JP2005001039A - Switch for power tool, and power tool using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switch for a power tool and a power tool using the same, which switch has a function for warning a decrease in residual capacity of a battery, the function being easily understandable for an operator, and can prevent an over-discharge of the battery. <P>SOLUTION: The switch 31 for the power tool comprises a trigger 3 interlocked with a sliding contact point 5, a PWM control section 6 for outputting a PWM signal Vp according to a voltage V1 of the sliding contact point and a reference voltage V2, a battery residual capacity judging section 7 which judges the residual capacity of a rechargeable battery 2 by detecting the voltage Vb of the battery and outputs a port output Vm, and a switching element 13 for driving a motor 1 by a switching control signal Vo according to the PWM signal Vp and the port output Vm. The switch 31 is configured such that the motor 1 is driven by the PWM signal Vp under usual conditions, and when the residual capacity of the rechargeable battery 2 has become smaller than a first required value, the maximum rotational speed at the maximum pulled value of the trigger 3 is fixed so as to be operable and to be lower than the maximum speed, and further when the residual capacity of the rechargeable battery 2 has become smaller than a second required value, the motor 1 is cut off from the rechargeable battery 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
[Technical field to which the invention belongs]
TECHNICAL FIELD The present invention relates to a power tool switch and a power tool using the same circuit, and more particularly to a power tool switch that can be perceived by changing the number of revolutions of a motor when the remaining capacity of a power battery of the power tool is reduced. And an electric tool using the same circuit.
[0002]
[Prior art]
Electric tools using a rechargeable battery or the like as a power source take advantage of being cordless and are used very often. However, there is always a problem that the battery runs out. For this reason, the remaining capacity is calculated and stored by detecting the current flowing into and out of the battery, and a light emitting diode (LED) is provided on the battery body to display a predetermined display according to the remaining capacity, thus preventing the battery from running out in advance. This method is employed (see, for example, Patent Document 1).
[0003]
[Patent Document 1]
JP-A-8-171360 (2nd page, FIG. 2)
[0004]
[Problems to be solved by the invention]
However, in actual work, if the remaining amount display is confirmed every time when working, work efficiency deteriorates. Moreover, if it continues using it in the state in which the battery remaining charge fell, a battery will be in an overdischarge state and the charging / discharging cycle life of a battery will deteriorate. Furthermore, when the operation becomes impossible during the operation without recognizing the decrease in the remaining battery level, there may be a problem that the operation cannot be performed properly.
[0005]
SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a rechargeable battery remaining capacity decrease warning function that is easier for an operator to understand, to improve work efficiency, and to prevent battery overdischarge.
[0006]
[Means for Solving the Problems]
The present invention, which has been made to achieve the above object, includes a rotation speed instruction means for instructing the rotation speed of a motor that is a drive source of the electric tool, a detection means for detecting a voltage of a battery that is a power source of the electric tool, Comparing means for comparing the voltage of the battery detected by the detecting means with a predetermined voltage, and remaining capacity determination for determining whether or not the remaining capacity of the battery is less than a predetermined remaining capacity according to the output of the comparing means And a rotation speed control means for controlling the rotation speed of the motor in accordance with the output from the rotation speed instruction means and the output from the remaining capacity determination means. When the capacity determination means determines that the remaining capacity of the battery is less than the first capacity, the rotation speed control means can perform a predetermined operation with the electric tool, with the maximum rotation speed of the motor, and The rotation speed instruction means A switch for an electric tool and outputs the speed control signals to the first rotational speed of less than Shimesuru maximum speed.
[0007]
In the power tool switch described above, an instruction from the rotation speed instruction means and an output from the remaining capacity determination means for determining whether or not the battery voltage detected by the detection means is less than a predetermined voltage. Therefore, the rotation speed control means controls the rotation speed of the motor. When the remaining capacity of the battery falls below the first capacity, the maximum number of rotations of the motor is limited to a predetermined number.
[0008]
When the remaining capacity determining means determines that the remaining capacity of the battery is greater than or equal to the first capacity, the rotational speed control means sets the rotational speed of the motor to the rotational speed indicated by the rotational speed instruction means. It is preferable.
[0009]
Further, when the remaining capacity determining means determines that the remaining capacity of the battery is less than the second capacity smaller than the first capacity, the rotation speed control means can stop the rotation of the motor.
