JP2012030318A5 - - Google Patents

Description

Electric tool

  The present invention relates to a power 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).

JP 2009-219428 A

  A lawn mower driven by an AC power source can work only within the reach of the power cord, resulting in poor work efficiency.

  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 voltage conversion unit that converts an input voltage and supplies the motor, an operation detection unit that detects a startup operation of the motor in a state where the operation of the voltage conversion unit is stopped, It is characterized by having.

The power tool of the present invention includes a switch for instructing power supply to the motor and a control unit for controlling the voltage conversion unit, and the operation detection unit is a separate system from the voltage conversion unit. Preferably, the control unit activates the voltage conversion unit after the switch is operated.

The power tool of the present invention includes a power switch for starting the control unit, and the operation detection unit applies the input voltage to the motor when the power switch and the switch are turned on. It is preferable to do.

A power supply device of the present invention is connected to an electric device having a motor, detects a start-up operation of the motor in a state where the operation of the voltage conversion unit that converts an input voltage and supplies the motor to the motor is stopped And a motion detection unit that performs the above-described operation.

The power supply device of the present invention includes a switch that instructs power supply to the motor, and a control unit that controls the voltage conversion unit, and the operation detection unit is a separate system from the voltage conversion unit. Preferably, the control unit activates the voltage conversion unit after the switch is operated.

The power supply apparatus of the present invention further includes a power switch for starting the control unit, and the operation detection unit applies the input voltage to the motor when the power switch and the switch are turned on. It is preferable to do.

The power tool of the present invention includes a motor, an inverter that converts DC power from a battery pack into AC power, a trigger switch that instructs the motor to supply the AC power, and after the instruction is given by the trigger switch And a control unit that controls the inverter so as to perform the conversion operation.

According to such a configuration, since the inverter is controlled so as not to perform the conversion operation until instructed by the trigger switch, it is possible to reduce waste of battery pack power by the inverter.

The power tool of the present invention includes a first switching element for converting DC power from the battery pack into AC power, a booster circuit that boosts AC power converted by the first switching element, A rectifying / smoothing circuit that rectifies and smoothes the boosted AC power and outputs it as DC power, and a transmission unit that directly transmits DC power from the battery pack to the motor when the trigger switch is instructed. The control unit determines that the instruction is given by the trigger switch when the DC power from the battery pack is transmitted to the motor via the transmission unit, and the control unit Then, after the instruction is made by the trigger switch, the conversion operation by the first switching element and the conversion operation by the inverter are performed. It is preferable to control the first switching element and the inverter.

According to such a configuration, the first switching element is controlled not to perform the conversion operation in addition to the inverter until an instruction is given by the trigger switch, so that the waste of power of the battery pack is further reduced. Is possible.

The power tool of the present invention includes a first switching element for converting DC power from the battery pack into AC power, a booster circuit that boosts AC power converted by the first switching element, A rectifying / smoothing circuit that rectifies and smoothes the boosted AC power and outputs the DC power as DC power, and the inverter includes a plurality of second switching elements connected to the motor. The unit turns on only one second switching element until the instruction is given by the trigger switch, and direct current power from the rectifying / smoothing circuit is supplied from the second switching element to the motor. When it is output, it is determined that the instruction is given by the trigger switch, and the control unit is configured after the instruction is given by the trigger switch. It is characterized by controlling the inverter to perform a conversion operation by the inverter.

According to such a configuration, it is possible to reduce waste of power of the battery pack without increasing the number of parts and the cost.

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.

The power tool of the present invention detects a motor, an inverter that converts DC power from the battery pack into AC power, a trigger switch that instructs the motor to supply the AC power, and an operation of the trigger switch. A trigger detection unit and a control unit that controls a power conversion operation of the inverter when the trigger detection unit detects an ON operation of the trigger switch are provided.

According to such a configuration, since the power conversion operation of the inverter is performed after the trigger switch operates, it is possible to reduce the waste of the battery pack power by the inverter.

Further, a booster circuit unit that converts DC power from the battery pack into AC power and boosts the voltage, a rectifying and smoothing circuit unit that rectifies and smoothes the AC power boosted by the booster circuit unit, and the rectifying and smoothing circuit unit An inverter circuit unit that converts the direct current output into alternating current, and the control unit preferably starts the boosting operation of the boosting circuit unit when the trigger detection unit detects an ON operation of the trigger switch. .

