JP4936227B2 - Battery pack and electric tool using the battery pack - Google Patents

Description

  The present invention relates to a battery pack using a secondary battery such as a lithium ion battery and an electric tool using the same, and more particularly to a battery pack having a protection circuit for preventing an abnormal temperature rise during charging and discharging and an electric motor using the same. Related to tools.

  As a driving power source for driving a cordless power tool in a power tool, a battery pack constituted by a secondary battery such as a lithium ion battery, a nickel cadmium battery, or a nickel metal hydride battery capable of relatively high capacity is widely used. . In order to prevent overdischarge and improve cycle life characteristics, these battery packs have, for example, those having an overdischarge prevention circuit as disclosed in Patent Document 1. In addition, battery packs using lithium ion batteries are particularly advantageous in that they can be increased in capacity and weight, but if overcharged or overdischarged, there is a possibility of battery deterioration or ignition. Specifically, a dedicated protection IC (control IC) is provided in the battery pack, and when the overcharge / overdischarge is monitored and the charge voltage value is equal to or higher than a predetermined charge voltage value or lower than a predetermined discharge voltage value, the protection IC Alternatively, a countermeasure for protecting the secondary battery is performed, in which a control signal of an overdischarge signal is output to a charger circuit or a load circuit, and the charge / discharge path is cut off based on the control signal.

  Further, as disclosed in Patent Document 2 or Patent Document 3, a thermal protector (temperature-sensitive switch) is provided in the charging path, and particularly when the temperature of the battery rises to a predetermined value or more during charging. In the open state, charging is cut off.

JP 2003-164066 A Japanese Unexamined Patent Publication No. Sho 63-316642 JP 2000-40503 A

  However, the present inventor has examined the life of the battery pack of the cordless power tool using the lithium ion battery pack, and even if the discharge current supplied to the tool body is less than the overdischarge current value, the long time It has been found that when used continuously, the battery cell temperature of the battery pack may exceed the rated value and cause deterioration or breakage of the battery cell.

  Accordingly, an object of the present invention is to provide a battery pack having a protection circuit that solves the above-described problems and prevents an abnormal temperature rise during charging and discharging, and an electric tool using the battery pack.

  Another object of the present invention is to provide an inexpensive battery pack having safety and long life.

  Among the inventions disclosed in accordance with the present invention in order to solve the above problems, the summary of typical ones will be described as follows.

  According to one aspect of the present invention, based on the battery cell or cells and the battery voltage of the battery cell, the battery voltage is in an overcharged state that is greater than or equal to a predetermined charge value, or is greater than or equal to a predetermined discharge value. Overcharge / overdischarge detection means for detecting a discharge state and outputting a control signal indicating overcharge or overdischarge; and a charging path for the battery cell, wherein the temperature of the battery cell is equal to or higher than a predetermined temperature value When the temperature of the battery cell becomes equal to or higher than the predetermined temperature value, the temperature sensitive switch means opens the charging path when the battery cell temperature rises to the predetermined temperature value. A discharge stop signal is output by opening the charging path.

  According to another feature of the invention, the discharge stop signal is output as a control signal indicating overdischarge.

  According to still another aspect of the present invention, the battery pack includes a pair of discharge terminals electrically connected to the positive electrode side and the negative electrode side of the battery cell, and branches from one of the discharge terminals via the charge path. The temperature sensing switch means is inserted into the charging path between the one discharging terminal and the charging terminal.

  According to still another aspect of the present invention, the battery pack includes a temperature sensing element that detects a battery temperature separately from the temperature sensing switch means.

  According to still another aspect of the present invention, a motor drive circuit device for driving an electric motor, an electric tool body including a motor control circuit device for controlling the motor drive circuit device, the motor drive circuit device, and the motor control circuit A battery pack having one or more battery cells for supplying power to the apparatus, wherein the battery pack is provided in a charging path of the battery cells, and the temperature of the battery cells is a predetermined temperature value. When the temperature rises above, the temperature-sensitive switch means for opening the charging path, and when the temperature of the battery cell becomes equal to or higher than the predetermined temperature value, the discharge is stopped based on the opening of the temperature-sensitive switch means. The power tool body is capable of being turned on or off based on the control signal of the control terminal. And when the temperature of the battery cell becomes equal to or higher than the predetermined temperature value during operation of the power tool body, the temperature output from the control terminal based on opening of the temperature sensitive switch means The power cutoff switch means is turned off by a control signal.

