JP2005059177A - Impact rotating tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an impact rotating tool capable of driving and controlling a motor while avoiding cost increase and enlargement. <P>SOLUTION: By using variation of rotation speed peculiar to the impact rotating tool 1, a brushless motor 4 is driven at a maximum efficiency. In other words, based on a rotor position detection signal outputted from a rotor position detecting section 24, the rotation speed of the brushless motor 4 is calculated. An amplitude value and the center value of the amplitude of the variation of the rotating speed are calculated, and a load torque corresponding to the amplitude value and the center value of the amplitude is derived with a load torque table set from the amplitude value and the center value of the amplitude based on a measurement result measured in advance. A current phase corresponding to the load torque and the rotating speed is derived as a current phase β providing the maximum efficiency. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an impact rotary tool used for tightening a bolt, a nut, or a screw.

  A brushless motor, a drive shaft to which the rotational force of the motor is decelerated and transmitted, a hammer coupled to the drive shaft via a cam mechanism, an output shaft disposed coaxially with the drive shaft, and an output shaft And an anvil that is arranged to overlap with a predetermined portion of the hammer in the axial direction, and a spring that biases the hammer toward the output shaft, and the rotational force is applied to the hammer via the drive shaft and the cam mechanism. When transmitted, an impact rotary tool configured to transmit intermittent rotational impact force to the output shaft through the anvil by repeatedly performing an impact engagement between the hammer and the anvil is performed. Known (for example, Patent Document 1 below).

This type of impact rotary tool may be configured to feedback control the motor current using a current sensor in order to operate the motor with maximum efficiency.
JP 2000-317854 A

  However, as described above, in the configuration in which the motor is controlled using the current sensor, since the current sensor is relatively expensive, the cost of the impact rotary tool is increased. A space for installing the current sensor is required, and the impact rotary tool is increased in size.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an impact rotary tool capable of performing drive control of a motor while avoiding an increase in cost and an increase in size.

  In order to achieve the above-described object, an impact rotary tool according to the first means of the present invention includes a brushless motor and a hammer that is movably supported in the axial direction on a drive shaft to which rotational force is transmitted by the brushless motor. In an impact rotary tool comprising a power transmission mechanism that transmits the rotational force of the drive shaft to an output shaft that supports the anvil by intermittently hitting the anvil, and a drive unit that drives the brushless motor, The drive unit detects a rotation speed of the brushless motor, and a speed control for deriving a control value of the rotation speed based on the detected rotation speed and a target value of the rotation speed of the brushless motor. And an amplitude value of the detected rotational speed fluctuation and a center value of the amplitude, and a torque indicating a predetermined torque value from the amplitude value and the center value. Comprising a torque signal generator for outputting a click value signal, based on each output of the torque value signal generator and a rotation speed detecting unit, and a current phase setting unit that sets the current phase where the maximum efficiency is obtained.

  In the above-described impact rotary tool, the torque value signal generation unit may be in a state in which the brushless motor is idling when the amplitude value of the detected rotation speed falls below a value set as the idling amplitude value for a certain period. When the idling determination is performed, a signal indicating the idling torque value is output to the current phase setting unit in preference to the torque value signal based on the amplitude value and the center value.

  Further, in the above-described impact rotary tool, the torque value signal generation unit has a function of determining that the brushless motor is in an acceleration state when the detected rate of change in the rotational speed exceeds a predetermined threshold for a certain period. Further, when the acceleration determination is made, a signal indicating an acceleration torque value is output to the current phase setting unit in preference to the torque value signal based on the amplitude value and the center value.

  Furthermore, in the above-described impact rotary tool, the torque value signal generator generates the brushless signal when the detected amplitude value of the rotational speed exceeds a value set as a lock amplitude value and the center value of the amplitude falls below the threshold value. The motor further includes a function for determining that the motor is in a locked state. When the lock determination is made, a signal indicating a lock torque value is given priority over the torque value signal based on the amplitude value and the center value. Output to.

  Furthermore, in the above-described impact rotary tool, the current phase setting unit replaces the outputs of the torque value signal generation unit and the rotation speed detection unit with the output of the torque value signal generation unit and the rotation speed of the brushless motor. Based on the target value, the current phase at which the maximum efficiency is obtained is set.

