JP2010046785A - Electrical screwdriver, battery pack, and residual capacity detection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect an over-discharge state of a battery without being affected by use environment. <P>SOLUTION: In an electrical screwdriver, a strain gage installed either on a shaft that screws a screw or on a motor portion connected to the shaft detects the over-discharge state when torsion of the shaft is reduced, assuming that a residual capacity of the battery has been decreased. The detection of the over-discharge state is judged by comparing detected values such as a voltage value based on resistance detected according to the torsional amount with a prescribed threshold. When the battery has a large residual capacity, generated torque is large so that the torsion is generated to the shaft by a drive power for rotating the shaft generated at a part of the shaft connecting the motor portion and repulsion force created at a part of the shaft contacting the screw. Therefore, the state of the battery can be accurately grasped by judging the residual capacity of the battery based on such torsion actually generated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a battery pack, an electric driver incorporating the battery pack, and a remaining capacity detection system, and more particularly, an electric driver and battery pack that perform power control by appropriately determining the remaining battery capacity even when the usage environment changes. And a remaining capacity detection system.

  In recent years, the number of electronic devices used using batteries, particularly rechargeable batteries, has increased, and the frequency of use has increased. The battery capacity of these devices is expressed using, for example, a lamp or a liquid crystal, so that the user can know the approximate usable time.

  As one of the methods for detecting the remaining capacity of the secondary battery, there is a detection method by a voltage method in which the remaining capacity of the secondary battery is detected by measuring the voltage of the battery pack. In addition, as another method, there is a detection method using an integration method in which the current supplied from the battery pack to the electronic device is measured and the current value and the supply time are integrated to obtain the remaining capacity of the secondary battery.

  In the detection method based on the integration method, the capacity supplied to the electronic device is calculated from the integrated current value and the supply time, and the remaining capacity is detected from the difference between the capacity when the battery pack is fully charged and the capacity supplied to the electronic device. In addition, the battery pack has a battery-specific characteristic that the battery capacity that can be taken out changes according to the usage environment of the battery pack. For this reason, for example, a reference table of the battery capacity at the time of full charge for each environmental temperature and the battery capacity at the time of full charge that decreases with an increase in the number of cycles is stored in advance in a microcomputer in the battery pack, for example. And by measuring the environmental temperature and the number of cycles of the battery pack and calculating the remaining capacity based on a pre-stored reference table, the battery capacity can be changed according to the usage environment and usage conditions of the battery pack. It can be done.

  By the way, at the time of discharging, if the voltage method is used, there is a problem that the detection accuracy of the remaining capacity becomes very bad at the intermediate potential of the secondary battery. This is because, for example, in the case of a lithium ion battery, the voltage at the intermediate potential is almost constant and the voltage difference does not occur so much, so that it is difficult to detect the remaining capacity by voltage.

  In addition, when the integration method is used, there is a problem that accuracy is deteriorated at the end of discharge. This is because errors are accumulated together with the accumulated current or power due to voltage and current measurement errors and heat loss, and a large error occurs at the end of discharge, which leads to deterioration of accuracy.

  Therefore, a method of detecting the battery capacity using both the integration method and the voltage method is used. In the voltage method, when the current of the secondary battery is small, the capacity calculation accuracy is high, and when the current is large, an accurate open-circuit voltage cannot be obtained due to the battery internal Imp (impedance) or the DC Imp variation due to the environmental temperature. The battery capacity cannot be calculated. In addition, in the integration method, the capacity calculation accuracy is high when the current of the secondary battery is large, and when the current is small, the integration error increases and the capacity calculation accuracy deteriorates.

