JP5729597B2 - Electric tool - Google Patents

Description

  The present invention relates to a power tool.

  2. Description of the Related Art Conventionally, there is known an electric tool that operates a tip tool connected to a motor by controlling the motor with an inverter circuit (see, for example, Patent Document 1).

Japanese Patent No. 4487836

  By the way, the inverter circuit is driven by a voltage within a usable range, and may fail if a voltage outside the usable range is supplied.

  Accordingly, an object of the present invention is to provide an electric tool that can prevent an inverter circuit from being broken by supplying a voltage outside the usable range.

  An electric power tool of the present invention includes a motor, an inverter circuit that generates a motor drive voltage from a DC voltage and supplies the motor drive voltage, a voltage detection unit that detects the DC voltage, and the DC voltage is out of a predetermined range. And a control unit that prohibits supply of the motor drive voltage to the motor by the inverter circuit.

  According to such a configuration, it is possible to prevent the inverter circuit from failing because the voltage outside the usable range is supplied.

  An electric tool according to another aspect of the present invention includes a motor, a rectifier circuit that rectifies an alternating voltage and outputs the rectified voltage, an inverter circuit that generates a drive voltage from the rectified voltage and supplies the drive voltage to the motor, A voltage detection unit that detects the rectified voltage; and a control unit that prohibits supply of a drive voltage to the motor by the inverter circuit when the rectified voltage is out of a predetermined range. .

  According to such a configuration, it is possible to prevent the inverter circuit from failing because the voltage outside the usable range is supplied.

  An electric tool according to another aspect of the present invention includes a motor, a rectifier circuit that rectifies an alternating voltage and outputs the rectified voltage, an inverter circuit that generates a drive voltage from the rectified voltage and supplies the drive voltage to the motor, A voltage detection unit that detects a peak value of the rectified voltage, and a control unit that prohibits supply of a drive voltage to the motor by the inverter circuit when the peak value is out of a predetermined range. It is a feature.

  According to such a configuration, it is possible to prevent the inverter circuit from failing because the voltage outside the usable range is supplied.

  An electric power tool according to another aspect of the present invention includes a power cord that can be connected to an AC power source, a brushless motor that is rotationally driven by the power cord, a tip tool that is driven by the brushless motor, and the brushless motor. A voltage supply unit that supplies a drive voltage; and a current detection unit that detects a current value flowing through the brushless motor, wherein the voltage supply unit is an electric tool that uses a pulse width modulation signal, and the current value is When the current value is larger than the first current value, a duty of the pulse width modulation signal is defined by a difference between the current value and the first current value.

  An electric power tool according to another aspect of the present invention includes a power cord that can be connected to an AC power source, a brushless motor that is rotationally driven by the power cord, a tip tool that is driven by the brushless motor, and the brushless motor. A voltage supply unit that supplies a drive voltage; and a current detection unit that detects a current value flowing through the brushless motor, wherein the voltage supply unit is a power tool using a pulse width modulation symbol, and the drive voltage value Is greater than the first voltage value, the duty of the pulse width modulation signal is reduced.

  An electric power tool according to another aspect of the present invention includes a power cord that can be connected to an AC power source, a brushless motor that is rotationally driven by the power cord, a tip tool that is driven by the brushless motor, and the brushless motor. A voltage supply unit that supplies a drive voltage; and a current detection unit that detects a current value flowing through the brushless motor, wherein the voltage supply unit is a power tool using a pulse width modulation symbol, and the drive voltage value Is greater than the first voltage value, the duty of the pulse width modulation signal is defined by the difference between the drive voltage value and the first voltage value.

  According to the electric tool of the present invention, it is possible to prevent the inverter circuit from being broken by supplying a voltage outside the usable range.