  According to the present invention, the rotational speed of the brushless motor is detected, the amplitude value of the fluctuation of the detected rotational speed and the center value of the amplitude are calculated, and the torque indicating a predetermined torque value from the amplitude value and the center value. A value signal is generated, and the current phase for obtaining the maximum efficiency is set based on the torque value signal and the detected rotational speed, so that the maximum efficiency can be obtained using the current sensor for the current flowing through the brushless motor. Compared with the case where the current phase is set, the drive control of the brushless motor can be performed while avoiding the increase in cost and size.

  Hereinafter, an embodiment of an impact rotary tool according to the present invention will be described.

  FIG. 1 is a partially cutaway view showing the overall configuration of the impact rotary tool, and FIG. 2 is a diagram showing the main configuration and operation of the impact mechanism in the impact rotary tool.

  As shown in FIG. 1, the impact rotary tool 1 includes a power transmission unit 2, an output shaft 3, a brushless motor 4, and a motor drive device 5, and the power transmission unit 2 includes a drive shaft 6 and a planetary gear mechanism. 7, a hammer 8 and an anvil 9.

  The drive shaft 6 transmits the rotational force generated by the brushless motor 4 at a reduced speed by the planetary gear mechanism 7.

  The hammer 8 is a member having a substantially cylindrical shape provided with a striking portion 10 protruding from the surface on the output shaft 3 side, and is rotatably fitted on the drive shaft 6 via a cam mechanism 11. The cam mechanism 11 is engaged with a cam groove 12 having a V-shaped cross section formed at a suitable position on the outer peripheral surface of the drive shaft 6, a cam groove 13 formed on the inner peripheral surface of the hammer 8, and both cam grooves 12, 13. The hammer 8 is controlled by the cam mechanism 11 to move in the axial direction relative to the drive shaft 6 and in the direction around the axis. As shown in FIGS. 1 and 2, the hammer 8 is biased toward the output shaft by a spring 15.

  As shown in FIG. 2, the anvil 9 has a ring-shaped base portion 16 connected to the output shaft 3 and a hit portion 17 that protrudes from the base portion 16 toward the outer peripheral side. In the axial direction, the hit portion 17 is disposed at a position overlapping the hit portion of the hammer 8. Thereby, when the hammer 8 rotates, the hitting portion 10 of the hammer 8 hits the hit portion 17 of the anvil 9.

  In the impact rotary tool 1 having the above configuration, when the load (torque) of the output shaft 11 to which bolts, nuts and the like are mounted is small, the drive shaft is connected via the cam mechanism 11 as shown in FIG. 6 is transmitted to the output shaft 3 through engagement between the striking portion 10 of the hammer 8 to which the rotational force 6 is transmitted and the striking portion 17 of the anvil 9.

  When the load applied to the output shaft 3 increases, the hammer 8 rotates relative to the drive shaft 6 as shown in FIG. It moves (retreats) toward the brushless motor 4 against the urging force, and the engagement between the hitting portion 10 of the hammer 8 and the hit portion 17 of the anvil 9 is released. When the striking part 10 gets over the striking part 17, the hammer 8 is moved to the output shaft 3 side by the guidance of the cam mechanism 11 by the biasing force of the spring 15.

  Thereafter, as shown in FIG. 2 (d), the hammering portion 10 of the hammer 8 is engaged with the hitting portion 17 of the anvil 9 again by the rotation of the hammer 8, and the hitting portion 17 is impacted in the rotational direction. give. The above operation is repeated.

  FIG. 3 is a diagram illustrating an example of the internal structure of the brushless motor 4.

  As shown in FIG. 3, the brushless motor 4 is formed with a rotor 18 having a plurality of permanent magnets 20 embedded therein so that magnetic poles are alternately arranged in the circumferential direction, and at regular intervals in the circumferential direction. And a stator 19 in which excitation windings (stator coils) are respectively wound around the plurality of salient poles. The configuration of the rotor 18 and the stator 19 such as the arrangement of the permanent magnets 20 and the number of salient poles provided in the stator 19 are not limited to those described above.

  Further, on the circumferential surface of the rotating shaft (not shown) of the rotor 18, a plurality of permanent magnets alternate the magnetic poles in the circumferential direction at positions corresponding to the positions where the permanent magnets 20 are arranged in the circumferential direction. On the other hand, the stator 19 is provided with Hall elements 21 to 23 for detecting the position of the rotor 18 so as to correspond to the permanent magnet of the rotating shaft. The functions of the Hall elements 21 to 23 will be described later.

