Electric working machine and method for braking three-phase brushless motor of electric working machine

• US 10,326,385 B2
• Filed: 05/30/2018
• Issued: 06/18/2019
• Est. Priority Date: 06/15/2017
• Status: Active Grant

• Current Assignee: Makita Corporation
• Original Assignee: Makita Corporation
• Inventors: Ichikawa, Yoshitaka
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US15/992,530
• Publication Number:
  US 20180367070A1
• Time in Patent Office: 384 Days
• Field of Search: None
• CPC Class Codes: B24B 23/028 Angle tools
• CPC Class Codes: B24B 47/12 by mechanical gearing or electric power B24B47/16 takes precedence
• CPC Class Codes: B25F 5/00 Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
• CPC Class Codes: H02P 3/12 by short-circuit or resistive braking
• CPC Class Codes: H02P 3/22 by short-circuit or resistive braking

Abstract

In one aspect of the present disclosure, an electric working machine includes a three-phase brushless motor, a first switching element, a second switching element, a third switching element, a fourth switching element, a fifth switching element, a sixth switching element, a rotation detector, a brake controller. The brake controller executes a two-phase short-circuit brake. The two-phase short-circuit brake is executed so as to switch any of the fourth switching element, the fifth switching element, and the sixth switching element to a corresponding ON-state or an OFF-state in response a detection signal from the rotation detector that occurs prior to a switching time.

Claims

1. An electric working machine, comprising:

a tool;

a three-phase brushless motor including a first terminal, a second terminal, and a third terminal and configured to generate a driving force for driving the tool;

a first high-side switch provided between the first terminal and a positive electrode of a direct-current power source, the first high-side switch being configured to electrically couple the first terminal to the positive electrode in an ON-state, and the first high-side switch being configured to electrically decouple the first terminal from the positive electrode in an OFF-state;

a second high-side switch provided between the second terminal and the positive electrode, the second high-side switch being configured to electrically coupled the second terminal to the positive electrode in an ON-state, and the second high-side switch being configured to electrically decouple the second terminal from the positive electrode in an OFF-state;

a third high-side switch provided between the third terminal and the positive electrode, the third high-side switch being configured to electrically couple the third terminal to the positive electrode in a ON-state, and the third high-side switch being configured to electrically decouple the third terminal from the positive electrode in an OFF-state;

a first low-side switch provided between the first terminal and a negative electrode of the direct-current power source, the first low-side switch being configured to electrically couple the first terminal to the negative electrode in an ON-state, and the first low-side switch being configured to electrically decouple the first terminal from the negative electrode in an OFF-state;

a second low-side switch provided between the second terminal and the negative electrode, the second low-side switch being configured to electrically couple the second terminal to the negative electrode in an ON-state, and the second low-side switch being configured to electrically decouple the second terminal from the negative electrode in an OFF-state;

a third low-side switch provided between the third terminal and the negative electrode, the third low-side switch being configured to electrically couple the third terminal to the negative electrode in an ON-state, and the third low-side switch being configured to electrically decouple the third terminal from the negative electrode in an OFF-state;

a rotation detector configured to generate a detection signal that indicates a rotation position of the three-phase brushless motor every time the three-phase brushless motor rotates by a specific angle; and

a control circuit configured to execute a signal interruption process and a timer interruption process,

wherein the control circuit is configured to execute the signal interruption process in response to occurrence of the detection signal,

wherein the signal interruption process includes;

executing a brake control process in response to a soft brake process requirement being set, the soft brake process requirement requesting execution of a two-phase short-circuit brake;

calculating a delay time based on an elapsed time since the signal interruption process is previously executed and a delay angle; and

setting the delay time calculated in a timer to start measurement of the delay time by the timer,

wherein the control circuit is further configured to execute the timer interruption process in response to elapse of the delay time,

wherein the timer interruption process includes;

executing the brake control process in response to the soft brake process requirement being set; and

clearing the soft brake process requirement in response to completion of the brake control process, and

wherein the brake control process includes;

setting the first high-side switch, the second high-side switch, and the third high-side switch to the respective OFF-states; and

switching any one of the first low-side switch, the second low-side switch, and the third low-side switch to the corresponding ON-state or the OFF-state in accordance with the rotation position of the three-phase brushless motor so as to place any two of the first low-side switch, the second low-side switch, and the third low-side switch to the respective ON-states and to place any remaining low-side switch of the first low-side switch, the second low-side switch, and the third low-side switch in the corresponding OFF-state.

2. An electric working machine, comprising:

a three-phase brushless motor including a first terminal, a second terminal, and a third terminal;

a first switching element provided between the first terminal and a first electrode of a direct-current power source, the first switching element being configured to electrically couple the first terminal to the first electrode in an ON-state, and the first switching element being configured to electrically decouple the first terminal from the first electrode in an OFF-state;

a second switching element provided between the second terminal and the first electrode, the second switching element being configured to electrically couple the second terminal to the first electrode in an ON-state, and the second switching element being configured to electrically decouple the second terminal from the first electrode in an OFF-state;

a third switching element provided between the third terminal and the first electrode, the third switching element being configured to electrically couple the third terminal to the first electrode in an ON-state, and the third switching element being configured to electrically decouple the third terminal from the first electrode in an OFF-state;

a fourth switching element provided between the first terminal and a second electrode of the direct-current power source, the fourth switching element being configured to electrically couple the first terminal to the second electrode in an ON-state, and the fourth switching element being configured to electrically decouple the first terminal from the second electrode in an OFF-state;