Circuit diagram of power tool according to embodiment Diagram explaining the relationship between current and voltage The figure which shows each threshold value with respect to the peak value of AC voltage Flow chart of prohibition control according to embodiment The figure which shows the relationship between the voltage and target duty by embodiment Explanatory drawing of voltage control by embodiment Circuit diagram of a power tool according to one modification Circuit diagram of a power tool according to another modification Diagram showing the relationship between conventional load and current Explanatory drawing of the voltage control by the 1st modification Flowchart of voltage control according to the first modification The figure which shows the relationship between the target duty by the 2nd modification, and the rotation speed of a motor. Explanatory drawing of the voltage control by the 2nd modification Flowchart of voltage control according to the second modification Circuit diagram of electric tool according to third modification Explanatory drawing when implementing the first modification using an AC power supply Explanatory drawing of voltage control by the 3rd modification Flowchart of voltage control according to the third modification Explanatory drawing of voltage control by another modification Flow chart of voltage control according to another modification

  A first embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a circuit diagram of a power tool 1 according to the first embodiment. As shown in FIG. 1, the electric tool 1 includes a trigger switch 3, a control circuit voltage supply circuit 4, a motor 5, a rotor position detection element 6, a control circuit 7, an inverter circuit 8, and a normal mode filter. 9, a rectifier circuit 10, and a smoothing capacitor 11. When the trigger switch 3 is operated, the AC voltage output from the commercial power supply 2 is rectified by the rectifier circuit 10. Since the capacitor 11 according to the present embodiment has a small capacity, the rectified voltage is not completely smoothed (see, for example, FIG. 2). For this reason, the voltage after the rectification includes a ripple that has not been smoothed. Further, the trigger switch 3 when operated, the control circuit voltage is an AC voltage from the commercial power source 2 is pressed later by the supply circuit 4 is supplied to the control circuit 7 as a control circuit for driving voltages.

  The motor 5 is a three-phase brushless DC motor, and includes a rotor 5A made of a permanent magnet including a plurality of sets (two sets in the present embodiment) N poles and S poles, and a star-connected three-phase stator winding. And a stator 5B composed of lines U, V, and W. The motor 5 (rotor 5A) rotates when the stator windings U, V, and W through which the current flows are sequentially switched. Switching of the stator windings U, V, and W will be described later.

  The rotor position detection element 6 is arranged at a predetermined interval (for example, every angle of 60 °) in the circumferential direction of the rotor 5A at a position facing the permanent magnet of the rotor 5A, and the rotation of the rotor (rotor 6A). A signal corresponding to the position is output.

  The control circuit 7 includes a motor current detection circuit 71, a rectified voltage detection circuit 72, a control circuit voltage detection circuit 73, a switch operation detection circuit 74, an applied voltage setting circuit 75, a rotor position detection circuit 76, a motor A rotation speed detection circuit 77, a calculation unit 78, a control signal output circuit 79, and an AC input voltage detection circuit 80 are provided.

  The AC input voltage detection circuit 80 detects the peak value of the AC voltage output from the commercial power supply 2 and outputs it to the computing unit 78. In the present embodiment, it is assumed that the AC voltage is detected in a sampling period in which a value sufficiently approximate to the actual peak value can be detected.

  The motor current detection circuit 71 detects the current supplied to the motor 5 and outputs it to the calculation unit 78. The rectified voltage detection circuit 72 detects the voltage output from the rectifier circuit 10 and the smoothing capacitor 11 and outputs the detected voltage to the calculation unit 78. The control circuit voltage detection circuit 73 detects the control circuit drive voltage supplied from the control circuit voltage supply circuit 4, and outputs it to the calculation unit 78. The switch operation detection circuit 74 detects the presence / absence of operation of the trigger switch 3 and outputs it to the calculation unit 78. The applied voltage setting circuit 75 detects the operation amount of the trigger switch 3 and outputs it to the calculation unit 78.

  The rotor position detection circuit 76 detects the rotation position of the rotor (rotor 6 </ b> A) based on the signal from the rotor position detection element 6, and outputs it to the motor rotation number detection circuit 77 and the calculation unit 78. The motor rotation speed detection circuit 77 detects the rotation speed of the rotor (rotor 6 </ b> A) based on the signal from the rotor position detection circuit 76 and outputs the rotation speed to the calculation unit 78.