  According to still another aspect of the present invention, the battery pack has a pair of discharge terminals electrically connected to the positive electrode side and the negative electrode side of the battery cell, and branches from one of the discharge terminals via the charge path. The temperature sensing switch means is inserted into the charging path between the one discharging terminal and the charging terminal.

  According to the above-described feature of the present invention, since the rising temperature of the battery cell at the time of discharging is detected and the predetermined temperature is exceeded, the charging path and discharging path of the battery pack can be shut off, thereby preventing the deterioration or breakage of the battery pack be able to. Further, since the temperature sensitive switch (thermal protector) used at the time of charging is also used at the time of discharging, the number of parts of the temperature sensitive switch can be reduced and the battery pack can be manufactured at low cost. In addition, since the temperature-sensitive switch can also be used with a relatively small switching capacity (current capacity) for supplying charging current, the battery pack can be manufactured at a lower cost and the size of the battery pack can be reduced. .

  Furthermore, since the battery pack incorporates a temperature sensing element in addition to the temperature sensing switch, the battery pack is charged by three detection functions: the temperature sensing switch, the temperature sensing element, and the overcharge / overdischarge detection means. Battery abnormalities at the time, that is, abnormal temperature rise and overcharge can be monitored. Thereby, deterioration of a battery pack can be prevented reliably. The present invention is particularly effective when applied to a battery pack and a power tool when a discharge current within the rating is supplied from the battery pack for a long time.

  The above and other objects, and the above and other features and advantages of the present invention will become more apparent from the following description of the present specification and the accompanying drawings.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 5. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted.

  First, the circuit configuration of the battery pack according to the embodiment of the present invention will be described. FIG. 1 is a circuit diagram of a battery pack according to an embodiment. The battery pack 201 includes an assembled battery having a nominal voltage of 10.8 V (voltage at charging 12 V) in which three battery cells 109, 110, and 111 of a lithium ion secondary battery are connected in series, and at least one of the battery cells 109, 110, and 111. At least one of a thermal protector (temperature switch) 107 for detecting the temperature of the battery cell, which is arranged close to one, a shunt resistor 108 for detecting the discharge current, and the battery cells 109, 110 and 111 And a thermistor 112 for measuring the temperature of the battery cell, a control IC (protection IC) 123, and a signal output circuit 140. The number of battery cells incorporated in the battery pack 201 can be changed according to the required nominal voltage. Furthermore, the battery pack 201 may be constituted by a single battery cell.

  The battery pack 201 further includes a change in resistance value based on a temperature change of the battery set (battery cell) by the plus terminal 101 for charging, the plus terminal 102 for discharging, the minus terminal 103 for charging / discharging, and the thermistor 112. A resistance detection terminal (temperature terminal) 104 of the thermistor 112 for measuring the signal S, an overcurrent / overdischarge signal terminal 105 for outputting an overcurrent or overdischarge detection signal (control signal) LD, And an overcharge signal terminal 106 for outputting a charge detection signal (control signal) LE.

  The battery pack 201 and the electric tool body 202 are electrically connected via terminals 102, 103, and 105. That is, the battery voltage of the battery pack 201 is fed (applied) to the power tool main body 202 via the terminal 102 and the terminal 103, and is based on the output control signal of the overcurrent / overdischarge signal terminal 105. Control the built-in control device.

  On the other hand, the battery pack 201 and the charger 301 are electrically connected via the terminals 101, 103, 104 and 106. That is, at the time of charging, the charger 301 supplies power to the battery pack 210 via the pair of charging terminals 101 and 103, and the resistance change of the output control signal of the overcharge signal terminal 106 and the resistance detection terminal 104 of the thermistor. The charging operation of the control device of the charger 301 is controlled based on the above.

  The thermal protector 107 is, for example, a temperature-sensitive switching element using a bimetal contact that deforms in response to the temperature of the battery cell, and the temperature of the battery cells 109 to 111 is equal to or higher than a predetermined temperature (for example, 80 ° C. or higher) by overcharging. When it rises, the charging path is cut off by opening the bimetal contact, and the charging current supplied to the battery cells 109 to 111 is cut off. In particular, the thermal protector 107 is also used as a detecting means for detecting an abnormal temperature rise above a predetermined temperature (for example, 80 ° C. or higher) of the battery cells 109 to 111 during discharging according to the present invention.

