Power tool

• US 7,932,697 B2
• Filed: 10/22/2010
• Issued: 04/26/2011
• Est. Priority Date: 09/07/2006
• Status: Active Grant

• Current Assignee: Koki Holdings Co., Ltd.
• Original Assignee: Hitachi KOKI Company Limited (Koki Holdings Co., Ltd.)
• Inventors: Nakayama, Eiji, Watanabe, Shinji, Funabashi, Kazuhiko
• Primary Examiner(s): Tso; Edward
• Assistant Examiner(s): PIGGUSH, AARON C
• Application Number:
  US12/910,291
• Publication Number:
  US 20110037435A1
• Time in Patent Office: 186 Days
• Field of Search: 320/112, 320/114, 320/136, 320/163
• US Class Current: 320/114
• CPC Class Codes: H01M 10/425 Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing printed circuits H05K1/00
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/448 End of discharge regulating measures
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A power tool 1 is connected to a battery pack 5 including an overcurrent detector 533 which detects overcurrent of a battery module 51 and outputs a detection signal, and an overdischarge detector 532 which detects overdischarge of the battery module 51 and outputs a detection signal. The power tool 1 includes a motor 2 which is driven by electric power supplied from the battery pack 5, a trigger switch 31 for setting the power supply from the battery pack 5 to the motor 2 in ON/OFF state, and an FET 410 which sets the power supply to the motor 2 in ON/OFF state on the basis of the detection signal from the overcurrent detector 533 or the overdischarge detector 532.

Claims

1. A power tool comprising:

a battery pack including at least one lithium-ion cell;

a motor driven by electric power supplied from the battery pack;

a current path connecting the motor and the lithium-cell, said current path including a first switch and a first FET;

a battery protection IC electrically connected to the current path, the battery protection IC outputting a first detection signal when the battery protection IC detects that the current in the current path exceeds a predetermined current value and a second detection signal when the battery protection IC detects that a voltage of the lithium-ion cell is lower than a predetermined voltage value;

said first switch being switchable between an ON state and OFF state depending on user operation;

said first FET being switchable from its ON state to its OFF state responsive to the first detection signal or the second detection signal, whereby the current flows in the current path, when the first switch and the first FET are both in their respective ON states; and

a second FET positioned outside of the current path, said second FET being connected to said first FET via a circuit, said second FET being operable, in response to an overcurrent or low voltage, to change its switching state, wherein when the current in the current path becomes lower than the predetermined current value, the first FET maintains its OFF state when the first switch is in its ON state after the first FET changes to its OFF state, and

wherein when the voltage of the lithium-ion cell becomes higher than the predetermined voltage, the first FET maintains its OFF state when the first switch is in its ON state after the first FET changes to its OFF state.

2. The power tool according to claim 1, wherein the battery pack comprises a plurality of lithium-ion cells.

3. The power tool according to claim 2, wherein the battery protection IC comprises a plurality of terminals, each of said terminals being connected to one of the plurality of lithium-ion cells, whereby the voltage of each of the plurality of lithium-ion cells may be monitored.

4. The power tool according to claim 3, wherein the battery protection IC outputs the second detection signal when the voltage of one of the plurality of lithium-ion cells becomes lower than a predetermined voltage value.

5. The power tool according to claim 1, the battery pack further including:

a detection signal terminal for outputting the first detection signal and the second detection signal.