The boosting circuit unit includes a first switching element connected in series with the battery pack, and a boosting circuit that boosts AC power converted by the first switching element, and the control unit includes: It is preferable that the control of the first switching element is started when the trigger detection unit detects an ON operation of the trigger switch.

According to such a configuration, since the booster circuit portion, particularly the first switching element, is controlled after the trigger switch is operated, it is possible to reduce the waste of battery pack power when the trigger switch is not operating. It becomes possible.

The inverter circuit includes a plurality of second switching elements, and the control unit starts control of the second switching elements when the trigger detection unit detects an ON operation of the trigger switch. Is preferred.

According to such a configuration, since the second switching element of the inverter circuit unit is controlled after the trigger switch operates, it is possible to reduce waste of battery pack power when the trigger switch is not operating. It becomes.

In addition, the battery pack and the motor are connected, and when the trigger switch is turned on, the battery pack and the motor include a bypass circuit unit (transmission unit) that transmits DC power from the battery pack to the trigger detection unit. Preferably, the on-operation of the trigger switch is detected by applying a voltage of the battery pack through the bypass circuit unit and the motor.

According to such a configuration, in order to detect the ON operation of the trigger switch by applying the battery voltage to the trigger detection unit via the bypass circuit unit, the conversion operation for converting the direct current from the battery pack into the alternating current is performed. Therefore, it is possible to detect the on-operation of the trigger switch, and to reduce the waste of power of the battery pack.

The inverter may include a main switch connected to the battery pack for starting the control unit, and the bypass circuit unit may be connected to the opposite side of the main switch to the battery pack.

According to such a configuration, since one end of the bypass circuit unit is connected to the anti-battery pack side of the main switch, the battery voltage is not applied to the bypass circuit unit unless the main switch is turned on. Power consumption can be pushed.

Moreover, it is preferable that the said trigger detection part has several resistance connected in series with the said motor.

According to such a configuration, the trigger detection unit can be configured with a simple configuration.

In addition, a booster circuit unit that converts DC power from the battery pack into AC power and boosts the voltage, a rectifying and smoothing circuit unit that rectifies and smoothes the AC power boosted by the booster circuit unit, and a plurality of switching elements. Preferably, an inverter circuit unit that converts direct current from the battery pack into alternating current is provided, and the control unit maintains one of the plurality of switching elements in an on state before the trigger switch is turned on.

With such a configuration, a closed circuit for detecting the on-operation of the trigger switch can be configured with a simple configuration by turning on one of the switching elements.

In addition, a closed circuit is formed by the switching element, the motor, and the trigger detection unit that are maintained in the ON state, and the control unit increases the boost when the trigger detection unit detects an ON operation of the trigger switch. It is preferable to increase the output from the circuit section.

According to such a configuration, it is possible to detect the on-operation of the trigger switch with a simple configuration, and it is possible to suppress power consumption of the battery pack before the trigger switch is turned on.

The plurality of switching elements include at least two switch groups in which two switching elements are connected in series, and each of the two switch groups is electrically connected to a positive side of the battery pack. 1 switching element and a second switching element electrically connected to the negative side of the battery pack, and the switching element that maintains the ON state is one of the first switching elements of two switch groups. The trigger operation detector is preferably connected in parallel to the other second switching element of the two switch groups.

According to such a configuration, a closed circuit to which the battery voltage is applied when the trigger switch is turned on can be formed with a simple configuration.

Moreover, it is preferable that the said control part stops the power conversion operation | movement of the said inverter, when an 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.

According to the electric tool of the present invention, it is possible to reduce the waste of electric 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 circuit diagram of the inverter and electric tool by 2nd Embodiment.

A power tool such as a lawnmower 1 according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3.

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 a trigger switch 31 described later, 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 the inverter 2 and the lawn mower main body 3 as described above. When the trigger switch 31 of the lawn mower main body 3 is operated, the inverter 2 Assumes that the DC power supplied from the battery pack 4 is converted into AC power by the inverter 2 and supplied to the AC motor 32 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 section) 26, current detection resistor 27, PWM signal output section 28, microcomputer 29 serving as a control section, power switch detection diode 10, and trigger detection section 11.