[0010]
From another point of view, the present invention controls the start and stop of the electric tool, moves the sliding contact, a variable resistor to which the sliding contact is movably connected, and the drive source of the electric tool. A detecting means for outputting a signal for temporarily stopping the motor and detecting a voltage of a battery as a power source of the electric tool every first predetermined time during a period in which the motor is stopped; and When the detected voltage of the battery is less than a predetermined voltage continuously for a predetermined number of times, a remaining capacity determination means for determining that the remaining capacity of the battery is less than a predetermined capacity, and sliding at the sliding contact of the variable resistor A rotation speed control signal output means for outputting a rotation speed control signal for controlling the rotation speed of the motor according to a contact voltage and an output of the remaining capacity determination means, and based on the rotation speed control signal, the battery and the Mo Switching means for intermittently connecting the motor and changing the number of revolutions of the motor, and is built in the electric power tool body, and the remaining capacity determining means reduces the remaining capacity of the battery to less than the first capacity. The remaining capacity determination means outputs a signal for disconnecting the connection between the motor and the power source for a predetermined time of the first predetermined time, and determines the maximum rotational speed of the motor, A switch for an electric tool characterized in that a predetermined work by the electric tool is possible and the rotational speed of the motor is reduced as a first rotational speed less than a maximum rotational speed indicated by the sliding contact voltage. is there.
[0011]
In the power tool switch, the trigger starts and stops the power tool, moves the sliding contact, and changes the sliding contact voltage at the variable resistance sliding contact. The detecting means detects the battery voltage by temporarily stopping the motor every first predetermined time. The remaining capacity determining means determines whether or not the remaining capacity of the battery is less than a predetermined capacity from the detected voltage of the battery. When the remaining capacity of the battery is less than the first capacity, the remaining capacity determination means outputs a signal for disconnecting the connection between the motor and the power source for a predetermined time of the first predetermined time. Decreases at a predetermined rate.
[0012]
When the remaining capacity determining means determines that the remaining capacity of the battery is greater than or equal to the first capacity, the rotational speed control means sets the rotational speed of the motor to the rotational speed indicated by the sliding contact voltage. The rotation speed control signal is preferably output.
[0013]
In addition, when the remaining capacity determination unit determines that the remaining capacity of the battery is less than the first capacity, the remaining capacity determination unit determines that the remaining capacity is less than a second capacity that is smaller than the first capacity. In the case where it is determined whether or not the remaining capacity is less than the second capacity, the switching means can also disconnect the connection between the battery and the motor.
[0014]
According to still another aspect, the present invention is an electric tool that is driven by a motor and has any one of the electric tool switches described above.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a power tool switch and a power tool using the same circuit according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5. In the present embodiment, an electric driver will be described as an example of the electric tool.
[0016]
FIG. 1 is a cross-sectional view showing an electric driver 100 incorporating a switch according to the present embodiment. As shown in FIG. 1, the electric driver 100 includes a motor 1, a rechargeable battery 2, a trigger 3, a switch 31, a forward / reverse switching lever 32, a drive mechanism 33, a housing 34, a tip tool 35, and the like. Although not shown, the electric screwdriver 100 performs screw tightening work by fitting a screw and a tip tool 35 attached to the electric screwdriver 100.
[0017]
The motor 1 is a drive source of the electric driver 100. The rechargeable battery 2 is a power source for the electric driver 100. The trigger 3 starts and stops the electric driver 100 by pressing in the left direction in FIG. 1 and instructs the rotation speed of the motor 1 by the moving distance moved by the pressing (hereinafter referred to as trigger pulling amount).
[0018]
The switch 31 is connected between the motor 1 that is a drive source of the electric driver 100 main body and the rechargeable battery 2 that is a power source of the electric driver 100 main body. The switch 31 is provided with a trigger 3, and the operator presses the trigger 3 in the left direction in FIG. 1, thereby instructing the start and stop of the electric driver 100 main body and the speed change operation of the motor 1.
[0019]
The forward / reverse switching lever 32 is an operation unit that switches the rotation direction of the motor 1. The drive mechanism 33 is a mechanism that transmits the driving force of the motor 1 to the tip tool 35. The housing 34 houses the motor 1, the rechargeable battery 2, the trigger 3, the switch 31, the forward / reverse switching lever 32, the drive mechanism 33, and the like. The tip tool 35 is the tip of the driver in the example of FIG. 1 and rotates in conjunction with the rotation of the motor 1.