Therefore, Patent Document 1 below describes that the voltage method is used when the current value is smaller than a preset current value, and the current integration method is used when the current value is larger. By measuring the battery capacity by switching each method, it is possible to improve the calculation accuracy of the battery capacity.
International Publication No. 98/056059 Pamphlet

  However, not all of the batteries produced have exactly the same battery capacity, temperature characteristics, cycle characteristics, etc. Moreover, there is a problem that the deterioration state of each battery differs depending on the usage frequency and usage environment of the battery pack. For this reason, when the method as described above is used, it is very difficult to grasp all the deterioration states that differ depending on the battery pack by the microcomputer and appropriately process them, and the detection accuracy of the remaining capacity may be lowered. There is a problem that there is.

  Moreover, the performance of the electronic devices to which the battery pack is attached differs. For this reason, in the case of a battery pack that performs the remaining capacity detection using the method described above, it is necessary to change the setting of the microcomputer that performs the remaining capacity detection for each electronic device.

  Accordingly, an object of the present invention is to provide an electric driver, a battery pack, and a remaining capacity detection system that can detect an overdischarge state of a battery with high accuracy without being influenced by the use environment of the battery pack. .

  In order to solve the above problems, a first invention includes a driver bit, a driving means for rotating the driver bit, a detection element for detecting strain in one end and the other end of the driver bit, and a detection element. A strain amount detecting means for outputting a detection value corresponding to the amount of strain of the power source, and a power source means for supplying power to the driving means. The power source means detects the detected value output by the strain amount detecting means and the first threshold value. An electric driver having a comparing means for comparing values and a power cut-off means for cutting off power supply to the driving means when the comparison means determines that the detected value is equal to or less than the first threshold value. .

  In the above-described electric driver, it is preferable that the detection value is a voltage value, the power supply means has an amplification circuit that amplifies the detection value input, and the detection value amplified by the amplification circuit is input to the comparison means. .

  Preferably, the power supply means has constant voltage output means, and the constant voltage output means outputs a substantially constant voltage to the strain amount detection means.

  The electric driver described above further includes a lighting unit or an alarm unit, and in the comparison unit, a detection value output by the strain amount detection unit and a second threshold value that is equal to or greater than the first threshold value. When the comparison means determines that the detected value is less than or equal to the second threshold value, the control means causes the control signal to cause the lighting section to emit light, the control signal to output an alarm from the alarm section, and the display. You may make it perform at least 1 output of the control signal which displays that it is an overcharge state in a part.

  The first and second threshold values are preferably variable.

  According to a second aspect of the present invention, there is provided one or more battery cells in which a battery element in which a positive electrode and a negative electrode are stacked via a separator is covered with a first exterior material, and a circuit connected to the one or more battery cells The circuit board includes a substrate and an exterior material that accommodates the battery cell and the circuit board, and the circuit board detects the detected value based on the resistance value and the comparison means for comparing the detected value with a predetermined threshold value. When it is determined that the value is equal to or less than the threshold value, the battery pack includes power cut-off means for cutting off power supply.

  The battery pack described above preferably includes an amplifier circuit that amplifies the input detection value, and the amplifier circuit inputs the amplified detection value to the comparison means. It is preferable to have constant voltage output means for outputting a substantially constant voltage.

  A third invention includes a detection element that is provided in a drive unit that is driven by power supply from a battery and that changes in resistance value according to strain or vibration of the drive unit, and a resistance element that responds to strain or vibration. A strain amount detecting means for outputting a voltage value based on the value; a comparing means for comparing the voltage value with a predetermined threshold; and a constant voltage output means for outputting a substantially constant voltage to the strain amount detecting means. And a remaining capacity detection system that determines whether or not the battery is in an overdischarged state based on the comparison result of the comparison means.

  This remaining capacity detection system may be provided with a power shut-off means for shutting off the power supply to the drive means when the comparison means determines that the detected value is equal to or less than the threshold value.

  In the present invention, when a screw is screwed into an object, a torsion actually generated in a driver bit is detected, and it is determined whether or not an overcharged state has occurred based on a detection value that changes in accordance with the amount of the torsion. be able to.

