JP2012091276A - Power tool and inverter device used for power tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power tool provided with an inverter circuit and capable of alleviating waste of electricity of a battery pack.SOLUTION: A lawn mower 1 includes a motor 32; a boosting circuit section 23 converting a DC electric power from the battery pack 4 into an AC electric power and boosting the AC electric power; a rectifying and smoothing circuit section 24 rectifying and smoothing the boosted AC electric power, and outputting as the AC electric power; a switching circuit 26 converting the DC electric power output from the rectifying and smoothing circuit section 24 into the AC electric power; a trigger switch 31a instructing the AC electric power converted by the switching circuit 26 to be supplied to the motor 32; and a microcomputer 29 controlling the switching circuit 26 to implement conversion after being instructed by the trigger switch 31a. Furthermore, the microcomputer 29 controls the boosting circuit section 23 to operate intermittently until being instructed by the trigger switch 31a.

Description

  The present invention relates to an electric tool and an inverter device used for the electric tool.

  2. Description of the Related Art Conventionally, an electric tool driven by AC power directly supplied from an AC power source to an AC motor, such as a lawn mower, is known (see, for example, Patent Document 1).

JP2009-219428

  A lawnmower driven by an AC power source can work only within the reach of the power cord, so that the work efficiency is poor.

  On the other hand, a lawnmower driven by DC power from a battery pack is also known. In the case of such a lawn mower, the working range is not restricted by the power cord, but the working time is shortened when the power consumption of the battery pack is increased.

  An object of the present invention is to provide an electric tool including an inverter, particularly a lawnmower, which can reduce waste of electric power of a battery pack.

  The power tool of the present invention includes a motor, a booster circuit unit that converts DC power from the battery pack into AC power and boosts the voltage, and a rectifying and smoothing circuit unit that rectifies and smoothes the boosted AC power and outputs the DC power An inverter circuit that converts the DC power output from the rectifying and smoothing circuit unit into AC power, a trigger switch that instructs supply of the AC power converted by the inverter circuit to the motor, and the trigger switch A control unit that controls the inverter circuit to perform the conversion operation after an instruction is given, and the control unit further performs the step-up operation so as to perform an intermittent operation until the instruction is given by the trigger switch. The circuit part is controlled.

  According to such a configuration, since the conversion operation is not performed until instructed by the trigger switch, it is possible to reduce the waste of battery pack power by the inverter. Further, since the booster circuit unit is intermittently driven until instructed by the trigger switch, the voltage of the booster circuit unit can be set to such an extent that the instruction of the trigger switch can be detected, and power consumption of the battery pack by the inverter is wasted. It becomes possible to reduce. In addition, even in a device that does not start unless a high voltage is applied, such as a brushless motor, the instruction by the trigger switch can be reliably detected.

  Moreover, it is preferable that the said control part discriminate | determines the instruction | indication of the said trigger switch by the fall of the boost voltage of the said booster circuit part.

  According to such a configuration, the trigger switch operation can be determined based on the boosted voltage, so that the trigger determination can be easily performed without complicating the configuration.

  The booster circuit unit includes a first switching element for converting DC power from the battery pack into AC power, and a booster circuit for boosting the AC power converted by the first switching element. The controller preferably controls the first switching element until the instruction is given by the trigger switch.

  According to such a configuration, it is possible to reduce the waste of power of the battery pack by the inverter with a simple configuration that only controls the switching element. Furthermore, it is possible to reduce the waste of power by the first switching element.

  In addition, the inverter circuit includes a plurality of second switching elements connected to the motor, and the control unit has only one pair of the plurality of second switching elements until the instruction is given by the trigger switch. It is preferable that all of the plurality of second switching elements are controlled when the voltage of the rectifying / smoothing circuit section is reduced to a predetermined value or less.

  According to such a configuration, since the instruction by the trigger switch can be detected by detecting the voltage of the rectifying and smoothing circuit unit, it is possible to reduce the waste of the battery pack power by the inverter with a simple configuration without increasing the cost. Is possible.

  The rectifying / smoothing circuit unit includes a diode for rectifying the output from the boosting circuit unit and a capacitor for smoothing the output of the rectifying unit, and the control unit until the instruction is made by the trigger switch. The first switching element is controlled to intermittently charge the capacitor, and the first switching device is charged to the target voltage when the voltage of the capacitor drops below a predetermined value. It is preferable to control the element.