  Although not shown, the control IC 123 includes a comparison circuit, a detection time setting circuit, and an output level conversion circuit. When the overcurrent, overdischarge, and overcharge of the battery cells 109 to 111 are monitored and detected 4 outputs control signals indicating overcharge and overcurrent / overdischarge signals to the OV terminal and DCHC terminal of the control IC 123, as shown in the function table of the battery pack in FIG.

  For this reason, the voltage change of the positive electrode of the battery cell 109 is averaged and input to the input terminal V3 of the control IC 123 by the resistor 115 and the capacitor 120 that form an integration circuit (time constant circuit). Similarly, a voltage change of the positive electrode of the battery cell 110 and a voltage change of the positive electrode of the battery cell 111 are connected to the input terminal V2 and the input terminal V1 of the control IC 123 by an integrating circuit including the resistor 116 and the capacitor 121, and The signals are input via integration circuits each including a resistor 117 and a capacitor 122. The change in the battery voltage at the terminals V3 to V1 of the control IC 123 is compared with the maximum reference voltage (4.3 V / cell) corresponding to the maximum cell voltage during charging by the control IC 123, as shown in FIG. On the contrary, it is compared with the lowest reference voltage (2.0 V / cell) corresponding to the lowest cell voltage at the time of discharge to determine whether it is overdischarge.

  On the other hand, the control IC 123 has an input terminal Vcc and a CS terminal for detecting a discharge current flowing through the detection resistor 108. The positive voltage of the assembled battery (battery cells 109 to 111) is averaged and input to the input terminal Vcc by the resistor 114 and the capacitor 119 that form an integration circuit (time constant circuit). A voltage obtained by subtracting the voltage drop due to the discharge current flowing through the detection resistor 108 from the input voltage of the terminal Vcc is averaged and input by the resistor 113 and the capacitor 118 forming an integration circuit (time constant circuit). Whether the maximum discharge current value is 30 A or less by setting the resistance value of the resistor 108 to, for example, 5 mΩ and detecting whether the voltage drop between the terminal Vcc and the terminal CS is 150 mV or less. Is detected and an overcurrent is determined.

  That is, the control IC 123 detects the overcharge and overdischarge that occur at the time of charge / discharge by monitoring the battery voltage of each of the battery cells 109 to 111, and the overcharge signal and overcharge are output from the output terminals OV and DCHG according to the detection result. Outputs a discharge signal. Further, the overcurrent is detected by monitoring the voltage across the resistor 108, and an overcurrent signal is output from the output terminal DCHG according to the detection result.

  The control IC 123 has an output terminal OV and an output terminal DCHG for outputting a control signal. As shown in FIG. 4, the output terminal OV is composed of an open collector terminal, and normally exhibits high impedance (HZ), and the H signal (high signal) is generated when the resistor 135 of the output circuit 140 operates as a clamp resistor. ) Is output, however, when an overcharge state occurs, an L signal (low signal) is output. The output terminal DCHG normally outputs an L signal, but outputs an H signal when an overcurrent or overdischarge state occurs.

  The control IC 123 further has capacitor connection terminals COV, CDL and CDC for delaying the detection time. That is, a capacitor 124 for setting a dead time at the time of overcharge detection is connected to the capacitor connection terminal COV, and a capacitor 125 for setting a dead time at the time of overcurrent detection is connected to the capacitor connection terminal COL. Is done. Further, a capacitor 126 for setting a dead time when overdischarge is detected is connected to the capacitor connection terminal CDC.

  The output circuit 140 includes output FETs (switching elements) 129, 134, and 136, resistors 127, 128, 130, 133, and 135 for setting an operating potential, and diodes 131 and 132. The operation of each FET 129, 134 and 136 of the output circuit 140 is as shown in FIG.

  FIG. 2 shows a configuration diagram of an electric tool (applied to an impact driver) constituted by a battery pack 201 and an electric tool body 202 according to the present invention, and FIG. 3 shows a circuit function block diagram of the electric tool shown in FIG. Show. As shown in FIG. 3, the electric tool body 202 controls a motor 207 for driving a tip tool (not shown), a motor drive circuit 206 such as an inverter circuit for rotating the motor 207, and the motor drive circuit. And a trigger switch 205 for inputting a control signal for rotating and stopping the motor 207 to the control circuit 204, and a power cutoff switch 203 inserted in the power supply line Lv of the battery pack 201. Is done. According to such a configuration, if the cell temperature of the battery cells 109 to 111 of the battery pack 201 is abnormally increased to a predetermined value or more during operation of the power tool main body 202, the power cutoff switch 203 that is normally in the ON state is set. It has the function of turning off and opening the supply line Lv to cut off the discharge current flow path. That is, when the cell temperature of the battery pack 201 rises to 80 ° C. or more due to the long-time discharge current, the discharge stop signal is controlled from the control output terminal 105 of the battery pack 201 as an overcurrent signal (L level). Input to the circuit 204. The control circuit 204 turns off the power cutoff switch 203 based on the overcurrent signal (discharge stop signal) to suppress the discharge current. Thereby, it can prevent from the thermal destruction of the battery cells 109-111 of the battery pack 201. FIG.

