WO2011122696A1 - Battery pack and power tool using the same - Google Patents

Battery pack and power tool using the same Download PDF

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Publication number
WO2011122696A1
WO2011122696A1 PCT/JP2011/058481 JP2011058481W WO2011122696A1 WO 2011122696 A1 WO2011122696 A1 WO 2011122696A1 JP 2011058481 W JP2011058481 W JP 2011058481W WO 2011122696 A1 WO2011122696 A1 WO 2011122696A1
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WO
WIPO (PCT)
Prior art keywords
battery
threshold value
motor
overdischarge
data
Prior art date
Application number
PCT/JP2011/058481
Other languages
French (fr)
Inventor
Shinji Watanabe
Original Assignee
Hitachi Koki Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hitachi Koki Co., Ltd. filed Critical Hitachi Koki Co., Ltd.
Publication of WO2011122696A1 publication Critical patent/WO2011122696A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/44—Methods for charging or discharging
    • H01M10/441—Methods for charging or discharging for several batteries or cells simultaneously or sequentially
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
    • H01M10/482—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte for several batteries or cells simultaneously or sequentially
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0063—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with circuits adapted for supplying loads from the battery
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/007—Regulation of charging or discharging current or voltage
    • H02J7/00712—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters
    • H02J7/00714—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters in response to battery charging or discharging current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/007—Regulation of charging or discharging current or voltage
    • H02J7/00712—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters
    • H02J7/007182—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters in response to battery voltage
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a battery pack and a power tool using the battery pack capable of adequately protecting a motor in the power tool and secondary batteries in the battery pack.
  • the invention provides a battery pack mountable in a power tool including a motor.
  • the battery pack includes a secondary battery that supplies an electric power to the motor; and a controller that controls an electric current flowing into the motor based on both load data related to the motor and battery data related to the secondary battery.
  • the battery pack having this construction can adequately protect the motor and the secondary batteries.
  • the battery pack preferably includes a storing unit that stores a plurality of first overcurrent threshold values for load data and a plurality of second overcurrent threshold values for battery data.
  • the controller selects a smaller overcurrent threshold value between a first overcurrent threshold value corresponding to the load data and a second overcurrent threshold value corresponding to the battery data, and halts the supply of the electric power from the secondary battery to the motor when an electric current flowing into at least one of the secondary battery and the motor exceeds the selected overcurrent threshold value.
  • the battery pack having this construction can adequately protect the motor and the secondary batteries.
  • the battery pack preferably includes a storing unit that stores a plurality of first overdischarge threshold values for load data and a plurality of second overdischarge threshold values for battery data.
  • the controller selects a larger overdischarge threshold value between a first overdischarge threshold value corresponding to the load data and a second overdischarge threshold value corresponding to the battery data, and halts the supply of electric power from the secondary battery to the motor when a voltage of the secondary battery drops below the selected overdischarge threshold value.
  • the battery pack having this construction can adequately protect the motor and the secondary batteries.
  • Another aspect of the present invention provides a power tool on which a battery pack including secondary battery is mountable.
  • the power tool includes a motor driven by an electric power supplied from the secondary battery; and a controller that controls an electric current flowing into the motor based on both load data related to the motor and battery data related to the secondary battery.
  • the power tool having this construction can adequately protect the motor and the secondary batteries.
  • the power tool preferably includes a storing unit that stores a plurality of first overcurrent threshold values for load data and a plurality of second overcurrent threshold values for battery data.
  • the controller selects a smaller overcurrent threshold value between a first overcurrent threshold value corresponding to the load data and a second overcurrent threshold value corresponding to the battery data, and halts the supply of the electric power from the secondary battery to the motor when an electric current flowing into at least one of the secondary battery and the motor exceeds the selected overcurrent threshold value.
  • the power tool having this construction can adequately protect the motor and the secondary batteries.
  • the power tool preferably includes a storing unit that stores a plurality of first overdischarge threshold values for load data and a plurality of second overdischarge threshold values for battery data.
  • the controller selects a larger overdischarge threshold value between a first overdischarge threshold value corresponding to the load data and a second overdischarge threshold value corresponding to the battery data, and halts the supply of electric power from the secondary battery to the motor when a voltage of the secondary battery drops below the selected overdischarge threshold value.
