JP2006198690A - Electric tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize reduction of battery power consumption when an electric tool is not used and to prevent discharge in an overcharged state of a battery in a charging type electric tool provided with a chargeable battery. <P>SOLUTION: The electric tool is provided with a battery abnormality detecting means 5, which detects voltage of each unit cell of a battery pack 1 and outputs a battery abnormality signal when the voltage is below a prescribed voltage, and a power supply shut-off means 6 for shutting off the power supply to a control part 3 from the battery pack 1. The control part 3 outputs a power supply shut-off signal when detecting that the tool is in a non-operating state for a prescribed period of time. The power supply shut-off means 6 shuts off the power supply to the control part 3 from the battery pack 1 on the basis of at least one signal output of either of the battery abnormality signal outputted by the battery abnormality detecting means 5 and the power supply shut-off signal by the control part 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rechargeable power tool such as an impact driver including a rechargeable battery.

  In a rechargeable electric tool using a DC brush motor that performs commutation with a brush, the motor control unit is configured by an FET that limits the motor current by a chopper operation and its control circuit. In addition, a contact-type switch is provided in the power supply path from the battery to the control unit, and the switch is opened and closed in conjunction with the trigger switch of the tool. When the tool is not operating, the switch is opened and the motor control unit The power supply to is cut off. The above control unit can be realized with a compact configuration, and a space for incorporating a contact type switch into the tool can be secured. However, in a tool using a brushless DC motor, the configuration of the motor control unit is complicated and large, so the contact type It is difficult to secure a space for incorporating the switch. The motor control part of a brushless DC motor is composed of a microcomputer and its associated circuit, but even when the tool is not operating, the microcomputer and other circuit parts consume power continuously unless the supply power is cut off. When the tool is not in operation to reduce battery power consumption, battery consumption is prevented by adding an auto power-off function that automatically shuts off power supply from the battery using a microcomputer and a semiconductor switch.

  This type of function in a conventional rechargeable power tool will be described with reference to FIG. In FIG. 6, reference numeral 100 denotes a battery set composed of a plurality of unit cells, and 101 denotes a start switch, which is a momentary operation type switch that opens when the contact closes and stops when operating. Reference numeral 102 denotes a trigger switch, 103 denotes a microcomputer having a timer function, and 104 denotes a driving device that drives and controls the tool according to a signal output from the microcomputer 103. Reference numeral 105 denotes a PNP transistor connected in parallel with the start switch 101. The start switch 101 and the transistor 105 are provided in a power supply path from the battery set 100 to the microcomputer 103 and the driving device 104, and the transistor 105 is configured to perform an on / off operation in accordance with a signal output of the microcomputer 103. The on / off signal of the trigger switch 102 is input to the microcomputer 103, and the microcomputer 103 detects the on / off of the trigger switch 102 and controls the driving device 104.

When the operator activates the tool, when the operator turns on the activation switch 101 and power is supplied from the battery set 100 to the microcomputer 103 and the driving device 104, the microcomputer 103 is activated by a reset signal output from a reset circuit (not shown). Then, the output logic of the output port P0 is set to LOW to turn on the transistor 105. When the transistor 105 is turned on, the power supply from the battery set 100 to the microcomputer 103 and the driving device 104 is continued through the transistor 105 even when the start switch 101 is restored and turned off, and the operator turns on the trigger switch 102. Thus, the driving device 104 is controlled according to the signal output of the microcomputer 103, and the tool operates. On the other hand, when the tool is left unattended, the trigger switch 102 is in the off state, and the microcomputer 103 measures the time in which the trigger switch 102 is off by the timer function provided, and if it is off for a predetermined time, the transistor 105 is turned off, and the power supply from the battery set 100 is automatically cut off. (For example, see Patent Document 1)
JP 2004-74298 A

  In the conventional electric tool described above, the discharge of the battery set when the tool is not used can be suppressed, but since there is no overdischarge detection function of the battery set, for example, a battery set in which one of the unit cells is in an overdischarged state is used. The tool can be operated even in the mounted state, and the battery set can supply electric power to the motor and the control unit. Therefore, the progress of deterioration of the overdischarged unit cell could not be prevented. In particular, when a lithium ion battery is used as a unit cell of the battery set, there is a problem that the battery life is extremely shortened because the deterioration due to overdischarge proceeds rapidly.

  In addition, when a transistor, which is a means for shutting off the power supply from the battery, fails in the short mode, it is impossible to cut off the power supply from the battery to the control unit, preventing the battery from being consumed, and preventing battery deterioration. There was a problem that was not working.