  In the brushless motor 4 having such a configuration, a magnetic force acting between the magnetic pole of the excitation winding and the magnetic pole of the rotor 18 generated by electromagnetic induction caused by energization of the excitation winding is used, as will be described later. The switching operations of a plurality of switching elements (not shown) connected to the respective excitation windings L1 to L6 are performed based on position detection signals from the Hall elements 21 to 23, for example, the excitation windings L1, L2, L3, The rotor 18 is rotated by controlling in the order of L4, L5, and L6. Terminals T1 to T6 are terminals connected to the switching element.

  FIG. 4 is a block diagram showing the configuration of the motor drive device 5.

  As shown in FIG. 4, the motor drive device 5 includes a rotor position detection unit 24, an inverter unit 25, a power supply unit 26, and a control unit 27.

  The rotor position detection unit 24 includes the Hall elements 21 to 23 described above, and a pulse signal indicating the position of the rotor of the brushless motor 4 (hereinafter referred to as rotor position detection) using the characteristics of the Hall elements 21 to 23. Signal). That is, when a current is supplied from a predetermined terminal to the Hall elements 21 to 23 and a magnetic field is applied to the Hall elements 21 to 23, an electromotive force (proportional to the magnetic flux density in a direction perpendicular to the supplied current and the magnetic field ( Therefore, the Hall voltage output from the Hall elements 21 to 23 is converted into two kinds of digital signals (for example, 5V and 0V digital signals) and based on these signals. Then, it is detected whether the magnetic pole of the rotor 18 facing the Hall elements 21 to 23 is an N pole or an S pole.

  Although not shown, the inverter unit 25 is configured by a three-phase inverter in which, for example, six switching elements are connected in a three-phase bridge, and a command from the control unit 27 (voltage control unit 33) is described later. Thus, the switching operation of each switching element is controlled by PWM (Pulse Width Modification) to convert the DC voltage supplied from the power supply unit 26 into an AC voltage, and this voltage is applied to the excitation winding of the brushless motor. is there.

  The control unit 27 includes a microcomputer having a built-in storage unit including a ROM for storing a control program and a RAM for temporarily storing data, for example, and controls the operation of the inverter unit 25.

  By the way, when the hammer 8 strikes the anvil 10, the load (torque) applied to the brushless motor 4 is increased, and the rotational speed of the brushless motor 4 is minimized. Further, when the hammering portion 10 of the hammer 8 gets over the hitting portion 17 of the anvil 9, the load applied to the brushless motor 4 is abruptly reduced, and then the rotational speed of the brushless motor 4 until immediately before the hammer 8 strikes the anvil 9. Rises. Therefore, the rotation speed (detection speed) of the brushless motor has a waveform that changes in a wave shape with a period until the hammer hitting portion hits the hit portion of the anvil (see FIGS. 7 and 9).

  In the present embodiment, the brushless motor 4 is driven at the maximum efficiency without detecting the current flowing through the excitation windings L1 to L6 by utilizing the fluctuation of the rotational speed peculiar to the impact rotary tool 1 as described above. I have to.

  In order to realize this function, the control unit 27 functionally includes a speed calculation unit 28, a speed command unit 29, a speed control unit 30, a load torque deriving unit 31, a current phase setting unit 32, and a voltage control. Part 33.

  The speed calculation unit 28 calculates the rotation speed of the brushless motor 4 using a known calculation method based on the position detection signal output from the Hall element.

  The speed command unit 29 outputs information on a preset target value of speed (hereinafter referred to as a target speed) to the speed control unit 30.

  The speed control unit 30 includes a compensator into which a proportional element, a differential element, and an integral element are inserted, and calculates a speed output from the speed calculation unit 28 by using a well-known PID (Proportion Integral Differential) control method. The control value for matching with the target speed output from 29 is calculated, and this control value is output to the voltage control unit 33.

  The load torque deriving unit 31 derives a load applied to the brushless motor 4 (hereinafter referred to as load torque). That is, the load torque deriving unit 31 detects the maximum value and the minimum value of the rotation speed of the brushless motor 4 and calculates the difference between the average value of the maximum value and the minimum value (hereinafter referred to as an amplitude value) in a certain period. Then, an intermediate value between the maximum value and the minimum value (hereinafter, the center value of the amplitude) is calculated. The load torque deriving unit 31 stores the load torque using the amplitude value and the center value of the amplitude as parameters based on the measurement result measured in advance, and the amplitude value calculated with reference to this table. And a load torque corresponding to the center value of the amplitude is derived.