  • the power tool having this construction can adequately protect the motor and the secondary batteries.
  • the battery pack and the power tool of the present invention can adequately protect the motor and the secondary batteries provided in the same.
  • Fig. 1 is a cross-sectional view of a power tool and a battery pack according to a preferred embodiment of the present invention.
  • Fig. 2 is a circuit diagram showing the electrical circuitry in the power tool and battery pack according to the preferred embodiment.
  • Fig. 1 is a cross-sectional view of a power tool 1 and a battery pack 2 according to the preferred embodiment.
  • Fig. 2 is a circuit diagram showing the electrical circuitry in the power tool 1 and battery pack 2.
  • the power tool 1 includes a pair of tool-side terminals 11, a motor 12, a trigger switch 13, a switching element 14, a chuck 15, a mechanical unit 16, and a tool-side memory unit 17.
  • the battery pack 2 includes a pair of battery- side terminals 21, a battery 22, a voltage detection unit 23, a temperature detection unit 24, a current detection unit 25, a microcomputer 26, a discharge-cutoff-signal output unit 27, and a charge-cutoff-signal output unit 28.
  • the battery pack 2 is detachably connected to the power tool 1 via the tool-side terminals 11 of the power tool 1 and the battery-side terminals 21 of the battery pack 2.
  • the motor 12 of the power tool 1 is connected to the tool-side terminals 11 via the trigger switch 13 and switching element 14.
  • the motor 12 is driven when the user operates the trigger switch 13, i.e., switches the trigger switch 13 on.
  • the chuck 15 detachably holds a tip tool (not shown).
  • the mechanical unit 16 transmits the drive force of the motor 12 to the chuck 15.
  • the tool-side memory unit 17 stores load data related to the motor 12 and outputs this load data to the microcomputer 26 of the battery pack 2. The load data will be described later in greater detail.
  • the battery 22 is configured of a plurality of battery cells (secondary batteries) 22a connected in series.
  • the battery cells 22a may be one of various types of secondary batteries, such as nickel-cadmium batteries (hereinafter abbreviated as "NiCad batteries”), nickel-metal hydride batteries (hereinafter abbreviated as “NiMH batteries”), or lithium-ion batteries (hereinafter abbreviated as “Li-ion batteries”).
  • NiCad batteries nickel-cadmium batteries
  • NiMH batteries nickel-metal hydride batteries
  • Li-ion batteries lithium-ion batteries
  • the voltage detection unit 23 detects the voltage of the battery 22 and outputs this battery voltage to the microcomputer 26.
  • the temperature detection unit 24 is disposed in proximity to the battery 22 and functions to detect the temperature of the battery 22 and to output this battery temperature to the microcomputer 26.
  • the current detection unit 25 detects the electric current supplied to the motor 12 and outputs the current value to the microcomputer 26.
  • the microcomputer 26 includes a battery-side memory unit 26a.
  • the battery-side memory unit 26a stores properties of the battery cells 22a, as well as a plurality of overcurrent threshold values and a plurality of overdischarge threshold values.
  • the microcomputer 26 controls the discharge-cutoff-signal output unit
  • the microcomputer 26 similarly controls the charge-cutoff- signal output unit 28 to output a charge cutoff signal to a battery charger upon detecting overcharge in order to halt charging by the battery charger.
  • the microcomputer 26 extracts the overcurrent threshold value corresponding to the load data and the overcurrent threshold value corresponding to the battery data from the plurality of overcurrent threshold values stored in the battery-side memory unit 26a and subsequently selects the smaller overcurrent threshold value between the extracted overcurrent threshold values.
  • the microcomputer 26 detects an overcurrent when the electric current detected by the current detection unit 25 is greater than or equal to the selected overcurrent threshold value and controls the discharge-cutoff-signal output unit 27 to output a discharge cutoff signal upon detecting an overcurrent.
  • the microcomputer 26 also extracts the overdischarge threshold value corresponding to the load data and the overdischarge threshold value corresponding to the battery data from the plurality of overdischarge threshold values stored in the battery-side memory unit 26a and selects the larger overdischarge threshold value between the extracted overdischarge threshold values.
