Electric working machine

• US 10,541,636 B2
• Filed: 04/11/2017
• Issued: 01/21/2020
• Est. Priority Date: 04/18/2016
• Status: Active Grant

• Current Assignee: Makita Corporation
• Original Assignee: Makita Corporation
• Inventors: Nakamoto, Akihiro, Kato, Itsuku, Kawai, Yuki
• Primary Examiner(s): Islam, Muhammad S
• Application Number:
  US15/484,479
• Publication Number:
  US 20170302211A1
• Time in Patent Office: 1,015 Days
• Field of Search: 318751, 318794, 318817, 318629, 318812, 318504, 318 8, 318654
• CPC Class Codes: B23D 45/16 Hand-held sawing devices with circular saw blades
• CPC Class Codes: B23D 47/12 of drives for circular saw blades
• CPC Class Codes: B23D 59/001 Measuring or control devices, e.g. for automatic control of work feed pressure on band saw blade measuring in general G01; controlling in general G05
• CPC Class Codes: B27B 9/00 Portable power-driven circular saws for manual operation details or components, e.g. handles, casings, of portable power-driven tools not particularly related to the operation performed B25F5/00
• CPC Class Codes: H02M 1/083 for the ignition at the zero crossing of the voltage or the current
• CPC Class Codes: H02M 1/322 Means for rapidly discharging a capacitor of the converter for protecting electrical components or for preventing electrical shock
• CPC Class Codes: H02M 7/06 using discharge tubes without control electrode or semiconductor devices without control electrode
• CPC Class Codes: H02P 2201/03 AC-DC converter stage controlled to provide a defined DC link voltage general aspects of plural converters in cascade H02M
• CPC Class Codes: H02P 2207/05 Synchronous machines, e.g. with permanent magnets or DC excitation
• CPC Class Codes: H02P 27/06 using dc to ac converters or inverters H02P27/05 takes precedence
• CPC Class Codes: H02P 3/18 for stopping or slowing an ac motor
• CPC Class Codes: H02P 3/22 by short-circuit or resistive braking

Abstract

An electric working machine of an example of the present disclosure includes: a motor; a power supply portion; a controller; and a voltage detector. The power supply portion generates a DC voltage to drive the motor by rectifying an AC voltage supplied from an AC power source and smoothing by a capacitor. The controller controls energization of the motor. The voltage detector detects the AC voltage. The controller is configured to interrupt the energization when the voltage detector does not detect the AC voltage.

Claims

1. An electric working machine comprising:

a motor;

a power supply portion to generate a DC voltage to drive the motor by rectifying and smoothing an AC voltage supplied from an AC power source, wherein the power supply portion includes a capacitor for smoothing;

a controller that controls driving of the motor; and

a voltage detector that detects the AC voltage,

wherein the voltage detector is configured to detect a zero-cross point of the AC voltage, and

wherein the controller is configured to interrupt the driving of the motor so as to stop the motor when the controller determines that the zero-cross point of the AC voltage is not detected by the voltage detector while the motor is driven.

2. The electric working machine according to claim 1, further comprising:

a voltage generator that receives the DC voltage outputted from the power supply portion and generates a DC constant voltage to power the controller.

3. The electric working machine according to claim 1, further comprising:

a discharger that discharges an electric charge of the capacitor following a command of the controller,

wherein the controller is configured to output the command to the discharger and allows the discharger to discharge the electric charge of the capacitor when the voltage detector does not detect the AC voltage.

4. The electric working machine according to claim 1, wherein

the power supply portion includes a diode bridge that rectifies the full waves of the AC voltage inputted from the AC power source and the capacitor.

5. The electric working machine of claim 1, further comprising:

a fuse configured to receive, at a first end of the fuse, an alternating current (AC) associated with the AC voltage supplied from the AC power source;

a diode bridge connected to a second end of the fuse, and configured to rectify the AC voltage after passing through the fuse;

a slow discharge resistor connected directly in parallel with the capacitor, and configured to slowly discharge the capacitor;

a discharger including a fast discharge resistor in series with a discharge transistor, wherein the discharger is connected directly in parallel with the capacitor, and wherein the fast discharge resistor has a smaller resistance value than the slow discharge resistor;

a motor control circuit configured to control the motor;

an operation switch connecting a first node of the diode bridge to the motor control circuit;

a switch-detecting circuit configured to detect a position of the operation switch; and

a zero-cross detecting circuit configured to detect a zero-cross of the alternating voltage at the second end of the fuse.

6. The electric working machine according to claim 3, wherein the discharger includes a first resistor and a transistor, wherein the first resistor is in a series with the transistor, wherein the transistor is turned to an on state in response to a command from the controller, and wherein the series is in parallel with the capacitor.

7. The machine of claim 5, wherein the controller is configured to:

determine that a first zero cross is detected;

determine that the operation switch is ON; and

determine whether an initial elapsed time, after the first zero cross was detected, is greater than or equal to an initial set time.

8. The electric working machine according to claim 6, further comprising:

a second resistor connected to the capacitor in parallel,

wherein a resistance value of the first resistor is smaller than a resistance value of the second resistor.

9. The machine of claim 7, wherein the initial elapsed time is less than the initial set time, and wherein the controller is further configured to:

turn ON a re-start inhibition notice;

determine that the operation switch is OFF; and

cancel the re-start inhibition notice.

10. The machine of claim 7, wherein the initial elapsed time is greater than or equal to the initial set time, and wherein the controller is further configured to:

drive the motor;

determine that the operation switch is ON while the motor is driven;

determine that a driving zero-cross is not detected while the motor is driven;

stop the motor;

turn ON the discharger to discharge the capacitor; and

continue discharging the capacitor through the discharger until the operation switch is determined to be OFF.

11. The machine of claim 9, wherein the re-start inhibition notice is a light emitting diode (LED) in an ON state.

12. A machine comprising:

a fuse configured to receive an alternating current (AC) associated with an alternating voltage;

a diode bridge connected to a first end of the fuse and configured to rectify the alternating voltage;

a capacitor configured to smooth the rectified voltage;

a slow discharge resistor connected directly in parallel with the capacitor, and configured to slowly discharge the capacitor;

a discharger including a fast discharge resistor in series with a discharge transistor, wherein the discharger is connected directly in parallel with the capacitor, and wherein the fast discharge resistor has a smaller resistance value than the slow discharge resistor;

an operation switch connecting a first node of the diode bridge to a motor control circuit;

the motor control circuit configured to control a motor;

the motor;

a switch-detecting circuit configured to detect a position of the operation switch;

a zero-cross detecting circuit configured to detect a zero-cross of the alternating voltage at the first end of the fuse; and

a controller.

13. The machine of claim 12, wherein the controller is configured to:

determine that a first zero cross is detected;

determine that the operation switch is initially ON; and

determine whether an initial elapsed time, after the first zero cross was detected, is greater than or equal to an initial set time.

14. The machine of claim 13, wherein the initial elapsed time is greater than or equal to the initial set time, and wherein the controller is further configured to:

drive the motor;

determine that the operation switch is ON while the motor is driven;

determine that a driving zero-cross is not detected while the motor is driven;

stop the motor;

turn ON the discharger to discharge the capacitor; and

continue discharging the capacitor through the discharger until the operation switch is determined to be OFF.

15. The machine of claim 13, wherein the initial elapsed time is less than the initial set time, and wherein the controller is further configured to:

turn ON a re-start inhibition notice;

determine that the operation switch is OFF; and

cancel the re-start inhibition notice.

16. The machine of claim 15, wherein the re-start inhibition notice is a light emitting diode (LED) in an ON state.