a fifth switching element provided between the second terminal and the second electrode, the fifth switching element being configured to electrically couple the second terminal to the second electrode in an ON-state, and the fifth switching element being configured to electrically decouple the second terminal from the second electrode in an OFF-state;

a sixth switching element provided between the third terminal and the second electrode, the sixth switching element being configured to electrically couple the third terminal to the second electrode in an ON-state, and the sixth switching element being configured to electrically decouple the third terminal from the second electrode in an OFF-state;

a rotation detector configured to generate a detection signal that indicates a rotation position of the three-phase brushless motor every time the three-phase brushless motor rotates by a specific angle; and

a brake controller configured to execute a two-phase short-circuit brake,

wherein the two-phase short-circuit brake is executed so as to set the first switching element, the second switching element, and the third switching element to the respective OFF-states and to switch any of the fourth switching element, the fifth switching element, and the sixth switching element to the corresponding ON-state or the OFF-state in accordance with a switching time that is based on the detection signal, and

wherein the two-phase short-circuit brake is further executed so as to switch any of the fourth switching element, the fifth switching element, and the sixth switching element to the corresponding ON-state or the OFF-state in response to the detection signal that occurs prior to the switching time.

3. The electric working machine according to claim 2, further comprising a timer that is configured to measure a time,

wherein the brake controller includes a timer setter that is configured to set in the timer a delay time until arrival of the switching time based on the detection signal and to start measurement for the delay time by the timer.

4. The electric working machine according to claim 3,

wherein the brake controller includes a switching controller that is configured to switch the any of the fourth switching element, the fifth switching element, and the sixth switching element to the corresponding ON-state or the OFF-state in response to completion of the measurement for the delay time by the timer.

5. The electric working machine according to claim 4,

wherein the timer setter is configured to switch, in place of the switching controller, the any of the fourth switching element, the fifth switching element, and the sixth switching element to the corresponding ON-state or the OFF-state in response to the delay time being newly set in the timer based on the detection signal before elapse of the delay time that is previously set in the timer.

6. The electric working machine according to claim 3,

wherein the timer setter is configured to switch, in response to the delay time being newly set in the timer based on the detection signal before elapse of the delay time that is previously set in the timer, the any of the fourth switching element, the fifth switching element, and the sixth switching element to the corresponding ON-state or the OFF-state within a specific time after the rotation position of the three-phase brushless motor reaches a specific rotation position that is acquired based on the detection signal.

7. The electric working machine according to claim 3,

wherein the timer setter is configured to switch, in response to the delay time being newly set in the timer based on the detection signal before elapse of the delay time that is previously set in the timer, the any of the fourth switching element, the fifth switching element, and the sixth switching element to the corresponding ON-state or the OFF-state immediately after the rotation position of the three-phase brushless motor reaches a specific rotation position that is acquired based on the detection signal.

8. The electric working machine according to claim 2,

wherein the first electrode corresponds to a positive electrode of the direct-current power source, and

wherein the second electrode corresponds to a negative electrode of the direct-current power source.

9. The electric working machine according to claim 2,

wherein the first electrode corresponds to a negative electrode of the direct-current power source, and

wherein the second electrode corresponds to a positive electrode of the direct-current power source.

10. The electric working machine according to claim 2,

wherein the brake controller is configured to execute the two-phase short-circuit brake in response to establishment of a brake condition during the three-phase brushless motor rotating.

11. A method for braking a three-phase brushless motor of an electric working machine, the method comprising:

generating a detection signal that indicates a rotation position of the three-phase brushless motor every time the three-phase brushless motor rotates by a specific angle;

setting a first switching element, a second switching element, and a third switching element to respective OFF-states in response to establishment of a brake condition during the three-phase brushless motor rotating, the first switching element being provided between a first terminal of the three-phase brushless motor and a first electrode of a direct-current power source, the first switching element being configured to electrically couple the first terminal to the first electrode in an ON-state, the first switching element being configured to electrically decouple the first terminal from the first electrode in the OFF-state, the second switching element being provided between a second terminal of the three-phase brushless motor and the first electrode, the second switching element being configured to electrically couple the second terminal to the first electrode in an ON-state, the second switching element being configured to electrically decouple the second terminal from the first electrode in the OFF-state, the third switching element being provided between a third terminal of the three-phase brushless motor and the first electrode, the third switching element being configured to electrically couple the third terminal to the first electrode in an ON-state, and the third switching element being configured to electrically decouple the third terminal from the first electrode in the OFF-state;

switching any of a fourth switching element, a fifth switching element, and a sixth switching element to a corresponding ON-state or an OFF-state in accordance with a switching time that is based on the detection signal in response to the establishment of the brake condition during the three-phase brushless motor rotating, the fourth switching element being provided between the first terminal and a second electrode of the direct-current power source, the fourth switching element being configured to electrically couple the first terminal to the second electrode in the ON-state, the fourth switching element being configured to electrically decouple the first terminal from the second electrode in the OFF-state, the fifth switching element being provided between the second terminal and the second electrode, the fifth switching element being configured to electrically couple the second terminal to the second electrode in the ON-state, the fifth switching element being configured to electrically decouple the second terminal from the second electrode in the OFF-state, the sixth switching element being provided between the third terminal and the second electrode, the sixth switching element being configured to electrically couple the third terminal to the second electrode in the ON-state, and the sixth switching element being configured to electrically decouple the third terminal from the second electrode in the OFF-state; and

switching the any of the fourth switching element, the fifth switching element, and the sixth switching element to the corresponding ON-state or the OFF-state in response to the detection signal that occurs prior to the switching time.