TW201843018A - Motor control apparatus and power tool - Google Patents

Abstract

A motor control apparatus 32 has: an on/off switch 22; a main control unit 36; a motor control circuit 38; an operating voltage generation circuit 40; a SW/AC monitoring unit 46; and an operating voltage monitoring unit 48. The SW/AC monitoring unit 46 monitors the state of the on/off switch SW or the state of a power supply line 35 between the on/off switch SW and a motor 30. The operating voltage monitoring unit 48 monitors the voltage level of an operating voltage Vcc outputted from the operating voltage generation circuit 40. The main control unit 36 controls activation or stopping of the motor 30 by double-checking a SW/AC monitor signal MS from the SW/AC monitoring unit 46 and an operating voltage monitor signal MV from the operating voltage monitoring unit 48.

Description

Motor control device and power tool

The present invention relates to a motor control device and a power tool that use electric power from an external power source for motor operation and control.

Today, motors (electric motors) are used in various applications in the fields of home appliances, industry, and the like. Among them, there are many portable electrical machines around us that insert a plug that is mounted to the main body through a power line into a socket, and receive power supply from an external power source such as a commercial AC power source to operate a motor built in the main body. Generally, in such electrical machines, the user can manually control the operation / stop of the machine by operating a switch provided in the main body.

However, there are cases where the user inserts the plug into the socket with the switch accidentally turned on. In this case, when the electrical machine is accidentally started, various troubles may occur. When the external power is suddenly cut off during the operation of the machine, the motor is stopped, and then the power is turned off and then turned on again, and the motor is restarted accidentally, it will also cause all kinds of troubles.

In the past, in the field of power tools, in order to improve safety and workability, various motor control devices have been developed that have a function to prevent the motor from being accidentally started or restarted when the socket plug is plugged in and unplugged and when the power is turned off and on (Patent Literature 1, 2, 3). [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 60-174079 [Patent Document 2] Japanese Patent Publication No. 8-308098 [Patent Document 3] Japanese Patent Publication No. 8-336779

[Problems to be solved by the invention]

In the portable electrical equipment of the external power supply method as described above, when the socket plug is inserted or removed or the power is temporarily cut off, when the motor stops for a period of time (usually more than a few seconds), the plug is plugged in or the power is restored. At this time, the motor control device is reset and reacted once, which can prevent the motor from being accidentally started or restarted in advance. However, if the power is switched off or reconnected or the plug is plugged in within 1 to 2 seconds after the motor is stopped, the motor control device does not reset under the unstable or uncertain operating voltage and responds to the plug being plugged in or the power off recovery, Therefore, contrary to the user's intention, the motor may be accidentally started or restarted.

The present invention is to solve the above-mentioned problems of the prior art, and to provide a motor control device and a power tool provided with the motor control device to accurately and surely prevent the starting or restarting of a motor not intended by the user. [Means for solving problems]

The motor control device according to the first aspect of the present invention is used to control the operation of a rotating motor that receives electric power from an external power source, and includes: a switch that is electrically connected in series with the motor relative to the external power source; and generates an operating voltage A circuit that inputs electric power from the external power source and outputs a DC operating voltage; and a first monitoring unit that monitors a state of the switch or a state of a feeder line between the switch and the motor, and generates a first monitoring signal, The first monitoring signal indicates whether power is supplied to the feeder from the external power source, and is characterized by having a second monitoring section that monitors the operating voltage and generates a second monitoring signal, the second monitoring signal indicating the operation The voltage level of the voltage is higher or lower than a preset monitoring value; and a control unit that operates at the operating voltage and controls the information based on the information of the first monitoring signal and the information of the second monitoring signal Start and stop of the motor.

In the motor control device configured as described above, the state of the switch or the state of the feeder line between the switch and the motor is monitored by the first monitoring unit, and the voltage level of the operating voltage is monitored by the second monitoring unit. The first monitoring signal from the first monitoring unit and the second monitoring signal from the second monitoring unit are used to control the start and stop of the motor. Even if the power input from the external power supply stops unexpectedly and then restarts, it can accurately and reliably prevent non-source The user intends to start or restart the motor.

A motor control device according to a second aspect of the present invention is used to control the operation of a motor that rotates when receiving power from an external power source, and includes a switch that is electrically connected in series with the motor with respect to the external power source; an operating voltage generation A circuit that inputs electric power from the external power source and outputs a DC operating voltage; and a first monitoring unit that monitors a state of the switch or a state of a feeder line between the switch and the motor; and is characterized by: A monitoring unit that monitors a voltage level of the operating voltage above or below a preset monitoring value; and a control unit that operates at the operating voltage and is based on the monitoring by the first monitoring unit and the second monitoring unit Information to control the start and stop of the motor; in a state where the second monitoring unit gives monitoring information that the voltage level of the operating voltage is higher than the monitoring value, the first monitoring unit gives the switch to switch from the off state When the monitoring information is turned on, the control unit starts the motor in response to the monitoring information from the first monitoring unit; the second monitoring unit gives the voltage level of the operating voltage In the state of the monitoring information having a high monitoring value, when the first monitoring unit gives monitoring information that the power input from the external power source to the feeder is cut off, the control unit responds to the monitoring information from the first monitoring unit While stopping the motor; in a state where the second monitoring unit gives monitoring information whose voltage level of the operating voltage is lower than the monitoring value, the first monitoring unit gives power input from the external power source to the feeder When monitoring information is started or restarted, the control section does not start the motor.

In the motor control device configured as described above, the state of the switch or the state of the feeder line between the switch and the motor is monitored by the first monitoring unit, and the voltage level of the operating voltage is monitored by the second monitoring unit. The monitoring information from the first monitoring unit and the monitoring information from the second monitoring unit are used to control the start and stop of the motor. Even if the power input from the external power supply stops unexpectedly and then restarts, it is possible to accurately and reliably prevent unintended actions by the user. The motor starts or restarts.

The electric tool according to the first aspect of the present invention includes: a main body; a movable tool that is mounted to the main body in a manner to perform a certain movement; a motor provided in the main body and used for receiving power supply from an external power source and Drive the tool; a motor control device provided in the main body for controlling the operation of the motor by receiving power supply from the external power source, including: a switch which is provided in electrical series with the motor relative to the external power source An operating voltage generating circuit that inputs electric power from the external power source and outputs a DC operating voltage; and a first monitoring unit that monitors the state of the switch or the state of the feeder line between the switch and the motor, and generates a first 1 monitoring signal, the first monitoring signal indicates whether power is supplied to the feeder from the external power source, and is characterized by having a second monitoring unit that monitors the operating voltage and generates a second monitoring signal, the second monitoring signal The signal indicates that the voltage level of the operating voltage is higher or lower than a preset monitoring value; and the control section, which operates at the operating voltage, and Control the start and stop of the motor based on the information of the first monitoring system signal and the information of the second monitoring system signal.