  The calculation unit 78 generates switching signals H 1 to H 6 based on signals from the rotor position detection circuit 76 and the motor rotation number detection circuit 77 and outputs the switching signals H 1 to H 6 to the control signal output circuit 79. The calculation unit 78 adjusts the switching signals H <b> 4 to H <b> 6 as a pulse width modulation signal (PWM signal) based on the signal from the applied voltage setting circuit 75 and outputs it to the control signal output circuit 79. Switching signals H1-H6 are output to inverter circuit 8 via control signal output circuit 79. Note that the switching signal H1-H3 may be adjusted as a PWM signal.

  Inverter circuit 8 includes switching elements Q1-Q6. The gates of the switching elements Q1-Q6 are connected to the control signal output circuit 79, and the drains or sources of the switching elements Q1-Q6 are connected to the stator windings U, V, W of the stator 5B.

Each of the switching elements Q1-Q6, the control signal performs a switching operation based on the switching signal H1-H6 inputted from the output circuit 79, three-phase the applied Ru voltage to the inverter circuit 8 is outputted from the smoothing capacitor 11 (U-phase , V phase and W phase) Power is supplied to the stator windings U, V, W as voltages Vu, Vv, Vw.

  Specifically, switching signals H1-H6 are input to switching elements Q1-Q6, respectively, and thereby the energized stator windings U, V, W, that is, the rotation direction of rotor 5A is controlled. At that time, the amount of power supplied to the stator windings U, V, W is controlled by H4-H6 which is also a PWM signal.

  With the above configuration, the electric tool 1 can supply a drive voltage corresponding to the operation amount of the trigger switch 3 to the motor 5.

  By the way, the inverter circuit 8 is driven by a voltage within the usable range (for example, about 110 to 200 V for the rectified voltage and about 80 to 120 V for the AC input voltage). However, for example, as shown in FIG. 2, when the current flowing through the circuit is large, the voltage generated by the L component in the circuit is the rectified voltage output from the rectifier circuit 10 and the smoothing capacitor 11, that is, the inverter circuit. 8 may be superimposed on the voltage supplied to the inverter circuit 8, and if this voltage is out of the usable range of the inverter circuit 8, the inverter circuit 8 may break down.

  Therefore, in the electric power tool 1 according to the present embodiment, when a voltage outside the predetermined range is supplied to the inverter circuit 8 (calculation unit 78), supply of power to the motor 5 is prohibited and supply of power to the motor is prohibited. Control to limit. The predetermined range is included in the usable range of the inverter circuit 8 (arithmetic unit 78).

  For example, as shown in FIG. 3, when the voltage V1 detected by the AC input voltage detection circuit 80 is equal to or lower than the voltage threshold A (for example, 80V) or equal to or higher than the voltage threshold B (for example, 120V), the switching element Q4 -The supply of electric power to the motor 5 is prohibited by setting the PWM duty of the PWM signal H4-H6 output to Q6 to zero. As a result, it is possible to prevent the inverter circuit 8 from being supplied with a voltage outside the usable range, and thus it is possible to prevent the inverter circuit 8 from failing.

  In the present embodiment, the inverter circuit 8 also includes the voltage V2 detected by the rectified voltage detection circuit 72 when the voltage threshold C (eg, 110V) or less or the voltage threshold D (eg, 200V) or more. In order to prevent a voltage outside the usable range from being supplied, power supply to the motor 5 is prohibited.

  Further, in the present embodiment, in order to prevent the voltage outside the usable range from being supplied to the calculation unit 78, the voltage V3 detected by the control circuit voltage detection circuit 73 is the voltage threshold E (for example, 10V). The supply of electric power to the motor 5 is prohibited also when the voltage threshold value F (for example, 20 V) or more is used.

  Here, the prohibition control performed by the calculation unit 78 will be described in detail with reference to FIG. FIG. 4 is a flowchart of prohibition control according to the present embodiment. This flowchart starts when a power switch (not shown) of the electric power tool 1 is turned on.

  First, the calculation unit 78 determines whether or not the voltage V1 detected by the AC input voltage detection circuit 80 is equal to or lower than the voltage threshold A or higher than the voltage threshold B (S101).