The battery voltage detection unit 21 includes resistors 211 and 212 connected in series with each other, detects a voltage from the battery pack 4, and outputs the detected voltage to the microcomputer 29 as a divided voltage. In the present embodiment, the battery pack 4 is connected with four 3.6 V / cell lithium battery cells and outputs a rated voltage of 14.4 V.

The power supply unit 22 includes a power switch (main 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 preventing capacitors 222b and 222c. When the power switch 221 is turned on by the user, the voltage 14.4V from the battery pack 4 is supplied to a predetermined direct current. The voltage is converted to a voltage (for example, 5 V) and supplied to the microcomputer 29 as drive power. 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 (boost circuit unit) 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 boosted to AC power.

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

The rectifying / smoothing circuit (rectifying / smoothing circuit unit) 24 includes diodes 241 and 242 and a capacitor 243. By these, the AC power boosted by the transformer 231 is rectified and smoothed to be DC power (for example, 141V). ) Is output.

The boosted voltage detector 25 includes resistors 251 and 252 connected in series with each other, detects a DC boosted voltage (for example, 141 V) output from the rectifying / smoothing circuit 24, and uses the microcomputer 29 as a divided voltage. Output to.

The switching circuit (inverter circuit unit) 26 is composed of four FETs 261 to 264 that serve as second switching elements, and is connected in series with FETs 261 and 262 (first switch group) connected in series. FETs 263 and 264 (second switch group) are connected in parallel to the output terminal of the rectifying / smoothing circuit 24. 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.

Further, the source of the FET 261 and the drain of the FET 262 are connected to the first terminal 32 a of the AC motor 32 of the lawn mower body 3 via the trigger switch 31, and the source of the FET 263 and the drain of the FET 264 are connected to the AC motor 32. It is connected to the second terminal 32b. 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 AC motor 32 of the lawn mower body 3.

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 power switch detection diode 10 has an anode connected to the low voltage side of the power switch 221 and a cathode connected to the first terminal 32 a of the AC motor 32 of the lawn mower body 3. With such a configuration, when the power switch 221 is turned on, the battery voltage from the battery pack 4 is applied to the AC motor 32. Since the cathode of the power switch detection diode 10 is also connected to the source of the FET 261, the boosted power output from the rectifying / smoothing circuit 24 is applied to the AC motor 32 when the FET 261 is on. Will be. A circuit that includes the power switch detection diode 10 and applies the battery voltage to the AC motor 32 when the power switch 221 is turned on constitutes a bypass circuit. Specifically, a circuit connected to the low voltage side of the power switch 221 and connected to the AC motor 32 via the diode 10 and the trigger switch 31 is a bypass circuit. With this configuration, since the battery voltage is not applied to the AC motor 32 unless the power switch 221 is turned on, wasteful power consumption when the inverter 2 is not driven can be suppressed.

The trigger detection unit 11 includes resistors 111 and 112 connected in series between the second terminal 32b of the AC motor 32 and the source of the FET 264 (that is, GND), and when the trigger switch 31 is operated. The voltage divided by the resistors 111 and 112 is output to the microcomputer 29 as a trigger detection signal. That is, the battery voltage of the battery pack 4 is connected to one end of the trigger switch 31 via the bypass circuit. When the trigger switch 31 is turned on, the battery voltage of the battery pack 4 is applied to the trigger detection unit 11 via the bypass circuit, the trigger switch 31, and the AC motor 32. The applied voltage is divided by the resistors 111 and 112 to be detected as a trigger detection signal and output to the microcomputer 29. The trigger detection unit 11 is connected in parallel with the FET 264.

In this embodiment, the bypass circuit is connected to the source side of the FET 261 and the trigger detection unit 11 is connected in parallel to the FET 264. However, the bypass circuit is connected to the source side of the FET 263 and the trigger detection unit 11 is connected in parallel to the FET 262. May be.

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 according to the present embodiment is configured to turn off the FET 232 and the FET 261 to the FET 264 when the trigger switch 31 is not operated, that is, when the trigger detection signal is not input from the trigger detection unit 11. The first PWM signal and the second PWM signal are output, and the first PWM signal and the second PWM for turning on / off the FET 232 and the FET 261-264 are only when the trigger detection signal is input. Output a signal. In the configuration in which the DC power from the battery pack 4 is converted into AC power by the inverter circuit 26 and supplied to the AC motor 32 as described above, various controls are required, and power is wasted during the control process. It is possible that this will occur. However, in the present embodiment, when the trigger switch 31 is not operated, the FET 232 and the FET 261 to the FET 264 are controlled so as not to be turned on. It is also possible to prevent the failure of the FET 261-264. Since power is not supplied from the battery pack 4 to the microcomputer 29 unless the power switch 221 is turned on, the power consumption of the battery pack 4 is wasted by turning off the power switch 221 when not working. Can be further reduced.