  According to the present invention, it is possible to detect the overdischarge state of the battery without using a microcomputer that calculates the remaining capacity by integrating the supplied power in the battery pack. For this reason, it is not necessary to integrate the supplied power, and the measurement error is reduced. Further, the remaining battery level does not affect the usage environment, and there is no need to perform correction according to the environmental temperature.

  FIG. 1 schematically shows the configuration of the electric driver 1 of the present invention. FIG. 1A schematically shows the overall configuration of the electric driver 1. FIG. 1B shows the configuration of the shaft 4 that is a driver bit fitted to the screw 20, the motor unit 3 that rotates the shaft 4, and the strain gauge 5 provided on the shaft 4 in the electric driver 1.

  As shown in FIG. 1B, the electric driver 1 of the present invention has a shaft 4 that rotates when connected to the motor unit 3 and drives a screw 20 or the like into an object. When the screw 20 or the like is driven using the electric driver 1, a driving force X for rotating the screw 20 is generated in a portion connected to the motor portion 3 of the shaft 4, and a portion in contact with the screw 20 of the shaft 4 is generated. A repulsive stress X ′ is generated. As described above, the driving force and the repulsive stress are generated in the direction of canceling each other from both ends of the shaft 4, whereby the shaft 4 is twisted.

  In such a shaft 4, since the generated torque is larger in a state where the capacity of the battery pack 10 remains much, that is, in a state close to full charge, the degree of twist becomes large. On the other hand, when the remaining capacity of the battery pack 10 is small, that is, when the battery pack 10 is close to overdischarge, the generated torque is small and the degree of twist is small. And by continuing use, the rotation of the motor in the motor unit 3 stops, the electric driver 1 becomes unusable, and the degree of twist of the shaft 4 becomes zero.

  Thus, the voltage of the battery pack 10 and the twist generated in the shaft 4 have a corresponding relationship, and the twist of the shaft 4 becomes smaller as the battery voltage becomes smaller. Therefore, in the present invention, the twist of the shaft 4 is detected by the strain gauge 5, and when the amount of twist becomes small, it is determined that the remaining capacity of the battery pack 10 is small, and the operation of the electric driver 1 is stopped. To.

  Such a torsion is detected by, for example, a strain amount decrease detection circuit (hereinafter referred to as a strain detection circuit) 15 provided in the battery pack 10. When the strain detection circuit 15 determines that the amount of twist is equal to or less than a predetermined value, for example, the power cutoff circuit 16 of the electric driver 1 controls the motor unit 3 to stop supplying current. .

  In the battery pack, the battery capacity at the time of full charge and the remaining capacity corresponding to a predetermined voltage change according to the environmental temperature of the battery pack, the number of cycles, and the like. For this reason, the actual battery capacity is conventionally calculated by performing correction based on the reference battery capacity (remaining capacity) as described above. On the other hand, in the electric driver of the present invention, the force for actually rotating the shaft can be determined by detecting the amount of twist. Therefore, it is possible to determine whether or not the battery pack is in a state where the electric driver can be used without being affected by the temperature environment or the deterioration state where the battery pack is placed.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  A strain gauge 5 is provided in a portion connected to the shaft portion of the shaft 4 of the shaft 4 of the electric driver 1 or the motor portion 3 of the electric driver 1. As the strain gauge 5, a gauge generally used for strain detection can be used. As the strain gauge 5, a biaxial gauge, a triaxial gauge, or the like may be used in addition to a single axis gauge. The strain gauge 5 is provided on the surface of the installation portion of the shaft 4 or the motor unit 3 with an adhesive or the like.

[Strain gauge]
For example, when a tensile force is applied to an object whose strain is to be detected and a stress is generated inside the object, the strain gauge 5 generates a tensile strain proportional to the stress. At this time, the metal constituting the strain gauge 5 extends with the object, and the resistance value of the metal constituting the strain gauge 5 increases. On the contrary, when a compressive force is applied to the object and a stress is generated inside the object, a compressive strain proportional to the stress is generated. And if the metal which comprises the strain gauge 5 shrinks in connection with this, the resistance value of the metal which comprises the strain gauge 5 will reduce.