  When the voltage V1 is equal to or lower than the voltage threshold A or equal to or higher than the voltage threshold B (S101: YES), the power to the motor 5 is set by setting the target duty Dt of the PWM signals H4, H5, and H6 to 0%. Is prohibited (S102). This prevents a voltage outside the usable range from being supplied to the inverter circuit 8.

  On the other hand, if the voltage V1 is larger than the voltage threshold A and smaller than the voltage threshold B (S101: NO), then the voltage V2 detected by the rectified voltage detection circuit 72 is equal to or lower than the voltage threshold C or the voltage threshold. It is determined whether or not it is greater than or equal to D (S103).

  If the voltage V2 is equal to or higher than the voltage threshold C or the voltage threshold D (S103: YES), the target duty Dt of the PWM signals H4, H5, and H6 is set to 0% to set the power to the motor 5 Supply is prohibited (S102). This more reliably prevents the inverter circuit 8 from being supplied with a voltage outside the usable range.

  On the other hand, when the voltage V2 is larger than the voltage threshold C and smaller than the voltage threshold D (S103: NO), the voltage V3 detected by the control circuit voltage detection circuit 73 is equal to or lower than the voltage threshold E or the voltage It is determined whether or not it is equal to or greater than a threshold value F (S104).

  When the voltage V3 is equal to or higher than the voltage threshold value E or the voltage threshold value F (S104: YES), the target duty Dt of the PWM signals H4, H5, and H6 is set to 0% so that the electric power to the motor 5 is Supply is prohibited (S102). This prevents a voltage outside the usable range from being supplied to the calculation unit 78.

  When the voltage V3 is larger than the voltage threshold E and smaller than the voltage threshold F (S104: NO), it is subsequently determined whether or not the trigger switch 3 is turned on (S105).

  If the trigger switch 3 is not turned on (S105: NO), the process returns to S101.

  On the other hand, when the trigger switch 3 is turned on (S105: YES), it is subsequently determined whether or not the voltage V1 is equal to or higher than the voltage threshold G (S106).

  Here, as shown in FIG. 3, if the voltage V1 is included in the prevention range equal to or higher than the voltage threshold G even if the voltage V1 is smaller than the voltage threshold B, the inverter circuit 8 is not currently broken down. When the current increases or noise occurs, there is a possibility that the current value is easily deviated from the predetermined range.

Therefore, in the present embodiment, when the voltage V1 is equal to or higher than the voltage threshold G (S106: YES), the target duty Dt is set to less than 100% (S107), and the process returns to S101. Specifically, as shown in FIG. 5, a target duty Dt represented by Dt = ( G / V1 ) × 100 is set, and the process returns to S101. Thereby, as shown in FIG. 6, when V1 becomes more than the voltage threshold G, the voltage supplied to the inverter circuit 8 and the calculating part 78 can be reduced. Note that the voltage supplied to the inverter circuit 8 and the calculation unit 78 can be reduced by performing the same control when V2 becomes equal to or higher than the voltage threshold H. As a result, it is possible to prevent the mechanical rotation of the mechanical unit and the motor unit from occurring due to an increase in the motor rotation speed due to the high voltage input. Furthermore, since the voltage increases due to the influence of the L component of the circuit when the current increases, the current can also be decreased by reducing the duty, thereby preventing an increase in the voltage after rectification.

  On the other hand, when the voltage V1 is smaller than the voltage threshold G (S106: NO), the voltage V1 is included in the normal range, so the target duty Dt is set to 100% (S108) and the process returns to S101.

  Thus, in the electric power tool 1 according to the present embodiment, a predetermined range included in the usable range of the inverter circuit 8 (calculation unit 78) is set, and a voltage outside the predetermined range is applied to the inverter circuit 8 (calculation unit 78). Since the supply of power to the motor 5 is prohibited when supplied, a voltage outside the usable range is supplied to the inverter circuit 8 (calculation unit 78) to prevent the inverter circuit 8 (calculation unit 78) from failing. It becomes possible to do.