In the electric tool having the above configuration, the motor control device according to the first aspect of the present invention can accurately and surely prevent a motor that is not intended or started by a user from intention even if the power input from an external power source stops unexpectedly and then restarts. Restart to improve safety and workability.

An electric tool according to a second aspect of the present invention includes: a main body; a movable tool that is mounted to the main body in a manner to perform a certain movement; and a motor provided in the main body and used to receive power from an external power source. Drive the tool; a motor control device provided in the main body for controlling the operation of the motor by receiving power supply from the external power source, including: a switch which is provided in electrical series with the motor relative to the external power source An operating voltage generating circuit that inputs electric power from the external power source and outputs a DC operating voltage; and a first monitoring unit that monitors a state of the switch or a state of a feeder line between the switch and the motor; and is characterized by: It has a second monitoring unit that monitors the voltage level of the operating voltage above or below a preset monitoring value; and a control unit that operates at the operating voltage and is based on the first monitoring unit and the second monitoring unit. The monitoring information of the monitoring unit controls the start and stop of the motor; the second monitoring unit gives monitoring information of a voltage level of the operating voltage higher than the monitoring value. In a state, when the first monitoring unit gives monitoring information that the switch is switched from an off state to an on state, the control unit starts the motor in response to the monitoring information from the first monitoring unit; the second monitoring unit gives In a state where the voltage level of the operating voltage is higher than the monitoring information, when the first monitoring unit gives monitoring information that the power input from the external power source to the feeder is cut off, the control unit responds from The monitoring information of the first monitoring unit stops the motor; while the second monitoring unit gives monitoring information that the voltage level of the operating voltage is lower than the monitoring value, the first monitoring unit gives the information from the outside When the power input from the power supply to the feeder is monitored or restarted, the control section does not start the motor.

In the electric tool having the above configuration, the motor control device according to the second aspect of the present invention can accurately and surely prevent a motor that is not intended or started by a user from intention even if the power input from an external power source stops unexpectedly and then restarts. Restart to improve safety and workability. [Inventive effect]

According to the motor control device of the present invention, with the structure and function as described above, it is possible to accurately and surely prevent the motor from starting or re-starting without the user's intention by stopping and subsequently restarting the input of power from the external power source. start up.

According to the electric power tool of the present invention, the structure and function as described above can accurately and surely prevent starting or restarting of a motor not intended by the user, and improve safety and workability.

An embodiment of the present invention will be described below with reference to the drawings.

[Appearance and Configuration of Power Tool] FIG. 1 shows the appearance of an electric belt grinder as an electric power tool in an embodiment of the present invention. This electric belt mill 1 has a cylindrical main body 10, a socket plug 14 attached to the base end portion of the main body 10 through a power line 12, a grinding belt 16 rotatably attached to the front end of the main body 10, A movable grinding band 18 extending from the base end portion to the front end of the grinding band 16, a rod-shaped handle 20 fixed to the grinding band 16, a switch 22 provided at an appropriate position on the outer peripheral surface of the main body 10, and a display portion 24.

The main body 10 is also used as another gripping portion that is paired with the handle 20, and the circuit board of the motor 30 and the motor control device 32 (FIGS. 2 and 3) described below is housed inside. In addition, a transmission mechanism (not shown) that transmits a rotational driving force of the motor 30 to the gear of the grinding belt 16 is also accommodated in the front end portion of the main body 10. The grinding belt 16 includes a driving pulley (not shown) at a base end portion, and a driven pulley (not shown) is installed at a front end portion thereof. A circular grinding belt 18 extends between the two pulleys. . During processing, the rotational driving force of the motor 30 is transmitted to the grinding belt 18 through the above-mentioned transmission mechanism and driving pulley, etc. The grinding belt 18 linearly moves between the two pulleys while abrading the workpiece (not shown), thereby Grind or grind the workpiece.

The switch 22 is composed of, for example, a sliding manual switch. When the user releases his or her finger in its open position or closed position, it is locked in its released position. The display section 24 has, for example, a plurality of LEDs or lamps, which are turned on or flashed with a preset luminous color to display a warning when the operating condition or abnormal situation of the belt mill is displayed.

[Configuration of Motor Control Device] FIG. 2 is a schematic diagram showing a system configuration of a motor 30 and a motor control device 32 mounted on the electric belt mill.

The motor 30, for example, composed of single-phase AC motor, 14, the wire 12 (FIG. 1) and the switch 22, for example from the commercial AC (alternating current) commercial power source 34 receives a fixed effective value V _E (e.g. 100 volts) through the outlet plug The AC power E of the frequency is supplied to rotate under the control of the motor control device 32.

The motor control device 32 includes, as a basic configuration, a switch 22, a main control unit 36, a motor control circuit 38, an operating voltage generating circuit 40, a reference clock / timing unit 42, a motor rotation measuring unit 44, a SW / AC monitoring unit 46, Operating voltage monitoring section 48.

The operating voltage generating circuit 40 is electrically connected in parallel with the motor 30 with respect to the AC power source 34, and is configured to input AC power E from the AC power source 34 and output a DC operating voltage at a preset rated value (for example, 5 volts). V _CC . The operation voltage V _CC output from the operation voltage generating circuit 40 is supplied to all units in the motor control device 32 that require an operation voltage through the operation voltage supply line.

The motor control circuit 38 is provided in series with the switch 22 and the motor 30 with respect to the AC power source 34. When AC power E is input from the AC power source 34 through the plug 14 and the electric wire 12 and the switch 22 is turned on, the motor control circuit 38 controls the current flowing to the motor 30 under the control of the main control unit 36.

The reference clock / timing unit 42 includes an oscillator 50 and a zero-cross detection unit 52. The oscillator 46 is composed of, for example, a crystal oscillator, and generates a clock CK required for calculation and other processing in the main control unit 36. The zero-cross detection unit 52 detects the timing at which the commercial frequency AC supplied by the AC power source 34 crosses the zero level, and generates a timing pulse of a reference required by the main control unit 36 to perform ignition control or phase control of the motor 30 Signal CZ.

The motor rotation number measurement unit 44 includes a rotation detection sensor 54 that detects the position of a rotating body (rotor) of the motor 30 and a rotation number calculation that calculates the rotation speed of the motor 30 based on the output signal of the rotation detection sensor 54.部 56.