  The present invention has been made to eliminate the above-mentioned drawbacks of the prior art, and its object is to reduce the power consumption of the battery when the electric tool is not used and to prevent the battery from being discharged in an overdischarged state. An object of the present invention is to provide an electric tool capable of extending the use time and extending the life of a battery.

  Another object of the present invention is to improve the immunity against failure of the means for cutting off the power supply from the battery, to reliably reduce the power consumption of the battery when the power tool is not used, and in the overdischarged state of the battery. It is an object of the present invention to provide an electric tool capable of preventing the discharge.

In the electric tool including the battery set including a plurality of rechargeable cells, a motor, a motor driving unit that drives the motor, and a control unit that controls the motor driving unit,
Battery abnormality detection means for detecting the voltage of each unit cell of the battery group and outputting a battery abnormality signal when the voltage falls below a predetermined voltage, and power supply for cutting off the power supply from the battery group to the control unit A shut-off means is provided, and the control unit outputs a power supply cut-off signal when it detects that the power tool has been inactive for a predetermined time, and the power supply cut-off means is a battery abnormality signal output by the battery abnormality detection means. And the power supply from the battery set to the control unit is cut off based on at least one signal output of the power supply cut-off signal by the control unit.

  Further, the power supply interruption means is configured by arranging two or more interruption mechanisms in series on the power supply path from the battery set to the control unit, and each of the interruption mechanisms is output by the battery abnormality detection means. This is solved by cutting off the power supply from the battery set to the control unit based on at least one signal output of the battery abnormality signal and the power supply cut-off signal by the control unit.

  According to the present invention, the battery abnormality detection means for detecting the voltage of each unit cell of the battery set and outputting a battery abnormality signal when the voltage falls below a predetermined voltage, and the power of the battery set to the control unit A power supply cut-off means for cutting off the supply; the control unit outputs a power supply cut-off signal when detecting that the power tool has been inactive for a predetermined time; the power supply cut-off means is a battery abnormality detection means; The power supply from the battery set to the control unit is cut off based on at least one signal output of the battery abnormality signal output by the control unit and the power supply cut-off signal from the control unit. It is possible to reduce the discharge and prevent the battery from being discharged in an overdischarged state, and it is possible to extend the use time and extend the life of the battery.

  Further, the power supply cutoff means is configured by arranging two or more cutoff mechanisms in series on the power supply path from the battery set to the control unit, and each cutoff mechanism controls the battery abnormality signal output from the battery abnormality detection means. Since the power supply from the battery set to the control unit is cut off based on at least one signal output of the power supply cut-off signal by the unit, the tolerance to failure of the power supply cut-off means can be improved and when the power tool is not used reliably The power consumption of the battery can be reduced and the battery can be prevented from being discharged in the overdischarged state.

Specific embodiments of the present invention will be described below in detail with reference to the drawings.
FIG. 1 is a block circuit diagram of a rechargeable power tool according to a specific embodiment of the present invention.

  In FIG. 1, 1 is a battery set constituted by connecting a plurality of unit cells 1a, 1b, 1c, 1d in series, 2 is a three-phase brushless DC motor (hereinafter referred to as a motor), 4 Consists of FETs (4u, 4v, 4w, 4x, 4y, 4w) with 6 flywheel diodes that serve as the motor drive unit that receives the DC power of battery set 1 and applies variable frequency voltage to motor 2. Lu, Lv, and Lw are the three-phase lines of the motor 2. 3 is a control unit for controlling the inverter converter 4, and includes a microcomputer 3a incorporating peripheral peripherals such as an input / output I / O port, an AD converter, a timer function (not shown), and a gate of each FET of the inverter converter 4. The gate driver 3b is configured to output a signal. The microcomputer 3a outputs the drive signal of each FET of the inverter converter 4 from the output port PA to the gate driver 3b, and the gate driver 3b amplifies the FET drive signal so that each FET is turned on / off. It has become.

  Reference numeral 5 denotes battery abnormality detection means, which is configured using, for example, a battery protection IC such as MM1414 manufactured by Mitsumi Electric. The battery abnormality detection means 5 detects the voltage of each unit cell of the battery set 1, and outputs a LOW logic signal from the DCHG terminal if the voltage of each unit cell is higher than a predetermined voltage. When any one of them becomes a predetermined voltage or less, a HIGH logic signal is output from the DCHG terminal as a battery abnormality signal. 6 is a power supply cut-off means for cutting off the power supply from the battery set 1 to the microcomputer 3a and the gate driver 3b, and is arranged between the power supply output line L1 of the battery set 1 and the power supply input line L2 of the control unit 3. Yes. 7 is a momentary operation type start switch whose contact is closed by the operator's operation. One end of the contact of start switch 7 is connected to ground line L3, and the output signal from the other end is input port P1 of microcomputer 3a. And input to the power supply cutoff means 6. 8 is a motor speed adjusting means composed of a variable resistor whose resistance value changes according to the operator's operation, for example, and the output voltage divided by the motor speed adjusting means 8 is inputted to the AD converter built in the microcomputer 3a. The microcomputer 3a can detect the output voltage value of the motor speed adjusting means 8.

