JP2000176854A - Battery type fastening tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent fastening work in torque shortage and to improve working efficiency. SOLUTION: At first voltage VE becomes larger than voltage VF and voltage of a comparator OP3 becomes H when a switch SW2 opens and a switch SW3 is closed. Consequently, FETQ1 remains off. At this time, in the case where residual capacity of a battery is lowered below set residual capacity, voltage at an A point remains opened, and the voltage of the comparator OP3 is held H. Consequently, the FETQ1 remains off, and a motor 1 does not start. In the meantime, when the residual quantity of the battery is more than the set residual capacity, the voltage of the A point grounds, the voltage VE is lowered and the voltage of the comparator OP3 becomes L. Consequently, the FETQ1 is turned on, and the motor 1 starts. Even when the residual capacity of the battery is lowered below the set residual capacity while the motor 1 is driven and the voltage VE is lowered, the voltage of the comparator OP3 does not become H because of a diode D4. Consequently, the motor 1 is not stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery-operated fastening tool such as a screwdriver, a torque wrench, and an impact wrench for tightening screws such as screws, nuts and bolts, the motor being driven by a battery. In particular, the present invention relates to a battery-operated fastening tool with a forced stop mechanism for forcibly stopping driving of a motor when the remaining capacity of a battery becomes smaller than a set remaining capacity.

[0002]

2. Description of the Related Art In a battery-operated fastening tool, the remaining capacity of a battery decreases with use. Then, when the tightening work is performed in a state where the remaining capacity of the battery is lower than the set remaining capacity,
Insufficient tightening torque may cause insufficient tightening of the screws, and the screws may be loosened in the future. To solve this problem, a battery-operated fastening tool disclosed in Japanese Patent Application Laid-Open No. 7-1350 has been proposed. This battery-operated tightening tool is used to determine that the remaining capacity of the battery has dropped below the set remaining capacity when the voltage of the battery drops below the set voltage when starting the motor, and to prevent fastening work due to insufficient torque. Output the auto stop signal to As a result, the FET connected between the battery and the motor is forcibly turned off, and the start of the motor is prohibited even if the operation switch is operated.

[0003]

Normally, the set remaining capacity at which the auto-stop signal is output is determined by tightening due to insufficient torque even when the output timing of the auto-stop signal varies due to variations in the set voltage and battery voltage, battery characteristics, and the like. It is set with some margin to prevent work.
That is, even if the auto stop signal is output,
In many cases, the battery has a remaining capacity that allows the tightening operation to be performed without running out of torque. in this way,
In the conventional battery-operated fastening tool, when an auto-stop signal is output during the fastening operation, the fastening operation is interrupted despite the remaining capacity of the battery, so that the working efficiency is not good. The present invention has been made in order to solve such a problem, and when an auto stop signal is output during the tightening operation, the motor is continuously driven to complete the current tightening operation. Accordingly, it is an object of the present invention to provide a battery-operated fastening tool that can prevent fastening work due to insufficient torque and can improve work efficiency.

[0004]