  According to such a configuration, it is possible to easily detect an instruction by the trigger switch only by detecting the voltage of the capacitor.

  Moreover, it is preferable that the said control part stops supply of the electric power from the said battery pack to the said inverter, when the overdischarge detection signal is input from the said battery pack.

  According to such a configuration, it is possible to prevent the life of the battery pack from being shortened.

  Further, the inverter can connect a plurality of the battery packs having different voltages, and the control means can control the voltage according to the voltages of the plurality of battery packs so that the voltage of the rectifying and smoothing circuit unit is constant. It is preferable to control the first switching element.

  According to such a configuration, various battery packs can be used, and workability can be improved. Moreover, optimal control can be performed according to the voltage of the connected battery pack.

  The inverter device according to the present invention includes a motor, a booster circuit unit that converts DC power from the battery pack into AC power and boosts it, and rectifies and smoothes the boosted AC power as rectified and smoothed output as DC power. A circuit unit; an inverter circuit that converts DC power output from the rectifying and smoothing circuit unit into AC power; a trigger switch that instructs supply of AC power converted by the inverter circuit to the motor; and the trigger switch And a control unit that controls the inverter circuit to perform the conversion operation after the instruction is given by the control unit, and the control unit further performs an intermittent operation until the instruction is given by the trigger switch. The booster circuit unit is controlled.

  According to such a configuration, since the conversion operation is not performed until instructed by the trigger switch, it is possible to reduce the waste of battery pack power by the inverter. Further, since the booster circuit unit is intermittently driven until instructed by the trigger switch, the voltage of the booster circuit unit can be set to such an extent that the instruction of the trigger switch can be detected, and power consumption of the battery pack by the inverter is wasted. It becomes possible to reduce. In addition, even in a device that does not start unless a high voltage is applied, such as a brushless motor, the instruction by the trigger switch can be reliably detected.

  Moreover, it is preferable that the said control part discriminate | determines the instruction | indication of the said trigger switch by the fall of the boost voltage of the said booster circuit part.

  According to such a configuration, the trigger switch operation can be determined based on the boosted voltage, so that the trigger determination can be easily performed without complicating the configuration.

  The booster circuit unit includes a first switching element for converting DC power from the battery pack into AC power, and a booster circuit for boosting the AC power converted by the first switching element. The controller preferably controls the first switching element until the instruction is given by the trigger switch.

  According to such a configuration, it is possible to reduce the waste of power of the battery pack by the inverter with a simple configuration that only controls the switching element. Furthermore, it is possible to reduce the waste of power by the first switching element.

  In addition, the inverter circuit includes a plurality of second switching elements connected to the motor, and the control unit has only one pair of the plurality of second switching elements until the instruction is given by the trigger switch. It is preferable that all of the plurality of second switching elements are controlled when the voltage of the rectifying / smoothing circuit section is reduced to a predetermined value or less.

  According to such a configuration, since the instruction by the trigger switch can be detected by detecting the voltage of the rectifying and smoothing circuit unit, it is possible to reduce the waste of the battery pack power by the inverter with a simple configuration without increasing the cost. Is possible.

  The rectifying / smoothing circuit unit includes a diode for rectifying the output from the boosting circuit unit and a capacitor for smoothing the output of the rectifying unit, and the control unit until the instruction is made by the trigger switch. The first switching element is controlled to intermittently charge the capacitor, and the first switching device is charged to the target voltage when the voltage of the capacitor drops below a predetermined value. It is preferable to control the element.

  According to such a configuration, it is possible to easily detect an instruction by the trigger switch only by detecting the voltage of the capacitor.

  Moreover, it is preferable that the said control part stops supply of the electric power from the said battery pack to the said inverter, when the overdischarge detection signal is input from the said battery pack.

  According to such a configuration, it is possible to prevent the life of the battery pack from being shortened.

  Further, the inverter can connect a plurality of the battery packs having different voltages, and the control means can control the voltage according to the voltages of the plurality of battery packs so that the voltage of the rectifying and smoothing circuit unit is constant. It is preferable to control the first switching element.

  According to such a configuration, various battery packs can be used, and workability can be improved. Moreover, optimal control can be performed according to the voltage of the connected battery pack.

  According to the electric tool and the inverter device of the present invention, it is possible to reduce the waste of power of the battery pack.