  Further, in the electric power tool 1 according to the present embodiment, the voltage supplied to the inverter circuit 8 (calculation unit 78) is included in the predetermined range when the motor 5 is driven, but is out of the normal range. In this case, since the voltage is controlled to decrease, it is possible to prevent the inverter circuit 8 (arithmetic unit 78) from being supplied with a voltage outside the usable range.

  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, AC power from the commercial power source 2 is converted into DC power and then supplied to the inverter circuit 8. However, as shown in FIG. 7, DC power from the battery pack 20 is directly applied to the inverter circuit 8. The structure which supplies to may be sufficient. In this case, a battery voltage detection circuit 81 is provided instead of the rectified voltage detection circuit 72 of FIG. 1, and the detected voltage detected by the battery voltage detection circuit 81 or the control circuit voltage detection circuit 73 is detected. What is necessary is just to prohibit supply of the electric power to the motor 5, when a voltage has remove | deviated from the predetermined range.

  In addition, when the voltage of the battery pack 20 is low, as shown in FIG. 8, instead of the control circuit voltage supply circuit 4 and the control circuit voltage detection circuit 73 of FIG. A configuration in which the detection circuit 82 is provided and the voltage boosted by the booster circuit voltage supply circuit 40 is supplied to the arithmetic unit 78 is conceivable. In the case of such a configuration, when the voltage detected by the battery voltage detection circuit 81 or the voltage detected by the booster circuit voltage detection circuit 82 is out of a predetermined range, power is supplied to the motor 5. You can ban it.

  Moreover, in the said embodiment and modification, prohibition of the electric power supply to the motor 5 was judged for every voltage of several places, but prohibition of an electric power supply may be judged based on the voltage of any one place. .

  By the way, the motor 5 may break down when an overcurrent flows. For example, as shown in FIG. 9, the current is proportional to the load, and therefore when the motor 5 is subjected to a load exceeding a predetermined level, a current having a magnitude that damages the motor 5 flows to the motor 5. .

  Therefore, in the electric power tool 1 according to the first modification, as shown in FIG. 10, a target current value It smaller than the overcurrent threshold Ith is set, and the current value of the current detected by the motor current detection circuit 71 is the target value. Voltage control is performed to reduce the PWM duty of the PWM signals H4-H6 output to the switching elements Q4-Q6 when the current value It exceeds the current value It. As a result, the current flowing through the motor 5 is also smaller than the target current value It, so that it is possible to prevent an overcurrent from flowing through the motor 5. In addition, since the possibility of stopping the motor 5 due to overcurrent is reduced, smooth work by the electric power tool 1 is ensured. Furthermore, it is possible to protect the inverter circuit 8 that is vulnerable to overcurrent.

  Here, the voltage control performed by the calculation unit 78 will be described in detail with reference to FIG. FIG. 11 is a flowchart of voltage control according to the first modification. This flowchart starts when the trigger switch 3 is turned on.

  First, the calculation unit 78 acquires the current value I of the current flowing through the motor 5 from the motor current detection circuit 71 (S101), and determines whether or not the current value I is larger than the overcurrent threshold Ith (S102). ).

  When the current value I is larger than the overcurrent threshold Ith (S102: YES), the supply of power to the motor 5 is stopped by setting the target duty Dt of the PWM signals H4, H5, and H6 to 0% ( S103). This prevents overcurrent from flowing through the motor 5.

  On the other hand, when the current value I is equal to or less than the overcurrent threshold Ith (S102: NO), it is subsequently determined whether or not the current value I is larger than the target current value It (S104).

  When the current value I is less than or equal to the target current value It (S104: NO), after setting (increasing) the target duty Dt for increasing the current value I to the target current value It (S105), S101 Return to.

  More specifically, Dt = (It−I) × P + D (1) (P is a feedback gain, D is a current duty), a target duty Dt is set, and the duty is set toward the target duty Dt by Da. Increase by%. Thus, by increasing the duty by Da%, it is possible to prevent an excessive inrush current from flowing through the motor 5.