  • the microcomputer 26 detects an overdischarge when the voltage detected by the voltage detection unit 23 is less than or equal to the selected overdischarge threshold value and controls the discharge-cutoff- signal output unit 27 to output a discharge cutoff signal upon detecting an overdischarge.
  • the overcurrent threshold value corresponding to the load data will be considered.
  • the rated load current of the motor 12 may be treated as the load data, for example.
  • the microcomputer 26 extracts a small overcurrent threshold value when the rated load current is small and a large overcurrent threshold value when the rated load current is large.
  • the overcurrent threshold value corresponding to the battery data will be considered.
  • the properties and state of the batteries may be treated as the battery data, for example.
  • Examples of battery properties may be the manufacturer of the battery cells (more specifically, internal resistance, which varies from manufacturer to manufacturer) and type of battery (rated voltage).
  • Examples of the battery state may be the battery voltage and battery temperature (internal resistance).
  • the microcomputer 26 extracts a small overcurrent threshold value when the internal resistance of the battery cells 22a is large and extracts a large overcurrent threshold value when the internal resistance is small.
  • the rated voltage of a battery cell differs according to the type of battery.
  • the higher the rated voltage the larger the electric current that can flow in the battery cells. Therefore, the microcomputer 26 extracts a larger overcurrent threshold value when the rated voltage of the battery cells 22a is high (3.6 V in the case of a Li-ion battery, for example), and extracts a small overcurrent threshold value when the rated voltage is low (1.2 V in the case of a NiCad or NiMH battery, for example).
  • the battery voltage will be considered first.
  • the internal resistance produces a greater quantity of heat.
  • the microcomputer 26 extracts a low overcurrent threshold value when the battery voltage is high and extracts a high overcurrent threshold value when the battery voltage is low.
  • the battery temperature will be considered. At low temperatures, the internal resistance is greater. Therefore, the amount of heat generated in the battery cells increases as the size of the current increases at low temperatures. On the other hand, the amount of heat generated in the battery cells also increases at higher temperatures because the temperature of the battery cells themselves is high. Therefore, the microcomputer 26 extracts a large overcurrent threshold value when the battery temperature is within an appropriate range and extracts a small overcurrent threshold value when the battery temperature is outside this appropriate range.
  • the microcomputer 26 selects the smallest of the overcurrent threshold values from among the values extracted according to the procedure described above, and determines whether the electric current detected by the current detection unit 25 is greater than or equal to the selected overcurrent threshold value. If the detected current value exceeds the selected overcurrent threshold value, the microcomputer 26 determines that overcurrent exists and controls the discharge-cutoff-signal output unit 27 to output a discharge cutoff signal.
  • the microcomputer 26 selects an overcurrent threshold value corresponding to the load data when giving priority to protecting the motor 12 (load) over the battery cells 22a, and selects an overcurrent threshold value corresponding to the battery data when giving priority to protecting the battery cells 22a over the motor 12.
  • the overcurrent threshold value corresponding to the load data will be selected when the rated load current is small.
  • the battery pack 2 can reliably halt discharge in the event of an abnormality, such as a short circuit, occurring when the load is less than one ampere, such as in a light.
  • the overcurrent threshold value corresponding to the battery data may be selected when the rated load current is high in order to prevent deterioration of the battery cells 22a.
  • the microcomputer 26 extracts a large overdischarge threshold value when the rated load current is small and extracts a small overdischarge threshold value when the rated load current is large. Similarly, the microcomputer 26 extracts a large overdischarge threshold value when the internal resistance of the battery cells 22a is high, and extracts a small overdischarge threshold value when the internal resistance is low. Similarly, the microcomputer 26 extracts a small overdischarge threshold value when the rated voltage of the battery cells 22a is high and extracts a large overdischarge threshold value when the rated voltage is low.
  • the microcomputer 26 extracts a large overdischarge threshold value when the battery voltage is high and a small overdischarge threshold value when the battery voltage is low. Similarly, the microcomputer 26 extracts a small overdischarge threshold value when the battery temperature falls within the appropriate range and extracts a large overdischarge threshold value when the battery temperature is outside this range.