The SW / AC monitoring unit 46 is the first monitoring unit in this embodiment, and is configured to monitor the state of the switch SW or the state of the feeder 35 between the switch SW and the motor 30, and generate a SW / AC monitoring signal (the first Monitoring signal) MS, which indicates whether the electric power from the AC power source 34 is input to the feeder 35.

The operating voltage monitoring unit 48 is the second monitoring unit in this embodiment, and is configured to input and monitor the same voltage as the operating voltage V _CC supplied from the operating voltage generating circuit 40 to the main control unit 36 and generate an operating voltage monitoring signal. (Second monitoring signal) MV, which indicates that the voltage level of the operating voltage V _CC is higher or lower than a preset monitoring value.

As described above, the main control unit 36 inputs the operating voltage V _CC from the operating voltage generating circuit 40, inputs the basic clock CK and the timing pulse signal CZ from the reference clock / timing unit 42 (50, 52), and counts the number of rotations from the motor. The measurement unit 44 (54, 56) inputs a rotation number measurement value indicating the rotation speed of the motor 30, the SW / AC monitoring signal MS from the SW / AC monitoring unit 46, and the operating voltage monitoring signal MV from the operating voltage monitoring unit 48. The main control unit 36 has signal processing and arithmetic processing functions, and controls the start, rotation operation, and stop of the motor 30 through the motor control circuit 38.

FIG. 3 shows a specific circuit configuration of the motor control device 32 in this embodiment. The main control unit 36 and the rotation number calculation unit 56 are preferably constituted by a microcomputer. The rotation detection sensor 54 is preferably a Hall IC. The operating voltage generating circuit 40 is composed of an AC-DC conversion circuit. As a preferred form, it has an input capacitor 60, a full-wave rectification circuit 62 composed of four diodes bridged, and a Zener for smoothing or ripple suppression. Output circuits 74 of the diodes 64, 66, resistors 68, 70, and capacitor 72.

The zero-cross detection unit 52 is preferably formed by an optical coupler 76. When AC power E is input from the AC power source 34, only when the commercial frequency AC crosses the zero level, the photoelectric crystal 76a of the photocoupler 76 is turned off instantaneously, and the timing pulse signal CZ is obtained at the collector terminal of the photoelectric crystal 76a. , Which indicates the start timing of each half cycle of the commercial AC frequency. This timing pulse signal CZ is supplied to a predetermined input port of the main control section 36.

The motor control circuit 38 preferably includes a bidirectional thyristor 78 and a photo triac 80 as a preferred embodiment. Here, the bidirectional brake fluid 78 constitutes a switching element, and is electrically connected in series with the switch 22 and the motor 30 with respect to the AC power source 34. The light bidirectional tripolar gate fluid 80 combines the surrounding capacitor 82 and the resistors 83 and 84 to form an ignition circuit or a phase control circuit. The light emitting diode 80 a is connected to a predetermined output port of the main control unit 36. The main control unit 36 controls the turn-on (light-on) and turn-off (light-off) of the light-emitting diode 80a, and uses the light bi-directional tripolar gate fluid 80 to synchronize with the preset ignition angle or phase of the timing pulse signal CZ The angle controls the bidirectional brake fluid 78, and the current to the motor 30 can be arbitrarily controlled.

In this way, the motor control circuit 38 electrically isolates and separates the motor drive system operating under the high voltage (AC 100 volts) of the AC power source 34 by using the optical bidirectional tripolar gate fluid 80 in the ignition circuit or the phase control circuit. Circuits and circuits of a control system operated with an operating voltage (DC 5 volts).

The SW / AC monitoring unit 46 preferably has a branch or branch circuit 86 electrically connected in parallel to the feeder 35 or the motor 30, and a photocoupler 88 and a current limiting resistor 90 are connected in series to the branch circuit 86. Here, the phototransistor 88a of the photocoupler 88 has a collector terminal connected to a voltage supply line or terminal of the operating voltage V _CC through a pull-up resistor 92 and is connected to a predetermined input port of the main control section 36, and its emitter terminal Connect to ground potential terminal.

In the SW / AC monitoring unit 46 configured as described above, when AC power E from the AC power source 34 is input to the feeder 35 through the switch 22, regardless of the state (running / stopping) of the motor 30, current flows to the branch circuit 86 and is optically coupled The photonic crystal 88a of the device 88 is turned on, and the SW / AC monitoring signal MS obtained at its collector terminal becomes the ground potential collector, that is, the L level. However, when AC power E is input to the operating voltage generating circuit 40 but not to the feeder 35 (when the switch 22 is closed), the photo-transistor 88a of the photocoupler 88 is turned off, and the SW / AC monitoring obtained at its collector terminal is MS signal becomes a potential of the operating voltage V _CC i.e. H level. The main control unit 36 receives and monitors the SW / AC monitoring signal MS at any time. When the voltage level is higher than a predetermined H level threshold V _H (for example, 2.0 volts), it determines that the monitoring signal MS is at the H level (MS = “H ”), And when it is lower than the predetermined L-level threshold V _L (for example, 0.8 volts), it is judged that the monitoring signal MS is the L-level (MS =“ L ”). In addition, when the voltage level of the monitoring signal MS is between the L-level threshold V _L and the H-level threshold V _H , it is uncertain.

In this way, the SW / AC monitoring unit 46 electrically isolates the high voltage (AC 100 volts) of the AC power source 34 by using a photocoupler 88 in the current detection unit for detecting whether a current flows to the branch circuit 86. The current detection circuit and the monitoring signal output circuit operated with the operating voltage (DC 5 volts).

The operating voltage monitoring unit 48 is preferably a integrated circuit. Although not shown, it has a comparator and an output circuit. The comparator compares the voltage level of the operating voltage V _CC input from the operating voltage generating circuit 40. The standard and preset monitoring value V _K output a comparison result indicating the relationship between the two. The output circuit sends the comparison result from this comparator to the main control unit 36 as a two-value operation voltage monitoring signal MV. In more detail, when the voltage level of the operating voltage V _CC is higher than the monitoring value V _K , the monitoring signal MV is output at the H level, and when the voltage level of the operating voltage V _CC is lower than the monitoring value V _K , the L level is output. Quasi-output monitoring signal MV. When the voltage level of the operating voltage V _{CC is} the same as the monitoring value V _K , it can be determined that MV = “H” or MV = “L”. The monitoring value V _K is set to a value higher than the limit value of the operating voltage V _CC at which the main control unit 36 can normally operate. For example, if the rated value V _S of the operating voltage V _CC is 5 volts, the monitoring value V _K is set to 4.5 volts.