[0020]
As shown in FIG. 2, the switch 31 includes a main contact 4, a sliding contact 5, a PWM control unit 6, a battery remaining amount detection unit 7, a diode 14, and a forward / reverse switching contact 15.
[0021]
The trigger 3 is interlocked with the main contact 4 and the sliding contact 5 inside the switch 31. The main contact 4 is a contact to be connected when the trigger 3 instructs the activation of the electric driver 100.
[0022]
The PWM control unit 6 includes a sliding contact 5, a variable resistor R, a comparison circuit 16, an oscillation circuit 17, and the like. The sliding contact 5 is connected to the variable resistor R so as to divide the voltage of the rechargeable battery 2, moves in conjunction with the instruction of the trigger 3, and the sliding contact voltage V 1 divided by the sliding contact 5 is It changes according to the movement of the sliding contact 5.
[0023]
The oscillation circuit 17 outputs a reference voltage V2 that varies at a predetermined cycle. The comparison circuit 16 compares the sliding contact voltage V1 with the reference voltage V2, outputs a PWM signal Vp, and indicates the rotation speed of the motor 1. The PWM signal Vp will be described later. The trigger 3 and the PWM control unit 6 correspond to a rotation speed instruction unit.
[0024]
The battery remaining amount detection unit 7 is configured around a microcomputer 8 (hereinafter referred to as “microcomputer 8”), and includes a power supply circuit 9, a battery voltage detection unit 10, a warning LED 11, and the like.
[0025]
The microcomputer 8 has a CPU 81, ROM 82, RAM 83, A / D converter 84, timer 85, output port 86, and reset circuit 87. The CPU 81, the ROM 82, and the RAM 83 correspond to comparison means and remaining capacity determination means, and perform comparison calculation of the battery voltage Vb. The A / D converter 84 A / D converts the battery voltage Vb detected by the battery voltage detection unit 10. The timer 85 sets time such as the detection time of the battery voltage Vb and the switching time of the port output Vm. The reset circuit 87 initializes a timer 85, a counter (not shown), and the like. The output port 86 outputs a port output Vm obtained by comparing and calculating the detected battery voltage Vb. The battery voltage detector 10 detects the battery voltage Vb. The warning LED 11 is a warning means that blinks when the remaining battery capacity is determined to be less than a predetermined value. The battery voltage detection unit 10, the A / D converter 84, the timer 85, and the reset circuit 87 correspond to detection means.
[0026]
The AND circuit 12 corresponds to rotation speed control signal output means, performs a logical product operation on the inputs of the PWM signal Vp and the port output Vm, and outputs a switch control signal Vo.
[0027]
The switching element 13 corresponds to switching means, and is a transistor that controls the rotational speed of the motor 1 by intermittently connecting the motor 1 and the rechargeable battery 2 based on the switch control signal Vo. The rotation speed control signal output means and the switching means function as the rotation speed control means.
[0028]
The diode 14 is a diode for absorbing a surge voltage generated when the switching element 13 is turned off. The forward / reverse switching contact 15 is a forward / reverse switching contact for switching the rotation direction of the motor 1, and the forward / reverse switching lever 32 is interlocked with the forward / reverse switching contact 15.
[0029]
Next, the operation of the electric driver 100 during actual work will be described. When the operator pulls the trigger 3 in the electric driver 100, the main contact 4 is closed first, the PWM control unit 6 that is the rotation speed instruction means, the detection means for detecting the voltage of the rechargeable battery 2, and the output of the detection means are predetermined. Energization is started to the battery remaining amount detection part 7 which functions as a comparison means for comparing with the value.
[0030]
As shown in FIG. 3A, the PWM control unit 6 compares the sliding contact voltage V1 divided by the sliding resistance 5 with the reference voltage V2, and determines the PWM signal Vp shown in FIG. Output. The reference voltage V2 is a sawtooth wave with a period T1. The sliding contact voltage V <b> 1 changes as the sliding contact 5 moves according to the pulling amount of the trigger 3. When the reference voltage V2 is equal to or higher than the sliding contact voltage V1, the comparison circuit 16 outputs a high level voltage (hereinafter also simply referred to as “H”). When the reference voltage V2 is less than the sliding contact voltage V1, the comparison circuit 16 outputs a low level voltage (hereinafter also simply referred to as “L”).