  • the microcomputer 26 selects the larger of the overdischarge threshold values from among those values extracted according to the above method and determines whether the voltage detected by the voltage detection unit 23 is less than or equal to the selected overdischarge threshold value. When the detected voltage is less than or equal to the threshold value, the microcomputer 26 determines that overdischarge exists and controls the discharge-cutoff-signal output unit 27 to output an overdischarge cutoff signal.
  • the power tool 1 and battery pack 2 can adequately protect the motor 12 and battery cells 22a.
  • the power tool 1 and battery pack 2 since the power tool 1 and battery pack 2 according to the preferred embodiment select the smaller overcurrent threshold value between the overcurrent threshold value corresponding to the load data and the overcurrent threshold value corresponding to the battery data from the battery-side memory unit 26a, the power tool 1 and battery pack 2 can more adequately protect the motor 12 and battery cells 22a.
  • the power tool 1 and battery pack 2 since the power tool 1 and battery pack 2 according to the preferred embodiment select the larger overdischarge threshold value between the overdischarge threshold value corresponding to the load data and the overdischarge threshold value corresponding to the battery data from the battery-side memory unit 26a, the power tool 1 and battery pack 2 can more adequately protect the motor 12 and battery cells 22a.
  • the microcomputer 26 may control the electric current supplied to the motor 12 based on the load data and the battery data. In such cases, the microcomputer 26 essentially regulates the electric current supplied to the motor 12 so as to match the rated load current. As an example, the microcomputer 26 could reduce the electric current supplied to the motor 12 or the like when the battery temperature is outside the appropriate range.
  • the microcomputer 26 selects the smallest overcurrent threshold value from among the extracted overcurrent threshold values and selects the largest overdischarge threshold value from among the extracted overdischarge threshold values, but the microcomputer 26 may use an average of these threshold values instead.
  • the number of uses of the battery cells 22a may be treated as part of the battery state.
  • the period of continuous use may be treated as part of the battery state in place of the battery temperature.
  • microcomputer 26 is provided in the battery pack 2 in the preferred embodiment, the microcomputer 26 may be provided in the power tool 1 instead.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)
  • Secondary Cells (AREA)

Abstract

A battery pack 2 mountable in a power tool 1 including a motor 12 includes a secondary battery 22a that supplies an electric power to the motor 12; and a controller 26 that controls an electric current flowing into the motor 12based on both load data related to the motor 12 and battery data related to the secondary battery 22a.

Description

[DESCRIPTION]
BATTERY PACK AND POWER TOOL USING THE SAME
(Technical Field)
[0001] The present invention relates to a battery pack and a power tool using the battery pack capable of adequately protecting a motor in the power tool and secondary batteries in the battery pack.
(Background Art)
[0002] Conventional power tools and their battery packs cut off the supply of power from secondary batteries in the battery pack to a motor in the power tool upon determining an overcurrent or overdischarge state in order to prevent degradation of the secondary batteries (see Japanese unexamined patent application publication No. 2009- 095162, for example).
(Disclosure of Invention)
(Technical Problem)
[0003] However, since conventional battery packs and power tools use a fixed threshold value for determining overcurrent and the like, the timing of such determinations is late under certain conditions, resulting in degradation of the secondary battery. Further, the threshold values for overcurrent and the like are set in the conventional technology solely for the purpose of protecting the secondary batteries, with no consideration given for protecting the motor.
Technical Solution
[0004] In view of the foregoing, it is an object of the present invention to provide a battery pack and a power tool employing the same that are capable of adequately protecting the motor of the power tool and the secondary batteries of the battery pack.
[0005] In order to attain the above and other objects, the invention provides a battery pack mountable in a power tool including a motor. The battery pack includes a secondary battery that supplies an electric power to the motor; and a controller that controls an electric current flowing into the motor based on both load data related to the motor and battery data related to the secondary battery.
[0006] The battery pack having this construction can adequately protect the motor and the secondary batteries.
[0007] The battery pack preferably includes a storing unit that stores a plurality of first overcurrent threshold values for load data and a plurality of second overcurrent threshold values for battery data. The controller selects a smaller overcurrent threshold value between a first overcurrent threshold value corresponding to the load data and a second overcurrent threshold value corresponding to the battery data, and halts the supply of the electric power from the secondary battery to the motor when an electric current flowing into at least one of the secondary battery and the motor exceeds the selected overcurrent threshold value.