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 from the LD terminal to the microcomputer 29. The first PWM signal and the second PWM signal for turning off the FETs 232 and 261-264 are also output when the signal is received. 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 AC motor 32 by the microcomputer 29 in the present embodiment will be described using the flowchart 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, the microcomputer 29 is driven by generating the driving voltage of the microcomputer 29 by the constant voltage circuit 222 from the battery voltage of the battery pack 4.

First, the microcomputer 29 determines whether or not a trigger detection signal is input from the trigger detection unit 11 (S201). That is, it is determined whether or not the battery voltage of the battery pack 4 is applied to the trigger detection unit 11 via the bypass circuit including the power switch detection diode 10. When the trigger detection signal is input (S201: YES), it is determined that the trigger switch 31 is turned on, and the first PWM signal for turning on / off the FET 232 serving as the first switching element is input to the FET 232. The voltage is output to the gate, and the transformer 231 performs a boosting operation (S202).

Subsequently, based on the boosted voltage detected by the boosted voltage detector 25, it is determined whether or not the boosted voltage is larger than the target voltage (S203). When the voltage is larger than the target voltage (S203: YES), the first PWM signal with a reduced duty is output to the gate of the FET 232 (S204). When the voltage is lower than the target voltage (S203: NO), the duty is increased. The first PWM signal is output to the gate of the FET 232 (S205).

Subsequently, a second PWM signal for turning on / off the FET 261-264 serving as a second switching element constituting the inverter circuit unit 26 is output, and an AC voltage is supplied to the AC motor 32 (S 206). The second PWM signal is output from the PWM signal output unit 28 to the gates of the FETs 261-264.

Subsequently, it is determined whether or not the battery voltage detected by the battery voltage detector 21 is smaller than a predetermined overdischarge voltage (S207). When the voltage is smaller than the predetermined overdischarge voltage (S207: YES), it is determined that the battery pack 4 is in an 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 23 and the switching circuit 26 (S208). 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 (S207: NO), it is determined whether an overdischarge signal is input from the battery pack 4 (S209). When the overdischarge signal is input (S209: YES), the operation of the booster circuit 23 and the switching circuit 26 is stopped in the same manner as when the battery voltage is smaller than the predetermined overdischarge voltage (S207: YES) ( S208). On the other hand, when the overdischarge signal is not input (S209: NO), it is determined again whether the trigger detection signal is input from the trigger detection unit 11 (S210). When the trigger detection signal is input (S210: YES), the process returns to S202. When the trigger detection signal is not input (S210: NO), the operation of the booster circuit 23 and the switching circuit 26 is stopped. (S211), the process returns to S201.

Although overdischarge detection of the battery pack 4 is performed by both the battery pack 4 and the inverter 2, the threshold value of the overdischarge voltage is set smaller in the inverter 2 than in the battery pack 4. Conversely, when the overdischarge threshold set in the battery pack 4 is smaller, the order of S207 and S209 is reversed. That is, in this embodiment, since overdischarge detection of the battery pack 4 is performed by both the battery pack 4 and the inverter 2, overdischarge can be reliably prevented. Similarly, not only overdischarge but also overcurrent can be detected by both the battery pack 4 and the inverter 2 to prevent overcurrent.

As described above, in the configuration in which the DC power from the battery pack is converted to AC power by the inverter circuit and then supplied to the AC motor, various controls are required, and power is wasted in the control process. In this embodiment, in the state where the trigger switch 31 is not operated, the FET 232 and the FET 261 to the FET 264 are controlled so as not to be turned on. H.264 failure can also be prevented. In this embodiment, the booster circuit 23, the rectifying / smoothing circuit 24, and the switching circuit 26 are configured not to operate when the trigger switch 31 is not operated. However, only one of them is prevented from operating. However, waste of power can be reduced.