  Therefore, when the resistance value of the strain gauge 5 is detected by the strain detection circuit 15 of the battery pack 10 and it is determined that the resistance value is equal to or less than a certain value, the power cutoff circuit 16 rotates the motor of the electric driver 1. Stop. Note that the resistance value being equal to or less than a certain value means that the amount of twist is small (the generated torque is small), and the remaining battery capacity is low (the battery pack 10 is in an overdischarged state). Conceivable.

  The strain gauge 5 is connected to the strain detection circuit 15 of the battery pack 10 and is attached to the shaft 4 with the wiring from the strain detection circuit 15 extended. For this reason, when providing the strain gauge 5 in the shaft 4, the structure which does not produce the twist of wiring is needed.

[Battery pack]
The battery pack 10 is, for example, a battery pack 10 of a lithium ion polymer secondary battery having a square shape or a flat shape. The battery pack 10 includes a battery cell in which a battery element is housed in an exterior material such as a laminate film and a battery can, and a circuit board. And a battery cell and a circuit board are armored with an exterior material, and a top cover and a bottom cover respectively fitted to openings at both ends of the exterior material are provided. The battery pack 10 preferably has a plurality of battery cells.

[Battery cell]
The battery cell is constituted by a battery element and a laminate film in which a belt-like positive electrode and a belt-like negative electrode are sequentially laminated via a separator. Moreover, the gel electrolyte layer is formed on both surfaces of the positive electrode and the negative electrode. A positive electrode terminal connected to the positive electrode and a negative electrode terminal connected to the negative electrode are led out from the battery element. Resin pieces are provided at portions where the positive electrode terminal and the negative electrode terminal are in contact with the exterior material in order to improve adhesion.

[Positive electrode]
The positive electrode has a positive electrode active material layer containing a positive electrode active material formed on both surfaces of the positive electrode current collector. As the positive electrode current collector, for example, a metal foil such as an aluminum (Al) foil, a nickel (Ni) foil, or a stainless steel (SUS) foil is used.

The positive electrode active material layer includes, for example, a positive electrode active material, a conductive agent, and a binder. As the positive electrode active material, mainly Li _x MO ₂ (wherein M represents one or more transition metals, x is different depending on the charge / discharge state of the battery, and is usually 0.05 or more and 1.10 or less). A composite oxide of lithium and a transition metal is used. As a transition metal constituting the lithium composite oxide, cobalt (Co), nickel (Ni), manganese (Mn), or the like is used.

Specific examples of such a lithium composite oxide include lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), and lithium manganate (LiMn ₂ O ₄ ). A solid solution in which a part of the transition metal element is substituted with another element can also be used. Examples thereof include nickel cobalt composite lithium oxide (LiNi _0.5 Co _0.5 O ₂ , LiNi _0.8 Co _0.2 O _2, etc.). These lithium composite oxides can generate a high voltage and have an excellent energy density. Furthermore, TiS _2, MoS _2, may be used NbSe _2, V ₂ O no lithium metal sulfides such as ₅ or metal oxide as a cathode active material. As the positive electrode active material, a mixture of a plurality of these materials may be used.

  As the conductive agent, for example, a carbon material such as carbon black or graphite is used. As the binder, for example, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), or the like is used. Moreover, as a solvent, N-methyl-2-pyrrolidone (NMP) etc. are used, for example.

[Negative electrode]
The negative electrode is formed by forming a negative electrode active material layer containing a negative electrode active material on both surfaces of a negative electrode current collector. As the negative electrode current collector, for example, a metal foil such as a copper (Cu) foil, a nickel (Ni) foil, or a stainless steel (SUS) foil is used.

