the drive part by outputting a drive instruction to the drive part; and the rotation-detection circuit is configured to input the drive instruction, which is supplied by the control circuit to the drive part, and to detect, based on the drive instruction, whether or not the rotor is rotating.

11 . The electric work machine according to claim 7 , wherein:
the drive part comprises six switching devices, which include a first switching device and a second switching device; the drive instruction includes six drive signals, which are respectively input to the six switching devices and which include a first drive signal input to the first switching device and a second drive signal input to the second switching device; the control circuit is configured to generate three-phase electric power to drive the motor by turning ON each of the six switching devices using the six drive signals during an energization interval for each of the six switching devices that starts from an energization-start time until the rotor rotates by an energization electric angle, wherein the energization-start times respectively correspond to the rotational position of the rotor, and the energization-start times for the six switching devices are phase-shifted from one another by a fixed electric angle; and the rotational-direction detection circuit is configured to detect the actual rotating direction of the rotor based on the first drive signal and the second drive signal.

12 . The electric work machine according to claim 11 , wherein:
the control circuit is configured to generate the three-phase electric power by controlling the ON time of each of the six switching devices during each of the energization intervals using a pulse-width-modulation method, in which each of the six drive signals includes instructions for periodically switching ON and OFF each of the six switching devices at a switching frequency; the electric work machine further comprises:
a first low-pass filter configured to receive the first drive signal, to attenuate signal components, which are contained in the first drive signal, having a frequency higher than a first cutoff frequency and to output a filtered first drive signal containing signal components below the first cutoff frequency; and
a second low-pass filter configured to receive the second drive signal, to attenuate signal components, which are contained in the second drive signal, having a frequency higher than a second cutoff frequency and to

Assignees

• Makita Corp

Inventors

• Suzuki Hitoshi
• Hayashi Seitaro
• Omura Motohiro
• Kato Itsuku

Classifications

• H02H7/097 Primary

  against wrong direction of rotation · CPC title

• H02P23/24

  Controlling the direction, e.g. clockwise or counterclockwise · CPC title

• H02P3/18

  for stopping or slowing an AC motor · CPC title

• H01H1/22

  with rigid pivoted member carrying the moving contact · CPC title

• B25F5/00 Primary

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