Next, a lawnmower 10 according to a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a circuit diagram of the lawn mower 1 according to the second embodiment. In FIG. 4, the same components as those in FIG. 2 are denoted by the same reference numerals as those in FIG.

In the second embodiment, instead of including the power switch detection diode 10 (bypass circuit) in the first embodiment, when no trigger detection signal is input from the trigger detection unit 11, the microcomputer 29 Outputs a first PWM signal for turning on / off the FET 232, and simultaneously outputs a second PWM signal for turning on only the FET 261 of the FETs 261-264. In such a configuration, when the power switch 221 is turned on, the DC voltage output from the rectifying / smoothing circuit 24 is applied to the AC motor 32. When the trigger switch 31 is operated and a trigger detection signal is input from the trigger detection unit 11, a second PWM signal for turning on / off all of the FETs 261 to 264 is output. In the present embodiment, the step-up operation of S202 in the flowchart of FIG. 3 is performed prior to the determination of whether or not the trigger detection signal of S201 is input.

When the power switch 221 of the inverter 2 is turned on, the constant voltage circuit 22 generates power for the microcomputer 29 and the microcomputer 29 is activated. The microcomputer 29 outputs an on / off signal (PWM signal) to the FET 232 serving as the first switching element. The booster circuit 23 boosts the battery voltage to an arbitrary voltage, and the rectifying / smoothing circuit 24 rectifies and smoothes the boosted voltage and outputs it to the switching circuit 26.

Here, the switching circuit 26 includes four FETs 261 to 264 that serve as second switching elements. The FETs 261 and 262 (first switch group) connected in series, the FET 263 connected in series, and H.264 (second switch group) is connected in parallel to the output terminal of the rectifying / smoothing circuit 24.

Regarding the first switch group (FETs 261 and 262), 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 source of the FET 262 is connected to the output terminal (minus side) of the rectification / smoothing circuit 24. Similarly, for the second switch group (FETs 263 and 264), the drain of the FET 263 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 source of the FET 262 is connected to the output terminal (minus side) of the rectification / smoothing circuit 24. Furthermore, the first switch group and the second switch group are connected in parallel. Here, in FIG. 3, FETs 261 and 263 located on the upper side are first switching elements, and FETs 262 and 264 located on the lower side are second switching elements.

When the power switch 221 is turned on, the microcomputer 29 controls the FET 232 to be turned on and off, and controls one of the first switch group and the second switch group, which is the FET 261 in the present embodiment. A command is output to the PWM signal output unit 28 so as to be always turned on. As a result, the voltage boosted by the booster circuit 23 is converted into direct current by the rectifying / smoothing circuit 24 and applied to one end of the trigger switch 31 via the FET 261.

On the other hand, among the first switch group and the second switch group, the trigger detection unit 11 is provided in parallel with the other second switching element, in the present embodiment, the FET 264.

When the trigger switch 31 is turned on, a closed circuit is formed by the FET 261, the trigger switch 31, the AC motor 32, and the trigger detection unit 11, and the output (DC voltage) of the rectification / smoothing circuit 24 is applied to the trigger detection unit 11. The microcomputer 29 can detect the ON operation of the trigger switch 31 by inputting the voltage divided by the trigger detection unit 11.

When the microcomputer 29 detects that the trigger switch 31 is turned on, the microcomputer 29 controls on / off of the FET 232 and also controls on / off of the four FETs 261-264, and the DC output of the rectifying / smoothing circuit 24 is switched to a switching circuit (inverter). Circuit) 26 to convert to AC and provide AC motor 32 with AC output.

In order to detect the on operation of the trigger switch 31, the FET 261 is turned on and the trigger detection unit 11 is provided in parallel with the FET 264. However, the FET 263 is turned on and the trigger detection unit 11 is connected in parallel with the FET 262. The structure provided may be sufficient. That is, the FET may be controlled and a trigger detection unit provided so that a closed circuit is formed by the FET, the trigger switch, and the trigger detection unit.

As described above, in the present embodiment, the microcomputer 29 controls the FET 232 to be turned on / off at the same time that only the FET 261 of the FETs 261 to 264 is turned on when the trigger switch 31 is not operated. Therefore, waste of power can be reduced, and at the same time, failure of the FET 232 and the FET 261-264 due to heat generation can be prevented. In addition, since the power switch detection diode 10 is not provided, the number of parts and the cost can be reduced.