  In this embodiment, the rotation control of the motor 2 by the microcomputer 3a is performed by the motor applied voltage control of 120 ° energization, and the switching operation of the six FETs of the inverter converter 4 is controlled by PWM control in the commutation operation. The current conduction rate is controlled. Further, when the detected output voltage value of the motor speed adjusting means 8 is large, the microcomputer 3a rotates the motor 2 at a high speed by increasing the on duty in the PWM control, and the output voltage value of the motor speed adjusting means 8 is small. At that time, the PWM duty is reduced and the speed of the motor 2 is adjusted according to the output voltage of the motor speed adjusting means 8 so that the motor 2 rotates at a low speed.

  Further, in this embodiment, the microcomputer 3a does not have a tool if the contact of the start switch 7 is open, the input logic of the P1 port is HIGH, and the output voltage value of the motor speed adjusting means 8 is not more than a predetermined voltage. Assuming that the state is in use, the internal timer measures the time for which this state continues, and outputs a HIGH logic power supply cutoff signal from the output port P0 when the unused state continues for a predetermined time or longer. The power supply cutoff means 6 is based on the DCHG terminal output signal of the battery abnormality detection means 5, the output signal of the output port P0 of the microcomputer 3a, and the output signal of the start switch 7, and the power supply of the power supply output line L1, the microcomputer 3a, and the gate driver 3b The input line L2 is connected / disconnected.

  Next, the detailed configuration and operation of the present embodiment will be described with reference to FIGS. In FIGS. 2 to 5, the same function parts as those in FIG. 1 are denoted by the same reference numerals.

  FIG. 2 is a block circuit diagram showing a detailed configuration of the power supply cutoff means 6 in FIG. Q1 is a PNP transistor. A resistor R1 is connected between the emitter and base of the PNP transistor Q1, and a resistor R2 is connected between the base of the PNP transistor Q1 and the DCHG terminal of the battery abnormality detection means 5. When the output signal of DCHG terminal 5 is LOW logic, the base current flows through resistor R2, and PNP transistor Q1 is turned on. Q2 is a PNP transistor. A resistor R3 is connected between the emitter and base of the PNP transistor Q2, and a resistor R4 is connected between the base of the PNP transistor Q2 and the output port P0 terminal of the microcomputer 3a and the output terminal of the start switch 7. When a LOW logic signal is output from the output port P0 of the microcomputer 3a or a LOW logic signal is output from the start switch 7, a base current flows through the resistor R4 so that the PNP transistor Q2 is turned on. It has become. The emitter of the PNP transistor Q1 is connected to the power output line L1 of the battery set 1, the collector of the PNP transistor Q2 is connected to the power input line L2 of the microcomputer 3a and the gate driver 3b, and the collector of the PNP transistor Q1 and the PNP transistor Q2 Are connected, and power is supplied from the battery set 1 to the microcomputer 3a and the gate driver 3b when both the PNP transistors Q1 and Q2 are turned on.

  In this embodiment, when the output signal of the DCHG terminal of the battery abnormality detection means 5 is LOW logic and the PNP transistor Q1 is turned on, when the operator turns on the start switch 7 and turns on the transistor Q2, the battery is sent to the microcomputer 3a. Power is supplied from the set 1, and the microcomputer 3a is activated by a reset signal output from a reset circuit (not shown), and immediately sets the output logic of the output port P0 to LOW, so even if the momentary operation type start switch 7 is turned off The self-holding of the on-state of the transistor Q2 is performed, and the supply of power from the battery set 1 to the microcomputer 3a and the gate driver 3b is maintained. When the microcomputer 3a detects an unused state for a predetermined time or more and outputs a HIGH logic power supply cut-off signal from the output port P0, the transistor Q2 is immediately turned off, and the microcomputer 3a and the gate driver 3b from the battery set 1 are turned off. The power supply is cut off. Note that when a HIGH logic battery abnormality signal is output from the DCHG terminal of the battery abnormality detection means 5, the PNP transistor Q1 is turned off, so it does not depend on the signal output from the output port P0 of the microcomputer 3a and the output terminal of the start switch 7. The power supply from the battery set 1 to the microcomputer 3a and the gate driver 3b is cut off. Therefore, in this embodiment, when the tool is not used, the power supply cutoff means 6 cuts off the power supply of the battery set 1 according to the output of the microcomputer 3a, the battery set 1 becomes overdischarged, and the battery abnormality detection means 5 When the battery abnormality signal is output, the power supply of the battery set 1 is unconditionally cut off, so the power consumption of the battery when the power tool is not used is reduced and the battery is discharged in the overdischarged state. Can be prevented.