  On the other hand, when the current value I is larger than the target current value It (S104: YES), the target duty Dt is decreased by decreasing the target current value It (105), and the process returns to S101.

  Thus, in the electric tool 1 according to the first modification, the target duty Dt is decreased when the current value I of the current flowing through the motor 5 is larger than the target current value It. As a result, the current flowing through the motor is also smaller than the target current value It, so that it is possible to prevent an overcurrent from flowing through the motor 5. In addition, since the possibility of stopping the motor 5 due to overcurrent is reduced, smooth work by the electric power tool 1 is ensured. Furthermore, it is possible to protect the inverter circuit 8 that is vulnerable to overcurrent.

  Subsequently, a second modification will be described.

  If the same voltage is supplied when the rotation speed of the motor 5 is low and high, a larger current flows through the motor 5 when the rotation speed is low. On the other hand, the change of the target duty takes some time before being reflected in the current. Therefore, when the rotational speed of the motor 5 is low, even if the control according to the first modification is performed, the control cannot follow and an overcurrent may flow through the motor 5.

  Therefore, in the present embodiment, as shown in FIG. 12, the target duty Dt is changed according to the number of rotations of the motor 5. Specifically, the target duty Dt is set such that a large voltage is not supplied to the motor 5 by setting the target duty Dt to a small value while the rotational speed of the motor 5 is low. As a result, as shown in FIG. 13, it is possible to prevent a large current from flowing through the motor 5 while the rotational speed of the motor 5 is low, and thus it is possible to appropriately prevent an overcurrent from flowing through the motor 5. Become.

  Next, voltage control according to the present embodiment will be described with reference to FIG. FIG. 14 is a flowchart of voltage control according to the present embodiment. This flowchart starts when the trigger switch 3 is turned on. Note that the steps from S201 to S203 are the same as S101 to S103 in FIG.

  When the current value I is equal to or less than the overcurrent threshold Ith (S202: NO), the motor N is obtained from the motor speed detection circuit 77 (S204), and the target current value is based on the speed N. After setting It and the target duty Dt for increasing the current value I to the target current value It and limiting it with the target current value It (S205), the process returns to S201. In the present embodiment, as shown in FIG. 12, the target duty Dt is increased in proportion to 100% when the rotational speed is from 0 rpm to a predetermined rpm, and is fixed to 100% after the predetermined rpm.

  As described above, in the electric power tool 1 according to the present embodiment, the target duty Dt is changed according to the rotational speed of the motor 5. Thus, since a large voltage is prevented from being supplied to the motor 5 while the rotation speed of the motor 5 is low, it is possible to appropriately prevent an overcurrent from flowing through the motor 5.

  Subsequently, a third modification will be described.

  In the first modification, the DC power from the battery pack 2 is directly supplied to the inverter circuit 8, but a configuration in which AC power from a commercial power supply is rectified and smoothed into DC power and then supplied to the inverter circuit 8 is also conceivable. . As such a configuration, for example, as shown in FIG. 15, a normal mode filter 21, a rectifier circuit 22, and a smoothing capacitor 23 are provided between the commercial power supply 20 and the inverter circuit 8. One having an AC input voltage detection circuit 24 is conceivable.

  In the configuration shown in FIG. 15, the smoothing capacitor 23 may have a small capacity for reasons such as cost reduction. The reason for using a small-capacitance capacitor is that if a large-capacity smoothing capacitor is used, the power factor deteriorates and it is necessary to add a power factor improving circuit for improving the power factor as a countermeasure. In order to provide the power factor correction circuit, a large space is required, and the power tool becomes large.

  The small-capacitance capacitor here is a capacitor having a capacitance of 47 μF or less, for example. In particular, when it is 10 μF or less, pulsation of the drive voltage is likely to occur. In the embodiment of the present invention, a 0.47 μF capacitor is employed. When this small-capacitance capacitor is used, the ripple of the power supply voltage becomes large. For example, if the ripple is 70% or more, it can be said that a large pulsation occurs. The ripple is expressed as (dV / V *) × 100% when the maximum value of the voltage of the input power supply of the tool is V * and the amount of change in voltage is dV.