  The current phase setting unit 32 sets the current phase β at which the maximum efficiency is obtained based on the output from the load torque deriving unit 31 and the output from the speed calculation unit 28. The current phase β is a phase difference in the switching timing of energization with respect to the position of the rotor 18.

  FIG. 5 is a graph showing the characteristics of load torque and rotational speed, where the horizontal axis represents id current and the vertical axis represents iq current.

  As shown in FIG. 5, when the load torque applied to the brushless motor 4 is constant, the id current and the iq current are in a substantially inversely proportional relationship, and when the id current is constant, the load torque is equal to the iq current. It has the characteristic that it increases as it increases. Further, when the rotation speed of the brushless motor 4 is constant, the id current and the iq current are in a substantially proportional relationship, and when the id current is constant, the rotation speed increases as the iq current increases. Have The current phase setting unit 32 stores this characteristic in a table format, and uses this characteristic to derive a current phase at which maximum efficiency can be obtained.

  That is, as shown in FIG. 5, for example, assuming that the rotation speed detected by the speed calculation unit 28 is 5000 rpm and the load torque derived by the load torque deriving unit 31 is 3 Nm, the current phase setting unit 32 The intersection point P between the curve R and the curve T is obtained, and the angle between the vector having the origin (0, 0) as the start point and the intersection point P as the end point and the Y axis is set as the current phase β at which the maximum efficiency is obtained.

  The voltage control unit 33 controls the operation of the inverter unit 25, that is, the power supplied to the brushless motor 4. The voltage control unit 33 is based on the control value output from the speed control unit 30 and the current phase β output from the current phase setting unit 32, and the duty of the AC voltage output from the inverter unit 25 (ON time / ( A signal indicating ON time + OFF time)) and a signal indicating energization switching timing to the brushless motor 4 are output to the inverter unit 25. Thereby, the voltage of the voltage value corresponding to the aforementioned duty is supplied from the inverter unit 25 to the excitation windings L1 to L6 instructed by the voltage control unit 33.

  As described above, the rotation speed of the brushless motor 4 is calculated based on the rotor position detection signal output from the rotor position detection unit 24, and the amplitude value and the center value of the amplitude of the fluctuation of the rotation speed are calculated. A load torque corresponding to the calculated amplitude value and the center value of the amplitude is derived from the load torque table set from the amplitude value and the center value of the amplitude based on the measurement result measured in advance. Since the current phase corresponding to the speed is derived as the current phase β for obtaining the maximum efficiency, the cost of the impact rotary tool 1 is suppressed compared to the case where the current value of the motor current is detected by the current sensor. However, the brushless motor 4 can be driven with maximum efficiency.

  Next, a second embodiment of the present invention will be described.

  In the present embodiment, as shown in FIG. 6, in the block configuration of the motor drive device, in addition to the load torque deriving unit 31, an idling detection unit 34, an acceleration detection unit 35, and a lock detection unit 36 described below are provided. Since the configuration is substantially the same as that of the first embodiment except for the points described below, the same members and the like as those of the first embodiment are denoted by the same reference numerals, and the first embodiment is described below. Only differences from the form will be described. The load torque deriving unit 31, the idling detection unit 34, the acceleration detection unit 35, and the lock detection unit 36 are realized by one microcomputer.

  The idling detection unit 34 detects the maximum value and the minimum value of the rotation speed (detection speed) of the brushless motor 4 and calculates the difference between the maximum value and the average value (hereinafter referred to as an amplitude value) in a certain period. At the same time, as shown in FIG. 7, when detecting a state in which the rotation speed of the motor (detection speed of the speed detection unit) changes at a predetermined amplitude value (for example, 100 rpm) for a predetermined time or longer (for example, 1 second or longer), It is determined that the brushless motor is idling, and a signal indicating the first torque value is output to the current phase setting unit 32.

  The first torque value is a torque value at which the current phase β at which the maximum efficiency is obtained in the idling state is set by the current phase setting unit 32. The idle state of the brushless motor 4 is that the hammer 8 and the anvil 9 are engaged, but the anvil 9 and the output shaft 3 rotate integrally, so that the brushless motor 4 is hardly loaded, and the brushless motor 4 A state in which the fluctuation of the rotation speed of the motor 4 is small.

  FIG. 8 is a diagram illustrating a change in the rotation speed (detection speed) of the brushless motor 4.