  Next, a series of operations of the battery pack 201 when the battery pack 201 is connected to the charger 301 or the power tool main body 202 will be described with reference to an operation flowchart shown in FIG.

First, overdischarge detection of the battery cells 109 to 111 is performed by the control IC 123. That is, in step 301, it is determined whether or not the cell voltage of the battery cell is lower than the overdischarge voltage value (2.0V). At this time, the voltages of the battery cells 109 to 111 are averaged by an integrating circuit including the resistors 115 to 117 and the capacitors 120 to 122, and are input to the voltage input terminals V1 to V3 of the protection IC 123.
In step 301, the voltages input to the voltage input terminals V1 to V3 are compared with a preset comparison voltage (for example, 2.0 V / cell), and the voltage of the battery cell is determined based on the preset voltage. If it is low (in the case of YES), it is determined that there is a possibility of an overdischarge state. At this time, even if the dead time set by the capacitor 126 has elapsed, if the voltage of the battery cell is in a low state, it is determined that the battery is in an overdischarge state, and an overdischarge signal H is output from the DCHG terminal (step 305).

  In step 305, when the H level is output from the DCHG terminal, it is input to the gate terminal of the FET 134 through the diode 132, and the FET 134 is turned on (step 306). When the FET 134 is turned on, an L-level overcurrent / overdischarge signal LD is output from the terminal 105 (step 307). The power tool main body 202 detects the overcurrent / overdischarge signal LD, and the control circuit 204 shuts off the power cutoff switch 203 to stop the operation of the motor drive circuit 206 (step 308).

  If it is determined in step 301 that the overdischarge state is not present (in the case of NO), the process proceeds to step 302 to detect whether or not the discharge current is an overcurrent. As described above, the discharge current is detected by averaging the voltage (voltage drop) at both ends of the shunt resistor 108 proportional to the discharge current flowing through the shunt resistor 108 by the integrating circuit including the resistor 113 and the capacitor 118, and controlling the control IC 123. It detects by inputting into terminal CS. The control IC 123 determines that there is a possibility of an overcurrent state when the voltage input to the CS terminal falls below a preset voltage value (for example, 150 mV) with reference to the voltage at the terminal VCC. For example, when the resistance value of the shunt resistor 108 is 5 mΩ, the overcurrent detection value is 150 mV / 5 mΩ = 30 A. Next, if the discharge current value exceeds the set value even after the dead time set by the capacitor 125 has elapsed, it is determined as an overcurrent state, and in the same way as the overdischarge state, a high level is detected from the DCHG terminal. An overcurrent signal is output (step 305). Thereafter, similarly to the above-described step at the time of overdischarge detection, the process proceeds to steps 306 to 308, and the operation of the motor drive circuit 206 is stopped by the control circuit 204 of the tool body 202.

  Next, when it is determined in step 302 that there is no overcurrent state (in the case of NO), the process proceeds to step 303, where overcharge is detected. In the overcharge detection, the voltage of the battery cells 109 to 111 is detected and compared with a preset comparison voltage (for example, 4.3 V / cell) similarly to the overdischarge detection in step 301. In step 303, when the voltage of the battery cells 109 to 111 is higher than a preset voltage (for example, 4.3 V / cell), it is determined that there is a possibility of an overcharge (overvoltage) state. At this time, if the battery cells 109 to 111 are in a high voltage state even after the dead time set by the capacitor 124 has elapsed, it is determined that the battery is overcharged, and an L level overcharge signal is output from the OV terminal. Is output (step 309). Since the OV terminal of the control IC 123 is normally in a high impedance (HZ) state, the battery voltage is given by the pull-up resistor 135 and is at the H level. When overcharged, L level is output.