[0008] The battery pack having this construction can adequately protect the motor and the secondary batteries.
[0009] The battery pack preferably includes a storing unit that stores a plurality of first overdischarge threshold values for load data and a plurality of second overdischarge threshold values for battery data. The controller selects a larger overdischarge threshold value between a first overdischarge threshold value corresponding to the load data and a second overdischarge threshold value corresponding to the battery data, and halts the supply of electric power from the secondary battery to the motor when a voltage of the secondary battery drops below the selected overdischarge threshold value.
[0010] The battery pack having this construction can adequately protect the motor and the secondary batteries.
[0011] Another aspect of the present invention provides a power tool on which a battery pack including secondary battery is mountable. The power tool includes a motor driven by an electric power supplied from the secondary battery; and a controller that controls an electric current flowing into the motor based on both load data related to the motor and battery data related to the secondary battery.
[0012] The power tool having this construction can adequately protect the motor and the secondary batteries.
[0013] The power tool preferably includes a storing unit that stores a plurality of first overcurrent threshold values for load data and a plurality of second overcurrent threshold values for battery data. The controller selects a smaller overcurrent threshold value between a first overcurrent threshold value corresponding to the load data and a second overcurrent threshold value corresponding to the battery data, and halts the supply of the electric power from the secondary battery to the motor when an electric current flowing into at least one of the secondary battery and the motor exceeds the selected overcurrent threshold value.
[0014] The power tool having this construction can adequately protect the motor and the secondary batteries.
[0015] The power tool preferably includes a storing unit that stores a plurality of first overdischarge threshold values for load data and a plurality of second overdischarge threshold values for battery data. The controller selects a larger overdischarge threshold value between a first overdischarge threshold value corresponding to the load data and a second overdischarge threshold value corresponding to the battery data, and halts the supply of electric power from the secondary battery to the motor when a voltage of the secondary battery drops below the selected overdischarge threshold value.
[0016] The power tool having this construction can adequately protect the motor and the secondary batteries.
[Advantageous Effects]
[0017] The battery pack and the power tool of the present invention can adequately protect the motor and the secondary batteries provided in the same.
(Brief Description of Drawings)
[0018] Fig. 1 is a cross-sectional view of a power tool and a battery pack according to a preferred embodiment of the present invention; and
[0019] Fig. 2 is a circuit diagram showing the electrical circuitry in the power tool and battery pack according to the preferred embodiment.
(Explanation of Reference)
1 power tool
2 battery pack
12 motor
17 tool-side memory unit
22a battery cell
23 voltage detection unit
24 temperature detection unit
25 current detection unit
26 microcomputer
26a battery-side memory unit
(Best Mode for Carrying Out the Invention) [0020] Next, a preferred embodiment of the present invention will be described while referring to Figs. 1 and 2.
[0021] Fig. 1 is a cross-sectional view of a power tool 1 and a battery pack 2 according to the preferred embodiment. Fig. 2 is a circuit diagram showing the electrical circuitry in the power tool 1 and battery pack 2.
[0022] As shown in the drawings, the power tool 1 includes a pair of tool-side terminals 11, a motor 12, a trigger switch 13, a switching element 14, a chuck 15, a mechanical unit 16, and a tool-side memory unit 17.
[0023] The battery pack 2 includes a pair of battery- side terminals 21, a battery 22, a voltage detection unit 23, a temperature detection unit 24, a current detection unit 25, a microcomputer 26, a discharge-cutoff-signal output unit 27, and a charge-cutoff-signal output unit 28.
[0024] As illustrated in Fig. 2, the battery pack 2 is detachably connected to the power tool 1 via the tool-side terminals 11 of the power tool 1 and the battery-side terminals 21 of the battery pack 2.
[0025] First, the structure of the power tool 1 will be described. The motor
12 of the power tool 1 is connected to the tool-side terminals 11 via the trigger switch 13 and switching element 14. The motor 12 is driven when the user operates the trigger switch 13, i.e., switches the trigger switch 13 on. The chuck 15 detachably holds a tip tool (not shown). The mechanical unit 16 transmits the drive force of the motor 12 to the chuck 15. The tool-side memory unit 17 stores load data related to the motor 12 and outputs this load data to the microcomputer 26 of the battery pack 2. The load data will be described later in greater detail.