The display unit 24 includes, for example, three LEDs 94R, 94Y, and 94B whose emission colors are red, yellow, and blue (or green). These LEDs 94R, 94Y, and 94B are connected in parallel to the output port of the main control unit 36, and their respective on and off lights are individually controlled.

[Function of Motor Control Device] Next, the function of the motor control device 32 in this embodiment will be described with reference to FIGS. 4 to 11.

The basic control program of the main control unit 36 for starting and stopping the motor 30 in the motor control device 32 is shown in a flowchart in FIG. 4. In addition, FIG. 5 and FIG. 6 show timing changes of the states of the respective units when the AC power is normally supplied from the AC power source 34 during the operation of the electric belt mill in a timing chart.

In this motor control device 32, when the plug 14 is inserted into the socket of the AC power source 34, regardless of the state of the switch 22, AC power E from the AC power source 34 is input to the operating voltage generating circuit 40, and an operation is output from the operating voltage generating circuit 40. Voltage V _CC . At this time, the operating voltage V _CC instantly rises from the previous 0 volt to the rated value V _S (DC 5 volt). When this operating voltage V _CC rises to the rated value V _S , the sections that operate under the operating voltage V _CC , that is, the main control section 36, the motor rotation number measuring section 44 (54, 56), the operating voltage monitoring section 48 and the like become activation. On the other hand, when the AC power E starts to be input, a timing pulse signal CZ is supplied from the zero-cross detection unit 48 to the main control unit 36.

The main control unit 36 first initializes the initial settings required for the register and output port used this time (step S ₁₀₁ ). In this initialization, a set value (for example, 10 ms) of the unit delay time T _P and a set value (for example, 5 times) of the delay times N _S are set. Then, the number of delays is initialized (N = 0) (step S _R ). The unit delay time T _P is set to a value shorter than a monitoring value arrival time T _K described later. Next, the main control unit 36 receives the SW / AC monitoring signal MS from the SW / AC monitoring unit 46 through a preset input port and reads its logical value (step S ₁₀₂ ).

As shown in FIG. 5, usually, when the user inserts the plug 14 into the AC power source 34 socket (at time t ₀ ), the switch 22 is turned off. In this case, since no current flows to the branch circuit 86 in the SW / AC monitoring unit 46, the photo-crystal 88 a of the photo-coupler 88 is turned off. As a result, at the same time when the AC power E starts to be input, that is, at the time point t ₀ , as the operating voltage V _CC rises, the SW / AC monitoring signal MS changes from the previous L level to the H level. Therefore, the main control unit 36 judges that MS = “H” and reads the value of the operating voltage monitoring signal MV from the operating voltage monitoring unit 48 after the delay time T _P (step S _F ) has elapsed (step S ₁₀₃ ). At this time, the operating voltage V _CC rises to the rated value (5 volts), and MV = “H”.

The main control unit 36, when it is confirmed MS = state "H" and MV = "H", and five times the loop [C] (Step _{S P → S 104c → S 105} → S 102 → S F → S 103 → S _P → ‧‧), and when the number of delays N reaches the set number of times N _S (5 times), which means that when 50ms (10ms × 5) elapses from the time point t ₀ , leave the circuit C and make preparations for starting the motor 30 ( Step S _P → S ₁₀₆ ), and then continue the loop [D] (Step S ₁₀₇ → S ₁₀₈ → S ₁₀₇ → ‧‧), and wait for the SW / AC monitoring signal MS to change from H level to L level.

As shown in FIG. 5, the SW / AC monitoring signal MS changes from the H level to the L level, that is, when the user turns on the switch 22 (time point t ₁ ). At this time, in the SW / AC monitoring unit 46, the current starts to flow to the branch circuit 86, the phototransistor 88a of the photocoupler 88 changes from the previous off state to the on state, and the SW / AC monitoring signal MS changes from the H level to the L level. .

The main control section 36 starts the motor 30 through the motor control circuit 38 when the SW / AC monitoring signal MS changes from the H level to the L level (time point t ₁ ) (steps S ₁₀₇ → S ₁₀₉ ). Thereafter, the main control unit 36 monitors the SW / AC monitoring signal MS, and while confirming that the monitoring signal MS is at the L level, continuously loops the loop [E] (steps S ₁₀₉ → S ₁₁₀ → S ₁₁₁ → S ₁₀₉ → ‧ ‧), continue the rotation operation of the motor 30.

While the rotation operation of the motor 30 is continued in this way, the main control unit 36 measures the number of rotations or the load of the motor 30 through the motor rotation number measurement unit 44 (54, 56), and controls the flow to the motor 30 through the motor control circuit horse 38 The current is immediately notified to the user of the operation status (especially the load status) through the display unit 24. For example, turn on the blue (green) LED 94B at normal or no load (maximum rotations), turn on the yellow LED 94Y at light loads (80% of rotations), and turn on the light at high loads (60% of rotations). Red LED 94R turns on. When overload occurs, the following display control can be performed, for example, flashing the red LED 94R at a high interval of 0.2 seconds to stop the motor 30. Immediately after stopping, the red LED 94R is switched from high-speed blinking to low-speed blinking at a interval of 1 second .

Then, the grinding process of the electric belt mill is finished. When the user turns off the switch 22 (time point t ₂ ), the SW / AC monitoring signal MS changes from the previous L level to the H level. At this time, in the SW / AC monitoring unit 46, no current flows to the branch circuit 86, and the phototransistor 88a of the photocoupler 88 is turned off.

When the SW / AC monitoring signal MS changes from the L level to the H level, the main control unit 36 completely closes the switching element 78 of the motor control circuit 38 at this point in time to stop the motor 30 (steps S ₁₁₀ → S ₁₁₂ ) . Then, the number of delays is initialized (N = 0) (step S ₁₁₃ → S _R ), and the loop [C] is repeated in the same manner as when the AC power E starts to be input, and the number of delays is set to N _S (5 times) and MS = is repeated. "H" and MV = confirm "H", the process proceeds motor starting preparation (step S _P → S _106), then continuing cycle [D], wait for the switch 22 is switched ON.

The example shown in FIG. 5 shows a case where the user pulls the plug 14 out of the socket at a time point t ₃ after a period of time (for example, several seconds or more) has elapsed. In this case, when the plug 14 is unplugged from the socket, the AC power E from the AC power source 34 is no longer input to the operating voltage generating circuit 40, and the output voltage of the operating voltage generating circuit 40 is the operating voltage V _CC from The rating drops to zero volts. In this case, the charge stored in the output capacitor 72 of the operating voltage generating circuit 40 is discharged through the resistor 70, so the operating voltage V _CC gradually decreases with a fixed time constant. Then, when the operation voltage V _{CC is} lower than a preset operation limit value (for example, about 1.8 volts), the main control section 36 becomes an inactive state.