[0031]
As described above, the PWM signal Vp is output according to the magnitude relationship between the reference voltage V2 and the sliding contact voltage V1, and accordingly, the duty Dp (= (t1 / T1) × 100) (%) of the PWM signal Vp. Changes to generate a rotation number instruction signal of the motor 1. Here, the time t1 is a time during which the reference voltage V2 becomes equal to or higher than the sliding contact voltage V1. When the trigger is fully pulled, the state of V2> V1 is always established, and the duty Dp is 100%.
[0032]
FIG. 4 shows a flowchart of the microcomputer 8 in the battery remaining capacity detection unit 7. When the operator pulls the trigger 3 and the main contact 4 is closed and energization is started, the reset is performed by the reset circuit 87 built in the microcomputer 8. After reset is released, battery remaining capacity detection is started.
[0033]
During the reset period, the output port 86 is in a high impedance state, and the port output Vm of the battery remaining capacity detection unit 7 is maintained in the H state by a pull-up resistor. Therefore, during the reset period, the switching element 13 is repeatedly turned on and off by the PWM signal Vp of the PWM control unit 6.
[0034]
After the reset is released, in the main routine shown in FIG. 4A, first, initialization such as clearing of the flags in the RAM 83 and the microcomputer 8 is performed (step 401). Next, the timer 85 is set to a value corresponding to the time T2 shown in FIG. 3, and a timer interrupt is started. After the start of the timer interrupt, whenever the time T2 elapses, the microcomputer 8 is interrupted by a timer interrupt and branches to the battery remaining capacity detection routine (step 402).
[0035]
In the battery remaining capacity detection routine shown in FIG. 4B, the port output Vm is set to L, the switching element 13 is turned off, and the power supply to the motor 1 is temporarily stopped (step 421). When power supply to the motor 1 is stopped, a surge voltage is generated in Vb obtained by dividing the battery voltage by the counter electromotive force from the motor as shown in FIG. Therefore, the process waits for a time ts when the surge voltage is generated and a time td until the battery voltage is stabilized (step 422). At this time, the battery is almost in a no-load state, and it becomes possible to measure a stable battery voltage as compared with a state in which the switching element 13 is turned on and the motor 1 is fed and the load fluctuates.
[0036]
Next, the battery voltage Vb obtained by dividing the battery voltage by the A / D converter 84 is sampled (step 423). When the sampled battery voltage Vb is lower than the first predetermined value Vb1 (step 424, YES), first, the remaining amount reduction flag is checked. If the remaining amount reduction flag is not raised (step 425, NO), the remaining amount reduction flag is set (step 426), and the battery remaining amount reduction counter is incremented (step 427).
[0037]
When the battery remaining amount reduction flag is set (step 425, YES), the remaining amount reduction counter is incremented (step 427). If the sampled battery voltage Vb exceeds the first predetermined value Vb1 (NO in step 424), the battery remaining amount decrease flag and the battery remaining amount decrease counter are cleared (step 428). Finally, the port output Vm is set to H, the switching element 13 is turned on, and the power supply to the motor 1 is resumed (step 429).
[0038]
The time for processing the timer interrupt routine corresponds to the time t2 in FIG. 2, and the duty D in which the switching element 13 is turned on when the trigger 3 is fully pulled is (1-t2 / T2) × 100 (%). . At this time, for example, the time T2 is set so that the duty D becomes 98%.
[0039]
In the main routine, the remaining battery level counter is constantly monitored, and when the remaining capacity counter reaches a predetermined value, for example, 8 (step 403, YES), the remaining battery level warning LED 11 starts blinking (step 403). 404), the timer interrupt is once canceled (step 405). Next, a value corresponding to, for example, 70% of the time T2 is reset in the timer, and a timer interrupt for speed limit when the remaining battery power is low is started, that is, the process branches to a speed limit interrupt routine (step 406).
[0040]
In the speed limiting interrupt routine shown in FIG. 4C, first, the port output Vm is set to L, the switching element 13 is turned off, and the power supply to the motor 1 is stopped (step 431).