The negative electrode active material layer includes, for example, a negative electrode active material, a conductive agent, and a binder. As the negative electrode active material, lithium metal, a lithium alloy, a carbon material that can be doped / undoped with lithium, or a composite material of a metal material and a carbon material is used. Specific examples of carbon materials that can be doped / undoped with lithium include graphite, non-graphitizable carbon, graphitizable carbon, and the like. More specifically, pyrolytic carbons, cokes (pitch coke, needle coke). , Petroleum coke), graphites, glassy carbons, organic polymer compound fired bodies (phenol resins, furan resins, etc., calcined at an appropriate temperature), carbon fibers, activated carbon and other carbon materials are used. be able to. Furthermore, as a material capable of doping and dedoping lithium, a polymer such as polyacetylene or polypyrrole or an oxide such as SnO ₂ can be used.

  Various materials can be used as materials capable of alloying lithium, such as tin (Sn), cobalt (Co), indium (In), aluminum (Al), silicon (Si), and these. Often alloys are used. When metallic lithium is used, it is not always necessary to use powder as a coating film with a binder, and a rolled lithium metal plate may be used.

  As the binder, for example, polyvinylidene fluoride (PVdF), styrene butadiene rubber (SBR) or the like is used. As the solvent, for example, N-methyl-2-pyrrolidone (NMP), methyl ethyl ketone (MEK) or the like is used.

[Electrolytes]
As the electrolyte, an electrolyte salt and a non-aqueous solvent that are generally used in lithium ion secondary batteries can be used. Specific examples of the non-aqueous solvent include ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dipropyl carbonate ( DPC), ethylpropyl carbonate (EPC), or a solvent in which hydrogen of these carbonates is substituted with halogen. One of these solvents may be used alone, or a plurality of these solvents may be mixed with a predetermined composition.

As the electrolyte salt, one that dissolves in the non-aqueous solvent is used, and a combination of a cation and an anion is used. As the cation, an alkali metal or an alkaline earth metal is used. As the anion, Cl ⁻ , Br ⁻ , I ⁻ , SCN ⁻ , ClO ₄ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , CF ₃ SO ₃ ^{− and the} like are used. Specifically, lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), bis (trifluoromethanesulfonyl) imide lithium (LiN (CF ₃ SO ₂ ) ₂ ), bis (pentafluoro Ethanesulfonyl) imidolithium (LiN (C ₂ F ₅ SO ₂ ) ₂ ) lithium perchlorate (LiClO ₄ ) and the like. The electrolyte salt concentration is not a problem as long as it can be dissolved in the above solvent, but the lithium ion concentration is in the range of 0.4 mol / kg or more and 2.0 mol / kg or less with respect to the nonaqueous solvent. preferable.

  The gel electrolyte can be obtained by incorporating a non-aqueous solvent and an electrolyte salt into a gel polymer into a gel polymer. The matrix polymer has a property compatible with a non-aqueous solvent. As such a matrix polymer, silicon gel, acrylic gel, acrylonitrile gel, polyphosphazene modified polymer, polyethylene oxide, polypropylene oxide, and their composite polymers, cross-linked polymers, modified polymers, and the like are used. Further, as a fluorine-based polymer, polyvinylidene fluoride (PVdF), a copolymer containing vinylidene fluoride (VdF) and hexafluoropropylene (HFP) as repeating units, vinylidene fluoride (VdF) and trifluoroethylene (TFE). And a polymer such as a copolymer having a repeating unit. Such a polymer may be used individually by 1 type, and may mix and use 2 or more types.

[Separator]
The separator is made of, for example, a porous film made of a polyolefin-based material such as polypropylene (PP) or polyethylene (PE), or a porous film made of an inorganic material such as a ceramic nonwoven fabric. A structure in which a porous film is laminated may be used. Among these, polyethylene and polypropylene porous films are the most effective.