  The L level control signal output from the OV terminal is supplied to the gate of the FET 136 to turn off the FET 136, which is normally in the ON state (step 310). As a result, an overcharge signal LE in the H level or high impedance HZ state is output from the overcharge terminal 106 to a control circuit (not shown) of the charger 301 (step 311). Thereby, the charging operation of the charger 301 is stopped (step 312).

  Next, when it is determined in step 303 that the battery is not overcharged (in the case of NO), the process proceeds to step 304 where temperature detection of the battery cells 109 to 111 is performed. This temperature detection is performed by the thermal protector 107 as described above. The thermal protector 107 is in a short-circuited state (closed state) at a normal temperature, but is in an open state when the temperature exceeds a predetermined temperature (for example, 80 ° C.). According to the present invention, the thermal protector 107 is used for both detecting an abnormal temperature increase during charging and detecting an abnormal temperature increase during discharging.

  First, temperature protection of battery cells during charging will be described. The thermal protector 107 is installed between the plus side terminal 101 for charging and the plus side terminal 102 for discharging. That is, the thermal protector 107 is inserted into a charging path branched from the discharging path (discharging terminal 102) of the battery cells 109 to 111. Therefore, when the temperature of the battery cells 109 to 111 becomes equal to or higher than the set temperature (for example, 80 ° C.) of the thermal protector 107 due to some abnormality, the thermal protector 107 is opened (step 313), and charging is immediately stopped (step 313). Step 314). This prevents overheating during charging.

  Next, overheat protection during operation of the power tool body 202, that is, during discharge will be described. When the temperature of the battery cells 109 to 111 becomes equal to or higher than the set temperature (80 ° C.) of the thermal protector 107 due to a long-time discharge current at the time of discharging, the thermal protector 107 is opened (step 313). Therefore, the charging path is immediately interrupted (step 314).

  Since the charging terminal 101 is electrically separated from the discharging terminal 102 by the open state of the thermal protector 107, the battery voltage applied to the gate bias resistors 127 and 128 of the FET 129 is cut off, and the FET 129 is in the OFF state. (Step 315). Therefore, the gate voltage is input from the discharging plus terminal 102 to the gate of the FET 134 via the resistor 130 and the diode 131, and the FET 134 is turned on (step 306). As a result, a discharge stop signal is output as an L-level overcurrent / overdischarge signal LD from the overcurrent / overdischarge terminal 105 in the same manner as in the case of the overcurrent discharge (step 307). By inputting the LD to the control circuit 204 of the electric power tool main body 202, the operation of the electric power tool main body 202 can be stopped by the control circuit 204 (step 308).

  Next, when the temperature of the battery cells 109 to 111 is not in an overtemperature state in Step 304 (in the case of NO), the process returns to Step 301 and overdischarge, overcurrent, overcharge, and overtemperature are performed by the method described above. Monitor.

  As will be apparent from the above description of the embodiment, according to the present invention, the battery pack is detected based on the operation of the thermal protector 107 when the rising temperature of the battery cell during discharge is detected and the temperature exceeds a predetermined temperature. Since the charging paths and discharging paths 109 to 111 can be blocked, overheating deterioration or overheating damage of the battery pack can be prevented even during discharging.

  Further, since the thermal protector 107 used at the time of charging is also used as an overheat detecting means at the time of discharging, the number of parts of the temperature sensitive switch such as the thermal protector can be reduced and the battery pack can be manufactured at low cost. Furthermore, according to the present invention, since the thermal protector 107 is inserted into the charging path, it is possible to select one that can conduct only a charging current that is relatively smaller than the discharging current. Therefore, a thermal protector with a small current capacity can be used. For this reason, while being able to arrange | position the thermal protector 107 which made the thermal coupling close with the battery cells 109-111, the size of the battery pack 201 can be made smaller.