As shown in FIG. 8, the acceleration detector 35 calculates a difference ΔV1 between the rotational speeds V1 and V2 of the brushless motor 4 measured at regular time intervals (time T1, T2), and the difference ΔV1 is a predetermined threshold ΔV. _{When the} time _H or more exceeds the predetermined time, it is determined that the brushless motor 4 is in an accelerated state, and a signal indicating a preset second torque value is output to the current phase setting unit 32. The second torque value is a torque value at which the current phase β at which the maximum efficiency is obtained in the acceleration state is set by the current phase setting unit 32.

  FIG. 9 is a diagram illustrating the rotation speed of the brushless motor 4 when the rotation target (screw or the like) is firmly struck and the anvil 9 is locked. The locked state is a state in which the load applied to the brushless motor 4 becomes relatively large when the hammer 8 and the anvil 9 are engaged and the hammer 8 tries to rotate the anvil 9 (for example, a screw is tightened to some extent). State). Therefore, in the locked state, when the hammer 8 and the anvil 9 are engaged, after the rotational speed of the brushless motor 4 is greatly reduced, when the engaging portion 10 of the hammer 8 gets over the engaged portion 17 of the anvil 9, As the rotation speed increases again, the fluctuation in the rotation speed of the brushless motor 4 increases compared to the acceleration state and the idling state.

  The lock detection unit 36 detects the maximum value and the minimum value of the rotation speed of the brushless motor 4, calculates the difference between the maximum value and the average value of the minimum value (hereinafter referred to as an amplitude value) in a certain period, and calculates the maximum value. An intermediate value between the value and the minimum value (hereinafter referred to as a center value of amplitude) is calculated. Then, when the amplitude value is 2000 rpm or more and the center value of the amplitude is 4000 rpm or less, for example, the lock detection unit 36 determines that the lock state has been established, and outputs a signal indicating the third torque value as a current. Output to the phase setting unit 32.

  The third torque value is a torque value at which the current phase β at which the maximum efficiency is obtained in the locked state is set by the current phase setting unit 32.

  The first to third torque values are set such that the first torque value <the second torque value ≦ the third torque value, and in the acceleration state and the idling state, the acceleration detection unit 35 Is configured to output the second torque value to the current phase setting unit 32. Note that the idle state and the locked state do not occur simultaneously.

  When the current phase setting unit 32 receives signals indicating the first to third torque values from the idling detection unit 34, the acceleration detection unit 35, and the lock detection unit 36, the current phase setting unit 32 has priority over the output of the load torque deriving unit 31. A current phase β is set at which the maximum efficiency corresponding to these torque values is obtained. That is, when the signal indicating the first torque value is input from the idling detection unit 34 based on the current phase derivation method shown in FIG. 5, the current phase setting unit 32 derives the current phase corresponding to the torque value. When a signal indicating the second torque value is input from the acceleration detection unit 35, a current phase corresponding to the torque value is derived, and when a signal indicating the third torque value is input from the lock detection unit 36, A current phase corresponding to the torque value is derived.

  With the above configuration, the brushless motor 4 can be driven with maximum efficiency in the idle state, the accelerated state, and the locked state while suppressing an increase in the cost of the impact rotary tool.

  Next, a third embodiment of the present invention will be described.

  In the first embodiment, the current phase setting unit 32 sets the current phase at which maximum efficiency is obtained based on the output of the speed calculation unit 28 and the output of the load torque deriving unit 31. In the embodiment, as shown in FIG. 10, when setting the current phase for obtaining the maximum efficiency, the output of the speed command unit 29 (target value of the rotation speed) is used instead of the output of the speed calculation unit 28. Except for this point, the configuration is substantially the same as that of the first embodiment. In FIG. 10, the same members and the like as those in the first embodiment are given the same numbers.

  As described above, by using the output of the speed command unit 29 (the target value of the rotation speed) instead of the output of the speed calculation unit 28, the maximum efficiency can be achieved without being affected by the fluctuation of the rotation speed of the brushless motor 4. The obtained current phase setting process can be performed stably.

  In addition, this invention can employ | adopt not only the said embodiment but the following modification (1)-(3).

  (1) In the second embodiment, in addition to the load torque deriving unit 31, the idling detection unit 34, the acceleration detection unit 35, and the lock detection unit 36 are all provided. Any one or two of them may be provided.

  (2) In the third embodiment, instead of the output of the speed calculation unit 28, the output of the speed command unit 29 (target value of the rotation speed) is used. The unit 32 uses the output of the speed calculation unit 28 and the output of the load torque deriving unit 31 to set the current phase, and the current phase using the output of the speed command unit 29 and the output of the load torque deriving unit 31. These modes may be switched.