[0041]
After waiting for time (ts + td) (step 432), the battery voltage Vb obtained by dividing the battery voltage by the A / D converter 84 is sampled (step 423). When the sampled battery voltage Vb is lower than the second predetermined value Vb2 (step 434, YES), the no remaining amount flag is checked. When the no remaining amount flag is not raised (step 435, NO), the remaining amount flag is set (step 436), and the no battery counter is incremented (step 437).
[0042]
If the battery remaining amount flag is set (step 435, YES), the remaining amount counter is incremented (step 437). If the sampled battery voltage Vb exceeds the second predetermined value Vb2 (step 434, NO), the remaining battery level flag and the remaining battery level counter are cleared (step 438). Next, after waiting for a value tw obtained by subtracting the processing time of the interrupt routine from the time corresponding to 30% of time T2 (step 439), the port output Vm is finally set to H, the switching element 13 is turned on, and the motor 1 is turned on. The power supply is resumed (step 440).
[0043]
In this example, the duty D when the trigger 3 is fully pulled by this speed limiting interrupt routine is fixed to 70%, and the operator recognizes that the remaining battery level is low due to the obvious difference in motor rotation speed. be able to. On the other hand, the screw tightening operation by the electric screwdriver 100 can be performed even when the rotational speed is slowed as described above.
[0044]
In the main routine, the remaining battery counter is constantly monitored, and when the remaining battery counter reaches a predetermined value, for example, 8 (step 407, YES), it is determined that the battery is dead and the remaining battery low warning LED is turned on. (Step 408), in order to prevent overdischarge of the battery, the port output Vm is finally set to L, the battery switching element 13 is turned off, the tool is stopped (Step 409), and the rechargeable battery is overdischarged. Can be prevented in advance.
[0045]
As described above in detail, according to the switch 31 and the electric driver 100 according to the present embodiment, the battery voltage Vb is compared with the predetermined voltage Vb1 at regular intervals, and as a result, the battery voltage Vb is continuously applied a predetermined number of times. Is lower than the voltage Vb1, it is determined that the remaining capacity of the battery has decreased, and the rotation of the motor 1 is decreased at a predetermined rate. Thereby, the operator of the electric driver 100 can recognize that the remaining capacity of the battery has been reduced.
[0046]
When the battery voltage Vb is lower than the voltage Vb2 lower than the voltage Vb1, the switching element 13 disconnects the connection between the motor 1 and the rechargeable battery 2 and stops the driving of the electric driver 100. Thereby, it can prevent that a battery will be in an overdischarge state.
[0047]
Further, since the switch 31 having the function of warning the battery remaining level is provided in the electric driver 100 body as described above, when the rotation of the motor 1 is reduced for warning, the screw by the electric driver 100 is used. The duty D can be set in a range where the tightening operation can be performed so that the operation is not hindered.
[0048]
As mentioned above, although preferred embodiment of the switch for electric tools by this invention and the electric tool using the switch was described referring an accompanying drawing, this invention is not limited to embodiment mentioned above. Those skilled in the art can make various modifications and improvements within the scope of the technical idea described in the claims.
[0049]
For example, although the electric driver 100 has been described as an example of the electric tool in the above embodiment, the present invention is also applicable to other electric tools such as an electric drill, an electric saw, and an impact driver as long as the rotary tool is driven by a motor. Is applicable.
[0050]
Further, the trigger 3 is used as a member constituting the rotation speed instruction means, and the pulling amount of the trigger 3 is used as a value for giving the instruction. However, the trigger 3 does not necessarily move when pressed, for example You may make it give the instruction | indication of rotation speed by other methods, such as detecting a pressure. Further, instead of the trigger 3, a dial or the like that can change the resistance value by rotating it may be used.
[0051]
Furthermore, a warning LED 11 is provided as a second warning means other than a warning based on the number of revolutions of the motor when the remaining capacity of the rechargeable battery 2 falls below a predetermined capacity, and a warning is issued by blinking. A buzzer or the like may be provided as a means to issue a warning by voice.
[0052]
【The invention's effect】
As described above, according to the present invention, it is possible to warn of a decrease in the remaining battery capacity by an intuitive method of changing the number of rotations of the motor, and therefore it is possible to provide a battery remaining capacity warning function that is easy for the operator to understand. It becomes possible. Moreover, since it is possible to stop the tool when it is determined that there is no remaining amount, overdischarge of the battery can be prevented in advance.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a mounting state of an electric driver 100 according to an embodiment of the present invention.