  When a capacitor having a small capacity is used as the smoothing capacitor 23, the AC power is not completely smoothed by the smoothing capacitor 23, and power having a pulsating waveform of the first frequency is supplied to the inverter circuit 8. Then, when the control according to the first embodiment is performed in such a configuration, as shown in FIG. 16, the current value I becomes equal to the time when the control follows after the current value I becomes larger than the target current value It. The duty is increased again when it starts to decrease and decreases below the target current value It.

  However, in this case, the current value I has decreased to the target current value It or lower because the AC voltage has decreased, not because the load has decreased. Therefore, a current exceeding the target current value It flows to the motor 5 every AC cycle, and the motor 5 generates unnecessary heat generation.

  Therefore, in the present embodiment, the duty is reduced when the peak value Ip of the pulsating current is larger than the target current value It. Specifically, as shown in FIG. 17, when the peak value Ip of the pulsating current is larger than the target current value It, the duty is decreased, and the decreased duty is maintained until the next peak value Ip is detected. When the peak value Ip becomes equal to or less than the target current value It, the duty is recovered stepwise. As a result, a current exceeding the target current value It does not flow to the motor 5 for each AC cycle, so that it is possible to prevent the motor 5 from generating unnecessary heat.

  Here, the voltage control according to the present embodiment will be described in detail with reference to FIG. FIG. 18 is a flowchart of voltage control according to the present embodiment. This flowchart starts when the trigger switch 3 is turned on. The steps from S301 to S303 are the same as S101 to S103 in FIG.

  On the other hand, if the current value I (t) is equal to or less than the overcurrent threshold Ith (S302: NO), then the current value I (t) is smaller than the stored current value I (t-1). It is determined whether or not (S304).

  If the current value I (t) is greater than or equal to the current value I (t−1) (S302: NO), the current value I (t) is stored as the current value I (t−1) ( S305), the process returns to S301.

  On the other hand, when the current value I (t) is smaller than the current value I (t−1) (S302: YES), the current value I (t−1) is determined as the peak value Ip (S306). In the present embodiment, it is assumed that the current value I (t) is detected in a sampling period in which a value sufficiently close to the actual peak value can be detected.

  Subsequently, it is determined whether or not the peak value Ip is larger than the target current value It (S307).

  When the peak value Ip is less than or equal to the target current value It (S307: NO), after setting the target duty Dt for increasing the peak value Ip to the target current value It and limiting it with the target current value It. (S308), the process returns to S301.

  On the other hand, when the peak value Ip is larger than the target current value It (S307: YES), the target duty Dt is decreased to decrease the target current value It (309), and the process returns to S301.

  As described above, in the electric power tool 1 according to the present modification, the duty is reduced when the peak value Ip of the pulsating current is larger than the target current value It. Therefore, the current exceeding the target current value It is increased by the motor 5 every cycle of AC. Therefore, it is possible to prevent the motor 5 from generating unnecessary heat and the like.

  Note that the first modification and the second modification may be performed simultaneously. More specifically, the target duty Dt is changed according to the number of revolutions of the motor 5, and when the current value I is larger than the target current value It, the target duty Dt is decreased to reduce the current flowing through the motor 5. Also good.

  In this case, as shown in FIG. 19, a target duty Dt is set so that a large voltage is not supplied to the motor 5 while the rotation speed of the motor 5 is low, and the duty is set after the rotation speed of the motor 5 exceeds a predetermined value. Is fixed to 100%. After the duty is fixed at 100%, the target duty Dt is decreased when the current value I becomes larger than the target current value It.

  Here, the voltage control according to the modification will be described in detail with reference to FIG. FIG. 20 is a flowchart of voltage control according to a modification. This flowchart starts when the trigger switch 3 is turned on.

  First, the calculation unit 78 acquires the current value I of the current flowing through the motor 5 from the motor current detection circuit 71 (S401), and determines whether or not the current value I is larger than the overcurrent threshold Ith (S402). ).