The side view of the lawn mower by 1st Embodiment of the electric tool of this invention. The circuit diagram of the inverter and electric tool by 1st Embodiment. The flowchart about control of the supply voltage to the AC motor by 1st Embodiment. The time chart of the voltage of the step-up circuit unit according to the first embodiment.

  A power tool, for example, a lawnmower 1 according to an embodiment of the present invention will be described with reference to FIGS. 1 to 4.

  FIG. 1 is a side view of the lawn mower 1. The lawn mower 1 includes an inverter 2 that is detachably provided on the lawn mower main body 3 by a latch portion 2A. The operator holds the handle 5 and operates the trigger switch 31 a, whereby the electric power from the battery pack 4 is supplied to the motor 32 via the inverter 2. The lawn mower body 3 is provided with a front wheel 6 provided on the front side in the traveling direction and a rear wheel 7 provided on the rear side, and is configured to be movable. A grass collection bag 8 for collecting grass and the like mowed by a rotary blade (not shown) is detachably provided on the rear side of the main body 3 in the traveling direction.

  FIG. 2 is a circuit diagram of the lawn mower 1. In the present embodiment, the lawn mower 1 includes an inverter 2 and a lawn mower main body 3. When the trigger switch 31 a of the lawn mower main body 3 is operated, the inverter 2 is connected to the battery pack 4. It is assumed that the DC power supplied from is converted into AC power by the inverter 2 and supplied to the brushless motor 32 via the rectification three-phase conversion circuit 31 of the lawn mower body 3. The inverter 2, the lawn mower main body 3, and the battery pack 4 are detachable. In the following description, it is assumed that they are connected.

  The inverter 2 includes a battery voltage detection unit 21, a power supply unit 22, a booster circuit (boost circuit unit) 23, a rectification / smoothing circuit (rectification smoothing circuit unit) 24, a boost voltage detection unit 25, and a switching circuit (inverter). Circuit) 26, a current detection resistor 27, a PWM signal output unit 28, and a microcomputer 29 serving as a control unit.

  The battery voltage detection unit 21 includes resistors 211 and 212 connected in series to each other, detects the voltage from the battery pack 4, and outputs the voltage to the microcomputer 29 as a divided voltage from the connection point between the resistors 211 and 212. . Note that the battery pack 4 shown in FIG. 2 has four 3.6 V / cell lithium battery cells connected in series and outputs a rated voltage of 14.4 V.

  The power supply unit 22 includes a power switch 221 and a constant voltage circuit 222 connected in series between the battery pack 4 and the microcomputer 29. The constant voltage circuit 222 includes a three-terminal regulator 222a and oscillation prevention capacitors 222b and 222c. When the power switch 221 is turned on by the user, the voltage from the battery pack 4 is set to a predetermined DC voltage (for example, 5V) and supplied as drive power to the microcomputer 29. When the power switch 221 is turned off, the driving power is not supplied to the microcomputer 29, so that the entire inverter 2 is turned off.

  The booster circuit 23 includes a transformer 231 and an FET 232 serving as a first switching element. The primary side of the transformer 231 is connected in series between the battery pack 4 and GND, and the FET 232 is disposed between the primary side of the transformer 231 and GND. The gate of the FET 232 is connected to the microcomputer 29, and the FET 232 is turned on / off by a first PWM signal from the microcomputer 29, which will be described later. As a result, the DC power supplied from the battery pack 4 to the primary side of the transformer 231 Is converted to AC power.

  On the secondary side of the transformer 231, a rectification / smoothing circuit 24, a boosted voltage detection unit 25, a switching circuit 26, and a current detection resistor 27 are connected.

  The rectifying / smoothing circuit 24 includes diodes 241 and 242 and a capacitor 243. With these, the AC power boosted by the transformer 231 is rectified and smoothed and output as DC power.

  The boosted voltage detection unit 25 includes resistors 251 and 252 connected in series with each other, detects a DC boosted voltage (capacitor voltage, for example, 140 V) output from the rectification / smoothing circuit 24, and detects the mutual resistance. The divided voltage is output from the connection point to the microcomputer 29.

  The switching circuit 26 is composed of four FETs 261-264 serving as second switching elements. The FETs 261 and 262 connected in series and the FETs 263 and 264 connected in series are connected to the rectifying / smoothing circuit 24. Connected in parallel to the output terminal. Specifically, the drain of the FET 261 is connected to the output terminal (plus side) of the rectifying / smoothing circuit 24, and the source of the FET 261 is connected to the drain of the FET 262. The drain of the FET 263 is connected to the output terminal (plus side) of the rectification / smoothing circuit 24, and the source of the FET 263 is connected to the drain of the FET 264.