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. The power tool is not limited to a lawn mower, and is a hedge trimmer, circular saw. Any electric tool that can be applied to a jigsaw, grinder, driver, etc. and that has a trigger switch and is driven by AC power may be used.

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. That is, the power supply of the microcomputer 29 may be shut off. With such a configuration, it is possible to prevent the life of the battery pack 4 from being shortened. In particular, since no power is supplied to the microcomputer 29, the life of the battery pack 4 can be further extended. Further, a notification unit (display, buzzer, etc.) for notifying the operator of overdischarge when an overdischarge is detected may be provided, and after the notification unit notifies the operator of the overdischarge state for a predetermined time, the microcomputer 29 You may comprise so that FET may be cut off automatically. With such a configuration, the operator can know that the battery pack 4 is in an overdischarged state.

In the second embodiment, the first PWM signal having the same duty is output to the FET 232 with the trigger switch 31 being operated and not being operated, but the trigger 31 is not being operated. The duty of the state may be smaller than the duty of the operated state. In this case, the microcomputer 29 sets the target value of the boosted voltage to the first target value when the trigger switch 31 is not operated, and is larger than the first target value when the trigger switch 31 is operated. Set to the target value of 2. As a result, it is possible to further reduce the waste of electric power when the trigger switch 31 is not operated. That is, in a state where the trigger switch 31 is not operated, it is sufficient that a voltage that can detect whether the trigger switch 31 is operated or not is applied to the trigger detection unit 11 and power that is not necessary is not consumed. .

In the above embodiment, the DC power supplied from one battery pack 4 connected to the inverter 2 is converted into AC power by the inverter 2 and supplied to the AC motor 32 of the lawn mower body 3. A plurality of packs can be connected, and when one battery pack is used, the next battery pack is used as a power source, so that the usage time of the lawn mower 1 can be extended.

In the flowchart of FIG. 3, the boosted voltage is controlled in S202 to S205, but these may be performed at any position in the flowchart as long as the trigger is detected in S201. Moreover, although overdischarge was detected in S207-S209, these may be performed in any position in the flowchart, and may be performed in parallel.

In the above embodiment, an AC motor is used as the motor. However, a DC motor may be used. Even in this case, the voltage may be changed at a stage before being supplied to the DC motor. .

2 Inverter
3 Lawn mower body
4 Battery pack
10 Power switch detection diode
11 Trigger detector
26 Switching circuit
27 Current detection resistor
29 Microcomputer
31 Trigger switch
32 motor

Claims (21)