According to a first aspect of the present invention, there is provided a battery-operated fastening tool according to the first aspect of the present invention. If the battery-operated tightening tool according to claim 1 is used, when the remaining capacity of the battery is smaller than the set remaining capacity at the time of starting the motor, the starting of the motor is prohibited, and the remaining capacity of the battery during driving of the motor is prohibited. If the capacity becomes less than the set remaining capacity, the motor will continue to be driven.
Tightening work due to insufficient torque can be prevented, and the motor is not forcibly stopped during the tightening work and the tightening work is not interrupted. Thereby, work efficiency is improved. According to a second aspect of the present invention, there is provided a battery-operated fastening tool according to the second aspect. If the battery-operated fastening tool according to the second aspect is used, for example, when a shift switch is used as an operation switch, it is possible to appropriately determine that the remaining capacity of the battery has decreased. According to a third aspect of the present invention, there is provided a battery-operated fastening tool according to the third aspect. By using the battery-type fastening tool according to the third aspect, it is possible to accurately determine that the remaining capacity of the battery is lower than the set remaining capacity.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are views showing an embodiment of a battery-operated fastening tool according to the present invention. The battery-type fastening tool according to the present embodiment includes a motor 1, a battery 2, a drive circuit, a remaining capacity detection circuit IC1, and the like. Motor 1
Is supplied with the driving power of the voltage VB from the battery 2 via the contact CN1. A current detecting means for detecting the output current of the battery 2, for example, a current detecting resistor Rs is connected in series to the battery 2. A changeover switch SW1 for switching the rotation direction of the motor 1 is connected to both ends of the motor 1. The changeover switch SW1 has movable contacts a and d and fixed contacts b, c, e, and f. The fixed contacts b and f are connected to a positive voltage line B1, and the fixed contacts c and e are connected to a negative voltage line GND via a control element for controlling driving power to the motor 1, for example, a field effect transistor (FET) Q1. ing. A diode D1 for absorbing a back electromotive voltage of the motor 1 and a switch SW2 are connected between the fixed contacts b and f and the fixed contacts c and e of the switch SW1. Positive voltage line B1 is connected to positive voltage line B2 via switch SW3. The resistors R1 and R2 are connected between the gate of the FET Q1 and the positive voltage line B2. Switch SW
2 and SW3 are configured to operate in conjunction.
For example, while the operation switch for starting the motor 1 is being operated, the switch SW2 is opened and the switch SW3 is opened.
Is closed and the switch S is released when the operation of the operation switch is released.
W3 opens and switch SW2 closes. In addition, the configuration and arrangement position of the switches SW1 to SW3, the arrangement position of the diode D1, the control element, and the like can be variously changed.

The Zener diode ZD1 has a constant voltage V
Supply C. The comparator OP1, the resistors R3 to R7, the capacitor C1, and the like constitute a sawtooth wave generating circuit, and generates a sawtooth voltage VT having a predetermined period and a predetermined voltage. Comparator O
P2 connects the voltage VC to the resistors R8 and R10 and the variable resistor R9.
Supplies a pulse width modulation (PWM) signal corresponding to the result of comparison between the voltage VR divided by the above and the sawtooth voltage VT to the switching element, for example, the base of the transistor Q2. P
The pulse width of the WM signal varies depending on the period and voltage of the sawtooth voltage VT or the voltage divided by the variable resistor R9. When the pulse width of the PWM signal is adjusted by the divided voltage value of the variable resistor R9, the PWM signal may be adjusted manually, or a shift switch may be used as an operation switch, and the shift switch may be adjusted in conjunction with the pull-in operation of the shift switch. May be configured. The collector of the transistor Q2 is connected to the resistors R1 and R
2 connection points. Therefore, the transistor Q2, that is, the FET Q1, can be turned on and off in accordance with the PWM signal output from the comparator OP2.
The FET Q1 can be controlled by various signals other than the PWM signal, and the configuration of the control circuit can be variously changed.

[0007] The comparator OP3 outputs the voltage VC to the resistor R13,
A voltage VF divided by R14 and the capacitor C2 is supplied to the inverting input terminal, and a voltage VE obtained by dividing the voltage VC by the resistors R15 to R17 and the capacitor C3 is supplied to the non-inverting input terminal, and is output when the voltage VE is higher than the voltage VF. The output voltage VG of the terminal is set to the high level “H”, and the voltage VE
Is smaller than the voltage VF, the output voltage VG is set to the low level “L”. A diode D3 having an anode connected to the output terminal of the comparator OP3 and a cathode connected to the base of the transistor Q2 is provided between the output terminal of the comparator OP3 and the base of the transistor Q2. A diode D4 having an anode connected to the non-inverted input terminal and a cathode connected to the output terminal is provided between the non-inverted input terminal and the output terminal of the comparator OP3. When the output voltage VG of the comparator OP3 is “H”, the transistor Q2 is turned on, and the FET Q1 is forcibly turned off. When the output voltage VG of the comparator OP3 is “L”, the transistor Q2 and therefore the FET Q1 are controlled to be turned on and off by the PWM signal output from the comparator OP2. On the other hand, since the diode D4 is provided between the output terminal of the comparator OP3 and the non-inverting input, the comparator OP3
Is "L", the voltage VE of the non-inverting input terminal does not rise above the voltage "L" of the output voltage VG of the comparator OP3.