[Circuit board]
The circuit board is one in which the positive terminal and the negative terminal of the battery element are electrically connected. The circuit board is mounted with a protection circuit including a temperature protection element such as a fuse, a thermal resistance element (Positive Temperature Coefficient; PTC element), a thermistor, an ID resistor for identifying the battery pack 10 and the like. For example, three contact points are formed. The protection circuit includes a charge / discharge control FET (Field Effect Transistor), an IC (Integrated Circuit) that monitors the secondary battery and controls the charge / discharge control FET, and the like. In addition, circuits necessary for detecting the remaining capacity of the battery from the strain of the shaft 4 and cutting off the power, such as the strain detection circuit 15 and the power cut-off circuit 16, are mounted. The strain detection circuit 15 and the power cut-off circuit 16 will be described later.

  The heat-sensitive resistance element is connected in series with the battery element, and when the temperature of the battery becomes higher than the set temperature, the electrical resistance increases rapidly and substantially interrupts the current flowing through the battery. The fuse is also connected in series with the battery element. When an overcurrent flows through the battery, the fuse is blown by its own current to cut off the current. In addition, a heater resistor is provided in the vicinity of the fuse. When an overvoltage is applied, the temperature of the heater resistor rises, so that the current is cut off.

  Further, when the terminal voltage of the secondary battery exceeds 4.3 V to 4.4 V, the battery may be in a dangerous state such as thermal runaway. For this reason, the protection circuit monitors the voltage of the secondary battery, and when the voltage exceeds 4.3 V to 4.4 V and becomes overcharged, the charge control FET is turned off to prohibit charging. Furthermore, when the terminal voltage of the secondary battery is overdischarged to below the discharge prohibition voltage and the secondary battery voltage becomes 0V, the secondary battery may be in an internal short circuit state and may not be recharged. For this reason, as a first safety function, the discharge current is interrupted by the strain amount, as a backup, a protection circuit in the battery pack 10 is provided with a discharge control FET, and the voltage of the battery itself is also monitored. Also good.

  A constant voltage is input to the Wheatstone bridge circuit (hereinafter referred to as a bridge circuit as appropriate) 13 from the battery cell via the regulator 12.

[Battery pack circuit configuration]
FIG. 2 shows the configuration of a circuit that detects strain and shuts off power. FIG. 3 shows an example of the circuit configuration of the electric driver 1. In the following description, it is assumed that R2, R3, and R4 of the bridge circuit 13 are the same in FIG. In the bridge circuit 13, regarding the resistance value R <b> 1 of the strain gauge 5, the resistance value of the strain gauge 5 when the shaft 4 of the electric driver 1 is not twisted is R, and the resistance when the shaft 4 is twisted is R. Let the value be R + ΔR. ΔR is a change in resistance value caused by twisting. In the bridge circuit 13, when the shaft 4 is not twisted, that is, when R1 = R, the output voltage V2 is 0V. For this reason, the voltage value output when the shaft 4 is twisted can be a voltage value corresponding to the change in resistance value when the twist is not generated.

  When the power of the electric driver 1 is turned on and a screw or the like is rotated, a twist is generated in the strain gauge 5 provided on the shaft 4 or the motor unit 3 of the electric driver 1. The twist generated in the strain gauge 5 is detected as a resistance value generated according to the amount of twist by the bridge circuit 13 inside the battery pack 10, and the change in the resistance value is converted into a voltage value, so that the strain signal amplification circuit 14 is output.

  The distortion signal amplifier circuit 14 amplifies the voltage value (voltage change) output from the bridge circuit 13. The distortion signal amplification circuit 14 can amplify the signal to an arbitrary magnification by selecting the resistance value of the resistor to be used. For example, it is preferable that amplification is possible up to about 100 times. The amplified voltage value is output to the strain detection circuit 15.

  In the strain detection circuit 15, the input voltage value is compared with a preset threshold value. At this time, the preset threshold value is variable, and is a voltage value at which the battery pack 10 is determined to be in an overdischarged state. The threshold varies depending on the battery type and the like, but when a lithium ion secondary battery is used, for example, the threshold value is set to a voltage value of 2.5 V per cell.