  As shown in FIG. 4, the power supply cutoff means 6 comprises a PNP transistor Q41 and resistors R41 and R42, and the output signal of the DCHG terminal of the battery abnormality detection means 5 is input to the input port P2 of the microcomputer 3a, and the microcomputer 3a outputs a high logic power supply cut-off signal from the output port P0 when a high logic battery abnormality signal is detected by the battery abnormality detection means 5 or when an unused state is detected for a predetermined time or longer. By operating in the same manner, the same effects as described above can be obtained.

  Next, FIG. 3 is a block circuit diagram showing an example of the power supply cutoff means 6 having a configuration in which two cutoff mechanisms are arranged in series on the power supply path from the battery set 1 to the control unit 3. Q11 is a PNP transistor serving as a first cutoff mechanism provided on the power supply path from the battery set 1 to the control unit 3, and Q21 is a second cutoff mechanism arranged in series with the PNP transistor Q11 on the supply path This is a PNP transistor. The emitter of the PNP transistor Q11 is connected to the power output line L1 of the battery set 1, the collector of the PNP transistor Q21 is connected to the power input line L2 of the microcomputer 3a and the gate driver 3b, and both the PNP transistors Q11 and Q21 are turned on. During this time, power is supplied from the battery set 1 to the microcomputer 3a and the gate driver 3b.

  The on / off circuit of the PNP transistor Q11 will be described with reference to FIG. 3. A resistor R11 is connected between the emitter and base of the PNP transistor Q11, and a resistor R12 is connected between the base of the PNP transistor Q11 and the collector of the NPN transistor Q12. When the NPN transistor Q12 is turned on, a base current flows through the resistor R12, and the PNP transistor Q11 is turned on. The emitter of PNP transistor Q14 is connected to power line L1, the collector is connected to resistors R15 and R17, and the base is connected to resistor R16.When PNP transistor Q14 is turned on, base current flows to NPN transistor Q12 via resistors R13 and R15. The NPN transistor Q12 is turned on, and the PNP transistor Q11 is also turned on. Here, the base current flows to the NPN transistor Q13 through the resistor R14, and when the NPN transistor Q13 is turned on, the connection point between the resistors R13 and R15 is short-circuited to the ground line L3, so the base current of the NPN transistor Q12 that flows through the resistor R13 Disappears, the NPN transistor Q12 is turned off, and the PNP transistor Q11 is also turned off.

  The on / off circuit of the PNP transistor Q21 is composed of the NPN transistors Q22 and Q23, the PNP transistor Q24, and the resistors R21, R22, R23, R24, R25, R26, and R27 in the same manner as the on / off circuit of the PNP transistor Q11. When the PNP transistor Q24 is turned on, the NPN transistor Q22 is turned on, and the PNP transistor Q21 is also turned on.A base current flows through the resistor R24 to the NPN transistor Q23, and when the NPN transistor Q23 is turned on, the NPN transistor Q22 Is turned off, and the PNP transistor Q21 is also turned off.

  As described above, in the present embodiment, the condition for turning on the PNP transistors Q11 and Q21 is that the NPN transistors Q14 and Q24 are turned on and the NPN transistors Q13 and Q23 are turned off, respectively. On the other hand, the base of each of the NPN transistors Q13 and Q23 is connected to the DCHG terminal of the battery abnormality detection means 5 via the resistors R14 and R24, and when the output signal of the DCHG terminal of the battery abnormality detection means 5 is HIGH logic, The NPN transistors Q13 and Q23 are turned on, and the PNP transistors Q11 and Q12 serving as the first and second cutoff mechanisms are turned off. The bases of each of the PNP transistors Q14 and Q24 are connected to the output port P0 terminal of the microcomputer 3a and the output terminal of the start switch 7 through resistors R16 and R26, and a HIGH logic signal is output from the output port P0 of the microcomputer 3a. Is output, the PNP transistors Q14 and Q24 are turned off. That is, the power supply cut-off mechanism from the battery set 1 to the microcomputer 3a and the gate driver 3b is doubled, and each cut-off mechanism is configured according to the output of the microcomputer 3a when a tool is not used. On the other hand, when the battery set 1 is overdischarged and the battery abnormality signal is output by the battery abnormality detection means 5, the operation to unconditionally cut off the power supply of the battery set 1 is performed. . Therefore, in the configuration of FIG. 2, particularly when the transistor Q1 fails in the short mode, there is a risk that the overdischarge protection of the battery may be incomplete. Thus, the tolerance to a single failure can be improved, the power consumption of the battery can be reliably reduced when the power tool is not used, and the battery can be prevented from being discharged in an overdischarged state.