A diode D2 having the polarity shown is connected to both ends of the resistor R16. The cathode (point A) of the diode D2 is connected to the third terminal of the remaining capacity detection circuit IC1 and to the switching element, for example, the base of the transistor Q20. Transistor Q
The collector of the reference numeral 20 is connected to the tenth terminal of the remaining capacity detection circuit IC1. Terminals 1 and 4 of the remaining capacity detection circuit IC1
A resistor R27 and a light-emitting diode LED20 having the polarity shown in the figure are provided between the first and second terminals. Remaining capacity detection circuit I
When detecting that the remaining capacity of the battery 2 has dropped below the set remaining capacity, C1 outputs a remaining capacity drop signal indicating that the remaining capacity has dropped below the set remaining capacity.

There are various methods for detecting that the remaining capacity of the battery 2 has dropped below the set remaining capacity. The first method is a method for detecting that the voltage of the battery has dropped below the set voltage. This method has a simple circuit configuration and processing. Using this method, for example, when the auto stop signal is output and the battery is forcibly stopped when the remaining capacity of the battery becomes approximately 20% of the full charge capacity, the set voltage is set to the set voltage A as shown in FIG. . However, since there are variations in the set voltage, variations in the battery voltage (battery voltage), and the like, the timing at which the auto stop signal is output varies greatly. In this case, an auto stop signal may be output even though the remaining battery capacity is sufficient. In order to reduce the variation in the timing at which the auto stop signal is output, the set voltage may be set to the set voltage B as shown in FIG. However, when the set voltage is set to the set voltage B, when the auto stop signal is output, there is almost no remaining capacity of the battery. May be performed. Also, if the timing at which the auto stop signal is output is slightly delayed, the battery voltage sharply drops, so that a tightening operation with insufficient torque may be performed. Here, the battery voltage changes according to the discharge current of the battery. When an on-off switch is used as the operation switch, the starting current at the time of starting the motor is substantially the same, so that the lower limit value of the battery voltage at the time of starting the motor is substantially the same. On the other hand, when a speed change switch is used as an operation switch, the lower limit value of the battery voltage at the time of starting the motor is high when the operation switch is slowly operated, so that when the operation switch is rapidly operated, the motor is not operated. Therefore, the lower limit value of the battery voltage at the time of starting the motor becomes lower. For this reason, in a battery-powered tool using a speed change switch as an operation switch, an auto stop signal may not be output properly when the motor is started.