  In the strain detection circuit 15, the voltage value input by the comparator is compared with the threshold value. At this time, for example, when the input voltage value is larger than the threshold value, the output from the comparator is set to the H level. When the input voltage value is smaller than the threshold value, the output from the comparator is set to L level. The comparison result from the comparator is output to the power cut-off circuit 16 (the transistor 8 as the power cut-off circuit 16 in FIG. 3).

  In the power cutoff circuit 16, when the input from the comparator is at the H level, a control signal for controlling the rotation of the motor unit 3 of the electric driver 1 is output to the trigger switch 2. In the case of using the transistor 8 as the power cutoff circuit 16, the transistor 8 is controlled to continue to rotate by keeping the transistor 8 ON. On the other hand, when the input from the comparator is L level, a control signal for controlling the rotation of the motor unit 3 of the electric driver 1 to be stopped is output to the trigger switch 2. When the transistor 8 is used, the rotation of the motor unit 3 of the electric driver 1 is stopped by turning off the transistor 8.

[Circuit configuration of electric driver]
The trigger switch 2 is turned on when the electric driver 1 is driven, and is turned off when the work is stopped. When the trigger switch 2 is turned off, power supply from the battery pack 10 to the motor unit 3 is not performed, so that the rotation of the shaft 4 of the electric driver 1 is stopped. Further, when a control signal for stopping the rotation of the motor unit 3 is input from the power cut-off circuit 16, the rotation of the motor unit 3 is stopped in a state where the trigger switch 2 is turned on.

  In addition, you may make it provide the LED lighting part, an alarm warning part, etc. in the electric driver 1. FIG. In this case, when a control signal for stopping the rotation of the motor unit 3 is output from the power cut-off circuit 16 based on the amount of twist of the shaft 4, the trigger switch 2 is turned off and the LED lighting unit is turned on. Or alarms from the alarm warning section. As a result, it is possible to easily notify the user that the stop of the rotation of the shaft 4 is due to a decrease in the remaining capacity.

  In addition, a display unit may be provided to display that the display unit is in an overdischarged state. The display of the overdischarge state on the display unit and LED lighting and / or alarm warning can be performed together.

  Further, when an overdischarged state is approached, LED lighting, alarm warning, and display on the display unit may be performed. It is preferable because the user can be notified that the battery pack 10 is approaching an overdischarged state before the rotation of the shaft 4 stops.

  In such an operation, when the voltage value becomes a predetermined threshold value or less, LED lighting, alarm warning, and display on the display unit are performed. The threshold value for performing LED lighting, alarm warning, and display on the display unit is the same as or higher than the threshold value for stopping the rotation of the shaft 4. The threshold value for LED lighting, alarm warning, and display on the display unit is variable.

  Moreover, the trigger switch 2 may be configured to function as both the forward / reverse switching switch 6 and the speed control switch 7 as shown in FIG. In this case, when the trigger switch 2 is operated by the user, the rotation direction of the shaft 4 can be adjusted or the rotation speed of the shaft 4 can be adjusted.

  Accordingly, when the rotation of the shaft 4 is stopped while the electric driver 1 is being used, the user can determine that the remaining capacity of the battery pack 10 has decreased. In the present invention, since the remaining capacity of the battery pack 10 can be detected based on the amount of twist actually generated in the shaft 4, the remaining battery capacity is corrected according to the environmental temperature and the deterioration state of the battery pack 10. There is no need. This also prevents an error in the remaining capacity of the battery pack 10.

  Further, since the remaining capacity of the battery can be obtained easily and accurately, it is possible to suppress the battery from being overdischarged. If the battery is in an overdischarged state, deterioration of the battery is promoted, which is not preferable.

  As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, The various deformation | transformation based on the technical idea of this invention is possible.