  In the present embodiment, power supply from the battery set 1 to the inverter converter 4 is not specifically interrupted. FIG. 5 is a block diagram showing the configuration of the gate driver 3b for the U phase, and the other phases are configured in the same manner. The 4x drive power supply for the lower arm FET is based on the power input line L2 of the control unit, and the 4u drive power supply for the upper arm FET is based on the U-phase line Lu of the motor 2 composed of the diode D51 and the capacitor C51. It is a floating power supply. When turning on 4u of the upper arm FET, the microcomputer 3a outputs a HIGH logic signal from the output port PAu so that the NPN transistor Q51 is turned on, the NPN transistor Q52 is turned off, and the NPN transistor of the composite transistor Z51 is turned on. . When turning on the lower arm FET 4x, the microcomputer 3a outputs a HIGH logic signal from the output port PAx so that the NPN transistor of the composite transistor Z52 is turned on.

  By connecting the gate terminals of 4u and 4x which are FETs of the upper and lower arms to the source side with resistors R51 and R52, and discharging the remaining charge on the gate, it is always an inverter when the power supply to the gate driver 3b is cut off Each FET of the converter 4 is turned off, and the power consumption of the motor 2 is cut off. Further, the microcomputer 3a outputs a LOW logic signal from the output port PA so as to turn off each FET of the inverter converter 4 immediately before the power supply cutoff signal is output to the power supply cutoff means 6, and then the power supply cutoff signal. Is output to cut off the power supply from the battery set 1 when the tool is not used.

  Further, in the present embodiment, the unit cells of the battery set 1 are connected in series, but a configuration in which a plurality of unit units configured in series are used in parallel is also conceivable. In this case, a plurality of battery abnormality detection means are provided so as to form a pair in each series unit of the unit cells, and a logical sum of battery abnormality signals from these battery abnormality detection means is input to the power supply cutoff means, and battery abnormality detection is performed. When any one of the means detects a battery abnormality, it is desirable that the power supply cutoff means cut off the power supply from the battery set 1 based on the logical sum of the battery abnormality signals.

It is a block diagram which shows specific embodiment of the rechargeable electric tool used as this invention. 3 is a block circuit diagram showing an embodiment of a power supply cutoff means 6. FIG. 6 is a block circuit diagram showing another embodiment of the power supply cutoff means 6. FIG. 6 is a block circuit diagram showing still another embodiment of the power supply cutoff means 6. FIG. FIG. 5 is a block diagram showing a configuration of a gate driver 3b for the U phase. It is a block diagram which shows the structure of the conventional rechargeable electric tool.

Explanation of symbols

1 is a battery set, 2 is a motor, 3 is a control unit, 4 is a motor drive unit, 5 is a battery abnormality detection unit, and 6 is a power supply cutoff unit.

Claims (3)

In an electric tool including a battery set including a plurality of rechargeable unit cells, a motor, a motor drive unit that drives the motor, and a control unit that controls the motor drive unit,
A battery abnormality detecting means for detecting a voltage of each unit cell of the battery set and outputting a battery abnormality signal when the voltage falls below a predetermined voltage; and supplying power from the battery set to the control unit. A power supply shut-off means for shutting off is provided, and the control unit outputs a power supply cut-off signal when detecting that the power tool has been inactive for a predetermined time, and the power supply cut-off means detects the battery abnormality. An electric power tool that cuts off power supply from the battery set to the control unit based on at least one signal output of a battery abnormality signal by means and a power supply cut-off signal by the control unit. The power supply cut-off means is configured by arranging two or more cut-off mechanisms in series on a power supply path from the battery set to the control unit, and each cut-off mechanism is a battery abnormality signal by the battery abnormality detection means. 2. The power tool according to claim 1, wherein power supply from the battery set to the control unit is cut off based on at least one signal output of a power supply cutoff signal from the control unit. 3. The electric tool according to claim 1, wherein the unit cell of the battery set is a lithium ion battery.

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