In a second method, a current detection resistor is connected in series with a battery, and the remaining capacity of the battery is determined based on an integral value of a voltage generated between both ends of the resistor. This is a method of detecting that the capacity has dropped. For example, after mounting a remaining capacity detection circuit on a fully discharged battery,
Charge the battery. At this time, the remaining capacity detection circuit integrates the voltage generated at both ends of the current detection resistor for each unit time, and sequentially adds up the sum of the integrated values to obtain the charge amount. Here, if the integrated value before charging is set to “0”, an accurate charge amount can be obtained. On the other hand, when the battery discharges, the voltage generated at both ends of the current detection resistor is integrated for each unit time, and the integrated value is added to determine the amount of discharge. The state of charge or the state of discharge of the battery can be determined by the polarity of the voltage generated across the current detection resistor. Then, the remaining capacity of the battery is determined by subtracting the amount of discharge from the amount of charge. This method obtains the amount of charge charged to the battery and the amount of discharge discharged from the battery by integrating the voltage generated across the current detection resistor.
The remaining capacity of the battery can be accurately determined. On the other hand, when the battery approaches the end of its life and the full charge capacity of the battery decreases as shown by a solid line in FIG. 7, for example, a difference occurs between the remaining capacity of the battery detected by this method and the actual remaining capacity of the battery. , An appropriate auto stop signal is not output. To prevent this, it is necessary to learn and store the full charge capacity of the battery according to the number of times of use of the battery and to determine the remaining capacity of the battery based on the full charge capacity of the battery each time. To determine the full charge capacity of a battery, it is necessary to completely discharge the battery once. However, in the battery-type fastening tool with an auto-stop function, the battery cannot be completely discharged because the auto-stop function works before the battery is completely discharged. For this reason, in order to accurately determine the full charge capacity of the battery, it is necessary to completely discharge the battery using a discharging device or the like every set period, for example. When a method of detecting that the remaining capacity of the battery is lower than the set remaining capacity due to the lowering of the battery voltage than the set voltage is used, as shown in FIG. 7, the full charge capacity of the battery decreases. However, there is little variation in the timing at which the auto stop signal is output.
That is, the timing at which the auto-stop signal is output when using a battery with a reduced full charge capacity or a battery with a slightly lower battery voltage, as indicated by the solid line, uses a new battery, as indicated by the broken line. This is almost the same as the timing when the auto stop signal is output.

In a third method, an output current output from the battery to the motor, that is, a set voltage corresponding to the discharge current of the battery is read from a storage circuit and set, and the voltage of the battery falls below the set voltage. This is a method for detecting that the remaining capacity of the battery is lower than the set remaining capacity. For example, while dividing into a plurality of current value ranges, a set voltage corresponding to each current value range is prepared, and a set voltage corresponding to each current value range is selected and set. As described above, when the speed change switch is used as the operation switch, the starting current of the motor changes according to the operation speed of the speed change switch, and the lower limit value of the battery voltage at the time of starting the motor changes. That is, when the shift switch is operated slowly, the set speed of the motor gradually increases, so that the starting current of the motor is small and the lower limit voltage of the battery is high. On the other hand, when the shift switch is rapidly operated, the set speed of the motor is instantaneously increased, so that the starting current of the motor is large and the lower limit voltage of the battery is low. FIG. 8 shows the characteristics of the battery voltage according to the discharge current of the battery. In FIG. 8, the solid line indicates that the discharge current is between 0 and 1.
The characteristics at 0 A are shown.
0A shows the characteristics when the discharge current is 20 A
The characteristics in the case of ３０30 A are shown. As described above, since the rate of decrease in battery voltage changes depending on the discharge current of the battery, when the set voltage is set based on a certain discharge current, the voltage of the battery greatly decreases when the discharge current is larger than a certain discharge current. Therefore, the remaining capacity reduction signal may be output even though the remaining capacity of the battery is equal to or greater than the set remaining capacity. Thus, for example, when the discharge current of the battery is 0 to 10 A, the set voltage is 1, when the discharge current is 10 A to 20 A, the set voltage is 2, and when the discharge current is 20 A to 30 A, the set voltage is 3. By setting the set voltage according to the discharge current of the battery, it is possible to prevent the erroneous output of the remaining capacity reduction signal even though the remaining capacity of the battery is equal to or greater than the set remaining capacity. By using this method, it is possible to appropriately output an auto-stop signal at the time of starting the motor when using the speed change switch or during driving of the motor.

