POWER TOOL

• US 20150171654A1
• Filed: 08/29/2013
• Published: 06/18/2015
• Est. Priority Date: 08/30/2012
• Status: Active Grant

• Current Assignee: Koki Holdings Co., Ltd.
• Original Assignee: Hitachi KOKI Company Limited (Koki Holdings Co., Ltd.)
• Inventors: Horie, Yuki, Funabashi, Kazuhiko, Takano, Nobuhiro
• Granted Patent: US 10,320,214 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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

Abstract

A power tool includes: a secondary battery; a drive unit; a detecting unit; and a control unit. The secondary battery has positive and negative terminals across which a battery voltage is developed. The drive unit is connected to the secondary battery. The detecting unit is configured to detect a current value and a voltage value supplied from the secondary battery to the drive unit. The control unit is configured to control an effective voltage and an effective current applied to the drive unit depending on a load imposed thereon to fall within an allowable power dissipation value.

Claims

1. A power tool comprising:

a secondary battery having positive and negative terminals across which a battery voltage is developed;

a drive unit connected to the secondary battery;

a detecting unit configured to detect a current value and a voltage value supplied from the secondary battery to the drive unit; and

a control unit configured to control an effective voltage and an effective current applied to the drive unit depending on a load imposed thereon to fall within an allowable power dissipation value.

2. The power tool according to claim 1, wherein the control unit executes either one of a first control and a second control, wherein the first control continuously applies the battery voltage to the drive unit, and the second control converts the battery voltage, the converted battery voltage having an effective voltage different from the battery voltage, at least one converted battery voltage being applied to the drive unit.

3. The power tool according to claim 1, wherein the battery voltage is different from a rated voltage of the drive unit.

4. The power tool according to claim 1, further comprising a current interrupting unit configured to interrupt current flowing to the drive unit in response to an alert signal alerting that the secondary battery has an error.

5. The power tool according to claim 4, wherein the alert signal alerts that the secondary battery is about to become at least one of an over-discharge state, an over-current state in which overcurrent flows from the secondary battery, and a high-temperature state in which a temperature of the secondary battery exceeds a prescribed limit temperature.

6. The power tool according to claim 1, wherein the control unit is further configured to change current from the secondary battery into different values step-by-step depending on the battery voltage by outputting a square-wave signal of prescribed frequency as a chopping control signal and varying a duty cycle of the chopping control signal.

7. The power tool according to claim 6, further comprising a current interrupting unit configured to interrupt current flowing to the drive unit in response to an alert signal alerting that the secondary battery has an error, wherein the control unit is further configured to change the current from the secondary battery by turning the current interrupting unit on and off in response to the chopping control signal.

8. The power tool according to claim 1, wherein the secondary battery comprises a lithium-ion battery cell.