  Furthermore, the source of the FET 261 and the drain of the FET 262, the source of the FET 263, and the drain of the FET 264 are connected to output terminals 265 and 266, respectively. The output terminals 265 and 266 are connected to the brushless motor 32 of the lawn mower body 3 via the rectification three-phase conversion circuit 31. The gate of the FET 261-264 is connected to the PWM signal output unit 28, and the FET 261-264 is turned on / off by a second PWM signal from the PWM signal output unit 28, which will be described later. The DC power output from 24 is converted into AC power and supplied to the lawn mower main body 3 (motor 32).

  Note that a commutator motor may be used instead of the brushless motor 32. In this case, the trigger switch is connected in series between the motor and the output terminal 265 or 266.

  The current detection resistor 27 is connected in series between the source of the FET 262 and the source of the FET 264 and GND, and the terminal on the high voltage side of the current detection resistor 27 is connected to the microcomputer 29. With such a configuration, the current detection resistor 27 detects the current flowing through the AC motor 32 and outputs it to the microcomputer 29 as a voltage.

  The microcomputer 29 outputs, to the gate of the FET 232, a first PWM signal for outputting AC power having a target effective voltage from the secondary side of the transformer 231 based on the boosted voltage detected by the boosted voltage detection unit 25. Then, the FET 232 is turned on / off. Further, the microcomputer 29 outputs a second PWM signal for supplying the set power to the AC motor 32 to the PWM signal output unit 28. The PWM signal output unit 28 outputs the second PWM signal output from the microcomputer 29 to the gate of the FET 261-264 to turn on / off the FET 261-264. Specifically, the microcomputer 29 performs a second operation for alternately turning on and off a set of FET 261 and FET 264 (hereinafter referred to as a first set) and a set of FET 262 and FET 263 (hereinafter referred to as a second set) at a duty of 100%. The PWM signal is output.

  Here, the microcomputer 29 of the present embodiment outputs a first PWM signal for intermittently turning on / off the FET 232 to the gate of the FET 32 and the FET 261-when the trigger switch 31 a is not operated. A second PWM signal for turning on only one set, for example, turning on the first set (FETs 261, 264) and turning off the second set (FETs 262, 263) is output. As will be described later, the first PWM signal and the second PWM signal for turning on / off the FET 232 and the four FETs (FETs 261-264) are not detected until the microcomputer 29 detects the operation of the trigger switch 31a. Output.

  In the configuration as described above, the DC power from the battery pack is converted into AC power by the inverter 2 (particularly the switching circuit 26) and then supplied to the brushless motor 32. Various controls are required, and in the process of the control It is conceivable that power is wasted. However, in this embodiment, when the trigger switch 31a is not operated, the FET 232 oscillates intermittently, and only the FET 261 and the FET 264 (first set) are controlled to be turned on. At the same time, it is possible to prevent failure of the FET 232 and the FET 261-264 due to heat generation.

  Furthermore, the microcomputer 29 determines overdischarge of the battery pack 4 based on the battery voltage detected by the battery voltage detection unit 21. Specifically, when the battery voltage detected by the battery voltage detection unit 21 is equal to or lower than a predetermined value, it is determined that the battery pack 4 is over-discharged, and the second for turning off the FETs 232 and 261-264 1 PWM signal and 2nd PWM signal are output. Further, the battery pack 4 includes a protection IC and a microcomputer therein, and has a function of detecting overdischarge by itself and outputting an overdischarge signal to the microcomputer 29. The microcomputer 29 is overdischarged from the signal terminal LD. Even when the signal is received, the first PWM signal and the second PWM signal for turning off the FETs 232 and 261-264 are output. With such a configuration, it is possible to prevent the life of the battery pack 4 from being shortened.

  Next, the control of the supply voltage to the lawn mower 3 by the microcomputer 29 in the present embodiment will be described using the flowchart of FIG. 3 and the time chart of FIG.

  3 is a flowchart when the power switch 221 is turned on while the battery pack 4 is attached to the inverter 2, or when the battery pack 4 is attached to the inverter 2 while the power switch 221 is turned on. Start. When the power switch 221 is turned on, a voltage is supplied from the voltage of the battery pack 4 to the constant voltage circuit 222, so that the driving voltage of the microcomputer 29 is generated and the microcomputer 29 operates.