In the present embodiment, the remaining capacity detection circuit IC1
Determines the remaining capacity of the battery based on the charge / discharge current of the battery 2, detects that the determined remaining capacity of the battery has dropped below the set remaining capacity, and determines the voltage of the battery 2 in accordance with the discharge current of the battery. It is detected that the remaining capacity of the battery has dropped below the set remaining capacity due to a drop below the set voltage. That is, the remaining capacity of the battery 2 is determined based on the charging / discharging current of the battery 2 by the method described above, and when the determined remaining capacity is 80% or more of the full charge capacity, the terminals 3 to 6 are connected to GND, and When less than 60% or more, terminal 6, 60%
Terminals 5 and 6 when less than 40% or more, less than 40%
The terminals 4 to 6 are opened when it is 20% or more, and the terminals 3 to 6 are opened when it is less than 20%. When the voltage of the battery 2 falls below a set voltage set according to a plurality of current value ranges, the terminals 3 to 6 are opened. In the present embodiment, when the terminal 3 of the remaining capacity detection circuit IC1 is opened, the remaining capacity detection signal is output from the remaining capacity detection circuit IC1. Since the voltage of the terminal 1 of the remaining capacity detection circuit IC1 is the same as the power supply voltage of the IC1, when the terminal 4 is connected to GND, LE is applied.
D20 is lit to indicate that the remaining capacity of the battery 2 is 40% or more, and when the terminal 4 is opened, the LED 20 is turned off to indicate that the remaining capacity of the battery 2 is less than 40%.
Further, the remaining capacity detection circuit IC1 of the present embodiment normally has the terminals 3 to 6 open. When the switch SW3 is closed by operating the operation switch and the transistor Q20 is turned on and the terminal 10 is connected to GND, the terminals 3 to 6 are connected or opened to GND according to the remaining capacity of the battery 2. Further, when the operation of the operation switch is released and the switch SW3 is opened, the transistor Q20 is turned off and the connection between the terminal 10 and GND is cut off, the terminals 3 to 6 are opened in a normal state, that is, open. Thus, when the trigger of the operation switch is not pulled, that is, when the switch SW3 is open, the terminals 3 to 6 are opened to reduce the power consumption of the remaining capacity detection circuit IC1 as much as possible, and So that you can use it for a long time. The configuration of the remaining capacity detection circuit IC1, the arrangement position of the indicator lamp, and the like can be appropriately changed.

Next, the operation of this embodiment will be described. First, an operation when the operation switch is operated in a state where the remaining capacity of the battery 2 is 70%, which is more than 20% of the full charge capacity, will be described with reference to a signal waveform diagram shown in FIG.
It is assumed that the changeover switch SW1 is selected in a predetermined rotation direction. When the operation switch is operated, the switch SW2 opens and the switch SW3 closes. Thereby, a sawtooth wave is generated from the sawtooth wave generation circuit, and the comparator OP
2 outputs a PWM signal. Here, when a shift switch is used as the operation switch, the switch SW2 is opened and the switch SW3 is closed by the pull-in operation of the shift switch. Then, the resistance value of the variable resistor R9 changes according to the amount of pull-in of the shift switch,
The pulse width of the PWM signal output from the comparator OP2 changes. When the pulse width of the PWM signal changes, the rotation speed of the motor 1 changes. Also, switch S
When W3 is closed, charging of the capacitors C2 and C3 starts. Here, the resistors R13 to R17 and the capacitor C
2, The values of C3 are set so as to satisfy the following conditions. That is, (1) the voltage VE rises earlier than the voltage VF when the capacitors C2 and C3 start charging at the same time, and (2) the terminal 3 of the remaining capacity detection circuit IC1 is open, that is, the point A is open. (3) the remaining capacity detection circuit IC1 so that the voltage VE becomes higher than the voltage VF when the charging of the capacitors C2 and C3 is completed.
When the terminal 3 is connected to GND, that is, when the point A is connected to GND via the resistor R20, the voltage at the point A becomes lower than when the terminal is open, and the charging of the capacitors C2 and C3 ends. In this state, the voltage VE is set to be lower than the voltage VF. For this reason, charging of the capacitors C2 and C3 is started, and the voltage VE becomes the voltage V
Until time t3 when the voltage becomes smaller than F, the voltage VG of the comparator OP3 becomes VH indicating "H". When the voltage VG becomes "H", the transistor Q2 is turned on, so that the FET Q1 remains off.