FIG. 6 shows the user inserting the plug 14 into the socket of the AC power source 34 when the switch 22 is on. In this case, no matter what the state of switch 22, simultaneously with the start input AC power from the AC power source 34, E (the time point _{t 0),} operation of the voltage generating circuit 40 rises to the operating voltage V _CC rating V _S, the operation The voltage monitoring signal MV rises from the previous L level to the H level.

In this case, when the main control unit 36 reads the SW / AC monitoring signal MS immediately after the initial setting (step _S101 ) (step _S102 ), the monitoring signal MS remains at the L level. In other words, in the SW / AC monitoring unit 46, since the switch 22 is on, the AC power E starts to input and the current starts to flow to the branch circuit 86, and the phototransistor 88a of the photocoupler 88 becomes on. Therefore, the SW / AC monitoring The signal MS remains at the L level. The main control unit 36 continues the loop [A] (steps S ₁₀₂ → S _104a → S _R → S ₁₀₂ → S _104a ‧ ‧ ‧ ‧) and waits for the monitoring signal MS to change from L level to H level.

Then, when the user switches the switch 22 to off, no current flows to the branch circuit 86 in the SW / AC monitoring section 46, the photo-crystal 88a of the photocoupler 88 is turned off, and the SW / AC monitoring signal MS changes from the L level H level. Therefore, the main control unit 36 confirms that MS = "H" and MV = "H". When the loop [C] is performed 5 times and the delay number N reaches the set number N _S (5 times), it means from the time point t ₀ passes 50ms (10ms × 5), in order to start preparing to enter (step S _P → S ₁₀₆₎ 30 a motor cycle duration [D] until the switch 22 is switched to open.

Then, when the user turns on the switch 22 (time point t ₁ ), the motor 30 is started because the SW / AC monitoring signal MS changes from the H level to the L level (step S ₁₀₇ → S ₁₀₉ ) , The loop circuit [E] continues the rotation operation of the motor 30. Then, when the user turns off the switch 22 or the plug 14 is pulled out of the socket, the motor 30 is stopped because the monitoring signal MS changes from the H level to the level (steps S ₁₁₀ → S ₁₁₂ ). The subsequent control procedures and operations are the same as in the case of FIG. 5.

In this way, in this embodiment, even if the user inserts the plug 14 into the AC power source 34's socket when the switch 22 is on, the motor 30 will not start, and the switch 22 is once turned off and then switched on again. Before starting the motor 30.

Occasionally, as shown in FIG. 7, while the rotation operation of the motor 30 is continuing, at, for example, a time point t _a , a power outage occurs suddenly, or the plug 14 is accidentally pulled out of the socket. In this case, the input of the AC power E is temporarily suspended, and therefore, even if the switch 22 is turned on, the power supply to the feeder 35 and the motor 30 is suspended, and the power to the operating voltage generating circuit 40 is also suspended. However, in the operating voltage generating circuit 40, since the electric power stored in the capacitor 72 of the output circuit 74 is discharged with a fixed time constant, its output voltage, that is, the operating voltage V _CC decreases exponentially from the rated value V _S , as if the plug were normally inserted. 14 Same when unplugged from socket.

Therefore, at the same time when the AC power E input is stopped, the current flowing to the branch circuit 86 in the SW / AC monitoring unit 46 is cut off so far, the phototransistor 88a of the photocoupler 88 is turned off, and the SW / AC monitoring signal MS is changed from the previous The L level changes to the H level. The main control unit 36 stops the motor control circuit horse 30 through the motor control circuit 38 at the time point when the monitoring signal MS changes (MS = "L" → "H") (steps S ₁₁₀ → S ₁₁₂ ).

In the example of FIG. 7, it is shown that a certain period of time (the monitoring value arrival time) until the voltage level of the operating voltage V _CC decreases to the monitoring value V _K after the time point t _a when the AC power E input stops is elapsed. ) after the time point T _K (e.g. 30ms) (for example, stopping power from an AC input point E point 40ms time t _a elapsed time t _c), the user again plug 14 into the socket.

In this case, when the input of the AC power E from the AC power source 34 is restarted at the time point t _c , the operating voltage generating circuit 40 instantly returns the operating voltage V _CC to the rated value V _S , and the operating voltage monitoring section 48 is also rough. The operation voltage monitoring signal operation MV is changed from L level to H level instantly. On the other hand, when the AC power E input is restarted, the SW / AC monitoring unit 46 turns on the photo-transistor 88a of the photocoupler 88, so that the voltage level of the SW / AC monitoring signal MS instantly falls from the previous H level to Zero volts (L level). In addition, the voltage level of the SW / AC monitoring signal MS rises to the vicinity of the rated value V _S once when the input of AC power E stops, and then decreases exponentially following the operating voltage V _CC . The main control unit 36 determines that MS = "H" until the voltage level of the SW / AC monitoring signal MS decreases to the H level threshold _VH .

The processing procedure of the main control unit 36 in this case is as follows. That is, after the motor 30 is stopped, the number of delays is initialized (N = 0) (step S ₁₁₃ → S _R ), and MS = “H” and MV = “H” are confirmed, and the loop circuit [C] is continued. During this period, when the above-mentioned monitoring value arrival time T _K (30ms) elapses, the voltage monitoring signal MV changes from the H level to the L level during this operation, and moves from the loop [C] to the loop [B] (step S ₁₀₃ → S _104b → S _R → S ₁₀₂ → S _F → S ₁₀₃ → ‧‧). Then, at a subsequent time point t _c , when the input of the AC power E is restarted and the operating voltage monitoring signal MV returns from the L level to the H level, it leaves from the loop [B] to check the number of delays (step S ₁₀₃ → S _P). At this time, since the delay has not yet reached the set number of times N _S (5 times), the loop enters the [C] to inspect SW / AC monitoring signal MS (step _{S P → S 104c → S 105} → S 102). Then, since MS = "L", the circuit [A] is entered (step S ₁₀₂ → S _104a → S _R → ‧ ‧), and the circuit [A] is continued continuously thereafter.