[0026] Next, the structure of the battery pack 2 will be described. The battery 22 is configured of a plurality of battery cells (secondary batteries) 22a connected in series. The battery cells 22a may be one of various types of secondary batteries, such as nickel-cadmium batteries (hereinafter abbreviated as "NiCad batteries"), nickel-metal hydride batteries (hereinafter abbreviated as "NiMH batteries"), or lithium-ion batteries (hereinafter abbreviated as "Li-ion batteries").
[0027] The voltage detection unit 23 detects the voltage of the battery 22 and outputs this battery voltage to the microcomputer 26. The temperature detection unit 24 is disposed in proximity to the battery 22 and functions to detect the temperature of the battery 22 and to output this battery temperature to the microcomputer 26. The current detection unit 25 detects the electric current supplied to the motor 12 and outputs the current value to the microcomputer 26.
[0028] The microcomputer 26 includes a battery-side memory unit 26a. The battery-side memory unit 26a stores properties of the battery cells 22a, as well as a plurality of overcurrent threshold values and a plurality of overdischarge threshold values.
[0029] The microcomputer 26 controls the discharge-cutoff-signal output unit
27 to output a discharge cutoff signal to the power tool 1 upon detecting an overcurrent or overdischarge in order to switch off the switching element 14 and halt electrical discharge. When the battery pack 2 is connected to a battery charger (not shown) in place of the power tool 1, the microcomputer 26 similarly controls the charge-cutoff- signal output unit 28 to output a charge cutoff signal to a battery charger upon detecting overcharge in order to halt charging by the battery charger.
[0030] Next, the overcurrent threshold values and overdischarge threshold values stored in the battery-side memory unit 26a will be described in greater detail.
[0031] In the preferred embodiment, the microcomputer 26 extracts the overcurrent threshold value corresponding to the load data and the overcurrent threshold value corresponding to the battery data from the plurality of overcurrent threshold values stored in the battery-side memory unit 26a and subsequently selects the smaller overcurrent threshold value between the extracted overcurrent threshold values. The microcomputer 26 detects an overcurrent when the electric current detected by the current detection unit 25 is greater than or equal to the selected overcurrent threshold value and controls the discharge-cutoff-signal output unit 27 to output a discharge cutoff signal upon detecting an overcurrent.
[0032] The microcomputer 26 also extracts the overdischarge threshold value corresponding to the load data and the overdischarge threshold value corresponding to the battery data from the plurality of overdischarge threshold values stored in the battery-side memory unit 26a and selects the larger overdischarge threshold value between the extracted overdischarge threshold values. The microcomputer 26 detects an overdischarge when the voltage detected by the voltage detection unit 23 is less than or equal to the selected overdischarge threshold value and controls the discharge-cutoff- signal output unit 27 to output a discharge cutoff signal upon detecting an overdischarge.
[0033] Next, the process for extracting and selecting the overcurrent threshold values and overdischarge threshold values performed by the microcomputer 26 will be described in greater detail.
[0034] First, the overcurrent threshold value corresponding to the load data will be considered. Here, the rated load current of the motor 12 may be treated as the load data, for example. Thus, the microcomputer 26 extracts a small overcurrent threshold value when the rated load current is small and a large overcurrent threshold value when the rated load current is large.
[0035] Next, the overcurrent threshold value corresponding to the battery data will be considered. Here, the properties and state of the batteries may be treated as the battery data, for example. Examples of battery properties may be the manufacturer of the battery cells (more specifically, internal resistance, which varies from manufacturer to manufacturer) and type of battery (rated voltage). Examples of the battery state may be the battery voltage and battery temperature (internal resistance).
[0036] First, consideration will be given for the manufacturer of the battery cells. Generally, when electric current flows through the battery cells, the internal resistance of the cells produces heat, potentially causing damage to the battery cells if the amount of heat produced is large. The amount of heat produced is largely dependent on the magnitude of internal resistance and the size of the electric current, and the internal resistance varies according to the manufacturer of the battery cells. Accordingly, the microcomputer 26 extracts a small overcurrent threshold value when the internal resistance of the battery cells 22a is large and extracts a large overcurrent threshold value when the internal resistance is small.