After the switch SW3 is closed, the voltage at the point A rises and the transistor Q20 is turned on, so that the terminal 10 of the remaining capacity detection circuit IC1 is connected to GND. When the terminal 10 is connected to GND, the remaining capacity detection circuit IC1 determines whether the remaining capacity of the battery 2 is smaller than the set remaining capacity. That is, it is determined whether the voltage of the battery 2 is lower than a set voltage corresponding to the current output from the battery 2 to the motor 1. Further, the remaining capacity of the battery 2 is detected based on the integrated value of the current output from the battery 2 until then. In this case, the remaining capacity of the battery is 70% of the full charge capacity.
%, And since the voltage of the battery 2 is higher than the set voltage, the remaining capacity detection circuit IC1 opens the terminal 6,
Terminal 5 is connected to GND. Terminal 3 is GND at time t2
, And the point A is connected to GN via the resistor R20.
When connected to D, the capacitor VE discharges via the diode D2, so that the voltage VE decreases. The charging voltage of the capacitor C3 is the voltage VC and the resistances R15, R16, R
17, determined by R20. Then, when the voltage VE becomes lower than the voltage VF at the time point t3, the voltage VG of the comparator OP3 changes from VH to VL indicating “L”, and the transistor Q2 and therefore the FET Q1 are turned on by the PWM signal output from the comparator OP2. The control is turned off, and the motor 1 is started in a predetermined direction. Note that the period from the time point t1 to the time point t3 is set to be short enough not to impair operability. When the operation of the operation switch is released, the switch SW2 closes and the switch SW3 opens, so that the motor 1 stops. When the operation of the operation switch is released, the transistor Q20 is turned off, and the terminal 10 of the remaining capacity detection circuit IC1 is opened.

Next, the operation when the operation switch is operated when the remaining capacity of the battery 2 becomes smaller than a set remaining capacity, for example, 20% of the full charge capacity, will be described with reference to a signal waveform diagram shown in FIG. When the operation switch is operated and the switch SW2 is opened and the switch SW3 is closed, the PWM signal is output from the comparator OP2 as described above. At the same time, charging of the capacitors C2 and C3 is started, and the voltage VE becomes the voltage V
At time t11 when the voltage becomes larger than F, the voltage VG of the comparator OP3 becomes the voltage VH indicating “H”. Thereby, FE
TQ1 remains off. When the switch SW3 is closed, the transistor Q20 is turned on and the terminal 10 of the remaining capacity detection circuit IC1 is connected to GND in the same manner as described above, so that the remaining capacity detection circuit IC1 indicates that the remaining capacity of the battery is equal to the set remaining capacity. It is determined whether or not the remaining capacity is lower by determining the remaining capacity based on the output current or the like output from the battery 2 and determining whether or not the voltage of the battery 2 is lower than a set voltage corresponding to the output current of the battery 2. to decide. In this case, whether the remaining capacity of the battery is less than 20% of the full charge capacity,
Alternatively, if the voltage of the battery 2 is lower than the set voltage, the remaining capacity detection circuit IC1 opens the terminals 3 to 6. Therefore, the voltage VG of the comparator OP3 is kept at “H”. Therefore, the FET Q1 remains off, and the starting of the motor is prohibited. The remaining capacity detection circuit IC1 determines that the remaining capacity of the battery 2 is smaller than the set remaining capacity based on the output current of the battery 2 or the like, or that the voltage of the battery 2 is equal to the set voltage corresponding to the output current. If it is determined that the remaining capacity is lower, that is, if it is determined that the remaining capacity is lower than the set remaining capacity, the terminal 3 is opened. When the operation of the operation switch is released, the switch SW
2 is closed and the switch SW3 is opened. Further, the transistor Q20 is turned off, and the terminal 10 of the remaining capacity detection circuit IC1 is opened.

