ELECTRIC TOOL

• US 20200130127A1
• Filed: 10/27/2017
• Published: 04/30/2020
• Est. Priority Date: 11/30/2016
• Status: Active Grant

• Current Assignee: Koki Holdings Co., Ltd.
• Original Assignee: Koki Holdings Co., Ltd.
• Inventors: YOSHINARI, Takuya, IWATA, Kazutaka
• Granted Patent: US 11,511,387 B2
• Time in Patent Office: Days
• CPC Class Codes: B24B 23/02 with rotating grinding tools; Accessories therefor
• 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 27/08 with pulse width modulation
• CPC Class Codes: H02P 3/22 by short-circuit or resistive braking
• CPC Class Codes: H02P 6/17 and for generating speed information
• CPC Class Codes: H02P 6/24 Arrangements for stopping

Abstract

An electric tool capable of achieving inhibition of reaction due to braking in good balance with inhibition of voltage jumping due to regenerated energy is provided. A grinder (1) is provided with a motor (6), an inverter circuit (43) for supplying electric current to the motor (6), and a controller (50) for controlling the inverter circuit (43). When generating an electric braking force on a motor (6), the rotation speed of which exceeds a specified rotation speed, the controller (50) performs a first braking control of continuously turning on lower arm-side switching elements (Q4-Q6) of the inverter circuit (43), after which the controller performs a second braking control of repeatedly turning on and off the lower arm-side switching elements (Q4-Q6).

Claims

1. An electric tool, comprising:

a motor;

an inverter circuit supplying an electric current to the motor and having a plurality of switching elements; and

a controller controlling the inverter circuit,

wherein when generating an electric braking force on the motor, the controller performs a first braking control of turning on at least one of the plurality of switching elements of the inverter circuit and then performs a second braking control of repeatedly turning on and off the at least one of the plurality of switching elements.

2. The electric tool according to claim 1, wherein the controller switches from the first braking control to the second braking control when a rotation speed of the motor becomes equal to or less than a predetermined rotation speed in a braking control.

3. The electric tool according to claim 2, comprising:

a rotation tool driven by the motor,

wherein the controller sets the predetermined rotation speed according to an inertia moment of the rotation tool.

4. The electric tool according to claim 3, wherein the controller determines the inertia moment of the rotation tool based on a time change rate of a rotation speed during acceleration or deceleration of the motor or a starting current of the motor.

5. The electric tool according to claim 1, wherein the controller turns on at least one of upper arm-side switching elements of the plurality of switching elements or at least one of lower arm-side switching elements of the plurality of switching elements of the inverter circuit in the first braking control.

6. The electric tool according to claim 1, wherein the controller sets a duty ratio of an on period of the at least one of the plurality of switching elements constant in the second braking control.

7. The electric tool according to claim 1, wherein the controller sets a duty ratio of an on period of at least one of the plurality of switching elements variable in the second braking control.

8. The electric tool according to claim 7, wherein the controller gradually increases the duty ratio in the second braking control.

9. The electric tool according to claim 1, comprising:

a capacitor provided on an input side of the inverter circuit,

wherein the controller performs the second braking control so that a voltage applied to the capacitor by a regenerated energy does not exceed a withstand voltage of the capacitor.

12. The electric tool according to claim 1, comprising:

an operation switch switching between driving and stopping the motor,

wherein the controller generates the electric braking force on the motor when the operation switch enters a state of instructing the motor to stop.

13. The electric tool according to claim 1, wherein the electric tool operates with an AC power supplied from outside.

10. (canceled)

11. (canceled)

14. An electric tool, comprising:

a motor;

an inverter circuit supplying an electric current to the motor; and

a controller controlling the inverter circuit,

wherein when generating an electric braking force on the motor, the controller performs a first braking control in which a pulse width modulation control is not performed to the inverter circuit, and when a rotation speed of the motor becomes equal to or less than a predetermined rotation speed, the controller performs a second braking control in which the pulse width modulation control is performed.

15. The electric tool according to claim 14, comprising:

a rotation tool driven by the motor,

wherein the controller sets the predetermined rotation speed according to an inertia moment of the rotation tool.