In this embodiment, even when the AC power E input restart time point t _c exceeds the unit delay time (10 ms) multiplied by the delay setting number N _S (50 ms), the main control unit 36 remains in the loop During [A] to [C], the motor will not move to the motor start preparation (step _S106 ). In other words, when the loop [C] is performed 4 times, that is, at the time point t _b when 40 ms has passed from the AC power E input stop time point t _a , the operating voltage monitoring signal MV changes from the H level to the L level, This moves from circuit [C] to circuit [B] (steps S ₁₀₃ → S _104b → S _R → ‧‧). Thereafter, at a time point when t AC input power E _c and then start, while away from the circuit [B] (Step S ₁₀₃ → S _P), but due to the delay times does not reach the set number N _S (5 times), was into the loop [C] (step _{S P → S 104c → S 105} → S 102). However, since the SW / AC monitoring signal MS is at the L level at this time, it moves from circuit [C] to circuit [A] (step S ₁₀₂ → S _104a → S _R → ‧‧), and then stays in circuit [A] .

In the example of FIG. 8, it shows a case where the time point t _a from which the AC power E input is stopped elapses before the monitoring value reaches the time T _K (30 ms) (for example, from the AC power input stop time point t _a After the time point of 20ms) t _β , the user inserts the plug 14 into the socket again, and the input of the AC power E is turned on again.

The processing procedure of the main control unit 36 in this case is as follows. That is, after the motor 30 is stopped, the number of delays is initialized (N = 0) (step S ₁₁₃ → S _R ), and then the logical values of the SW / AC monitoring signal MS and the operating voltage monitoring signal MV are checked (steps S ₁₀₂ , S ₁₀₃ ). After the AC power input is stopped, MS = "H" and MV = "H", so the loop circuit [C] is continued. Then, when the input of AC power E is restarted at the time point t _β before the monitoring value reaches the time T _K (30ms), check the SW / AC monitoring signal MS in the loop [C] (step S ₁₀₃ → S _104c → S ₁₀₅ → S ₁₀₂ ). Then, since the SW / AC monitoring signal MS also changes from the H level to the L level at the time point t _β , it enters the loop [A], and thereafter remains in the loop [A].

In this way, in this embodiment, the main control unit 36 double-checks the monitoring information (MS) from the SW / AC monitoring unit 46 and the monitoring information (MV) from the operating voltage monitoring unit 48. When monitoring information (MV = “L”) where the operating voltage V _CC is lower than the preset monitoring value V _{K is} output, even if the SW / AC monitoring unit 46 gives start or restart input from the AC power source 34 The monitoring information (MS = "H" → "L") of the AC power to the feeder 35 will not start the motor 30.

Accordingly, during the grinding process using this electric belt mill, when the plug 14 is pulled out from the socket contrary to the user's intention, the motor 30 will not start even if the plug 14 is hurriedly inserted back into the socket. This is the case even if the AC power source 34 suddenly loses power during the grinding process and immediately resumes power. In this case, the user can turn on the motor 30 again by turning off the switch 22 once and then turning it on again.

In addition, when the main control unit 36 prevents the restart of the motor 30 as described above, the main control unit 36 urges the user to operate the switch 22 by a warning from the display unit 24, such as a low-speed blinking green LED 94G.

Incidentally, as a comparative example, when the operating voltage monitoring section 48 is removed from the motor control device in this embodiment, the control program of the main control section 36 is shown in FIG. 9, and the voltage levels or logical values of the sections are shown in 10 changes as shown. In this case, including checking from the operation voltage monitoring unit operation (48) of the monitor (step S ₁₀₃₎ information (operation voltage monitoring signal MV), the delayed correlation process (step _{S R, S F, S P} ), the circuit [ B], [C], etc. The main control unit 36 controls the start and stop of the motor 30 based only on the monitoring information (SW / AC monitoring signal MS) from the SW / AC monitoring unit 46. For this reason, when the input of AC power E suddenly stops during the grinding process and immediately restarts (time point t _c ), the SW / AC monitoring signal MS changes from the H level to the L level, and the main control unit 36 responds to this and restarts The motor 30 is started (steps S ₁₀₆ → S ₁₀₉ ). However, since such a restart is not the intention of the user, it may cause danger to the user or those around him, and it is not a job expectation.

[Other Embodiments or Modifications] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. Those skilled in the art can make various modifications and changes without departing from the technical idea and technical scope of the present invention in the specific embodiments.

For example, in the above embodiment, the control program (FIG. 4) of the main control unit 36 may be modified as shown in FIG. 11. This modified embodiment or the second embodiment is omitted delay initialization process (step S _R), the delay times inspection program (step S _P) and a circuit [C], instead added SW / AC monitoring signal and then check program (step S _G) And circuit [F]. Here, the delay time T _P in the delay program (step S _F ) is set to a value equal to or slightly larger than the monitoring value arrival time T _K (30 ms) (for example, 30 to 35 ms). With the control program of this embodiment, the same operations as those in FIGS. 7 and 8 can be performed.

That is, in the case of FIG. 7, from the AC power E input stop time point t _a timing delay time T _P , the monitoring value arrival time T _K (30ms) passes and the operating voltage monitoring signal MV changes from the H level to L Level. With this, when the operating voltage monitoring signal MV is checked after the delay time T _P elapses, MV = “L” and enters the loop [B] (step S ₁₀₃ → S _104b → S ₁₀₂ → S _F → S ₁₀₃ → S _104b ‧ ‧‧‧). Then, when the AC power input is restarted at a later time point t _c , since the SW / AC monitoring signal MS becomes the L level, it enters the loop [A] (step S ₁₀₂ → S _104a → S ₁₀₂ → ‧ ‧), It remains in circuit [A] afterwards.

In addition, in the case of FIG. 8, from the AC power E input stop time point t _a timing delay time T _P , the AC power E input is restarted at the time point t _β , although the operating voltage monitoring signal MV changes from the L level H level (step S ₁₀₃ ), but since the SW / AC monitoring signal MS is L level, it enters loop [A] via loop [F] (steps S _G → S _104a → S ₁₀₂ ‧ ‧), and thereafter It remains in the loop [A].

Regarding the circuits around the main control unit 36, for example, the operating voltage generating circuit 40 can generate plural kinds of operating voltages. In this case, the operating voltage monitoring unit 48 may monitor any one of the plural types of operating voltages, and generally monitors the voltage level of those supplied to the main control unit 36. In addition, the external power source 34 is not limited to a single-phase commercial AC power source, and may be a single-phase or three-phase AC power source having an arbitrary frequency, or a DC power source. Therefore, the operating voltage generating circuit 40 is not limited to a single-phase AC / DC conversion circuit, it may be a three-phase AC / DC conversion circuit, or it may be composed of a switching power supply circuit, an inverter circuit, and the like. The motor 30 is not limited to a single-phase AC motor, and may be any motor. In the SW / AC monitoring unit 46, although the high-speed current detection unit can be configured using the photocoupler in the above-described embodiment, a relay or the like may be used instead of the photocoupler.