Next, the operation when the remaining capacity of the battery 2 is larger than the set remaining capacity when the operation switch is operated, but the remaining capacity of the battery 2 becomes smaller than the set remaining capacity while the motor is being driven will be described with reference to FIG. This will be described with reference to signal waveform diagrams shown in FIG. The case where the remaining capacity of the battery 2 becomes smaller than the set remaining capacity during driving of the motor is, for example, the case where the remaining capacity of the battery 2 when the operation switch is operated is slightly larger than the set remaining capacity.
When the operation switch is operated and the switch SW2 is opened and the switch SW3 is closed, the comparator OP2 is operated as described above.
Thus, a PWM signal is output. At the same time, charging of the capacitors C2 and C3 is started, and at time t21 when the voltage VE becomes higher than the voltage VF, the voltage VG of the comparator OP3 becomes “H”.
, And the FET Q1 remains off. Further, the transistor Q20 is turned on as described above, and the terminal 10 of the remaining capacity detection circuit IC1 is connected to GND. When the terminal 10 is connected to GND, the remaining capacity detection circuit IC1 determines whether the remaining capacity of the battery is smaller than the set remaining capacity. In this case, when the operation switch is operated, the remaining capacity of the battery 2 detected based on the output current or the like of the battery 2 is equal to or more than the set remaining capacity, and the voltage of the battery 2 is higher than the set voltage. 3 is connected to GND. Thus, at time t23 when the voltage VE becomes lower than the voltage VF, the voltage VG of the comparator OP3 changes from “H” to “L”, and the transistor Q2 and therefore the FET Q
1 is turned on and off in accordance with the PWM signal output from the comparator OP2, and the motor 1 starts.

While the motor 1 is being driven, at time t24 the battery 2
When the remaining capacity of the battery 2 calculated based on the output current of the battery 2 falls below the set remaining capacity or the voltage of the battery 2 falls below the set voltage, the remaining capacity detection circuit IC1 opens the terminal 3. Thereby, charging of the capacitor C3 is started, and the voltage VE
Rises. However, the voltage VG of the comparator OP3 is the voltage VL indicating “L”, and the voltage of the comparator OP3 is
Since the diode D4 is provided between the inverting input and the output, the voltage VE does not rise above the voltage VL. That is, the voltage VE does not become higher than the voltage VF, and the voltage VG of the comparator OP3 does not become “H”. For this reason, even if the remaining capacity of the battery 2 becomes smaller than the set remaining capacity while the motor 1 is being driven, the automatic stop signal is not output, and the fastening operation is not interrupted. In this case, when the operation switch is operated next time, it is detected that the remaining capacity is smaller than the set remaining capacity, an auto stop signal is output, and the start of the motor 1 is prohibited.

In the above embodiment, the remaining capacity detection circuit I
C1 is based on a method of detecting that the remaining capacity of the battery 2 has become smaller than the set remaining capacity based on the output current of the battery 2 and the like, and on the basis of a set voltage corresponding to the output current output from the battery 2 to the motor 1. Although the detection method was used, only one of the methods may be used, another method may be used, or a plurality of methods may be used in combination.
By using a plurality of methods in combination, an auto stop signal can be output with higher accuracy. Further, the configuration of the battery-operated fastening tool of the present invention is not limited to the configuration shown in FIGS. 1 and 2 and can be variously changed. For example, the remaining capacity detection circuit only needs to detect that the remaining capacity of the battery 2 has become smaller than the set remaining capacity. The circuit that outputs the auto stop signal enables the motor to start when the remaining charge of the battery is larger than the set remaining capacity when the operation switch is operated, and starts the motor when the remaining capacity of the battery is smaller than the set remaining capacity. It is only necessary to prohibit start-up and continue driving the motor if the remaining capacity of the battery becomes smaller than the set remaining capacity while the motor is being driven. The changeover switch SW1, the switches SW2, SW3, and the like may have a function of switching the rotation direction of the motor 1, a function of supplying and shutting off power to the motor 1, and a function of stopping the motor 1.