  Further, according to the present invention, the battery pack 201 outputs only the overtemperature signal (control signal) LD, and the power cut-off switch 203 of the discharge path is external to the battery pack 201 such as a circuit board built in the electric power tool body 202. Since it can be mounted, an appropriate capacity corresponding to the operating current (discharge current) of the power tool main body 202 can be selected for the power cutoff switch 203 formed of a power FET or the like. Furthermore, since the temperature is monitored by the thermal protector 107 and the thermistor 112 even during charging, the abnormal temperature rise can be detected more reliably, so that deterioration of the battery can be prevented more completely. The present invention is particularly effective when applied to a battery pack and a power tool when a discharge current within the rating is supplied from the battery pack for a long time.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. . For example, if the power tool 202 has a relatively small discharge current, the power cutoff switch 203 provided in the power tool is configured in a discharge path in the battery pack using a switching element such as a power FET, and the above You may comprise so that it may control directly with an overcurrent and overdischarge signal (LD). In the above-described operation flowchart, the overdischarge, overcurrent, overcharge, and overtemperature monitoring order (monitoring sequence) is not limited to the order of the above-described embodiments. It may be executed first. In addition, the temperature-sensitive switch element 107 is inserted between the charging plus terminal 101 and the discharging plus terminal 102, but the plus terminal is used for charging / discharging in common, and the charging / discharging minus terminal 103 is used as a charging and discharging minus terminal. It may be inserted between the minus terminals.

The circuit diagram of the battery pack concerning one embodiment of the present invention. FIG. 2 is a structural diagram of the battery pack and the power tool main body shown in FIG. 1. The functional block diagram of the battery pack and electric tool main body shown in FIG. The function table | surface which shows the protection function of the battery pack shown in FIG. The operation | movement flowchart for demonstrating operation | movement of the battery pack shown in FIG.

Explanation of symbols

101: Positive terminal for charging 102: Positive terminal for discharging 103: Negative terminal for charging / discharging 104: Resistance detection terminal for thermistor 105: Overcurrent / overdischarge signal terminal 106: Overcharge signal terminal 107: Thermal protector 108: Shunt resistance 109 to 111: Battery cell 112: Thermistor 113 to 117, 127, 128, 130, 133, 135: Resistor 118 to 121, 122, 124, 125, 126: Capacitor 123: Control IC (protection IC) 129, 134, 136 : FET
131, 132: Diode 140: Output circuit 201: Battery pack 202: Electric tool body 203: Power cut-off switch 204: Control circuit 205: Trigger switch 206: Motor drive circuit 207: Motor

Claims (6)

Based on one or a plurality of battery cells and the battery voltage of the battery cell, it is detected that the battery voltage is in an overcharge state that is equal to or higher than a predetermined charge value or an overdischarge state that is equal to or lower than a predetermined discharge value. Overcharge / overdischarge detection means for outputting a control signal indicating charging or overdischarge; and a charging path for the battery cell. When the temperature of the battery cell rises above a predetermined temperature value, the charging path is A temperature-sensitive switch means to be opened, and a battery pack comprising:
A battery pack, wherein when the temperature of the battery cell becomes equal to or higher than the predetermined temperature value, a discharge stop signal is output by opening the charging path by the temperature sensitive switch means.   The battery pack according to claim 1, wherein the discharge stop signal is output as a control signal indicating overdischarge.   The battery pack includes a pair of discharge terminals electrically connected to the positive electrode side and the negative electrode side of the battery cell, and a charge terminal branched from one of the discharge terminals via the charging path, The battery pack according to claim 1 or 2, wherein the temperature switch means is inserted into the charging path between the one discharge terminal and the charging terminal.   The battery pack according to any one of claims 1 to 3, wherein the battery pack includes a temperature sensing element that detects a battery temperature separately from the temperature sensing switch means. A motor drive circuit device that drives an electric motor, an electric tool body that includes a motor control circuit device that controls the motor drive circuit device, and a power supply that supplies power to the motor drive circuit device and the motor control circuit device. In a power tool comprising a battery pack having battery cells,
The battery pack is provided in a charging path of the battery cell, and when the temperature of the battery cell rises above a predetermined temperature value, temperature-sensitive switch means that opens the charging path, and the temperature of the battery cell is the temperature of the battery cell A control terminal that outputs a control signal indicating discharge stop based on the opening of the temperature-sensitive switch means when the temperature is equal to or higher than a predetermined temperature value;
The power tool body has a power cut-off switch means that can be turned on or off based on a control signal of the control terminal,
When the temperature of the battery cell becomes equal to or higher than the predetermined temperature value during operation of the electric power tool body, the power supply is shut off by the control signal output from the control terminal based on the opening of the temperature sensitive switch means. An electric tool characterized in that the switch means is turned off.   The battery pack includes a pair of discharge terminals electrically connected to a positive electrode side and a negative electrode side of the battery cell, and a charge terminal branched from one of the discharge terminals via the charging path, The electric power tool according to claim 5, wherein the temperature switch means is inserted into the charging path between the one discharge terminal and the charging terminal.

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