  First, the microcomputer 29 performs the intermittent oscillation operation S201 of the FET 232 composed of S202 to S204. When the microcomputer 29 is driven, a signal for oscillating (the FET 232 oscillation period in FIG. 4) / stopping (the FET 232 inactive period in FIG. 4) is output to the gate of the FET 232 (S202a, S202b). Then, the FET 261 and the FET 264 are turned on, and a voltage is output between the output terminals 265 and 266 (S203).

  Thereafter, it is determined whether or not a predetermined time has elapsed since the intermittent oscillation stop of the FET 232 (S204). If it has elapsed, the voltage charged in the capacitor 243 of the rectifying and smoothing circuit unit 24 detected by the boost voltage detecting unit 25 Based on the (boosted voltage), the boosted voltage drop rate in the pause period of intermittent oscillation of the FET 232 is calculated (S205).

  The determination in S204 is not always necessary, but this determination is provided because a certain amount of time is required to detect an accurate voltage drop. Further, as will be described later, even when the trigger switch 31a is not operated, a slight amount of power is consumed by the boosted voltage detector 25 and the like, and the voltage drop of the capacitor 243 varies depending on conditions such as temperature. By providing a predetermined time, it is possible to accurately determine a normal voltage drop (due to a leakage current or the like) and a voltage drop due to tool connection.

  Here, when the lawn mower 3 is connected to the inverter 2 and the trigger switch 31a is operated (trigger switch on in FIG. 4), the capacitor 243 is operated by the action of a control circuit (not shown) such as an inverter control circuit of a brushless motor. Is applied to the brushless motor 32 via the FETs 261 and 264. Then, since power consumption increases, the voltage drop of the output voltage (charge voltage of the capacitor 243) during the pause period of the FET 232 becomes large (large voltage drop in FIG. 4). In the present embodiment, based on this voltage drop (boost voltage drop rate), it is determined whether or not the trigger switch 31a has been operated (S206).

  When the lawn mower 3 is not connected to the inverter 2 or when the brushless motor 32 is not operating even when the lawn mower 3 is connected (the first FET 232 pause period in FIG. 4), the rectifying / smoothing circuit The voltage drop of the capacitor 243 in the unit 24 is small (consumption caused by leakage current from the boosted voltage detection unit 25 and the like), and the FET 232 can maintain the voltage even in the intermittent oscillation operation as described above. small. Accordingly, when the boost voltage drop rate is equal to or lower than the predetermined value (S206: NO), it is determined that the trigger switch 31a is not operated, and the process returns to S201 and the intermittent oscillation operation of the FET 232 is repeated.

  On the other hand, if the boost voltage drop rate is greater than the predetermined value (S206: YES), it is determined that the trigger switch 31a has been operated. At this time, as the voltage output to the output terminals 265 and 266 is lower, the power consumption can be reduced. However, if the output voltage is too low, the voltage applied to the rectification three-phase conversion circuit 31 of the lawn mower 3. Is too low, a control circuit (not shown) built in the lawn mower 3 does not start, and the lawn mower 3 cannot be started. Therefore, it is desirable that the voltage charged in the capacitor 243 during intermittent operation is about DC voltage 80 to 120V. Further, when the voltage charged in the capacitor 243 is within the above range, the predetermined value is preferably about 20V to 50V. Note that if the motor of the lawn mower 3 is a commutator motor, the charging voltage of the capacitor 243 during intermittent operation can be further reduced, and power consumption can be suppressed.

  When the boost voltage drop rate is larger than the predetermined value (S206: YES, voltage drop detection in FIG. 4), a signal for continuously oscillating the FET 232 is output so as to drive the boost circuit unit 23 continuously. (S207), the output voltage of the booster circuit unit 23, that is, the voltage of the capacitor 243 of the rectifying / smoothing circuit unit 24 is controlled to be a target value (S207-S210, FET232 continuous oscillation section of FIG. 4). At this time, the voltage target value of the capacitor 243 is preferably 140V. That is, the voltage (detection voltage) of the capacitor 243 is compared with the target value (S208), and when the detection voltage is lower than the target value, the duty ratio of the FET 232 is increased (S209). Conversely, the detection voltage is higher than the target value. In this case, the duty ratio of the FET 232 is decreased (S210), and the first PWM signal is output so that the voltage of the capacitor 243 becomes the target value 140V to control the FET 232.