[0037] Next, consideration will be given for the type of battery. The rated voltage of a battery cell differs according to the type of battery. The higher the rated voltage, the larger the electric current that can flow in the battery cells. Therefore, the microcomputer 26 extracts a larger overcurrent threshold value when the rated voltage of the battery cells 22a is high (3.6 V in the case of a Li-ion battery, for example), and extracts a small overcurrent threshold value when the rated voltage is low (1.2 V in the case of a NiCad or NiMH battery, for example).
[0038] For battery states, the battery voltage will be considered first. When the battery has a high voltage, the internal resistance produces a greater quantity of heat.
Therefore, the microcomputer 26 extracts a low overcurrent threshold value when the battery voltage is high and extracts a high overcurrent threshold value when the battery voltage is low. [0039] Next, the battery temperature will be considered. At low temperatures, the internal resistance is greater. Therefore, the amount of heat generated in the battery cells increases as the size of the current increases at low temperatures. On the other hand, the amount of heat generated in the battery cells also increases at higher temperatures because the temperature of the battery cells themselves is high. Therefore, the microcomputer 26 extracts a large overcurrent threshold value when the battery temperature is within an appropriate range and extracts a small overcurrent threshold value when the battery temperature is outside this appropriate range.
[0040] Next, the microcomputer 26 selects the smallest of the overcurrent threshold values from among the values extracted according to the procedure described above, and determines whether the electric current detected by the current detection unit 25 is greater than or equal to the selected overcurrent threshold value. If the detected current value exceeds the selected overcurrent threshold value, the microcomputer 26 determines that overcurrent exists and controls the discharge-cutoff-signal output unit 27 to output a discharge cutoff signal.
[0041] According to the configuration described above, the microcomputer 26 selects an overcurrent threshold value corresponding to the load data when giving priority to protecting the motor 12 (load) over the battery cells 22a, and selects an overcurrent threshold value corresponding to the battery data when giving priority to protecting the battery cells 22a over the motor 12.
[0042] As an example, it is likely that the overcurrent threshold value corresponding to the load data will be selected when the rated load current is small. In this case, the battery pack 2 can reliably halt discharge in the event of an abnormality, such as a short circuit, occurring when the load is less than one ampere, such as in a light. On the other hand, the overcurrent threshold value corresponding to the battery data may be selected when the rated load current is high in order to prevent deterioration of the battery cells 22a.
[0043] However, when extracting and selecting overdischarge threshold values, the opposite concept to that used for overcurrent threshold values is employed.
[0044] That is, the microcomputer 26 extracts a large overdischarge threshold value when the rated load current is small and extracts a small overdischarge threshold value when the rated load current is large. Similarly, the microcomputer 26 extracts a large overdischarge threshold value when the internal resistance of the battery cells 22a is high, and extracts a small overdischarge threshold value when the internal resistance is low. Similarly, the microcomputer 26 extracts a small overdischarge threshold value when the rated voltage of the battery cells 22a is high and extracts a large overdischarge threshold value when the rated voltage is low. Similarly, the microcomputer 26 extracts a large overdischarge threshold value when the battery voltage is high and a small overdischarge threshold value when the battery voltage is low. Similarly, the microcomputer 26 extracts a small overdischarge threshold value when the battery temperature falls within the appropriate range and extracts a large overdischarge threshold value when the battery temperature is outside this range.
[0045] Next, the microcomputer 26 selects the larger of the overdischarge threshold values from among those values extracted according to the above method and determines whether the voltage detected by the voltage detection unit 23 is less than or equal to the selected overdischarge threshold value. When the detected voltage is less than or equal to the threshold value, the microcomputer 26 determines that overdischarge exists and controls the discharge-cutoff-signal output unit 27 to output an overdischarge cutoff signal.
[0046] By controlling the electric current flowing to the motor based on the load data and battery data in this way, the power tool 1 and battery pack 2 according to the preferred embodiment can adequately protect the motor 12 and battery cells 22a.
[0047] Further, since the power tool 1 and battery pack 2 according to the preferred embodiment select the smaller overcurrent threshold value between the overcurrent threshold value corresponding to the load data and the overcurrent threshold value corresponding to the battery data from the battery-side memory unit 26a, the power tool 1 and battery pack 2 can more adequately protect the motor 12 and battery cells 22a.