The electric belt grinder in the above embodiment is an example of the electric tool of the present invention. The present invention can be applied to electric chamfering machines, disc grinding machines, disc grinding machines, strippers, cutting machines, punching machines, etc. Any power tool that uses a motor for external power supply. In addition, the motor control device of the present invention is not limited to a power tool, and can be applied to any electric equipment using a motor as an external power supply system of a power source.

1‧‧‧ Electric belt mill

10‧‧‧main body

12‧‧‧ Power Line

14‧‧‧Socket Plug

16‧‧‧Grinding belt

18‧‧‧ grinding belt

20‧‧‧handle

22‧‧‧Switch

24‧‧‧Display

30‧‧‧Motor

32‧‧‧Motor control device

34‧‧‧AC Power

35‧‧‧ Feeder

36‧‧‧Main Control Department

38‧‧‧motor control circuit

40‧‧‧operating voltage generating circuit

42‧‧‧Reference clock / timing section

44‧‧‧ Motor rotation measurement section

46‧‧‧SW / AC Surveillance Department

48‧‧‧Operating Voltage Monitoring Department

50‧‧‧ Oscillator

52‧‧‧Zero crossing detection department

54‧‧‧Rotary detection sensor

56‧‧‧rotation number operation section

60‧‧‧input capacitor

62‧‧‧Full-wave rectifier circuit

64, 66‧‧‧Zina Diodes

68, 70‧‧‧ resistance

72‧‧‧ capacitor

74‧‧‧output circuit

76‧‧‧ Optocoupler

76a‧‧‧photoelectric crystal

78‧‧‧Two-way brake fluid

80‧‧‧light bidirectional tripolar gate fluid

80a‧‧‧light-emitting diode

82‧‧‧Capacitor

83, 84‧‧‧ resistance

86‧‧‧ Branch circuit

88‧‧‧ Optocoupler

88a‧‧‧photoelectric crystal

90‧‧‧ resistance

92‧‧‧ Pull-up resistor

94R, 94Y, 94B‧‧‧LED

[A], [B], [C], [D], [E], [F] ‧‧‧loop

CK‧‧‧ clock

CZ‧‧‧Time Series Pulse Signal

E‧‧‧AC Power

MS‧‧‧SW / AC monitoring signal

MV‧‧‧Operating voltage monitoring signal

S ₁₀₁ , S ₁₀₂ , S ₁₀₃ , S _104a , S _104b , S _104c , S _104d , S ₁₀₅ , S ₁₀₆ , S ₁₀₇ , S ₁₀₈ , S ₁₀₉ , S ₁₁₀ , S ₁₁₀ , S ₁₁₂ , S ₁₁₃ , S _{F , S G, S P, S} R ‧‧‧ step

t ₀ , t ₁ , t ₂ , t ₃ , t _a , t _b , t _c , t _d , t _β ‧‧‧

T _K ‧‧‧ Monitoring value arrival time

Operating voltage V _CC ‧‧‧

V _E ‧‧‧RMS

V _H ‧‧‧H threshold level

Monitoring value V _K ‧‧‧

V _L ‧‧‧L level threshold

V _S ‧‧‧ Rating

FIG. 1 is a perspective view showing an external appearance of an electric belt grinder as an electric power tool according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a system configuration of a motor and a motor control device mounted on the electric belt mill. Fig. 3 is a circuit diagram showing a specific circuit configuration of the motor control device in the embodiment. FIG. 4 is a flowchart showing a basic control routine of a main control unit of the motor control device related to the start and stop of a motor in the embodiment. FIG. 5 is a timing chart showing the state of each part when the plug is inserted into the socket with the switch turned off, and the power from the external power source is normally supplied. FIG. 6 is a timing chart showing changes in the state of each part when the plug is inserted into the socket with the switch on, and the power from the external power source is normally supplied. FIG. 7 is a timing chart showing changes in the state of each part in an example in which the power input from the external power source was stopped once and then restarted during the operation in the above embodiment. FIG. 8 is a timing chart showing changes in the state of each part in another example in which the power input from the external power supply was stopped once and then restarted during the operation in the above embodiment. FIG. 9 is a flowchart showing a basic control routine of the main control unit in a case where the operating voltage monitoring unit is removed from the motor control device of the embodiment (comparative example). FIG. 10 is a timing chart showing changes in the state of each part in the comparative example (FIG. 9). FIG. 11 is a flowchart showing a modification of the control program of the main control unit in the motor control device.

Claims (18)