  Subsequently, the microcomputer 29 outputs a second PWM signal for turning on and off the switching circuit 26 (FET 261-264) via the PWM signal output unit 28, and an AC voltage (100 V) is output to the output terminals 265 and 266. Is supplied (S211). That is, the first set (FETs 261 and 264) and the second set (FETs 262 and 263) of the switching circuit 26 are alternately turned on and off.

  Subsequently, it is determined whether or not the battery voltage detected by the battery voltage detector 21 is smaller than a predetermined overdischarge voltage (S212). If the voltage is smaller than the predetermined overdischarge voltage (S212: YES), it is determined that the battery pack 4 is in the overdischarge state, and the first PWM signal and the second PWM signal for turning off the FET232 and the FET261-264 are determined. Is output to stop the operation of the booster circuit unit 23 and the switching circuit 26 (S214). Thereby, the supply of power from the battery pack 4 is stopped.

  If the battery voltage is equal to or higher than the predetermined overdischarge voltage (S212: NO), it is determined whether or not an overdischarge signal is input from the battery pack 4 via the LD terminal (S213). If an overdischarge signal has been input (S213: YES), it is determined that the battery pack 4 or at least one battery cell is in an overdischarge state, and the operations of the booster circuit 23 and the switching circuit 26 are stopped (S214). ).

  On the other hand, if no overdischarge signal is input (S213: NO), it is determined whether or not current is flowing through the motor based on the signal from the current detection resistor 27 (S215). When there is no motor current (S215: NO), it is determined whether or not a predetermined time has elapsed (S216). If the predetermined time has elapsed (S216: YES), it is determined that the lawn mower 3 is not operating, the operation of the booster circuit unit 23 and the switching circuit 26 is stopped (S217), and the intermittent oscillation operation of S201 is performed. Return. The intermittent oscillation operation continues until the power switch 221 is turned off.

  With such an operation, the power consumption of the battery pack 4 during standby can be suppressed. In addition, since the operation is automatically switched to the intermittent oscillation operation, the operability can be improved. Note that a manually operable switch or the like may be provided, and the lawn mower 3 may be manually switched to the intermittent oscillation operation after use.

  If there is a motor current (S215: YES), and if the predetermined time has not passed (S216: NO), it is determined that the lawn mower 3 is operating, and the booster circuit unit 23 and the switching circuit 26 in S207 Return to continuous operation.

  As described above, in the configuration in which the DC power from the battery pack 4 is converted to AC power by the inverter 2 (switching circuit 26) and then supplied to the brushless motor 32, various controls are required. Although it is conceivable that power is wasted, in the present embodiment, the FET 232 oscillates intermittently when the trigger switch 31 a is not operated, and the FET 261 and the FET 264 of the FET 261 to the FET 264 of the switching circuit 26. Therefore, it is possible to reduce the waste of electric power and suppress the heat generation of the FET 232 and the FET 261-264 and prevent the failure.

  The power tool of the present invention is not limited to the above-described embodiment, and various modifications and improvements can be made within the scope described in the claims.

  For example, in the above embodiment, when a further FET is arranged in series with the power switch 221 and the battery pack 4 detects overdischarge, a configuration is adopted in which an overdischarge signal is sent to the gate of the FET. May be. With such a configuration, it is possible to prevent the life of the battery pack 4 from being shortened.

  Moreover, in the said embodiment, although the battery pack 4 connected to the inverter 2 was demonstrated as 14.4V, any of the battery packs which consist of different types of battery packs, for example, a lithium battery, a nickel-cadmium battery, or a nickel metal hydride battery May be connectable, or a plurality of battery packs having different battery voltages may be connectable. In this case, the battery pack is provided with identification means (for example, a resistor) in order to identify the battery voltage and type, and the microcomputer 29 determines the connected battery pack based on information from this resistor, and the FET 232 according to the battery pack. If the intermittent drive timing is controlled to be changed, various battery packs can be used and workability can be improved.

  In the flowchart of FIG. 3, the boosted voltage is controlled in S207 to S210. However, these may be performed at any position in the flowchart as long as the trigger is detected in S201. Moreover, although overdischarge was detected by S212-S214, these may be performed in any position in a flowchart, and may be performed in parallel.