FIG. 2 is a block circuit diagram showing a switch 31 according to an embodiment of the present invention.
FIG. 3 is a time chart showing a driving waveform of the switching element 13;
FIG. 4 is a flowchart showing the operation of the microcomputer 8;
FIG. 5 is a time chart showing a voltage waveform during battery voltage measurement.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Motor, 2 ... Rechargeable battery, 3 ... Trigger, 4 ... Main contact, 5 ... Sliding contact, 6 ... PWM control part, 7 ... Battery remaining charge detection part, 8 ... Microcomputer, 9 ... Power supply circuit, 10 ... Battery voltage detection unit, 11 ... warning LED, 12 ... AND circuit, 13 ... switching element, 14 ... diode, 15 ... forward / reverse switching contact, 16 ... comparison circuit, 17 ... oscillation circuit

Claims (7)

A rotational speed instruction means for instructing the rotational speed of a motor that is a drive source of the electric tool;
Detecting means for detecting a voltage of a battery which is a power source of the electric tool;
Comparison means for comparing the voltage of the battery detected by the detection means with a predetermined voltage;
A remaining capacity determining means for determining whether or not a remaining capacity of the battery is less than a predetermined remaining capacity in accordance with an output of the comparing means;
A rotational speed control means for controlling the rotational speed of the motor in accordance with an output from the rotational speed instruction means and an output from the remaining capacity determination means;
Have
Built in the power tool body,
When the remaining capacity determination means determines that the remaining capacity of the battery is less than the first capacity, the rotation speed control means can perform a predetermined operation with the electric tool, with the maximum rotation speed of the motor, And the switch for electric tools characterized by outputting the said rotation speed control signal made into the 1st rotation speed less than the maximum rotation speed which the said rotation speed instruction | indication means instruct | indicates. When the remaining capacity determining means determines that the remaining capacity of the battery is greater than or equal to the first capacity, the rotational speed control means sets the rotational speed of the motor to the rotational speed indicated by the rotational speed instruction means. The power tool switch according to claim 1, wherein the rotation speed control signal is output. The rotation speed control means stops the rotation of the motor when the remaining capacity determination means determines that the remaining capacity of the battery is less than a second capacity smaller than the first capacity. Item 3. The power tool switch according to any one of Items 1 and 2. A trigger that moves the sliding contact while controlling the start and stop of the power tool,
A variable resistor to which the sliding contact is movably connected;
Detection means for outputting a signal for temporarily stopping a motor that is a driving source of the electric tool and detecting a voltage of a battery that is a power source of the electric tool every first predetermined time during a period when the motor is stopped. When,
A remaining capacity determining means for determining that the remaining capacity of the battery is less than a predetermined capacity when the voltage of the battery detected by the detecting means is continuously less than a predetermined voltage a predetermined number of times;
A rotational speed control signal output means for outputting a rotational speed control signal for controlling the rotational speed of the motor according to the sliding contact voltage at the sliding contact of the variable resistor and the output of the remaining capacity determining means;
Based on the rotational speed control signal, the battery and the motor are intermittently connected, and switching means for changing the rotational speed of the motor;
Have
Built in the power tool body,
When the remaining capacity determining means determines that the remaining capacity of the battery is less than the first capacity, the remaining capacity determining means connects the motor and the power source for a predetermined time of the first predetermined time. A signal that cuts the motor, and the maximum rotational speed of the motor is defined as a first rotational speed that is capable of a predetermined operation by the electric tool and is less than the maximum rotational speed indicated by the sliding contact voltage. The switch for electric tools characterized by lowering the rotation speed of. When the remaining capacity determining means determines that the remaining capacity of the battery is greater than or equal to the first capacity, the rotational speed control means sets the rotational speed of the motor to the rotational speed indicated by the sliding contact voltage. The power tool switch according to claim 4, wherein the rotation speed control signal is output. If the remaining capacity determining means determines that the remaining capacity of the battery is less than the first capacity, the remaining capacity determining means determines whether the remaining capacity is less than a second capacity that is less than the first capacity. The switching means disconnects the connection between the battery and the motor when it is determined that the remaining capacity is less than the second capacity. A switch for an electric tool according to claim 1. An electric tool driven by a motor and having the electric tool switch according to any one of claims 1 to 6.

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