  (3) In the third embodiment, the idling detection unit 34, the acceleration detection unit 35, and the lock detection unit 36 are appropriately provided as necessary, and the current phase setting unit 32 includes the idling detection unit 34, the acceleration detection unit. 35, the current phase β that provides the maximum efficiency may be derived from the output from the lock detection unit 36 and the output from the speed command unit 29.

  (4) In the first to third embodiments, the rotation speed of the motor 4 is detected using the detection signals of the Hall elements 21 to 23. However, the present invention is not limited to this. For example, the brushless motor 4 Detection based on the waveform of the back electromotive force, detection by detecting the magnitude of the back electromotive voltage of the motor separately attached, or the current and voltage waveforms of the excitation windings L1 to L6. The rotational speed may be estimated.

It is a partially broken view which shows the whole structure of an impact rotary tool. It is a figure which shows the principal part structure and operation | movement of an impact mechanism in an impact rotary tool. It is a figure which shows an example of the internal structure of a brushless motor. It is a block diagram which shows the structure of the motor drive device which concerns on 1st Embodiment. It is the figure which showed the characteristic of load torque and rotational speed. It is a block diagram which shows the structure of the motor drive device which concerns on 2nd Embodiment. It is a figure for demonstrating operation | movement of an idling detection part. It is a figure which shows the change of the rotational speed (detection speed) of a brushless motor. It is a figure which shows the rotational speed of the brushless motor 4 when it will be in the locked state where the rotation object (screw etc.) was struck firmly and the anvil was fixed. It is a block diagram which shows the structure of the motor drive device which concerns on 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Impact rotary tool 4 Brushless motor 5 Motor drive device 6 Drive shaft 8 Hammer 9 Anvil 10 Striking part 17 Striking part 24 Rotor position detection part 25 Inverter part 27 Control part 28 Speed calculation part 30 Speed control part 31 Load torque derivation part 32 current phase setting unit 33 voltage control unit 34 idling detection unit 35 acceleration detection unit 36 lock detection unit

Claims (5)

A brushless motor and a hammer supported to be movable in the axial direction on the drive shaft to which the rotational force is transmitted by the brushless motor intermittently strikes the anvil, so that the output shaft of the drive shaft is connected to the output shaft that supports the anvil. In an impact rotary tool comprising a power transmission mechanism for transmitting rotational force and a drive unit for driving the brushless motor,
The drive unit is
A rotational speed detector for detecting the rotational speed of the brushless motor;
A speed control unit for deriving a control value of the rotational speed based on the detected rotational speed and a target value of the rotational speed of the brushless motor;
A torque value signal generator that calculates an amplitude value of the detected rotation speed fluctuation and a center value of the amplitude, and outputs a torque value signal indicating a predetermined torque value from the amplitude value and the center value;
An impact rotary tool comprising: a current phase setting unit that sets a current phase at which maximum efficiency is obtained based on outputs of the torque value signal generation unit and the rotation speed detection unit. The torque value signal generation unit further has a function of determining that the brushless motor is in an idle state when the detected amplitude value of the rotational speed falls below a value set as the idle amplitude value for a certain period of time. 2. The impact according to claim 1, wherein when the idling determination is performed, a signal indicating an idling torque value is output to the current phase setting unit in preference to the torque value signal based on the amplitude value and the center value. Rotary tool. The torque value signal generation unit further includes a function of determining that the brushless motor is in an acceleration state when a rate of change in the detected rotational speed exceeds a predetermined threshold for a certain period of time. 3. The impact rotary tool according to claim 1, wherein a signal indicating an acceleration torque value is output to the current phase setting unit in preference to a torque value signal based on the amplitude value and the center value. The torque value signal generation unit determines that the brushless motor is in a locked state when the detected amplitude value of the rotational speed exceeds a value set as a lock amplitude value and the center value of the amplitude falls below the threshold value. A function is further provided, and when the lock determination is made, a signal indicating a lock torque value is output to the current phase setting unit in preference to the torque value signal based on the amplitude value and the center value. Item 4. The impact rotary tool according to any one of Items 1 to 3. The current phase setting unit has a maximum efficiency based on the output of the torque value signal generation unit and the target value of the rotation speed of the brushless motor, instead of each output of the torque value signal generation unit and the rotation speed detection unit. The impact rotary tool according to any one of claims 1 to 4, wherein an obtained current phase is set.

Images