[0019]

As described above, the use of the battery-operated tightening device according to the first aspect can prevent the tightening operation due to insufficient torque and force the motor during the tightening operation. Work efficiency is improved. Further, if the battery-operated fastening tool according to the second aspect is used, it is easily determined that the remaining capacity of the battery is lower than the set remaining capacity even with a battery-operated fastening tool having a shift switch. be able to. Further, if the battery-operated fastening tool according to claim 3 is used, even if the battery-operated fastening tool with a speed change switch is used, an auto-stop signal can be output with high accuracy even for a battery whose life is near the end, Work efficiency also improves. Further, if the voltage of the battery falls below a set voltage set according to the discharge current of the battery before the remaining capacity based on the discharge current of the battery falls below the set remaining capacity, the life of the battery or the actual capacity temporarily decreases. The decrease can be easily determined, and the operator can be notified of the decrease by a display or a buzzer attached to the battery. Alternatively, by communicating between the battery and the charger, it is possible to notify the worker that the life of the battery in the charger or the actual capacity is temporarily reduced.

[Brief description of the drawings]

FIG. 1 is a main part circuit diagram of a battery-operated fastening tool of the present invention.

FIG. 2 is a main part circuit diagram of the battery-operated fastening tool of the present invention.

FIG. 3 is a signal waveform diagram when the remaining capacity of the battery is larger than a set remaining capacity.

FIG. 4 is a signal waveform diagram when the remaining capacity of the battery is smaller than a set remaining capacity.

FIG. 5 is a signal waveform diagram when the remaining capacity of the battery becomes smaller than a set remaining capacity during a fastening operation.

FIG. 6 is a battery voltage-remaining capacity characteristic diagram.

FIG. 7 is a battery voltage-remaining capacity characteristic diagram.

FIG. 8 is a diagram showing characteristics of a battery according to a discharge current.

[Explanation of symbols]

 Reference Signs List 1 motor 2 battery Q1 FET (drive element) Q2, Q20 transistor (switching element) SW1 to SW3 switch OP1 to OP3 comparator IC1 remaining capacity detection circuit D1 to D5 diode R1 to R17, R20 to R25, Rs resistor C1 to C3 capacitor LED20 light emitting diode

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Junichi Nishimi 3-11-8 Sumiyoshicho, Anjo City, Aichi Prefecture Inside Makita Co., Ltd. (72) Inventor Ikuo Takenaka 3-11-8 Sumiyoshicho, Anjo City, Aichi Prefecture Stock F-term in the company Makita (reference) 3C038 AA01 BC04 CA05 CC03 CC08 EA06

Claims (3)

[Claims] 1. A driving device comprising: a battery; a remaining capacity detection circuit that outputs a remaining capacity reduction signal when a remaining capacity of the battery is lower than a set remaining capacity; a motor; and a driving circuit that drives the motor. The circuit prohibits the start of the motor when the remaining capacity reduction signal is output from the remaining capacity detection circuit when the motor starts, and the remaining capacity reduction signal is output from the remaining capacity detection circuit when the motor starts. A battery-operated fastening tool that starts the motor when the output is not output, and continues driving the motor when a remaining capacity reduction signal is output from the remaining capacity detection circuit during driving of the motor. 2. The battery-operated fastening tool according to claim 1, wherein the remaining capacity detection circuit is configured to reduce the remaining capacity when the voltage of the battery drops below a set voltage corresponding to a discharge current of the battery. Battery-operated fastening tool that outputs a signal. 3. The battery-operated fastening tool according to claim 1, wherein the remaining capacity detection circuit detects a remaining capacity of the battery based on a charging / discharging current of the battery, and detects the remaining battery. A battery-operated fastening tool that outputs the remaining capacity reduction signal when the remaining capacity of the battery is lower than a set remaining capacity.