  When the current value I is larger than the overcurrent threshold Ith (S402: YES), the supply of power to the motor 5 is stopped by setting the target duty Dt of the PWM signals H4, H5, and H6 to 0% ( S403).

  On the other hand, if the current value I is equal to or less than the overcurrent threshold Ith (S402: NO), then, the rotational speed N of the motor 5 is acquired from the motor rotational speed detection circuit 77 (S404). Based on the target current value It and the target duty Dt for increasing the current value I to the target current value It are set (S405).

  Subsequently, it is determined whether or not the current value I is larger than the target current value It set in S405 (S406).

  If the current value I is less than or equal to the target current value It (S406: NO), after setting the target duty Dt for increasing the current value I to the target current value It and limiting it with the target current value It. (S407), the process returns to S401.

  On the other hand, when the current value I is larger than the target current value It (S406: YES), the target duty Dt is decreased to decrease the target current value It (408), and the process returns to S401.

  Thus, by performing the first modification and the second modification at the same time, it is possible to more effectively prevent an overcurrent from flowing through the motor 5.

  In the first modification, the voltage is decreased at a constant decrease rate when the current value I is larger than the target current value It. However, the decrease rate may be changed according to the magnitude of the current value I. .

  In the above modification, the supply of voltage to the motor 5 is stopped when the current value I is greater than the overcurrent threshold Ith. However, the current value I is greater than the target current value It over a predetermined time. The supply of voltage to the motor 5 may be stopped when the overcurrent threshold value Ith or less. In this case, the predetermined time may be changed according to the weakness against the overcurrent of the motor 5 and the inverter circuit 8.

  Further, for example, lock detection at the end of fastening when the electric power tool 1 is a driver may be performed. In this case, for example, (1) when the rotation speed N is equal to or less than a predetermined value, (2) when the rotation speed N is equal to or less than a predetermined value, and the current value I is equal to or greater than a predetermined value, (3) a current value equal to or greater than the predetermined value. If I continues for a predetermined time or more, it is conceivable to perform lock detection.

DESCRIPTION OF SYMBOLS 1 Electric tool 2 Commercial power supply 3 Trigger switch 7 Control circuit 8 Inverter circuit 10 Rectifier circuit 11 Smoothing capacitor 20 Battery pack 72 Rectified voltage detection circuit 78 Calculation part 80 Input voltage detection circuit 81 Battery voltage detection circuit

Claims (5)

A motor,
A rectifier circuit that rectifies an alternating voltage and outputs the rectified voltage;
A capacitor connected to the output side of the rectifier circuit, the rectified voltage is not completely smoothed and is a pulsating voltage;
An inverter circuit connected to the output side of the capacitor, generating a driving voltage from the pulsating voltage and supplying the driving voltage to the motor;
A voltage detector for detecting the pulsating voltage ;
A control unit for prohibiting or limiting the supply of the drive voltage to the motor by the inverter circuit so as to prevent the peak value of the pulsating voltage from becoming too large due to an increase in the current flowing through the inverter circuit. When,
An electric tool comprising: The inverter circuit is configured to generate the drive voltage using a pulse width modulation signal;
2. The electric tool according to claim 1, wherein a duty of the pulse width modulation signal is reduced when a peak value of each cycle of the pulsating voltage is larger than a first voltage value. The power tool according to claim 2, wherein the duty of the pulse width modulation signal is increased when the peak value is smaller than the first voltage value. A motor,
A rectifier circuit that rectifies an alternating voltage and outputs the rectified voltage;
An inverter circuit that generates a drive voltage from the rectified voltage and supplies the drive voltage to the motor;
A voltage detector for detecting a peak value of the AC voltage;
And a control unit for the peak value is prohibited or limit the supply of the drive voltage to the motor by the inverter circuit if the out of a predetermined range,
An electric tool comprising: The inverter circuit is configured to generate the drive voltage using a pulse width modulation signal;
The power tool according to claim 4, wherein when the peak value is larger than a first voltage value within the predetermined range, the duty of the pulse width modulation signal is reduced.

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