A motor,
A voltage converter that converts the input voltage and supplies the converted voltage to the motor;
An operation detection unit for detecting a start operation of the motor in a state where the operation of the voltage conversion unit is stopped;
An electric tool comprising: A switch for instructing power supply to the motor;
A control unit for controlling the voltage conversion unit,
The operation detection unit is configured in a separate system from the voltage conversion unit,
The power tool according to claim 1, wherein the control unit activates the voltage conversion unit after the switch is operated. A power switch for activating the control unit;
The power tool according to claim 1, wherein the operation detection unit applies the input voltage to the motor when the power switch and the switch are turned on. A power supply device connected to an electric device having a motor,
A voltage converter that converts the input voltage and supplies the converted voltage to the motor;
A power supply apparatus comprising: an operation detection unit configured to detect a start operation of the motor in a state where the operation of the voltage conversion unit is stopped. A switch for instructing power supply to the motor;
A control unit for controlling the voltage conversion unit,
The operation detection unit is configured in a separate system from the voltage conversion unit,
The power supply apparatus according to claim 4, wherein the control unit activates the voltage conversion unit after the switch is operated. A power switch for activating the control unit;
The power supply device according to claim 4 or 5, wherein the operation detection unit applies the input voltage to the motor when the power switch and the switch are turned on. A motor,
An inverter that converts DC power from the battery pack into AC power;
A trigger switch for instructing the motor to supply the AC power;
A control unit for controlling the inverter to perform the conversion operation after the instruction is given by the trigger switch;
An electric tool comprising: A first switching element for converting DC power from the battery pack into AC power;
A step-up circuit for stepping up the AC power converted by the first switching element;
A rectifying / smoothing circuit that rectifies and smoothes the boosted AC power and outputs it as DC power;
A transmission unit that directly transmits DC power from the battery pack to the motor when the trigger switch is instructed;
Further comprising
The control unit determines that the instruction is made by the trigger switch when DC power from the battery pack is transmitted to the motor via the transmission unit;
The controller controls the first switching element and the inverter to perform a conversion operation by the first switching element and a conversion operation by the inverter after the instruction is made by the trigger switch. The power tool according to claim 7. A first switching element for converting DC power from the battery pack into AC power;
A step-up circuit for stepping up the AC power converted by the first switching element;
A rectifying / smoothing circuit that rectifies and smoothes the boosted AC power and outputs it as DC power;
Further comprising
The inverter includes a plurality of second switching elements connected to the motor,
The control unit turns on one of the plurality of second switching elements until the instruction is given by the trigger switch, and the rectifying / smoothing circuit is connected to the motor from the one second switching element. When the direct-current power from is output, it is determined that the instruction is made by the trigger switch,
8. The electric tool according to claim 7, wherein the control unit controls the inverter to perform a conversion operation by the inverter after the instruction is given by the trigger switch. The power tool according to claim 7, wherein the control unit stops the supply of power from the battery pack to the inverter when an overdischarge detection signal is input from the battery pack. A motor,
An inverter that converts DC power from the battery pack into AC power;
A trigger switch for instructing the motor to supply the AC power;
A trigger detection unit for detecting the operation of the trigger switch;
A control unit that controls a power conversion operation of the inverter when the trigger detection unit detects an ON operation of the trigger switch;
An electric tool comprising: A booster circuit unit that converts DC power from the battery pack into AC power and boosts the power;
A rectifying / smoothing circuit unit that rectifies and smoothes the AC power boosted by the boosting circuit unit;
An inverter circuit unit for converting a direct current output from the rectifying and smoothing circuit unit into an alternating current;
With
12. The power tool according to claim 11, wherein the control unit starts the boosting operation of the boosting circuit unit when the trigger detection unit detects an ON operation of the trigger switch. The booster circuit unit includes a first switching element connected in series with the battery pack, and a booster circuit that boosts AC power converted by the first switching element,
13. The electric tool according to claim 12, wherein the control unit starts control of the first switching element when the trigger detection unit detects an ON operation of the trigger switch. The inverter circuit includes a plurality of second switching elements,
The electric power tool according to claim 12 or 13, wherein the control unit starts control of the second switching element when the trigger detection unit detects an ON operation of the trigger switch. When the battery pack and the motor are connected and the trigger switch is turned on, the battery pack includes a bypass circuit unit that transmits DC power from the battery pack to the motor.
15. The trigger detection unit detects an ON operation of the trigger switch when a voltage of the battery pack is applied through the bypass circuit unit and the motor. The electric tool according to Crab. The inverter includes a main switch connected to the battery pack for starting the control unit,
The power tool according to claim 15, wherein the bypass circuit unit is connected to a side of the main switch opposite to the battery pack. The electric power tool according to claim 15 or 16, wherein the trigger detection unit includes a plurality of resistors connected in series with the motor. A booster circuit unit that converts DC power from the battery pack into AC power and boosts the power;
A rectifying / smoothing circuit unit that rectifies and smoothes the AC power boosted by the boosting circuit unit;
An inverter circuit unit that has a plurality of switching elements and converts direct current from the battery pack into alternating current,
12. The electric tool according to claim 11, wherein the control unit maintains one of the plurality of switching elements in an on state before the trigger switch is turned on. A closed circuit is formed by the switching element, the motor and the trigger detection unit maintained in the ON state,
19. The electric tool according to claim 18, wherein the control unit increases the output from the boosting circuit unit when the trigger detection unit detects an ON operation of the trigger switch. The plurality of switching elements include at least two switch groups in which two switching elements are connected in series,
Each of the two switch groups includes a first switching element electrically connected to the positive side of the battery pack and a second switching element electrically connected to the negative side of the battery pack,
The switching element that maintains the ON state is the first switching element of one of two switch groups,
The electric tool according to claim 18 or 19, wherein the trigger operation detection unit is connected in parallel to the second switching element of the other of the two switch groups. 21. The electric tool according to claim 11, wherein the control unit stops the power conversion operation of the inverter when an overdischarge detection signal is input from the battery pack.