[0048] Further, since the power tool 1 and battery pack 2 according to the preferred embodiment select the larger overdischarge threshold value between the overdischarge threshold value corresponding to the load data and the overdischarge threshold value corresponding to the battery data from the battery-side memory unit 26a, the power tool 1 and battery pack 2 can more adequately protect the motor 12 and battery cells 22a.
[0049] While the power tool 1 and battery pack 2 of the present invention have been described in detail with reference to specific embodiments thereof, it would be apparent to those skilled in the art that many modifications and variations may be made therein without departing from the spirit of the invention, the scope of which is defined by the attached claims.
[0050] For example, the microcomputer 26 may control the electric current supplied to the motor 12 based on the load data and the battery data. In such cases, the microcomputer 26 essentially regulates the electric current supplied to the motor 12 so as to match the rated load current. As an example, the microcomputer 26 could reduce the electric current supplied to the motor 12 or the like when the battery temperature is outside the appropriate range.
[0051] In the preferred embodiment described above, the microcomputer 26 selects the smallest overcurrent threshold value from among the extracted overcurrent threshold values and selects the largest overdischarge threshold value from among the extracted overdischarge threshold values, but the microcomputer 26 may use an average of these threshold values instead.
[0052] Further, since the internal resistance of the battery cells 22a increases over multiple uses (charging/discharging cycles), the number of uses of the battery cells 22a may be treated as part of the battery state.
[0053] Further, since the battery temperature increases in proportion to the period of time in which the power tool 1 is used continuously, the period of continuous use may be treated as part of the battery state in place of the battery temperature.
[0054] While the microcomputer 26 is provided in the battery pack 2 in the preferred embodiment, the microcomputer 26 may be provided in the power tool 1 instead.

Claims

1. A battery pack mountable in a power tool including a motor comprising: a secondary battery that supplies an electric power to the motor; and
a controller that controls an electric current flowing into the motor based on both load data related to the motor and battery data related to the secondary battery.
2. The battery pack according to claim 1, further comprising a storing unit that stores a plurality of first overcurrent threshold values for load data and a plurality of second overcurrent threshold values for battery data,
wherein the controller selects a smaller overcurrent threshold value between a first overcurrent threshold value corresponding to the load data and a second overcurrent threshold value corresponding to the battery data, and halts the supply of the electric power from the secondary battery to the motor when an electric current flowing into at least one of the secondary battery and the motor exceeds the selected overcurrent threshold value.
3. The battery pack according to claim 1, further comprising a storing unit that stores a plurality of first overdischarge threshold values for load data and a plurality of second overdischarge threshold values for battery data,
wherein the controller selects a larger overdischarge threshold value between a first overdischarge threshold value corresponding to the load data and a second overdischarge threshold value corresponding to the battery data, and halts the supply of electric power from the secondary battery to the motor when a voltage of the secondary battery drops below the selected overdischarge threshold value.
4. A power tool on which a battery pack including secondary battery is mountable comprising:
a motor driven by an electric power supplied from the secondary battery; and a controller that controls an electric current flowing into the motor based on both load data related to the motor and battery data related to the secondary battery.
5. The power tool according to claim 4, further comprising a storing unit that stores a plurality of first overcurrent threshold values for load data and a plurality of second overcurrent threshold values for battery data,
wherein the controller selects a smaller overcurrent threshold value between a first overcurrent threshold value corresponding to the load data and a second overcurrent threshold value corresponding to the battery data, and halts the supply of the electric power from the secondary battery to the motor when an electric current flowing into at least one of the secondary battery and the motor exceeds the selected overcurrent threshold value.
6. The power tool according to claim 4, further comprising a storing unit that stores a plurality of first overdischarge threshold values for load data and a plurality of second overdischarge threshold values for battery data,
wherein the controller selects a larger overdischarge threshold value between a first overdischarge threshold value corresponding to the load data and a second overdischarge threshold value corresponding to the battery data, and halts the supply of electric power from the secondary battery to the motor when a voltage of the secondary battery drops below the selected overdischarge threshold value.
PCT/JP2011/058481 2010-03-30 2011-03-29 Battery pack and power tool using the same WO2011122696A1 (en)

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