A motor control device for receiving electric power from an external power source to control the operation of a rotating motor includes: a switch that is electrically connected in series with the motor with respect to the external power source; an operating voltage generating circuit whose input comes from the And a first monitoring unit that monitors a state of the switch or a state of a feeder line between the switch and the motor, and generates a first monitoring signal, the first monitoring signal indicates Whether to supply power to the feeder from the external power source; and is characterized by having a second monitoring unit that monitors the operating voltage and generates a second monitoring signal, the second monitoring signal indicating that the voltage level of the operating voltage is high At or below a preset monitoring value; and a control unit that operates at the operating voltage and controls the start and stop of the motor based on the information of the first monitoring system signal and the information of the second monitoring system signal. The motor control device according to item 1 of the scope of patent application, wherein the first monitoring unit includes: a branch circuit, which is electrically connected in parallel with the motor at a rear stage of the switch when viewed from the external power source; and a current detection unit , It detects whether the current flows to the branch circuit. The motor control device according to item 2 of the scope of application for a patent, wherein the current detection section has a photocoupler provided in the branch circuit, and the optoelectronic crystal of the photocoupler has a first terminal and a second terminal. The 1 terminal is connected to the voltage supply terminal of the operating voltage through the impedance, the second terminal is connected to the ground potential terminal, and the first monitoring signal is obtained from the first terminal. The motor control device according to item 3 of the scope of patent application, wherein the first monitoring signal is generated as a binary signal, and the binary signal has a first value set between a rated value of the operating voltage and a ground potential. A threshold value and a second threshold value lower than the first threshold value, when the voltage level of the first monitoring signal is higher than the first threshold value, the control unit determines that the first monitoring signal has a first logic value, and when the first monitoring signal has a first logic value, When the voltage level of the monitoring signal is lower than the second threshold, it is determined that the first monitoring signal has a second logic value. The motor control device according to item 4 of the scope of patent application, wherein in a state where the second monitoring signal indicates that the voltage level of the operating voltage is higher than the monitoring value, when the first monitoring signal is changed from the first logic value When changing to the second logic value, the control unit starts the motor, and when the second monitoring signal indicates that the voltage level of the operating voltage is higher than the monitoring value, when the first monitoring signal changes from the second logic value At the first logic value, the control section stops the motor. The motor control device according to item 5 of the scope of patent application, wherein in a state where the second monitoring signal indicates that the voltage level of the operating voltage is lower than the monitoring value, even if the first monitoring signal is changed from the first logic value After changing to the second logic value, the control unit still does not start the motor. The motor control device according to item 5 of the scope of patent application, wherein the monitoring value is set so that when the switch is on, the input power from the external power source to the feeder is suspended, the voltage of the first monitoring signal Before the level is below the threshold, the operating voltage is lower than the monitored value. The motor control device according to any one of claims 5 to 7, wherein when the voltage level of the operating voltage is higher than the monitoring value, the second monitoring unit generates the first logic value with a first logic value. 2 monitoring signal, and when the voltage level of the operating voltage is lower than the monitoring value, the second monitoring unit generates the second monitoring signal with a second logic value. According to the motor control device described in item 8 of the scope of patent application, as long as the second monitoring signal has a second logic value, the control unit does not start the motor regardless of the value of the first monitoring signal. The motor control device according to item 1 of the scope of patent application, wherein immediately after the motor is stopped and before a preset delay time has passed from the stop time, regardless of whether the first monitoring signal or the second monitoring signal is What is the value, the control section keeps the stopped state of the motor. The motor control device according to item 10 of the scope of patent application, wherein when the switch is in an on state and the input power from the external power source is suspended to the feeder, the delay time is set to a voltage level that is in line with the operating voltage It takes the same or slightly longer time for the setting value to fall to the monitoring value. The motor control device according to item 1 of the scope of patent application, wherein immediately after stopping the motor, the control unit repeatedly checks the first monitoring signal and the second monitoring signal within a preset delay time by a predetermined number of times. . The motor control device according to item 12 of the scope of patent application, wherein the delay time is set to be shorter than the time required for the voltage level of the operating voltage to fall from the rated value to the monitored value. The motor control device according to item 1 of the scope of patent application, further includes a switching element, which is electrically connected in series with the motor and the switch with respect to the external power source, and the control unit switches and controls the switching element at a certain frequency to control The rotation operation of the motor turns off the switching element when the motor is stopped. The motor control device according to item 1 of the scope of patent application, wherein the external power source is an AC power source, and the operating voltage generating circuit has an AC-DC conversion circuit that converts AC power input from the AC power source into DC power. The DC conversion circuit has a capacitor in its output section, and outputs the charging voltage of the capacitor as the operating voltage. A motor control device for controlling the operation of a motor that is rotated by receiving power from an external power source includes a switch that is electrically connected in series with the motor with respect to the external power source; and an operating voltage generating circuit whose input comes from the And a first monitoring unit that monitors a state of the switch or a state of a feeder line between the switch and the motor; and includes a second monitoring unit that monitors the state of the switch The voltage level of the operating voltage is higher or lower than a preset monitoring value; and a control unit that operates at the operating voltage and controls the motor based on the monitoring information of the first monitoring unit and the second monitoring unit. Start and stop; in a state where the second monitoring unit gives monitoring information that the voltage level of the operating voltage is higher than the monitoring value, the first monitoring unit gives monitoring information in which the switch is switched from an off state to an on state At the time, the control unit starts the motor in response to the monitoring information from the first monitoring unit; the second monitoring unit gives a voltage level of the operating voltage greater than the monitored value In the state of high monitoring information, when the first monitoring unit gives monitoring information that the power input from the external power source to the feeder is cut off, the control unit stops the response in response to the monitoring information from the first monitoring unit. Motor; in a state where the second monitoring unit gives monitoring information with a voltage level of the operating voltage lower than the monitoring value, the first monitoring unit gives power input from the external power source to the feeder to start or restart When the monitoring information is enabled, the control unit does not start the motor. An electric tool includes: a main body; a movable tool that is mounted to the main body in a manner to perform a certain movement; a motor disposed in the main body for receiving power supply from an external power source to drive the tool; a motor A control device provided in the main body for controlling the operation of the motor by receiving power supply from the external power source includes a switch that is electrically connected in series with the motor relative to the external power source; an operating voltage generating circuit , Which inputs electric power from the external power source and outputs a DC operating voltage; and a first monitoring section, which monitors a state of the switch or a state of a feeder line between the switch and the motor, and generates a first monitoring signal, which The first monitoring signal indicates whether power is supplied to the feeder from the external power source; it is characterized by having a second monitoring unit that monitors the operating voltage and generates a second monitoring signal, the second monitoring signal indicating the operating voltage The voltage level is higher or lower than a preset monitoring value; and a control unit that operates at the operating voltage and is based on the first The information of the monitoring signal and the information of the second monitoring signal control the start and stop of the motor. An electric tool includes: a main body; a movable tool that is mounted to the main body in a manner to perform a certain movement; a motor disposed in the main body for receiving power supply from an external power source to drive the tool; a motor A control device provided in the main body for controlling the operation of the motor by receiving power supply from the external power source includes a switch that is electrically connected in series with the motor relative to the external power source; an operating voltage generating circuit , Which inputs electric power from the external power source and outputs a DC operating voltage; and a first monitoring section, which monitors a state of the switch or a state of a feeder line between the switch and the motor; and is characterized by having: a second monitor A monitoring unit that monitors a voltage level of the operating voltage above or below a preset monitoring value; and a control unit that operates at the operating voltage and is based on monitoring information from the first monitoring unit and the second monitoring unit While controlling the start and stop of the motor; in a state where the second monitoring unit gives monitoring information that the voltage level of the operating voltage is higher than the monitoring value When the first monitoring unit gives monitoring information that the switch is switched from an off state to an on state, the control unit starts the motor in response to the monitoring information from the first monitoring unit; the second monitoring unit gives the operation In the state where the voltage level of the voltage is higher than the monitoring information, when the first monitoring unit gives monitoring information that the power input from the external power source to the feeder is cut off, the control unit responds from the first 1 the monitoring unit stops the motor with the monitoring information; and the second monitoring unit gives the monitoring information that the voltage level of the operating voltage is lower than the monitoring value, and the first monitoring unit gives the information from the external power source to When the power input of the feeder is monitored or restarted, the control section does not start the motor.