  For example, the configuration described in the above-described embodiment is merely an example, and various modifications and applications can be made without departing from the gist of the present invention. For example, in the present invention, a distortion amount decrease detection circuit provided with a comparator is provided, and it is determined whether or not the battery is in an overcharged state by comparison with a predetermined threshold value. In such a configuration, a calculation unit for calculating the remaining capacity from the correspondence relationship between the detected voltage value and the remaining battery capacity and a display unit are provided, and the remaining capacity is displayed on the display unit as a percentage or the like. It may be.

It is an approximate line figure showing the composition of the electric driver concerning one embodiment of this invention. It is a block diagram which shows the circuit structure of the electric driver which concerns on one Embodiment of this invention. It is a circuit diagram which shows the structure of the electric driver which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electric driver 2 ... Trigger switch 3 ... Motor part 4 ... Shaft 5 ... Strain gauge 6 ... Forward / reverse changeover switch 7 ... Speed control switch 8 ... Transistor DESCRIPTION OF SYMBOLS 10 ... Battery pack 11 ... Battery 12 ... Regulator 13 ... Wheatstone bridge circuit 14 ... Strain signal amplification circuit 15 ... Strain amount fall detection circuit 16 ... Power cut-off circuit 20 ... ·screw

Claims (11)

A driver bit,
Driving means for rotating the driver bit;
A detection element for detecting strain in one end and the other end of the driver bit;
A strain amount detecting means including the detection element and outputting a detection value corresponding to the strain amount of the strain;
Power supply means for supplying power to the drive means,
The power supply means is
A comparison means for comparing the detection value output by the strain amount detection means with the first threshold value;
An electric driver comprising: a power cut-off means for cutting off power supply to the drive means when the comparison means determines that the detected value is equal to or less than the first threshold value. The electric driver according to claim 1, wherein the detected value is a voltage value. The power supply means has an amplifier circuit for amplifying the input detection value;
The electric driver according to claim 2, wherein the amplification circuit inputs the amplified detection value to the comparison unit. The power supply means has constant voltage output means,
The electric driver according to claim 3, wherein the constant voltage output means outputs the substantially constant voltage to the strain amount detection means. It further comprises at least one of a lighting part, an alarm part and a display part,
In the comparison means, the detection value output by the strain amount detection means is compared with a second threshold value equal to or greater than the first threshold value,
When the comparison means determines that the detected value is less than or equal to the second threshold value, the control means causes the control signal to cause the lighting part to emit light, and the control signal to output an alarm from the alarm part. 5. The electric driver according to claim 4, wherein at least one output of a control signal for displaying the overcharge state on the display unit is performed. The electric driver according to claim 5, wherein the first and second threshold values are variable. A circuit board connected to one or more battery cells;
An exterior material for accommodating the battery cell and the circuit board;
The circuit board includes a comparison unit that compares a detection value detected based on a resistance value with a predetermined threshold value;
A battery pack comprising: a power shut-off means for shutting off the power supply when the comparison means determines that the detected value is equal to or less than the threshold value. An amplification circuit for amplifying the input detection value;
The battery pack according to claim 7, wherein the amplification circuit inputs the amplified detection value to the comparison unit. 9. The battery pack according to claim 8, further comprising constant voltage output means for outputting a substantially constant voltage. A detection element that is provided in a driving unit that is driven by power supply from a battery, and whose resistance value changes according to strain or vibration of the driving unit;
A strain amount detection means including the detection element and outputting a voltage value based on a resistance value corresponding to the strain or vibration;
A comparing means for comparing the voltage value with a predetermined threshold value;
Comprising constant voltage output means for outputting a substantially constant voltage to the strain amount detection means,
A remaining capacity detection system that determines whether or not the battery is in an overdischarged state based on a comparison result of the comparison means. The remaining capacity detection system according to claim 10, further comprising: a power shut-off means for shutting off power supply to the drive means when the comparison means determines that the detected value is equal to or less than the threshold value.

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