1: lawn mower, 2: inverter, 3: lawn mower main body, 4: battery pack, 23: booster circuit unit, 24: rectifying and smoothing circuit unit, 26: switching circuit, 27: current detection resistor, 29: microcomputer, 31: Rectification three-phase conversion circuit, 32 brushless motor

Claims (14)

A motor,
A booster circuit unit that converts DC power from the battery pack into AC power and boosts the power;
A rectifying / smoothing circuit for rectifying and smoothing the boosted AC power and outputting the DC power as DC power;
An inverter circuit that converts the DC power output from the rectifying and smoothing circuit unit into AC power;
A trigger switch for instructing supply of the AC power converted by the inverter circuit to the motor;
A control unit that controls the inverter circuit to perform the conversion operation after the instruction is given by the trigger switch;
With
The control unit further controls the booster circuit unit to perform an intermittent operation until the instruction is given by the trigger switch.   The power tool according to claim 1, wherein the control unit determines an instruction of the trigger switch based on a decrease in a boosted voltage of the booster circuit unit. The booster circuit unit includes a first switching element for converting DC power from the battery pack into AC power, and a booster circuit that boosts AC power converted by the first switching element,
The power tool according to claim 1, wherein the control unit controls the first switching element to perform an intermittent operation until the instruction is given by the trigger switch. The inverter circuit includes a plurality of second switching elements connected to the motor,
The control unit turns on only a pair of the plurality of second switching elements until the instruction is made by the trigger switch, and when the voltage of the rectifying / smoothing circuit unit drops below a predetermined value, The power tool according to claim 3, wherein all of the plurality of second switching elements are controlled. The rectifying and smoothing circuit unit includes a diode that rectifies the output from the boosting circuit unit, and a capacitor that smoothes the output of the rectifying unit,
The control unit controls the first switching element to intermittently charge the capacitor until the instruction is given by the trigger switch, and when the voltage of the capacitor is reduced to a predetermined value or less. The power tool according to claim 3 or 4, wherein the first switching element is controlled to charge the capacitor to a target voltage.   The said control part stops supply of the electric power from the said battery pack to the said inverter circuit, when an overdischarge detection signal is input from the said battery pack. The electric tool according to item. The inverter circuit can connect a plurality of the battery packs having different voltages,
The control means controls the first switching element according to the voltages of the plurality of battery packs so that the voltage of the rectifying / smoothing circuit unit is constant. The electric tool according to one item. A booster circuit unit that converts DC power from the battery pack into AC power and boosts the power;
A rectifying / smoothing circuit for rectifying and smoothing the boosted AC power and outputting the DC power as DC power;
An inverter circuit that converts the DC power output from the rectifying and smoothing circuit unit into AC power;
A trigger switch for instructing the supply of AC power converted by the inverter circuit to the motor;
A control unit that controls the inverter circuit to perform the conversion operation after the instruction is given by the trigger switch;
With
The inverter unit further controls the booster circuit unit to perform an intermittent operation until the instruction is given by the trigger switch.   The inverter device according to claim 8, wherein the control unit determines an instruction of the trigger switch based on a decrease in a boosted voltage of the booster circuit unit. The booster circuit unit includes a first switching element for converting DC power from the battery pack into AC power, and a booster circuit that boosts AC power converted by the first switching element,
The inverter device according to claim 8 or 9, wherein the control unit controls the first switching element to perform an intermittent operation until the instruction is given by the trigger switch. The inverter circuit includes a plurality of second switching elements connected to the motor,
The control unit turns on only a pair of the plurality of second switching elements until the instruction is made by the trigger switch, and when the voltage of the rectifying / smoothing circuit unit drops below a predetermined value, The inverter device according to claim 10, wherein all of the plurality of second switching elements are controlled. The rectifying and smoothing circuit unit includes a diode that rectifies the output from the boosting circuit unit, and a capacitor that smoothes the output of the rectifying unit,
The control unit controls the first switching element to intermittently charge the capacitor until the instruction is given by the trigger switch, and when the voltage of the capacitor is reduced to a predetermined value or less. The inverter device according to claim 10, wherein the first switching element is controlled to charge the capacitor to a target voltage.   13. The control unit according to claim 8, wherein when an overdischarge detection signal is input from the battery pack, the control unit stops supply of power from the battery pack to the inverter circuit. The inverter device described in the paragraph. The inverter circuit can connect a plurality of the battery packs having different voltages,
The said control means controls the said 1st switching element according to the voltage of these battery packs so that the voltage of the said rectification smoothing circuit part may become fixed, The any one of Claim 8 thru | or 13 characterized by the above-mentioned. The inverter device according to one item.

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